170 ACIDIFIABLE COMBUSTIBLES. 



Kemien, states the composition of silica as 

 follows : 



Silicon 49-7 or 0-988 

 Oxygen 50-3 1- 



100-0 1-988 = atomic weight of silicon. 



I do not know whether this new determination, 

 which approaches the ratio of equality much 

 more nearly than the number given by Berzelius 

 in his original paper, be the result of a new set 

 of experiments, or deduced from corrections 

 made upon the old ones. But the atomic 

 weight of silica deduced from it, is only dhrth 

 part less than 2. And I do not believe it to be 

 possible to operate in the way practised by Ber- 

 zelius and Stromeyer, without the risk of a still 

 greater error than yfeth part. I consider, there- 

 fore, this determination of Berzelius as a very 

 strong evidence in favour of 2 being the true 

 atomic weight of silica. 

 The com. XI. Among the minerals which are found in 



position of 



natural sin. regular crystals, and which have been subjected 

 to chemical analysis, there are a good many con- 

 taining silica united chemically, and conse- 

 quently in definite proportions with different 

 bases. If these minerals were perfectly pure, 

 an accurate analysis of them would give us suffi- 

 cient data for determining the atomic weight of 

 silica. It will be worth our while to examine a 

 few of these compounds, that we may see how 



