Chemical Science. 383 
peroxydize the iron, and then decomposed by carbonate of ammonia, 
in excess, which leaves the iron and earths ; the filtered solution is to 
be hoiled as long as carbonate of ammonia is disengaged, the oxides of 
uranium, zinc, and part of the oxide of cobalt falls down, and is to be 
collected on a filter, washed and dried. It is then to be heated to 
redness, by which it becomes of a dark green colour, and afterwards 
by maceration in dilute muriatic acid has the oxides of cobalt and 
zinc, with a small portion of oxide of uranium, dissolved out, and 
after washing and drying, pure oxide of uranium remains. About 
65 per cent. of the pechblende used was obtained in this way. 
19. Uranium Pyrophori.—When solutions of per-nitrate of ura= 
nium and nitrate of lead are mixed together, and precipitated by 
caustic ammonia, a precipitate falls, which M. Asfwedson considers 
as an uraniate of lead ; after being washed, heated, and pulverized, 
it was of a cinnamon brown colour. This substance being placed 
in a tube was heated, and hydrogen gas passed over it, much 
water was formed, and it is to be presumed that the lead and the 
uranium were both reduced to the metallic state. The product was 
a dark brown powder, which when exposed to the air on paper, took 
fire and ignited, leaving uraniate of lead asa residue. This singular 
phenomenon, which was quite unexpected, may have been occasioned 
(M. Arfwedson suggests) by an electro-chemical action between the 
two metals, which caused their combustion. 
When uraniate of barytes is reduced by hydrogen in a similar 
manner it also produced a body presenting the same phenomenon in 
the air; and the pyrophorus thus obtained from the uraniate of iron is 
still more powerful than either of the former. 
20. Atomic ox proportional Weights.—Dr. Thomson gives the fol- 
lowing as the most correct expression of the atomic weights of the 
substances mentioned according to his last experiments ; 
Boracic acid. .. - . 3.00 
Tartaricacid , . « . $8.25 
Pie ACI Me aw (dno 
Fluoboricacid . « . « 4.25 
Tartaric acid crystallized. 9.375 
Oxygenbeing . . . . 1.00 
The crystals of tartaric acid contain 1 proportional of water.— Ann, 
Phil. N.S. VII. 245. 
21. On the Acetates of Copper. By M. Vauquelin,—The follows 
ing results are abstracted from a paper by M. Vauquelin, read to 
the Academy of Sciences, Nov. 6, 1823, and published in the Mé- 
moires du Museum, x. 295. ; 
Analysis of the Crystallized Acetate of Copper.—A given weight was 
2D2 
