OCCURRENCE OF TINGUAITE AT KOSCIUSKO, N.S.W. 



367 



Composition oj portion decomposed by HCl. 





I. 



III. 



IV. 



Si0 2 



... 51-84 



53-90 



5316 



A1A ... 



... 28-74 



26-86 



27-08 



Fe 2 3 ... 



... 2-68 



3-02 



274 



CaO 



... 1-83 



1-92 



1-85 



K 2 



... 1-98 



1-77 



2-45 



Na 2 ... 



... 12-93 



12-53 



12-72 



100-00 100-00 10000 



A few remarks with regard to the analysis are appended. The 

 water above 100° 0. was determined by heating the powdered 

 rock in a hard glass tube, the water being collected and weighed 

 in a small bulb-tube containing calcium chloride. The mass after 

 fusion with sodium carbonate was in all cases of a bright green 

 colour, dissolving in acid to a pink-coloured solution. The 

 iron and alumina were separated from the manganese by pre- 

 cipitation as basic acetates, and the manganese determined by 

 the method described in Bulletin 148 of the United States 

 Geological Survey by W. F. Hillebrand. The ferrous iron was 

 determined by treating the rock with hydrofluoric and sulphuric 

 acids in an atmosphere of carbon dioxide. 1 We are indebted to 

 Mr. Mingaye, Assayer and Analyst to the Mines Department, 

 Sydney, for a sample of hydrofluoric acid of almost absolute purity. 



The portion of the rock decomposed by hydrochloric acid was 

 attacked in the following manner : 1 gramme of the finely powdered 

 rock was digested with strong hydrochloric acid (sp. gr. 1*1) for a 

 few minutes. The solution was diluted with about four times 

 its volume of water, boiled for 10 minutes, and filtered. The 

 filtrate, which contained dissolved Si0 2 , was evaporated to dryness, 

 ignited on the water-bath and taken up with hydrochloric acid, 

 the separated Si0 2 being filtered off, ignited and weighed ; the 

 iron, alumina, lime and alkalies being determined in the filtrate. 

 The residue originally insoluble in hydrochloric acid and which 



1 J. H. Pratt— Amer. Journ. Sci. (3) 48, 149. 



