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Calcium benzarsenite, (C 6 H 4 (AsO 2 H 2 )CO 2 ) 2 Ca, crystallizes in
nacreous plates, which lose a molecule of water on heating.
Silver nitrate added to its solution produces a white precipitate
of silver lenzarscnite, C 6 H 4 (AsO)CO 2 Ag.

Dibenzarscnic acid, (C 6 H 4 .C0 2 H) 2 AsO.OH, is formed by the
oxidation of paraditolylarsenic acid with potassium permanganate
and forms fine, lustrous plates, which are scarcely soluble in water,
and only slightly in alcohol and hydrochloric acid. Its salts do
not crystallize well.

Dibenzarsenc iodide, (C 6 H 4 .CO 2 H) 2 AsI, is obtained by heating
the acid with hydriodic acid and amorphous phosphorus. ]t
is a crystalline mass which dissolves in alcohol and ether, and
melts above 280.

Dibenzarsenious acid, (C 6 H 4 .CO 2 H) 2 AsOH, is prepared by de-
composing the iodide with sodium carbonate ; on the addition of
hydrochloric acid, it is obtained as a crystalline precipitate,
which is slightly soluble in water, more readily in alcohol.

Calcium dibenzarsenitc, HOAs(C 6 H 4 .C0 2 ) 2 Ca + 2H 2 O, is pre-
cipitated by alcohol from its aqueous solution as a white
powder.

Tribenzarscnic acid, (HO) 2 As(C 6 H 4 .C0 2 H) 3 , is formed when
tritolylarsine is oxidized ; it is tolerably soluble in water and
separates from alcohol in crusts, from ether in granular
crystals.

Potassium tribenzarsenate, AsO(C 6 H 4 .CO 2 K) 3 , separates from
alcohol in crystalline crusts, which are readily soluble in
water.

Tribcnzarsenious acid, or Arsenctribenzoic acid, As(C 6 H 4 .CO 2 H) 3 ,
is obtained by the reduction of tribenzarsenic acid with hydriodic
acid and phosphorus ; it crystallizes from ether, in small, colourless
needles.

Sodium arsenelribenzoate,As(CoH. i .CO l2 Nsi) s + 2H 2 O, crystallizes
from hot water in short, fine needles. The silver salt is a
yellowish precipitate. 1

1 La Coste, Ann. Clwm. Pharm. ccviii. 1.



HYDROXYBENZYL GROUP. 279



HYDROXYBENZYL GROUP.

/OH
HYDROXYBENZYL ALCOHOLS, C 6 H 4 <;

\CH 2 .OH.

2161 Orthohydroxybenzyl alcohol. Piria, in 1845, found that
galicin, which is contained in willow bark, is split up by
the action of dilute acids or of emulsin (p. 130) into
grape sugar and a new compound which he therefore named
saligenin : x

C 13 H 18 7 + H 2 = C 6 H 12 + C 7 H 8 2 .

This substance, which was subsequently also called salicyl
alcohol, because it was found to stand to salicylic acid in the
same relation as benzyl alcohol to benzoic acid, was obtained by
Beilstein and Reineke by the action of sodium amalgam and
water on salicyl aldehyde, 2 and Greene found that it is also
formed when phenol is heated with methylene chloride and
caustic soda solution : 3

/OH
C 6 H,.ONa + CH 2 CL+NaOH=C 6 H 4 < +2NaCl.

\CH 2 .OH

The decomposition of salicin by dilute acids cannot be
employed for its preparation, since a portion of the alcohol is
converted into saliretin (p. 280), and the following method,
devised by Piria, is therefore made use of. Fifty parts of salicin
are brought into 200 parts of water, and 3 parts of emulsin added,
this substance being obtained by macerating pressed almonds with
3 parts of water for two hours, and precipitating the solution with
alcohol. After twelve hours the greater portion of the saligenin
has crystallized out, and the remainder is extracted from the

1 Ann. Cficm. Phwm. Ivi. 37.

- Beilstein and Reineke, ibid, cxxviii. 179.

