[32] Consult Percy's _Metallurgy of Silver and Gold_, p. 172; A.C. Claudet, _Trans. Inst. Mining and Metallurgy_, vol. vi. p. 29; G.M. Roberts _Trans. Amer. Inst. Mining Engineers_, Buffalo Meeting, 1898; J. and H.S. Pattinson, _Journ. Soc. Chem. Industry_, vol. xi. p. 321. [33] Heycock and Neville, _Journ. Chem. Soc._, 1892, p. 907. [34] G.M. Roberts. [35] A.C. Claudet. [36] "The Sampling of Argentiferous and Auriferous Copper," by A.R. Ledoux. _Journ. Canadian Mining Institute_, 1899. [37] NaCNO + BaCl_{2} + NaHO + H_{2}O = NH_{3} + BaCO_{3} + 2 NaCl. [38] HCy + NaHO = NaCy + H_{2}O. [39] 2KCN + AgNO_{3} = KAg(CN)_{2} + KNO_{3}. [40] If it be desired to make a solution so that 100 c.c. shall be equivalent to 1 gram of sodium cyanide, then 18.085 grams of silver nitrate should be taken for each litre. [41] AgNO_{3} + KAgCy_{2} = 2 AgCy + KNO_{3}. [42] AgNO_{3} + KI = AgI + KNO_{3}. [43] See pp. 322, 323, and 324 for a description of the methods for measuring the quantity of acid or alkali. [44] KCN + HCl = KCl + HCN [45] Taking 16.0 grams of ore, each c.c. = 1 lb. of soda to the short ton. The corresponding figures for the long ton are 12.544 grams for lime and 17.92 grams for soda. [46] In which case each .01 gram of metal found equals 1 lb to the short ton of solution. [47] 100 c.c. of water dissolves 0.66 gram of the salt; it is almost insoluble in alcohol or in solutions of ammonic chloride. [48] According to Personne mercuric chloride is not volatilised from boiling solutions when alkaline chlorides are present. [49] The solution should contain about 0.25 gram of mercury, and a large excess of nitric acid must be avoided. CHAPTER X. COPPER--LEAD--THALLIUM--BISMUTH--ANTIMONY. COPPER. Copper occurs native in large quantities, especially in the Lake Superior district; in this state it is generally pure. More frequently it is found in combination. The ores of copper may be classed as oxides and sulphides. The most abundant oxidised ores are the carbonates, malachite and chessylite; the silicates, as also the red and black oxides, occur less abundantly. All these yield their copper in solution on boiling with hydrochloric acid. The sulphides are more abundant. Copper pyrites (or yellow ore), erubescite (or purple ore), and chalcocite (or grey ore) are the most important. Iron pyrites generally carries copper and is frequently associated with the above-mentioned minerals. These are all attacked by nitric acid. They nearly all contain a small quantity of organic matter, and frequently considerable quantities of lead, zinc, silver, gold, arsenic, bismuth, &c.