hydrogen of the OH group can be readily replaced by sodium
or potassium :
2CH 3 .OH + 2Na = 2CH 3 ONa + H 2 ,
Methyl alcohol. Sodium methylate.
and the hydroxyl group, as a whole, is substituted by chlorine
by the action of PC1 5 :
CH 3 .OH + PC1 5 = CH 3 C1 + POC1 3 + HC1,
Methyl alcohol. Methyl chloride.
while, on the other hand, the synthesis of methyl alcohol can
be effected by heating methyl chloride with water in sealed
tubes to a temperature of 1 20 C. :
CH..C1 + H . OH = CH,OH + HC1.
o o
Very important also is the ability of methyl alcohol to form
ethereal salts, in which the methyl group of the alcohol plays
ETHYL ALCOHOL
47
the same part as the metal in an inorganic salt. These are
entirely similar to those derived from ethyl alcohol, which will
presently be considered in more detail.
Ethyl Alcohol, C 2 H & . OH, is prepared on a very large
scale, though not in the pure state, by the fermentation of
starch or sugar contained in various cereals and fruits. The
term fermentation is applied to a process of chemical decom-
position, depending for its continuance upon the influence of
some " ferment," which yet seems to take no part in the
chemical reaction, and
is able to transform a
disproportionately large
amount of the ferment-
ing substance. Fer-
ments may be organised
or unorganised. In the
first case they are living-
micro-organisms whose
activity as ferments is
connected with their vital
processes, and ceases
with their death. The
unorganised ferments
are definite chemical
Substances Called en- F , G 23 ._ Pure Yeast under the microscope.
zymes, but no satis-
factory explanation has been given of their action.
In the case of the alcoholic fermentation of sugar we are
concerned with an organised ferment, the yeast plant. This is
a minute and structurally very simple plant, which, placed in a
solution of sugar, is able to grow and multiply, provided the
temperature be maintained between the limits of 5 and 40
C. ; at the same time the sugar is gradually decomposed
mainly according to the equation :
Glucose.
Alcohol.
but there is always produced a certain amount of other sub-
stances, of which the most important are higher alcohols and
their ethereal salts ; these together constitute the fusel oil of
4 8
ALCOHOLIC LIQUORS
the crude alcohol, and to its different nature are due both the
pleasant flavour of good wine and the foul taste of cheap
spirit.
EXPT. 10. Dissolve 10 grams of sugar in 200 c. c. of warm water.
Place in a 250 c. c. flask and add some yeast. Fit the flask with a cork
and tube to pass any gas evolved through lime-water.
Arrange a parallel experiment, using glucose or honey instead of cane-
sugar.
Notice that fermentation soon begins in the latter case, and that COo
is evolved. The cane-sugar is much slower.
The most important alcoholic beverages may be classified
as follows :
(a) Beer or ale, made by fermentation of the sugar in
malted cereals (especially barley), and containing from 4 to 10
per cent of alcohol.
The malting is itself a fermentation process. The active
principle is the diastase
of the malt, an unor-
ganised ferment which
converts the starch of
the cereal into sugar.
(b) Wines, made by
fermenting the sacchar-
ine juice of ripe fruit.
No ferment is artificially
introduced, as in the
case
but
floating as dust in the
air fall into the must
and start fermentation.
Wines contain from 10
to 20 per cent of al-
cohol.
(c) Spirits are much richer in alcohol (30 per cent and up-
wards), and are made by distillation of the weaker spirituous
beverages. A large quantity of cheap spirit is made by
fermentation of malted potato- starch, and from the same
source the bulk of the alcohol used in the arts and manu-
factures is obtained.
of brewing beer,
micro - organisms
FIG. 24. Bloom of Grapes under the microscope,
showing yeast cells at A.
ALCOHOLOMETRY
49
Methylated Spirit. In order that the high price of
alcohol due to the heavy duty upon it may not seriously inter-
fere with its use for other purposes than as the basis of intoxi-
cating beverages, the so-called methylated spirit is allowed to
be sold duty free. This is a mixture of alcohol containing 20
per cent of water with substances which make the spirit prac-
tically undrinkable, but do not seriously interfere with its use
for other purposes, and at the same time are difficult to
remove. The present regulations order that certain small
proportions of wood-spirit and of light petroleum shall be em-
ployed as the methylating mixture.
