Mr. Jeremiah Brown's method of making faltpetre; published in Virginia by order of the trustees for the improvement of arts and manufactures, and in England by order of the fociety for the encouragement af arts, manufac tures, and commerce. SALTPETRE is to be found in tobacco - houses, stables, cowhoufes, hen and pigeon-houses, and in any covered place where the influence of the fun feldom reaches. A fixty-feet tobaccohoufe will yield upwards of 16 c. weight a year, and fo in proportion for larger or fmaller houses. In order to prepare the floors for attracting nitre, all dung and other trash must be removed; and if the floors are not level, they must be made fo by laying on marle, or any fail not too ftiff, which must be lightly trod down with the feet. The floor being thus prepared, fprinkle ftrong ambeer over it, made from tobacco-trafh, and cover it with wet ground leaves, or other tobacco-trafh, for a fortnight; then clean out the trash, and in any cool dry morning that fucceeds, you will find on the floor the nitre attracted and condensed like hoar-froft; fweep this off lightly, and put it by in fome hogfheads, or fafe place in your houfe, till you have leifure to go through the following procefs. This work you must carefully repeat as often as you obferve the abovementioned appearance of nitre on your floors; by which means you will be furnished with a competent quantity to employ a leisure day. The procefs. Make a lye from this earth in the fame manner as is ufually done for foap, noting that the earth is not to be hard packed on the ftraw in the bottom of your lye veffel, which would retain the water to be poured on it too long, and overcharge it with faline par-. ticles, to the great interruption of the process: place the earth hollow in the veffel, for the reception. of the water; the first put to it must be warmer than new milk from the cow; afterwards add cold water: fix a veffel to receive the lye as foon you begin to put the water in, as it will not remain long upon the earth, but in a few minutes begin to drop into the receiver: if it runs foul, it must be returned: upon the earth: as foon as it: has dropped a gallon, you may begin to boil it in a cast-iron pot. Every bushel of earth will require near eight gallons of water. Continue to boil it gently until you have fully charged your pot with the lye, and you will find the watry particles evaporate until it is reduced to a thick oily confiftence, fhooting into fmall icy crystals, which you will easily perceive by expofing the fuds, in a fpoon, to a cold place: then put the liquor out of the pot into wetted wooden trays, and fet it by in a cool place for the firft growth: if you accidentally boil it too thick, add a little cold water: when your trays have ftood with the fuds a few hours, you muft raife one end to let the lye drain off from the faltpetre, which is the first growth, and which, by boiling a second time, will yield you a fresh quantity. After it is thus drained and become dry, you may put it into cafks or tubs, until you have leifure, without prejudice to your crops, to refine. To refine falt-petre. Put into your pot about a third of the quan quantity it will hold of this firft growth, and fet it over the fire: you are to be provided with an iron rod, or poker, to ftir it: as foon as it begins to melt, you will fee it begin to boil furioufly: keep it well ftirred down, as at this time it is very apt to take fire, which will deftroy the whole: when you observe it in the boiling to look of a dirty white, flacken your fire, and ftir it brifky for a quarter of an hour; then increase your fire, and continue the ftirring, though the danger of burning it is now over: the pot, before it is fufficiently melted, will be, at the bottom, of a flaming red, and the matter will appear like boiled cream; and when it becomes whitifh and liquid, pour it upon a ftone, or fome earthen vessel, or a hard wellrammed earthen floor, clean fwept. As foon as it is cold, it will become hard, and if you throw it upon a stone, will ring like broken china. If you have not leifure immediately to clarify it, put it into a tub in a dry place until fome convenient opportunity. To clarify coagulated cream of nitre. To every pound of this matter put fix pounds of water, after you have broke it into fmall pieces: put your pot upon the fire, and stir it until it is well diffolved; then make the fire all round the pot, which will cause it to boil in the middle, and prevent any wafte by its drying and fticking on the fides of the pot; and as foon as the earthy matter begins to fettle in the pot, pour the liquid into a tray, or other open veffel, that its fediment may fettle: pour off the clear liquor, and evaporate it with gentle fire, until in a spoon it will shoot into cryftals; then pour it into your tray, with dry sticks fixed across, fo as to be a little below the furface of the liquor; fet this by in a cool place, where it may fland until it shoots into clear tranfparent cryftals; then pour off the liquor, and fet the tray fo as to drain it off perfectly dry. Thus your faltpetre is completely made, and in a few days will be dry enough to remove out of your trays into cafks or vessels proportioned to the quantities. The liquor you laft poured off muft be again evaporated over the fire, for it