1876.] 
Recent Chemical Researches. 
43 
The formulae in this table do not always agree with those 
in general use ; but it must be remembered that we are 
altogether in ignorance of the true molecular weights of the 
greater number of these compounds. Similar formulae may 
be deduced to express the composition of other salts ; but, 
as Meyer points out, we need many new researches into the 
too much negledted compounds of inorganic chemistry 
before we shall be able to introduce a complete system of 
classification of compounds. 
With regard to the notation of compounds, we have 
already seen that the formulae in general use imply that a 
certain amount of energy has been expended in the formation 
of one compound from another. Wright has studied some- 
what in detail the relations which exist between affinity and 
structural formulae : he has sought to measure affinity by 
the number of heat-units gained during the coming together 
of several forms of matter, so as to form a given weight of 
a compound body. Many interesting generalisations have 
been deduced, important among which are the following : — - 
The production of ethers and steam from alcohols is ac- 
companied by heat absorption. 
The oxidation of alcohols to acids and steam is accom- 
panied by heat evolution. 
In the substitution of the group CHL for the hydrogen 
belonging to the hydrocarbonous part of a radicle 
heat is evolved, while in the substitution of the same 
group for the hydrogen belonging to the hydroxylic 
(OH) part of a radicle heat is absorbed. 
The replacement of H 2 by O is accompanied by heat 
evolution. 
These results open the way to most interesting consider- 
ations regarding the work done in the formation and 
transformation of chemical compounds ; but before any 
generalisations can be safely made a large amount of experi- 
mental data must be accumulated. 
Among the general results which have been deduced by 
Wright we find the following statement : — “ If an operation 
be performed such that heat is evolved during its perform- 
ance, the resulting produCb boils at a higher temperature 
than the original substance, and vice versa .” This statement 
is in accordance with the views of Mohr, and also with 
those promulgated some years ago by Odling. If we under- 
stand by the evolution of heat the loss of molecular motion, 
it follows that the resultant must be more viscous, so to 
speak, than the substance producing it, and must therefore 
boil at a higher temperature. The subject of the influence 
