Mr. Brown on the Commercial Value of Black Oxide of Manganese. 187 



then brought ia contact with the hinoxide of manganese, which is to be 

 heated to redness. The manganese begins at the edges to burn ; the 

 combustion gradually approaches the centre ; and when heat is applied 

 somewhat longer, the mass becomes quite green from the formation of 

 the protoxide. The hydrogen uniting with the oxygen of the man- 

 ganese is converted into water, which is caught by the chloride of 

 calcium. The oxide of manganese is then allowed to cool in a current 

 of hydrogen, to jjrevent its oxidizing. When cool, it is weighed, and 

 the decrease of weight between its present and the former weight, 

 gives the quantity of oxygen above protoxide contained in the mineral. 

 The chloride of calcium is then weighed, and the increase multiplied by 

 I gives also the quantity of oxygen, which is a check on the decrease of the 

 binoxide. The protoxide thus formed is then converted into protosesqui- 

 oxide or red oxide, by heating it in a current of air. This is again 

 weighed, and from the increase between it and the protoxide, we can 

 calculate the amount of oxygen that should be in the specimen, if the red 

 oxide and protoxide were pure. 



TABLE I. 



Exact results of Analyses. 



BiNOXIDES. 



Amount used in grains, 



Geissen, 50 



— 2d example, . " .... 



Kilpatrick, 



— 2d exam., 

 Thuringia, 



— 2d exam., 



New Zealand, 



Table Mountain, . . , 



— 2d exam., 



Water. 



•64 

 •65 

 1-61 

 1-52 

 2^43 

 2^02 

 3-19 

 M2 

 MO 



Oxygen. 



8-91 



Sesquioxides. 



Amount used 



\n graum. 



Braunite, 50 . 



— 2d exam., ... « . 

 New Brunswick, > . 



Water. 



3-27 

 3-85 

 4-52 



Impure Protox.ide. 



,.. 40-45 



8-88 40-47 



8-65 39-74 



8-54 39-68 



7-30 41-00 



7-14 40-84 



7-01 39-80 



5-67 43-21 



5-70 43-07 



Oxygen. Impui-e Protoxide. 



6-37 40-36 



6-57 40-10 



5-09 40-34 



TABLE IL 



Mean per ccnta^e. 



BiNOXIDES. 



Geissen, 1-24 17-79 



Kilpatrick, 2-26 17-19 



Thuringia, 4-45 14-44 



New Zealand, 0-38 14-02 



Table Mountain, 222 11-39 



1752 



