FOOTNOTES:

[9] Lead may be granulated by heating it to a little above the melting point, pouring it into a closed wooden box, and rapidly agitating it as it solidifies.

[10] A rod of iron placed in the crucible with the a.s.says will decompose any regulus that may be formed.

[11] With b.u.t.tons poor in silver the lowering of the temperature at this stage is not a matter of importance.

[12] 100 grams of the lead, or of its oxide, will contain from 1.5 to 2.5 milligrams.

[13] Still the precautions of having cupels well made from bone ash in fine powder, and of working the cupellation at as low a temperature as possible are very proper ones, provided they are not carried to an absurd excess.

[14] Be careful to remove the crucible before taking the bottle out of the basin of water; if this is not done the chloride may be washed out of it.

[15] 1 c.c. of this dilute acid will precipitate 8 or 9 milligrams of silver.

[16] Chlorides interfere not merely by removing silver as insoluble silver chloride, but also by making it difficult to get a good finishing point, owing to the silver chloride removing the colour from the reddened solution.

[17] These results were obtained when using ammonium sulphocyanate, and cannot be explained by the presence of such impurities as chlorides, &c.

[18] Multiply the _standard_ by 1000, and dilute 100 c.c. of the standard solution to the resulting number of c.c. Thus, with a solution of a standard .495, dilute 100 c.c. to 495 c.c., using, of course, distilled water.

[19] HNa_{2}AsO_{4} + 3AgNO_{3} = Ag_{3}AsO_{4} + HNO_{3} + 2NaNO_{3}.

[20] SiO_{2} + Na_{2}CO_{3} = CO_{2} + Na_{2}SiO_{3} SiO_{2} + 2NaHCO_{3} = 2CO_{2} + Na_{2}SiO_{3} + H_{2}O.

[21] PbO + SiO_{2} = PbSiO_{3}

[22] Here and elsewhere in this article when a flux is spoken of as soda the bicarbonate is meant.

[23] See the description of the process commencing on p. 98 and the explanatory remarks on p. 110.

[24] Percy, _Metallurgy of Silver and Gold_, p. 258.

[25] "Limits of Accuracy attained in Gold-bullion a.s.say," _Trans. Chem.

Soc._, 1893.

[26] "a.s.saying and Hall-marking at the Chester a.s.say Office." W.F. Lowe.

_Journ. Soc. Chem. Industry_, Sept. 1889.

[27] Fine or pure gold is 24 carat. Nine carat gold therefore contains 9 parts of gold in 24 of the alloy; eighteen carat gold contains 18 parts of gold in 24; and so on.

[28] The mouth of the flask must not have a rim around it.

[29] See "a.s.saying and Hall-marking at the Chester a.s.say Office," by W.F. Lowe. _Journ. Soc. Chem. Industry_, Sept. 1889.

[30] Percy, _Metallurgy of Silver and Gold_, p. 263.

[31] See also "The a.s.saying of Gold Bullion," by C. Whitehead and T.

Ulke. _Eng. and Mining Journal_, New York, Feb. 12, 1898.

[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] Heyc.o.c.k 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 Inst.i.tute_, 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 quant.i.ty 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--BIs.m.u.tH--ANTIMONY.

COPPER.