Alcoholometry. The method in general use for deter-
mining the percentage of alcohol present in a given sample of
liquid depends upon the gradual variation in the specific
gravity of mixtures of alcohol and water as the proportion of
alcohol is altered. The following short table illustrates the
way in which the specific gravity changes :
Parts by
weight of
alcohol in 100
of mixture.
Specific gravity.
Parts by
weight of
alcohol in 100
of mixture.
Specific gravity.
O
IO
20
30
I.OOO
.984
.972
.958
60
70
80
90
.896
.872
.848
.823
40
.940
IOO
794
5
.918
It would, of course, be quite incorrect to apply this table to
such a liquid as beer or wine, in which other substances than
water and alcohol are present, and influence the specific
gravity. What is done in such cases is to take 100 c.c. of the
liquid, distil over two-thirds of it, and make up the distillate
to 100 c.c. by adding water; we then have 100 c.c. of liquid
containing all the alcohol which was originally present, but
freed from the sugar and other non-volatile materials. By
taking the specific gravity of this distillate we find at once
PROOF-SPIRIT
from the table what percentage of alcohol there was in the
beer or wine taken.
The nomenclature employed in this country for stating the
results is very complicated. The standard taken is proof-
spirit, originally spirit of such strength that when poured
over gunpowder and set fire to, it was just able to ignite the
powder, while a more watery spirit failed to do so. The present
legal definition of proof-spirit is that it should be of the specific
gravity , which corresponds to a proportion of 49.3 parts
by weight of pure alcohol in i oo of the mixture. The strength
of spirituous liquors is generally expressed as being so many
FIG. 25. Distillation of small quantities.
degrees over or under proof ; thirty degrees over proof implies
that I oo parts of the spirit contain as much alcohol as 1 30
parts of proof-spirit.
Pure ethyl alcohol, absolute alcohol, is obtained from
rectified spirit by treatment with quicklime and subsequent
distillation. The spirit is allowed to stand over lumps of
quicklime for several hours before distillation, and even then
it is usually necessary to repeat the process before the alcohol
is entirely freed from water. Whether this is the case can be
made certain by shaking some anhydrous copper sulphate (a
white powder obtained by heating the crystallised blue salt
for several hours at 180 C.) with the alcohol, when the
presence of even a trace of water will be detected by the white
copper sulphate becoming tinged with blue. Anhydrous
VI SYNTHESIS OF ALCOHOL 51
alcohol is very hygroscopic, and must be preserved in well-
stoppered bottles.
Pure ethyl alcohol has a slight pleasant smell, and boils at
a considerably lower temperature than water, viz. 78-3 C.
Its specific gravity is .794 at I5C. It mixes readily with
water, and can be used as a solvent for many substances (resins
and other organic compounds) which are insoluble in water.
Other methods besides that of fermentation of sugar may
be used for the preparation of ethyl alcohol, but are of
theoretical interest only ; the most important of them are :
I. Ethylene, C 2 H 4 , is absorbed by concentrated sulphuric
acid with formation of ethyl-sulphuric acid :
C,H 4 + H,S0 4 - C 2 H 5 . HS0 4 ,
and this, when treated with hot water, is decomposed into
alcohol and sulphuric acid :
C 2 H ft . HSO 4 + H 2 O = C 2 H 5 OH + H 2 SO 4 .
As ethylene can be prepared by passing a mixture of acetylene and
hydrogen over platinum sponge, and acetylene has been made by direct
union of carbon and hydrogen, this gives a way by which it would be
possible to effect the synthesis of ethyl alcohol from its elements.
II. Ethyl iodide, bromide, or chloride, when heated with
water (or more readily, when heated with solution of an
alkali) to a high temperature, yields ethyl alcohol,
C 2 H 5 I + H,O = C a H 5 OH + HI.
This last method of preparation is strong evidence for the
constitutional formula, CH 3 . CH 2 OH, which has been adopted;
other evidence is forthcoming in the reactions of ethyl alcohol,
all of which are well represented by this formula. Of these
reactions the following only will be mentioned here :
I. With metallic sodium or potassium, an alcoholate is
formed and hydrogen is evolved :
2C 2 H 5 . OH + 2Na=2C 2 H 5 ONa + H :J .
