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decomposition when more strongly heated. The hydrochloride,
(C 6 H 4 (NH 3 C1)CH 2 ) 2 NH 2 C1, is readily soluble in water, slightly
in hydrochloric acid, and crystallizes in small white, lustrous
plates ; the platinichloride, C u H 18 N 3 Cl.PtCl 6 , forms large pointed
reddish-yellow needles which are readily soluble in water.

Parcdriamidubenzylamine, (C C H 4 (NH 2 )CH 2 ) 3 N, is insoluble in
water, and crystallizes from hot alcohol in octahedra, possessing
a diamond lustre and melting at 136. Its hydrochloride
crystallizes in yellow needles, and is so readily soluble in water,
alcohol, and hydrochloric acid, that it cannot be obtained
pure.

In the preparation of the base, the action of the tin and
hydrochloric acid must not be allowed to continue too long,
as under these circumstances it is split up into paradiamido-
benzylamine and paratoluidine :



/CH,C 6 H 4 .NH 2 CH 2 .C 6 H 4 .NH

[f CH;.C H .NH+2H = HN<
\CH;C 6 H 4 .NH 2 X CH 2 .C 6 H 4 .NH 2



s so / 'L o &

N^-CH 2 .C H 4 .NH 2 +2H = HN/ _ -f CH 3 .C C H 4 .NH 2 .



Faramidobenzylpkcnylamine, C 6 H 4 (NH 2 )CH 2 .N(C 6 H 5 )H, can-
not be obtained by the action of tin and hydrochloric acid on
the nitre-compound, since a more deeply seated decomposition
takes place; the reduction may, however, be effected by
employing ammonium sulphide. The base is soluble in water
and alcohol, and crystallizes in silky scales, which melt at 88
and become coloured red in the light.

Metadiamidobenzylamine forms prismatic needles, melting at
86; its hydrochloride, (C 6 H 4 (NH 3 C1)CH 2 ) 2 NH 2 C1, crystallizes
from concentrated hydrochloric acid in long, pinkish needles, and
forms a readily soluble platinichloride.

Metatriamidobcnzylaminc forms needles melting at 142; its
platinichloride is only slightly soluble.

Mctamidobenzylplicnylaminc melts at 07.



BENZYLACETAMIDE.



BENZYL-DERIVATIVES OF THE ACID-AMIDES
AND ALLIED BODIES.

2080 Benzylacdamide, C 6 H 5 .CH 2 .N(C 2 H 3 0)H, was prepared
by Strakosch by heating benzylamine with glacial acetic acid for
several hours ; l it is more readily formed by the action of
benzyl chloride on acetamide, 2 and is very soluble in alcohol and
ether, slightly in petroleum naphtha, from which it crystallizes
in small plates, which have a pleasant smell of flowers and melt
at 57. It boils at 300 and is not attacked by acids or
aqueous alkalis ; alcoholic potash, however, converts it into
acetic acid and benzylamine.

Dibenzyloxamide, (C 6 H 5 .CH 2 .NH 2 ) 2 C 2 O 2 , is obtained by boiling
benzylamine with ethyl oxalate ; it is insoluble in water, slightly
soluble in hot alcohol, from which it crystallizes in scales, which
possess a satin lustre and melt at 216.

Cyanobcnzylamine, C 18 H 10 N 4 , is obtained by passing cyanogen
into a cold solution of benzylamine :

C 6 H 5 .CH 2 .NH 2 C=N C a H 6 .CH 2 .NH.C=NH

+ 1 -I

C 6 H 5 .CH 2 .NH 2 C=N C 6 H 5 .CH 2 .NH.C=NH.

It forms lustrous crystals, which are soluble in alcohol and
melt at 140. If hydrochloric acid be added to the alcoholic
solution, the salt, C 18 H 16 N 4 (C1H) 2 , is obtained in white, silky
needles. When it is allowed to stand in contact with hydro-
chloric acid for some time, it is converted into dibenzyloxamide
(Strakosch).

