62 M. Stahlschmidt on the Reducing- Action of Zinc. 



tate produced by molybdate of ammonia. According to the ex- 

 periments of the author, this precipitate contains three atoms of 

 ammonia for one of phosphoric acid ; and therefore 42 parts by 

 weight of nitrogen correspond to 71 parts by weight of phos- 

 phoric acid. 



Stahlschmidt obtained the following as the results of some 

 experiments on the reducing-action of zinc*. In the presence 

 of a soluble alkali, finely divided zinc reduces nitrates almost 

 immediately into nitrites ; so that this method may be conve- 

 niently used for the preparation of the latter. Zinc-dust can be 

 had at almost every zincworks (it consists of zinc 39*99, lead 

 2*47, cadmium 4*09, oxide of zinc 49" 76, and carbonate of zinc 

 3*29), and may be advantageously used for these experiments 

 after having been washed with acids and water. 



If to a saturated solution of nitrate of potash zinc-powder be 

 added, and the mixture allowed to stand several days, nitrite of 

 potash and oxide of zinc are formed, with a small quantity of free 

 potash. If the temperature be raised to 60°, oxide of zinc, free 

 ammonia, and potash are formed, along with a small quantity of 

 nitrite of potash, while nitrogen is liberated. On boiling the 

 liquid, oxide of zinc, potash, and ammonia are formed, scarcely 

 any nitrite of potash, and much nitrogen. Nitrite of potash is 

 obtained in large quantities on mixing a solution of nitre satu- 

 rated at 30°-40° with one-tenth the volume of ammonia, and 

 adding zinc-powder ; the violence of the reaction requires to be 

 moderated by cooling. The decomposition of the nitre can be 

 recognized by the fact that the solution freed from ammonia and 

 oxide of zinc gives no crystalline precipitate on the addition of 

 four times the volume of alcohol. The solution is freed from am- 

 monia by boiling, the oxide of zinc filtered off, the dissolved zinc 

 and cadmium precipitated by carbonate of potash, the excess of 

 acid removed by dilute nitric acid, and the nitre got rid of by 

 crystallization. If a saturated solution of nitre is mixed with 

 excess of nitre, ammonia, potash, and much zinc, the liquid 

 begins to boil, and the nitre is decomposed with the formation 

 of potash, nitrogen, and ammonia. The same action is exerted 

 by sodium-amalgam. 



Stahlschmidt points out the reducing-action of this powdered 

 zinc in several other cases. 



* Poggendorff's Annalen, July 1866. 



