an essential of gastric digestion, and thereby arrests this
process. The desirable effects produced by alcohol on
the stomach are worth obtaining only in cases of acute
diseases. In chronic disease and in health the use of
alcohol as an aid to digestion is without the support of
clinical or laboratory experience, the beneficial action
being at least neutralized by undesirable effects produced
elsewhere. The continued use of large doses of alcohol produces
chronic gastritis, in which the continued irritation has led
to overgrowth of connective tissue, atrophy of the gastric
glands and permanent cessation of the gastric functions.
A single dose of concentrated alcohol (e.g. brandy) produces
very valuable reflex effects, the heart beating more rapidly and
forcibly, and the blood-pressure rising. Hence the immediately
beneficial effect produced in the cases of ``fainting'' or
syncope. After absorption, which is very rapid, alcohol
exerts a marked action upon the blood. The oxygen contained
in that fluid, and destined for consumption by the tissues,
is retained by the influence of alcohol in its combination
with the haemoglobin or colouring matter of the red blood
corpuscles. Hence the diminished oxidation of the tissues,
which leads to the accumulation of unused fat and so to the
obesity which is so often seen in those who habitually take
much alcohol. The drug exerts a noteworthy action upon the
body-temperature. As it dilates the blood-vessels of the
skin it increases the subjective sensation of warmth. The
actual consequence, however, is that more heat than before
is necessarily lost from the surface of the body. Alcohol
also diminishes the oxidation which is the main source of the
body-heat. It follows that the drug is an antipyretic, and
it is hence largely used in fevers as a means of reducing the
temperature. This reduction of the temperature, carried to an
undesirable extreme, is the reason why the man who has copiously
consumed spirits ``to keep out the cold'' is often visited with
pneumonia. The largest amount of alcohol that can be burnt up
within the healthy body in twenty-four hours is 1 1/2 oz., but
it must be consumed in great dilution and divided into small
doses taken every four hours. Otherwise the alcohol will for
the most part leave the body unused in the urine and the expired
air. In fever the case is different. The raised temperature
appears to facilitate the oxidation of the substance, so that
quantiries may be taken and completely utilized which would
completely intoxicate the individual had his temperature been
normal. It follows that alcohol is a food in fever, and its
value in this regard is greatly increased by the fact that
it requires no primary digestion, but passes without changes,
and without needing change, to the tissues which are to use
it. According to Sir Thomas Fraser nothing else can compete
with alcohol as a food in desperate febrile cases, and to
this use must be added its antipyretic power already explained
and its action as a soporific. During its administration in
febrile cases the drug must be most carefully watched, as its
action may prove deleterious to the nervous system and the
circulation in certain classes of patient. The state of the
pulse is the best criterion of the action of alcohol in any
given case of fever. The toxicology of alcohol is treated
in other articles. It includes acute alcoholism (i.e.
intoxication), chronic alcoholism, delirium tremens, and
all the countless pathological changes--extending to every
tissue but the bones, and especially marked in the nervous
system-- which alcohol produces. (See DRUNKENNESS: DELIRIUM.)
After death the presence of alcohol can be detected in all the body
fluids. Its especial affinity for the nervous system is indicated
by the fact that, when all traces of it have disappeared elsewhere,
it can still be detected with ease in the cerebro-spinal fluid.
ALCOHOLS, in organic chemistry, a class of compounds which may
be considered as derived from hydrocarbons by the replacement of
one or more hydrogen atoms by hydroxyl groups. It is convenient
to restrict the term to compounds in which the hydroxyl group is
attached to an aliphatic residue; this excludes such compounds
as the hydroxy-benzenes, naphthalenes, &c., which exhibit many
differences from the compounds derived from the aliphatic alkyls.
Alcohols are classified on two distinct principles, one depending
upon the number of hydroxyl groups present, the other on the
nature of the remaining groups attached to the carbon atom which
carries the hydroxyl group. Monatomic or monohydric alcohols
contain only one hydroxyl group; diatomic, two, known as glycols
(q.v.); triatomic, three, known as glycerols (q.v.); and so on.
The second principle leads to alcohols of three distinct
types, known as primary, secondary and tertiary. The genesis
and formulation of these types may be readily understood by
considering the relation which exists between the alcohols
and the parent hydrocarbon. In methane, CH4, the hydrogen
atoms are of equal value, and hence only one alcohol,
viz. CH3OH, can be derived from it. This compound,
methyl alcohol, is the simplest primary alcohol, and it is
characterized by the grouping .CH2OH. Ethane, C2H6, in
a similar manner, can only give rise to one alcohol, namely
ethyl alcohol, CH3CH2OH, which is also primary. Propane,
CH3CH2CH3, can give rise to two alcohols --a primary
alcohol, CH3CH2CH2OH (normal propyl alcohol), formed
by replacing a hydrogen atom attached to a terminal carbon
atom, and a secondary alcohol, CH3.CH(OH).CH3 (isopropyl
alcohol), when the substitution is effected on the middle carbon
atom. The grouping CH.OH characterizes the secondary alcohols;
isopropyl alcohol is the simplest member of this class.
Butane, C4H10, exists in the two isomeric forms--normal
butane, CH3.CH2.CH2.CH3, and iso-butane, CH(CH3)3.
