Saltpetre. Gunpowder. Aquafortis

In examining the question, whether Theophrastus, Pliny, and in general the ancient Greeks and Romans, were acquainted with our saltpetre, or at what period it became known, I shall perhaps meet with as little success as those who have preceded me in the same research 1190. I shall therefore be satisfied if competent judges allow that I have contributed anything new that can tend to illustrate the subject.

Our saltpetre, which is commonly called nitrum, and sometimes, though more rarely, sal nitræ, is a neutral salt composed of a peculiar acid, named the acid of saltpetre or nitric acid, and that alkali called potash. The characters by which it is most readily distinguished from other salts are its cooling taste, its fusibility when exposed to a small degree of heat, and in particular its so-called deflagration; that is, the property it has when placed in the fire, or on an ignited body, or when melted in a crucible, with a combustible substance, of suddenly bursting into a very bright flame, by which it loses its acid, and nothing remains but a carbonate of potash. The principal use of it is in making gunpowder, and for the preparation of that acid known under the name of aquafortis 1191 , which is employed in various ways.

Native saltpetre is so rare, that Cronstedt was not acquainted with it. At present, however, it is known to occur in the East Indies, in the lower part of Italy, also in Portugal 1192 , Spain, America, and some other countries 1193. But almost all the saltpetre obtained in Europe is produced partly by nature and partly by art. The putrefaction of organic bodies gives rise, under certain circumstances, to nitric acid, which in general combines with calcareous earth wherever it finds it, and forms the so-called earthy saltpetre. This is decomposed by potash, and the latter uniting with the acid forms common saltpetre. Sometimes also it is found that the nitric acid, instead of being united with calcareous earth, is combined with soda, which produces the so-called cubic saltpeter 1194. Both these saline substances, but the earthy more frequently than the cubic, are often found on effloresced walls; and both are then comprehended under the common names of Mauersalz  or Mauerbeschlagsal murale.

This efflorescence on walls was observed, in all probability, at a very early period, especially as it is produced in many parts in great abundance, and as it makes itself perceptible by the decay of walls, which it seems to corrode. It is the plague or leprosy of houses mentioned in the Mosaic code of laws. As the ancients were so much inclined to expect medicinal virtue in all natural bodies, there is reason to think that they soon collected and made trial of this saline incrustation. That this indeed was actually the case, and that they gave the name of nitrum  to this saline mass, may be proved from their writings. Their nitrum, however, must have been exceedingly various in its properties. For this incrustation is not always calcareous saltpetre; it is often soda 1195 , mixed with more or less calcareous earth; and sometimes it consists of salts of sulphuric acid. In modern times, on closer examination, other salts of nitric acid have been found in the incrustation of walls, such as flaming saltpetre or nitrate of ammonia, bitter saltpetre or nitrate of magnesia; but of these no mention can be expected in the works of the ancients.

Substances so different ought not indeed to have been all named nitrum ; but before natural history began to be formed into a regular system, mankind in general fell into an error directly contrary to that committed at present. Objects essentially different were comprehended under one name, if they any how corresponded with each other even in things accidental. Whereas at present every variety, however small, obtains a distinct appellation; because many wish to have the pleasure, if not of forming new species, at any rate of giving new names. The elephant and rhinoceros were formerly called oxen; the sable and ermine were named mice, and the ostrich was distinguished by the appellation of sparrow. In the like manner, calcareous saltpetre and alkali might be called nitrum. The ancients, however, gave to their nitrum  some epithets, but they seem to have been used only to denote uncommon varieties.

Now, as the ancients were not acquainted with any accurate method of separating and distinguishing salts, it needs excite no wonder that they should ascribe to their nitrum  properties which could not possibly be united in a salt, and much less exist in our saltpetre. But as they were neither acquainted with aquafortis nor manufactured gunpowder, and as no particular use of calcareous saltpetre was known, the nitrum  most valuable to them must have been that which consisted chiefly of soda, and which consequently could be employed in washing, in painting, and in glass-making.

It is well known that in warm countries this alkali effloresces here and there from the earth, particularly in a dry soil, and even in such quantity as to be employed in commerce. Hence it may be readily comprehended why this effloresced salt, which is very often mixed with common salt, obtained the name of nitrum.

The important discovery, that a similar salt, having the like properties, and applicable to the same uses, named at present soda, may be obtained from the ashes of certain plants, was first made, in my opinion, by the ancient Egyptians or Arabians 1196. This salt also, at least by the Greeks, was named nitrum, or considered as a species of it. By the incineration of the plants this salt was rendered slightly caustic; and it then became moist in the air, and deliquesced when not preserved in very close vessels. It was therefore like those salts which are obtained, in the same manner, from the ashes of all other plants; though the latter are essentially different from the former, and in the course of time obtained the peculiar appellation of potash or pearlash. One can hardly be surprised that the ancients were not able to distinguish soda from potash, especially as they were both obtained from vegetable ashes.

But were the ancients, under the ambiguous name of nitrum, acquainted with our saltpetre? There is certainly reason to think that it became known to them by lixiviating earths impregnated with salts. There are, as already said, not only in India but also in Africa, and particularly in Egypt, earths which, without the addition of ashes or potash, give real saltpetre, like that of the rubbish-hills on the road from new to old Cairo 1197 , and like the earth in some parts of Spain. It is a knowledge only of this natural kind of saltpetre, which required no artificial composition, that can be allowed to the ancients, as it does not appear by their writings that they were sufficiently versed in chemistry to prepare the artificial kind used at present.

But even admitting that they had our saltpetre, where and by what means can we be convinced of it? Is it to be expected that any of the before-mentioned characters or properties of this salt should occur in their writings? They neither made aquafortis nor gunpowder; and they seem scarcely to have had any occasion or opportunity to discover its deflagration and the carbonization thereby effected, or, when observed, to examine and describe it. No other use of our saltpetre which could properly announce this phenomenon has yet been known. How then can it be ascertained that under the term nitrum  they sometimes meant our saltpetre?

Those inclined to believe too little rather than too much, who cannot be satisfied with mere conjectures or probabilities, but always require full proof, will acknowledge with me, that the first certain accounts of our saltpetre cannot be expected much before the invention of aquafortis and gunpowder. It deserves also to be remarked, that the real saltpetre, as soon as it became known, was named also nitrum ; but, by way of distinction, either sal nitrum, or sal nitri, or sal petræ. The first appellation, from which our ancestors made salniter, was occasioned by an unintelligible passage of Pliny, which I shall afterwards point out. The two other names signify, like sal tartarisal succini, a salt which was not nitrum  but obtained from nitrumSal-nitri, therefore, or salniter, was that salt which, according to the representation of the ancients, was separated by art from nitrum, yet was essentially different from the nitrum  or soda commonly in use. Biringoccio says expressly, that the artificial nitrum, for the sake of distinction, was named, not nitrum, but sal nitrum.

The name nitrum  is of great antiquity, and seems to have been conveyed from Egypt and Palestine to Greece, and thence to Italy and every part of Europe. For it is evidently the neter  mentioned by the prophet Jeremiah, chap. ii. ver. 22; and which occurs also in the Proverbs of Solomon, chap. xxv. ver. 20. But whether the name nitrum, as Jerome says 1198 , be derived from the Egyptian province Nitria, whence it was exported in great abundance, or the name of the province was derived from nitrum, is a question of little importance in regard to this research. Nitron is mentioned by Herodotus, where he describes the Egyptian method of embalming dead bodies 1199 ; by some of the Greeks the word was written and pronounced litron. In the same manner people say nympha  and lympha. In order to avoid confusion, I shall here call the nitrum  of the ancients nitrum, and the nitrum  of the mineralogists saltpetre.