Bcnzylcyanamidc, C 6 H 5 .CH 2 .NH(CN), is formed when cyan-
ogen chloride is passed into an ethereal solution of benzyl-
amine, and crystallizes in tablets melting at 33. It changes
spontaneously into lenzylcyanuramide or lenzylmelamine, (C 6 H 5 .
CH 2 .NH) 3 C 3 N 3 , which has a much higher melting-point and
crystallizes from alcohol in plates ; the change takes place more
readily at 100.

When an alcoholic solution of benzylcyanamide is boiled with
benzylamine hydrochloride, dibenzylgnanidine (C 6 H 5 .CH 2 .NH) 2
C.NH, is formed ; this compound crystallizes from alcohol in

1 Her. Dcutuch. Chcm. Gfls. v. 697.
3 Rudolph, ibid. xii. 1297.



122 AROMATIC COMPOUNDS.

plates or tablets, melting at 100. The hydrochloride, (C 7 H 7 .
NH) 2 C.NH.C1H, is slightly soluble in water, more readily in
alcohol (Strakosch).

Dibenzykyanamide, (C 6 H,.CH 2 ) 2 N.CN, was obtained by Lim-
pricht from dibenzylamine and cyanogen chloride ; it crystallizes
from alcohol in plates, melting at 53 54.

Benzyl uocyanate, or Benzyl carlimide, C 6 H 5 .CH 2 N : CO, was
prepared by Letts in the impure state and in small quantity,
by distilling benzyl chloride with silver cyanate j 1 the isocyanurate
is always formed at the same time. It is a liquid which gives
all the characteristic reactions of the isocyanates and possesses
an extremely penetrating odour, its vapour attacking the eyes
violently.

Benzyl isocyanurate, (C 6 H 5 .CH 2 ) 3 N 3 (CO) 3 , crystallizes from hot
alcohol in silky needles, melting at 157. It boils above 320, and
when fused with caustic potash yields benzylamine. Cannizzaro
seems to have obtained the same substance in small quantity
and together with other products by the action of cyanuric
chloride on benzyl alcohol. 2

Benzyl isothiocyanate, or Benzyl mustard oil, C 6 H 5 .CH 2 .N:CS.
Hofmann obtained this compound by dissolving benzylamine in
carbon disulphide, and distilling the white, crystalline compound
formed with an alcoholic solution of mercuric chloride 3

It is a liquid which boils at about 243 and possesses the smell
of water -cress (Nasturtium officinale) in such a remarkable
degree that Hofmann was induced to search for it in the oil of
this plant ; it is not, however, present, the odoriferous constituent
in water-cress being phenylpropionitril, C 6 H 5 .C 2 H 4 .CN, 4 while
benzonitril, C C H 5 CN, is that of the nasturtium (Tropaeolum
majus.) 5

Benzyl thiocyanate, C 6 H 5 .CH 2 .S.CN, is formed by heating
benzyl chloride with an alcoholic solution of potassium thio-
cyanate. It is insoluble in water, and crystallizes from alcohol in
long, transparent prisms, which have a sharp, burning taste, and
a penetrating smell resembling that of cress. According to
Henry, 6 it melts at 3G 38 and boils with partial decomposition
at 256, while Barbaglia found its melting-point to be 41 and
its boiling-point 230 235 . 7

1 Bcr. Dcutsch. Chcm. Ges. v. 90 ; see also Strakosch, ibid. v. 692 : Ladcnburg,
ibid. x. 46.

- Bcr. Dcutxch. Chcm. Gcs. iii. 517. 3 Ibid i 201

* Ibid. vii. 520. 5 ibid. vii. 518. Ibid. ii. 633.
7 Ibid. v. 688.



