OF ARTS AND SCIENCES. 35 



C 6 Hg — JN - Fo— Oi = F2 



next acts on another molecule of the base in the same way that the 

 fluoride of silicon did originally, forming 



Ho = AT — C S H 5 



H 2 = AJ 0--JN -F 6 5 ; 



C 6 II 5 — il — F 2 — Oi-F 



but it would seem that the acid nature of the silicon has been so 

 weakened by the introduction of two aniline molecules, that the atom 

 of fluorine left attached to the silicon cannot combine with the fluorine 

 attached to the nitrogen, and therefore this latter is saturated by 

 the more acid fluorine of a fluoride of silicon carrying only one aniline 

 molecule, thus : 



H 2 = AT - C 6 H S 



H 2 

 C 6 H 5 -±^| F 2 -k3i-F TF-Oi — F 2 -±T| --C 6 H 5 



- JN -Fo- Oi - F + F - Si-F 2 - N - 



H„=XT-C 6 H 5 

 .H? — JN — F 2 — fei — F F— fei — Fo — JN — a 



C 6 H^ — ±1 -_F 2 -Oi — F F_Oi — Fo — JlX --C B H 6 " 



If then the two atoms of fluorine remaining attached simply to silicon 

 are united, the formula given above is constructed. Our only reason 

 for joining these last atoms of fluorine is that it makes the molecule 

 more symmetrical, but it is also possible that they remain univalent. 



Turning next to the compounds formed by the union of the base 

 and fluoride of silicon in the proportion of two molecules of the for- 

 mer to one of the latter ; as has been already argued, it is necessary 

 to double the simplest formula which can be assigned to these sub- 

 stances, because they break up into the free base and the compound of 

 three molecules of the base to two of fluoride of silicon, and also be- 

 cause they can be formed by a reaction the reverse of this decompo- 

 sition. If, then, the formula discussed above is given to the trianiline 

 disilicotetrafluoride, the formula of the dianiline silicotetrafluoride 

 must be 



Ho = AT-C 6 H 5 



C 6 Hs — JN — F 2 — fei — F 2 — "VT — fch — F 2 — JN — C 6 H 5 ' 



C fi H s 



and the very slight stability of the substance can be explained by the 

 neutralization of the acid properties of the silicon and fluorine, already 

 alluded to, by the introduction of so many molecules of base, which 

 makes them hold the last molecule of the base with comparatively 



