# Essays Upon The Making Of Salt-Petre And Gun-Powder/Provincial Works Philadelphia

New York Colony Committee of Safety, pages 23–33
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The Process for extracting and refining Salt-petre, according to the Method practised at the Provincial Works in Philadelphia.
Published by Order of the Committee of Safety, in that City.
SALT-PETRE, or Nitre, is found in a large quantity in different materials, sometimes mixed and incorporated with stones, and in earths which are exposed and open to all weathers; but the most common places where it is found, is in the earth which forms the floor either of sheep, horse or cow stables, or sheds, in old out-houses, in cellars, and under barns where any animals usually shelter, or any other covered place where any animal or vegetable substances mixed together with earth have been collected, and have lain a long time; and it is said those places where tobacco is manufactured, &c. produce it. A very important part of the Salt-petre maker's knowledge consists in a judicious choice of the materials; and no directions can be given that will avail much; a few experiments properly attended to, will afford more instruction than any written directions; nevertheless, by way of caution, it may be proper to observe, that where stables are constantly used, you must take the earth that lies near the manger, otherwise it will have too great a mixture of the ​ [24] urine and dung of the animals, which will produce Sal-amoniac instead of Salt-petre; and it is considered as a rule for the choice of materials, that the longer they have lain together, the greater chance there will be of getting Salt-petre out of them.
When the materials are collected, they extract and refine the Salt-petre by the following easy process, which I shall divide into six parts, to render it plain and easy of comprehension, viz.
1. To make the Lye.
2. The first boiling to prepare it for filtering.
3. Filtering or straining the Lye.
4. The second boiling to separate the sea-salt and preparing it for crystalizing.
5. Crystalizing the Salt-petre
6. Refining the crystals of Salt-petre.
First, To make the Lye.
Take a tub or tubs, according to the extent of your works, but not to exceed the size of half a hogshead in depth, make a hole in the bottom near one edge, fit a plug or spigot to it, lay a wisp or straw over this hole, then fill the tub tightly with the earth which you have found to contain Salt-petre, pour as much cold water on it as will fill the tub to the brim, after it has soaked into the earth, keep your tubs in a warm place, that the water may not freeze, and in about ten or twelve hours draw off the water at the hole in the ​ [ 25 ] bottom, till it has all drained off this water will have dissolved a great part of the Salt-petre that was in the earth, and runs off very foul, and is what we call the lye. Secondly, Of the boiling to fit it for filtering. Take any kind of boiler and put your lye into it, in the foul state which it was drawn off of the earth, cover your boiler with a lid, and boil the lye away with a brisk fire, to about one fifth of the quantity, if it should be reduced something more or less, it is not material, this first boiling being only to prepare the lye for straining, which is better done while it is hot, than while it is cold, and the reducing of it in quantity makes the operation of filtering it more expeditious. Thirdly, to filter or strain the lye. Prepare yourself with a cask which must be proportioned to the quantity of your lye, put a false bottom in it, about two or three inches above the true bottom, or otherwise make a kind of lattice with strips of boards or small twigs, in the same manner as is used in setting common lye tubs, on the top of this false bottom or lattice work, a layer of straw must be placed, the straws being cut of a proper length to extend across the tub, and must be laid about two inches thick, as even and parallel with each other as conveniently can be; over this another such layer of straw must be put so as to cross it, and of about the same thickness : This straw must bee pressed down, and confined by some slips of boards laid across it, tight within the tub, on this spread straw an inch or two in height, then add some live ashes about five inches thick; lastly, have a piece
