112 Penfield and Foote — Composition of Tourmaline. 



The agreement between the corrected analyses of Rammels- 

 berg and those of the other investigators is very remarkable, 

 and the ratios of Si0 2 to the total equivalent of hydrogen 

 atoms approximate closely to 4 : 20 ( the average is 4 : 20*1). 



Seven complete analyses are also given by Rammelsberg 

 and to them corrections for water have been applied, while 

 the errors of the analysis have been distributed upon the 

 Si0 2 and B 2 3 . The results are given below, together with 

 Rammelsberg's figures for SiO a , B 2 3 , H 2 and loss on ignition : 



No. of Analy 



sis, 2 



5 



22 



24 



, -d ( Si0 2 . 

 Sl]B 9 0,. 



..[36-53] 



[36-37] 



[34-82] 



[34-87] 



..[10-66] 



[10-61] 



[10-16] 



[10-17] 



° £ A1 2 3 



.. 32-90 



33-15 



35-46 



33-35 



FeO . 



.. -66 



2-88 



13-17 



11-95 



MnO. 



._ 







•28 



1-25 



MgO. 



.. 11-79 



10-89 



1-52 



•63 



CaO . 



.. 125 



•77 











Na 2 



.. 2-37 



1-52 



•98 



1-75 



K 2 0_ 



.. '47 







09 



•40 



, r^j ) Li 2 . 



_ _ 











•84 



°1 [H 2 0. 



.. 3-00 



3-81 



3-28 



4-31 



°£ )V-~. 



.. -64 

 100-27 



100-00 



•41 

 10017 



•82 





100-34 



. fSi0 2 . 



.. 33 09 



38-33 



36*11 



36-22 



"fib-: J B 2 3 - 

 g fl ]H 2 0. 



.. 11-15 



9-86 



11-64 



10-65 



.. 2-05 



2-81 



1-26 



2-21 



LIga... 



l 293 



3-49 



1-82 



2-98 



29 



31 



33 



[35-49] 

 [10-35] 



[36-03] 



[36-02] 

 [10-51] 



[10-51] 



42-63 



4405 



36-80 







_ _ _ _ 



6-38 



194 



•92 



•78 



•39 



•20 



1-88 



•45 









2-60 



2-00 



2-47 



•68 



1-30 



•47 



1-17 



1-22 



•72 



3-61 



337 



3-65 



1-18 



•70 



•55 



100-49 



10030 



10023 



38-19 



38-85 



38-46 



997 



952 



9-73 



200 



2-41 



231 



3-61 



337 



294 



A comparison of the corrected analyses with the figures 

 given by Rammelsberg indicate that B 2 3 has been determined 

 with a good degree of accuracy. His water is always low 

 and his silica high. The ratios of Si0 2 to the total equivalent 

 of hydrogen atoms in the corrected analyses are as follows : 



No. 2 No. 5 No. 22 No. 24 No. 29 No. 31 No. 33 

 Ratio 4:20-0 4:20*3 4:20-4 4:20*7 4:21*8 4:21*4 4:20*2 



Two of the hydrogen ratios are very high ; four of them 

 approximate closely to 4:20*0; the average is 20*7. 



The results obtained by applying similar corrections to 

 the remaining twenty analyses are given in the table on page 

 113, together with Rammelsberg's figures for Si0 2 , H 2 and 

 loss on ignition. In the last column the ratios of the total 

 equivalent of hydrogen atoms are given, one quarter of the 

 corrected Si0 2 being taken as unity. 



The ratios of the silica to the hydrogen atoms in these 

 twenty analyses exhibit a rather wide variation, from 4 : 18*7 

 to 4 : 21*8. The average, however, is 4 : 20*4, and the average 

 for all of his thirty-four analyses is also 4 : 20*4, or approxi- 

 mately 4 : 20. 



