288 AGRICULTURAL EXPERIMENT STATION. [Jan. 



as wool, leather, etc., can be converted into sulphate of 

 ammonia. He suggests dissolving the material in a ten per 

 cent, solution of caustic soda in the cold. The substances 

 will be partly dissolved, or their structure more or less 

 destroyed. The jelly-like mass is then mixed with caustic 

 lime till it becomes of a doughy consistency. It is then 

 brought into iron retorts, and heated at first at as low a tem- 

 perature as possible, in order to prevent the dissociation of 

 the ammonia, which is caught in sulphuric acid. After the 

 gas has been nearly driven off, the retorts are subjected to 

 red heat. At the end of the operation a white powdery 

 substance is left behind, consisting of carbonate of soda and 

 caustic lime. By cooking this substance with water, caustic 

 soda is formed and can be again utilized. By this method 

 all the nitrogen is obtained. The resulting sulphate of am- 

 monia is somewhat colored. 



For utilizing leather Riimpler * suggests the following 

 method : in lead or iron jacketed kettles, sulphuric acid of 

 50° B. is heated very hot, and leather stirred in till a dark- 

 brown fluid is obtained. This fluid is then used to dis- 

 solve the phosphate of lime. He remarks that "the nitro- 

 gen is saved, and without doubt is much more available 

 from the fact that the tannin is destroyed." 



Erhardt f suggests that such refuse material be slowly 

 burned in closed ovens, and the gas collected in moist muck 

 till the latter becomes saturated. This muck mixed with 

 superphosphate gave, he says, a quick-acting manure. 



Deherain | says that this leather refuse can be dissolved in 

 sulphuric acid, and the excess of acid neutralized with phos- 

 phate of lime. In this way he claims a very active fertilizer 

 can be obtained at a low cost. 



The writer understands that this latter method has been in 

 quite general use for many years by European manufacturers. 

 Not only has leather been thus treated, but also a great 

 variety of nitro2:en-containino: refuse materials. American 

 manufacturers also subject various waste materials to the 

 action of sulphuric acid, in order to render them more quickly 

 available. 



* Kaiifliche Dongestoffe. H. Riimpler, 1875 (Thaer Bibliothek). 

 t Jahresbericht Agric. Chera., 1880, 337. 

 i Deherain, Chimie Agricole [1892] , 624. 



