42 
Recent Chemical Researches. 
[January, 
both views are perhaps most fittingly presented to us in the 
formulas which are in common use. If the motions and 
configurations of the atoms have been altered (as our ordi- 
nary formulae say they have) energy must have been expended 
in bringing about this alteration, and therefore these formulae 
indirectly express this facft. Various physical considerations 
tell us that there is a difference in the inner constitution of 
i 
isomeric bodies ; their boiling-points are different, and 
Thorpe has shown — in a preliminary paper read to the British 
Association at Belfast — that their specific volumes also vary. 
The propriety of attempting to express the constitution 
of such a body as a molecule upon a flat surface has been 
questioned by Van’t Hoff ; but it is evident, as Lodge has 
shown, that “ any configuration in space may be projected 
on a plane surface, and the only difference between such a 
projection and a diagram drawn diredtly on the plane will 
be — that in the latter the bands are not usually made to 
cross each other, whereas in the former they will be very 
liable to do so.” 
A consideration of groups of compounds leads us to speak 
of recent attempts to systematise inorganic chemistry. 
Lothar Meyer — adopting Mendelejeff’s view, that the 
properties of each element are expressed as a periodic func- 
tion of its atomic weight when the elements are arranged 
in the order of their atomic weights — has endeavoured to 
deduce general formulas which shall express the composition 
of series of salts, thus introducing the homologous and 
heterologous series of organic into inorganic chemistry. 
He has expressed the composition of a number of hydrates 
and other salts by the general formula H 2 „X 2 0 y+w , where X 
represents the atomic weight of an element, v its valency 
as deduced from the highest oxide, and n a whole number, 
which generally does not exceed 4 . The following examples 
will illustrate the application of the formula : — 
n = Q 
n — i 
V= I. 
Na 2 0 
Cu 2 0 
H 2 Na 2 0 2 
H 2 K 2 0 2 “ 
H 2 Cr 2 0 2 
&c. 
Mg 2 0 2 A1 2 0 3 
Zn 2 0 2 B 2 0 3 
H 2 A1 2 0 4 
Mg 2 Al 2 G 4 
&c. 
H 4 Mg 2 0 4 H 2 Ag 2 B 2 0 5 
H 4 Ca 2 0 4 
H 4 Ba 2 0 4 
&c. 
n — 2 - 
