Constitution of certain Micas and Chlorites. 379 



The molecular ratios deducihle from these analyses, reject- 

 ing water given off below 300°, and the chromite contained in 

 the serpentine, are as follows : 





A. 



B. 



C. 



JD. 



E. ' 



SiO, 



•281 



•516 



•500 



•709 



•736 



R,o, 



•430 



•192 



•211 



•022 



•374 



RO 



•759 



•874 



•861 



1-022 



•004 



R,0 

















•124 



H o 



•247 



•713 



•714 



•675 



•230 



F 















•050 



Hence we get the following empirical formulae, in which all 

 R"'=A1, all K"=Mg, etc. 



Waluewite, Al B9 Mg 76 H B0 (SiO 4 ) !I8 O IT4 



Clinochlore, Al S8 Mg 87 H IM (Si0 4 ) M I1 , 



Leuchtenbergite, Al 42 Mg 8fi EI 143 (SiO 4 ) 50 O 121 



Serpentine, Al 4 Mg 10 ,H m (SiO 4 ) 71 O„ 



Mica, Al 75 K 25 H 46 (Si0 4 ) 74 9 F 5 



The last of these minerals is evidently an ordinary musco- 

 vite, possibly a little altered, and will receive no further con- 

 sideration in this paper. The other minerals were examined 

 more in detail, with very interesting results. As in our pre- 

 vious work, all experiments upon each mineral were made upon 

 a uniform sample of the powdered material, so that direct 

 comparisons with the analyses might be possible. The analyses 

 themselves agree closely with the published analyses made by 

 others, and are noteworthy only in the fractional determina- 

 tions of the water. 



Towards dry, gaseous hydrochloric acid, at the temperature 

 interval 383°-412°, the minerals under investigation were 

 somewhat refractory. From the waluewite, after nine hours 

 heating in the gas, only 0*22 per cent of lime and (HO per cent 

 of magnesia were extractable by water. Hence we may fairly 

 infer that the species contains practically no -Mg-OH groups, 

 a result which is in accordance with theory, as will be seen 

 later. The chlorites and the serpentine, however, gave anoma- 

 lous results, as follows ; there being two experiments on each. 



Clinoclildre. Leuchtenbergite. Serpentine. 



Hours heated, 8£ 13 16^ 18£ 28J J7_ 



MgO extracted, 7134 5 T 48 7"33 5^62 ^66 2 T 66 



In each case the heating was continued to constant weight, 

 but the amount of action was much less than in the American 

 clinochlore and serpentines which we formerly investigated. 

 The leuchtenbergite behaves much like the impure material 



