OP ARTS AND SCIENCES. 233 



diagonals, and in four jilanes constituting a vertical dome ; they ter- 

 minate at one end in two planes which form one-half of a klino dome. 

 Partially decomposed by large quantities of water and alcohol ; com- 

 pletely by a solution of a fixed alkali into the brown hydrate of man- 

 ganese and fluoride of the alkali. Soluble in acids ; partially soluble 

 in anhydrous ether. Insoluble in benzol and toluol. When the solu- 

 tion of this fluoride before crystallization is boiled, a dark brown 

 substance is deposited, which evolves HF vapor with suliihuric acid. 

 The crystals retain their crystalline form, but turn dark brown on 

 exposure to air or the temperature of 100°C. This brown sub- 

 stance is probably an oxyfluoride, in which two or a multiple of two 

 atoms of fluoride in the original fluoride are replaced respectively by 

 one or more atoms of oxygen. 



I can account for the formation of MnF^ instead of Mn^Fy from the 

 sesquioxide in no way except by assuming either that during the pro- 

 cess of evaporation the sesquifluoride breaks up into tetrafluoride, or 

 that the existence of a sesquifluoride is impossible. 



Double Fluoride of Peroxide of Manganese and Ijptassium, 3fnF^. 2KF. 

 — To a moderately concentrated solution of MnF^, potassic fluoride dis- 

 solved in water is added in excess. Care must be taken that the solu- 

 tion of potassic fluoride is concentrated, otherwise the tetrafluoride 

 of manganese will be decomposed. A rose-colored precipitate imme- 

 diately separates, which when dried at 100°C. presents the following 

 composition : — 



100.00 100.02 



The analysis was conducted in the same manner as that of the for- 

 mer double fluorides. 



Properties. — Rose colored. Under the microscope exhibits traces 

 of crystalline structure ; form indistinct. Decomposed by water, but 

 not so readily as the tetrafluoride. Soluble in acids. Stable in air. 

 Fuses to a blue mass, which on cooling resumes its original color. 



A fluoride of manganese was prepared, in which the ratio between 

 manganese and fluorine was found to be 1 : 8 respectively. This fluo- 

 ride, however, requires further study ; and it is hoped that, if the above 

 ratio shall be proved beyond question to exist, the exact relation and 

 disposition of the atoms will be determined. 



