Chemistry and Physics. 409 



# 



crystals. The specific gravity of these two acids is widely different, 

 but unequally so, according to the temperatures to which they have 

 been exposed previous to weighing. 



Owing to want of material, I found it impossible to make a thorough 

 examination of the two acids which are contained in the North Ameri- 

 can columbite : I very soon ascertained, after the discovery of niobic 

 acid, that this was the principal acid constituent in the American 

 columbite, but I could not determine whether it was mixed with pelopic 

 or with tantalic acid ; I therefore addressed myself to Mr. B. Silliman, 

 of New Haven, who with the greatest readiness procured me a very 

 considerable quantity (half a pound) of this now very rare mineral. 



A large quantity of this columbite was used for the preparation of 

 the acid. When treated in tbe same manner as that from the Bavarian 

 columbite, it proved to consist principally of niobic acid combined with 

 pelopic acid ; but the amount of the latter was far smaller than in the 

 Bodenmais mineral, so that I do not think it would have been possible 

 for me to have examined the properties of pelopic acid so completely 

 as was necessary in order to recognize it as an essentially distinct acid 

 from tantalic acid, if I had had only the American mineral at my dis- 

 posal. But both the acids were so perfectly identical in all their prop- 

 erties with the two acids prepared from the Bodenmais mineral, that I 

 did not find the least, difference, even as regards the specific gravity. 



As the specific gravity of pelopic acid is considerably higher than 

 that of niobic acid, when the two are heated in the same manner, the 

 higher specific gravity of the Bavarian columbite is thus satisfactordy 



explained. 



1 have moreover found small quantities of tungstic acid in the acids 

 from the American columbite, as well as in those from the Bodenmais 

 mineral. 



3. Diamond converted to Coke, (Proc. Brit Assoc, 1847, Athen., 

 No. 1028.)— Dr. Faraday exhibited some diamonds, which he had re- 

 ceived from M. Dumas, which had, by the action of intense heat, been 

 converted into coke. In one case, the heat of the flame of oxyd of car- 

 bon and oxygen had been used— in another the oxyhydrogen flame— 

 ^d in the third the galvanic arc of flame from a Bunsen battery of 

 100 pairs. In the las? case, the diamond was perfectly converted mto 

 a Piece of coke,— and in the others the fusion and carbonaceous forma- 

 tion were evident. Specimens, in which the character of graphite was 

 ^ken by the diamond! were also shown. The electrical characters of 

 these diamonds were stated also to have been changed,— the diamond 

 being an insulator, while coke is a conductor. 



4. On Different Properties of the Various Rays °f **&}". J™** 

 «tion on the Daguerreotype Plate prepared with Iodine Chlorine and 

 Bromine, in producing and preventing the Fixation oj Mer euruu va- 

 Por; by A. Claudet, (Proc. Brit. Assoc, 1847, Albw- No. JMOT-J-J 

 M. Claudet has made a series of observations upon light transmitted 

 though certain coloring media, through the vapors of l, « atmosphere, 

 -^d through red, oran|e and yellow glasses. Having *™^ a c * 

 mera obscura upon the sun when its disc appeared quite red, be obtain- 

 *d after ten seconds a black image of the sun. The red sun had pro- 

 duced no photogenic effect, although the surrounding spaces had been 



Second Series, Vol. IV, No. 12.— Nov., 1847. 52 



