several gases into liquids . 191 
as the common air had not been excluded when the tube was 
sealed, nearly one atmosphere must be due to its presence, so 
that sulphurous acid vapour exerts a pressure of about two 
atmospheres at 45° F. Its specific gravity was nearly 1.42.* 
Sulphuretted hydrogen. 
A tube being bent, and sealed at the shorter end, strong 
muriatic acid was poured in through a small funnel, so as 
nearly to fill the short leg without soiling the long one. A 
piece of platinum foil was then crumpled up and pushed in, 
and upon that were put fragments of sulphuret of iron, until 
the tube was nearly full. In this way action was prevented 
until the tube was sealed. If it once commences, it is almost 
impossible to close the tube in a manner sufficiently strong, 
because of the pressing out of the gas. When closed, the 
muriatic acid was made to run on to the sulphuret of iron, 
and then left for a day or two. At the end of that time, 
much proto-muriate of iron had formed, and on placing the 
* I am indebted to Mr. Davies Gilbert, who examined with much attention 
the results of these experiments, for the suggestion of the means adopted to obtain 
the specific gravity of some of these fluids. A number of small glass bulbs were 
blown and hermetically sealed; they were then thrown into alcohol, water, sulphuric 
acid, or mixtures of these, and when any one was found of the same specific gravity 
as the fluid in which it was immersed, the specific gravity of the fluid was taken : 
thus a number of hydrometrical bulbs were obtained ; these were introduced into 
the tubes in which the substances were to be liberated; and ultimately, the dry 
liquids obtained, in contact with them. It was then observed whether they floated 
or not, and a second set of experiments were made with bulbs lighter or heavier as 
required, until a near approximation was obtained. Many of the tubes burst in the 
experiments, and in others difficulties occurred from the accidental fouling of the 
bulb by the contents of the tube. One source of error may be mentioned in addition 
to those which are obvious, namely, the alteration of the bulk of the bulb by its 
submission to the pressure required to keep the substance in the fluid state. 