BENZYL UREAS. 123



Concentrated nitric acid converts it into paranitrobenzyl thio-
cyanate, C 6 H 4 (NO 2 )CH 2 S.CN, which can also be obtained by
the action of paranitrobenzyl chloride on potassium thiocyanate.
It crystallizes from alcoholic solution in small, brittle crystals.

Various halogen substitution-products of this compound are
also known. 1

Benzyl selenocyanate,C G H. 5 .CH 2 .Se.C'$, crystallizes from alcohol
in white needles or prisms, which have an extremely repulsive
smell and melt at 71 '5. 2

Benzyl carbamate, or Benzyl urethane, C 6 H 5 .CH 2 .O.CO.NH 2 ,
was obtained by Cannizzaro, together with a little benzyl
isocyanurate and dibenzyl urea, by the action of cyanogen
chloride and cyanuric chloride on benzyl alcohol. 3 It is also
formed when urea nitrate is heated to 130 140 4 with benzyl
alcohol; it crystallizes from hot water in large plates, which
melt at 8G and decompose into benzyl alcohol and cyanuric acid
at 220.

Benzyl urea, (C 6 H 5 .CH 2 )NH.CO.NH 2 ,is formed, together with
symmetric dibenzyl urea, by the action of benzyl chloride on an
alcoholic solution of potassium cyanate, 5 as well as by that of
alcoholic ammonia on benzyl isocyanate (Letts). It is also
obtained when a solution of benzylamine hydrochloride is boiled
with potassium cyanate. 6 It is tolerably soluble in hot, readily
in boiling alcohol, and crystallizes in long, white needles, melting
at 147 147-5.

Symmetric dibenzyl urea, CO(NH.CH 2 .C 6 H 5 ) 2 , is formed when
the compound just described is heated to 200 (Cannizzaro), as
well as when benzyl isocyanate is heated with water in a sealed
tube to 100, and also when benzyl alcohol is heated to 100
with urea nitrate (Letts), benzylaldehyde being simultaneously
formed (Campisi and Amato). It is insoluble in water and
crystallizes from alcohol in needles melting at 167. It does
not combine with hydrochloric acid or nitric acid, but gives a
plantinichloride.

Asymmetric dibenzyl urea, (C 6 H 5 .CH 2 ) 2 N.CO.NH 2 , has been
obtained by Paterno and Spica from dibenzylamine hydrochloride
and potassium cyanate ; it is slightly soluble in cold, readily in
hot water, and crystallizes in thick prisms, melting at 124 125.

1 Jackson, Field, Mabeiy, Lovvry, loc. cit.
- Jackson, Ann. Ghcm. Phann. clxxix. 15.

3 Ber. Dcutsch. Uhem. Ges. iii. 517 ; iv. 412.

4 Campisi and Amato, ibid. iv. 412.

5 Paterno and Spica, ibid, ix 81. c Ibid.



124 AROMATIC COMPOUNDS.

Benzyl thiocarlamide, C 6 H 5 .CH 2 .NH.CS.NH 2 ,has been prepared
in an analogous manner from berizylamine hydrochloride and
potassium thiocyanate ; it is very soluble in water and melts at
101.

Symmetric dibenzyl thiocarbamide, (C 6 H 5 .CH 2 .NH) 2 CS, is
formed when an alcoholic solution of benzylamine is heated with
carbon disulphide until the evolution of sulphuretted hydrogen
ceases. It crystallizes in large, four-sided, lustrous tablets, melt-
ing at 114 ; it is converted into dibenzyl urea when its alcoholic
solution is treated with mercuric oxide (Strakosch). -

Asymmetric dibenzyl thiocarbamide, (C 6 H 5 .CH 9 N).,CS.NH , is
prepared from dibenzylamine hydrochloride and potassium
thiocyanate ; it is slightly soluble in water, readily in alcohol,
and crystallizes in long needles melting at 156 157 (Paterno
and Spica).



PHOSPHORUS COMPOUNDS OF BENZYL.