Sodium ethylate.
The alcoholates are readily oxidised, and are decomposed by water
with formation of alcohol and a hydrate :
C,H D ONa + H.,0 = C,H 5 OH + NaOH.
52 PROPYL ALCOHOL
II. With PC1 5 , or HC1 in presence of a dehydrating agent,
ethyl chloride is formed :
C 2 H 5 OH + HC1 = C 2 H 6 C1 + H 2 0.
Zinc chloride may be used as the dehydrating agent. Similar reactions
occur with HBr . HI, also PBr 3 and PI 3 .
III. With acids the alcohol combines to form ethereal salts
(see p. 55):
C 2 H 5 OH + H 2 S0 4 = C 2 H 5 . HS0 4 + H 2 O.
Alcohol and sulphuric acid yield ethyl hydrogen sulphate and
water.
Propyl Alcohol, C 3 H g O, is the next higher homologue of
ethyl alcohol, and is the lowest member of the series for which
isomeric forms are possible. If we proceed from ethyl alcohol,
CH 3 .CH 2 OH, by substituting a methyl group, CH 3 , fora
hydrogen atom, we find that two isomeric alcohols are in-
dicated for the formula C.>H Q O :
O o
CH 3 .CH 2 .OH CH 3 .CH 2 .OH
gives gives
* TH *
CH 3 .CH 2 .CH OH ::"3>CH.OH
CH 3
Normal propyl alcohol. Isopropyl alcohol,
and both of these isomers are well-known substances.
A third isomer. CH 3 . CH 2 . O . CH 3 , exists, but is not an alcohol ; it is
methyl-ethyl ether.
Normal propyl alcohol is found in fusel oil in considerable
quantity, and can also be prepared synthetically by the action
of water or potash solution upon the corresponding iodide :
CH :{ . CH 2 . CH 2 I + H 2 O = CH 3 . CH 2 . CH 2 OH + HI.
Propyl iodide. Propyl alcohol.
Isopropyl alcohol does not occur in fusel oil, but can only
vi PRIMARY, SECONDARY, AND TERTIARY ALCOHOLS 53
be obtained by synthetical methods, as by the action of water
upon isopropyl iodide :
CH 3 . CHI . CH 3 + H L ,0 = (CH 3 ) 2 CHOH + HI. '
Both these alcohols are liquids of pleasant smell boiling at
a somewhat lower temperature than water. Chemically, both
exhibit the reactions characteristic of alcohols which are
mentioned on p. 51, but they differ markedly from one another
in their behaviour towards oxidising agents. Normal propyl
alcohol, when oxidised, yields first an aldehyde and then an
acid (propionic) :
CH 3 . CH 2 . CH 2 OH ^CH 3 . CH 2 . CHO ^CH 3 . CH 2 . CO 2 H
Primary alcohol. Aldehyde. Acid.
a behaviour completely parallel to that of methyl and ethyl
alcohols, and characteristic of all alcohols containing the group
CH., . OH. Such alcohols are termed primary alcohols.
Isopropyl alcohol, on the other hand, yields first a ketone, and
this, on further oxidation, breaks up into several acids con-
taining a smaller number of carbon atoms in the molecule.
This behaviour is characteristic of secondary alcohols,
which contain the group CHOH united to two alkyl groups :
CH 3 CO.,H
(CH 3 ) 2 . CHOH ^(CH 3 ) CO > and "
H . CO,H
Secondary alcohol. Ketone. Lower acids.
The next alcohol we shall consider, butyl alcohol, will furnish
us with a case of a ^tertiary alcohol. Such an alcohol
contains the group C . OH combined- with three alkyl groups,
and on oxidation breaks up at once into bodies containing
fewer carbon atoms in the molecule :
(CH 3 ) 3 . COH >- bodies with fewer carbon
atoms in the molecule.
Tertiary alcohol.
Butyl Alcohols, C 4 H 1(J O, occur in four isomeric forms.
Their derivation from the two propyl alcohols by substitution
54 BUTYL ALCOHOLS
of a methyl group for a hydrogen atom is shown in the
following table :
CH 3 . CH. . CH 2 OH yields (i.) CH 3 . CH 2 . CH 2 . CH 2 OH
Normal butyl alcohol.
