330 METALS AND THEIR COMBINATIONS. 



heated moderately upon charcoal before the blowpipe, forms a scar- 

 let-red incrustation of bismuthyl iodide, BiOI. 



6. Apply the reduction test on charcoal (see directions in test 3 

 for sulphuric acid) to any dry bismuth compound. A hard, brittle bead 

 of metallic bismuth is produced, which, if dissolved in a little con-, 

 centrated hydrochloric acid, aided by a few drops of nitric acid, and 

 the solution then be strongly diluted with water, gives a dense white 

 precipitate of bismuth subchloride, 



BiCL, + H 2 = BiOCl + 2HC1. 



Tests 1, 5, and 6 together are sufficient to identify a bismuth com- 

 pound. The insoluble or sub-salts are the most stable, and can be dis- 

 solved by acids, forming the normal salts. The latter cannot exist 

 in aqueous solution, except in the presence of an acid. The decomposi- 

 tion of normal salts of bismuth by water into insoluble sub-salts is the 

 most characteristic property of bismuth. One other metal resembles 

 it in this respect, namely, antimony, but its sulphide has an orange 

 color. 



The most readily obtained sub-salt of bismuth is the subchloride, 

 BiOCl . If no precipitate occurs when diluting the nitrate solution 

 (because of too much acidity), addition of solution of ammonium or 

 sodium chloride produces a precipitate of the subchloride imme- 

 diately. 



31. SILVER MERCURY. 



Silver, Ag = 107.12 (Argentum). This metal is found sometimes 

 in the metallic state, but generally as a sulphide, which is nearly 

 always in combination with large quantities of lead sulphide, such 

 ore being known as argentiferous galena. The lead manufactured 

 from this ore contains the silver, and is separated from it by roasting 

 the alloy in a current of air, whereby lead is oxidized and converted 

 into litharge, while pure silver is left. 



QUESTIONS. What are the properties of lead, and from what ore is it ob- 

 tained? What is litharge, and how does it differ from red lead? Give the 

 composition of nitrate, carbonate, and iodide of lead; how are they made? 

 State the analytical reactions for lead. How is copper found in nature ? How 

 many oxides of copper are known ; what is their composition, and under what 

 conditions are they formed? What is "blue vitriol"; how is it made, and 

 what are its properties? How does ammonium hydroxide act on cupric solu- 

 tions? Mention tests for copper. What is the composition of subnitrate and 

 subcarbonate of bismuth ; how are they made from metallic bismuth, and what 

 explanation is given in regard to their constitution ? 



