1895.] PUBLIC DOCUMENT — No. 33. 297 



So far as the writer has been able to ascertain, Wagner 

 does not state the form of the leather used. 



Taking the price of nitrogen in nitrate of soda at 14.8 

 cents, a pound of nitrogen in stable manure would be worth 

 G.7 cents and in leather 2.8 cents. 



B, Artificial Digestion Experiments with Leather. 



Stutzer and Klinkenberg "were the first to propose this 

 method. They argued that the amount of nitrogenous 

 material that could be dissolved or digested would give a 

 fairly correct idea of the value of the substance as a source 

 of nitrogen for growing plants. They prepared the diges- 

 tive fluid l)y extracting the inner lining of a pig's stomach, 

 cut fine, with five litres of 0.2 per cent, hydrochloric acid 

 for two days, filtering the solution, and preserving in glass- 

 stoppered bottles, adding a few grams of salicylic acid to 

 prevent fermentation. Tiiey submitted a variety of materials 

 to the action of this solution. A few results are given 

 below : — 



Substance. 



Per Cent. 



of Nitrogen 



digested. 



Blood, 



Leather (cooked, and then roasted) , 



Raw bone, 



Steamed bone, .... 



89.75 

 39.19 

 98.70 

 90.50 



Drs. Shepard and Chazal * afterwards submitted a great 

 variety of nitrogen-containing materials to the action of 

 Stutzer's solution. Several of the results obtained are pre- 

 sented below : — 



Per Cent, of Nitrogen 

 digested. 



Roasted leather raeal,f 37.80 



Dried blood (black), 78.61 



Fish scrap, 88 . (37 



* See Report of Connecticut Experiment Station, 1885, page 117 



t The authors remarlc that " this prepared leather was an excellent article, so far 



as preparation goes, and one capable of being used in the fertilizer trade without 



much fear of detection." 



