C H EMISTR Y — BAXTER . 



149 



Baxter, Gregory P., Harvard University, Cambridge, Massachusetts. 

 Grant No. 154. Research upon the atomic weight of manganese. 

 (For first report see Year Book No. 3, p. 105.) $500. 



Abstract of Report. — Four samples of manganous bromide were pre- 

 pared. In the case of samples A and B, the manganese was freed 

 from other metals by crystallization of potassium permanganate, this 

 operation being performed thrice with sample A and ten times with 

 sample B. After reduction with sulphur dioxide, both samples were 

 converted into bromide by precipitation with ammonium carbon- 

 ate, solution of the carbonate in nitric acid and crystallization of 

 the nitrate, reprecipitation with ammonium carbonate in platinum, 

 and finally solution in hydrobromic acid in a quartz dish. Bromine 

 was expelled from the solution by heating in quartz, and the bromide 

 was several times recrystallized in platinum. 



Samples C and D were obtained from commercial manganese dioxide 

 and manganous sulphate. Purification was effected by fractionation 

 with hydrogen sulphide and sodium hydroxide. The manganese 

 was converted into bromide as in the case of samples A and B. 



After fusion in a stream of nitrogen and hydrobromic acid gases 

 in a platinum boat, the bromide was dissolved and precipitated with a 

 weighed equivalent amount of the purest silver. The exact end-point 

 was found, and then the silver bromide was collected and weighed. 



ABSTRACT. 



Series I.— MnBRj : -'AG. 



[ Ag = 107.930 ; Br = 79-955- ] 



Number of 

 analysis. 



Sample 



of 

 MiiBro. 



Sample 

 of Ag. 



Weight of 



MnBr 2 

 iu vacuum. 



Weight of 



Ag. 

 in vacuum. 



Atomic 



weight of 



Mn. 



I 



2 



3 

 4- 

 5 

 6. 



7 

 8 



9 

 io 

 ii 



12. 



'3 

 14 

 15 



Average . 



A 

 A 



C 



c 

 c 



A 

 B 

 A 

 R 

 B 

 B 

 C 

 D 

 D 

 D 



C 

 C 



c 



A 

 B 

 A 

 A 

 B 

 B 

 C 

 C 

 A 

 A 

 B 

 A + B 



Grams. 



6-53745 

 4.81006 

 4.S8098 

 5.63220 

 6.5S985 

 5-7^926 

 4.19912 



5- 16335 

 3.92227 



4-49159 

 3.60073 



4-77393 

 3.57660 



5-69973 



Grains. 



6.56755 

 4.83238 



4-90354 

 5-658I3 

 6.62041 

 5.82600 

 4-2IS39 

 3.61478 

 5-I87II 



3 94045 

 4-51250 



3-6I736 

 4.79619 



3 59319 

 5.72641 



54 

 54 

 54 

 '54 

 54 

 54 

 54 

 54 

 54 

 54 

 54 

 54 

 54 

 54 

 54 



961 

 953 

 957 

 961 



954 

 959 

 964 



954 

 961 



954 

 95o 

 953 

 948 

 953 

 944 



54-955 



