OF ARTS AND SCIENCES. 29 



statement made in a preliminary notice of this work, that a compound 

 was formed under these conditions was incorrect, the diphenylamine 

 used for that first experiment being impure. If, however, fluoride of 

 silicon is passed through a solution of diphenylamine in benzol, a white 

 crystalline precipitate is deposited slowly, which was washed with ben- 

 zol, dried at 100°, and analyzed with the following results. 



I. 0.4356 grm. of the substance gave 0.0695 grm. of silicic dioxide 

 and 0.2141 grm. of sodic fluoride. 

 II. 0.4192 grm. of the substance gave 0.1986 grm. of sodic fluoride. 



Calculated for Found. 



((C G II 5 ).,NH) 3 (SiF 4 ) 2 . I. II. 



Silicon 7.83 7.44 



Fluorine 21.26 22.23 21.43 



Properties. — It forms thick white needles, which are decomposed by 

 heat into fluoride of silicon and diphenylamine. When treated with 

 water a precipitate of diphenylamine separates, and the filtrate con- 

 tains fluosilicic acid. A quantitative study of the reaction gave the 

 following results. 



I. 0.8135 grm. of the substance gave 0.5686 grm. of diphenylamine 

 and 0.3040 grm. of potassic fluosilicate. 

 II. 0.4934 grm. of the substance gave 0.3476 grm. of diphenylamine. 



In the calculated percentages given below, it is assumed that all the 

 diphenylamine is separated by the action of the water, and that four 

 molecules of the compound will yield five of potassic fluosilicate, i. e. 

 that the reaction with water is analogous to that of the corresponding 

 aniline compound. 



Calculated. Found. 



I. II. 



Diphenylamine 70.91 69.89 70.44 



Potassic fluosilicate 38.50 37.37 



If, as the numbers obtained seem to show, the reaction is similar to 

 that of the trianiline disilicotetrafluoride with water, silicic acid should 

 have been set free; but no trace of it could be discovered, the solution 

 being free from any precipitate except the diphenylamine, and upon 

 evaporation to dryness leaving no residue, while that silicic acid had 

 not been carried clown by the diphenylamine was shown by burning 

 it, and also by dissolving it in benzol. In neither case did it leave 

 a residue. "We have not been able to find any explanation for this 

 curious observation, or to account for the formation of fluosilicic acid 