2081 Primary and secondary benzylphosphine are formed
when benzyl chloride is heated with phosphonium iodide and zinc
oxide. The product of the reaction is distilled with water, an
oily liquid coming over, which possesses a very characteristic,
persistent odour, and is a mixture of toluene and benzylphos-
phine. The residue contains dibenzylphosphine and other
substances, which, however, remain in solution, while the
dibenzylphosphine crystallizes out on standing, ( more rapidly in
the presence of caustic potash ; it is then removed from the
liquid and recrystallized from boiling alcohol. 1

BenzylpJiosphine, C 6 H 5 .CH 2 .PH 2 , is a strongly refractive liquid,
boiling at 180 ; it is oxidized on exposure to the air with such
rapidity that its temperature rises to above 100, thick, white
needles being deposited.

Bcnzylphosphonium iodide, C H 5 .CH 2 .PH 3 I, is obtained by the
addition of fuming hydriodic acid to benzylphosphine, as a white
precipitate which crystallizes from the hot acid in long, white
needbs. When these are washed with ether and dried in a
stream of hydrogen, they are converted into large, well-formed
tablets. Water decomposes the compound into its constituents.

1 Hofmann, Ber. Dculsch. Chcm. Gcs. v. 100.



ARSENIC COMPOUNDS OF BENZYL. 125

D&enzylphosphine, (G 6 H 5 CH 2 ) 2 PH, crystallizes in needles
which form star-like aggregates, are colourless and tasteless, do
not combine with acids, and melt at 205. While dimethyl-
phosphine and ethylphosphine are spontaneously inflammable in
the air, dibenzylphosphine is not acted upon by oxygen, even
at a higher temperature.

Triphenyttenzylphosphonium chloride, P(C 6 H 5 ) 3 (CH 2 .C 6 H 5 )C1,
is readily formed by the combination of benzylchloride with
triphenylphosphine. It is readily soluble in alcohol and water,
and separates from the latter in rhombic crystals which contain
one molecule of water and are efflorescent. Other salts, which
are characterized by their power of crystallization, have been
prepared from this compound by double decomposition ; they are
decomposed by boiling caustic soda, with formation of triphenyl-
phosphine oxide and toluene : x

P(C C H 5 ) 3 (C 6 H 5 .CH 2 )C1 + NaOH = PO(C 6 H 5 ) 3 + C H 6 .CH 8 +NaCL



ARSENIC COMPOUNDS OF BENZYL.

2082 When benzyl chloride, diluted with absolute ether, is
treated with arsenic trichloride and sodium, a reaction commences"
after some time, which in the course of a few days may raise the
temperature to the boiling-point of ether, the following com-
pounds being formed :

Dibenzylarsine trichloride.

2C 7 H 7 C1+ AsCl 3 + 2Na = (C 7 H 7 ) 2 AsCl 3 + 2NaCl.

Tribenzylarsine dichloride.

3C 7 H 7 C1 + AsCl 3 + 4Na=(C 7 H 7 ) 3 AsCl 2 + 4NaCl.

If the sodium chloride be now removed, the ether distilled off
and the residue treated with ordinary ether containing water,
the chlorides are converted into dxychlorides, which separate out
as a powder, while resinous by-products containing arsenic go
into solution. The powder is washed with ether and then treated
with boiling dilute caustic soda solution ; dibenzylarsenic acid
goes into solution, while the residue consists of tribenzylarsine
oxide, which is very slightly soluble in the cold solution, and is,
therefore, removed by cooling and filtering.

