CHEMISTRY: W. D. HARKINS 
153 
That the appHcation of this hypothesis is not a single problem, is indi- 
cated by the electrical duality of such a field, and by the fact that while a 
part of the combinations between atoms or molecules in such a system may 
be of the, nature of primary valence unions, — presumably a fitting of one or 
more of the outer electrons of one atom into the electronic system of another 
atom, — other molecules maybe grouped together, though very much less firmly, 
by forces which still remain after all of the primary valence combinations have 
been made. In this preliminary paper only the more general features of the 
hypothesis will be considered, — that is only those which can be treated on 
the basis of a general knowledge of the intensity of the electromagnetic field 
around the molecule. The greatest obstacle in this connection is the meager- 
ness of our knowledge of the characteristics of this field, which in this paper 
will be designated as the stray field of the molecule, since it gets out beyond 
the electronic constituents of the molecule. 
The first problem which will be considered is: given two components (A) 
and (B), each in a phase by itself and both phases in the liquid state at the 
common temperature (T), when will these two phases be miscible and when 
will they be practically insoluble in each other? The relation is not difficult 
to find, for we know that (A) mixes with itself; so perfect miscibility should 
result when the stray fields around the molecules of (B) are sufficiently like 
those around the molecules of (A). Likeness of the fields in this sense means 
likeness in intensity, and presumably in the rate at which this intensity falls 
off with the distance from the molecule. A sufficient likeness of stray fields 
is also the condition which must hold if Raoult's law 
is to be valid. Here p^^ and are the vapor pressures of (A) and (B) in the 
mixture. Pa and are the vapor pressures of the pure liquids, and and 
are the mol fractions in the mixture. If (A) is a liquid, but the state of (B) 
is unknown, then (B) is apt to be a liquid if the pressures and temperatures of 
both are the same, though the size of the molecule is a factor which also has 
an effect. If the stray fields around the molecules of (A) and (B) are suffi- 
ciently different, then the two substances will be practically insoluble in each 
other — if the difference is extreme, one of the substances will be a gas and the 
other a solid, if they are at ordinary room temperatures. 
Since the intensity of the stray field falls off more rapidly with the distance 
in the case of some molecules than with others (it probably decreases more 
rapidly around small atoms than around large atoms), it is not possible to give 
a fist arranged in the order of increasing intensity of the stray field which is 
correct in all respects. Thus, while the intensity of the field close to the 
atoms of the heavy metals is very high, it undoubtedly decreases rapidly 
with the distance. On the other hand there are facts which seem to indicate 
