[Footnote 1: Translated from the _Pharmaceutische Centralhalle_, by
A.G. Vogeler.--_Western Druggist_.]
By A. GANSWINDT.
"Water consists of one atom of oxygen and two atoms of hydrogen." This
proposition will not be disputed in the least by the author; still, it
may be profitable to indulge in a few stereo-chemic speculations as to
the nature of the water molecule and to draw the inevitable
conclusions.
From the time of the discovery, some 110 years ago, that water is a
compound body, made up of oxygen and hydrogen, the notion prevailed up
to within a quarter of a century that it was composed of even
equivalents of the elements named, and all but the youngest students
of chemistry well remember how its formula was written HO, the atomic
weight of oxygen being expressed by 8, making the molecular weight of
water (H=1 + O=8) 9. But the vapor density of water, referred to
air, is 0.635, and this number multiplied by the constant 28.87, gives
18 as the molecular weight of water, or exactly twice that accepted by
chemists. This discrepancy led to closer observations, and it was
eventually found that in decomposing water, by whatever method
(excepting only electrolysis), not more than the eighteenth part in
hydrogen of the water decomposed was ever obtained, or, in other
words, only just one-half the weight deducible from the formula HO =
9. The conclusion was irresistible that in a water molecule two atoms
of hydrogen must be assumed, and, as a natural sequence, followed the
doubling of the molecular weight of water to 18, represented by the
modern formula H_{2}O.
Both the theory and the practice of substitution enable us to further
prove the presence of two hydrogen atoms in a water molecule.
Decomposing water by sodium, only one-half of the hydrogen contained
is eliminated, the other half, together with all of the oxygen,
uniting with the metal to form sodium hydroxide, H_{2}O + Na = H +
NaHO. Doubling the amount of sodium does not alter the result, for
decomposition according to the equation H_{2}O + 2Na = H_{2} + Na_{2}O
never happens. Introducing the ethyl group into the water molecule and
reacting under appropriate conditions with ethyl iodide upon water,
the ethyl group displaces one atom of hydrogen, and, uniting with the
hydroxyl residue, forms ethyl alcohol, thus: H_{2}O + C_{2}H_{5}I =
C_{2}H_{5}OH + HI. Halogens do not act directly on water, hence we may
not properly speak of halogen substitution products. By the action,
however, of phosphorus haloids on water an analogous splitting of the
water molecule is again observed, one-half of the hydrogen uniting
with the halogen to form an acid, the hydroxyl residue then forming a
phosphorus compound, thus: PCl_{3} + 3H_{2}O = 3HCl + P(OH)_{3}.
Now these examples, which might readily be multiplied, prove not only
the presence of _two_ hydrogen atoms in the water molecule, but they
further demonstrate that these two atoms _differ from each other_ in
respect to their form of combination and power of substitution. The
two hydrogen atoms are certainly not of equal value, whence it follows
that the accepted formula for water:
H
> O
H
or as preferred by some: H-O-H, is not in conformity with established
facts. Expressed as here shown, both hydrogen atoms are assigned equal
values, when in fact only _one of the atoms is united to oxygen in
form of hydroxyl_, while the second is loosely attached to the
univalent hydroxyl group. Viewed in this light, water then is
decomposed according to the equation: H_{2}O = H + (OH), never in this
manner: H_{2}O = 2H + O. Hence, water must be considered as a
combination of one hydrogen atom with one molecule of hydroxyl,
expressed by the formula H(OH), and it is this atom of hydrogen _not_
united to oxygen which is eliminated in the generation of oxygen or
substituted by metals and alkyl groups. The hydrogen in the hydroxyl
group cannot be substituted, excepting it be the entire group as such;
this is proved by the action of the halogens, in their phosphorus
compounds, upon water, when the halogen takes the place of the
hydroxyl group, but never that of the hydrogen.
Now as to some logical deductions from the foregoing considerations.
Hydrogen is by many looked upon as a true metal. This theory cannot be
directly proved by the above, but it is certainly greatly strengthened
thereby. To compare. Hydrogen is a powerful reducing agent; it is
similarly affected by the halogens, the hydroxyl group, the acid
radicals, oxygen and sulphur; hydrogen and members of the univalent
alkali metals group are readily interchangeable; it forms superoxides
analogous to the metals; its analogy to the alkali metals as exhibited
in the following:
H H(OH) HCl HNO_{3} H_{2}SO_{4} H_{2}S H_{2}O_{2}
K K(OH) KCl KNO_{3} Na_{2}SO_{4} Na_{2}S K_{2}O
But if we consider hydrogen as a gasiform metal, we naturally arrive
at the conclusion that _water is the hydroxide of this gasiform
metal_, that is _hydrogen hydroxide_, while gaseous hydrochloric and
hydrosulphuric acids would be looked upon as respectively the chloride
and the sulphide of the metal hydrogen. This would then lead to
curious conclusions concerning the hydroxyl group. This group would,
by this theory, become an oxygenated metal radical similar to the
hypothetical bismuthyl and uranyl, and yet one in which the metallic
character has disappeared as completely as in the ferrocyanic group.
An entirely new light is shed by this view upon the composition of
hydrogen peroxide, which would be looked at as two free hydroxyl
groups joined together thus: (OH)--(OH), analogous to our di-ethyl,
diphenyl, dicyanogen, etc. Considered as dihydroxyl, it would explain
the instability of this compound.
The ethers proper would also be placed in a new light by this new
conception of the constitution of the water molecule. The hydrogen in
the hydroxyl group, as is known, may be substituted by an alkyl group.
For instance, an alkyl may be substituted for the hydroxyl hydrogen in
an alcohol molecule, when an ether results. According to the new
theory this ether will no longer be considered as two alkyl groups
connected by an oxygen atom, but as a compound built up on the type of
water by the union of an alkyl group and an alkoxyl group. Thus
ethylic ether would not be represented by
C_{2}H_{5}
> O,
C_{2}H_{5}
as heretofore, but by the formula C_{2}H_{5}(OC_{2}H_{5}), which is
ethyl-ethoxol. Acetone would admit of a similar explanation.
Finally the assumption of dissimilarity in character of the hydrogen
atoms in the water molecule possibly may lead to the discovery of a
number of unlocked for isomerides.
Thus, by appropriate methods, it ought to become possible to introduce
the alkyl groups solely into the hydroxyl group (instead of into the
place of the loosely attached H-atom). In that case chemists might
arrive at an isomeride of methyl alcohol of the formula H.(OCH_{3}),
or at methoxyl hydride, a compound not alcoholic in character, or at a
nitroxyl hydride, H(ONO_{2}), not of an acidic nature. Oxychlorides
would be classed with this latter category, that is, they would be
looked on as water in which the free hydrogen atom has been
substituted by the metal, and the hydrogen atom of the hydroxyl by
chlorine. This example, indeed, furnishes a most characteristic
illustration of our theory. In the case just now assumed we arrive at
the oxychloride; when, however, the metal and chlorine change places
in the water molecule, the isomeric hypochlorous salts are the result.
It is true that such cases of isomerism are as yet unknown, but we do
know that certain metals, in our present state of knowledge, yield
oxychlorides only, while others only form hypochlorous salts. This
condition also explains why hypochlorites still possesses the
bleaching power of chlorine, while the same is not true of
oxychlorides. However, it seems needless to multiply examples in
further illustration of the theory.
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