452 Clarke and Schneider — Experiments upon the 



Art. LYII. — Experiments upon the Constitution of the Nat- 

 ural Silicates ; by F. "W. Clarke and E. A. Schneider. 



[Continued from p. 415.] 



6. The Vermiculites. 



Of this interesting group two examples were studied ; the 

 well-known, typical jefferisite from Westchester, Pennsylvania, 

 and the kerrite from near Franklin, Macon County, North 

 Carolina. The latter, presented to us by Prof. F. A-. Genth, 

 was part of his original sample, and the analysis agrees well 

 with Chatard's. Analyses as follows, on air -dried material. 



Jefferisite. Kerrite. 



Si0 2 34-20 38-13 



Al 2 O s 16-58 11-22 



Fe„0 3 7-41 2-28 



FeO "... 1-13 -18 



NiO -48 



CoO trace 



MgO 20-41 27-39 



H a *0 (ignition) 21-14 20-47 



100-87 100-15 



H„0 over H o S0 4 10-56 9-62 



H 2 "0 at 105° .... -24 



H.,0 at 250°-3()0°... 4-20 4-10 



H 2 at red heat 6-18 6-27 



H„0 at white heat _. -20 24 



Here the water falls into three sharply defined parts ; one, 

 lost by drying over sulphuric acid, very loosely held ; a second, 

 water of crystallization, lost below 300° ; and the third, consti- 

 tutional water. 



By dry hydrochloric acid gas the minerals were little affected. 

 The' data are as follows, for 383°-412.° 



Jefferisite. Kerrite. 



Hours heated 32 32 



MgO removed 3*98 3'15 



R^Og removed 1-38 '09 



By aqueous hydrochloric acid both of the vermiculites were 

 easily and completely decomposed. By ignition, however, 

 with fusion in the case of the kerrite, they were split up into 

 soluble and insoluble portions. In the kerrite, after fusion, 

 only 10-64 per cent of magnesia and 3 75 of sesquioxides were 

 removable by aqueous hydrochloric acid, but nothing more 

 could be determined for want of material. The jefferisite, 

 after strong ignition, and subsequent digestion with the acid 



