Introduction to the study of inorganic chemistry / by William Allen Miller.

  • Miller, William Allen, 1817-1870.
Date:
1871
Catalogue details

Licence: Public Domain Mark

Credit: Introduction to the study of inorganic chemistry / by William Allen Miller. Source: Wellcome Collection.

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    Gold fuses at about i ioo° C. It is scarcely volatile in the furnace, but in the intense heat of the oxyhydrogen jet it may be dissipated in purple vapours. Sulphuric acid does not attack it; neither does the nitric or the hydrochloric acid separately, but a mixture of the two liberates chlorine, and this gradually dissolves it, forming a yellow solution. Exp. 262.—Place a little gold leaf in two test-tubes; to one add nitric, to the other hydrochloric acid. Even when heated with the acid the gold leaf remains unaffected. Pour the con- tents of one tube into the other : the gold will disappear with effervescence. Evaporate this solution in a small porcelain capsule till the acid is nearly all driven off; auric chloride will be left. Exp. 263.—Dilute the solution with 3 or 4 c. c. of water. To a portion of this liquid add a solution of ferrous sulphate: a Ijrown precipitate of finely divided reduced gold is obtained, and ferric chloride is formed— 6FeS04 4- cAuClj = 2(Fe,3S04) -1- FejClg -1- 2A11. This is a common mode of separating gold from its solutions. Add to another portion of the auric chloride a solution of sul- phurous acid : on warming the mixture gold will be precipitated—■ 2A11CI3 + 3H,0 + 3HjSO. = 6HC1 -t- 3HJSO4 + 2Au. A solution of oxalic acid will have a similar effect— 2AUCI3 + 3HAO4 = 2Au + 6HC1 -t- 6CO„ carbonic acid being produced. All these liquids look purple when viewed by holding them between the eye and the light, owing to the trans- parency of the finely divided gold. Gold in its pure state is too soft to be used for the inir- poses of coin or plate. It is hardened by alloying it with about a tenth ora twelfth of its weight of copper. Gold is usually triad in combination ; it however forms two oxides (.‘\U;0 and AU2O3), but they are seldom prepared. 'Fhc tri- chloride (AuCl3), obtained by dissolving gold in a mixture of nitric and hydrochloric acids, as above directed, is the most important com])Ound of the metal. When heated gradually