October 28, 1871.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
341 
CHLORAL. 
BY W. A. TILDEX, D.SC., F.C.S. 
A little more than two years ago the notice of the 
world was drawn to the remarkable physiological 
action of a substance, which at that time had pro¬ 
bably been not even seen by more than a few indi¬ 
viduals, and of which the quantity then in existence 
might he estimated by ounces. 
At present it is bought and sold by hundreds of 
pounds. 
In consequence of its production upon so large a 
scale, and of having become, in so pure a form, a 
regular article of commerce, chloral has latterly re¬ 
ceived from chemists a very considerable share of 
attention. Apart from considerations connected with 
its employment in medicine, a body of characters so 
singular deserved that its chemical history should 
be studied more closely than had hitherto been the 
case. 
Experiments upon chloral, upon its hydrate, and 
upon other bodies more or less nearly related to it, 
have multiplied. Most of them are, however, of 
comparatively recent date, and are consequently not 
yet to be found in books. 
Manufacture .—As every one knows chloral is 
made by passing chlorine gas into alcohol, mixing 
the product with oil of vitriol and rectifying. But 
the number of precautions to be taken to ensure a 
successful result, can only be properly appreciated 
after experience in the operation. The main points 
to attend to are, it seems, two:—the chlorine and 
the alcohol must both be absolutely free from mois¬ 
ture, and the current of chlorine gas must be main¬ 
tained slowly but continuously from beginning to end. 
The chlorine is rapidly absorbed at first by the alco¬ 
hol, but after a time it is necessary to heat the spirit 
until towards the close of the operation it boils. 
This must of course be done in an apparatus con¬ 
nected with a proper condensing arrangement, that 
the volatilized portions may not be lost. A yellow 
liquid ultimately results, which is agitated with oil 
of vitriol; the lighter part is separated and rectified 
from some fresh acid. The resulting anhydrous 
chloral is finally distilled from some quicklime, to 
remove hydrochloric acid, and then converted into 
the hydrate by mixing with the theoretical propor¬ 
tion of water. 
It is necessary to exclude water from the mate¬ 
rials employed, from the fact that clilorine in pre¬ 
sence of water acts upon organic bodies, not by 
substituting itself for their hydrogen, but by oxidiz¬ 
ing them. Consequently, when water is present, the 
aldehyd and acetic acid that are usually unavoid¬ 
ably produced in small quantity become the chief 
results of the reaction. 
It appears that alcoholate of chloral is the imme¬ 
diate offspring of the action of the chlorine, and that 
from this chloral is set free by the sulphuric acid 
afterwards used. Water is, however, certainly 
formed in small quantity by a secondary action, and 
therefore a little hydrate is probably present, as well. 
Theory of the Process .—There can be little doubt 
that the chloral results from the removal of two 
atoms of hydrogen from the alcohol with production 
of aldehyd, and the conversion of this body into 
chloral by the replacement of three of its atoms of 
hydrogen by three chlorine atoms. Of course, a 
large quantity of hydrochloric acid results simulta¬ 
neously. 
Third Series, No. 70. 
I. CoH 6 0 + C1 2 = C 2 H 4 0 + 2HC1. 
Alcohol. Aldehyd. 
II. C 2 H 4 0 d-3Cl 2 =:C 2 HCl 3 0 + 3HCl. 
Aldehyd. Chloral. 
And it is interesting to observe in connection with 
this, that from aldehyd itself chloral is obtainable 
by the action of chlorine, if precautions are taken to 
remove the hydrochloric acid as it is produced. 
Chloral, however, is not by any means the only 
resultant of the reaction of chlorine upon alcohol. 
The subordinate interchanges which go on at the 
same tune are complicated, and result mainly from 
two causes, one the influence of the hydrochloric 
acid generated,-and the other that of the chlorine, 
which affects, on the one hand, the matters to which 
the action of the hydrochloric acid gives birth, and 
on the other hand the impurities in the spirit. 
These must be examined separately. 
The action of the hydrochloric acid upon the un¬ 
altered alcohol gives rise to the formation of hydro¬ 
chloric ether or cliloride of ethyl. 
C 2 H 5 HO + HC1=C 2 H.C1 + H 2 0. 
Alcohol. Ethyl Cliloride. 
But hydrochloric acid, in the absence of water, or 
even in concentrated solution, is a powerful promoter 
of what is called condensation. It does this by tak¬ 
ing from two or more molecules of a compound body 
the elements of water, the residues of those two 
molecules uniting into one. 
In a great deal of the spirit employed on the Con¬ 
tinent in this manufacture aldehyd already exists in 
appreciable amount, and from this is formed a 
curious substance, which has been repeatedly ob¬ 
served and minutely examined. It is crotonic 
chloral, a body which stands in the same relation- 
sliip to crotonic aldehyd that ordinary chloral does 
to acetic aldehyd. It is formed in this way:—From 
two molecules of aldehyd a molecule of water is de¬ 
tached by the hydrochloric acid. This gives cro¬ 
tonic aldehyd, wliich, at the moment of its forma¬ 
tion, is attacked by the chlorine passing through the 
liquid, and converted into the new chloral. 
2(C 2 IT 4 0) — H 2 0 = C 4 H 6 0 
Aldehyd. Crotonic Aldehyd. 
and C 4 H 6 0 + 3C1 2 =: C 4 H 3 C1 3 0 + 3HC1. 
Crotonic Aldehyd. Crotonic Chloral. 
It is possibly by an analogous reaction that the 
small quantities of ether which it is believed are 
formed in the process may also result. This is, 
however, open to question. 
The foreign substances which occur in spirit of 
wine are very numerous. 
Water .—Although but minute quantities are pre¬ 
sent in the alcohol to start with, the amount, as 
already explained, is liable to increase. To this 
cause is due the production of acetic acid. 
C 2 H 6 0 + 0 H 2 + Cl, = C 2 H 4 0 2 + 2 H Cl. 
Alcohol. Acetic Acid. 
Fousel Oil .—This name is applied to the mixture 
of alcohols of higher boiling-point than ordinary 
alcohol, which is separated from spirit by the process 
of rectification. Propylic, butylic, amylic alcohols, 
and the corresponding iso-alcohols are among the 
constituents of this complex mixture, which ha^ e 
been observed. Acted upon by chlorine they pro¬ 
bably yield products analogous to those formed from 
ordinary etliylic alcohol, but inasmuch as they are 