1 Michaelis and V. Soden, Ann. Chcm. Pharm. ccxxix. 319.



12 Q AROMATIC COMPOUNDS.

Dibcnzylarsenic acid, (C 6 H 5 .CH 2 ) 2 AsO.OH, is precipitated from
its alkaline solution by acids ; it is only very slightly soluble in
cold, more readily in boiling water, and crystallizes from hot
dilute alcohol in fine, white plates, melting at 210'5. It dissolves
in hot dilute hydrochloric acid and the solution on cooling
deposits the compound (C 7 H 7 ) 2 As(OH) 2 Cl, in fine needles, which
melt at 128 and are reconverted into the acid by water. It
forms similar compounds with hydrobromic, hydriodic and nitric
acids. It is decomposed on heating with concentrated hydro-
chloric acid :

2(C 7 H 7 ) 2 As0 2 H + 2HC1 = 2C 7 H 7 C1 + 2C 7 H 8 + As 2 O 3 + H 2 O.

It behaves in this reaction similarly to cacodylic or di-
methylarsenic acid. Its alkaline salts are soluble in water and
alcohol; those of the calcium group separate from alcohol in
crystals ; the silver salt is a white precipitate, insoluble in water.

Tribenzylarsine oxide, (C 6 H 5 .CH 2 ) 3 AsO, crystallizes from dilute
alcohol in lustrous needles, melting at 219'5. On heating with
hydrochloric acid it is converted into the oxychloride, (C 7 H 7 ) 3
As(OH)Cl, which melts at 162 163 and is reconverted into
the oxide by alkalis.

Tribenzylarsine, (C 6 H 5 CH 2 ) 3 As. When a little acetic ether is
added to the mixture employed in the preparation of the
compounds just described, the reaction becomes so violent that
it has to be moderated by cooling :

3C 7 H 7 C1 + AsCl 3 + 6Na = (C 7 H 7 ) 8 As + GNaCl.

If the treatment described above be then proceeded with, the
oxychlorides are obtained as before, but the solution contains
tribenzylarsine and no resinous by-products ; it crystallizes from
alcohol in large colourless needles, melting at 104. On heating
with ethyl iodide, tribenzylarsonium w^w^e, (C 6 H 5 .CH 2 ) 3 C 2 H 5 AsI,
is formed, and crystallizes in small white plates, which are
slightly soluble in water, readily in alcohol. 1

Tribenzylarsine is isomeric with tritolylarsine, (C 6 H 4 .CH 3 ) 3 As,
which, like triphenylarsine, forms no compounds with the
alcoholic iodides.

1 Michaelis and Paetow, Ber. Deutsch. Chem. Gcs. xviii. 4L



SILICON TETRABENZYL. 127



SILICON COMPOUNDS OF BENZYL.

2083 Silicon tetrdbenzyl, or Silicotctrdbenzylmethane, Si(CH 2 .
C C H 5 ) 4 , is formed by the action of sodium on a mixture of
benzylchloride and silicon chloride, to which a little acetic ether
has been added, and which has been diluted with ether. It
separates fiom warm ether in crystals melting at 127'5. 1

1 Polis, Ser. Dcutsch. Chcm. Ges. xviii. 1543.



128 AROMATIC COMPOUNDS.



THE BENZOYL GROUP.

2084 It has been already mentioned in the introductory sketch
of the development of organic chemistry (Part I. p. 11), that
Wohler and Liebig showed in their classical research, Investiga-
tions on the Radical of Benzoic Acid, that oil of bitter almonds,
benzoic acid, and a number of substances prepared from these, all
contain a "compound basis " of the formula C 7 H 5 O, to which they
gave the name of benzoyl (the latter portion of the word being
derived from v\t], matter). 1 They communicated their results
to Berzelius, who makes the following remarks in his reply :

" The results which you have obtained by the investigation of
oil of bitter almonds, are certainly the most important which
have hitherto been attained in the field of vegetable chemistry,
and promise to throw an unexpected light upon that department
of science. The fact that a substance which is composed of carbon,
hydrogen and oxygen, combines with other substances, but
especially with those which form salts and bases, in precisely the
same manner as do simple substances, proves that there are
ternary compound atoms (of the first order), and the radical of
benzoic acid is the first well-established instance of a ternary
substance which possesses the properties of an element.

