90 T. Lyttleton Lyon and James A. Bizzell 



dilute hydrochloric acid was added and the mixture was evaporated to 

 complete dryness. The resulting residue was taken up with hot water, 

 and a small quantity of hydrochloric acid was filtered, washed thoroly 

 with hot water, dried, ignited, and weighed as silica. 



Phosphorus. — To determine the phosphorus content, the filtrate and 

 washings from the silica were made up to 200 cubic centimeters, and one- 

 half was taken for the determination of phosphorus gravimetrically 

 according to the official method described in Bulletin 107 (revised) of the 

 United States Bureau of Chemistry, page 3. 



Calcium, magnesium, potassium, and sodium. — The remaining 100 

 cubic centimeters not used for the phosphorus determination was treated 

 with ammonium hydroxide to remove iron and aluminum and the 

 precipitate was filtered and washed thoroly. The filtrate and washings 

 were concentrated to about 75 cubic centimeters and calcium was deter- 

 mined by the official method described in Bulletin 107 (revised) of the 

 United States Bureau of Chemistry, page 15. The filtrate and washings 

 from the calcium precipitate were made up to 200 cubic centimeters, 

 one-half of which was used for the determination of magnesium according 

 to the official method described on page 16 of the bulletin cited, and the 

 other half for the determination of potassium and sodium according 

 to the official method described on page 17 of the same publication. 



METHODS FOR THE CHEMICAL ANALYSIS OF MANURE 



The preparation of the sample, and the determinations of moisture, 

 nitrogen, phosphorus, and sulfur, for the chemical analysis of manure, 

 were made according to the methods already described for the analysis 

 of the crop. 



Potassium. — The potassium content in manure was determined by the 

 official method for determining potassium in organic compounds, described 

 in Bulletin 107 (revised) of the United States Bureau of Chemistry, 

 page 11. 



Calcium and magnesium. — A 5-gram sample was incinerated and dis- 

 solved in a small quantity of hydrochloric acid. The resulting solution 

 was cooled and made up to 500 cubic centimeters, and an aliquot part 

 corresponding to 0.5 gram of the original sample was taken for the 

 determination of calcium and magnesium according to the official methods 



90 



