HYPONITRITES. 317 



The following work, tlierefore, was directed to the examination 

 of sodium and ammonium hyponitrites and, incidentally, to the 

 examination of the method of preparation of hyponitrite of silver, 

 which is the starting-point in the pre])aration of other hyponitrites. 



The yield of hyponitrite by the different methods of preparation 

 varies from an amount which is described as bad and variable to a 

 disputed maximum of 15 per cent, of the " theoretical quantity," 

 and it was therefore considered advisable to ascertain, in the first 

 place, if it were possible to readily improve this yield. 



Fyroyenous Methods of Formation. — As nitrite is readily 

 obtained from nitrate by heating, as well as by reduction in 

 solution, it wovdd seem, at first sight, that hyponitrite would most 

 easily be obtained by heating nitrates, either alone or in contact 

 with some reducing agent. Support is given to this view by 

 Menke, Avho states that he obtained alkaline hyponitrites by 

 heating sodium or potassium nitrate with iron filings in the 

 presence or absence of sodium carbonate, and a considerable 

 number of experiments were made, but without result, to test this 

 method of preparation. It may be mentioned that Divers and 

 Zorn have also been unsuccessful in repeating Menke' s experi- 

 ments. Moreover, there are several important reasons for thinking 

 that Menke himself did not obtain hyponitrite, for (1) Menke 

 states that his sodium salt gives a turquoise blue precipitate with 

 eoi^per sulphate, whereas Kolotoff has shown (C.S.J., Mar., 1893) 

 that copper hyponitrite is yellow ; (2) Menke boiled his product 

 of reduction with water to extract the hyponitrite. As a matter of 

 fact, sodium hyponitrite is very meltable under these conditions ; 

 (3) Menke heated his silver salt with ethyl iodide in a sealed tube 

 and fractionated the product. Zorn has shown that this could not 

 be carried out with real hyponitrite, as ethyl hyponitrite is violently 

 explosive. 



After trying unsuccessfully to obtain hyponitrite by reducing 

 nitrate with aluminium, and also by reducing potassium and barium 

 nitrates with barium amalgam, it was decided to adopt the 

 original method of Divers, tha* is, reduction of nitrate with 

 sodivini amalgam, neutralisation of the resulting alkaline liquid with 

 acetic acid, and precipitation of the silver hyponitrite with silver 

 nitrate. 



The. Divers' Methods of Preparation. — Zorn states that the best 

 amalgam for the purpose contains one part of sodium to thirty 

 of mercury, but, as the product is still very small, a series of 

 experiments was made with different strengths of amalgam, and 

 these results showed that the largest yield was obtained with a 

 very dilute amalgam and the smallest with a very strong one. 

 Intermediate amalgams gave a secondary maximum. A similar 

 series of experiments was conducted at 4°, and these show that 

 the yield is much increased when the reduction is carried on at a 

 Ibw temperature. 



