Gooch and Austin — Oxidation of Manganese. 267 



500 cmS , was heated to 80° C, and acid potassium carbonate 

 added, in quantity a little more than enough to neutralize the 

 remnant of the acid present. The precipitate was collected 

 upon asbestos, and after careful washing was returned to the 

 flask in which the precipitation had been made. The oxygen 

 value of the oxide was determined by one or other of the 

 methods described. In the one case the flask was fitted with a 

 paraffined stopper having two bores, one holding a Will and Yar- 

 rentrap absorption apparatus (in which a solution of potassium 

 iodide dissolved any escaping iodine), the other a small separating 

 funnel. Sulphuric acid and potassium iodide in solution were 

 run in through the funnel, the iodine set free was titrated 

 with thiosulphate — the amount of manganese being reckoned 

 from the iodine set free. The results of this work follow in 

 the first part of Table Y. In the second case the dioxide 

 obtained in the manner described above was reduced by warm- 

 ing gently with a decinormal solution of arsenious acid. After 

 cooling, and neutralizing with acid potassium carbonate in the 

 presence of Rochelle salt, the excess of the arsenious acid was 

 estimated with iodine in the presence of starch. The estima- 

 tion by this method gave the results recorded in the second 

 part of Table Y. 







Table Y. 





Mn taken 



in the 



form of chloride. 



Mn found upon 



the hypothesis that 



MnO a is the oxide 



finally obtained. 



Error. 



grm. 





grm. 



grm. 





By 



reduction with potassium 



iodide. 



0-0643 





0-0637 



0-0006 — 



0-0643 





0-0642 



o-oooi — 



0-0643 





00642 



o-oooi — 



00651 





00651 



o-oooo 



0-1125 





0-1121 



0-0004 — 



0-1125 





0-1121 



0-0004 — 



0-1125 





0-1120 



0-0005 — 



0-1214 





0-1206 



0-0008 — 



0-1214 





0*1207 



0-0007 — 



0-1214 





0-1223 



0-0009 + 



0-1214 





0-1214 



0000 





By reduction with arsenious 



oxide. 



0-1213 





0-1212 



o-oooi — 



0-1213 





0-1201 



0-0012 — 



0-1213 





0-1203 



o-ooio— 



0-1213 





0-1208 



0-0005 — 



