Artificial tourmalines



Dissolve 50 grains of disulphide of quinine in 2 fl. oz. of acetic acid, and 2 oz. of proof-spirit warmed to 130 Fahr., in a very wide-mouthed flask or glass beaker; then slowly add 50 drops of a mixture of 40 grs. of iodine in 1 oz. of rectified spirits; agitate the mixture, and then set it carefully aside for 6 hours, in an apartment maintained at a temperature of about 50 Fahr. The utmost care must be taken to avoid any motion of the vessel; indeed, all accidental vibrations should be guarded against by suspending the vessel by a string, or by allowing it to rest on a mass of cotton and wool. If, in 6 hours, the large laminae of the salt have not formed, warm the fluid with a spirit lamp, and when it has become clear, add a few drops of the solution of iodine in spirit. The large laminae form on the top of the fluid, and should be removed carefully by gliding under one of them a circular piece of thin glass. The specimen should be drained by resting the edge of the glass on a piece of bibulous paper, but it must not be touched on account of its extreme fragility; if any small crystals adhere to its surface, they must be washed off by pouring over it a few drops of watery solution of iodine. When dry the specimen should be placed for a few minutes under a bell-glass by the side of a watch-glass, containing a few drops of tincture of iodine; and, lastly, very little fluid Canada balsam should be dropped on it, and a thin glass cover applied without heat. Specimens may thus be obtained of extreme thinness, and 1/2 an inch in diameter, or even larger, possessing scarcely the slightest color, and yet completely polarizing transmitted light.





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