4 BULLETIN 245, U. S. DEPARTMENT OF AGEICULTURE. 



After five days' incubation at 28 to 30° C. the plates were counted. 

 The average counts of the duplicate plates were taken and converted 

 into equivalents for 1 gram of dry manure by the use of the figures 

 obtained from the duplicate 10-gram samples that had been dried at 

 100° C. The results obtained by plating on the standard beef agar 

 are comparative and serve to show the germicidal action of the 

 chemicals on the majority of the bacteria present in the manure. 

 Dr. Seemann, in the work at New Orleans, used a medium prepared 

 from manure water, but the counts were practically the same as 

 those on beef agar. 



CHEMICAL EXAMINATION. 



The manure samples were analyzed for solids, ash, ammonia, and 

 nitrogen, using the methods of the Association of Agricultural 

 Chemists (Wiley, 1908). The total nitrogen determinations were 

 made by the Nitrogen Laboratory of the Bureau of Chemistry. The 

 results obtained by the magnesium-oxid distillation method for 

 ammonia, which are not reported in the table, although much higher, 

 showed the same general tendencies as the figures obtained on the 

 water extracts. 



Water extracts were prepared from each sample by taking 25 grams 

 of the finely divided manure and adding 500 c. c. of distilled water, 

 allowing them to stand for one hour, with occasional shaking. The 

 solutions were filtered, and the following determinations were made: 

 Water-soluble nitrogen, ammonia, nitrites, nitrates, and reaction. 



Ammonia was extracted by the Folin and Macallum (1912) aera- 

 tion method and nesslerized. Nitrites were determined with the 

 sulphanilic acid reagent, and nitrates by the reduction method 

 with aluminum foil (American Public Health Association, Labora- 

 tory Section, 1912). Nitrites and nitrates were not usually found 

 in the samples examined, because the manure had not stood suffi- 

 ciently long. The reaction was determined by taking 20 c. c. of the 

 water extract, diluting with 200 c. c. of carbon-dioxid free water, and 

 titrating with twentieth normal acid, using alizarin red as indicator. 



GENERAL ACCOUNT OF SUBSTANCES USED. 



Representatives of two groups of substances were tested during 

 the season's work, namely, (1) inorganic and (2) organic, including 

 volatile and nonvolatile substances and some plant material. These 

 substances are arranged in alphabetical order in the respective 

 groups. 



INORGANIC SUBSTANCES. 



Of the inorganic substances, arsenical dip, chlorid of lime, Epsom 

 salts, lime-sulphur, and sulphuric acid in three concentrations were 

 used. 