" The facts brought forward by you give rise to such wide
considerations that they may be looked upon as marking the
commencement of a new era in vegetable chemistry. From this
standpoint I should propose to name the first discovered radical
composed of more than two elements, proin (from the word
Trpcol, commencement of the day, in the sense, a-rro trpwl &?
eWe'po?, Acts xxviii. 23), or orthrin (from o/o^po?, dawn.)"

In view, however, of the circumstance that the long familiar
name benzoic acid would have also been altered, and that it is
customary to respect terms in general use, provided only that
1 Ann. Chcm. Pharm. iii. 249.



BENZ ALDEHYDE. 129



they do not admit of a double interpretation, it seemed to him
most suitable to accept the name benzoyl. 1

In the next year, nevertheless, he opposed the idea of the
existence of oxygenated radicals and looked upon oil of bitter
almonds as an oxide of picramyl, C 7 H 6 (in/epos, bitter, and
), almond), a name which was never generally adopted.



BENZALDEHYDE, C 6 H 5 .CHO.

2085 The poisonous qualities of bitter almonds were known
to the ancients, and they were employed in medicine in the
middle ages : Valerius Cordus, who has been already mentioned
under the history of ether, described them as constituents of
lozenges. At the commencement of this century, Bohm, an
apothecary's assistant in Berlin, discovered that the aqueous
distillate of bitter almonds contains prussic acid, 2 and this dis-
covery led to the assumption that the latter is poisonous, a
property which its discoverer, Scheele, had, somewhat strangely,
overlooked. Schaub, Schrader, Ittner and other chemists 3
confirmed the dangerous nature of this substance, and Schrader, 4
and Matres, 5 an apothecary in Montauban, observed that a liquid oil
is also obtained by the distillation of bitter almonds with water.
This oil was more closely examined by Vogel and Robiquet,
the former 6 of whom found that the most remarkable and
striking property of oil of bitter almonds is that it is converted
into a crystalline body by exposure to the air or by treat-
ment with pure oxygen or oxymuriatic acid (chlorine), while
Robiquet showed that the leaves of the cherry-laurel yield an
oil which resembles oil of bitter almonds in every respect, and
that the substance obtained from it by oxidation has acid pro-
perties. 7

Stange, an apothecary of Basel, who also obtained this solid
substance from the cherry-laurel, recognized it as benzoic acid, 8 an

1 Ann. Chcm. Pharm. iii. 282.

- K'-hcrcr's Journ. x. 126 ; Gilbert, Ann. Phys. xiii. 503.

3 Ittner, Hcitracja zur Gc'chichte dcr JJlausaure, Freiburg and Constanz, 1809 ;
rivyc-r, Dte lilausaurc, Horni, 1870, 154.

4 Schrader, Jlcrlin. Jahrb. Pharm. ii. 43.
"' Journ. Pharm. v. 289.

6 Schweigger, Journ. Chcm. Phys. xx. 59 ; xxxii. 119.

7 Ann. Chim. Phys. xv. 29 ; xxi. 250.

8 Huchner's Rcpe,rt. Pharm. xiv. 329, 361 ; xvi. 80.

VOL. III. PART IV. K



130 AROMATIC COMPOUNDS.

observation which was confirmed by Wohler and Liebig. These
chemists determined its composition, and that of the oil of
bitter almonds, and ascertained the relations of the two com-
pounds. To oil of bitter almonds they gave the name of benzoyl
hydride, which was later changed to benzoic aldehyde and
benzaldehyde.

