F. A. Genth—American Vanadium Minerals. 83 
able to repeat my analyses with better and purer specimens ; 
but I now give the results of my analyses because there is no 
— of getting any more of this mineral, as will be seen 
rom a letter of Dr. Blake, dated San Francisco, April 5th, 
1876, in which he says, that the mine in which it occurs cannot 
be worked any farther until a tunnel has been run, and that 
it is quite uncertain when this will be done. 
Although by no means perfect, my results approach the 
truth and give a fair idea of the composition of the mineral, 
even if the evident admixture of other minerals, varying in the 
twelve per cent, does not permit one to calculate the atomic 
ratio of the constituents and establish the constitution of this 
i e is especially an uncertainty with reference to 
. 
species. ‘Ther I 
the quantities of silicic acid, alumina and potassa which belong 
only about six per cent of potassa, while fusion with calcic car- 
sibility of washing the precipitates completely without loss of 
vanadium. It was therefore always determined by the only 
method which I found to give fully reliable results—by titra- 
no matter whether only a very minute quantity of sulphuric 
is present, or a very large excess, the V,0, is completely 
