A History of Inventions, Discoveries, and Origins, Volume II (of 2)

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 substance¹²⁰². 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 strengthened¹²⁰³. 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 salt¹²⁰⁴, 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 Theophrastus¹²⁰⁵ 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 Theophrastus¹²⁰⁶ that nitrum was said to be produced from oak-ashes; and Pliny¹²⁰⁷, 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 nitrum¹²⁰⁸. 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 Rhine¹²⁰⁹. Pliny says¹²¹⁰ that oak timber had before been burnt for that purpose. In another place he mentions a similar process among the Gauls and the Germans¹²¹¹, as Tacitus does among the Hermanduri and the Catti¹²¹². The former also states, on the authority of Theophrastus, that the Umbri burnt salt in the like manner¹²¹³. 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 Aristotle¹²¹⁴.

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 Denkwerth¹²¹⁵, 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 Brussels¹²¹⁶ 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.

Boerhaave¹²¹⁷, 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 intelligible¹²¹⁸. 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 volume¹²¹⁹. 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 nitrum¹²²⁰, 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 saltpetre¹²²¹; 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 Pliny¹²²², 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 health¹²²³.

When meat which was too fresh was to be dressed, it was put into nitrum¹²²⁴, 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 soft¹²²⁵. 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 fruit¹²²⁶; but others, security against beetles, which eat the fruit and leave the husks empty¹²²⁷. When cabbages were transplanted they were strewed over with nitre, and by these means were said to come sooner to maturity¹²²⁸. Radishes also were treated in the same manner, or besprinkled with nitrous water, in order to make them more tender¹²²⁹.

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 saltpetre¹²³⁰.

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 nitrum¹²³¹, which, as above shown, was burnt, and in general mixed with unslaked lime, and consequently caustic¹²³²; 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. Matthioli¹²³³ 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 nitrum¹²³⁴; 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 drinking¹²³⁵; and Pliny says, it was singular that the salt of such water would not shoot into crystals, like common salt, which is undoubtedly true¹²³⁶.

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 barley¹²³⁷. 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 axnan, usnan, usnen, 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 alchali¹²³⁸. 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 Jerome¹²³⁹, 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. 22¹²⁴⁰, 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 others¹²⁴¹.

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, chalastricum, halmirhaga, agrium, spuma nitri, aphronitrum, 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. Rhodius¹²⁴² 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 conjectured¹²⁴³ 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 collection¹²⁴⁴. 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. Klingenstierna¹²⁴⁵ 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 1280¹²⁴⁷.