62 



PROCEEDINGS OF THE AMERICAN ACADEMY 



III. 



IV. 



Mg 2 P 2 7 . 



0.2902 gr. 

 0.2903 gr. 

 0.2908 gr. 

 0.2913 gr. 

 0.2919 gr. 

 0.2920 gr. 

 0.2920 gr. 

 0.2935 gr. 

 0.2941 gr. 



P 2 5 found. 



0.1857 gr. 

 0.1857 gr. 

 0.1860 gr. 

 0.1863 gr. 

 0.1866 gr. 

 0.1867 gr. 

 0.1867 gr. 

 0.1877 gr. 

 0.1880 gr. 



P 2 O n required. 



0.1863 gr. 

 0.1863 gr. 

 0.1863 gr. 

 0.1863 gr. 

 0.1863 gr. 

 0.1863 gr. 

 0.1863 gr. 

 0.1885 gr. 

 0.1885 gr. 



Error. 

 —0.0006 gr. 

 —0.0006 gr. 

 —0.0003 gr. 



0. 

 +0.0003 gr. 

 -f-0.0004 gr. 

 + 0.0004 gr. 

 —0.0008 gr. 

 —0.0005 gr. 



Per cent, 

 error. 



—0.32 

 —0.32 

 —0.16 



0. 

 -J-0.16 

 +0.21 

 +0.21 

 —0.42 

 —0.27 



In experiments (40) to (43) inclusive 10 cm. 8 of strong ammonia 

 were added to 40 cm. 8 of the phosphate solution and then 10 cm. 3 of 

 magnesic chloride mixture. The precipitates of (42) and (43) were 

 dissolved by adding hydrochloric acid to the supernatant liquid and 

 thrown down again with ammonia. 



Mg 2 P 2 7 . P 2 O s found. 



(40) 0.2946 gr. 0.1884 gr. 



(41) 0.2950 gr. 0.1887 gr. 



(42) 0.2927 gr. 0.1872 gr. 



(43) 0.2936 gr. 0.1878 gr. 



In experiments (44) to (47) inclusive 10 cm. 8 of strong ammonia 

 were added to 40 cm. 8 of the phosphate solution, and then 25 cm. 8 of 

 magnesic chloride. The precipitates of (46) and (47) were dissolved 

 by hydrochloric acid added to the supernatant liquid and again thrown 

 down with ammonia. 



IV. 



Mg t P 2 7 . P 2 O e found. 



' (44) 0.2977 gr. 0.1904 gr. 



(45) 0.2986 gr. 0.1910 gr. 



1 (46) 0.2952 gr. 0.1888 gr. 



Per cent 

 error. 



P 2 5 required. Error. 



0.1885 gr. +0.0019 gr. +1.01 



0.1885 gr. +0.0025 gr. +1.33 



0.1885 gr; +0-0003 gr. +0.16 



[(47) 0.2954 gr. 0.1889 gr. 0.1885 gr. +0.0004 gr. +0.21 



For each of the experiments (48) to (60) inclusive 40 cm. 8 of the 

 phosphate solution were taken. Portions (48), (49), (50), and (51) 

 were precipitated with 40cm. 8 of magnesic chloride mixture containing 

 4 gr. of amnionic chloride more than the usual amount, the precipi- 

 tate being added to the phosphate in experiments (48) and (49), the 

 phosphate (gradually) to the precipitant in (50) and (51). In ex- 

 periments (52) and (53) the solution of the phosphate was acidulated 

 with 8 cm. 8 of hydrochloric acid, made alkaline with ammonia — 