3 Arner. Chem. Journ. ii. 19.



280 AROMATIC COMPOUNDS.



solution with ether. The crude product is then re-crystallized
from hot benzene. 1

Orthohydroxybenzyl alcohol dissolves in 15 parts of water at
22, and in almost all proportions in boiling water, readily in
alcohol and ether. It crystallizes in small rhombohedra, or tablets,
which melt at 82 and sublime at 100. It forms a bluish red
solution in sulphuric acid, and its aqueous solution is coloured
deep blue by ferric chloride.

Saliretin, C 14 H U 3 = C 6 H 4 (OH)CH 2 O.C 6 H 4 .CH 2 OH. Bracon-
not found that concentrated sulphuric acid converts salicin into
a resinous substance, and Piria, who observed that dilute acids
have the same effect, gave the product its name, which is
intended to suggest both its nature and source. 2

Saliretin is formed from salicin by elimination of the elements
of water ; in order to prepare it, salicin is heated to 80 with
10 parts of fuming hydrochloric acid, the product precipitated by
water, dissolved in dilute alcohol and again precipitated by a
solution of salt. 3

It is a yellowish powder, which dissolves in alkalis and does
not yield either salicylaldehyde or salicylic acid on oxidation.
Concentrated nitric acid converts it into picric acid.

The saliretin obtained by the action of concentrated sulphuric
acid has the formula C 28 H 26 O 5 , 4 while a compound, C 56 H 50 O 9 , is
formed by heating saligenin with acetic anhydride (Beilstein and
Seelheim).

Salireton, C 14 H 12 O 3 , is formed in small quantity, together Avith
other resinous products, when saligenin is heated with glycerol.
It crystallizes from hot water in plates or needles, which melt at
121 '5, are coloured red by strong sulphuric acid, and are not
affected by ferric chloride. 5

Orthohydroxybenzyl methyl ether, or Orthomcthoxybcnzyl alcohol,
C 6 H 4 (OCH 3 )CH 2 OH, is formed when saligenin is heated with
methyl iodide, caustic potash and wood spirit ; it is a liquid,
which boils at 247'5 and solidifies in a mixture of ether and solid
carbonic acid to a glassy mass. 6

Orthohydroxybenzyl ethyl ether, C 6 H 4 (OC 2 H 5 )CH 2 .OH, is a
pleasant smelling liquid, which boils at 265 and solidifies at

Boilstein and Seelheim, Ann. Chem. Pharm. cxvii. 84.

Ann. CJiem. Pharm. xxx. 179.

Kraut, ibid. clvi. 124.

f.erhanlt, Ann. Chim. Phys. [3"| vii. 215.

Giactwa, Jmirn. PrnU. Chem. [2] xxi. 221.

Gannizzaro and Kiirnor. 7,v,-. It.-utwh. Ch,n. <f. \. 4.,f,.



SALICIK 281



to a crystalline mass. It gives no colouration with ferric chloride,
and is oxidized by dilute nitric acid to ethoxybenzoic acid or ethyl
salicylic acid, CeH^OC^CO.OH. 1

Caffeol, C 8 H 10 O 2 . When coffee beans are roasted, the follow-
ing substances are given off from 100 parts : 0'05 of caffeol,
018 of caffeine, (V48 of fatty acids, chiefly palmitic and acetic,
carbon dioxide and small quantities of pyrrol, methylamine and
quinol, derived probably from the quinic acid which is contained
in the beans.

