252 CHEMISTRY. 



and drying it, the crystalline arrangement can be very 

 plainly seen. Ware which has been treated in this way is 

 called moire metallique. If a bar of tin be bent it gives a 

 peculiar sound, which is owing to the friction of the mi- 

 nute crystals of the metal against each other. This sound 

 has been fancifully called "the cry of tin." There are 

 three oxides of tin, one of Avhich, the dioxide, SnO 2 , is its 

 common one. The most famous and most abundant tin- 

 mines are those of Cornwall, in England. It is supposed 

 that they were worked long before the Christian era. 



354. "Tin Salts." By dissolving tin in hydrochloric acid, 

 stannotis chloride, SnCl 2 , separates from the solution in 

 needle-shaped crystals containing water. This forms the 

 "tin salts" so largely used by the calico-printer and dyer 

 as a mordant. Stannic chloride, SnCl 4 , is a fuming, color- 

 less, heavy liquid. 



355. Sulphides of Tin. There are two sulphides of tin, a mono- and 

 a di-sulphide. Stockhardt tells us how to obtain them. To obtain the 

 first inclose 2 grammes of flowers of sulphur in a piece of tin-foil weigh- 

 ing 4 grammes, and introduce the package into a test-tube. On heating 

 the tube, half of the sulphur will burn up, and the other half will unite with 

 the tin with a lively glowing, forming a brownish-black mass, which is the 

 monosulphide. If you sprinkle the glass, while still hot, with water, it is 

 rendered friable, and is easily separated from the fused salt, which will be 

 found to weigh about 5 grammes. Pulverize this, and mix intimately with 

 the powder 1 gramme of sulphur and 2 of sal ammoniac. Put this into a 

 thin flask, and let it be heated in a sand-bath for an hour and a half. The 

 disulphide will be found in the bottom of the flask in a mass having a gold- 

 en lustre, and the sal ammoniac will appear in the upper part of the flask, 

 deposited there by sublimation. The latter is not altered at all in compo- 

 sition, but it in some way serves to give the disulphide its golden color. 

 The beautiful substance thus obtained has been called aurum musivum, or 

 mosaic gold, and it may be used for giving a gold-like coating to wood, 

 plaster of Paris, etc. 



