Page:Proceedings of the Royal Society of London Vol 1.djvu/452

Rh to the quantity which has been stated, nothing further is gained by continuation of the process.

When mercury is not present during the electrization, then a different result is obtained. The quantity of hydrogen is estimated by the author not to exceed one seventieth part of the gas employed. The gas does not appear to be changed in bulk ; but a part of it is converted into oxymuriatic acid gas. When this gas amounts to a certain proportion of the mixture, the effect of the electricity Will then be to re-unite it to the hydrogen, and form muriatic acid gas rather than to decompose it.

But when mercury is present, it removes the oxymuriatic acid as fast as it is formed; and then a larger proportion of hydrogen is evolved, till every nascent portion of oxymuriatic acid gas is so surrounded by hydrogen that it cannot attain to a state of actual extrication.

In support of this explanation, Dr. Henry mixed thirty measures of hydrogen with 400 of muriatic acid gas; and when this mixture was electriﬁed over mercury, no eﬂ’ect was produced; the quantity of hydrogen was not. increased; and it was evident that no oxymuriatic gas was evolved, as the surface of the mercury remained without the slightest tarnish.

When, on the contrary, the muriatic acid gas was mixed with oxygen, and electriﬁed over mercury, then a diminution of bulk ensued, and the surface of the mercury became tarnished, as by the contact of oxymuriatic gas; and Water was formed in drops, and deposited on the inner surface of the vessel, combined with a portion of the muriatic acid.

These results, says Dr. Henry, may be explained either according to the commonly received theory, or according to that adopted by Mr. Davy.

According to one view the oxygen unites to the real acid of the muriatic gas, and forms oxymuriatic gas, which then deposits water that had been previously held in solution. According to the other, the oxygen unites with the hydrogen, and forms water, while the oxymuriatic base is now disengaged as a simple body.

The author, at present, is not acquainted with any ground for giving a preference to one above the other of these two modes of explanation; but he imagines that something would probably be gained by a precise determination of the proportions in which the gases saturate each other. He has not, however, been able to satisfy himself on this point; and he conceives that the condensation of a portion of the muriatic acid gas by the water that is formed during the process, is an almost insuperable impediment to any precise determination of these proportions.