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IX. Chemical Examination of the Oxides of Manganese. By 

 EDWARD TURNER, M. D. F. R. S. E. Professor of Chemis- 

 try in the University of London, and Fellow of the Royal 

 College of Physicians of Edinburgh. 



(Bead M and llth December 1827. ) 



I T was originally my intention, in entering on this inquiry, mere- 

 ly to ascertain the composition of the ores, the mineralogical cha- 

 racters of which have been so ably delineated by Mr HAIDINGER 

 in the preceding paper. I had advanced however but a short way 

 in the investigation, when my progress was arrested by doubts 

 both as to the manner of conducting 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 supply- 

 ing 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 composi- 

 tion of the artificial oxides of that metal ; and in the second, ap- 

 plying the facts thus established to illustrate the chemical con- 

 stitution of the native oxides described by Mr HAIDINGER. 



PART I. 



ON THE ATOMIC WEIGHT OF MANGANESE. ANALYSIS OF THE 



CARBONATE OF MANGANESE. 



A pure carbonate of the protoxide of manganese was prepared 

 in the following manner. The dark brown mass left in the pro- 

 cess for procuring oxygen gas from the common peroxide of 



