new Varieties of Vermiculites. 141 



over sulphuric acid, aud when subsequently heated to 100° for 

 twelve hours met with no appreciable loss. 



Mean. 



VII. 





(1) (2) (3) 

 [joss at 100° . . 3-48 3- 19 2*86 



(4) 



2-85 



2-28 



10-55 



15-86 16-05 15-66 



15-68 



15-81 



Loss at about 800°. 1 , OQO 100n f 2' 

 „ red heat .J 12 ' 82 13 39 \ll- 



VIII. 



09 2-44 

 09 10-77 



12-83 13-29 13-18 13-21 



The mean of (2), (3), and (4), which agree closely, is 13*23. 

 Reducing therefore Mr. C. E. Munroe's analysis of this same 

 variety to this basis, the following scheme represents the con- 

 stitution of the mineral dried at 100° : — 



99-45 



Si. 



Al. 



Fe. 



Fe. 



Mg. 



K. 



H. 



36-34 



7-54 



8-89 



1-14 



31-84 



•47 



13-23 



f 2-42 



•44 



•33 



■03 



1-59 



•01 



1-47 





^ 



; 



V 





, 





Ratio <! 1^63 



L 2-42 : 2-40 : 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 10*55 per cent, of its weight. The mean 

 of these values is 10*66; and regarding this as the water of 

 crystallization of the mineral, and reducing Mr. Munroe's ana- 

 lyses accordingly, we obtain the following results : — ■ 



Si. 



37*17 



2-48 



M. Fe. 



7'72 9-06 



•45 -34 



Fe. 



1-18 



•03 



Mg. 

 32-57 

 1-62 



K. 



•48' 

 •01 



H. 



11-24 



1-25 





•79 





1-66 







2-48 



: 



2-45 



1-25 



It would appear, then, that Hallite at 300° is in the same 

 condition of hydration which the other vermiculites examined 

 assume at or about 100°. Now, corresponding to this, there is 

 a very marked fact, indicated by the Tables given above, which 

 is worthy of special notice. Air-dried Jefferisite loses at 100° 

 about 10 per cent, of its weight, while air-dried Hallite loses 



