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428 fe Scientific Intelligence. 
returning the paper to the stone, and pressing the tin plate down upon 
it with the hand. 
5. On a New Process for obtaining pure Chlorine Gas ; by Profs. 
R. E. Rocers, and W. B. Rocers, of the University of Virginia, 
(communicated by the authors.)—This process is founded on the pow- 
erful oxidating action of chromic acid, especially when liberated in a 
solution, and consists in causing a reaction between hydrochloric acid 
and this substance, in which the chlorine of the former is set free. Our 
mode of proceeding is as follows. 
To 1 part of powdered bichromate of potassa, in a small retort or 
‘flask, we add 6 parts of hydrochloric acid, of specific gravity about 
1:16, and apply a gentle lamp heat for a few seconds, so as to bring 
about a brisk reaction. The chlorine is now rapidly evolved, and con- 
tinues to be disengaged as fast as is convenient, without requiring any 
further application of the lamp. 
Referring to the composition of the bichromate of potassa and of 
hydrochloric acid, it will be seen that one equivalent of bichromate of 
potassa and seven of hydrochloric acid, are capable of evolving three 
equivalents of chlorine, at the same time giving rise to one equivalent 
of the sesquichloride of chromium, one of the chloride of potassium, 
and seven of water. 
In order to ascertain how near we might iinet to the equivalent 
quantity of chlorine above deduced, we resorted to the following method. 
Knowing that a strong solution of chloride of sodium is much less ab- 
sorbent of the gas than ordinary water, we prepared a quantity of satu 
rated brine, through which we passed chlorine, until the liquid appeared 
to be fully charged. With this we filled a tall graduated vessel, design- 
ed to receive the gas, and a porcelain bowl, which served as a pneu- 
matic trough, and having placed 4 grammes of the bichromate with an 
excess of hydrochloric acid in a small retort, we passed the gas as it 
was evolved through the chlorous saline solution into the narrow grad- 
uated jar. After urging the process until the action entirely ceased, 
and no further gas escaped, we measured the resulting gas with the 
usual precautions, at 60°. Its volume was found to be 54°5 cubic inches. 
On repeating the experiment with the same amount of bichromate and 
acid, and with the same brine, we obtained in the second trial 55-5 cubic 
inches, and in the third 56:2 cubic inches of the gas, the increase being 
evidently due to the diminished absorption arising from the more come 
plete saturation of the liquid with chlorine. 
Taking 76°5 grains as the weight of 100 cubic inches of chlorine, at 
60° Fahr., the volume due to the entire decomposition of 4 grammes of 
bichromate of potassa, is 57°3 cubic inches. It thus appears that with 
proper precaution, this process may be made to yield $$ths, or nearly 
the whole theoretical amount of the gas. 