Caffeol is a liquid which boils at 195 197, and possesses
the fine aroma of coffee in a very marked degree. Its alcoholic
solution gives with ferric chloride a red colouration which is not
destroyed by sodium carbonate. It only dissolves with difficulty
in concentrated caustic potash solution, and on fusion with
caustic potash yields salicylic acid ; it is probably therefore a methyl
ether of saligenin, and has the constitution C 6 H 4 (OH)CH 2 .OCH 3 . 2
The fact that it gives a red colouration with ferric chloride,
which shows it to be a phenol, is in accordance with this sup-
position. Rotsch has also found that hydroxybenzyl methyl
ether, already mentioned, which is isomeric with caffeol, smells
strongly of burnt coffee, but loses the smell completely on
purification. This behaviour may be explained by the formation
of small quantities of caffeol as a by-product, to which the crude
product owes its smell.

2162 Salicin, or Ortlwhydroxylenzyl glucoside, C 6 H 4 (CH.,.OH)
OC 6 H n O 6 . After several chemists had unsuccessfully endeavoured
to obtain the bitter principle of willow-bark, which was recom-
mended in cases of intermittent fever as a substitute for quinine,
in the pure state, Leroux succeeded in purifying it to such an
extent that it could be readily crystallized. 3 It was at first
thought to be an alkaloid, although this was afterwards shown
not to be the case, and the difficulty experienced in obtaining
compounds of it with other substances prevented chemists
from examining it more closely until Piria subjected it to a
careful investigation, which resulted in a complete explanation
of its nature. 4

It occurs in the bark, leaves, and female flowers of many
trees which do not all belong to the willow tribe, and to the
extent of 4 per cent, in Salix helix, pcntandra, and prcccox', it

1 RStsch, Maruthh. Chr.m. i. 621. 2 Bcrnheimer, ibid. i. 456.

3 Ann. <"/,/,. Pln, K . xliii. 440.

1 -).H,i. Chem. Pharm. xxx. 151 ami 189 ; Ivi. 49 ; Licbi^, //>*<*. xxx. IS").



AROMATIC COMPOUNDS.



has also been found in the bark and leaves of the poplar, 1 in
the flower buds of Spiraa Ulmaria (p. 286) and in castoreum -
(Wohler).

In order to prepare it, 3 parts of willow-bark are extracted
three times with boiling water, the extract evaporated down
to 9 parts, digested for twenty-four hours with 1 part of litharge,
filtered and evaporated to a syrup. The salicin separates out
and is purified by re-crystallization. 3 It forms needles, plates, or
rhombic prisms, which dissolve in 30 parts of water at the
ordinary temperature, and freely in hot water and alcohol, but
are insoluble in ether; it has a very bitter taste, 'and forms a
purple-red solution in sulphuric acid. Dilute nitric acid oxidizes
it to helicin, C 6 H 4 (CHO)OC 6 H n O 6 (p. 288), which may be re-
converted into salicin by sodium amalgam and water. As
helicin can be artificially prepared by the action of acetochloro-
glucose on salicylaldehyde, it is also possible, as Michael has
shown, to prepare salicin artificially ; this is the first instance of
the synthesis of a glucoside occurring in nature. 4

Salicin melts at 201, and solidifies on cooling to a crystalline
mass ; when it is heated, however, for some time to 230
240, it partially decomposes into saliretin and glucosane 5
(Part II. p. 577). Its aqueous solution rotates the plane of
polarization to the left. 6 When taken internally a portion of it
appears in the urine as saligenin, salicylaldehyde and salicylic
acid, the remainder being excreted unchanged ; 7 its occurrence
in castoreum is thus explained. It is used in medicine in cases
of intermittent fever, acute rheumatism, &c., and is also employed
for adulterating quinine.

Populin, or Benzoylsalicin, C 18 H 17 (C 6 H 5 .CO)O 7 + 2H 2 O, was
discovered by Braconnot in the bark and leaves of the aspen
poplar, Populus tremnla, 8 and carefully investigated by Piria. 9
Piccard also observed it, along with salicin and other substances,
in the buds of Populus pyramidnlis, ni'/ra et balsamifera, 10 and
Schiff obtained it artificially by fusing salicin with benzoic
anhydride. 11



Pharm.



