OF ARTS AND SCIENCES. 229 



with sulphuric acid in a platinum retort, a yellow vapor, purple in 

 moist air, is evolved. This fluoride having the above ratio cor- 

 rodes glass, and in so doing is resolved into (SiFJ silicic fluoride and 

 (H^MnoOg) permanganic acid. Chloride of calcium exposed to the 

 yellow vapor evolves chlorine. The compound is absorbed by water, 

 forming a purple solution, which contains hydrofluoric and perman- 

 ganic acids. When the solution is evaporated in air, it evolves oxygen 

 gas and hydrofluoric acid vapor, and leaves a brown residue from which 

 water dissolves manganous fluoride, leaving a black insoluble basic salt. 

 The solution dissolves copper, mercury, and silver, with formation of 

 the corresponding fluorides. 



* The tetrafluoride of manganese, MnF_,, is produced in solution : 

 (1) when hydrofluoric acid is allowed to act on an ethereal solution of 

 MnCl^ ; (2) when the acid acts on MuOj, in which case all the acid 

 employed cannot be neutralized. The solution decolorizes indigo, and 

 produces colors with anilin and naphthylamine ; but may be preserved 

 in the presence of glucose and gum-arabic. The substance dissolves 

 in alcohol ; decomposes in presence of much water, especially when it 

 is alkaline, peroxide of manganese being formed. When potassic flu- 

 oride is added to the preceding solution, a rose precipitate is formed, 

 which when dried at 100°C yields the formula MuF^2KF. Ammonic 

 fluoride yields a compound of analogous composition. The alkaline 

 fluorides appear to give stability to the tetrafluoride. The potash salt 

 melts, and after lengthened fusion the salt MnF^.iKF is obtained. 

 The solution of tetrafluoride precipitates an alcoholic solution of 

 plumbic acetate. None of these compounds are crystalline. If to a 

 boiling solution of potassic fluoride or ammonic fluoride perchloride 

 of manganese is gradually added, a red powder comes down, the consti- 

 tution of which is represented by the formula MnOF,. This oxy- 

 fluoride and the preceding tetrafluoride are soluble in anhydrous ether. 

 Under the same conditions as above the sesquifluoride of manganese 

 acts in a similar manner, the properties of the compounds thus formed 

 being generally the same. With K^Mn^O^ and hydrofluoric acid, either 

 one or other of the following bodies is obtained: MnF^. 2KF ; Mn^ 

 F,0H-2KF. 



t When Mn02 is treated with hydrofluoric acid, brown crystals are 

 sometimes deposited, especially when the mixture has been digested 

 with the aid of heat. The crystals when dried on paper furnish the 



* Bull. Chim. Soc. viii. 4.8, NLkles. 

 t Ibid. 



