SILICON. 195 



retains a certain degree of transparency, and is 

 not quite destitute of its gelatinous form. In 

 this state it is a compound of 



1 atom silica . 2 



13 atoms water . 14-625 



16-625 



So that in this hydrate, though apparently quite 

 dry and solid, more than fths of the whole weight 

 is water. 



3. If we allow this solid mass of ielly to dry Hydrate of 



_ . . J 



in the open air, without breaking it m pieces, it 

 gradually assumes a yellowish colour, somewhat 

 similar to that of gum-arabic ; and even after an 

 interval of several years, it is still semi-transpa- 

 rent. In this state it is very brittle, but hard, 

 and breaks with a conchoidal fracture. It has a 

 certain resemblance to common flint ; or rather 

 it may be stated as an intermediate looking sub- 

 stance between flint and calcedony. This hy- 

 drate of silica, when successfully prepared, is 

 composed of 



1 atom silica . 2 



1 atom water . 1-125 



I have succeeded in preparing this hydrate, only 

 by leaving it for a very long time (in general 

 several years) in a warm and dry room. I shall 

 state the result of an experiment made during 

 the summer of 1823. A quantity of gelatinous 



N 2 



