The following is the specification of a patent granted to Alfred J. Watts, of Utica, N.Y., on the 18th, of last April, and as it F I very important invention, we publish it retire. The nature of the invention consists in dissolving gold (which has been jireviously purified by any of the well I. uown methods in mercury, and after treatment by heat or otherwise, dissolving out the mercury by nitric acid, and then subjecting the new conditioned Tint as yet niit'mished gold to the action of a particuliu lieat, whereby it is rendered cohe-rent,solt and malleable, and admirably fitted for filling teeth. I take gold, either pure or alloyed, dissolve it in nitro-muriatic acid, and precipitate by proto-sulphate of iron; I wash the precipitated gold with diluted hydrochloric acid, to remove any per-oxyde of iron or other impurities: edulcorate with hot water, and dry it thoroughly. I now amalgamate it with from 4 to 12 times, its own weight of mercury, triturate it thoroughly and set it aside and allow it to stand from about 1 to 24 hours, according to circumstances. If I wish the gold to be in a highly crystalline condition, I make a pretty fluid amalgam, and after thorough triturition, put It hi a flat K-itiormrd vo--cj, "aiil l;vt'. II gradually till it is quite hot and painful to the touch (about from 180 to 240 Fah.) I keep it at this heat for a few minutes, and then allowing it to cool gradually, let it remain some hours, as before stated, to condition itself. I then pour over it pure nitric acid diluted with about its own bulk of water. I apply heat very gently at first, and as the action progresses I increase it. Towards the end of the operation, when the mercury appears to be all dissolved out, and the gold presents the appearance of a mass of crystals, or semi-crystals, or sponge, T pour off the acid solution of mercury and pour pure undiluted nitric acid into the vessel containing the gold and then apply heat. This dissolves out the mercury, or any other metals which may have escaped the action of the diluted acid, and also any of the salts of mercury remaining in the pores of the gold, and after washing with hot water and drying, the gold is left in a perfectly pure condition. In this state, however, it is very friable, and so easily broken, that it will not bear the slightest handling without breaking it up into fine powder; it must be very tenderly treated while getting it into position for the next process. When this is thoroughly dry, I raise the heat to a cherry red, or to a heat just short of the melting point of gold. This is a particular part of the process and requires care and skill. The heat must be raised to just that point which will partially liquify without actually melting the gold and when properly managed, the gold will be left in the condition of a soft malleable and extremely ductile mass oi crystals, which will be either close and spongy, or loose, and in a mass of brilliant needle-shaped crystals, radiating from centres, and crossing each other in every direction, and will bear handling without crumbling to pieces, and upon pressure will readily weld into a solid mass eminently fitting it for the purpose set forth. I take gold, either pure or alloyed (I prefer pure), roll it out into thin strips, heat them to a red heat, cut them up into small pieces put them in a glass, a matrass, or any convenient vessel to answer the purpose hereafter mentioned. I pour over it from 6 to 10 times its weight of mercury, and apply heat just short of the boiling point of mercury. The vessel is f closed and kept close at the top, so as to con-. dense any mercurial vapors, and the gold dissolves. I then pour it into a glass mortar and b afterwards add more mercury, according to circumstances, and triturate it thoroughly till , cold, when it is poured into a flat bottom glass l vessel convenient for applying nitric acid ; I , then, according to the condition I wish to ! bring the gold into, either apply heat and set ! it aside to cool gradually or quickly, as requi-, red, or set it aside without applying heat, to remain an hour, or a day, according to circumstances, and then apply acid, as in the other case before mentioned. The herein mentioned processes of prepa-; ring and crystallizing gold, are claimed for preparing gold to fill teeth.
This article was originally published with the title "Preparing and Crystalizing Gold" in Scientific American 8, 46, 366 (July 1853)