In the course of time men became acquainted with the purer, more useful, and cheaper mineral alkali which was furnished, under the name of soda, by the Moors and inhabitants of the southern countries, who had learned the method of preparing it. The vegetable alkali also was always more and more manufactured in woody districts, as an article in great request, and sold under the name of potash, cineres clavellati. All knowledge of the impure alkali from the incrustation of walls was then lost; and as there was no further need of guarding against confusion, it was not longer thought worth while to name saltpetre sal nitri : it was called nitrum ; and the oldest signification of this word being forgotten, it was admitted without further examination, that the nitrum  of the ancients was nothing else than our saltpetre.

In the sixteenth century some learned Europeans, while travelling through the East, heard the name natrum given to the mineral alkali which was then exported as an article of commerce, and introduced in their works this transformation of the ancient word nitrum. This appellation was employed by the systematic mineralogists, who, giving themselves little trouble about the original meaning of words, and taking care only to avoid confusion, called the mineral alkali also natrum, and applied the name of nitrum  to saltpetre. As far as I know at present, it was first stated by Peter Bellon and Prosper Alpinus 1200 , that the mineral alkali was in the East called natrum. The former returned in 1549, and the latter was still in Cairo in 1580.

This word was adopted in mineralogy by Linnæus, in the year 1736, as the name of a species, in which he comprehended for the first time the alkaline incrustation found on walls. In this he is followed by Wallerius, who includes also the mineral alkali from the East. Afterwards the word natrum  was employed in the same sense by all mineralogists.

It deserves here to be remarked, that Boyle had even examined and determined the difference between the fixed and volatile alkalies; but that mineralogists and chemists, till the latest periods, believed that all fixed alkali arose, or at least was obtained, by the incineration of plants. The difference between the mineral and vegetable alkalies was first defined, in a proper manner, by the exertion of the German chemists Pott, Model and Marggraf 1201 ; especially after the last had proved, in the year 1758, that the basis of common salt was not, as had before been generally believed, an alkaline earth, but a fixed alkali, to which, because it was in many of its properties different from the fixed vegetable alkali, he gave the name of fixed mineral alkali. Soon after this substance was discovered in mineral springs; and Model and others have shown that it is not essentially different from that which in the East is called natrum.

It is singular, and yet may be accounted for, that since that time many have spoken of the nitrum  and natrum of the ancients, though they are only different pronunciations of the same word; and natrum  is never found in the works of the Greeks or the Romans, and not even in writings of the middle ages.

But if the greater part of what I have here said should be considered only as conjecture, it must nevertheless be acknowledged that it is deduced from the nature of the thing; and when impartially compared with what we read in the ancients, the latter I hope will be better understood than it hitherto has been; the impropriety of many readings will become apparent, and the truth of this conjecture be admitted.

Were I here to relate everything that we read of nitrum, in order to compare it with nature and to examine it thoroughly, I should be obliged to extend this article to a greater length than might be agreeable to the reader. I shall therefore give only the principal proofs of my assertion, premising, that doubts which might be excited by single passages not here mentioned, will, on a closer comparison, vanish without my assistance. But I maintain that those who wish to explain the old names of natural objects must relate everything said of them, and not that alone which is favourable to their opinion, and which may be often contradicted by what was purposely or accidentally concealed. The first part of such an examination is always a careful collection from the writings of the ancients of all the predicates of the natural object, the systematic name of which one is endeavouring to prove.

There is reason however to conjecture, that the ancients, in the history of their impure nitre, the manner of obtaining which the Romans at least had no opportunity themselves of seeing, for Pliny says expressly that it was not procured in Italy, fell into many errors and mistakes, which at present cannot all be explained.

Hence it happened that the ancients did not understand the art of purifying the salt which they obtained from minerals; and therefore they were obliged to use it in the same impure state in which they found it. On this account they considered each natural mixture as a peculiar kind; gave to the greater part of them, or those most useful, particular names; and of these recommended for different purposes those which, according to their purity or mixture, or according to other circumstances, were the most convenient. It is not probable that all these varieties could be again found out or defined; and it seems to be of little importance, when it is known that the names denote nothing more than the varieties of a mineral.

In this examination it is to be regretted that the book of Theophrastus, in which he expressly treated of nitrum, has not been preserved. But it may be believed, even without the testimony of Pliny, that he was one of the most accurate and acute naturalists among the ancients, and that he gave the best account of this substance 1202. It must, however, be admitted that Pliny thoroughly understood this author, and gave a correct extract from him, and that the transcriber fell into no mistake.

That the nitrum  of the ancients was an alkali more or less impure, but not saltpetre, has been long admitted by those who had the least knowledge of mineralogy, as well as by the most sagacious physicians. The grounds for this opinion, as far as I have yet learned, are as follows: more indeed might be found, but these are sufficient to afford a complete proof. Galen, a cautious writer, says that nitrum  was in general burnt, by which means its effects were strengthened 1203. Had it been saltpetre, it is impossible that the ancients should not in burning it have observed its deflagration, and this property is too remarkable not to have been mentioned. But nothing is to be found that can with any probability be supposed to allude to it.

But should it be admitted without any grounds that it was not an alkali but saltpetre which they burnt, it must certainly have been carbonized; for a burning body may easily have fallen into the crucible, and in general nitrum seems to have been burnt in an open fire, like our lime, because Pliny, speaking of the Egyptian, considers the contrary as somewhat uncommon. Physicians then, at any rate, must have observed, that a body very different both in its appearance and effects was produced from saltpetre by burning, but which could not be used for any other purpose than that salt. Of this however we do not find the least intimation.

But nitrum  was undoubtedly soda, and on that account when burnt must have become more caustic as well as stronger in most of its effects, and in this respect similar to potash, since [owing to impurities] it in the same manner became moist and deliquesced in the air. What Pliny relates of the Egyptian nitrum  becomes then intelligible. The latter, he says, was transported in pitched vessels, because it would otherwise have deliquesced; and he afterwards adds, that it was burnt before it was sent off. Had he known that the latter was the cause and the former the effect, he would have mentioned the latter first; but his whole extract, in regard to nitre, is written in general without order. The vessels, no doubt, were of clay; but whether he means in what he adds that they were not burnt but only baked in the sun, or that before they were filled they were completely dried in the sun, has been determined by no commentator. To me the latter is the more probable. Pliny also mentions another circumstance in regard to the burning of the Egyptian nitrum ; namely, that it must be done in a close vessel, otherwise it would decrepitate or fly off. This is perfectly intelligible, when it is considered that it contained a great deal of common salt, which alone possessed the property of decrepitating; and it is well known in mineralogy that native soda, and even that which in modern times has been introduced into our collections from Tripoli, and of which I have in my possession a specimen, contains common salt 1204 , and often in cubic crystals. Pliny had just reason to add, that nitrum  otherwise does not properly decrepitate. The ancients were well acquainted with the resemblance of their nitrum  to lime, and especially of that which was burnt. On this account, because the Egyptian was exported after it had been burnt, it could easily be mixed with quicklime, or, as Pliny says, be adulterated. But the proof which he gives he does not seem to have thoroughly understood. The Egyptian must at all times have been caustic (pungens ) even without lime; but that which was mixed with lime could not so speedily or completely dissolve on the tongue as that which was pure, and left behind it more earth. What he says of a test by the smell, I cannot understand in any other manner than that burnt lime, when moistened with water, diffused that disagreeable vapour observed in apartments the walls of which have been newly plastered; though when the quantity is small this is hardly perceptible.

