SALTS OF SILVER. 673 



soda is fused at a red heat, till it is wholly converted into 

 nitrite by loss of oxygen ; the latter salt then begins to lose 

 nitrous acid, and a small portion of the salt dissolved in water 

 will be found to precipitate silver brown. The fusion is then 

 interrupted, the salt dissolved in boiling water, precipitated by 

 nitrate of silver, and filtered while still very hot. The nitrite of 

 silver, which requires 1 20 times its weight of water at 60" to 

 dissolve it, is precipitated as the solution cools. The other 

 nitrites are prepared by rubbing this salt in a mortar with 

 chlorides taken in equivalent quantities. It appears from 

 experiments of Proust that two sub nitrites of silver exist, one 

 soluble and the other insoluble. 



Acetate of silver, which is soluble in 100 times its weight of 

 cold water, is precipitated when acetate of copper is mixed with 

 a concentrated solution nitrate of silver. It crystallizes from 

 solution in boiling water in anhydrous needles. 



Oxalate of silver is an insoluble powder. A double oocalate 

 of potash and silver is formed by saturating binoxalate of potash 

 with carbonate of silver. It is very soluble, and forms 

 rhomboidal crystals, which are persistent in air. 



Peroxide of silver. A superior oxide of silver is deposited 

 upon the positive pole or zincoid of a voltaic battery in a weak 

 solution of nitrate of silver, in the form of needles of 3 or 4 

 lines in length, which are black and have a metallic lustre, while 

 metallic silver is, at the same time, deposited in crystals upon 

 the negative pole or chloroid. The former crystals are con- 

 verted by sulphuric acid into oxide of silver and oxygen, and 

 yield with hydrochloric acid, chloride of silver and chlorine. 



Silver may be readily alloyed with most metals. It combines 

 by fusion with iron, from which it cannot be separated by 

 cupellation. Native silver is always associated with gold ; the 

 two metals are found crystallized together in all proportions in 

 the same cubic or octohedral crystals. Gold may be detected 

 in a silver coin, by dissolving the latter in pure nitric acid, 

 when a small quantity of black powder remains, which after 

 being washed with water, will be found to dissolve in nitro- 

 muriatic acid, giving a yellow solution in which protochloride of 

 tin produces a precipitate of the purple powder of Cassius. 

 Pure silver, being very soft, is always alloyed in coin and plate, 

 with a certain quantity of copper, to make it harder. The 



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