V. (Victor) Regnault.

Elements of chemistry : for the use of colleges, academies, and schools (Volume 2) online

. (page 69 of 87)
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formula C 10 H 8 0, which is generally written C 20 H 16 3 ; its equivalent
then corresponding to 4 volumes of vapour. Camphor is slightly
soluble in water, but dissolves more freely in alcohol, ether, and
concentrated acetic acid, and it burns with a white and smoky flame.
Camphor obtained from the family of the laurels, when dissolved in
alcohol, rotates toward the right.

Chlorine does not act readily on camphor, but when dissolved in
chloride of phosphorus PC1 3 , and subjected to the action of chlorine,
it yields chlorinated camphor G !i0 H. w C} 8 O ay which is separated from
the perchloride of phosphorus by washing it with water and weak
solutions of carbonate of potassa.

Camphor absorbs chlorohydric acid gas, and yields a colourless
liquid of the formula C 20 H 16 2 ,HC1, which is readily destroyed by
water, while camphor separates from it.

1517. Alkaline solutions exert no action upon camphor, but if its



640 ESSENTIAL OILS.

vapour be passed over potassic lime heated to 750 in a glass tube,
an acid called campholic is formed, which combines with the alkaline
substance, and which is then separated by dissolving in water and
supersaturating with chlorohydric acid. The precipitated cam-
phoric acid is dissolved in a mixture of alcohol and ether, from which
it separates in crystals, melting at 176, and boiling at 482. It is
insoluble in water, but very soluble in alcohol and ether. When
crystallized, its formula is C 20 H 18 4 , or more properly C 20 H 17 3 ,HO,
which corresponds to 4 volumes of vapour, for the density of the
vapour of campholic acid is 5.9. The formula of campholic acid
differs from that of camphor only by containing, in addition, the
elements of 1 equiv. of water. The formula of campholate of silver
is AgO,0,H w O,.

Campholate of lime CaO,C 20 H 17 3 is decomposed by heat into
carbonate of lime and a peculiar liquid called campholone C 19 H 17 0.

CaO,C^H 17 O s =CaO,C0 3 +C 19 H 17 0.

Campholic acid, distilled with anhydrous phosphoric acid, gives
off water and carbonic acid, while a carburetted hydrogen C^Hjg,
called campholen, which boils at 275, is formed.

1518. Cold nitric acid dissolves camphor, and parts with it
when diluted with water, while, by the application of heat, a peculiar
acid, called camphoric, is developed. In order to prepare this acid,
camphor is boiled for a long time with 10 times its weight of nitric
acid, and as the latter distils over, it is collected and poured back
into the retort. At the close of the operation, the excess of nitric
acid is driven off by evaporation, when the camphoric acid separates
in a crystalline mass, which is purified by dissolving it in carbonate
of potassa, and again separating it by means of nitric acid. Cam-
phoric acid is moderately soluble in boiling water, the greater por-
tion of it separating during cooling, while alcohol and ether dissolve
it readily. Its composition corresponds to the formula C li0 H. l6 Q 8 ;
and the camphor, by being converted into camphoric acid, combines
therefore with 6 equiv. of oxygen, which it takes from the nitric
acid. The formula of camphoric acid should be written C 20 H 14 6 ,
2HO, because it is a bibasic acid, and the general formula of its
salts is 2RO,C 30 H 14 6 . When heated it is decomposed into water
and a crystallized substance, boiling at 518, which, from its com-
position C 20 H 14 6 , may be regarded as anhydrous camphoric acid.
Camphoric acid, dissolved in alcohol, rotates toward the right.

1519. A species of camphor is extracted from the labiates, which,
in its chemical composition, appears identical with the camphor of
the laurels, but which rotates toward the left.

Borneo Camphor C 20 H 18 2 .