If I understand Theophrastus 1205  properly, he seems to say, that if nitrum  be burnt as soon as it is dug up, it communicates heat to water in the same manner as lime. It may here be seen how great a resemblance the ancients found between their nitrum, alkaline earth and lime.

The similarity of wood-ashes to the nitrum  of the ancients, which they acknowledged, proves also that it was in reality an alkaline salt. We are told by Theophrastus 1206  that nitrum  was said to be produced from oak-ashes; and Pliny 1207 , who borrowed from this writer, remarks that it was certain the ashes of that wood were nitrous. He ascribes also to burnt wine-lees the nature and properties of nitrum 1208 . Nay he considers as a kind of nitrum  those saline ashes which, in many countries destitute of salt, were used for seasoning food, and which were prepared by pouring sea-water or salt brine over burning piles of wood, gradually and in small quantities, so that the fire was not extinguished, by which means the water evaporated, leaving the salt behind, but mixed indeed with charcoal, ashes, earth, and alkaline salts; consequently it must have been moist, or at any rate nauseous, if not refined by a new solution. This method of preparing or boiling salt, which perhaps is the oldest, has been mentioned by various writers; but many of them, through ignorance or neglect, have not told us that sea-water or brine was employed, as they speak in such a manner as if any kind and even fresh water had been used for that purpose.

Varro relates that he saw this process employed on the Rhine 1209. Pliny says 1210  that oak timber had before been burnt for that purpose. In another place he mentions a similar process among the Gauls and the Germans 1211 , as Tacitus does among the Hermanduri and the Catti 1212. The former also states, on the authority of Theophrastus, that the Umbri burnt salt in the like manner 1213. It is however certain that Pliny and other ancient writers often quote from Theophrastus what, at present, is not to be found in the works of that naturalist, but in those of his preceptor Aristotle 1214.

Pliny adds, that this paltry method of obtaining salt had been long given up; and this indeed was the natural consequence of increased civilization. It is however certain that it was long continued in many countries, and in some still exists.

About two centuries ago the inhabitants of the province of Zeeland, descendants perhaps of the Catti, used no other salt than what they obtained in the like manner, from mud thrown up by the sea, which they burned and moistened with sea-water, as we are told by Lemnius, who was himself a native of that country. Boxhorn says, in his annotations on the above-quoted passage of Tacitus, that he saw a painting at Zirkzee, in which the whole process was represented. It is probable that salt was boiled exactly in the same manner as at some of the Sleswic islands, described by Denkwerth 1215 , from whose account it is seen that the glebæ marinæ, of which Lemnius speaks, consisted of mud mixed with roots growing in them; and that the salt when afterwards refined was called there Frisic, in all probability because the inhabitants had learned to make it from their ancestors the Frieslanders. I remember somewhere to have read that salt was made for a long time in this manner by the so-called Wurst-Frieslanders, in the country of Wurst, belonging to the duchy of Bremen. The inhabitants also of the Austrian part of Moldavia, or Buccowina as it is called, still use a salt, which they do not boil, but burn with their superfluous wood, in the like manner from the brine of a saline spring. A member of the former Academy of Brussels 1216  took the trouble to examine the process as described by the ancients, and obtained, as might certainly have been expected, a highly alkaline kind of common salt, similar to that which Pliny, not without reason, considered as a sort of nitrum, because undoubtedly it may oftener have been an alkaline carbonate than common salt.

Boerhaave 1217 , in quoting the passages of the ancients, did not reflect that, during the incineration of the wood, salt water was poured over it. He considered the whole process as a burning of potash, and thought that the salt obtained was fit for use only because it was made according to the manner of Tachenius. That indeed gives a carbonated salt, which is almost saponaceous, and so mixed with various parts of the burnt plants that it is much milder, consequently fitter for use than common soda or pearlash can be; but that salt was not so much of the Tachenian kind as a species of common salt superabundant in alkali.

If the nitrum  was carbonated alkali, there is reason to suppose that the ancients must have occasionally mentioned in their writings that it effervesced with acids. With the mineral acids indeed they were not acquainted; but they had vinegar, and that nitrum  produced with this an effervescence had been known in the oldest times. A very clear allusion to this circumstance is found in the book of Proverbs, chap. xxv. ver. 20; where Luther however translates the word by chalk. Jerome, whose explanation I have already quoted, was in some degree acquainted with this phænomenon; and therefore to him the comparison of Solomon was intelligible 1218. But at present I can produce no proofs from Greek writers; though they might have occurred during the use of nitrum  in medicine, in consequence of which it was often put into vinegar.

We shall be further convinced what nitrum  really was, when the uses to which it was applied, as mentioned in the works of the ancients, are considered. The most common, as soap was not then known, appears to have been in washing, a purpose for which our saltpetre would not be fit; besides, it is at all times too scarce and too dear. I shall not here adduce any proofs of its being employed in this manner, as they often occur, and as several have been already given in the preceding volume 1219. Many salves and cosmetics were prepared with nitrum ; and in all probability articles of this kind, used chiefly among the women, are to be understood by the term nitron parthenicon, which occurs in Nicholas Myrepsius, in the beginning of the fourteenth century; matronicon, mentioned by the same, and by Alexander of Tralles, about the year 565; and the nitrum matronale  of Marcellus Empiricus, in the fifth century. That the use of it for washing still continues in the East, is confirmed in various books of travels.

The oldest glass, of the preparation of which any account is to be found in history, was made by means of nitrum  or mineral alkali. For though I doubt that it could have been produced on the sandy banks of the Belus, where some merchants, when cooking, supported their pots with lumps of nitrum 1220 , because sand is not so easily brought to a state of fusion; it at any rate remains certain, that this supposed fusion with our saltpetre is altogether impossible.

The use of nitrum  for painting announces, without doubt, an alkaline carbonate, and not saltpetre 1221 ; and the case is the same with the various uses in the cookery of the ancients, many of which we have still retained. It was added to bread in baking, according to Pliny 1222 , in the stead of salt, but probably to promote its rising, for which purpose it is still employed by the Egyptians, as potash was by our bakers. For this use the mineral alkali was formerly brought from the Levant to France, till it was declared by the physicians to be injurious to the health 1223.

When meat which was too fresh was to be dressed, it was put into nitrum 1224 , in order to make it tender; and, according to Forskäl and others, this is still practised in the East. Our cooks also know that smoked meat, fish and other dried provisions become more tender when placed in a ley of potash, or when a little potash is added while they are boiling.

Nitrum, however, was employed for curing articles of food which people wished to preserve. This appears to contradict what has been mentioned above; but in all probability a caustic sort was used for the former purpose; but for the latter a mild kind, mixed with a great deal of common salt. There were so many species, that some of them might have been applied to quite contrary purposes.

As I conjecture, the use of nitrum  for causing chestnuts and other husky fruits to boil soft, was also known: to produce the same effect, potash is at present thrown among boiling lentils and peas. I am inclined to think that for this reason Apicius caused chestnuts to be boiled with nitre.

It is highly probable that this effect of alkaline carbonates induced agriculturists to believe that beans, peas, lentils and other leguminous fruits, if steeped, before they were sown, in water in which nitre had been dissolved, or if the dung spread over the earth had been mixed with nitre, the future product could be more easily boiled soft 1225. However useful this addition may be in cookery, it would produce little effect on seed; and it appears to me that the old agriculturists placed little confidence in the last-mentioned use, because they were not agreed in regard to the result. Virgil and others seem to expect from it an increase of the fruit 1226 ; but others, security against beetles, which eat the fruit and leave the husks empty 1227. When cabbages were transplanted they were strewed over with nitre, and by these means were said to come sooner to maturity 1228. Radishes also were treated in the same manner, or besprinkled with nitrous water, in order to make them more tender 1229.

