540 FERGUSON: OXIDATION OF LAVA 



at that time by the writer indicated that the lava was not ap- 

 preciably attacked by water vapor at temperatures in the neigh- 

 borhood of iooo°C. and that the presence in the lava of so much 

 iron in the ferrous condition was not at variance with the water 

 content of the emanations observed by Day and Shepherd.^ 

 These experimental results, obtained in 191 2 and 1913, are now 

 presented as a matter of record. 



Most of the writers who have speculated upon the role that 

 water plays in the chemical reactions which take place in the 

 volcanic vent during an eruption have based much of their 

 speculation upon the equation' 



3FeO + H2O Z^ Fe304 + H2 + 15400 cal. 



This equation must not be taken too literally, because recent 

 investigations^ have indicated that the action of steam upon a 

 ferrous iron oxide at high temperatures gives rise to a "mag- 

 netite" of variable composition. The actual composition ob- 

 tained is dependent upon the temperature.^ 



An analysis of a fresh flow of Kilauean lava" shows 9.28 per 

 cent FeO and 1.92 per cent Fe203. The ratio of ferrous to ferric 

 iron in this rock is much greater than the ratio in magnetite 

 (1:2) and, were we deaUng with the pure iron oxides only, 

 this fact might be used as an argument against the presence of 

 a preponderance of water vapor in the gas phase. The lava, 

 however, does not contain ferrous oxide as a separate phase. 

 The ferrous iron exists mainly in the silicate minerals and the 

 glass, together with a little in the traces of magnetite which are 

 probably present, although microscopic examination does not 

 show appreciable amounts of Fe304. The equations which would 



2 Day and Shepherd, Loc. cit. Shepherd, E. S., Bull. Hawaiian Volcano Obs. 

 7 (July). 1919. 



* Chamberlin, R. T., Carnegie Publication No. io6: 66. 1903. R. A. 

 Daly, Igneous rocks and their origin, p. 272. 1914. Von Wolff, Vulkanisnius, 

 I, p. 116. 1914. 



^ Htlpert, S., and Beyer, J., Ber. deutsch. Chem. Ges. 44: 1618. 1911. 



* The whole problem of the various oxides of iron is an exceedingly difficult one 

 to study experimentally and much yet remains to be done before the problem can 

 be considered satisfactorily solved. 



* Ferguson, J. B., Am. Journ. Sci. 37: 400. Analysis B. 1914. 