of board about the size of a plate to place upon the top of the ashes, in order to break the fall of the lye when poured into the tub. The tub thus prepared, is called an asher. If the tub for this purpose should not be properly proportioned to the extent of your works, as was before observed, the quantity of ashes may be too great, and you will be disappointed of getting Salt-petre, having Pot-ash instead thereof. At the Provincial Works their filtering vessel, or asher, will contain better than a barrel, in which they put near a bushel of ashes. This is sufficient for the lye drawn from twenty tubs of earth at least, each the size of half aa hogshead; of course, where you have but one such lye tub, the asher must be small in proportion, and not above one twentieth part of that quantity of ashes; perhaps some may think the ashes wholly unnecessary, but for their information I would observe, that in general the Nitre will not shoot into crystals, without either ashes or pot-ash being added to the lye, it being absolutely necessary to detach the Salt-petre from other unfit substances which it had joined to in the earth. The ashes should be changed every fourth time your filtering vessel is used, but the other parts of the tub may continue so long as you can refine your lye through it; this kind of filtering tub will be scarcely necessary unless the making Salt-petre is intended to be continued, then it will fully recompence the trouble and expence of making it, as it refines the lye expeditiously and well; if a single or a few experiments are only intended to be made, ten or twelve inches deep of cut straw put into a cask, with the proper quantity of ashes above it will answer the end very well. ​ [ 27 ]
The filtering tub or after being prepared, pour the lye after the first boiling hot out of the boiler into the said tub, and draw it gently off; return it back again two or three times, until it comes off clear and fine. Fourthly, Of the second boiling, to separate the sea salt from the lye, and to strengthen the lye to prepare it for crystalizing. The lye which has been sufficiently refined by running through the filtering vessel, must now be returned into the kettle and boiled a second time, but with more gentle sise towards the latter part of the boiling, otherwise it would be apt to boil over; the boiler must be kept covered during this boiling, in the same manner as was directed in the first boiling. To know when the lye has boiled away enough in order to separate the salt, examine it from time to time by putting about a spoonful of it in a saucer and setting it in a place where it will cool, if it is of a proper strength, a great part of the lye will harden, and shoot in the form of crystals, or sometimes in grains, if the quantity of sea salt be great; when this is the cafe, the lye has boiled almost enough. When the lye is boiled to this strength, if there is any sea salt, it would settle at the bottom of the boiler, and should be taken out with a skimmer, and put into some suitable vessel, for the Salt-petre lye to drain off into the kettle; this salt retains some Salt-petre in it, and is said to be very suitable to cure meat with, and by a farther refining may be purified fit for table use. ​ [ 28 ] The reason assigned for the sea salt's settling to the bottom is, that water will melt the Salt-petre more readily than it does sea salt, but when barely sufficient to dissolve the Salt-petre, it will then dissolve some sea salt, but as soon as the water is boiled away so much that there remains only enough to dissolve the Nitre, the sea salt then settles to the bottom, for the nitre lye of this strength has no more power to dissolve the sea salt, that water has to dissolve a stone. After all the sea salt is taken out, which can be done by this method, continue the boiling till about one fourth of the remaining lye is boiled away, then it must be put into a tub large enough to contain the whole of it; this tub is called a stander, and is somewhat broader at bottom than at top, having a tap fixed about two inches above the bottom; let the liquor stand in this tub till it is nearly as cold as new milk, by which time the gross foul matter which will not dissolve in the water will be settled to the bottom, and amongst it there usually is a good deal of sea salt, as the liquor is not capable of retaining so much salt dissolved in it after it has cooled, as while boilingl the liquor is now ready for crystalizing, which forms the fifth part of the progress. Fifthly, To crystalize the Salt-petre. Having any kind of a vessel, either of metal, wood, &c. provided it is large enough; at the provincial works they have sinall tubs that will contain about three gallons each; the liquor prepared for crystalizing by the former part of the process, is drawn out of the stander by the tap into these tubs, as long as it will run tolerably clear, ​ [ 29 ] filling them about two thirds full, then set these tubs in a cool cellar, and let them remain there twenty-four hours at least, if it has been boiled sufficiently the Salt-petre will be formed into beautiful crystals, but somewhat foul; pour off the liquor that remains, and set the tubs on one edge to drain; this liquor is called the mother of lye, and should be returned into the kettle with your next boiling, or may be further boiled down by itself, and set out to crystalize again as it is very strong of Salt-petre;if there should be no Salt-petre settled in your tubs after standing the time directed, it is a sign your liquor has not been boiled enough, therefore you should return it again into the kettle, and boil it about one half away, proceeding as has been already directed to separate the sea salt, &c.
