60 PROCEEDINGS OP THE AMERICAN ACADEMY 



Experiments (11) to (16) inclusive were made with portions of 

 40 cm. 3 each of Solution II. Portions (11) and (12) were acidulated 

 with hydrochloric acid and, after the addition of ammonia in excess, 

 precipitated with 6 cm. 8 of magnesic sulphate mixture. Portions (13) 

 and (14) were acidulated with 0.5 gr. of citric acid and, after the ad- 

 dition of ammonia, treated with 6 cm. 8 of magnesic sulphate mixture ; 

 which amount failing (on account of the presence of a citrate) to 

 throw the phosphoric acid down entirely, 6 cm. 8 more of the same 

 mixture were added to complete the precipitation. Portions (15) and 

 (16) were acidulated with hydrochloric acid and 0.5 gr. of citric acid, 

 ammonia added in excess and precipitation effected with 12 cm. 3 of 

 magnesic sulphate mixture. The precipitates of (11), (13), and (15) 

 were filtered off, washed and ignited; those of (12), (14), and (16) 

 were filtered off on paper, drained, dissolved (without previous wash- 

 ing) in hydrochloric acid, thrown down again with ammonia, and, the 

 precipitate having settled, filtered off, after the addition of a few 

 centimeters of magnesic sulphate mixture, upon asbestus, washed and 

 ignited. The precipitates were all thrown down the first time from 

 hot solutions. 



Per cent, 



error. 



+1.37 

 0. 



+3.31 

 0. 



+3.31 

 0. 



iM 



Experiments (17) to (20) inclusive were made with portions of 

 40 cm. 3 each of Solution III. To each portion were added 6 cm. 8 of 

 strong hydrochloric acid, 20 cm. 8 of strong ammonia, and 20 cm. 8 

 of magnesic sulphate mixture. The first precipitate was filtered off 

 on paper, drained, dissolved in hydrochloric acid and thrown down 

 again with ammonia. In portions (17) and (18) the second precipi- 

 tation was effected instantly by adding concentrated ammonia to the 

 acid solution, the precipitate being consequently quite voluminous, 

 and magnesic sulphate mixture was added after settling. In portions 

 (19) and (20) the second precipitation was brought about more grad- 

 ually by neutralizing with dilute ammonia. 



