,[ * ] 



XV. Chemical Examination of the Oxides of Manganese. By 

 Edwaud Turner, M.D. F.R.S. Ed. Prof essor of Chemistry 

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

 of Physicians of Edinburgh. 



[Concluded from p. 35.] 



Part II. 



On the Composition of the Ores of Manganese described by Mr. 

 Haidinger. 



Method of Analysis. — pURE fragments of the ores were 

 * carefully selected, recjuced to fine 

 powder in a mortar of agate, and washed with distilled water. 

 Some of the ores yielded nothing to the action of water; but 

 from some of them, especially from those of Ihlefeld, minute 

 quantities of the muriate and sulphate of lime, and sometimes 

 of soda, were separated by the action of water. It is the ac- 

 cidental presence of the muriates which gives rise to the dis- 

 engagement of chlorine when sulphuric acid is added to some 

 of the native oxides of manganese, and which induced Mr. 

 Macmullin to regard chloric acid as a constituent of these ores. 

 For the correction of this error we are indebted to Mr. Richard 

 Phillips*, with whose observation my own experiments cor- 

 respond ; — none of the native oxides yield a trace of chlorine 

 on the addition of sulphuric acid, provided the muriates have 

 been previously removed by washing. 



The ores, before being submitted to analysis, were dried at 

 212° F., by which means they were brought to the same degree 

 of dryness which they possessed before being washed. The 

 water naturally contained in them was ascertained in every 

 instance by heating a known quantity of the ore to redness, 

 and collecting the water in a tube filled with fragments of the 

 chloride of calcium. 



The quantity of oxygen was in most cases ascertained both 

 by bringing the ore to the state of red oxide by exposure to a 

 white heat, and by converting it into the protoxide by means 

 of heat and hydrogen gas. When performed with the pre- 

 cautions stated in the first part of this communication, either 

 of these methods may be relied on with confidence; but the 

 first is more convenient in general practice, because it requires 

 less time and a more simple apparatus. The latter is some- 

 times very troublesome, owing to the difficulty with which some 

 of the ores of manganese, the native peroxide for example, are 



* Phil. Mag. and Annals, vol. i. p. 313. 



reduced 



