SILICON. 193 



quantity of silica, with thrice its weight of an- 

 hydrous carbonate of soda, and digested the fus- 

 ed mass in a small quantity of water, till the si- 

 lica assumed a flocky appearance. The whole 

 was then thrown upon a filter ; and the silica was 

 washed repeatedly with distilled water, till no 

 traces of soda could be found in the washings. 

 In two days the filter with the silica became dry 

 enough to be handled. I placed the filter on 

 several folds of bloating paper, on a table in the 

 middle of my laboratory, where it was allowed 

 to remain for six weeks, without being disturbed. 

 It may be necessary to mention, that the weather 

 during the whole time was uncommonly cold ; 

 and I have reason to believe, that the tempera- 

 ture of the room scarcely ever exceeded 60, if 

 it amounted to so much. When I returned to 

 Glasgow, on the 24th of June, the thermometer 

 in my laboratory stood at 57. The silica, to 

 the eye and the feel, appeared perfectly dry ; it 

 weighed 43*23 grains. By exposure to a red 

 heat, it lost 10*55 grains, and was reduced to 

 32-68. Now, 32-68 : 10-55 : : 4 : 1-2913 = wa- 

 ter combined with 4 silica. This exceeds 1-125 

 by 0-1663, which is rather more than fth of an 

 atom. This may be considered the greatest a- 

 mount of the excess which ever remains. I shall 

 now state the circumstances of the successful ex- 

 periment. 



A quantity of silica obtained, precisely as in 



Vor., I. N 



