Technical Physics. 283 
periments were made with a solution of nitrate of sesquioxyd of 
chromium and it was found that 5 ¢. ¢. of chromic nitrate employed to 
1c. ¢. each, of the solutions of phosphate of soda and nitrate of bismuth, 
were sufficient to prevent the formation of any precipitate. The solution 
used was a rather strong one. 
large amount, dissolves the precipitate entirely. The phosphate of bis- 
muth when thrown down from a solution containing uranic nitrate is 
contaminated with the latter. 
similar series of experiments was made with the nitrates of ammonia, 
potassa, baryta, strontia, lime, and magnesia. The presence of these bases 
8 not seem to interfere with the success of the method. 
and is likely to remain valueless in just those cases where a new method — 
would be most acceptable, viz. for the estimation of phosphoric acid in 
Presence of alumina. S.-W. J. 
Yale Scientific School, Feb. 15, 1861. 
Tecuxicat Puysics, 
9. On the loss of Light by Glass Shades—(To the Editor of Silliman’s 
American Journal of Science and Arts)—Sir: In the November num- 
ber of your Journal I find a notice of my experiments on the loss of 
light by glass shades, with an account of additional investigations by 
Mr. Frank H. Storer; his communication induces me to offer so 
ther remarks on the subj 
n of the amount of light, falling for example, upon 
book held near to its source, which 
‘ition of the shades enumerated.” 
po the ° : of a 
would be occasioned by the interpo- 
+ Prof, Verver had another object in view. and his experiments ‘iments do not 
ply to this subject. He was ay igating the illuminating power of 
oa hen burnt in an Argand burner with, and without, a chimney. The 
