398 Scientific Intelligence. 
45°66 per cent of niobic acid, while the Haddam columbite contains at 
least 10 per cent of tantalic acid. There is no hyponiobic acid, but the 
white chlorid discovered by Rose, and which he considered.as a sesqui- 
chlorid of niobium, Nb,Cl,, is in reality an oxychlorid, NbO,CI,; the 
true chlorid of niobium is NbCl,. There exists an oxyfluorid of nio- 
bium, NbO,F,, which combines with fluorid of potassium to form a well 
crystallized salt having the formula NbO,F,,2KF-+2aq. By the action 
W0,F,, a fact which Marignac explains by supposing that an atom 0 
oxygen, ©, is isomorphous with an fluorin 
™m 
niobic acid, but Hermann was right in maintaining, against the authority 
of Rose, that the Bavarian columbite contained tantalic acid, and that 
Rose’s niobic acid was a mixture of tantalic acid and Rose’s hyponiobie 
acid. Marignac separates niobic from tantalic acid by converting “ 
e 
ered as only provisional. The density of pure niobic acid was found to 
be 4:37-4:46 ; prepared in another manner it was 4°51-4'53. The acid 
forms well crystallized salts with potash, contrary to the statemen 
e and Hermann. Marignac describes compounds having respectively 
the formulas 
