402 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. [November 18,1871. 
CHLORAL. 
BY W. A. TILDEN, D.SC., F.C.S. 
('Concluded from page 342.) 
Chemical Characters of Chloral. —Chloral is a 
colourless oily liquid, of a rather disagreeable odour, 
very soluble in water, alcohol, ether, benzol and 
other solvents. When pure, it boils at about 201° 
F. (a little under 94° C.); sp. gr. at 18° C., 1"502, 
nearly identical with that of chloroform, but a little 
higher. 
Mixed with the due proportion of water it becomes 
hot, and sets on cooling into a crystalline mass of 
the hydrate C 2 HC1 3 0, H 2 0. This substance, when 
slowly crystallized, forms rhomboidal prisms, but is 
usually met with in confused crystalline masses. 
It melts at 122°-123 , 8° F. (50° to 51° C.), and 
boils at a temperature which is always below 212° 
F. (100° C.), but which is estimated by different 
observers at various points between 203° F. (95° C.) 
and 210-2° F. (99° C.). 
Hydrate of chloral contains 89*12 per cent, of 
chloral and yields by decomposition by an alkali, 
72'20 per cent, of chloroform. Its aqueous solution 
should give no turbidity with nitrate of silver. 
Chloral, mixed with any alcohol, furnishes a 
crystalline alcoholate; the formula of the ethyl- 
alcoholate, for instance, being C 2 HC1 3 0, C 2 H 6 0. 
This substance melts at 114-8° F. (40° C.) and boils 
at 234°-239° F. (112*5°-115° C.). It contains 70‘22 
per cent, of chloral, and yields, by the action of 
alkalies, 61"76 per cent, of chloroform. 
Both pure chloral and its aqueous solution are 
said to dissolve many of the alkaloids, among others 
morphia, quinia and strychnia. It is also capable 
of tailing up considerable quantities of some sub¬ 
stances, such as camphor and carbolic and benzoic 
acids, which are by themselves but sparingly so¬ 
luble in water. Chloral hydrate is miscible with 
glycerine. 
Chemical Constitution. —Chloral appears to be 
purely an aldehyd; in fact, the aldehvd of trichlor¬ 
acetic acid. For it not only resembles ordinary 
acetic aldehyd in its general reactions, but these tivo 
bodies are convertible one into the other. Thus, 
like aldehyd, it forms a solid isomer, metachloral, 
into which it is for the most part converted soon 
after separation from the hydrate by sulphuric acid. 
This metacliloral is a white amorphous body, quite 
insoluble in water, but gradually reconverted into 
the soluble form by ebullition with water, or by dis¬ 
tillation. It is not at present known whether there 
exist other modifications corresponding to the liquid 
polymers of aldehyd. 
Then it forms with ammoniacal gas a compound 
which corresponds to aldehyd-ammonia, and which 
possesses the same power of reducing silver in the 
form of a mirror when warmed with a solution of 
the nitrate. 
Like aldehyds in general, it combines with bisul¬ 
phites of the alkali-metals, and, when boiled with 
hydrocyanic and hydrochloric acids, produces a 
syrupy compound, probably analogous to lactic acid. 
By oxidation, chloral is converted into trichlor¬ 
acetic acid, just as aldehyd yields, under the same 
circumstances, though with greater facility, acetic 
acid. 
C 2 H s OH + o = c 2 h 3 oho 
Aldehyd. Acetic Acid. 
C 2 C1 3 0H 4-0=0,Cl,OHO. 
Chloral. Trichloracetic Acid. 
Notwithstanding this close general correspon¬ 
dence between the two, there is necessarily an im¬ 
portant difference in certain properties and reactions, 
the existence of which must of course be referred to 
the presence of the three atoms of chlorine in chloral. 
Thus, the action of alkalies upon aldehyd is to give, 
under ordinary circumstances, resinous products; 
or, by a properly-contrived experiment, hydrogen 
and an acetate are procurable. 
f ch 3 
c H' + 
(OK)'H 
1 0 
Aldehyd. 
Potash. 
( ch 3 
= c (OK)' + 
H'H 
l O 
Potassie Acetate. 
Hydrogen. 
But chloral yields, by contact with alkaline solutions, 
chloroform and a formate— 
f(cci 3 y . ((ok/ 
C-!H + (OK)'H=C H -F(CC] 3 VH 
to (o 
Chloral. Potash. Potassie Chloroform. 
Formate. 
This replacement of hydrogen by chlorine also 
probably explains the deficiency in that eagerness 
for oxygen which is so characteristic of aldehyd. 
Aldehyd, moreover, forms no hydrate. Opinion is 
at present divided as to whether the hydrate and 
alcoholates of chloral are molecular compounds or 
not. The question is, whether in hydrate of chloral, 
for example, the molecules of chloral and water 
stand side by side without change, or whether in 
the act of union a single molecule is formed which 
comprises neither chloral nor water as such. Oil 
the one hand, it may be argued that dehydrating 
agents readily remove water from the hydrate, set¬ 
ting chloral free; and that even distillation of the 
compound causes a partial separation of the two. 
Further, that the alcoholate when treated with an 
alkali yields chloroform, a formate and alcohol. On 
the other hand, the alcoholate is stated to give, by 
the action of pentacliloride of phosphorus, not chlo¬ 
ride of ethyl among the products of the reaction, as 
it should do if it contained alcohol, but a compound, 
in the generation of which the elements both of 
chloral and alcohol are concerned. 
The alcoholate is also represented as differing in 
its physiological action from the hydrate. Until 
better evidence, however, is adduced, it will be more 
convenient to regard these bodies as containing 
chloral and either water or an alcohol. 
Action of Dehydrating Agents upon the Hydrate .— 
Sulphuric acid mixed with hydrate of chloral pro¬ 
duces considerable depression of temperature. On 
gently heating, a separation of liquid chloral occurs, 
which after a time becomes partially opaque from 
the formation of metacliloral. If a considerable ex¬ 
cess of sulphuric acid is employed, there is produced 
another solid body, which has been named chloralide; 
the nature of which is, however, but imperfectly un¬ 
derstood. It seems to result from the metamorphosis 
of part of the metacliloral. 
C 6 H 3 C1 9 0 3 = C 5 H 2 C1 6 0 3 + chci 3 . 
Metachloral. Chloralide. Chloroform. 
