SILICON. 183 



An atom of oxide of zinc, as has been proved in 

 the first chapter of this work, weighs 5-25. Now, 

 if silica weigh 2, and this mineral be a silicate of 

 zinc, we have 2 : 5-25 : : 24-893 : 65-344 = ox- 

 ide of zinc united to the silica. 



The oxide of zinc in the mineral exceeds this 

 quantity by 1-493 grain, according to Berze- 

 lius' analysis. Let us see how far this excess 

 can be accounted for. 



1. The water in the mineral amounts, we see, 

 to 7*460 per cent. Now, an atom of water 

 weighs 1-125, and an integrant particle of an- 

 hydrous silicate of zinc 7'&5 5 and 7*%5 : 1-125 

 : : 90-237 (the silicate of zinc per cent.) : 14-002 

 = quantity of water, supposing the silicate to 

 contain 1 atom water. Now, 14*002 being near- 

 ly double the quantity of water actually contain- 

 ed in the mineral, it is obvious that the silicate 

 of zinc can contain only half an atom of water, 

 which, in 100 parts of the mineral, amounts to 

 7*001. The quantity of water in the mineral is 

 7-460, which exceeds 7-001 by 0-459. 



2. Besides the silica, then, there are two other 

 substances contained in the mineral, both of 

 which have the property of uniting to oxide of 

 zinc. There are 0-459 grain of water, and 0-45 

 grain carbonic acid. 



Now, 0-45 grain of carbonic acid requires 0-86 

 grain of oxide of zinc to form anhydrous carbo- 

 nate ; but carbonate of zinc usually contains li 



