108 Prof. Louis Henry on the Polymerization 



Oxygen is an element endowed in reality, in spite of appear- 

 ances to the contrary, with great power of volatilization. It 

 forms oxides which are gaseous, or at least very volatile, with 

 elements which are relatively but little volatile, as sulphur ; 

 or which are even entirely fixed, as carbon and osmium. To 

 these normal oxides, which are regular at least in their physical 

 properties, there correspond chlorides which are notably less 

 volatile, as in the case of those of carbon : — 



C0 2 gaseous, b. -p. — 78. 

 CC1 4 liquid, b.-p. + 76. 



That being so, it may be affirmed that many of the regular 

 metallic oxides w 7 hich correspond to the chlorides should be 

 gaseous at the ordinary temperature, or at least very volatile. 

 This should be especially true of Si0 2 , A1 2 3 , &c; for SiCl 4 is 

 a liquid boiling at 58°, and A1 2 C1 6 a solid volatile below 100°. 

 In reality, however, these oxides, which I regard as polymers, 

 (Si0 2 ) n and (A1 2 3 )^ are fixed solids. Organic chemistry 

 furnishes examples of the relationships which exist in poly- 

 mers between the volatility and molecular weight, thus : — 



Difference. 

 | 88°-5 





Molec. 



wt. 



B.-p. 



Ethylene oxide C 2 H 4 

 Ethylene dioxide (C 2 H 4 0)2 

 Aldehyde C 2 H 4 

 Paraldehyde (C 2 H 4 0) 3 



. 44 

 . 88 

 . 44 

 . 132 



liquid 

 liquid 

 liquid 

 liquid 



13°-5 

 102 



21 

 124 



} 



103' 



C 



We thus see what is the difference in volatility between 

 bodies of which the molecular weight in the state of gas is 

 simple, double, or treble. 



Now between a body which ought to be gaseous or very 

 volatile, such as Si0 2 , and a fixed body, such as silica really 

 is, there is a difference which cannot be compared to that 

 which separates (as regards volatility) ethylene oxide and 

 aldehyde from their polymers. If silica is, as I believe, a 

 polymer (Si0 2 ) w , then the value of n should be considerable, 

 and the molecular weight therefore very high. We come to 

 the same conclusion if we consider the examples which are 

 furnished by the relative densities of the chlorides and oxides of 

 the radicals C„H 2n and those of their polymers. As already 

 remarked above, the density of the chlorides is higher than that 

 of the corresponding oxides, whereas the densities of the poly- 

 mers of the latter rise, approaching those of the chlorides, and 

 even going beyond. The densities of the metallic oxides are 

 often considerably greater than those of the chlorides. If we 