1520. From the dryabalanops camphora exudes a more or less
viscous oil, containing a crystallizable substance, of which the pro-



CAMPHORS. 641

perties are analogous to those of Japan camphor. It has been called
Borneo camphor, and is often found crystallized in old trunks of
the tree of the dryabalanops camphora. The camphor imported from
Borneo and Sumatra is in small, crystalline, colourless, and trans-
parent fragments, insoluble in water, but dissolving freely in alcohol
aud ether. It melts at about 383, and boils at about 419. Bor-
neo camphor differs from Japan camphor only by containing 2 ad-
ditional equiv. of hydrogen, which are consumed by heating it with
nitric acid ; the Borneo being converted into Japan camphor. The
liquid portion of the essential oil of the dryabalanops camphora is
essentially composed of a liquid carburetted hydrogen C 30 H 16 , called
borneen, boiling at about 320, and isomeric with oil of terpentine,
similarly to which it polarizes to the left, its rotatory power being
much greater. Nitric acid, after some time, and assisted by gentle
heat, converts borneen into Japan camphor, probably by the mere
absorption of oxygen.

Of some other Stearoptens analogous to Camphor.

1521. Stearoptens, exhibiting properties analogous to the cam-
phors, are found in a great number of vegetables ; but we shall only
mention them, for as yet they possess but little interest, and are but
little known.

Peppermint contains a stearopten of the formula C^H^Og, called
menthen C^Hj , which boils at 325.4. Oil of mint rotates toward
the right. , . .

Oil of cedar is composed of a crystallizable substance C 32 H 26 2 ,
and a liquid carburetted hydrogen, cedren C 3 H a4 , which boils at
478.4.

Oil of absinth, when purified, boils at 399. 2, and rotates to-
ward the right : its formula being C^H^O^ it is isomeric with Japan
camphor.

The root of elecampane (inula hellenium) contains a white crys-
tallizable substance, helenin, very soluble in alcohol and ether, melt-
ing at 161.6, boiling at about 536, and presenting the formula

c^o,.

An essential oil, composed of a liquid portion and a portion which
solidifies at 9.5, is extracted from roses; but the composition of the
two substances is not exactly known.

Oil of lavender contains a considerable proportion of Japan cam-
phor, and a volatile oil, the essential oil properly so called, which
has been used in the arts.

BENZOIC SERIES.
Oil of Bitter Almonds C 14 H 8 2 .

1522. Bitter almonds contain an essential oil, and a non-vola-
tile fatty oil, which latter is expressed by subjecting them to pres-
sure ; and if the pulp moistened with water be then distilled in an

VOL. II. 41



642 ESSENTIAL OILS.

alembic, a volatile oil, which falls to the bottom of the receiver,
passes over with the water. This is the oil of bitter almonds, mixed
with cyanohydric acid and two new substances, benzo'ine and ben-
.zoic acid, which shall soon be described. They are separated by
distilling the crude oil with lime and protosulphate of iron, reduced
to a paste with water ; the distilled oil being removed with a pipette,
and again distilled in a glass retort, collecting separately the first
portions, which contain water.

Oil $o bitter almonds is a colourless, very fluid liquid, having a
peculiar odour resembling that of cyanohydric acid ; and its density
is 1.048, while it boils at 348.8. Water dissolves about ^ of its
weight of it, while it is indefinitely soluble in alcohol and ether.
Its formula is C 14 H 6 3 , and it exerts no rotatory power.

Oil of bitter almonds rapidly absorbs the oxygen of the air, and
is converted into benzoic acid C 14 H 5 3 ,HO,

C 14 H 6 O a +20=C 14 H 6 3 ,HO.

Anhydrous benzoic acid is therefore derived from the oil of bitter
almonds, by the substitution of 1 equivalent of oxygen in the place
of 1 equivalent of hydrogen. Benzoic acid is also formed when oil
of bitter almonds is boiled with a solution of potassa ; the hydrated
potassa converting, at a high temperature, the oil of bitter almonds
wholly into benzoic acid, hydrogen being at the same time disen-
gaged. Chlorine, in contact with water, effects the transformation
in a very short time.

1523. Dry chlorine acts powerfully on oil of bitter almonds,
disengaging chlorohydric acid. When the evolution of the gas has
ceased, the liquor is heated to drive off the dissolved chlorine, and
a liquid of a penetrating and disagreeable odour is obtained, of the
density 1.106, and boiling at 383, which is monochlorinated oil of
bitter almonds C 14 H 5 C10 2 . Water, particularly when hot, decom-
poses it, forming chlorohydric and benzoic acids :

C 14 H 3 C10 2 +2HO=C 14 H 5 3 ,HO+HC1.

