Prof. F. von Kobell on Dianic Acid. 423 
as to the possible cooperation of the tungstic acid in the produc- 
tion of the blue colour alluded to, the acid of the dianite from 
Tammela was purified with the utmost care by the process sug- 
gested by H. Rose. The filtered acid was dried down till it was 
capable of being readily reduced to powder. I took 0:5 grm, 
of it, which was triturated with 1:5 grm of carbonate of pot- 
ash and then with 0°5 grm. sulphur. I fused the mixture in a 
covered porcelain crucible over a gas-lamp, dissolved the mass 
in water, and after decantation transferred the acid remaining 
into a close glass vessel with sulphuretted hydrogen, which I 
agitated well, leaving it thus for twenty-four hours. The liquor 
was then decanted twice, and the residue boiled with diluted 
hydrochloric acid and well washed ; and lastly, the metallic acid 
was attacked a second time with hydrate of potash in a silver 
crucible, precipitated with hydrochloric acid and filtered. <A tin- 
foil funnel was filled, as above described, with the acid, and a cubic 
inch of concentrated hydrochloric acid having been poured into 
it, the fluid was maintained for three minutes at a boiling tempe- 
rature. Having been poured into a glass, it proved to be deep 
blue and turbid; but on the addition of the necessary quantity 
of water, it afforded a splendid sapphire-blue solution, perfectly 
transparent, -without a trace of undissolved precipitate. There 
is therefore no doubt, not only that by its very marked difference 
of solubility under similar conditions dianic acid is distinguish- 
able from tantalic and hyponiobie acids, but also that the pro- 
perty of producing a blue colour, as above described, belongs to 
‘it essentially, a property which the other acids do not possess. 
I purified in the same way the acid of euxenite and samars- 
kite ; and their behaviour was precisely the same as I observed it 
to be on my endeavouring to remove by agitation with ammonia 
any tungstic acid they might possibly contain. The blue solution 
of dianite and samarskite was of a peculiarly deep colour, almost 
black, so that twice or thrice its volume of water had to be added 
to it to recognize the blue colour distinctly, and to see that the 
solution was perfectly transparent. In a stoppered bottle the 
colour maintained itself quite unaltered for weeks. 
The acid of eschynite I have not purified further than by 
agitation with ammonia; and as in two experiments, independent 
of the blue colour, it proves to be quite as thoroughly soluble as 
the acid of dianite, I have no doubt that it is dianic acid. The 
experiments here described have all been repeated several times, 
particularly those with true tantalic acid, with hyponiobic acid, 
and with the dianic acid of dianite. 
The very peculiar behaviour of dianic acid above described 
with respect to zine as compared with tin, and with hydro- 
chloric acid alone, induced me to make some additional ex- 
