OF ARTS AND SCIENCES. 



459 



(3.) 



Ratio 



38.04 18.39 

 2.56 107 



8.84 2.33 21.34 

 .33 .06 1.07 



1.40 



1.13 



2.56 



2.53 



10.51 99.45 

 1.17 



1.17 



Table VII. gives the percentages of water found in air-dried speci- 

 mens of the green variety of Hallite, and Table VIII. gives the 

 percentages of water found in the same specimens dried at 100°. In 

 analysis (4) the mineral was dried for three months over sulphuric 

 acid, and when subsequently heated to 100° for twelve hours met with 

 no appreciable loss. 



(Mean.) 



15.86 16.05 15.66 15.68 15.81 



Loss at about 300° 

 „ red heat 



VIII. 



12.82 13.29-1 ^-^^ ^-^"^ 

 (11.09 10.77 



12.83 13.29 13.18 13.21 



The mean of (2), (3), and (4), which agree closely, is 13.23. Re- 

 ducing therefore Mr. C. E. Munroe's analysis of this same variety to 

 this basis, the following scheme represents the constitution of the 

 mineral dried at 100°. 



99.45 



Ratio 



1.47 



It will be noticed, however, that in the case of Hallite there appears 

 to be a constant condition of hydration at about 300°, and that in two 

 experiments the air-dried mineral lost above this temperature 10.77 and 



