Heinrich Rose. 323 
tended with the greatest difficulties. ‘I do not exaggerate when 
Tsay that the chlorid of niobium could not be considered ag 
quite free from pelopium until the conversion of the acid int 
chlorid had been repeated from twenty to thirty times.” This 
was the second stage of the research; Rose’s remark gives some 
idea of the immense labor with which it was attended. 
For seven years Rose was now occupied in studying the prop- 
erties of the two acids, on the supposition that they were the 
oxyds of different metals, when, at last, their true nature was 
disclosed to him by a fortunate accident. And how many great 
discoveries have been owing to accident! to accident in the 
ds of one who knows how to make use of i 
tion furnished the charcoal. The mixture happened to be 
heated very gradually in the current of chlorine, and the niobic 
continued, when the remark was made, “I have the idea that 
niobium and pelopium are but one and the same substance ;” 
and repeated experiments soon enabled Rose to produce, from 
either acid, either chlorid at will. : 
It might be supposed that the two acids and chlorids are iso- 
Meric modifications of the same matter; but the yellow chlorid 
of pelopium was found to contain more chlorine than the white 
chlorid, and consequently the pelopic acid is a higher stage of 
Oxydation of the niobic. Pelopium having disappeared as a 
_ Separate element, the names of the acids were changed to the 
_ hyponiobic and niobie acid; so that what was before the pelopic, 
ecomes now the niobic acid. 
