48 JOURNAL OF THE 



A COMPARISON BETWEEN THE WASHINGTON 

 AND ATLANTA METHODS FOR THE ES- 

 TIMATION OF REVERTED PHOS- 

 PHORIC ACID IN COMMER- 

 CIAL FERTILIZERS. 



H. B. BATTLE. 



To determine the difference in results as obtained by the Wash- 

 ington and Atlanta methods was the cause of the set of determina- 

 tions given below : 



The samples taken were acid phosphates made from S. C. Rock 

 and Navassa Rock — being regarded as types of the various manip- 

 ulated phosphates. They were ground and mixed carefully so 

 as to pass a ^V inch mesh sieve, and were kept in closely stoppered 

 glass bottles during the process of the analysis. 



The Washington Method, as pursued in the determinations, was 

 as follows: 2 grms. were ground in a small mortar with about 50 

 c. c. of water, allowed to settle, the liquid decanted on a filter and 

 allowed to run into a 200 c. e. flask — this grinding and decanting 

 was repeated twice, using pestle without rubber tip, and grinding 

 moderately each time. The residue was then transferred to the fil- 

 ter thoroughly washed. In the filtrate diluted to 200 c. c. the water 

 soluble P.>0^ was determined in 50c. c. (= i grm.). The residue on 

 the filter was then transferred to a flask of about 150 c. c. capacity, 

 using 100 c. c. strictly neutral solution ammonium citrate (sp. gr. = 

 1.09) and placed in a bath previously heated to 40'C and kept there 

 40 minutes, shaking vigorously twice during the operation*— the 

 temperature being kept constant at 40^C throughout the operation. 

 The solution was then filtered with a pump of ordinary power, after 

 which the residue was washed with one-half strength citrate solu- 

 tion three times, consuming about one hour in the washing. The res- 

 idue after being dried and ignited wasfused withNasCOs-f-KNOs and 

 the Insoluble P-iO^ determined in the usual manner as for the Total 

 viz: fusing, taking up with HgO and HNOg, diluting to 200 c. c, 



*By the strict Washington Method the flask should be shaken every five min- 

 utes, this was reduced to twice during the 40 minutes, owing to the peculiar ro- 

 tating bath used which is supposed to agitate the flasks slightly. 