will yield faltpetre equally good as the former; and thus continue the operation, until all the watry particles are totally evaporated. N. B. The earth, from which you have extracted the faltpetre, and all the washings of your veffels, if you lay it by thinly spread, in your houfe, will turn to profit, as it continues to be peculiarly proper to attract and abforb the nitre floating in the air; add alfo the earthy matter which fettles in the refining and fhould you be in want of houfe-room, you may spread it upon the earth, covered in the manner that fodder ftacks are: it will produce faltpetre full as well as a tobacco-houfe, taking care that the north-end be always open, and that it be defended as much as poffible from rain. I : A new process for obtaining Nitre. Have lately feen in the public papers mention of a defign to establifh in this kingdom the manufacture of nitre; and being defirous to contribute all that lies in expe my power to fo useful an undertaking, I fhall with your concurrence fubmit to the public, a detail of fome proceedings I made fome years ago for procuring that neceffary article; in which I not only mean to point out what the conftituent parts of nitre are, and deliver a method of making it here, but, by the recital of various experiments ineffectually made on the materials beft recommended for the purpose, prevent any further expectations from thofe fubftances; and hope, for the future, to fecure every perfon from falling a prey to the infinuations of impoftors and ignorant pretenders to the art, as hath already been too often rienced. Having perused what Hoffman, Stahll, Boerhaave, and others, have delivered on the formation of nitre; and being furnished with an account of the nitre works near Paris, and with the method of making this falt at Calcutta, I entered upon the fubject with as much affiduity and attention, as a man can apply to one he is either pleafed with, or interefted in. The writers above mentioned differ fo little in their accounts of the confitution of nitre, and the materials which fupply it, that I fhall, for brevity fake, confine myfelf to what is delivered by Hoffman; who is, indeed, more particular and extenfive on the fubject than any of the reft. He fays, in the first place, that nitre has two principles or elements; one the univerfal primogenial fimple acid, which inhabits the air quod ventre fuo portat, the other an alcaline fulphureous fat earth; and that this laft is a matrix which by attracting to itself, and imbibing the former from the air, conftitutes nitre. He further obferves, that the fubftances which fupply nitre in greatest plenty are the rubbish of demolished houses, all kinds of earth, clay, and loam, lime, afhes, and foap-boilers dregs; and that thefe : always produce most nitre, in proportion as they are combined with the excrements and urine of ani- !. mals, and with corrupted vege tables. All these materials I foon furnished myself with, and for greater certainty procured fome of them from different places; but: after frequent trials by drenching and boiling them in water, could not procure any thing at all like nitre from them. I then provided a great number of flat glazed earthen pans, and in thefe expofed the fame fubftances for feveral months in a dry ftate to the air, but found myself equally difappointed. I likewife placed in the fame fituation a quantity of the vegetable alcaline falt, called pearl afh, fome of it alone, and fome mixed with the forementioned earthy fubftances; but to no better purpose; for which I am induced to believe, notwithstanding the authority of Hoffman, and the opinion of many concerning the refidence of the nitrous acid in the air, that it is not to be found therein; and this I am the better authorised to deliver, as I never could procure, after proper trials, any vef tiges of nitre from hail, fnow, rain-water, or dew. These expe riments terminating wholly fruitlefs, I determined to go back to the place where I once intended to fet off from; if the accounts I had met with in authors had not flattered me with hopes of a more fpeedy mode of acquifition. The decompofition of nitre was now un dertaken; dertaken; it was well known that every kind of falt confifts only of two materials, an acid, and an alcali; but the decompofition was performed to come at the proportions of thofe materials, and more especially that the nature of the alcali, in the conftitution of nitre,, might be precifely known. Two methods were made use of for this purpose, the diftillation of nitre in a retort to procure its acid apart from its alcali, and the deflagration or calcination of nitre in a crucible, to procure its alcali feparate from its acid. The proceffes for thefe purposes are fo well known that there is no occafion to defcribe them; I fhall only take notice here that the alcali procured from calcined nitre was found in all refpects, and in every mode of trial, fimilar to that which every kind of vegetable burnt to afhes affords. That this alcali being added to the acid obtained by the diftillation before mentioned, recompofed a pure and perfect nitre, and that nitre equally pure was obtained by faturating the fame acid with the common vegetable alcaline falt, called pearl afh. From this account it will appear that nothing more is wanting to the formation