Sixthly, Of the Refining. When you have a sufficient quantity of Nitre made, you may proceed to refine it, which is performed thus: Put your Nitre into a boiler that will hold about one third more than your quantity of Nitre, add as much water as will cover the whole mass one inch, after it has soaked through it, put it on a gentle fire, keep continually stirring it quite to the bottom till the Salt-petre is all dissolved, take off the foul scum as it rises, which you must continue to do as long as any appears, when the scum has nearly done rising, the sea salt must be taken from the bottom of the kettle with the skimmer, and which is nearly on sixth part of the Salt-petre; it will be proper for you to taste this as you take it out of the kettle, or you will be apt to be deceived by its appearance while wet,
C 3 ​ [ 30 ]
wet, by its resemblance to the wet Nitre which you have in the kettle to refine, but it is readily distinguished from it by the taste. When you have taken all the sea-salt out of the kettle, put into the liquor while a-boiling, about one quarter of an ounce of powdered allum for every twenty-five pounds of Salt-petre, and in proportion for any other quantity; it will occasion it to boil violently and a great foul scum to rise, take iff the foulness, and have some cool water at hand to prevent the liquor from boiling over, which it would otherwise do; you must continue the boiling a little while after the addition of the allum, then take the kettle off the fire, cover it over with a coarse wet linen cloth, and lay a cover of boards over that, put it in a cool place in a cellar, &c. where it must remain about two or three days, then pour off the liquor, on another lye, and drain it from the Salt-petre by settling the kettle an edge, when it is drained turn the kettle bottom upwards for to get your Salt-petre out, which will by this time form itself into a handsome cake. If it is not sufficiently refined this time, repeat this sixth part of the process over again, and you will have it sufficiently fine for any purpose; then put your cake on a heap of dry ashes, which will imbibe and draw off all the moisture that remained in the cake, if not , renew the ashes till it does. This concludes the whole business of extracting and refining Salt-petre fit for the powder-maker, as it is practised at the Provincial Works. T H E foregoing process has already had the experience of many in the province, and particularly ​ [ 31 ] larly in Philadelphia and the town of York. It is simple, and may be practiced in families without any additional expence of fuel, or even of labour, as it only requires the over sight of any person in the evening, after the work of the day is concluded. The process is described with such exactness, the Committee have reason to think few or none will fail in the undertaking, but if that should sometimes be the case, in the first attempt, from too little attention to the direction given, a second would doubtless succeed. The Assembly of this province have granted a premium of 25 l. per hundred weight, which is 5 s. per pound, for all Salt-petre made in this province, and thrown into the public magazines; and the Committee of Safety, through whole hands the premium is to pass, do hereby, for the next three months, leave it in the option of the makers of this article to receive one fourth of the weight thereof in gun-powder, to be delivered to the several persons appointed to take in the Salt-petre in the different counties within this province, the names of whom will be published soon. The Committee need not remark to any intelligent and sensible man, in the province, the indispensable necessity there is, of instantly providing ourselves with a large quantity of Gun-powder, when the quarrel between the mother country and the colonies is drawing to a hasty decision by arms, when the Ministry threaten to overwhelm us the ensuing year, with numerous mercenary soldiers, brought even from the most distant and barbarous nation in Europe; at a time too, when from the wicked vigilance and industry of this Ministry, every ​ [ 32 ] very court in Europe has been solicited and pre-vailed on so far, to aid their designs against our liberties, as to refuse selling us either arms or ammunition. But thanks to Almight God, we have those means and resources within ourselves, which if not shamefully neglected and overlooked, will consound all their artificies and conspiracies; the principal of these is the knowledge of making Salt-petre, by which we may, in a very short time, if it be practised by every family in the country, who are surrounded with abundant materials for the purpose, be relieved from the necessity of depending upon a precarious supply of Gun-powder, purchased at a ruinous expence in foreign countries. That this is not a fallacious representation or a deceitful hope, held out to the people, will appear from this consideration, that five pounds of Salt-petre, which may be made in as many days, produced from 20,000 families, would afford a stock of Gun-powder for a large army, leaving a sufficiency for cannon both for forts and batteries, and for the field. The Committee, in this publication, hold our every motive to invite their countrymen to this undertaking, that can possibly engage the human heart. There is the love of the public good, which they doubt not, fully possesses almost every breast. There is interest, should these strong incentives alone not be of sufficient energy to overcome the reluctance natural to some to engage in any work that has the appearance of novelty. There is the love of pleasure, which among sportsmen, can be gratified at present in no other way, but by a criminal. ​ [ 33 ] minal breach of a regulation dictated by self-evident necessity.
The Committee from these considerations, cannot entertain a doubt of extracting immediately from this resource, the richest treasures; to a free people, more valuable than the mines of Peru or Mexico to their possessors, it is affording them a certain means of defending their natural and chartered rights, and handing them down unimpaired a fair inheritance to their children and children's children to the latest posterity.
By Order of the Committee of Safety,
WILLIAM GOVETT, Clerk.