230 PROCEEDINGS OF THE AMERICAN ACADEMY 



formula MngFg. lOH^O. The substance is soluble in a small quantity 

 of water, but decomposed by an excess into the brown oxide of man- 

 ganese. Its solution forms a red precipitate with potassic fluoride. 

 Dissolves silver, and is decolorized in passing to the state of proto- 

 fluoride. 



* A fluosilicate of Mn has been artificially prepared, represented by 

 MnSiFg. 7H^0. Crystallizes in long six-sided prisms, and rhombo- 

 hedrons. Color very light red. When heated, it first gives off seven 

 molecules of water, then gaseous SiF^, leaving MnFg of the same form 

 as the original crystals. Easily soluble in water. 



Manganous Fluoride, MnF\ — Owing to the difficulty of obtaining 

 mangauous oxide free from higher oxides, it was found more practi- 

 cable to prepare this fluoride by dissolving the white manganous car- 

 bonate in hydrofluoric acid. The resulting liquid was then evaporated 

 on the water bath to dryness. The fluoride rendered anhydrous by 

 drying at lOO^C. gave by analysis : — • 



Found. At. Ratio. Theory. 



Mn 58.G8 LOG 59.14 



F3 40..57 2.13 40.86 



99.25 100.00 



Manganese and fluorine were separated by decomposition with a con- 

 centrated solution of potassic hydrate, the hydrate of Mn thus formed 

 converted into pyrophosphate, and the fluorine in the filtrate precipi- 

 tated as calcic fluoride. 



Properties. — Color white, shading faintly into pink. Structure crys- 

 talline, but indistinct. Insoluble, or sparingly soluble, in water and 

 alcohol. Decomposed by the fixed alkalis and their carbonates. Dis- 

 solves in mineral acids, but in no case evolves hydrofluoric acid vajjor ex- 

 cept when treated with concentrated sulphuric acid. (It may be well to 

 notice once for all that concentrated sulphuric acid invariably decom- 

 poses fluorides with evolution of hydrofluoric acid.) Dissolves in water 

 containing free HF. Not decomjjosed by water, or by exposure to 

 air. At red heat fuses to a dark brown mass with loss of fluorine. 



Manganous Fluoride and Hydrofluoric Acid, MnF.^. 2)HF. ^dH.^0. 

 — When the anhydrous MnFg is dissolved in aqueous hydrofluoric 

 acid, and the solution evaporated in vacuo over snlphuric acid, crystals 

 containing free hydrofluoric acid are deposited. Also prepared directly 



* Gmelin, vol. iv. Mn. Berzelius. 



