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Nature
(Thursday, November 4, 1869)

Williamson, A. W.
[The late Professor Graham],   pp. 21-22


Page 21


Nov. 4, I869]
NA TURE
year. It was in 1830 that he was appointed Professor of
Chemistry at the Andersonian University, Glasgow; and
it is said that his mother, who was on her deathbed, lived
to hear the glad tidings of his appointment. He was now
more favourably circumstanced for experimental labours,
and we find that the seven years spent at the Andersonian
University were years of great activity.
  In 1837 he was appointed Professor of Chemistry in
the London University, now called University College,
London, and he occupied that chair with great distinc-
tion till the year i855, when he succeeded Sir John
Herschel as Master of the Mint, which appointment
may be considered an acknowledgment on the part of the
Government of his scientific services and of his high
character.
  His numerous discoveries have been much quoted.
Some of their theoretical bearings claim a brief notice
here.
  His investigation of the phosphates is remarkable in
many ways. It was known that solutions of phosphoric
acid in water vary in their pro-
perties; and chemists Rvere sa-
tisfied with giving a name to
the changes without investigat-
ing their nature. These solu-
tions contained phosphoric acid
and water, and were assumed to
have like composition. They'
were accordingly called isomeric.
Graham observed that they differ
from one another in the pro-
portion of water combined with
the acid, and constitute in rea-
lity different compounds.
  He knew that water combines
with acids as other bases do, and
he showed that the various com-
pounds of phosphoric acid and
water constitute distinct salts,
each of which admits of its
hydrogen being replaced by
other metals without disturbance
of what we should now call the
type. Thus, to use our present
notation, the three hydrates
PO4H,, P,OH,, POH, corre-
spond to the following propor-
tions of acid and water:-
P205 + 3H20
P205 + 2H.O
P205+ HO
- 2PO4H,
-POR2PH
- 2P0,H
  Graham observed that the hy-     THomsAS GRAHAM (fn
drate POH, is constituted like'a
salt, inasmuch as its hydrogen can be replaced atom
for atom by other metals, like sodium, potassium, &c.,
forming such compounds as PO4NaH., PO4Na2H, &c.
  In order to appreciate duly the powers of mind of the
author of this admirable research, we ought to compare
his methods of reasoning with those generally prevalent
among contemporary chemists, and on the other hand
with the methods of to-day. One would fancy that
Graham had been acquainted with the modem doctrines
of types and of polybasic acids, so clearly does he describe
the chemical changes in matter-of-fact language, and so
consistently does he classify the compounds by their
analogies. At that early period we find Graham considering
hydrogen, in various salts, as a basylous metal; an idea
which (in spite of its undeniable truth) some chemists of
the present day have not fully realised.
  Amongst minor chemical researches may be mentioned
a series of experiments on the slow oxidation of phosphorus
by atmospheric air. He discovered that this process (and
the faint light which accompanies it) is arrested by the
r1
21
i presence in the air of a trace of olefiant gas, 41 of the
volume of the air being sufficient for the purpose. Still
smaller proportions of some other vapours were found
capable of producing this same effect; spirits of turpentine
being particularly remarkable, as less than a quarter of a
thousandth of its vapour with air was found sufficient to
prevent the slow oxidation of phosphorus.
   On another occasion Graham investigated phosphuretted
 hydrogen, and made some remarkable observations
 concerning the conditions of the formation of the
 spontaneously inflammable gas. One of these deserves
 especial notice in connection with the action of olefiant
 gas, and in preventing the oxidation of phosphorus. He
 found that phosphuretted hydrogen is rendered sponta-
 neously inflammable by the admixture of a very small
 proportion of an oxide of nitrogen, probably nitrous acid.
   One of the most obscure classes of combinations are
 those which water forms with various salts. These bodies
 are characterised by the chief peculiarities which belong
 to definite chemical compounds; but chemists are as yet
                        unable to explain them.
    -a _-~                Water so combined is called
water of crystallisation, and is
said to be physically, not che-
mically, combined. Avery con-
venient way of getting rid of a
difficulty, by passing it on to our
neighbours.
  Graham examined the pro-
portion of such water of crys-
tallisation in a considerable
number of salts, and he more-
over examined the properties
which it has when so combined.
He found that some of the
water in an important class of
sulphates is held far more firmly
than the remainder, and with
force equal to that with which
water is held in various chemical
compounds. He showed that
such firmly combined water can
be replaced by salts in a definite
chemical proportion.  ln fact,
he got fairly hold of the subject
by chemical methods, and laid
the foundation for an explana-
tion of it.
  He discovered and examined
compounds of alcohol with salts,
and derived from them valuable
evidence nf the nnaino-u hetween
                             -.  -_ _     fibs a -.. __.
m a recent Photograph)   alcohol and water.
                           On a later occasion he made
a series of important experiments upon the transformation
of alcohol into ether and water, by the action of hydric
sulphate. Liebig had endeavoured to explain the forma-
tion of ether in this process, by representing it as due to
the decomposition at a high temperature of a compound
of ether previously formed at a lower temperature; such
decomposition being due to the increased tension of the
vapour of ether at the higher temperature.
  Graham justly argued that if the decomposition were
due to the tension of ether vapour, it would not take
place, and ether would not be formed, if the tension were
not allowed to exert itself. He heated the materials in a
closed tube, and proved that ether was formed, although
the tension of its vapour was counteracted by the pressure
thus obtained.
  The line of research which occupied most of his atten-
tion, and in which his results were perhaps the most im-
portant, was that of diffusion; and it would be difficult to
over-estimate the importance to molecular chemistry of
his measurements, of the relative velocities of these


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