282 THE ATOMIC WEIGHTS. 



MANGANESE. 



The earliest experiments of Berzelius* and of Arfvedsonf gave values 

 for Mn ranging between 56 and 57, and therefore need no farther con- 

 sideration here. The first determinations to be noticed are those of 

 Turner J and a later measurement by Berzelius. who both determined 

 gravimetrically the ratio between the chlorides of manganese and silver. 

 The manganese chloride was fused in a current of dry hydrochloric acid, 

 and afterwards precipitated with a silver solution. I give the MnCl 2 

 equivalent to 100 parts of AgCl in the third column : 



4.20775 grm. MnG 2 == 9.575 grm. AgCl. 43-945 \ 



, _ _ > 



3.063 = 6.96912 43-95-' 



12.47 grains MnQ 2 = 28.42 grains AgCl. 43.878 Turner. 



Mean, 43.924, .015 



Many years later Dumas || also made the chloride of manganese the 

 starting point of some atomic weight determinations. The salt was fused 

 in a current of hydrochloric acid, and afterwards titrated with a standard 

 solution of silver in the usual way. One hundred parts of Ag are equiva- 

 lent to the quantities of MnCl 2 given in the third column : 



3.3672 grm. MnCl 2 = 5.774 grm. Ag. 5 8 -3i7 



3.0872 " 5.293 " 58.3 26 



2.9671 " 5-0875 " 58.321 



1.1244 1.928 " 58.320 



1.3134 " 2.251 " 58.321 



Mean, 58.321, =h .001 



An entirely different method of investigation was followed by von 

 Hauer,^]" who, as in the case of cadmium, ignited the sulphate in a stream 

 of sulphuretted hydrogen, and determined the quantity of sulphide thus 

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

 MnS0 4 as calculated from them : 



4.0626 grm. Mn?O 4 gave 2.3425 grm. MnS. 57-66o per cent. 



4.9367 " 2.8442 " 57.613 " 



5.2372 " 3- OI 9 2 " 57.649 c< 



7.0047 " 4.0347 " 57.600 " 



4.9175 " 2.8297 " 57-543 



4-8546 " 2.7955 57.585 " 



4.9978 2.8799 " 57.625 



4 6737 " 2.6934 " 57.629 



4.7240 2.7197 " 57.57 2 



Mean, 57.608, =fc .008 



* Poggend. Anualen, 8, 185. 1826. 



t Berz. Jahresbericht, 9, 136. 1829. 



| Trans. Roy. Soc. Ediub., ir, 143. 1831. 



I Lehrbuch, 5 Aufl., 3. 1224. 



|| Ann. Chem. Pharm., 113, 25. 1860. 



If Journ. fur Prakt. Chem., 72, 360. 1857. 