It has not yet been ascertained if the oil of bitter almonds forms
still more chlorinated products with chlorine. Bromine converts it
into monobrominated oil C 14 H 5 Br0 2 ; and monoiodinated oil C 14 H 5 I0 3
is obtained, crystallized in laminae, by distilling the monochlorinated
oil over iodide of potassium. By replacing the iodide of potassium
by sulphide of lead, or cyanide of mercury, a mono sulphuretted oil
C f 4 H^S0 2 , or a monocyanuretted oil C 14 H 5 Cy0 2 , is obtained. Some
chemists take a different view of the composition of these various
bodies, and admit the existence of an hypothetical radical C 14 H 5 ? ,
called benzoyl, which, combined with hydrogen, constitutes the oil
of bitter almonds C 14 H 5 2 ,H, thus forming a hydruret of benzoyl,
while benzoic acid is the oxide of benzoyl C 14 H 5 O a ,0. The chlori-
nated, brominated, cyanuretted, and sulphuretted oils are chlorides,
bromides, sulphides, and cyanides of benzoyl.



BENZOIC SERIES. 643

1524. The chlorinated oil of bitter almonds absorbs a large
quantity of ammoniacal gas, and is converted into a white crystal-
line compound C 14 H 7 N0 3 , or benzamide :

C 14 H 5 C10 2 +2NH 3 =NH 3) HCH-C 14 H S 2 ,NH 2 .

By treating the solid product of the reaction with water, the am-
moniacal salt which formed during the operation is dissolved, while
the benzamide alone remains, and may be crystallized %om its solu-
tion in alcohol. The relation of benzamide C 14 H 5 2 ,NH 3 with the
benzoate of ammonia (NH 3 ,HO),C 14 H 5 3 is the same as that of sul-
phamide S0 3 ,NH 3 with sulphate of ammonia (NH 3 ,HO),SO S ?

Benzamide dissolves in boiling water, and separates from it, on
cooling, in crystals, which melt at 239, and boil without change
at a higher temperature. Benzamide, treated with a cold alkaline
lye, undergoes no change, while at the boiling point it yields ben-
zoate of potassa and ammonia. Sulphuric acid also decomposes it,
sulphate of ammonia and benzoic acid being formed.

1525. The oil of bitter almonds, kept for several weeks at a
temperature of 100 to 120, with 20 times its volume of an aqueous
solution of ammonia, gives rise to a large number of crystals, which
are obtained isolated by removing the unaltered oil by ether. They
are dissolved in cold alcohol, which, by evaporation, deposits them
in a pure state, when their composition is represented by the formula
C^HjgNjj. It has been called hydrobenzamide^ and its formation is
represented by the following equation :



Hydrobenzamide, dissolved in alcohol, is readily converted, by
boiling, into ammonia and oil of bitter almonds. If hydrobenzamide
be boiled with a solution of caustic potassa, crystalline flakes are
formed, which, by recrystallization in alcohol, furnish colourless
crystals of the formula C 42 H 18 N 2 , like that of the original hydroben-
zamide, but which differ from it widely in its properties. This new sub-
stance, called amarin, is a true organic base, which forms crystal-
lizable salts with the acids. The formula of chlorohydrate of amarin
is C^H^N^HCl+HO, while that of the nitrate, which is but
slightly soluble in water, is

(C ffi H 18 N 2 ,HO),N0 5 .

1526. By adding chlorohydric acid to water which has distilled
with the oil of bitter almonds in the preparation of the latter sub-
stance, and evaporating it to dryness at a gentle heat, the residue
is composed of chlorohydrate of ammonia, and a peculiar substance,
called formobenzoylic acid, which is removed by dissolving it in
ether, when it is deposited after evaporation in the form of crystal-
line spangles, having the smell of bitter almonds and a strongly
acid reaction. This substance dissolves readily in water, alco-
hol, and ether, and its composition corresponds to the formula
C 16 H 8 6 , or rather C 16 H 7 5 ,HO, the equivalent of water being



644 ESSENTIAL OILS.

replaced, in the salts, by 1 equivalent of base. The formula of the
acid may be written C 14 H 6 2 ,C 2 H0 1 ,HO, which would represent it
as formed by the combination of 1 equivalent of oil of bitter almonds
and 1 equivalent of formic acid; and such, in fact, is the constitu-
tion assigned to it by its behaviour in a great number of chemical
reactions : thus, with oxidizing reagents, it yields carbonic acid, pro-
duced by the combustion of the formic acid and oil of bitter almonds.

