io8 THE PROSPECTOR'S HANDBOOK. 



tion. If a precipitate is formed it may, if black, show the 

 presence of mercury, lead, bismuth, platinum, tin, gold, and 

 copper ; if yellow, of tin, antimony, arsenic, or cadmium ; 

 but should no precipitate be formed, the addition of other 

 reagents has to be made to determine the presence of iron, 

 zinc, manganese, copper, nickel, and cobalt, &c.* 



The prospector will, however, find that usually his best 

 plan is to take portions of the original solution, and to test 

 them, one at a time, as follows : 



To separate portions of the original add reagents as in 

 Table on the next page. The presence of antimony may 

 be noted by adding a little hydrochloric acid to the original 

 solution, and, introducing a piece of zinc a sooty black 

 precipitate will be the result. 



To test a mineral for gold, the specimen must be tho 

 roughly dissolved in aqua regia (4 parts hydrochloric and 

 1 nitric acid), then protochloride of tin added. The slight- 

 est trace of gold will cause the purple precipitate (called 

 purple of cassius) to be formed ; if a bright red solution 

 results, there is platinum present. If, instead of the proto- 

 chloride of tin, a solution of sulphate of iron (copperas) be 

 added, the gold would be precipitated as a brown powder. 



Though, generally, testing for a metal in a mineral is 

 most satisfactorily performed by means of the blowpipe, 

 there are cases in which there is great difficulty in obtaining 

 proper results; for instance, when several metallic com- 

 pounds are combined in the same specimen. Under such 

 or other circumstances, individual tests, by means of the 

 addition of reagents to the original solution, are most useful. 



Again, the action of an acid on a mineral frequently 

 enables the operator to determine whether the mineral is 

 a silicate, a carbonate, &c. if the former, sometimes by 

 gelatinization ; if the latter, by effervescence ; and the 

 evolution of nitrous acid vapours will suggest that copper, 

 copper pyrites, or some metalliferous substance, not an 

 oxide, may be present. 



* Analogous test by fusion : If, when a mineral be fused with 

 hyposulphite of soda, the mass is black, it denotes the presence of bis- 

 muth, cobalt, copper, gold, iron, lead, mercury, nickel, platinum, silver, 

 uranium ; white, zinc ; red, antimony ; green, chromium or manga- 

 nese ; brown, tin or molybdenum. 



