180 EXPERIMENT STATION RECORD. 



Ill tills coiiiic'ctioii B. B. Boss ciilled attention to a new reaction 

 between uminoniuiii ]»liosphoiiiolyl)(Iate, >suli)lnuic acid, and hydrogen 

 peroxid, whicli be suggested might be utilized in the voluinetric 

 deteriniiiatioii of phosphoric acid. 



In a paper on "The estimation of pliosphoric acid by titration of the 

 yellow precipitate of ammonium phosphomolybdate," B. W. Kilgore 

 reviewed the literature of this method, and reported results of com- 

 parisons of Pemberton\s method with the official, method. The results 

 l)y the former method were generally too high, due, as the experiments 

 indicate, to the separation of a mixture of molybdic acid and molyb- 

 date of ammonia at the temperature prescribed. By reducing the 

 temi^erature to 60° 0. in the bath, correspondiug to 55° in the tiask, 

 results closely agreeing with those given by the gravimetric method 

 were obtained. It was also found that the official molybdate solution 

 was less liable to form a deposit than the aqueous solution recom- 

 mended by Pemberton. By using L'5 cc. of the official solution for each 

 0.2 gm. of substance and reducing the temj)erature of the bath to 60° 

 the author obtained fairly concordant results which agreed well with 

 those obtained by the gravimetric method. 



A paper on "A comparison of results by old and new methods for 

 citrate-soluble phosphoric acid," by B. W. Kilgore and C. B. Williams, 

 was read, in which attention was called to the fact that changes in the 

 manipulation of the official method made at the last meeting involve 

 an increase in actual temperature of digestion of about 2 ° C. ; and 

 results of 17 tests are reported which show that this increase in tem- 

 l^erature causes an average decrease of 0.5 per cent of insoluble 

 phosphoric acid. 



A paper on " A comi)arison of Pemberton's method of phosphoric acid 

 determination with the official method," by F. Bergami, was presented 

 to the convention. In this it was shown by the results of comparative 

 trials on 15 materials that the Pemberton method gave results a little 

 lower than those obtained by the official method. It is suggested that 

 the results by the official method w^ould probably be somewhat reduced 

 if special precautions were taken to neutralize the ammonia solution of 

 the phospho-molybdate precipitate. The results on the whole are 

 thought to be generally favorable to the Pemberton method on the 

 score of rapidity and accuracy. It was observed in connection with 

 this investigation that the presence of a small amount of carbonic acid 

 in the standard alkali did not affect the accuracy of the determinations. 



A mechanical shaker for precipitating solutions of phosx^hate was 

 described by H. A. Huston. 



In a paper on " The determination of phosphoric acid by molybdic 

 solution," W. E. Garrigues reported results of investigations on the 

 effect of evaporating phosphoric acid solutions to dryness to remove 

 silica ujion the subsequent determination of phosphoric acid. It was 

 found that both nieta and pyrophosphoric acid were formed in this case 



