284 THE ATOMIC WEIGHTS. 



of experiments were made. First, the silver permanganate was heated 

 to redness in a ghiss bulb, first in air, then in hydrogen. Ikfore weigh- 

 ing, the latter gas was replaced by nitrogen. The data are as follows : 



AgMnO^. Ag + MnO. Per cent. Ag + MnO. 



5-8696 4-63212 78.917 



5-4988 4.33591 78.852 



7-6735 6.05395 78.894 



13-10147 10.31815 78.756 



("9.91065 78.782 



1 9.91435 78.811 



Mean, 78.835, dz .0174 



12.5799 



The duplication of the last weighing is not explained. 



In the second series the permanganate was dissolved in dilute nitric 

 acid, reduced by sulphur dioxide, potassium nitrite, .or sodium formate, 

 and titrated with potassium bromide. The AgMnO, equivalent to 100 

 KBr appears in the third column. 



AgMnO,. KBr. Ratio. 



6.5289 3-42385 190.686 



7-5378 3-9553 190.575 



6.1008 3.20166 190.559 



5-74647 3-00677 191.117 



6.16593 3-23602 190-540 



5-H329 2.6828 190.596 



5.07438 , 2.66204 190.624 



13.4484 7.05602 190.604 



12.5799 6.60065 190.5S8 



12.27025 6.43808 190.584 



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 suli)hur 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 mean — 



KBr : AgMn04 : : 100 : 190.584, ih .0062, 



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 



I 



*Arch. Sci. Phys. et Nat. (3), 10. 21. 16 



