The Third Part of the Prosperity of Germany

drop by drop the lye of wood, until the boiling of the lye poured over the dissolved stone ceases, and when the noise has settled, you will see some salt produced from these mixed things, namely from the dissolved stone and the lye. To this salt, pour common water in the quantity that suffices for the dissolution of the salt in a warm place. Once the solution is made, let the liquor be filtered or strained through a thin cloth, so that the stone not yet dissolved and the dregs remain in the filter or cloth. Let the filtered liquor be coagulated into salt by evaporation in a copper vessel, the weight of which must be investigated. But so that it may be exactly certain to us how much saltpeter was in that half-ounce of stone, we must proceed further in this way.

Take Aqua fortis nitric acid in the same quantity that you just used for the solution of the lime stone, and pour onto it the lye in the same quantity that you used for the precipitation of the dissolved stone, and precipitation will occur. Let the precipitate be coagulated into the substance of salt, and let the quantity of this salt also be explored by weight. As much as is now observed by weight to be lacking in this salt compared to the first to which the lime stone is present, that much saltpeter was in that half-ounce of lime stone. This proof is most certain, and in this way we can most easily find out how many pounds of saltpeter are contained in a hundredweight of stone. NB: For the proof to be most accurate, we are bound to use a smaller hundredweight, as it is more adapted and customary for the examination of metals.