Shortly before this, Robiquet and Boutron-Charlard had
found that when bitter almonds are freed from fatty matters
by pressure, an odourless residue is left which yields the
characteristic smell of oil of bitter almonds on the addition
of water. The oil in question, or its elements, had there-
fore been left behind in the pressed mass and had not been
removed by the process. They, therefore, concluded that oil of
bitter almonds is a compound of water with a peculiar principle,
which they endeavoured to isolate. The use of water being
impossible, they extracted the pressed almonds with boiling
alcohol, and obtained, together with resin and a liquid sugar, a
crystalline compound containing nitrogen, to which they gave
the name of amygdalin. This compound, to which the taste of
bitter almonds is due, gave no smell of bitter almonds when
treated with water, nor did either of the two other compounds,
nor the residue, nor even of a mixture of them all. The prussic
acid and oil of bitter almonds had vanished from their hands. 1
They found further, that sweet almonds contain no amygdalin
and that the latter yields benzoic acid when oxidized by nitric
acid, while Peligot observed the formation of oil of bitter almonds
as an intermediate product in this reaction.

Wohler and Liebig, who also accurately determined the
composition of amygdalin, succeeded in finding the solution of
the problem. They showed that both sweet and bitter almonds
contain a peculiar nitrogenous substance, emulsin, which con-
verts amygdalin in presence of water into benzaldehyde, prussic
acid, and grape sugar :

C 20 H 27 NO n + 2H 2 = C 7 H 6 4- CNH + 2C 6 H 12 O 6 .

The action of the ferment is destroyed by boiling water and by
heating with alcohol, so that when dried and powdered bitter.
almonds are shaken up with boiling water and distilled, none of
the liquid oil is obtained, and the same result occurs when, as in

1 Ann. Ohim. Phys. xliv. 352.



OCCURRENCE OF BENZALDEHYDE. 131



Robiquet and Boutron-Charlard's process, they are treated with
boiling alcohol. 1

Amygdalin, which is the first example of a glucoside, a large
number of which bodies is now known, occurs in many plants,
chiefly the Amygdalaeece, Drupacece and Pomacece, which all
yield benzaldehyde and prussic acid when distilled with water.
The kernel of the peach also yields an oil resembling oil of
bitter almonds in every respect, 2 while that obtained from the
leaves, flowers, seeds and bark of the cherry, contains both oil of
bitter almonds and another oil which has a penetrating, repul-
sive odour. 3 This subject will be further discussed under
Amygdalin.

According to Winkler, the fresh leaves of the cherry-laurel
(Prunus laurocerasus), the cherry (Prunus padus) and the peach,
contain a small quantity of free oil of bitter almonds varying in
amount with the water present, 4 which can be extracted by ether.

Ittner looked upon oil of bitter almonds as a compound of
hydrocyanic acid and an ethereal oil, but Vogel opposed this
view, for he had found that it could be easily freed from hydro-
cyanic acid by treatment with caustic potash or baryta water, or
by distillation with mercuric oxide. 5 Since, however, the oil
containing hydrocyanic acid is readily converted into the polymer'.c
benzoin, C 14 H 12 O 2 , by caustic potash, Wohler and Liebig proposed
to remove the acid by shaking up with milk of lime and ferrous
sulphate, calcium ferrocyanide being formed ; a loss of about 1
per cent, is experienced in the process. According to Bertagnini
it is better to shake the oil with three or four volumes of acid
sodium sulphite, remove the crystals which separate out and
wash with alcohol. 6 All the hydrocyanic acid is not removed
by this process, and the double sulphite is therefore recrystal-
lizod from hot alcohol before being distilled with caustic soda. 7
The oil containing hydrocyanic acid is not simply a mixture of
benzaldehyde and hydrocyanic acid, but contains phenylhydroxy-
acctonitril, C 6 H 5 .CH(OH)CN, which, like other cyanhydrins or
nitrils of hydroxyacids, readily decomposes into its constituents.
Winkler had noticed some time previously that crude oil of bitter
almonds is converted by hydrochloric acid into mandelic acid

1 Ann. Chcm. Pharm. xxii. 1 ; Robiquet and Boutron, ibid. xxv. 175 ; Liebig,
iln'if. xxv. 190.

- llighini, ibid. x. 359 ; Geisslcr, ibid, xxxvi. 331.



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