420 Prof. F. von Kobell on Dianic Acid. 
niobie acid, now termed hyponiobic acid, and has called the. 
mineral formerly designated as tantalite by the name of nio- 
bite. According to my experiments, the same case occurs with 
the acids of the tantalite from Kimito, and of that from Tammela 
which I have examined. I will therefore name the latter, in 
which I first remarked the difference, after Diana, and term it 
Dianie acid; the element I shall name Dianium (D1), and the 
mineral from Tammela which contains this acid, Dianite. 
Besides occurring in the mineral here mentioned, this acid, 
though in a less pure state, appears to occur in the Greenland 
tantalite, im the pyrochlore-from the IlImen Mountains, and in 
the brown Wohlerite (I have not examined the yellow). I could 
only employ small quantities, however, of these minerals, and it 
was not in my power to carry out the requisite investigations in 
sufficient detail. A small fragment of yttrotantalite, professedly 
from Ytterby, gave the reaction of dianic acid; in another assay 
of a specimen, the specific gravity of which I ascertamed to be 
5°5, from the collection of the late Duke of Leuchtenberg, the 
acid proved to be tantalic acid. ‘The former assay refers there- 
fore to a different species, the specific gravity of which I could 
not determine. 
When combinations of this nature contain at the same time 
titanic acid, the latter is found in the residue of the potash-lye, 
in which it can be easily detected even when this residue con- 
tains also a small portion of dianic acid. The residue is boiled 
with concentrated hydrochloric acid and filtered, the filtrate, 
with a strip of tin laid in it, bemg then boiled longer. If no 
dianic acid, but tantalic acid is present, the liquor on becoming 
concentrated assumes a violet-blue colour, which on diluting 
with water is changed very characteristically to pnk. The fluid 
retains this latter colour for several days or longer. When the 
solution, in addition to titanic acid, contains a portion of dianic 
acid as well, the blue colour of the latter predominates ; on di- 
luting it in an open glass, the pink colour due to titanic acid 
makes its appearance in the course of a few hours, owing to the 
colouring of the dianic acid disappearing gradually. In this 
way I recognized the presence of titanic acid (as it had been esta- . 
blished previously by other methods) in sschynite, pyrochlore, | 
and euxenite. 
I cannot of course say whether my dianic acid is contained in 
all varieties, and from all the localities, of the above-named 
species; with respect to the tantalites from Tammela, it is indeed 
established that perhaps the majority of them contain tantalic 
acid. ‘The specific gravity should probably be particularly at- 
tended to. ‘The mineral from Tammela examined by me (dia- 
nite) has a specific gravity of 5°5, while the tantalites from that 
