24s Dr. Henry's Additional Experiments 
the mercury had considerable influence over the results ; and 
I found, by experiments with tubes of different diameters, 
that the larger the surface of the mercury exposed to the gas, 
the more rapid and complete was the change. Its action was 
greatly accelerated, also, by causing the electric discharge to 
strike from the conducting wire, sealed into the tube, to the 
mercury, which was probably thus raised into vapour ; for in 
some instances, the whole of the inner surface of the glass 
was coated with sublimed calomel. 
The only way, in which the mercury appeared to me likely 
to be efficient in this case, was by removing the oxymuriatic 
acid as fast as it was formed ; for I have never found any 
mixture of this gas in the results of experiments on muriatic 
acid, when carried on over quicksilver. Upon any theory of 
the constitution of muriatic acid, it may be expected that when, 
in a mixture of that acid gas w ith hydrogen and oxymuriatic 
acid gases, the two latter come to bear a certain proportion to 
the former, they will be brought within the sphere of mutual 
agency, and will reproduce muriatic acid. This point appears, 
from my experiments, to be attained, when the hydrogen and 
oxymuriatic acid, taken together, have the proportion to the 
muriatic acid, of about 1 to 35, The amount of the change, 
therefore, which is capable of being effected on muriatic acid 
gas, electrified without the contact of mercury, is limited by 
the reaction of the evolved hydrogen and oxymuriatic acid 
gases on each other, whenever they compose a certain pro- 
portion of the mixture. This proportion being attained, we 
only, by continuing the electrization, work in a circle. 
It may now be inquired, what is the limitation to the action 
of electricity on muriatic acid gas which is confined over mer- 
