50 HYPONITRITES ; PEOPEETIES AND rPEPARATIOX P.Y 



tioiisly filtered, if necessary, into some sodium carbonate solution 

 or, if not, is at once made alkaline with sodium carbonate. 

 The reprecipitated salt is then treated with sulphuric acid and 

 washed, all just as was done with the original precipitate. 

 Even after reprecipitation, the silver hyponitrite coming from 

 34.5 grams sodium nitrite will weigh about 11 grams. 



The way of preparing silver hyponitrite just given differs 

 from that contained in my first paper in not neutralising the 

 sodium hydroxide with acetic acid, in taking silver sulphate 

 instead of nitrate, sulphuric acid in place of nitric acid, and 

 sodium carbonate in place of ammonia, and in some minor 

 details. The use of sulphuric acid is not new, that acid having 

 been first used by van der Plaats, but the motive for the change is 

 new^ and has been already given (p. 48). Cold dilute sulphuric 

 acid is not in the least less active than nitric acid in decomposing 

 silver hyponitrite ; in fact, unless very dilute, it is more active 

 in consequence of silver sulj^hate crystallising out. Sodium car- 

 bonate (used by Haga and me in 1884, J. C'h. Soc, 45, 78) is 

 to be preferred to ammonia for precipitating the salt as being 

 more sensitive, and because the last trace of ammonia is dif- 

 ficult to wash out of the silver salt (as Hantzsch and Kauf- 

 mann have found to their cost — see p. 64). It is easy to 

 ensure absence of all silver carbonate along with complete 

 precipitation of the hyponitrite, because of the solubility of 

 the carbonate in the carbon dioxide always present in the 

 solution. 



Properties of silver hyponitrite. 



Silver hyponitrite is bright yellow, and when pale in colour 

 it generally contains a trace of ammonia or loosely combined 



