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 XIII. Intelligence and Miscellaneous Articles. 



ON THE FORMATION OF HYPONITRITE OF SILVER. 



MPERSOZ found that by heating nitrate of silver so as to 

 • expel a portion of its oxygen, the residue, when treated with 

 sufficient water at 40° F. to dissolve the nitrate remaining undecom- 

 posed, yielded a gray residue, which was insoluble in cold but solu- 

 ble in hot water ; and the solution on cooling deposited long acicu- 

 lar crystals, possessing all the properties of hyponitrite of silver. 



Being satisfied from this experiment that hyponitrite of silver re- 

 sults from the decomposition of the nitrate by heat, it appeared 

 natural to conclude, that by cautiously heating the nitrate it might 

 be totally converted into hyponitrite. All attempts to produce this 

 effect were however unsuccessful. It was found not only to be im- 

 possible so to convert the whole of a given portion of the salt, but even 

 to increase the quantity of hyponitrite beyond a certain proportion, 

 because it decomposes much sooner than the nitrate. Its formation 

 and existence, under the circumstances described, can be explained 

 only by supposing that it acquires, by the presence of the nitrate of 

 silver, a degree of stability which it does not possess when isolated. 

 If this be the case, the nitrate of silver ought to be capable of being 

 replaced by a more stable nitrate, and in point of fact this actually 

 occurs; for by fusing and calcining a mixture of equal parts of ni- 

 trate of silver and nitrate of potash, a much larger quantity of hypo- 

 nitrite is obtained and less silver is set free. This process of pre- 

 paring the hyponitrite appears to be the most certain. The fine 

 crystalline needles obtained by dissolving the salt in hot water, have 

 a fatty and cotton-like appearance, and seem colourless in the liquid 

 in which they form; whereas when taken from it, they always pos- 

 sess a greenish tint of greater or less intensity. When heated in a 

 small glass tube by a spirit-lamp, these crystals are immediately 

 decomposed into nitrous vapour and silver, which retains the form of 

 the hyponitrite ; when treated with concentrated sulphuric acid, they 

 decompose instantly with the production of nitrous vapour and sul- 

 phate of silver. 



One hundred parts of the crystallized hyponitrite yielded 69'87 of 

 silver, showing that it is composed of — 



One equivalent of hyponitrous acid 38 



One equivalent of oxide of silver 116 



154 

 This result agrees with the previous determination of Mitscherlich, 

 who found the salt to yield 70082 per cent, of silver. 

 From the above-mentioned facts M. Persoz concludes, — 



1 . That nitrate of silver behaves up to a certain point similarly to 

 the alkaline nitrates, being, like them, partially converted by heat into 

 hyponitrite. 



2. That this hyponitrite is formed only in the presence of nitrates 

 which give it stability, such as the nitrates of silver, potash, soda and 

 other alkaline nitrates. — Ann. de Ch. et de Phys., Mai 1848. 



