of the Oxides of Manganese. 149 



to be carried off mechanically by the acid vapour and lost. Tliis 

 accident has occurred to myself, and always happens when a large 

 quantity of free acid is rapidly expelled. By employing a slight 

 excess of acid, and raising the heat slowly, all loss from this cause 

 may easily be avoided. 



The dry salt obtained in my experiments was white, and dis- 

 solved readily and completely in distilled water. 



Like many other neutral metallic solutions it reddened deli- 

 cate litmus paper. It was nevertheless quite neutral ; for a single 

 drop of a dilute solution of potash occasioned a precipitate which 

 was not in the slightest degree re-dissolved by agitation. 



Analysis of the Chloride of Manganese. 



In an excellent paper published in the Philosophical Trans- 

 actions for the year 1812, Dr JOHN DAVY states the chloride of 

 manganese to be composed of 54 parts of chlorine and 46 of me- 

 tallic manganese. The atomic weight of manganese calculated 

 from these data is 3O67, a number which is considerably be- 

 yond the truth. Dr DAVY prepared the chloride by heating the 

 muriate in a glass tube communicating with the atmosphere by 

 a very small aperture. I have never failed by this method to 

 decompose some of the chloride, a circumstance which compli- 

 cates the analysis, and probably gave rise to Dr DAVY'S error. 



According to the analysis of M. ARFWEDSON (Annals of Phi- 

 losophy, N. S. vol. vii. p. 74.), the elements of the chloride of 

 manganese are in the ratio of 8403 parts of chlorine to 6677 of 

 manganese. This result, in the accuracy of which M. ARFWED- 

 SON does not place implicit confidence, would fix the equivalent 

 of manganese at 28*61. He prepared the chloride by placing 

 the carbonate of manganese in a spherical cavity blown in a ba- 

 rometer tube, transmitted over it a current of muriatic acid gas, 

 and heated the carbonate by means of a spirit-lamp as soon as 