A common method employed by the ancient cooks to give a beautiful green colour to pickled or boiled vegetables, was to add nitrum  to them while boiling; but this effect could be produced by natrum, and not by the nitrum  of the moderns, or that neutral salt called saltpetre 1230.

Among the oldest accounts of nitrum  is that where it is mentioned as being employed for embalming dead bodies. It would be tiresome to read over and examine everything written on that subject by the learned; but this much I think is clear, that either the flesh, and in general the softer parts of the body could be corroded in the course of seventy days by the Egyptian nitrum 1231 , which, as above shown, was burnt, and in general mixed with unslaked lime, and consequently caustic 1232 ; or that the moist parts could be desiccated by carbonate alkali, in the same manner as the manufacturers of parchment purify and dry their skins by the application of chalk. That saltpetre in no case could be useful for this purpose needs hardly be mentioned.

The ancient physicians, who were unacquainted with our numerous class of salts, employed their nitrum  in many ways, and for a great variety of mixtures; but no writer, as far as I know, ever took the trouble to examine these recipes, though it has long since been declared that nitrum  must have been potash or salt of tartar.Matthioli 1233  asserted, that those physicians would act very improperly who should prescribe our saltpetre where the ancients employed their nitrum ; and indeed those in the least acquainted with the effects of salts must know, that all those extolled by the ancients announce carbonated alkalies. Thus burnt nitrum  was employed for cleaning black teeth, as at present many use tobacco ashes instead of tooth-powder. It is seen by the works of Aretæus and others, that burnt nitrum  was used as a caustic, till people learned in modern times to prepare the more active causticum potentiale, or sal causticum.

What the ancients say of the taste of their nitrum  seems, however, not entirely applicable to pure carbonated alkali; and much less, or not at all, to our saltpetre. Had they meant the latter, they would certainly not have failed to mention the sensation of coolness which it occasions when applied to the tongue. Galen and Aetius say, that nitrum  is as bitter as gall; but Serapio ascribes to it a saline taste, with a small degree of bitterness; as does also Pliny, only that for bitterness he substitutes the word sharpness. The names of tastes, however, are as uncertain as the names of the colours which occur in the works of the ancients. Both certainly deserve to be more accurately examined, and to be defined by comparing the things to which these names are given. Prosper Alpinus, however, is of opinion that what the ancients called amarum, is not inapplicable to the taste of natrum.

The ancients mention various springs and streams which contained what they called nitrum 1234 ; but nitrous water, according to the present acceptation of the word, that is, water which contains saltpetre, does not exist; and if credit is to be given to Marggraf and others, that they observed traces of saltpetre in some kinds of water, the instances must have been so rare that mention of them could not be expected among the ancients. Their nitrous water was undoubtedly alkaline, and this indeed is not scarce. Such water was recommended by the ancient physicians, both for bathing and drinking 1235 ; and Pliny says, it was singular that the salt of such water would not shoot into crystals, like common salt, which is undoubtedly true 1236.

Alkaline water of this kind, such as that of Armenia, was used for washing, and also by fullers. In Egypt, at present, people wash in the same manner with nitrum.

It appears to me that many kinds of water, which were only impure and not potable on account of their nauseous taste, were considered by the ancients as nitrous. This seems to be proved by the means which they propose for rendering nitrous water fit to be drunk; that is, by throwing into it clay, or some grains of barley 1237. In the like manner, I saw the brewers at Amsterdam improve their dirty water, in some degree, by putting into it kneaded clay, and allowing it to sink to the bottom.

One foundation more for my assertion may be found, I think, in the name borax. The ancient nitrum  by the Arabians was called Bauracon  or Baurach. When that salt, which at present is everywhere called borax, became known to the Arabians, it was at first generally considered as a kind of nitre, and on that account called Baurach, because in most of its properties it approached near to the nitrum  of the ancients, that is, the natrum  of the present day. But afterwards, when the difference became known, our borax, at least in Europe, retained exclusively the general name of Baurach, from which at length was formed the present word borax. My conclusion therefore is, that the nitrum  of the ancients must have been mineral alkali; otherwise it is impossible that our borax, which till modern times was reckoned to be mineral alkali, should have been considered as a nitrum.

For many centuries past, the people in Africa and Asia, and also in Spain and Sicily, have cultivated some kinds of plants, which they dry and then burn to ashes. By regulating the fire in a particular manner, they cause these ashes to assume a certain degree of concretion, or vitrification, by which means they are formed into solid cakes of a grey colour, interspersed with many white and black spots. This substance, which in consequence of the vitrification does not become moist in the air, is broken into fragments, and sent to every part of Europe under the name of soda, for the use of the glass-houses, soap-boilers, dyers, and for other purposes.

These plants were undoubtedly first cultivated and employed in Europe by the Arabians, who made known the use of them. Those first or chiefly employed were named by them axnanusnanusnen, or uscnanon ; and also Hasciscio alcali, that is, herba kali, the plant or herb kali, because the name kali, or, with the article prefixed, al kali, was not given to the plant but to the half-vitrified ashes kali. Hence the chemists call salts obtained from the ashes of plants, alkaline salts. I do not know how old this appellation may be; but it is to be found in Vincent Bellovacensis and in the interpolated writings of Geber and Avicenna, and particularly in a passage quoted by the former from an old alchemist named Jahie, where it is called sal alchali 1238 . All these salts formerly were considered as nitrous salts, or a kind of nitrum. It was indeed soon observed that soda and wood-ashes, which from the earliest periods had been burnt in woody districts, and which are now called potash, were not all of the same nature; but when the difference between the mineral and vegetable alkalies began to be studied, it was then known that soda contains the former, that is, our natrum, and potash the latter, but both indeed often rendered impure by earthy and foreign saline particles; and that there are many plants from the ashes of which mineral and not vegetable alkali is obtained. A question now arises, How old in the Levant is the method of preparing this natrum from the ashes of plants?

Michaelis is of opinion that it is mentioned in Malachi, chap. iii. ver. 2; which passage I shall give according to Luther's translation: “Who shall stand when he appeareth? for he is like the fire of the goldsmith, and the soap of the scourer. He will sit and melt and purify the silver, and make pure like gold and silver.” This learned man here seems to think that the sacred writer alludes to refining the noble metals, and that the word borith  means soda, which indeed may serve as a flux in the purification of them. I at first considered this meaning as true; but, on closer examination, I am fully convinced that we have both erred.

Those who read without prejudice the above passage of Malachi, must remark, that a double comparison or double image is employed. The messenger there promised was to separate the good from the bad, the clean from the unclean. The first occupation is compared with the labour of the gold-refiner; the other, with that of the scourer of clothes. The first image is afterwards heightened, because the poet, in all probability, was desirous of applying the separation of the ignoble parts, such as slag, by means of fire, as being the stronger image which denotes punishment, in a closer manner to the Levites and priests. At the time of the poet, before the invention of soap, people employed for washing either nitre or the saponaceous juice of certain plants, which I have already endeavoured to determine. The borith  of the washer there expressly named, was undoubtedly one of these soap plants, and not the half-vitrified ashes either of soda or potash.

This passage of Malachi was so understood in the oldest times. Professor Tychsen, a true pupil and intimate friend of Michaelis, to whose opinion I subjected my doubts, assured me that Michaelis was never able to convince him of the justness of his exposition; especially as Jerome 1239 , without the least hesitation, understood borith  to be a plant growing in Palestine, and used there for washing; and as the Greek translators, who were much nearer to the period of the poet, and could not be unacquainted with a thing so much used, have translated borith  by the word ποα, a plant.