Benzoic Acid C 14 H S 3 ,HO.

1527. Oil of bitter almonds rapidly absorbs the oxygen of the
air, and is converted into benzoic acid C 14 H 5 3 ,HO, which same
transformation is effected by exposing the oil to oxidizing reagents.
Benzoic acid is also extracted from a large number of vegetable and
animal substances, in which it generally does not exist already
formed, being the product of chemical reactions. In the laboratory
it is obtained from the resin of benzoin, by various processes, the
most simple of which consists in placing in an earthen or cast-iron
capsule 1 kilog. of coarsely powdered benzoin, covering the capsule
with a sheet of tissue-paper, the edges of which are pasted to the
vessel, and then surmounting it with a pasteboard cone. The cap-
sule being heated in a sand-bath for 3 or 4 hours, the vapours of
benzoic acid condense on the sides of the cone, after having tra-
versed the tissue-paper, which retains a small quantity of the empy-
reumatic oily substances, which would injure the product. This
process yields very pure benzoic acid, in the form of snow-white
crystals of an agreeable odour, but furnishes only a small portion
of the acid which the benzoin contains ; 1 kilog. of benzoin yielding
only 40 gm. of benzoic acid.

By the following process, as much as 140 gm. of benzoic acid
may be obtained from the same quantity of benzoin. The resin of
benzoin, finely powdered, is mixed with J of its weight of carbonate
of soda, and a sufficient quantity of water to make a liquid paste,
which is gently heated for several hours, stirring it continually to
prevent the melting of the resin. It is then heated with a larger
quantity of water, to dissolve the benzoate of soda, and the benzoic
acid is separated by the addition of a proper quantity of sulphuric
acid.

The resin of benzoin may also be treated with 3 times its weight
of alcohol at 0.75, and the benzoic acid saturated with carbonate of
soda dissolved in 8 parts of water ; and 2 parts of alcohol being
finally added, the liquid, when decanted, is distilled in order to
separate the greater portion of the alcohol. The resin which was
dissolved in the alcoholic liquor separates, while the solution only
contains the benzoate of soda, which is decomposed by sulphuric acid,
when the benzoic acid separates almost wholly from the liquor when
cool. By this method, 1 kilog. of benzoin will yield as much as 180
gm. of benzoic acid.



BENZOIC SERIES.



645



Benzoic acid crystallizes in lamellae or in flexible and brilliant
Bilky aciculae ; and it has, of itself, but little odour, while it gene-
rally preserves the smell of benzoin, particularly when it has been
prepared by simple distillation. It weakly reddens litmus, melts at
248, and boils at 464, exhaling copious vapours aj^ady at a tem-
perature of 300 or 400. The density of its vapourbeing 4.27, its
equivalent C 14 H 8 3 HO corresponds to 4 volumes of vapour. It re-
quires for its solution 25 parts of boiling and 200 parts of cold
water, while it dissolves in 2 parts of alcohol, and is also very solu-
ble in ether.

The general formula of the benzoates is RO,C 14 H 5 3 . The ben-
zoates of potassa, soda, and ammonia, are very soluble in water, and
crystallize with difficulty. The benzoate of lime is very soluble in
hot water, while cold water retains only about ^ of its weight of it.
The benzoate of silver is prepared by double decomposition, by
pouring a hot solution of nitrate of silver into a boiling solution of
an alkaline benzoate, when the benzoate of silver AgO,C 14 H 5 3 is
precipitated, during the cooling, in the form of colourless needles.

Chlorine acts on benzoic acid when assisted by the rays of the
sun, and produces chlorinated benzoic acid, retaining the principal
properties and capacity of saturation of free benzoic acid, the same
products being obtained by heating benzoic acid with the alkaline
hypochlorites or with mixtures of chlorohydric acid and chlorate of
potassa. Two chlorinated benzoic acids have been obtained in this
manner :

Monochlorinated benzoic acid C 14 H 4 C10 3 ,HO.



