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.