1 Braconnot, Ann. Chim. Phys. xliv. 296 ; Tischhausen, Ann. Chem.
rii. 280. = Ibid. Ixvii. 360.

Duflos, -ibid. viii. 200. * Amer. Chem. Journ. v. 171.

Schiff, Ber. Dcutsch. Chem. Gcs. xiv. 304.
Hesse, Ann. Clicm. Pharm. clxxvi. 116.

Laveran and Millon, ibid. Hi. 435 ; Ranke, Jahrcsb. Chem. 1852, 711.
Ann. Chim. Phys. xliv. 296.
Ann. Chem. Pharm. Ixxxi. 245 ; xcvi. 375.
1(1 Ber. Deutech. Chem. Gcs. vi. 890. Ann. Chem. Pharm. cliv. 5.



BENZOYLSALICIN. 283



It crystallizes in extremely thin needles, which dissolve in
2,420 parts of water at 15 and in 42 parts at 100 C ; it loses its
water of crystallization at 100 and melts at 180. Its taste
resembles that of liquorice ; it is coloured amaranthine red by
sulphuric acid. Boiling baryta water decomposes it into salicin
and benzoic acid ; emulsin has no action upon it, but on boiling
with a dilute acid it yields saliretin, benzoic acid and glucose, 1
while salicin, benzamide, and ethyl benzoate are obtained by
heating it with alcoholic ammonia. Nitric acid oxidizes it to
benzoyl-helicin, which is the corresponding aldehyde. It has,
therefore, the following constitution :

/CH,.OH

C.H/

\OC 6 H 10 (CO.C 6 H 5 )0 5

2163 Metahydroxybenzyl alcohol is obtained by the action of
sodium amalgam on an aqueous solution of metahydroxy benzoic
acid which is kept acid by the repeated addition of small
quantities of hydrochloric acid. It is readily soluble in alcohol
and hot water, crystallizes in tough needles, melts at 63, and
boils with partial decomposition at about 300 ; its aqueous
solution is coloured violet-blue by ferric chloride. Hydrochloric
acid converts it into a viscid resin, and on fusion with caustic
potash it is oxidized to metahydroxybenzoic acid.

Mctahydroxylcnzyl acetate, C 6 H 4 (OH)CH 2 .O.C.,H 3 O, is formed
by the action of a mixture of acetic and sulphuric acids
on the alcohol, and forms crystals which melt at 55 and
are only very slightly soluble in water ; the solution is
coloured violet-blue by ferric chloride. It boils with decom-
position at 295 302.

Metahydroxybenzyl diacetate, or Mela-acetdbenzyl acetate, C 6 H 4
(OC 2 H 3 O)CH 2 .OC 2 H 3 0, is formed by heating the alcohol to
160 with acetic anhydride, and is a liquid which boils at 290,
and does not give a colouration with feme chloride. 2

Parahydroxybenzyl alcohol is obtained by the action of sodium
amalgam on a solution of parabenzaldehyde in dilute alcohol
acidified with sulphuric acid. It is readily soluble in water,
alcohol and ether, and crystallizes in needles, melting at 110. It
forms a splendid reddish violet solution in concentrated sulphuric
acid. 3

1 Schmidt, Ann. Chew. Phartn. xix. 92.

- Velden, Journ. Prakt. Chcm, [2] xv. 165.

