1254 MANURES AND MANURING 



earth, which CDiitained 0.115 gr. of nitric acid per kg., was rendered thorough- 

 ly homogeneous, then brought up to a moisture percentage of about 

 20 %, after which lots of one kilogram were taken from it. The different 

 manures ha\nng been reduced to an exceedingly^ fine powder, a weight of 

 each of them corresponding to i gr. of nitrogen was weighed off ; each of 

 these weighed quantities was thoroughly mixed with i kg. of earth. 

 For each manure, three different preparations were made, in order to be 

 able to ascertain the quantity of nitric acid formed, after different periods 

 of experimentation. The nitric acid contained in the mixture of soil and 

 manure was also determined after 1,2 and 5 months' contact. By way of 

 control the same was done with 3 lots of one kg. of earth to which no ma- 

 nure had been added, and the following results were reached : 



Nitric, acid contained in one kilogram of earth. 



After I month Two months Five months 



Soil without manure 0.145 gr- 0.160 gr. 0.326 gr. 



Dried blood 1.080 1.350 2.433 



Tanned leather 0.166 o.igo 0.404 



Chrome leather 0.003 c.021 0.227 



Roasted leather 0.220 0.263 0.523 



Dissolved leather (pasty) 0.742 0.952 1-547 



Dissolved leather (liquid) 0.990 1.200 2.015 



Sulphurated rape cake 0.888 1.287 2.291 



One of the results appeared to be altogether abnormal, namely that 

 given by the mixture of i kg. of earth with about 11 gr. of chrome leather; 

 not only was there no nitrification, but, a far more surprising fact, the pre- 

 existing nitrate disappeared. This rapid distruction of the nitrates was so 

 complete as to surprise the writer, who wondered whether the loss of the 

 nitric acid during the course of its determination, was owing to the presence 

 of chrome in the exhausting liquid. He therefore deemed it desirable at the 

 same time to carry out a chemical control of his method of estimation and 

 also an agricultural control. 



Chemical Control. — In order to ascertain the proportion of nitric acid, 

 the procedure adopted was as follows : when the mixtures of earth and ma- 

 nure had been undergoing nitrification for the required time, thej' were 

 placed in a 2-litre flask, 500 cc. of water added and the flask rotated on the 

 SCHXOESING car. After a quarter of an hour the earth and water were 

 completely mixed, and the nitrates were dissolved in the surface liquid ; the 

 liquid was drawn off into a large glass, the soil was allowed to settle and the 

 surplus liquid filtered. 250 cc. of water were poured into the earth, which 

 was shaken up and filtered after .settling. This washing by decant- 

 ing was once more repeated, after which the liquid and the mud were 

 conve^-ed into the filter, and the latter washed after completion of drain- 

 ing off. In this way there were obtained the nitrates contained in the 

 soil in a clear but very but dilute solution, which it is necessary to con- 

 centrate in order to determine the quantity by the Schloesixg method. 



