410 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 54 



An entirely different mctlKMl of investigation was followed by von 

 Ilauer/ who, as in the case of cadmium, ignited the sulphate in a stream 

 of sulphuretted hydrogen, and determined tlie quantity of sulphide thus 

 formed. I subjoin his weighings, and also the percentage of MnS in 

 MnSO. as calculated from them : 



4.0626 grm. MnSO^ gave 2.3425 grm. MnS. 



4.9367 

 5.2372 

 7.0047 

 4.9175 

 4.8546 

 4.9978 

 4.6737 

 4.7240 



2.8442 

 3.0192 

 4.0347 

 2.8297 

 2.7955 

 2.8799 

 2.6934 

 2.7197 



57.660 per cent. 



57.613 



57.649 



57.600 



57.543 



57. .585 



57.625 



57.629 



57.572 



Mean, 57.608, ± .008 



Hence Mn = 54.915. 



This method of von Hauer, which seemed to give good results with 

 cadmium, is, according to Schneider,^ inapplicable to manganese, for the 

 reason that the sulphide of the latter metal is liable to be contaminated 

 Math traces of oxysulphide. Such an impurity would bring the atomic 

 weight out too high. The results of two different processes, one carried 

 out by himself and the other in his laboratory by Eawack, are given by 

 Schneider in this paper. 



Eawack reduced manganoso-manganic oxide to manganous oxide by 

 ignition in a stream of hydrogen, and weighed the water thus formed. 

 From his weighings I get the values in the third column, which repre- 

 sent the MugO^ equivalent to one gramme of water : 



Hence Mn = 54.08. 



Here the most obvious source of error lies in the possible loss of water. 

 Such a loss, however, would increase the apparent atomic weight of 

 manganese; but we see that the value found is much lower than tliat 

 obtained either by Dumas or von Hauer. 



1 .Journ. prakt. Chem., 72, 360. 1857. 

 '■' Poggend. Annalen, 107, 605. 



