SALTS OF SILVER. 



crystallizes in the same form as hyposulphate of soda. It crys- 

 tallizes also with ammonia, as Ag O, S 2 O 5 + 2NH 3 . 



Hyposulphite of silver, AgO, S 2 O 2 . Hyposulphurous acid 

 appears to have a greater affinity for oxide of silver than for any 

 other base. Oxide of silver decomposes the alkaline hyposul- 

 phites, and liberates one half of their alkali, and a double hypo- 

 sulphite of the alkali and silver is formed. These double 

 salts are best prepared by adding chloride of silver in small por- 

 tions to the soluble hyposulphite of potash, soda, ammonia, or 

 lime in the cold, till the liquid is saturated; after which, the 

 solution is filtered, and mixed with a large quantity of alcohol, 

 which precipitates the double salt ; those of potash and soda are 

 crystallizable. Herschel considers the double salts obtained in 

 this manner, as probably containing one eq. of hyposulphite of 

 silver, to two eq. of the other hyposulphite. The solution of 

 one of these double salts dissolves more oxide of silver, and 

 forms a double salt, which is believed to contain single equiva- 

 lents of the salts, and precipitates as a white crystalline, pul- 

 verulent bulky mass. The second compound is sparingly 

 soluble in water, but dissolves in ammonia, and communicates 

 to the liquor an intensely sweet taste. 



The hyposulphite of silver itself, is an insoluble substance ; it 

 is prone to undergo decomposition, changing spontaneously into 

 sulphate and sulphuret of silver. When to a dilute solution of 

 nitrate of silver, a dilute solution of hyposulphite of soda is 

 added by small quantities, a white precipitate of hyposulphite 

 of silver falls, which dissolves again in a few seconds, from the 

 formation of the soluble double hyposulphite of soda and silver. 

 When enough of hyposulphite of soda has been gradually added, 

 to render the precipitate permanent, without, however, decom- 

 posing the whole silver salt, a flocculent mass is obtained of a 

 dull grey colour, which is permanent. The liquor contains 

 much hyposulphite of silver, and has an intensely sweet taste, 

 not at all metallic; the silver is not precipitated from it by 

 hydrochloric acid or the chlorides. An excess of hyposulphite of 

 soda destroys the precipitated hyposulphite of silver, converting 

 it into sulphuret of silver. 



Nitrate of silver, AgO,NO 5 , 2128.6 or 170.57- When a 

 piece of pure silver is suspended in nitric acid, it dissolves for 

 a time without effervescence at a low temperature, nitrous acid 

 being produced, which colours the liquid blue ; but if heat be 



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