Terchlorinated



C 14 H 2 C1 5 3 ,HO.



Vinolenzoic Ether C 4 H 5 0,C 14 H 5 3 .




Fig. 685.



1528. In order to prepare this
ether, 2 parts of alcohol, 1 part of ben-
zoic acid, and 6 parts of concentrated
chlorohydric acid are heated, in a dis-
tilling apparatus, the liquid acid which
distils being returned several times to
the retort; when the benzoic acid is
thus almost wholly converted into ben-
zoic ether. But it is better to arrange
the operation as represented in fig. 685 :
the mixture is placed over a water-bath
in a flask A which is made to commu-
nicate with a refrigerator so arranged
as to allow the distilled liquid to gra-
dually fall back again. The liquid is
treated, first with water, and then with



a weak solution of carbonate of soda to remove the free benzoic



646 ESSENTIAL OILS.

y

acid, after which the benzoic ether is dried by digesting it over
chloride of calcium.

Benzoic ether is a colourless liquid of an oleaginous consistence,
boiling at 410, and of the density 1.054 at 50. The density of
its vapour being 5.41, its equivalent corresponds to 4 volumes of
vapour, and it is insoluble in water, but soluble in all proportions in
alcohol.

Methylbenzoic Ether C 2 H S 0,C 14 H.O S .

1529. By replacing, in the preceding operation, vinic by me-
thylic alcohol, methylbenzoic ether* is obtained as an oily liquid,
boiling at 226.4.

Sulphobenzoic Acid (C 14 H 4 3 ,S 2 5 ),2HO.

1530. If vapour of anhydrous sulphuric acid be introduced into
a dry and well-cooled flask containing benzoic acid, a semifluid mass
is formed, which is afterward treated with water to dissolve the
monohydrated sulphuric acid, and a peculiar acid, called sulphoben-
zoic, while the benzoic acid is separated unchanged. The acid
liquid is saturated with carbonate of baryta, when sulphobenzoate
of baryta alone remains in the liquid. By adding chlorohydric
acid, crystals of acid sulphobenzoate of baryta (BaO + HO),
(C 14 H 4 3 ,S 2 5 ) separate, which are redissolved in boiling water and
again crystallized by cooling. Sulphobenzoic acid may be sepa-
rated by decomposing a solution of this salt with sulphuric acid
added by drops : it is very soluble in water, remains undecomposed
even at 300, and may be obtained in a crystalline form by evapo-
ration.

Sulphobenzoic acid forms two series of salts of which the general
formulae are

2RO,(0 14 H 4 3 ,S 3 0) 5

(RO+HO),(C 14 H 4 O s ,S a 5 ).

It is therefore a bibasic salt.

It will be seen that when benzoic acid C 14 H 5 3 ,HO is treated with
anhydrous sulphuric acid, 2 equivalents of the latter enter into the
new compound, but only after having parted with 1 equivalent of
oxygen, which has formed water with 1 equivalent of hydrogen
given off by the benzoic acid ; according to the equation

C 14 H 5 8 ,HO+2S0 3 =(C J4 H 4 3 ,S 2 3 ),2HO.

Nitrobenzoic Acid C 14 H 4 (N0 4 )0 8 ,HO.
1531. Dilute nitric acid does not act readily on benzoic acid,

* More properly called benzoic mether. W. L. F.



BENZOIC SERIES. 647

but if the fuming acid be used, and in great excess, the benzoic
acid is dissolved with the disengagement of nitrous vapours, and
the liquid deposits, on cooling, crystals of nitrobeD(|oic acid C 14 H 4
(N0 4 )0 3 ,HO, which is purified by recrystallizations.

Nitrobenzoic acid is but slightly soluble in cold, but much more
so in boiling water ; and dissolves freely in alcohol and ether. If
crystallized into benzoate of lime, it takes the formula

CaO,C 14 H 4 (N0 4 )0 3 +2HO,
and that of baryta, BaO,C 14 H 4 (N0 4 )0 3 +4HO.

From its composition it may be admitted that the molecule of
nitrobenzoic acid C 14 H 4 (N0 4 )0 3 ,HO is merely that of benzoic acid
C 14 H 5 3 ,HO in which 1 equivalent of hydrogen has been replaced
by the compound (N0 4 ) ; and many cases will subsequently be met
with in which the same substitution may be admitted.