3 Biedermanu, Bcr. Deutsch. Cttem. Ges. xix. 2373.



234 AROMATIC COMPOUNDS.

Parahydroxybenzyl methyl ether, or Anise alcohol, C C H 4 (OCH 3 )
CH 9 .OH, is formed by the action of alcoholic potash on anis-
aldehyde (paramethoxybenzaldehyde). 1 It is also formed when
parahydroxybenzyl alcohol is heated with methyl iodide and
caustic potash, and crystallizes in hard, lustrous needles, which
have a faint spirituous odour and a burning taste ; it melts at
25, and boils at 258'8. 2

Paramcthoxylenzyl chloride, C 6 H 4 (OCH 3 )CH 2 C1, is prepared by
saturating the alcohol with hydrochloric acid ; it is a liquid with
a fruity odour and burning taste. On treatment with sodium
methylate it yields the dimethyl ether C 6 H 4 (OCH 3 )CH 2 .OCH 3 ,
a liquid boiling at 225'5. 3

Parahydroxybenzyl acetate, C 6 H 4 (OH)CH 2 .O.C 2 H 3 0, is formed
in a similar manner to the meta-cornpound, and crystallizes
in yellowish needles melting at 84.

Para-acetobenzyl acetate, C 6 H 4 (OC 2 H 3 O)CH 2 .OC 2 H 3 O, also
forms yellow needles, melting at 75 (Biedermann).

Paramethoxybenzylamine, C 6 H 4 (OCH 3 )CH 2 .NH 2 , is obtained by
the action of ammonia on the chloride, and crystallizes from hot
water in small needles which have a strongly alkaline reaction
and melt above 100. The secondary base, (C 8 H 9 O) 2 NH, is
formed simultaneously ; it is less soluble in water, and crystal-
lizes in plates melting at 32 33. 4

Parahydroxybenzyl thiocarUmide, C 6 H 4 (OH)CH 2 N = CS, has
been already mentioned as sinalbin mustard oil (Part II. p. 448 ).
It is a product of the decomposition of sinalbin, C 30 H 44 N 2 S 2 O 16 ,
which crystallizes in small, lustrous needles and is readily
soluble in water, slightly in alcohol ; it is converted by myrosin
in presence of water into sinalbin mustard oil, acid sinapiu
sulphate, and grape sugar:

C 30 H 44 N 2 S 2 16 - C 8 H 7 NOS + C^NO^H.SO, + C 6 H 12 O C .

Sinalbin mustard oil is a non-volatile, oily liquid, which has a
very sharp taste and blisters the skin. When the sulphur is
removed it is converted into parahydroxyphcnylacetonitril,
C 6 H 4 (OH)CH 2 .CN, which was considered to be the ortho-
compound by Laubenheimer and Will. 5

1 Bertagnini and Cannizzaro, Ann. Clw.m. Pftstrm. xcviii. 189.
- Cannizzaro and Korner, Ber. Dciittsch. Clicm. Gcs. v. 436.
' Cannizzavo, Ann. Chem. Pharm. cxxxvii. 246.

4 Ibid, cxvii. 240.

5 Ann. Chcm. Phm-m. cxcix. 150.



SALTCYLALDEHYDE. 285



/OH
HYDROXYBENZALDEHYDES, C fi H,<

XJHO,

ORTHOHYDROXYBENZALDEEYDE, OR SALTCYLALDEHYDE.

2164 The volatile oil of the flowers of Spiraea Ulmaria was
first examined by Pagenstecher, an apothecary of Berne, who
discovered in it an acid, the aqueous solution of which is coloured
violet by ferric chloride, 1 and which was called " spiroylwasser-
stoffsdure" C 12 H 6 O(C = 6,O = 8) by Lowig, to whom Pagenstecher
intrusted its further investigation. 2 He and Weidmann sub-
sequently found that when the ethereal solution is shaken with
caustic potash, this is coloured yellow, and on evaporation of the
ether an indifferent oil remains behind, which possesses the
smell of the flowers in a very marked degree, while if the
alkaline solution be distilled with phosphoric acid, an acid oil
passes over first, followed by an acid crystallizing in long needles.
They now called the former of these spirceic acid, or spiroyl
hydride, C 13 H 10 O 4 . 3 About the same time, Piria, working in
Dumas' laboratory, found that salicin on oxidation with potassium
dichromate and dilute sulphuric acid yields a volatile, oily,
aromatic liquid, which he called salicyl hydride, C 7 H 6 O 2 . This
is isomeric with benzoic acid, and is to be looked upon as a
hydracid, which, on heating with caustic potash, yields salicylic
acid, C 7 H 6 3 , just as benzoyl hydride under similar circumstances
yields benzoic acid. The radicals benzoyl, C 7 H 6 O, and salicyl,
C 7 H 5 2 , are different oxidation products of the hydrocarbon,
C 7 H 5 . 4 Dumas, to whom Pagenstecher showed his preparations
from Spiraea, noticed the great similarity of the oil to salicyl
hydride and suggested that spirseic acid is identical with the
latter ; 5 this had already been proved by Ettling, who named
the compound salicylous or spiroylous acid. 6

