342 



On Chemical Tests, 



[Oct. 



add the test, tan, till the whole of the gelatine be precipitated, but not 

 in excess ; the flocculent precipitate that occurs is a mixture of tan 

 and gelatine, which if weighed and multiplied by 0 6 will very nearly 

 give the true weight of the gelatine. 



119. TELLURIUM. In a riitro-muriatic solution of this metal, wa- 

 ter produces a white precipitate, which fuses at a white heat and sub- 

 limes. Tellurium is precipitated in a metallic state by sulphurous acid; 

 by sulphate of ammonia; by iron, and by zinc. Tincture of galls pro- 

 duces a yellow flaky precipitate, and solutions of potash and soda white 

 precipitates soluble in excess of the precipitant, see table of re-agents. 



o. The oxide of tellurium forms salts with acids and alkalies : com- 

 bines with hydrogen yielding a colourless gas absorbable by water, and 

 forming a claret coloured solution, with an odour like sulphuretted hy- 

 drogen. 



120. THORINA after ignition is insoluble in all acids except hot 

 sulphuric acid diluted with an equal weight of water. It is precipitat- 

 ed white by ferrocyanate of potash, phosphate of soda, hydrosulphuret 

 of ammonia, and by oxalic acid. It forms a colourless glass with borax, 

 before the blow-pipe. 



a. Solutions of thorina may be distinguished from alkalies, and from 

 barytes, strontian, and lime, by giving a gelatinous precipitate with am- 

 monia: from magnesia by its action with ammonia : and by hydrosul- 

 phuret of ammonia, which produces no precipitate with magnesia, but 

 in neutral solutions of thorina it precipitates hydrate of thorina; and 

 from solutions of alumina and glucina, by producing with a solution of 

 potash, a precipitate which does not redissolve in an excess of the preci- 

 pitant. 



121. TIN is detected by muriate of gold, see 60. Muriate of platina 

 produces in solutions of tin an orange coloured precipitate ; ferrocyanate 

 of potash, a w 7 hite precipitate ; perchloride of mercury black, with pro- 

 toxide salts, but white with the peroxide: and a plate or slip of lead, 

 metallic tin. See table of re-agents 



a. A slip of tin immersed in a muriatic solution of gold becomes co- 

 vered with a purple powder which gradually diffuses throughout the 

 fluid, and imparts to it the colour of red wine, but the colouring matter 

 soon precipitates. * 



b. A bar of metallic zinc precipitates tin from the solutions of its 

 protosalts in the metallic state in the form of small greyish-white span- 