If a current of chlorohydric acid gas be passed through an alco-
holic solution of nitrobenzoic acid, nitrobenzoic ether C 4 H 5 O,C 14 H 4 -
(N0 4 )0 3 is formed, which separates in colourless crystals, fusible at
116.6, and boiling at about 570.

Binitrobenzoic Acid C 14 H 3 (N0 4 ) 2 3 ,HO.

1532. By digesting at a gentle heat 1 part of benzoic acid with
12 or 15 parts of a mixture, in equal proportions, of Nordhausen
sulphuric acid and fuming nitric acid, we effect the substitution, in
the molecule of benzoic acid C 14 H_0 3 ,HO, of 2 equivalents of the
compound N0 4 for 2 equivalents of hydrogen, and obtain binitro-
benzoic acid C 14 H 3 (N0 4 ) 2 3 ,HO.

Bromobenzoic Acid C 14 H 5 Br0 4 ,HO.

1533. By introducing into a very dry bottle benzoate of silver,
and bromine contained in an open tube, and leaving it to itself
after having closed the bottle, the benzoate of silver absorbs the
vapours of bromine, bromide of silver being formed, while the ben-
zoic acid combines, at the same time, with the equivalent of oxygen
given off by the silver and with 1 equivalent of bromine. By
treating it with ether, only the new acid C 14 H 5 Br0 4 ,HO, dissolves,
which remains in the form of a crystalline mass. It is important
to remark that bromobenzoic acid has not preserved the constitution
of benzoic acid, but that it is formed by the addition, and not the
substitution, of new elements.

Benzoate of Oil of Bitter Almonds.

1534. When moist chlorine is passed through oil of bitter
almonds, crystals insoluble in water, but very soluble in alcohol, are,
after some time, developed in it. The composition of this substance
may be represented by the formula (2C 14 H 6 3 ,C 14 H 5 3 ); 3 mole-
cules of the oil being grouped into one, after one of these molecules



648 ESSENTIAL OILS.

has been converted into benzole acid, by the oxidizing action of the
moist chlorine. Its composition would therefore be analogous to
that of acetal ( 1368) and of methylal, ( 1432.)

Benzoin C 14 H 6 3 .

1535. If crude oil of bitter almonds be shaken with an alco-
holic solution of potassa, the oil sets, in a few minutes, into a crys-
talline mass ; the presence of a certain quantity of cyanohydric
acid being necessary to the transformation. The new substance is
crystallized by purifying it in alcohol. This substance, to which
the name of benzoin has been given, presents exactly the same
composition as the oil of bitter almonds, melts at 248, and may
be distilled without change. Though insoluble in cold, it is slightly
soluble in boiling water, and rather freely so in alcohol. Melted
with hydrate of potassa, it yields benzoate of potassa. If it be
left, for a long time, with an aqueous solution of ammonia, a white
powder is formed, nearly insoluble in water, alcohol, and ether, which
has been called benzoinamide, and presents the formula C 43 H 18 N 3 : it
may be supposed to be formed by means of 3 equivalents of ben-
zoin 3(C 14 H 6 2 ) and 2 of ammonia, from the equation

3C 14 H 6 2 +2NH 3 =C 42 H 18 N 2 +6HO.

1536. Benzoin dissolves when heated with nitric acid, and a
new substance of the formula C 14 H 5 O a , separates after cooling,
called benzi^ which therefore results by the simple abstraction of

1 equivalent of hydrogen from the benzoin. The same compound
is obtained when chlorine is caused to act upon benzoin heated to
fusion, when the equivalent of hydrogen is disengaged in the state
of chlorohydric acid. Benzil is crystallized by purifying it in al-
cohol, and is a slightly yellowish substance, melting at about 194.

Benzil is not changed, even at the boiling point, by an aqueous
solution of potassa, while in contact with an alcoholic solution of
the same alkali, it abstracts 1 equivalent of water, and is converted
into an acid, called benzilic, of the formula C^H^Og, which results
from the combination of the elements of 2 equivalents of water with



Online LibraryV. (Victor) RegnaultElements of chemistry : for the use of colleges, academies, and schools (Volume 2) → online text (page 69 of 87)