FERTILIZERS. 131 



by vegetation experiments under accurately controlled conditions, in 

 which nitrogen is supplied in the same materials which have been tested 

 by digestion experiments." In order to further test the method 

 employed in the earlier experiments and determine the efficiency of the 

 pepsin now found in the market, various preliminary experiments with 

 ground bone, dried blood, tankage, dry-ground fish, ammonite, cotton- 

 seed meal, castor pomace, linseed meal, and pea meal, and with various 

 cheap "ammoniates " used as adulterants, some of which contained 

 leather, were undertaken, which showed that the results obtained in 1893 

 substantially agreed with those obtained in 1885, " and proved that 

 the pepsin solutions used in the two series of trials were alike in their 

 solvent action." 



The 125 brands of fertilizers analj^zed at the station during 1893 

 were examined by this method, as follows : 



" One gram of the mixed fertilizer was wasiied on a filter with about 250 cc. of cold 

 water to remove soluble salts and the residue . . . was brought into a 150 cc. 

 flask, with 100 cc. of pepsin-hydrochloric acid solution. 



"This solution wasprepared by mixing 5 gm. of Parke & Davis's pulverized pepsin 

 (guaranteed to dissolve 2,000 times its weight of coagulated white of egg) in 1,000 

 cc. of hydrochloric acid diluted to a strength of 0.2 per cent. 



'•'The flasks containing the weighed substance, together with pepsin solution, were 

 kept for 24 hours loosely corked in a water bath having a constant temperature of 

 40" C. 



"At the end of the second, fifth, eighth, and eleventh hours 2 cc. of a 10 per cent 

 hydrochloric acid solution Avas added. 



"After 24 hours' digestion the contents of the flask were filtered and nitrogen was 

 determined, by the Kjeldahl method, in the washed and dried residues." 



The results indicate that of the 125 brands 105 were above sus- 

 picion (60 per cent or more of nitrogen soluble), 12 near the danger 

 line (50 per cent soluble), and 8 probably contained some comparatively 

 worthless form of organic nitrogen (less than 50 per cent soluble) ; 

 but '' the method can not at present do more than create a strong jjre- 

 sumption for or against the quality of the goods." 



The amounts of nitrogen in the above unmixed materials rendered 

 soluble by putrefaction were also determined by a method of which 

 the following is the perfected form : 



"Into narrow-necked flasks of about 500 cc. capacity were weighed duplicate por- 

 tions of each of the materials under experiment, together with 0.12 gm. of tobacco 

 ash, which had been slightly acidified with phosphoric acid aiul dried; 300 cc. of 

 water from the city service pipes was added to each flask aud the contents were 

 boiled briskly for an hour. Before cooling, the necks of the flasks were filled with 

 sterilized cotton plugs. 



"To each flask was next added 0.05 gm. sodium carbonate, sufficient to neutralize 

 any free acid and to give the contents an extremely slight alkaline reaction, aud 

 finally was introduced 1 cc. of a putrid extract from a mixture of rotting meat and 

 manure. 



"The flasks were placed in a water bath which was kept at a constant temperature 

 of 100" F. during the day and allowed at night to sink to the temperature of the 

 room, which did not vary much from TG*^ F. 

 3714— No. 2 1 