In Jeremiah, chap. ii. ver. 22 1240 , both the substances formerly used for washing, nitrum  and the soap-plant, are so clearly named, that Michaelis was obliged to admit that we cannot understand there soda or potash, but a ley or soap, the last of which however was not at that time known. But, to speak the truth, potash and soda would not be altogether unfit for washing; at any rate, not less fit than the nether  or nitrum  there named. What may serve, however, to refute entirely the opinion of Michaelis is, that no proof has yet been found that soda is of so great antiquity. For my part, I am acquainted with no older mention of it than that which occurs in the works of the more modern Arabian physicians, Avicenna, Serapio, and others 1241.

All these grounds afford sufficient proof that the nitrum  of the ancients was our natrum, and not our saltpetre. But still, in the account given by the ancients of that salt, there remain many things inexplicable. Thus, for example, no one can accurately define the epithets, chalastricumhalmirhagaagriumspuma nitriaphronitrum, and others, because they do not indicate different kinds, as already said, but accidental properties of the same salt. Without enlarging further on this subject, I shall only remark that Pliny admits a natural and an artificial kind of nitrum, and this division is adopted by Serapio; but the latter term has not the meaning which we affix to it at present. The ancients were acquainted with no other than native nitrum, which they called artificial only when it required a little more trouble and art to obtain it.

Most of the physicians recommend red nitrum, which is mentioned also by many of the modern travellers. When Prosper Alpinus was in Egypt the rose-red nitrum  cost twice as much as the white. The red colour, in all probability, arises from a metallic admixture; yet the red nitrum  may be purer than the other, as red or violet rock-salt is often clearer and purer than that which is colourless.

One of the darkest parts in the history of nitrum  is the following passage of Pliny: “Faciunt ex his vasa, nec non frequenter liquatum cum sulphure, coquentes in carbonibus.” The latter words he seems soon after to repeat: “Sal nitrum sulphuri concoctum in lapidem vertitur.” From these words J. Rhodius 1242  concludes that nitrum fixum was at that time known, because he considered nitrum  to be saltpetre; but in that case with the sulphur, Glaser's sal polychrest must properly have been produced. This, however, was not the case, because nitrum  was fixed alkali. The ancients therefore, when they placed it with sulphur in a crucible upon burning coals must have obtained liver of sulphur, which when it cools is hard, but soon becomes moist when exposed to the air. But I will not venture to determine whether anything of this kind is to be supposed in Pliny, who did not himself fully understand the subject on which he touches.

The account of vessels made of nitrum  is still more singular. Michaelis conjectured 1243  that articles of various kinds were cut out of this substance, not for real use but merely for ornament, in the same manner as similar things are cut out of rock-salt in Transylvania, many specimens of which I have in my collection 1244. But even if nitrum had been compact and strong enough for this purpose, there could not be the same inducement to employ it as rock-salt, which, in consequence of its solidity, transparency, brightness and smoothness, appears to be capable of furnishing vessels equal to those made of the most beautiful crystal. Dalechamp seems to explain the whole as applicable to glazing; but in this case nitrum  could serve only as a flux.

Though it can be certainly proved that the nitrum  of the ancients was an alkaline salt, it is difficult to determine the time when our saltpetre was discovered or made known. As many have conjectured that it was a component part of the Greek fire, invented about the year 678, which, in all probability, gave rise to the invention of gunpowder, I examined the prescriptions for the preparation of it. The oldest, and perhaps the most certain, is that given by the princess Anna Comnena; in which however I find only resin, sulphur and oil, but not saltpetre.Klingenstierna 1245  therefore judged very properly, that all recipes in which saltpetre occurs are either forged or of modern invention. Of this kind are those which Scaliger, at least according to his own account, found in Arabic works, and in which mention is made of oleum de nitro  and sal petræ1246 . But it does not occur in that prescription given by Marcus Græcus, and copied by Albertus Magnus, who died in 1280 1247.

I must still believe that the first certain mention of saltpetre will be found in the oldest account of the preparation of gunpowder, which, in my opinion, became known in Europe in the thirteenth century, about the same time that the use of the Greek fire, of which there were many kinds, began to be lost. Among the oldest information on this subject is that found in the above-quoted work of Albertus Magnus, and the writings of Roger Bacon, who died in 1278. It is doubted whether the first-mentioned treatise belongs to Albertus; but it is certain that the author, whoever he may have been, and also Bacon, both derived their information from the same source.

When M. von Arretin lately announced that he was about to publish a manuscript preserved in the electoral library at Munich, which contained the true recipe for making the Greek fire and the oldest for gunpowder, the same writing, as appears, was printed from two manuscripts in the library at Paris. I have now before me a copy of it, which was transmitted to the library of our university by M. Laporte Dutheil, conservateur des Manuscrits de la Bibliothèque 1248 .

It contains many recipes, but only with a few variations, as in Albertus Magnus; and it may be evidently seen that Roger Bacon employed this writing, which is mentioned by Jebb in the preface to his edition, from a copy preserved in the library of Dr. Mead. Of this Marcus Græcus nothing at present is known. According to some, he lived in the ninth century; but others, with more probability, place him in the thirteenth. Of his work, perhaps, we have only a translation; for, from the surname Græcus, there is reason to think that the original was written in the Greek language. I must, however, remark that Cardan, where he gives directions for making a fire which can be kindled by water, names Marcus Gracchus, but not Græcus. Scaliger, who, as is very probable, had this writing also, makes no mention of it or its author.

This Marcus speaks of saltpetre three times; first under the name of sal petrosum, which occurs also in the same prescription in Albertus Magnus; but the addition, which Albertus does not repeat, is very remarkable. In my opinion, scrophulæ contra lapides  means the incrustation found on walls, which was represented as a kind of leprosy. The addition of ashes, or alkaline salts, the author either forgot or omitted, because perhaps he did not consider it as indispensably necessary. In another place it is said, Lapis qui dicitur petra solis, or, as it is in other manuscripts, salis ; but whether saltpetre is here understood I will not venture to determine. In a third passage we find the words de sale petroso, or de salepetro.

In the works of Bacon the term sal petræ occurs at least three times. According to Casiri, the term pulvis nitratus  is to be found in an Arabic manuscript, the author of which lived about the year 1249 1249. If the work of Geber, already quoted, be genuine, and if this writer lived, as some think, in the eighth century, it would be the oldest where saltpetre is mentioned, in a prescription for an aqua solutiva  or dissolutiva, which almost seems to be aqua regia. I have not observed the name sal petræ in the works of Vincent Bellovacensis, who lived in the thirteenth century.

In a word, I am more than ever inclined to accede to the opinion of those who believe that gunpowder was invented in India, and brought by the Saracens from Africa to the Europeans, who however improved the preparation of it, and found out different ways of employing it in war, as well as small arms and cannon 1250. In no country could saltpetre, and the various uses of it, be more easily discovered than in India, where the soil is so rich in nitrous particles that nothing is necessary but to lixiviate it in order to obtain saltpetre; and where this substance is so abundant, that almost all the gunpowder used in the different wars with which the sovereigns of Europe have tormented mankind was made from Indian saltpetre 1251. If it be true that saltpetre was not known in Europe till the thirteenth century, neither gunpowder nor aquafortis could have been made before that time; for the former cannot be prepared without saltpetre, nor the latter without nitre. But if it be true that this salt was known at a much earlier period in India, it is not improbable that both gunpowder and aquafortis were used by the Indians and the Arabians before they were employed by the Europeans, especially as the former were the first teachers of chemistry to the latter. In my opinion, what I have already related proves this in regard to gunpowder; and what I shall here add will afford an equal proof in regard to aquafortis.

