INTEODUCTION. xxv 



Iron. — The protoxide salts afford a greenish-white precipitate with potash 

 or soda, which becomes green in the first instance, and then yellow on 

 exposure. The peroxide salts, with the same tests, afford a brown precipitate 

 of hydrated peroxide of iron. 



Compounds of Copper are, for the most part, soluble in nitric acid. 

 Metallic iron, dipped in such a solution, becomes coated with a precipitate 

 of metallic copper. Compounds of copper in solution, on the addition of 

 potash or soda, yield a precipitate, which is blue at first, but turns black on 

 being boiled ; with ammonia they give a green precipitate, which is re- 

 dissolved in excess of ammonia, and becomes of a fine blue colour. 



Compounds of Lead, -when dissolved in nitric acid, give a black precipitate 

 with sulphuretted hydrogen (which is insoluble in excess), and a yellow 

 precipitate with iodide of potassium or chromate of potash. Neutral solu- 

 tions of lead precipitate metallic lead on metallic zinc. 



Compounds of Zinc. — The sulphates afford no precipitate with sulphuretted 

 hydrogen, but give a white precipitate with potash soluble in excess of that 

 reagent. Acetate of Zinc affords an abundant precipitate with sulphuretted 

 hydrogen. 



Compounds of Manganese. — The salts, when heated with potash or nitrate 

 of potash, afford manganate of potash, which gives a green solution in water, 

 and with dilute acids a rose tint, which is destroyed by sulphurous acid or 

 organic matters. The oxides give off chlorine when heated with muriatic 

 acid. 



' Compounds of Tin form chlorides when dissolved in muriatic acid, which 

 afford a purple colour with chloride of Gold; or if strong, a brown precipitate. 



Compounds of Silver. — When dissolved in nitric acid, the addition of a 

 chloride or muriatic acid throws down a dense white curdy precipitate of 

 chloride of silver, which turns black on exposure, and is soluble in ammonia. 

 A slip of copper dipped in a solution of silver becomes coated with a deposit 

 of metallic silver. 



Gold is not soluble in any of the acids singly, but is dissolved by a mix- 

 ture of nitric and muriatic acid (or aqua regia). The solution gives a purple 

 precipitate on the addition of protochloride of tin, and metallic gold with 

 protosulphate of Iron. 



Platinum is not dissolved either by nitric or muriatic acid, but is dissolved 

 in a mixture of the two. Muriate of ammonia throws down a yellow pre- 

 cipitate from such a solution, and the precipitate, heated in a platinum 

 crucible, yields metallic platinum in -the state of powder. 



Compounds of Mercury afford a white precipitate with muriatic acid. 

 Solutions of the protosalts give a black precipitate with potash, which is 

 insoluble in excess of that reagent; and a black insoluble precipitate with 

 sulphuretted hydrogen. A precipitate of metallic mercury is deposited on a 

 slip of copper when immersed in the above solutions, and is dissipated by 

 heat. 



The various members of the Quartz family, though one of the most abun- 

 dant in nature, and presenting a great diversity of colours, yet possess certain 

 characters in common which render them easily recognisable after a little 

 practice. The most important of these characters is the total absence of 

 cleavage, and the degree of hardness which is No. 7 in the table given at 



