228 PROCEEDINGS OF THE AMERICAN ACADEMY 



XIX. 



CONTRIBUTION TOWARDS THE HISTORY OF THE 

 FLUORIDES OF MANGANESE. 



By W. H. Melville. 



Presented by the Corresponding Secretary, June 14th, 1876. 



The investigation described in this jiaper was undertaken with a 

 view to the re-examination of the fluorides of manganese. Many in- 

 vestigations have been made upon this subject during this century, and 

 necessarily a large amount of fact has been accumulated. 



* Berzelius noticed that, on the evaporation of a solution of man- 

 ganous carbonate in hydrofluoric acid, ill-defined crystals were obtained, 

 which dissolved in water only when containing an excess of acid. This 

 amethyst-colored substance he called the proto-fluoride of manganese. 

 He furthermore prepared a fluoride of manganese and potassium by 

 double decomposition of a solution of manganous sulphate and fluoride 

 of potassium. Similarly the soda salt was precipitated. These double 

 fluorides were described as white precipitates, insoluble in water, and 

 soluble in acids. 



t When hydrated sesquioxide of manganese is dissolved in hydro- 

 fluoric acid and the solution left to evaporate spontaneously, dark 

 brown prisms crystallize out, which dissolve completely in small quan- 

 tities, but are decomposed by excess of water. When this decom- 

 position ensue*, a basic salt is deposited, while an acid salt remains in 

 solution. A part of the former is redissolved on cooling, if free acid 

 is present. Ammonia precipitates pure hydrated manganic oxide. 

 (Berzelius.) 



t A fluoride of manganese has been prepared, in which the Mu and 

 F exist in the ratio 1 : 7 respectively. When a mixture of two parts 

 potassic manganate or permanganate and one part fluor-spar is digested 



* Gmelin, vol. iv. Manganese. 



t Ibid. 



J WGhler, Fogg. 9, 619; Dumas, Ann. Chim. Phys., 3G, 82. 



