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.