It is difficult to discover the first mention of mineral acids in the writings of the ancient chemists. In the course of their numerous experiments they obtained indeed, at an early period, acids, the utility of which they extol; but each concealed the process by which they were made; and as they had no method of obtaining them pure, they were for a long time unacquainted with the difference between the kinds. Their prescriptions, when they are found, are so contradictory and so carelessly written, that it is almost impossible to conjecture which of the known acids forms the principal component parts in their recipes or mixtures.

It appears to me, that the first intelligible account of aquafortis occurs in the writings of the Arabians, or of the pupils of Arabian chemists. At present I am acquainted with none older than that to be found in the works of Geber. For though I do not believe that those of which we have Latin translations belong to a Geber of the eighth or ninth century, I am ready to admit that they may be, at any rate, of the twelfth. This appears probable, because about that period aquafortis and various arts are oftener mentioned, and in a much clearer manner, in these writings.

It is to be regretted in the history of chemistry, that it is impossible to determine the period of the Greek chemist or alchemist known under the name of Synesius; but it cannot be doubted that he borrowed a great deal from the works of the Arabians. This Synesius, among the chemical solvents, mentions water of saltpetre, which might be considered as aquafortis 1252. But, as he mentions at the same time aqua fæcis, he appears to me to allude to the nitrum  of the ancients, not to our saltpetre, and in general to strong alkaline leys, which indeed are capable of dissolving many bodies.

The monk Theophilus, of whom I have already spoken, and who in all probability lived in the twelfth century, appears also to have been acquainted with aquafortis; for in some of the passages quoted from his works by Raspe 1253 , he speaks of an acid which dissolved all metals. In the writings of Vincent Bellovacensis, in the thirteenth century, some traces, but very doubtful, are found of aquafortis. Where he mentions the different sorts of gold he speaks of dissolving it, but by this expression he does not allude to its treatment with fire, which he speaks of separately 1254. In another place he mentions the different solvents, and among these names vegetable acids, a water of sal-ammoniac, and a water obtained from alum by distillation. He here means undoubtedly a mineral acid 1255. Michael Meier, the most learned chemist of the seventeenth century, says that Vincentius speaks of aquafortis as of a secret; but the passage I have not yet been able to find 1256.

Spielman states that Lullius, who died in 1315, in the eightieth year of his age, gave an account of his obtaining aquafortis from saltpetre by the addition of vitriol, and that Basilius Valentin was acquainted with the use of clay for the same purpose. Picus Mirandula however declares it to be uncertain whether Arnoldus de Villa Nova was acquainted with the acid of saltpetre in the fourteenth century.

It appears to be an old tradition that this acid was first employed at Venice, by some Germans, for separating the noble metals, and conveyed thence as an article of merchandize to every part of Europe. The persons who prepared it were there narrowly watched, in order that the process might not become known. They were employed chiefly for separating the gold from the Spanish silver, and by these means acquired great riches. Hence arose the report that the people of Venice understood the art of making gold; and it is certain that in many countries the gold refiners were for a long time considered as gold makers; but in no period were there more gold makers than in that when separation in the moist way became known. I can however give less account of this art of the Venetians than of the introduction of it into France in the fifteenth or the beginning of the sixteenth century.

William Budæus, who was born in 1467, and died in 1540, speaks of it in his book, printed for the first time in 1516, as a thing entirely new at that period 1257. A man of low extraction, named Le Cointe, first undertook to separate gold from silver at Paris, by means of a water which Budæus calls aqua chrysulca. It is very remarkable, that by means of this water he could separate the smallest particle of gold from silver, and from every other metal; nay, he could even take from vessels their gilding without altering their form. By this art he acquired great wealth; which together with his secret descended to his son, who at the time was the only gold refiner at Paris.

He adds, that the art was exceedingly dangerous as well as unhealthy, and required great precaution. The possessor of it, when he became rich, left the execution of the work to a servant, whom he directed at a distance, that he might not expose himself to the pernicious fumes of the effervescing liquor. The fumes of the acid derived from saltpetre are indeed prejudicial to the health; but the danger has been much exaggerated, and no doubt with a view to deter people from attempting to discover the art, and to furnish a pretence for raising the price of the production 1258.

Budæus relates also, that the gold was left behind undissolved. The silver only was dissolved, and by another art was separated from the water and washed. It may here be easily perceived that Le Cointe employed aquafortis; but if he was able to loosen the gold from gilt vessels without destroying them, he must have used aqua regia, which consequently was not then unknown.

From other information, it appears that the mint at Paris purchased the art from Le Cointe's son, but still kept it a secret. On this account Francis I., by a decree issued at Blois on the 19th of March 1540, authorized the raising the value of coin, in order to defray the expense of fuel and assaying-water. In the middle of the seventeenth century, the preparation of aquafortis and the process of assaying in the moist way were fully known in France. At any rate, in the month of January 1637, the distillers obtained a guild letter, in which aquafortis is mentioned among the articles sold by them.

When saltpetre became necessary to governments for the manufacture of gunpowder, they endeavoured to obtain it at as cheap a rate as possible. No one before suspected that rulers would be justified in exclusively carrying away the incrustation of walls from private houses, which, when it could be used, became accessorium fundi. But the idea of regalia, so often abused, was extended so wide under various pretences, that the saltpetre regale and the letting of it was one of the severest oppressions to which the people were exposed by their rulers, and which occasioned almost as bitter complaints as the hunting regale, founded on no better grounds. I shall not here attempt to delineate the sufferings which were thus occasioned in many countries; they are still fresh in remembrance.

The oldest mention of this hated regale which I myself have found is of the year 1419. At that time, Gunther, archbishop of Magdeburg, granted to some person the right of searching out saltpetre and boiling it, during a year, in the district of Gibichenstein, for which he was to pay a barrel of saltpetre, and deliver to the archbishop the remainder at the rate of five cross-groschens per pound. The succeeding archbishop, Frederick, let in the year 1460, to a burgher of Halle, all the earth and the saltpetre that could be collected from it in the bailiwick of Gibichenstein, for four years, at the annual rent of a barrel of good refined saltpetre. On the same conditions, bishop Ernest, in 1477, let to some one for his lifetime the collection of the saltpetre. In 1544, a certain person obtained the collection of saltpetre from two heaps of rubbish before the gates at Halle. The magistrates of Halle also in 1545 had a saltpetre-work and a powder-mill. In the year 1560, John VI., archbishop of Triers, gave to some one permission to search for and dig up saltpetre. In 1583, the saltpetre regale was confirmed by a Brandenburg decree as a thing long known, and the case was the same with a Hessian of the year 1589.

It is very probable that this example was soon followed by most sovereigns; but even if they had collected and scraped together the nitrous incrustation of all the walls in Europe, they certainly would not have found a quantity of saltpetre sufficient for the gunpowder used in the numerous wars which took place, had not a much greater supply been obtained from India, and particularly from Patna. I do not know whether the Portuguese brought this article to Europe; but that it was imported at a very early period by the Dutch is proved by the oldest ladings of their return ships; and they at length found means to appropriate this branch of trade so entirely to themselves, that the other Europeans for a long time could not obtain any saltpetre in India.

