412 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 54 



and titrated with potassium bromide. 

 KBr appears in the third column : 



The AgMn04 equivalent to 100 



Mean. 190.647, ± .0361 



Vacuum weights are given throughout. To the first series of experi- 

 ments the authors attach little importance^ and numbers 1 and 4 of the 

 second series they also regard as questionable. These experiments rep- 

 resent the use of sulphur dioxide as the reducing agent, and were attended 

 by the formation of an insoluble residue, apparently of a sulphide. Ex- 

 cluding them, the remaining eight experiments of the second series give 

 in meaU' — 



KBr :AgMnO,:: 100: 190.584, ± .0062, and Mn = 54.95 



which will be used for the present calculation. Dewar and Scott also 

 made determinations with manganese chloride and bromide. With the 

 first salt they found Mn = 54.91, and with the second. Mn = 54.97; but 

 they give no details. 



Marignac's work upon the atomic weight of manganese also appeared 

 in 1883.' He prepared the oxide, MnO, by ignition of the oxalate and 

 subsequent reduction of the resulting Mn.O^ in hydrogen. The oxide, 

 with various precautions, was then converted into sulphate. The per- 

 centage of MnO in MnS04 is appended: 



2.6587 grm. MnO gave 5.6530 MnSO^. 

 2.5185 " 5.3600 " 



2.5992 " 5.5295 " 



2.8883 " 6.1450 " 



47.032 per cent. 



46.987 



47.006 



47.002 



Mean, 47.007, ± .0025 

 Hence Mn = 55.022. 



J. M. Weeren, in 1890,* published determinations made by two methods, 

 the one Marignac's. the other von Hauer's. From manganese sulphate 



' Arch. Sci. Phys. Nat. (3), 10, 21. 1883. 



* Atom-Oewichtsbestimmung dcs Mang.ins. Inaug:ural Dissertation. Halle, 1890. 



