M. Schonbein on the Formation of Nitrite of Ammonia. 521 



He adduces the following experiments in support of his view. 

 An open platinum crucible is heated so strongly that a drop 

 of water let fall upon it evaporates at once without showing 

 Leidenfrost's phenomenon. This process is repeated with the 

 purest water, waiting each time till the last drop is evaporated. 

 If now a cold flask is held over the vapour thus formed until a 

 few grammes of water are collected, it will be found that this 

 liquid has the power, when acidulated, of rendering iodides and 

 starch blue. Schonbein states that this experiment is not always 

 successful, and ascribes this to the difficulty of exactly hitting 

 that temperature at which the substance is formed and not 

 destroyed. 



To prepare large quantities of such nitrite solution, a copper 

 retort is fitted, such as is used for the distillation of water. The 

 retort is first heated, so that water projected upon it immediately 

 evaporates; this process is repeated as often as the previous 

 quantity is evaporated, and, the retort being connected by its 

 head with the condenser, a quantity of water is collected which 

 has all the properties of a solution of nitrite of ammonia. 



Schonbein holds that nitrite of ammonia is always formed, 

 provided that all the conditions for its formation are fulfilled, 

 which are the presence of heat, water, and atmospheric air. 

 Saussure found that ammonia as well as nitrous acid were 

 formed when hydrogen burnt in air, and Schonbein had shown 

 (in 1845) that in the combustion of hydrocarbons and fats an 

 oxidizing substance was produced which at that time he was not 

 able to identify with nitrous acid. 



He has found that nitrite is produced whenever charcoal is 

 burnt. On the top of a small charcoal furnace a tightly fitting 

 lid was placed ; in the side of the furnace, about 2 inches below 

 the lid, an iron tube an inch in diameter and about 4 inches long 

 was placed, through which the heated air made its exit and passed 

 into a receiver containing about 4 ounces of water. Not more 

 than a pound of charcoal was burnt at a time, and only a suffi- 

 cient quantity added to keep up the combustion, which must not 

 be too violent, as otherwise a quantity of the product formed is 

 again decomposed. 



In the combustion of coal, nitrite is produced; but as the 

 coal always contains sulphur, it produces sulphurous acid, which 

 decomposes the nitrous acid with the formation of sulphuric acid, 

 so that very little nitrite is perceptible. Schonbein suspended a 

 wet sponge in the chimney of a coal-fire for half a day, and found 

 that the water squeezed from it contained distinct quantities of 

 sulphate of ammonia, but also some nitrite. 



It is not difficult to understand that in the combustion of 

 certain substances no nitrite is perceived, though it may have 



