Sir Humphry Davy on the action of acids, &c. 215 
fumes, mixed with orange fumes, fill the upper part of the 
glass, which have a very peculiar and not a disagreeable 
smell. 
The slight effervescence taking place in this process, induced 
me to suppose that the substance which coloured the acid must 
contain a larger proportion of oxygene than euchlorine, for I 
have shown, in a work published in 1812,* that hyperoxy- 
muriate of potassa contains six proportions of oxygene ; and 
by its decomposition 2.5 volumes of oxygene ought to be 
evolved for every volume of chlorine ; and euchlorine pro- 
cured from the hyperoxymuriate of potassa by solution of 
muriatic acid, yields only one volume of oxygene, and two 
volumes of chlorine. 
I endeavoured to procure the substance which coloured the 
sulphuric acid during its action upon hyperoxymuriate of 
potassa, and after several failures, in which explosions took 
place, I at length succeeded in the following manner. Dry 
oxymuriate of potassa in powder was mixed with a small 
quantity of sulphuric acid, and they were rubbed together 
with a spatula of platinum till they had incorporated, and 
formed a solid mass of a bright orange colour. This mass 
was introduced into a small retort of glass, and exposed to 
the heat of water which was gradually warmed ; a bright 
yellowish green, elastic fluid arose from the mixture, which 
was rapidly absorbed by water, giving to it its own tint, but 
which had no sensible action on mercury. 
To make this experiment without danger, not more than 
50 or 60 grains of the hyperoxymuriate should be employed, 
great care should be taken to prevent any combustible matter 
from being present, and the water should not be permitted to 
* Elem. of Chem. Phil. 