In the seventeenth century, when chemistry began to be studied with more care and attention in Europe, and particularly in Germany, and the component parts and production of saltpetre became better known, many conceived the idea of improving the methods of obtaining it in Europe so much, that it might be possible to dispense with the Indian saltpetre, and flattered themselves with the hopes of thence deriving great advantages. Some proposed to fill tubes with putrifiable substances and earth capable of fixing of the nitric acid; others preferred building vaults of these substances, and Glauber recommended the filling of pits with them. The proposal, however, which met with the greatest approbation was that of building walls of them. Through a confidence in this idea, towns and villages were compelled to erect and maintain a certain number of saltpetre walls, under the most gracious promise that the collectors of saltpetre should no longer be allowed to spoil private dwellings, or render them unhealthful.

But experience has shown that all the means and coercive measures hitherto employed have rendered the European saltpetre much dearer than that obtained by commerce from Bengal. This will be readily comprehended, when it is known that earth richly impregnated with saltpetre abounds in India, and that it may be extracted by lixiviation without any addition, and brought to crystallize in that warm climate without the aid of fire; that the price of labour there is exceedingly low; that this salt is brought from India instead of ballast by all the commercial nations of Europe, where the competition of the sellers prevents the price from ever being extravagantly high, while the preparation of it in Europe, in consequence of the still increasing price of labour, fuel and ashes, is always becoming dearer. This regale will at length be everywhere scouted. In the duchy of Wurtemberg and the Prussian states, where it was most rigidly enforced, in consequence of an urgent representation from the States it was abolished in 1798; but in both countries an indemnification was given to government for the loss. The case also has been the same in Sweden 1259. In the duchy of Brunswick it was soon suffered to drop; but in the electoral dominions it never was introduced.

[The greater part of our nitre is derived from Bengal, where, as in Egypt, Persia, Spain, &c., it exists in the soil. It is separated by lixiviation and crystallization. In France, Sweden and some other countries it is prepared artificially in nitre-beds. These are formed of various animal matters, mixed with lime or mortar-rubbish; the mixture is watered and stirred occasionally, and allowed to remain for a considerable time. The whole is then lixiviated and decomposed by carbonate of potash. The nitre is then separated and purified by crystallization. In some cases wood-ashes are mixed with the animal matters; the decomposition with potash is then unnecessary.

It is a question whether the nitric acid in the nitre arises from the nitrogen of the atmosphere or that in the animal matters. Dr. Davy has found nitre in a cave at Ceylon, where no nitrogenous matter was present; and in some parts of India, Spain, and some other countries, at a distance from all habitations, immense quantities of nitre are reproduced in soils which have been washed the year before. Nitre is directly brought into this country from Calcutta and Madras, in bags containing from 150 lbs. to 175 lbs. each. From 200,000 cwts. to 260,000 cwts. are annually imported into the United Kingdom.

In making gunpowder, the components, the sulphur, nitre, and charcoal should be as pure as possible, and reduced to the finest possible powder; they are sifted and mixed in the proper proportions. The mixture is then made into a cake with water, and ground between calcareous millstones. It is then granulated through sieves in another mill, and again sifted. It is then polished and hardened by revolving rapidly in a cask, and finally dried. The proportions of the constituents vary in different countries; at Waltham Abbey they are seventy-five nitre, fifteen charcoal and ten sulphur. The quantity of gunpowder consumed in this country is enormous; moreover, 4,000,000 lbs. are annually exported, the greater part of which is sent to the western coast of Africa.

The force of the explosion of gunpowder is owing to the sudden disengagement of gaseous products; these consist of nitrogen, carbonic oxide, carbonic acid, and sulphurous acid gases; and their volume has been calculated to amount to 2000 times the bulk of the powder.]


1190  To this subject belong the following works:—Ars Magna Artilleriæ, Auct. Cas. Siomienowicz. Amst. 1650, fol. p. 61. The author thinks that the nitrum of the ancients is not at present known.

Natural History of Nitre, by W. Clarke. Lond. 1670, 8vo. It is here said that the nitrum of the ancients was impure saltpetre, and that the latter is produced from the former by purification.

G. C. Schelhameri de Nitro, cum veterum, tum nostro commentatio, Amst. 1709, 8vo, contains good philological observations, particularly in regard to the period, but leaves the question undetermined.

Saggi sul ristabilimento dell' antica arte de' Greci e Romani pittori, del Sig. Doct. Vin. Requeno. Parma, 1787, 2 tomi in 8vo, ii. pp. 95, 131: a learned but diffuse work. He thinks that the nitrum  of the ancients was our saltpetre; and what others consider as proofs of its being mineralized alkali, he understands as indicating alkalized saltpetre. I am not, however, convinced. Before I ascribe to the ancients a knowledge of our saltpetre, I must be shown in their writings properties of their nitrum  sufficient to satisfy me that it was the same substance.

Commentat. de nitro Plinii, in J. D. Michaelis commentationes. Bremæ 1784, 4to. The author only illustrates the account of Pliny, and states what, according to his opinion, we are to understand in it in regard to alkali, and what in regard to our saltpetre.

1191  [Since the discovery of the immense deposits of nitrate of soda in Peru, this salt, from its being much cheaper, has replaced the nitrate of potash in the manufacture of aquafortis, but it is not adapted to the making of gunpowder owing to its deliquescent property.]

1192  I found the account of the Portuguese saltpetre in Mémoires Instructifs pour un Voyageur. The author of this work was the well-known Theodore king of Corsica.

1193  More accounts of native saltpetre may be found in Recueil de Mémoires sur la Formation du Salpetre. Par les Commissaires de l'Academie. Paris, 1776, 8vo. Del Nitro Minerale Memoria dell' ab. Fortis, 1787, 8vo.

1194  The first, or one of the first, who was acquainted with and made known the cubic saltpetre, was professor John Bohn of Leipsic, in the Acta Eruditorum, 1683, p. 410; but with more precision in his Dissertat. Chymico-Physicæ, Lips. 1696, 8vo, p. 36.

1195  [It is scarcely necessary to inform the reader that the author understands the soda of commerce, which is a carbonate of soda, and not the hydrated or caustic soda of chemists.]

1196  [Crude soda or kelp  was formerly manufactured to a very large extent in the Highlands, by burning the sea-weed, but since the tax has been taken off salt, most of the soda of British commerce is made by decomposing this with chalk and some carbonaceous matter.]

1197  In like manner, a heap of dung covered with earth is lixiviated, and the result, without the addition of ashes, used as saltpetre.

1198  The passage of Jerome relating to Proverbs, xxv. 20, I here insert entire, because I shall often have occasion to employ it:—“Nitrum a Nitria provincia, ubi maxime nasci solet, nomen accepit. Nee multum a salis Ammoniaci specie distat. Nam sicut salem in litore maris fervor solis conficit, durando in petram aquas marinas, quas major vis ventorum, vel ipsius maris fervor in litoris ulteriora projecerit; ita in Nitria, ubi æstate pluviæ prolixiores tellurem infundunt, adest ardor sideris tantus, quod ipsas aquas pluviales per latitudinem arenarum concoquat in petram; salis quidem vel glaciei aspectui simillimam; sed nil gelidi rigoris, nil salsi saporis habentem, quæ tamen, juxta naturam salis, in caumate durare, et in nubilos, aere fluere ac liquefieri solet. Hanc indigenæ sumentes servant, et ubi opus extiterit, pro lomento utuntur. Unde Judæo peccanti dicit propheta Jeremias: Si laveris te nitro, et multiplicaveris tibi herbam borith, maculata es in iniquitate tua, dicit Dominus Deus. Crepitat autem in aqua quomodo calx viva; et ipsum quidem disperit, sed aquam lavationi habilem reddit; cujus natura cui sit apta figuræ, cernens Solomon ait: Acetum in nitro, qui cantat carmina cordi pessimo. Acetum quippe si mittatur in nitrum, protinus ebullit.”

