322 MAINE AGRICULTURAL EXPERIMENT STATION. I9IO. 



in birds' urine the reverse condition is true and the larger part 

 of the nitrogen present is in the form of uric acid. Therefore, 

 in order to determine the amount of nitrogen which was present 

 as undigested proteid it was necessary to determine the other 

 forms separately. The ammonia was determined by the offi- 

 cial method, namely distillation with MgO, but for uric acid 

 there is no official method. Its estimation presents by far 

 the most serious obstacle encountered in digestion experiments 

 with poultry. On account of the presence of ammonia in the 

 feces moisture was determined by drying several days over 

 sulphuric acid in a partial vacuum. 



Method for Determining Uric Acid. 

 After carefully considering all available methods for deter- 

 mining this acid the one worked out by Doctor Brown and 

 given in Bulletin 56, United States Department of Agriculture, 

 Bureau of Animal Industry, page 39, was given a trial. Our 

 first attempts with this method were not very satisfactory. The 

 filtration, after dissolving in piperidin solution, on paper was 

 very tedious and in some cases impossible to carry through. 

 Also in the case of some of the more highly colored feces so 

 much coloring matter was left in the residue that titration could 

 not be carried out. After a great many trials and many deter- 

 minations by different modifications, the method which was 

 finally adopted and by which most of the determinations were 

 made is as follows : 



Ten grams of the ground and thoroughly mixed feces were 

 weighed into a 250 c. c. beaker and treated with 100 c. c. of 95 

 per cent alcohol filtered through paper and washed twice with 

 50 c. c. of alcohol, then washed 3 times with ether and allowed 

 to dry. These treatments removed a greater part of the color- 

 ing and fatty matter. The residue when dry was returned to 

 the beaker, 100 c. c. of a . 5 per cent solution of IICI added and 

 set in the refrigerator over night. The following morning the 

 material was filtered through paper and washed twice with 

 cold water, returned to the beaker with 100 c. c. of water and 

 enough piperdine or sodium hydrate added to dissolve the uric 

 acid. Piperdine was usually used as the solvent, as it seemed 

 to dissolve the uric acid more quickly than a weak solution of 

 sodium hydrate. A few drops of phenolphthalein were added 



