214 U. L. Wells — Composition of Pollucite and its 



analysis. Brush afterwards published a re-calculation* on this 

 assumption, which is given below under la. Since Plattner 

 used 0*5 gram, of substance for his analysis, the footing still 

 hardly does justice to his well-known skill as an analyst. I 

 have therefore made a new re-calculation, given under lb, 

 assuming that Plattner's platinichlorides contained enough 

 potassium to make an exact summation. This assumption is 

 warranted to a certain extent by the fact that all analyses of 

 pollucite since Plattner's give at least a trace of potash. This 

 calculation of the potash cannot be considered very exact, but 

 it is quite probable that a part of the excess shown by the 

 other re-calculation was due to the presence of this substance. 



la. 16. 



Plattner. 





Plattner, 







Re-calculated. Ratio. 



Re-calculatec 



I. 



Ratio. 



Si Q 46-20 



•770 or 4-64 



Si0 2 46-20 





•770 or 4-64 



Al a O, 16-39 

 Fe 2 3 0-86 



™l 1-166 or 1-00 

 •00o j 



A1 2 8 16-39 

 Fe 2 O s 0-86 



•161 j 

 •005 j 



•166 or 1- 



Cs 2 35-69 



•127 ) 



Cs 2 29-80 



•106 ) 

 •029 \ 

 •028 ) 





K 2 .... 



[-•155 or 0-93 



K 2 2-71 



•163 or 0-98 



Na 2 1-72 



•028 ) 



Na 2 1-72 





H 2 2-32 



•129 or 0-78 



H 2 G 2-32 





•129 or 0*78 



103-18 100-00 



The analysis which Pisani made on his discovery of caesium 



in the mineral, is as follows : 



2a. 



' 







Ratio with 





Pisani. 



Ratio. 



assumed correction. 

 (Na 2 = 2-n per cent.) 



Si0 2 



44-03 



•734 or 4-56 



•734 or 4-56 



A1 3 3 



Fe 2 3 



15-97 



0-68 



[HI \ -161 or 1-00 



j- -161 or. 1-00 



CaO 



0-68 



•012 ) 



I -168 or 1-04 



Cs 2 Of 



34-07 



•121 V-196 or 1-22 



Na 2 Of 



3-88 



•063 ) 



J 



H 2 



2-40 



•133 or 0-83 



•133 or 0-83 



101-71 



Pisani is very positive about the freedom of his caesia from 

 any considerable amount of potash, and he determined the 

 atomic weight of his alkali-metal in support of this ; hence it 

 is* scarcely allowable to re-calculate his analysis, as has been done 



* This Journal, II, xxxviii, 115. f With traces of K 2 and Li 2 0. 



