of Schorlomite. 47 
attacked with sulphuric acid. The solution was effected very 
slowly, and chlorohydric acid was added, which was after- 
wards expelled by evaporating the solution. The removal of 
the sulphate of lime which remained undissolved when the 
solution was diluted with a large quantity of water, required 
long washing. The results show, however, that the attack - 
was perfect, and the silica obtained was perfectly pure. 
The difficulty of attacking this mineral completely, by sul- 
phuric acid alone, seems much greater than that experienced 
by Rose in his analyses of sphene, since he recommends this 
method of attack as preferable to any other, in case all the 
ingredients of the mineral are to be determined. The tedious 
operation of repeatedly heating with sulphuric acid, and the long 
continued washing necessary to remove the whole of the sul- 
phate of lime, render this a very undesirable method in any 
case, and in the analysis of the ferrotitanite it would have 
been impossible to effect a complete decomposition of the 
substance, had not chlorohydric acid been added ; since, after 
the substance had been several times heated with concentrated 
sulphuric acid alone, the solution being each time largely dilu- 
ted with water, and allowed to settle before being poured off, 
a very considerable portion of the mineral remained unat- 
tacked. Analysis I. shows that when the attack is made by 
means of strong chlorohydric acid, even when the solution 
was heated nearly to the boiling-point for some hours, the 
quantity of titanic acid remaining in combination with the 
silica was not by any means so large as to lead to very incor- 
rect conclusions as is the case with the silica obtained from an 
analysis of sphene by the same method. By a careful diges- 
tion of this mineral, at a low temperature, with chlorohydric 
acid, Rose obtained 51. per cent. of residue, instead of 30.9 
per cent. required by the formula. 
The method of attack by bisulphate of potash might be 
adopted with advantage, were it not that the silica enters into 
an insoluble combination with a portion of the sulphate of 
potash, so that in an analysis executed in this way, the 
quantity of silica obtained is always considerably too large. 
