REPORT ON CHEMISTRY. 
421 
one volume of chlorine, we obtain two volumes of muriatic acid. 
Now, according to Dumas, the volume being always equal to 
the atom, we have two atoms of the acid formed out of one atom 
of each of its elements, or half an atom of hydrogen combined with 
half an atom of chlorine produces a whole atom of muriatic acid. 
To obviate this objection, Dumas supposes that heat when it 
imparts the gaseous form does not subdivide matter into its 
chemical atoms; so that when they are acted upon by chemical 
affinity, a further separation of the entire atoms may take place, 
and thus the apparent combination by fractional parts in the 
union of volumes be accounted for. 
Berzelius, again, considers the atom and the volume equal 
only in simple gaseous bodies ; or that equal volumes of all the 
simple permanent gases contain an equal number of atoms. 
This view does not give rise to the anomalies which the theory 
of Dumas presents, while it retains the simplicity implied in 
the idea of equal atoms being contained in equal volumes. It 
has been adopted by most of the Continental chemists. 
The third mode of comparing atoms and volumes, which is 
generally followed in this country, differs from that of Berzelius 
in making oxygen an exception to the general rule. All other 
simple gases or vapours are supposed to contain equal atoms 
in equal volumes;—oxygen in an equal volume to contain twice 
as many atoms. This opinion involves a departure from the 
supposed simplicity of nature, for which there is, a priori, no 
sufficient reason. Whether or not it may ultimately prove a 
true representation of the relation between atoms and volumes, 
will depend upon the result of researches at present beyond 
our reach, by which some or all of the gases and vapours we 
now consider simple may be shown to be compound. In the 
mean time it is adopted by British chemists chiefly on account 
of the simpler view it enables us to take of the compounds of 
oxygen with hydrogen, chlorine, and other elementary sub¬ 
stances. 
Dumas's researches on the density of Gases and Vapours .— 
A very interesting inquiry connected with this subject has 
been opened by some late experiments of Dumas. His opinion 
above stated, that equal volumes of all simple substances in 
the state of gas or vapour contain an equal number of atoms, 
led him to determine the relative atomic weights of several vo¬ 
latile solid substances by a rigorous determination of their re¬ 
spective specific gravities in the state of vapour. For mercury, 
phosphorus and sulphur, he obtained the following results: 
