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VII. Chemical Examination of the Oxides of Manganese. By 

 Edward Turner, M.D. F.R.S. Ed. Professor of Chemistry 

 in the University of London^ and Fellow of the Royal College 

 of Physicians qf Edinburgh.* 



TT was originally my intention, in entering on this inquiry, 

 -*• merely to ascertain the composition of the ores, the mine- 

 ralogical characters of which have been so ably delineated by 

 Mr. Haidinger in the preceding paper f. I had advanced, 

 however, but a short way in the investigation, when my pro- 

 gress was arrested by doubts both as to the manner of con- 

 ducting the analyses, and as to the mode of calculating their 

 results. In this uncertainty I found it necessary to extend my 

 original plan, with the view of supplying by my own researches 

 what appeared to be not sufficiently established by the labours 

 of other chemists. I have accordingly divided the essay into 

 two parts; attempting in the first division to ascertain the 

 atomic weight of manganese, and the composition of the arti- 

 ficial oxides of that metal; and in the second, applying the 

 facts thus established to illustrate the chemical constitution of 

 the native oxides described by Mr. Haidinger. 



Part I. 

 On the Atomic Weight of Manganese. — Analysis of the Car- 

 bonate of Manganese. 

 A pure carbonate of the protoxide of manganese was pre- 

 pared in the following manner. The dark brown mass left in 

 the process for procuring oxygen gas from the common per- 

 oxide of manganese by heat, was mixed with a sixth of its 

 weight of powdered charcoal, and exposed to a white heat for 

 half an hour. The protoxide thus formed was dissolved by 

 muriatic acid, the solution evaporated to dryness, and the re- 

 sidue kept for some time in a state of fusion at a red heat. 

 The resulting chloride of manganese was re-dissolved by di- 

 stilled water; and after being filtered, was found to contain 

 no impurity except a little lime, which was separated by the 

 oxalate of potash. The manganese was then precipitated by 

 a solution of the bicarbonate of potash, and the carbonate of 

 manganese was carefully edulcorated and collected on a filter. 

 After removing the upper layer, which had become rather 

 brown by exposure to the air, the white carbonate was kept 

 in a vacuum along with a vessel of sulphuric acid until it be- 



* From the Transactions of the Royal Society of Edinburgh. 



f On a future occasion we propose to give Mr. Haidinger's paper here 

 alluded to, and also Dr. Turner's analyses of the ores which he has de- 

 scribed.— Edit. 



came 



