CONVENTION OF OFFICIAL AGRICULTURAL CHEMISTS. 181 



and were afterwards incompletely reconverte<l into orthophosplioric 

 acid. His investigations indicate further that for amounts of phos- 

 pborieacid exceeding 0.1 gm. a greater proportion of molybdic solution 

 than 50 cc. to 0.1 (the proportion i)rescribed in tlie official methods) 

 must be used to insure promi^t and complete precipitation of the phos- 

 phoric acid in 1 hour. The Pemberton method in the hands of the 

 author gave results agreeing well with the official method, although 

 a little higher, due, it is believed, to incomplete precipitation in tlie 

 latter. The results obtained also indicate that it is immaterial 

 whether there is considerable or only a slight excess of ammonia at the 

 time of precipitation. A method is described which it is believed 

 largely overcomes the above objection. 



(3) Nitrogen. — A report on the study of methods of determining nitro- 

 gen, especially those applicable to substances containing nitrates, was 

 submitted by J. jNI. Bartlett. The changes proposed and adopted were 

 principally of a verbal character. In the directions for the prepara- 

 tion of standard solutions the word "alkali" was substituted for 

 "ammonia," and the wording in the different methods was changed to 

 conform to this modification. The amount of material taken for diges- 

 tion in the Kjeldahl and Gunning methods and their modifications was 

 directed to be uniformly stated as from 0.7 to 3.5 gm. Fassbender's 

 method was recommended for trial during the coming year, and the 

 Schulz-Tiemann method for nitric nitrogen was adopted as provisional. 

 The Fassbender method is essentially as follow.s: To 1 gm. of substance 

 0.7 gm. of mercuric oxid and 20 cc. of concentrated sulphuric acid are 

 added and digestion conducted as usual, bumping and frothing being 

 checked by the addition of a piece of paraffin the size of a pea. Tlie 

 ammonia is set free by adding 60 cc. of a solution of caustic soda and 

 potassium sulphid prepared by adding a solution of .350 gm. of potas- 

 sium sulphid in 2 liters of water to 11.5 liters of soda solution of 1.375 

 sp. gr. 



In a paper on " The determination of nitric nitrogen by the zinc-iron 

 method," F. S. Shiver reported the following method, which had given 

 in his hands practi(;ally theoretical results on pure nitrates, although 

 its applicability to mixed fertilizers had been tested to only a limited 

 extent: Five grams of nitrate were dissolved in 500 cc. of water and 

 50 cc. of this solution placed in a Kjeldahl digestion flask with 5 gm. 

 each of zinc dust and iron filings; 75 cc. of water and 80 cc. of sodium 

 hydrate, 1.3 sp. gr., were added and the flask connected with a con- 

 denser, to which was attached an Erlenmeyer flask containing the 

 standard acid. The contents of the flask were thoroughly mixed and 

 allowed to stand 1 hour, then heated gently, and finally boiled until 

 100 to 125 cc. were distilled over. Chlorids and sul]»hates did not 

 impair the accuracy of the method. The averages of a number of 

 determinations of nitrogen in nitrate of potash containing theoretically 

 13.88 per cent of nitrogen were by zinc-iron method 13.84, by modified 