(ii.) (CH 3 ) 2 CH . CH 2 OH
Isobutyl alcohol.
(iii.) CH 3 . CH 2 . CH(CH 3 ) . OH
Secondary butyl alcohol.
(CH 3 ) 2 CHOH yields (iv.) CH 3 . CH 2 . CH(CH 3 ) . OH
(v.) (CH 3 ) 3 COH
Tertiary butyl
alcohol.
but of these (iii.) and (iv.) are identical, so that the full
number of isomers indicated by theory is four, and this is also
the number actually known. Only one of them is sufficiently
important to be further mentioned. Isobutyl alcohol,
(CH 3 ).,CH . CH 2 OH, can be separated from fusel oil, in which
it is present, by fractional distillation. It is a liquid boiling
at 107 C., and possessing the characteristic smell of fusel oil.
Amyl Alcohol, C 5 H 12 O. For this alcohol there are eight
isomers indicated by theory, and of these all are now known.
Two of these are largely present in fusel oil, and their mixture
is the ordinary " amyl alcohol," a liquid of unpleasant smell,
which boils at about 130 C. It is obtained from fusel oil by
fractional distillation.
QUESTIONS ON CHAPTER VI
i. What tests would you apply to a substance given to you, in order
to discover whether it is an alcohol or not ?
z. How is methyl alcohol obtained commercially ? Mention important
points in which it resembles, and others in which it differs from, ethyl
alcohol.
3. Give an account of the chief chemical changes which occur in
brewing beer from barley. How would you determine the percentage of
alcohol in a given sample of beer?
4. What are the characteristics of the three classes of alcohols,
primary, secondary, and tertiary?
5. Give an account of the two isomeric alcohols possessing the formula
C,H H O.
CHAPTER VII
ETHEREAL SALTS
ETHERS MERCAPTAN
Ethereal Salts. As has been already mentioned, the
alcohols are able to combine with acids somewhat in the same
way as the inorganic metallic hydrates. The products in the
case of the latter are termed salts, while those formed from
the alcohols go by the name of " ethereal salts " or " esters " :
CH 3 .OH + HN0 3 CH 3 NO 3 + H 2 O,
Methyl nitrate, an ethereal salt.
K.OH + HNO 3 = KNO 3 + H 2 O,
Potassium nitrate, a salt.
There are, however, several differences between the two
classes of reactions, of which the most important is that the
reaction does not occur so readily or completely with the
alcohol as with the base ; often, especially when the acid is
not one of the strongest, it is necessary to employ some
dehydrating agent to favour the reaction.
The reason is that the tendency to the reversed change, such as
C 2 H 5 HS0 4 + H 2 = CoH 5 OH + H 2 SO 4 ,
becomes greater as the quantity of water present increases. By combining
this water with some hygroscopic substance its effect is diminished.
The most important ethereal salts of ethyl alcohol are
perhaps the acetate and acid sulphate.
ETHYL ACETATE
Ethyl Acetate, CH 3 . CO 2 C 2 H 5 , can be prepared by
heating a mixture of alcohol and acetic acid with strong
sulphuric acid :
Ethyl alcohol. Acetic acid. Ethyl acetate.
It is a volatile liquid with a strong fragrant smell. Its forma-
tion in the way mentioned is employed as a test for acetic
acid or an acetate.
FIG. 26. Saponification of ethyl acetate by boiling with water and an alkali ;
the reflux condenser prevents loss by volatilisation.
EXPT. ii. In a test tube mix equal volumes of spirits of wine and
strong sulphuric acid. Add some pieces of a solid acetate, and notice the
fragrant smell of ethyl acetate which is evolved on gently heating the
mixture.
Like other ethereal salts, ethyl acetate is readily split up
into the alcohol and acid from which it is formed. The change
may be accomplished by heating with water in sealed tubes,
or more readily by boiling with a dilute solution of an alkali :
SAPONIFICATION 57
CH 3 C0 2 C 2 H 5 + H 2 = CH 3 C0 2 H + C 2 H 5 OH.
Ethyl acetate. Acetic acid. Ethyl alcohol.
Changes of this kind, in which an ethereal salt is broken
up by the action of water into the alcohol and acid from which
it is formed, are often spoken of as cases of saponification.
