PROCEEDINGS OF SECTION B. 



331 



lent to the gain through oxidation is determined by comparison with 

 the original FeO figure, and this is added to the total loss on ignition. 

 The carbon dioxide is separately determined by the gravimetric 

 method. 



Table VIT. 



Average — 



Ignition loss method 

 Penfield method 



.0279 

 .0293 



Any organic matter present would be included in the final figure, 

 obtained by the ignition loss method. The chief ground of objection 

 raised to this method is the influence of FeO and CO2, and the above 

 example shows that with the precaution suggested the results are quite 

 good. 



The complete analysis of the rock was as follows, viz. : — 



Table VIII. 



SiO„ 52.90% 



AI263 16.49 



FeaOs 0.78 



FeO 4.86 



MgO 2.92 



CaO 7.14 



NaoO 2.58 



KoO 1.73 



H„0+ 2.79 



HoO- 1.72 



COo 4.65 



TiO'o 1 . 10 



Mnd trace 



Li„0 n. d. 



P.Os 0.25 



SO3 nil 



CI traco 



99.91 % 



