Chemical Science, itS 



mineral to the state of oxide bj' any organized matter. The same 

 circumstance renders it necessary to keep the substance from the 

 contact of such bodies, and it is in its best state when recently pre- 

 pared. — (J. D.) An?i. de VInduslrie, i. 309. 



23. Reduction of Oxide of Copper by Iron and JVater. — Mr. 

 J. Malin, a worker of copper and iron plate, has had occasion to 

 remark that iron chippin<^s, which have accidentally fallen into a 

 vessel of water in which copper-plates had been previously quenched 

 and scaled, became, after some time, covered with copper, so as to 

 have every appearance of metallic copper. This easy reduction, he 

 tliinks, may be useful to those who work in both metals. — Franklin 

 Journal. 



24. Separation of Silver and Copper.— 'The, amalgam obtained 

 at the silver works of Freyberg-, leaves, when decomposed by heat, 

 an alloy of silver, copper, and other metals; the latter used to be 

 separated from the silver by boiling and dissolving the whole in 

 strong sulphuric acid, and then precipitating the silver. Of late a 

 process altogether new has been introduced. The alloy is now 

 heated in a reverberatory furnace, exposed to air, so as to oxidize 

 the copper, and is afterwards put into cauldrons of lead, and heated 

 with dilute sulphuric acid, which dissolves the oxide of copper previ- 

 ously formed ; the operations of roasting and digesting are repeated 

 once or twice, and many precautions are requisite to obtain a good 

 result, but these being attended to, the process is much more econo- 

 mical than the ancient one. The silver is not so pure, retaining 

 about -j'y of copper; but this is of no consequence for ordinary uses. 

 '—Ann. des Mines^ iii. 15. 



25. Solubility of Sulphate of Lead. — Nitrate and acetate of am- 

 monia dissolve sulphate of lead, the latter in considerable propor- 

 tion, so as even to be useful in analysis for the separation of sul- 

 phate of lead from other insoluble sulphates. At the temperature of 

 55° Fahr., one part of sulphate of lead is dissolved by 969 parts of 

 a solution of nitrate of ammonia, of specific gravity 1.29 ; and by 

 only 47 parts of a solution of acetate of ammonia, of a sp. gr. 1.036. 

 The same quantity is dissolved by 172 parts of nitric acid, sp. gr. 

 1.144. The dissolving power of nitric acid does not appear to be 

 diminished by dilution ; the best precipitate in such a case is free 

 sulphuric acid, and not the sulphates of potash or soda. — Bischolri 

 Jahrb. dcr Chem. 1827. 



26. Use of Red Sulphuret of Arsenic^ or Realgar, in Dyeing. — M. 

 H. Labillardiere states, that many useful colours may be obtained 

 from this substance. The colours are compounds of the sulphuret 

 with oxide of lead, and may, according to M. Berzelius's explanation, 

 be qonsidered as salts, in which the sulphuret plays the part of an 