All such changes occur more readily when an alkali or an acid
is present in the water.
. Ethyl acetate is used in the artificial preparation of per-
fumes and flavouring essences. Several other ethereal salts,
similar in composition, are also used for these purposes, as
Ethyl butyrate, C.,H-CO.,C.,H 5 , in pine-apple essence.
Amyl acetate, CH 3 CO 2 C 5 H il , in pear essence.
These and similar compounds also constitute the bulk of the
natural essences extracted from the plants themselves.
Ethyl Hydrogen Sulphate, C 2 H 5 HSO 4 , is formed when
alcohol and strong sulphuric acid are mixed. It can be
separated from unaltered sulphuric acid by means of its barium
salt, which is soluble in water, whereas barium sulphate is
insoluble. Ethyl hydrogen sulphate behaves as a monobasic
acid, and when liberated from its barium salt, can only be
obtained as a thick uncrystalli sable syrup.
Two of its reactions are important :
(a) When heated alone it splits up into ethylene and sul-
phuric acid :
In this case a larger proportion of sulphuric acid is used,
and the temperature of the reaction is higher.
(b) When heated with alcohol it forms ether and sulphuric
acid :
C,H 5 HS0 4 + C 2 H 5 O.H = (C 2 H 5 ) 2 + H 2 SO 4 .
In this case alcohol is present in larger quantity, and the
decomposition proceeds at a lower temperature.
ETHYL ETHER
ETHER
Ether is now a term applied to a whole class of compounds,
all of them oxides of organic radicles, such as methyl and
ethyl. Methyl ether is (CH 3 ) 2 O, and ethyl ether (C 2 H.) 2 O.
This latter is the ordinary "sulphuric ether" of the chemists,
the name being given from the fact that sulphuric acid is used
in its manufacture, although the substance obtained has no
sulphur whatever in its composition.
Ethyl Ether, (C 2 H 5 ) 2 O, is ordinarily prepared by the action
of ethyl-sulphuric acid upon alcohol : *
C 2 H 5 HS0 4 + C 2 H 6 OH - (C 2 H 5 ) 2 + H 2 SO 4 .
EXPT. 12. In practice a mixture of alcohol and sulphuric acid (consist-
ing, therefore, largely of ethyl-sulphuric acid) is heated in a flask to about
140 C., and then a slow stream of alcohol is allowed to flow into the
heated liquid. The vapours given off are condensed, and yield a mixture
of water, alcohol, and ether. The layer of ether is separated, dried over
quicklime, and redistilled.
FIG. 27. Preparation of Ether.
Ethyl ether is a colourless mobile liquid, boiling at 35 C.
Its vapour is very heavy, and also readily inflammable, so that
care must be exercised in working with ether in the neighbour-
hood of a flame. The smell of ether is pleasant, but when
inhaled in quantity the vapour produces insensibility, and is
MERCAPTAN 59
used as an anaesthetic in cases where chloroform is not per-
missible on account of its depressing action v upon the heart.
When drunk in the liquid state ether produces a peculiar kind
of short-lived intoxication, the after effects of which are very
injurious to the health.
The constitution of ether is not evident from the mode of
formation given above, and its reactions are mostly not of a
character to throw light upon this point. The preparation
from ethyl iodide and sodium ethylate (see p. 51),
C 2 H 5 I + C,H.ONa = C 2 H 5 . O . C 2 H 5 + Nal,
is, however, strong evidence in support of the view that ordinary
ether is oxide of ethyl.
MERCAPTAN AND ETHYL SULPHIDE
A large number of organic bodies are known in which it
seems that an atom of sulphur plays the part of an atom of
oxygen in closely related compounds. Such are the mercaptans
(e.g. C 2 H 5 . SH), which correspond to the alcohols (C 2 H 5 . OH),
and the alky I sulphides, e.g. (C H 5 ) S, which correspond to the
ethers ( (C 2 H 5 ) 2 O).
Ethyl Mercaptan, C 2 H 5 . SH, is formed by the action of
potassium sulphydrate, KSH, upon ethyl bromide or iodide :
C 2 H 5 Br + KSH = C.,H 5 . SH + KBr
c.f. C 2 H.Br+KOH = C 2 H 3 . OH + KBr.
