808 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[April 12, 1873. 
There is no more reason to regard albumin as plastic than 
water, fat and salts, for these are quite as indispensable as 
albumin to the constitution of a cell. Moreover, the 
greater part of the albumin taken into the body undergoes 
decomposition without even having formed part of any 
organ. Fat and carbohydrates, too, are not specially des¬ 
tined to produce heat, and they undergo decomposition 
quite independently of the thermal necessities of the body. 
It is quite a mistake to suppose that the oxygen taken in 
during respiration is the cause of the decomposition of the 
tissues, for it is in reality a consequence. The tissues split 
up into simple compounds quite independently of oxygen, 
and it is these compounds which take up the oxygen. A 
proper division of food can only be based on a considera¬ 
tion of the constituents of the body, and of what is neces¬ 
sary to replace the waste of these. 
The constituents are water, inorganic materials, fats 
and albumin and its derivatives. Of water there is gene¬ 
rally no lack, and inorganic constituents are generally 
found in abundance in any diet which contains a sufficient 
quantity of albuminous and non-nitrogenous materials, 
and therefore they do not require any special considera¬ 
tion. Fat can be supplied by giving it directly in the 
food. Animals in general, and especially herbivora, can¬ 
not take a sufficient quantity in this way, and it is there¬ 
fore necessary to give carbohydrates in addition, which 
probably do not themselves form fat, but economize it. 
It can also be supplied by a diet of flesh, which by decom¬ 
position in the organism yields fat. 
To replace the waste of albumin, a certain quantity of 
it must under any circumstances be contained in the food ; 
at least as much as will replace the waste of organ- 
albumin. G-enerally much more than this is necessary, 
in order to keep up the stock of circulating albumin. A 
large quantity of albumin is required for this purpose 
when it is given alone, but much less suffices when fats 
and carbohydrates are given along with it, although they 
can never become transformed into albumin. This most 
important use of these articles of food was not sufficiently 
noticed under the old classification into plastic and respi¬ 
ratory. It is impossible to give gelatin a place in this 
classification at all, for it cannot assist in the formation of 
tissues, and is therefore not plastic, nor has it any greater 
value as respiratory food than albumin, and consequently 
cannot be ranked as such. Under Voit’s new classifica¬ 
tion, it falls into its place at once. It economizes circu¬ 
lating albumin, like fats and carbohydrates, but much 
more powerfully, in this respect resembling peptones, 
which are not again converted into albumin. Besides 
this, it economizes fat to a slight extent. 
THE ACTION OF HEAT ON SOLUTIONS OF 
HYDRATED SALTS.* 
BY C. It. C. TICHBOKNE, F.C.S., M.R.I.A. 
While investigating the dissociative action of heat upon 
water of hydration, the author’s attention was naturally 
turned to salts,—such as those of cobalt, copper, and 
nickel,—which present a change of colour when passing 
from the dry to the hydrated state. It is a general 
characteristic of neutral solutions of the chlorides of such 
bodies that they do not change colour on boiling at 
ordinary atmospheric pressure, neither does dilution affect 
their tint except by attenuating it ; but Mr. Tichborne 
has never failed in their obtaining dehydration in solution by 
using extraordinary pressure. The laws of such chromatic 
change were found to differ from those produced by a 
basic condition of the salt. 
For instance, the dehydration of the salts of cobalt is 
evinced by change of colour from light rose to dark pure 
blue. But no amount of boiling at ordinary pressure will 
convert a pink solution of cobalt into a blue one, unless 
the solution be extremely concentrated. Prout stated 
* Abstract of a paper read before the Royal Irish Aca¬ 
demy. 
many years ago, that by concentrating a strongly acid 
solution of a cobalt salt by evaporation, he got a perman¬ 
ently blue solution, a result which he attributed to the 
abstraction of the water of hydration by the acid. He 
also reported that he had obtained from such a solution 
blue crystals, supposed to be the anhydrous salt. This 
experiment of Prout showed that the introduction into a 
neutral solution of any substance capable of exerting an 
affinity for the water of hydration—such as sulphuric and 
other acids, chloride of calcium, and other hygroscopic 
salts, or even sugar—has the effect of lowering the therm- 
analytic point of the salt. The quantity, however, of 
these dehydrants required to affect the cobalt solution 
being considerable, pure absolute alcohol was used to 
lower the thermanalytic point. 
A solution of chloride of cobalt,* which has dried at 
100° C. in pure absolute alcohol, is of a magnificent pure 
blue colour, free from any tinge of purple. If such a 
solution be placed in a deep beaker, and water poured 
cautiously down the side of the vessel, two layers are 
formed, the upper of which is blue, and contains the 
anhydrous salt ; the lower pink, containing the salt hy¬ 
drated by the direct action of the water. These layers 
will retain their positions a considerable time, by virtue of 
their different specific gravities. 
Alcoholic solution which has been thus hydrated is 
peculiarly sensitive to heat, passing, as the temperature 
rises, through all the shades of pink and purple to a pure 
blue, giving the same absorption spectrum as that obtained 
from the anhydrous salt. • The thermanalytic point is so 
lowered by the alcohol present that the water of hydration 
of the cobalt salt is gradually but perfectly dissociated. 
If the vessel containing it be now submerged halfway into 
a freezing mixture, the two differently coloured layers are 
again formed, the upper one, as before, being blue, and 
containing the anhydrous salt in the presence of the dis¬ 
sociated water of hydration. 
Such is the result when, through the addition of another 
body, the thermanalytic point is brought below 100° C. 
at ordinary pressure. Similar effects are obtained when 
a weak solution of cobalt is boiled in a sealed glass tube 
one-third full of the liquid, the colour passing gradually 
through all shades of purple to a pure blue. Thus, by 
extraordinary pressure, the temperature necessary for the 
separation of the water may be obtained in an aqueous 
solution. 
Aqueous solution of chloride of copper, heated in a 
sealed tube, from a beautiful blue, the colour of the hydrate, 
becomes gradually green, yellow, and ultimately a dark 
brown nearly opaque liquid. As it cools and gradually 
re-associates the water of hydration, it passes again through 
all these shades, becoming slightly opalescent through the 
formation of a bluish white basic precipitate. The addi¬ 
tion of a little acid to this solution prevents this precipi¬ 
tation, makes the solution even more sensitive to heat, 
and allows the experiment to be made ad infinitum. 
Solution of sulphate of copper gives similar results as to 
dehydration, but a basic precipitate is determined even in 
an acidulated solution. 
Caution should be used in these experiments, as explo¬ 
sions frequently occur. The plan recommended by the 
author is to take a strong white glass tube, draw it out 
until it has a diameter of or of an inch, and enclose 
this, when sealed, inside another much larger one before 
heating it. 
The author points out that the effect of dilution on 
colour changes attending dehydration is, as might be ex¬ 
pected, the reverse of that upon colour changes attending 
the basic condition due to the basic, action of the water. 
In the first case, the increase of the relative volume of 
water retards the dissociation of water of hydration ; in 
the second, the increase in the volume of water will assist 
the dissociation. 
* According to Marignac, the composition of the hy 
drated salt is CoCl2,6H 2 0. 