Each of these hydro-carbons gives rise to two alcohols:
n-butane gives a primary and a secondary; and iso-butane a
primary, when the substitution takes place in one of the
methyl groups, and a tertiary, when the hydrogen atom of the
:CH group is substituted. Tertiary alcohols are thus seen to
be characterized by the group :C.OH, in which the residual
valencies of the carbon atom are attached to alkyl groups.
In 1860 Hermann Kolbe predicted the existence of secondary and
tertiary alcohols from theoretical considerations. Regarding
methyl alcohol, for which he proposed the name carbinol, as
the simplest alcohol, he showed that by replacing one hydrogen
atom of the methyl group by an alkyl residue, compounds of the
general formula R.CH2.OH would result. These are the primary
alcohols. By replacing two of the hydrogen atoms, either
by the same or different alkyls, compounds of the formula
(R.R1)CH.OH (i.e. secondary alcohols) would result; while
the replacement of the three hydrogen atoms would generate
alcohols of the general formula (R.R1.R2)C.OH, i.e.
tertiary alcohols. Furthermore, he exhibited a comparison
between these three types of alcohols and the amines. Thus:--
R.NH2 (R1R2)NH (R1R2R3)N
R.CH2OH (R1R2)CH.OH (R1R2R3)C.OH
Primary. Secondary. Tertiary.
To distinguish Priinary, Secondary and Tertiary Alcohols.--
Many reactions serve to distinguish these three types of
alcohols. Of chief importance is their behaviour on oxidation.
The primary alcohols are first oxidized to aldehydes (q.v.),
which, on further oxidation, yield acids containing the same
number of carbon atoms as in the original alcohol. Secondary
alcohols yield ketones q.v.), which are subsequently
oxidized to a mixture of two acids, Tertiary alcohols yield
neither aldehydes nor ketones, but a mixture of two or more
acids. Another method is based upon the different behaviour
of the corresponding nitro-alkyl with nitrous acid. The
alcohol is first acted upon with phosphorus and iodine, and
the resulting alkyl iodide is treated with silver nitrite,
which gives the corresponding nitro-alkyl. The nitro-alkyl is
then treated with potassium nitrite dissolved in concentrated
potash, and sulphuric acid is added. By this treatment a
primary nitro-alkyl yields a nitrolic acid, the potassium
salt of which forms an intense red solution; a secondary
nitro-alkyl forms a pseudo nitrol, which gives an intense blue
solution, while the tertiary compound does not act with nitrous
acid. The reactions outlined above may be thus represented:--
//NOH
R.CH2OH --> R.CH2I --> R.CH2.NO2 --> R.C<
Primary alcohol. \NO2
Nitrolic acid.
R\ R\ R\ /NO2
>CH.OH --> >CH.I --> >CH.NO2 --> >C<
R1/ R1/ R1/ \NO
Secondary alcohol. Pseudo nitrol.
(R1R2R3)C.OH --> (R1R2R3)C.I --> (R1R2R3)C.NO2
Tertiary alcohol.
By heating to the boiling point of naphthalene (218 deg. ) tertiary
alcohols are decomposed, while heating to the boiling point of
anthracene (360 deg. ) suffices to decompose secondary alcohols, the
primary remaining unaffected. These changes can be followed out by
determinations of the vapour density, and so provide a method for
characterizing alcohols (see Compt. Rend. 1904, 138, p. 984).
Preparation.
Alcohols may be readily prepared from the corresponding alkyl
haloid by the action of moist silver oxide (which behaves as
silver hydroxide): by the saponification of their esters; or
by the reduction of polyhydric alcohols with hydriodic acid,
and the subsequent conversion of the resulting alkyl iodide
into the alcohol by moist silver oxide. Primary alcohols
are obtained by decomposing their sulphuric acid esters (from
sulphuric acid and the olefines) with boiling water; by the
action of nitrous acid on primary amines; or by the reduction
of aldehydes, acid chlorides or acid anhydrides. Secondary
alcohols result from the reduction of ketones; and from the
reaction of zinc alkyls on aldehydes or formic acid esters.
/C2H5 /C2H5
CH3CHO --> CH3.CH< --> CH3.CH<
\OZnC2H5 \OH
Acetaldehyde. Methyl ethyl carbinol.
//O /OZnCH3 /CH3 /CH3
HC HC<-CH3 --> R.C<-OZnCH3 --> R.C<-OH
\OC2H5 \Cl \CH3 \CH3
Formic ester. Isopropyl alcohol.
Tertiary alcohols may be synthesized by a method devised
by A. Butlerow in 1864, who thus discovered the tertiary
alcohols. By reacting with a zinc alkyl (methyl or ethyl) on
an acid chloride, an addition compound is first formed, which
decomposes with water to give a ketone. If, however, a second
molecule of a zinc alkyl be allowed to react, a compound is
formed which gives a tertiary alcohol when decomposed with water.
//O /CH3 /CH3 /CH3
R.C R.C<-OZnCH3 --> R.C<-OZnCH3 --> R.C<-OH
\Cl \Cl \CH3 \CH3
Acid chloride. Tertiary alcohol.
It is interesting to note that, whereas zinc methyl and ethyl