of nitre, than a fuitable combination of a vegetable alcaline falt with the nitrous acid; and that all that Hoffman and others have faid of the ufe of alcaline and fulphureous earths, excrements, and putrefied vegetables, has ferved to mislead thofe who have attempted the manufacture in England; neither of thofe fubftances can poffibly produce nitre, if no vegetable alcali has been mixed with them; and it is moft probably owing to the use of wood afhes in mortar that the rub bifh of old houses in France affords nitre, while from rubbish in England, where no wood afhes are ufed, nothing like nitre can be obtained. The nature of the alcali of nitre thus determined, there remained nothing more than to find the refidence of the nitrous acid; and having failed of it both in earthy fubftances, and in the air, I refolved to fearch for it in water. All waters that are averfe to a folution of foap, and commonly called hard, are known to be impregnated with a mineral acid, and that however bright and tranfparent fuch waters appear, they always contain as much earthy or metalline matter of fome kind or other, as the fort and quantity of acid they are poffeffed of is capable of diffolving; it was likewife known, that by adding the vegetable alcali to any fuch water, the combination of its acid and mineral would be deftroyed, and a new fubftance or falt be compofed by the vegetable alcali taking the place of the mineral; but thefe kind of waters had not been fo fully and artfully examined as to be fufficiently known and properly diftinguished; they had paffed promifcuously by the character of vitriolic waters. In order to fatisfy myself more particularly concerning their qualities, I procured fpring-water from va rious places in and about London, and among them met with feveral, which by adding a folution of pearl afh in common water, had their mineral matter precipitated, and afforded a pure nitre. It may not be amifs here to explain the nature of precipitation. The tenure that every kind of diffolved matter has in a folvent, is held only by a degree of affection, if it may be fo called, called, between the two parties, and is always found to give way to fuperior influence, viz. to a greater affinity between one of the parties, and fome fubftance added, than does fubfift between the parties firft united; this is the caule of every kind of chemical precipitation. Gold diffolved in aqua regia is precipitated by adding copper to the folution ; the copper in the fame manner gives way to iron, and iron to an earth or vegetable alcali. In the fame manner, and by the fame law, all waters that are impregnated either with the marine, the vitriolic, or the nitrous acid, and which have their acid faturated or neutralifed by any kind of mineral they have met with in their paffage or refidence under ground, will be obliged to part with that mineral by adding to them any kind of vegetable alcali; and this by the greater affinity there is between their acid and a vegetable alcali, than between their acid and any kind of earth or metal whatever. The method of making Nitre. To any quantity of fpring-water which contains the nitrous acid, put fome folution of pearl-afh in common water; this immediately will make the spring-water turbid; add gradually more of the folution of pearl-afh, as long as any cloudinefs is made in the water, but no longer the faturation of the nitrous acid with the folution of pearl-afh fhould be nicely adjusted. Suffer the liquor to ftand undifturbed till all the cloudinefs is fallen to the bottom; when this is done, decant the clear liquor from its fediment, and boil it until it is reduced to a brown colour, not un like small beer, then fet it by, and fon after it is grown cold it will fhoot into cryftals. The fyftem of cryftallization is, That water can only diffolve, and keep fufpended in it, a certain fixed quantity of every kind of falt; but the quantity foluble in warm water greatly exceeds that in cold; fo that when any water, fully charged with falt by the affiftance of heat, is reduced to a state of cold equal to air, fo much of the falt as owed its folution to the impofed heat of the lixivium, will shoot into cryftals, but no more; and thus by fucceflive evaporations of a lixivium, all its falt may be feparated from it. The fpeediest way of knowing if the lixivium, or springwater which has been faturated with pearl-afh, will afford nitre, is this: As foon as the lixivium is reduced by boiling to a brown colour, dip into it a piece of whitish brown paper, and having made it thoroughly dry, apply it to the flame of a candle, where, if instead of being fet on flame, it only takes fire, and runs on in circular bright fparks, until all the paper is confumed, it is certain it will afford perfect nitre. It is very obvious, after all, that nitre cannot be made to advantage in this way in or near London; the evaporation of fo large a portion of water, which the lixivium must neceffarily fuffer to bring it to a ftate of cryftalliza tion, will be too expenfive in the article of fuel; yet there are means of leffening this expence, and putting all the proceedings into fuch a way as may make it be found a profitable undertaking; but the difplay of this and other circum, ftances neceffary for carrying on fuch a work, muft be referred, for want |