JANUARY 19, 1912] 
eapable of doing anything chemically, and 
that the science of solutions is much broader 
than chemistry will be seen after a moment’s 
reflection. Geology is largely a science of so- 
lutions—of aqueous solutions and molten 
magmas, and how many branches of the bio- 
logical sciences owe their existence to matter 
dissolved in other forms of matter? 
In the pure homogeneous condition matter 
is, as we have stated, relatively inert. Na- 
ture, and, consequently, the science of nature, 
is, as it is, primarily due to matter in the dis- 
solved state; and our knowledge of solutions, 
thanks to Van’t Hoff and Arrhenius, is now 
reasonably satisfactory. We know far more 
about matter in the gaseous state than in the 
liquid or solid state. Wan’t Hoff has shown 
us that we can deal with solutions in many 
fundamental respects as we deal with gases. 
Consequently, we know far more about matter 
in solution than in the pure homogeneous 
liquid or solid condition. Why should these 
facts be concealed from the student of chem- 
istry until late in life? 
And now we come to another fundamental 
matter—the nature of the units that take part 
in chemical reaction. For a long time it was 
taught that the atoms and the molecules are 
the active chemical agents, and this was in 
keeping with what was known at the time. 
This is now largely changed. The number 
of concordant lines of evidence which show 
that electrically charged parts are necessary 
for chemical activity, is so great, that I know 
of no productive chemist to-day who seri- 
ously questions it. After thinking over this 
problem and working upon it for a good 
many years, I am of the opinion that there is 
no chemical reaction known to man in which 
at least one of the substances taking part in 
the reaction is not more or less ionized. In- 
deed, I am unable to form any physical con- 
ception of even the posibility of a chemical 
reaction between electrically neutral parts, 
any more than I can form a conception of 
two electrically neutral bodies attracting or 
repelling one another electrically. It would 
lead us much too far to discuss at all fully 
this question here, nor is it necessary to do so. 
SCIENCE 91 
To furnish evidence to-day for the general 
truth of the theory of electrolytic dissocia- 
tion, would be as unwise and as useless as to 
furnish new evidence for the law of the con- 
servation of energy, or for the law of the con- 
servation of mass. 
In the light of these facts are we justified 
in continuing to teach the beginner the old 
chemistry of atoms and molecules, which we 
know, or should know, is untrue; trusting to 
later years, to new experiences, or to another 
instructor to correct these erroneous first im- 
pressions, which, as has been stated, is well 
nigh impossible. 
Take another phase of things. A phe- 
nomenon which must be encountered very 
early in the study of chemistry is precipita- 
tion, already referred to in another connec- 
tion. Has it been possible to treat this sub- 
ject scientifically until quite recently? I 
think not. Whenever a precipitate could be 
formed it was formed, was about the way this 
matter was left. In the chemical reaction in 
question a solid is formed, which is practically 
insoluble in the solvent used; and being in- 
soluble it is thrown down in that coarse- 
grained condition that we call a precipitate. 
Think of this for a moment. When the 
solid was formed it was probably in a state of 
molecular aggregation. How do these solid 
molecules know enough to come together and 
form aggregates of the sizes that exist in pre- 
cipitates? Furthermore, if this is the “nat- 
ural condition” of insoluble solids when 
formed in a chemical reaction, then why do 
we not always have precipitation when an in- 
soluble solid is formed in a reaction? In a 
word, why do we have in some eases colloidal 
suspensions? 
To fix the idea and by way of illustration, 
why is arsenic sulphide precipitated when ar- 
senic chloride is treated with hydrogen sul- 
phide, but is not precipitated when arsenic 
oxide of the same concentration as the chloride 
is treated with hydrogen sulphide? Not only 
must every teacher of chemistry have asked 
himself this question, but every intelligent 
student, before he has advanced very far, must 
do so. 
