Section B. 



CHEMISTRY, METALLURGY, AND 

 MINERALOGY. 



1.— RECENT METHODS OF ROCK ANALYSIS. 



By P. G. WYKEHAM BAYLY, A.S.A.S.M., Government Metallurgical 

 Chemist. Melbourne. 



Since tlie work of the clieniists of U.S. Geological Survey has become 

 more generally known the quality of rock analysis has been steadily 

 improving. Wherever the general scheme, as developed by Clarke and 

 Hillebrand, has been adopted it has proved an incentive to ever-in- 

 creasing accuracy and carefulness, and as a result the standard of the 

 work done has been raised. Hillebrand showed the weakness of an 

 analysis, no matter how much time and care had been spent upon it, 

 which ignored certain features essential to its value from the point of 

 view of the petrographer, e.g., the omission of separation of the two 

 oxides of iron, failure to recover completely the silica, neglect of probable 

 and almost certain presence of titanium and other elements. He 

 showed, too, by working with extreme care for each base and blocking 

 every possible source of loss, how necessary were certain precautions 

 if good results were to be obtained. He demonstrated the presence in 

 nearly all igneous rocks of appreciable amounts of elements which, in 

 general, are completely ignored, but which may very possibly have 

 distinct significance to the geologist. Even the undoubted presence of 

 ■" traces " may quite possibly be of extreme importance in determining 

 a comparison of rocks. 



The principal object of this present paper is to urge all chemists 

 in the different States who are called upon to perform rock analyses to 

 take up their task with more regard to uniformity and agreement of 

 method, so that the results may be used comparatively one with another, 

 and so make possible an iiltimate combination of the results of analyses 

 of the rocks of Australia for the purpose of classification. It is intended 

 to deal only with the determination of a few of the important elements 

 upon which variations of methods have suggested themselves ; for the 

 remainder, the procedure of Hillebrand is followed as completely as 

 possible. 



Nothing better than the lines laid down by that chemist can be 

 suggested, and for the general discussion of his principles I would simply 

 refer to his own published work.(a) I propose, however, to suggest a 

 few modifications in some of his methods of procedure which I have 

 found by practice to recommend themselves. 



Preparation op Sample. — An amount of 25 grammes of repre- 

 .sentative chips of the rock is broken down in a diamond mortar, and 



*a Bulletin of Geological Survey, No. 17G. 



