PROFESSOR STOKES ON THE CHANGE OF REFRANGIBILFFY OF LIGHT. 521 
From its colour and the circumstances of its formation, it was probably the other 
hydrate U^O®+HO. It proved on examination to be totally insensible. 
151. Acetate of Peroxide of Uranium, prepared by dissolving the yellow hydrate of 
the peroxide in acetic acid, and evaporating to crystallize. — This salt is extremely 
sensitive, about as much so as the nitrate. The derived spectrum consisted of six 
bright bands arranged at regular intervals. It seemed to me that the last five of 
these were respectively a little more refrangible than the five bands given by the 
nitrate, and then a sixth band was visible in the faint red in the case of the acetate 
which was not ordinarily seen in the nitrate. However, this observation has need to 
be repeated under more favourable circumstances. 
152. Nitrate and acetate of peroxide of uranium, yellow uranite, and canary glass, 
are all so highly sensitive as to allow the primary spectrum to be examined with a 
prism at some distance. In the first three media the bright bands are narrow, 
much narrower than the dark intervals between ; in the glass they appear much 
broader than in the other media. 
153. Oxalate of Peroxide of Uranium, prepared in the manner mentioned by 
M. Peligot, namely, by adding a saturated solution of oxalic acid to a solution of 
nitrate of uranium, washing and drying the precipitate. — This salt was sensitive, but 
only in a low degree. However, the derived spectrum bore prismatic examination 
sufficiently to show three or four bright bands. The absorption of the medium was 
examined by spreading some of the powder on glass along with water and allowing it 
to dry. The layer was then examined by different methods. The salt exhibits three 
very intense absorption bands in the highly refrangible part of the spectrum. The 
positions of these bands, by measurement, were F0’31 G, FO‘58 G, F 0‘85 G. 
154. Phosphate of Peroxide of Uranium, prepared by precipitation from a solution 
of nitrate of uranium by adding a solution of common phosphate of soda. — This salt 
was sensitive, though not in a high degree. It was a good deal more sensitive than 
the oxalate, but I think not so much so as the hydrate of the peroxide. The de- 
rived spectrum consisted of bright bands as usual*. 
155. Uranate of Potassa, prepared by dropping a solution of nitrate of uranium 
into a solution of caustic potash, stopping long before the alkali was neutralized. — 
This salt was found to be insensible, both in its original state as a gelatinous hydrate, 
and in various stages of drying. 
156. Uranate of Lime, prepared in a similar manner with lime-water. — This salt, 
which after drying is of a fine orange colour, was like the preceding found to be 
insensible. It seemed interesting to examine these two salts, because the former con- 
tains two elements (not counting oxygen) in common with canary glass, and the 
latter two elements in common with yellow uranite. Yet the salts are insensible while 
the two other media are so remarkably sensitive. 
157 . Solutions hy means of alkaline carbonates. — It is known to chemists that alka- 
* See note C. 
3x2 
