8 BULLETIN 113, U. S. DEPARTMENT OF AGRICULTURE. 



soluble nitrogen, ammonia, amino nitrogen, nitrites, nitrates, and 

 reaction. 



Ammonia was extracted bytheFolin and Macallum (1912) aeration 

 method and nesslerized. The amino nitrogen was determined by the 

 Yan Slyke method (Van Slyke, 1911), but as very little nitrogen in 

 this form was present in the extracts, the figures are not given. 

 Xitrites were determined with the sulphanilic acid reagent and 

 nitrates by the reduction method with aluminum foil (American 

 Public Health Association. Laboratory Section. 1912). Nitrites and 

 nitrates were not usually found in the samples examined, because the 

 manure had not stood sufficiently long. The reaction was determined 

 by taking 20 c. c. of the water extract, diluting with 200 c. c. of 

 carbon clioxid free water, and titrating with X/20 acid, using 

 Alizarin red as indicator. Fehling's solution was not reduced by any 

 of the 20 or more water extracts tested. 



GENERAL ACCOUNT OF CHEMICALS USED. 



In the course of the season 24 different chemicals were tried in 

 various concentrations. Of , these only seven have shown any effective 

 larvicidal action in the strengths used. In the following paragraphs 

 some of the chemicals which gave negative results are first noted, 

 and later in the paper those which appeared to have the greatest 

 value are described in more detail. 



CHEMICALS WHICH GAVE LOW LARVICIDAL RESULTS. 



KEEOSE^E EMEXSIO^. 



Kerosene emulsion, prepared according to the Riley-Hubbard 

 standard formula, was used in strengths varying from 1 jDart 

 emulsion in 5 parts water to 1 part emulsion in 50 parts water. 

 In no case were results obtained which showed any appreciable 

 larvicidal action. Even from the cage subjected to the strongest 

 dosage 956 flies were taken, the average from the two control cages 

 being 1,355 flies. 



No chemical analyses of the manure were made. The bacterial 

 count, where the strongest emulsion (1-5) was used, was 16,600 

 million per 1 gram of dry manure as compared with 6,130 million 

 in the controls. These counts were made eight days after treatment 

 with the chemical, but as the bacterial content of manure varies 

 greatly and only one determination was made no conclusion can be 

 drawn. 



Kerosene emulsion was not used on any open-pile experiments. 

 TTe have already called attention to the fact that Dr. Howard in 

 his tests found that this reagent was ineffective when apj^lied on a 

 large scale. 