1199  Herodot. ii. cap. 86 et 87.

1200  Histor. Ægypti Naturalis iii. 2. See also Forskäl Flora Ægyptiaco-Arabica, p. xlv.

1201  [Duhamel proved soda to be distinct from potash in 1736, Marggraf confirmed  it in 1758.]

1202  Lib. xxxi. cap. 10.

1203  De Simplic. Med. Facult. ix. Dioscorides also, v. 131, speaks as if it had been well known that nitrum  was commonly burnt.

1204  Phil. Transactions, 1771, vol. lxi. p. 567.

1205  De Igne, p. 435, ed. Heinsii, where he speaks of the heat produced in lime by slaking it. Aristotle also mentions together κονία and νίτρον, on account of similar properties. Problemat. i. 39. ed. Septalii, p. 71.

1206  Hist. Plant. iii. 9, p. 50.

1207  xxvi. 8.

1208  xiv. 20.

1209  De Re Rustica, lib. i. c. 7. Little, however, depended on the wood; the principal thing was the sprinkling with water.

1210  xxxi. 10.

1211  xxxi. 7. Here express mention is made of brine.

1212  Taciti Annal. xiii. 57.

1213  Lib. xxx. 7.

1214  This is particularly the case in regard to Aristot. Auscult. Mirab., as I have remarked in the preface to my edition.

1215  In the island of Dagebull, and also in Faretoft and Galmesbull, Frisio salt is made in the following manner. The inhabitants proceed along the coast in small vessels, and at low water go on shore on the mud, which they dig up till they come to a kind of earth called torricht ; it is of a turfy nature, and interwoven with roots. This earth they convey to the islands, where they spread it out in the sun and leave it to dry, after which it is formed into a heap and burnt to ashes. What remains is again spread out, moistened and trod upon with the naked feet; the small stones and other useless parts are picked out, and being again dried and besprinkled with water, the ley is put into salt-pans and boiled into salt.

1216  Mémoires de l'Acad. de Bruxelles, 1777, i. p. 345.

1217  Elementa Chemiæ. Lugd. Bat. 1732, 4to, i. p. 767.

1218  Boyle considered the words of Solomon as a proof that nether  must be fixed alkali; and he was the more convinced of it when he saw nitre obtained from Egypt effervesce with acids.

1219  See the History of Soap  in vol. i.

1220  Plin. xxxvi. 26, § 65. The use of nitrum in making glass is often mentioned.

1221  Plin. xxxi. 10.

1222  Lib. xxx. 10.

1223  Forskäl Flora, p. xlvi.

1224  Plutarchi Sympos. lib. vi. at the end.

1225  Theophrasti Histor. Plant. ii. 5.—Geopon. ii. 35, 2; and ii. 41.—Palladius, xii. tit. i. 3, p. 996.

1226  Virg. Georg. i. 193.—Plin. xviii. 7. 845.—Geopon. ii. 36, p. 184.

1227  Columella, ii. 10, 11.

1228  Plin. xix. 8, § 41.—Pallad. iii. 24, 6.—Geopon. xii. 17, 1.—Theophrast. de Causa Plant. vi. 14.

1229  Plin. xxxi. 10; and xix. 5, § 26, 10.

1230  Apicius, iii. 1, p. 70.—Martial, lib. xiii. ep. 17.—Plin. xix. 8, §41, 3; xxx. 10.—Columella, xi. 3, 23. [Carbonate of soda, as is well known, is still frequently used for this purpose in culinary operations.]

1231  Herodot. ii. 87.

1232  Our tanners use unslaked lime for a similar purpose.

1233  Annot. to Dioscorides, v. 89, p. 951.

1234  A catalogue of such waters may be found in Baccii Liber de Thermis. Patavii, 1711, fol. v. 5, 6, 7, p. 160. [Carbonate of soda occurs for instance in the celebrated mineral waters of Seltzer and Carlsbad, and also in the volcanic springs of Iceland, especially the Geyser.]

1235  Plin. xxxi. 6, § 32, p. 556. Vitruv. viii. 3, p. 158.

1236  xxxi. 10.

1237  Plin. xxiv. 1; xxxi. 3, § 22. Geopon. ii. 5, 14, p. 85.

1238  Speculum Naturæ, vii. 87, p. 480.

1239  Hieronym. ad Jerem. ii. 22.

1240  “For though thou wash thee with nitre, and take much soap, yet thine iniquity is marked before me, saith the Lord God.”

1241  In regard to the two plants usneeasne, and usnemassuan, see Avicennæ Canon. Medic. Venet. 1608, fol. pp. 338, 406, 407. Serapio de Temperam. Simplic. p. 164. In Du Cange's Gloss. Gr. p. 12, addend. ἀλκαλη, and in Gloss. Lat. v. the word alcali  is quoted only from modern writers. That kali, however, does not mean the plant, but the concrete ashes, is proved by the explanation in Castelli's Lexicon.

1242  In the annotations to Scribonius Largus, p. 228.

1243  Commentationes, p. 145. Recueil des Questions, &c., p. 231.

1244  Such things were known to Aristotle. See Mirab. Ausc. c. 146.

1245  Dissertat. de Igne Græco. Upsaliæ, 1752.

1246  De Subtilitate, xiii. 3. p. 71. ed. Francof. 1612, 8vo.

1247  De Mirabilibus Mundi, p. 201; at the end of the book De Secretis Mulierum. Amst. 1702, 12mo.

1248  Liber Ignium ad Comburendos Hostes, auctore Marco Græco; ou, Traité des Feux propres à détruire les Ennemies, composé par Marcus le Grec. Publié d'après deux manuscrits de la Bibliothèque Nationale. Paris, 1804, three sheets in quarto.

1249  Biblioth. Arab. Hisp. Escurial, ii.

1250  See the works quoted in Fabricii Bibliograph. Antiquar. p. 978. In the year 1798, M. Langles proved, in a paper read in the French National Institute, that the Arabians obtained a knowledge of gunpowder from the Indians, who had been acquainted with it in the earliest periods. The use of it in war was forbidden in their sacred books, the Veidam or Vede. It was employed in 690 at the battle of Mecca.

1251  The following may be advantageously consulted:—Archæologia, v. p. 148; Henry's Hist. of Great Britain, vol. iv.; Muratori Antiq. Italiæ Medii Ævi, ii. p. 514; Watson's Chemical Essays, i. pp. 284, 327; Histoire de France, par Velly, xvi. p. 330; Dow's Hist. of Hindostan, vol. ii.; Erdbeschreibung der entferntesten Welttheile, ii. p. 159; Stettler Schweitzer Chronik. p. 109. The inhabitants of Berne purchased the first gunpowder from the people of Nuremberg in 1413.

1252  A fragment from the writings of Synesius was printed, for the first time, in Frabricii Bibliotheca Græca, viii. p. 236, where the words occur.

1253  Raspe on Oil-painting. London, 1781, 4to, p. 145.

1254  Speculum Naturale, vii. cap. 13, p. 432.

1255  Lib. vii. cap. 88, p. 480.

1256  Symbola Aureæ Mensæ. Francof. 1617, 4to, lib. vii. p. 335.

1257  De Asse, 1556, fol. lib. iii. p. 101.

1258  Les Anciens-Minéralogistes de France, par Gobet. Paris, 1779, 2 vols. 8vo, i. p. xxxiv. i. p. 51, 284; ii. p. 847.

1259  [The celebrated chemist Baron Berzelius, professor at Stockholm, states in his Manual of Chemistry (edit. 1835, vol. iv. p. 86), that every possessor of land in Sweden is still compelled to deliver a certain quantity of saltpetre yearly to the state, and gives directions for testing its goodness.]