It is a volatile liquid of very strong and unpleasant odour.
The hydrogen of the SH group is more readily replaced by
metals than the corresponding H atom in alcohols. Not only
does mercaptan react with sodium and potassium, but also
with the oxides of heavy metals, such as mercury :
HgO + 2 C 2 H. . SH = (C 2 H 5 S),Hg + H 2 O,
(hence the origin of the name mercaptan, mercurium aptans).
Ethyl Sulphide, (C H-) S, can be prepared,
60 ETHYL SULPHIDE CHAP, vn
(1) By acting on potassium sulphide, K 2 S, with ethyl
bromide :
K 2 S + 2C 2 H 5 Br = (C 2 H 5 ) 2 S + 2KBr.
When a solution of caustic potash is saturated with HoS, the compound
K.HS is produced. If to this the same amount as was originally taken of
caustic potash solution be added, K 2 S is formed :
KOH + H 2 S = KSH + H 2 O
and KSH + KOH = K. 3 S+H 2 O.
(2) By treating the compound, C H 5 SK (obtained from
mercaptan by action of potassium), with ethyl bromide or iodide:
C 2 H 5 . SK + C 2 H 5 Br == (C 2 H 5 ) 2 S + KBr,
with which compare the method for preparing ether :
C 2 H 5 . OK + C 2 H 5 Br = (C 2 H fi ) 2 O + KBr.
Ethyl sulphide, like nearly all volatile organic compounds
which contain sulphur, has a most unpleasant smell.
QUESTIONS ON CHAPTER VII
1. What is meant by an " ethereal salt " ? How are such compounds
prepared ?
2. Mention some organic compounds of the class of ethereal salts
which are used in artificial flavouring essences.
3. What two substances can be prepared by heating ethyl alcohol with
sulphuric acid? How do the circumstances of the reaction need to be
modified in the two cases.
4. Why is ether regarded as ethyl oxide? What sulphur-containing
compound resembles it in composition, and how is it prepared?
CHAPTER VIII
ALDEHYDES AND KETONES
The Aldehydes are characterised by the presence of the
monovalent group, CHO, whose structure is represented by the
formula C^ R ; that is to say, the general behaviour of the
aldehydes is best represented by formulae in which this group
is connected with an alkyl group, such as methyl or ethyl.
The aldehydes occupy an intermediate position between the
acids and the alcohols by whose oxidation they are produced ;
thus, between ethyl alcohol, CH 3 . CH 2 OH, and acetic acid,
CH 3 COOH, stands the aldehyde CH 3 . CHO, or in general :
R . CH 2 OH - H 2 = RCHO ; and R . CHO + O = R . COOH ;
Alcohol. ^- Aldehyde. > Acid.
and the names of the aldehydes are best chosen so as to denote
their connection with a particular acid, the one into which
they are converted by addition of an atom of oxygen. Thus
the first member of the aldehyde series, H . CHO, is termed
formaldehyde, the second one, CH 3 . CHO, is acetaldehyde,
and so on.
Formaldehyde, H . CHO, is best obtained from the corre-
sponding alcohol, methyl alcohol, H . CH 9 OH, by oxidation ;
and this is most conveniently effected by passing warm air
saturated with the vapour of methyl alcohol over a glowing
copper spiral.
EXPT. 13. In the centre of a piece of combustion tubing, about a foot
in length, place a two-inch coil of copper gauze. Connect one end of the
6a FORMALDEHYDE
tube through two gas-washing bottles (the first empty, the second half full
of water) with an aspirator, and the other end with a gas-washing bottle
containing methyl alcohol, kept at about 50 by being placed in a beaker of
warm water.
Now turn on the water tap of the aspirator until a vigorous current of
vapour-laden air is passing over the copper gauze. Heat this gently with
a Bunsen burner until it begins to glow, when it will continue to do so
without any further use of the burner so long as the experiment is con-
tinued. In order to minimise the danger of cracking the glass tube when
the copper spiral suddenly begins to glow, it is well to support the spiral
on a thin piece of mica or of asbestos paper.
In this way are obtained only mixtures of formaldehyde
with methyl alcohol and water. It has not been found possible
to prepare pure formaldehyde, H . CHO, except in solution or