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Chemistry. - 
when the solution immediately became cloudy, and was very speedily 
decomposed, the precipitate falling heavily. By experiments with the 
spectrum, the author found that the precipitation was due aint entirely 
to the most refrangible rays. 
_A few grains of sulphate of the protoxide of iron were dissolved in 
rain water; if kept in perfect darkness, the solution remained clear 
for a long time; it became, however, eventually cloudy and colored 
from the formation of some peroxide of iron, even in tubes hermet- 
ically sealed. A few minutes’ exposure to the sunshine is sufficient 
to produce this change, and the oxide formed, instead of floating in the 
liquid, and as in the former case rendering it opaque, falls speedily to 
the bottom. 
_Mr. Hunt made some experiments, (particularly one with a mixture 
of the bichromate of potash and the sulphate of copper,) in which pre- 
cipitation appears retarded by solar agency, and he is inclined to think 
that it will eventually be proved that the electric energy of the different 
bodies in relation to each other, will greatly modify the results obtained 
in these experiments. 
The action of the sun’s rays appears also to affect the color of the 
precipitates. Ifa solution of bichromate of potash is exposed to sun- 
shine, it acquires a property of precipitating several metals as chromates, 
differing many shades in color from the colors produced by a solution 
similarly prepared and kept in the dark. If the actinized solution 
(solution exposed to sunshine) be poured into a solution of nitrate of 
silver, the chromate of silver formed is of a much more beautiful 
color than that given by a solution which has not been exposed to the 
sun’s rays. The same is true when the salts of mercury are used. 
Solutions of sulphate of iron exposed to sunshine, yield a Prussian 
blue, with the ferrocyanide of potassium, of a far more beautiful color 
than that produced by a solution which has not been so exposed 
Among other curious actions that the sun’s rays exert, is the one by 
which it prevents electro-metallic precipitation. Place in a test tube a 
strong solution of nitrate of silver; in another tube, closed at one end 
by a thin piece of bladder, place a solution of iodide of potassium ; 
this is supported i in the solution of nitrate of silver by being fixed ina 
_ cork, and a piece of platinum wire is carried from one solution into the 
Other. An arrangement of this kind being kept in the dark, iodine is 
Soon liberated in the inner tube, and a crystalline arrangement of me- 
tallic silver is formed around the platinum one, in the outer. Another 
loan placed in the sunshine, iodine will be liberated, but no silver 
eposite 
Mr. has examined at length the action of the sun’s rays upon 
some photographic preparations, (the salts of silver,) with many curious 