The compound was mistaken for an acid because it is at once
an aldehyde and a phenol, and therefore forms salts.

Salicylaldehyde also occurs in the juice of various plants

1 Buchner's Eepcrt. Plui.rm. xlix. 337 ; li. 364.
- Pogg. Ann. xxxvi. 383.

3 Ibid. xlvi. 57.

4 Ann. Chem. Pharm. xxix. 300, xxx. 151.

5 Ibid. xxix. 306.

6 Ibid. xxix. :W9 ; xxxv. 241.



28t> AROMATIC COMPOUNDS.

belonging to the genus Spiraea, 1 in the stem and root of Crcpis
fcetida? and in the larvae of Chrysomela populi, which live on
willows and poplars, and possess small openings along the body
from which salicyl aldehyde may be pressed out in oily drops. 3
Enz also obtained it by distilling the beetle \\ ith water. 4

In order to prepare it, a mixture of 3 parts of salicin and 3
parts of potassium dichromate is treated with 24 parts of water,
to which 4*5 parts of sulphuric acid diluted with 12 parts of
water are added. When the reaction is complete, the mixture
is distilled until the distillate passes over clear, and the oily
portion then separated from the water ; some of the aldehyde
remains dissolved in the water and is extracted by ether. 5

If the distillation be continued too long, furfurol passes over,
and all preparations made from the aldehyde then become
intensely red-coloured on standing. 6

The flower-buds of Spiraea Ulmaria omy give a very small
yield of salicyl aldehyde on distillation with water, but a larger
quantity is obtained when sulphuric acid and potassium di-
chromate are added, thus showing that the buds contain salicin. 7
Salicyl aldehyde is obtained synthetically, along with the isomeric
parahydroxybenzaldehyde, by the action of chloroform on a
solution of phenol in caustic soda (Part III. p. 36). They are
separated by distillation in steam, with which the latter is not
volatile. 8

Properties. Salicylaldehyde is a liquid with a pleasant aromatic
smell and a burning spice-like taste ; it boils at 196'5, solidifies
at 20 to large crystals, and has a specific gravity of I 4 1731 at
13 - 5. Its aqueous solution, even when very dilute, is coloured
violet by ferric chloride, and yellow by alkalis ; it does not
reduce Fehling's solution, 9 and forms difficultly soluble com-
pounds with the acid sulphites of the alkali metals, 10 this
property being made use of in its purification (Reimer and
Tiemann). It produces a fine reddish violet colouration in a
solution of rosaniline which has been decolourized by sulphurous
acid. 11 The aldehydes of the fatty acids, benzaldehyde, &c., also
give this reaction.

Wicke, Ann. Chem. Pharm. Ixxxiii. 175. 2 Ibid. xci. 374.

Jnhresber. Chem. 1850, 583. 4 Ibid. 1859, 312.

Schiff, Ann. Chem. Pharm. cl. 193. 6 Ibid. ccx. 115.

Buchner, ibid. Ixxxviii. 284.

Reimer and Tiemann, Ber. Deukch. Chem. Ges. ix. 824.

Tollens, ibid. xiv. 1959.

Bertagniui, Ann. Chem. Pharm. Ixxxv. 93.

Schmidt, Ber. Dcutsch. Chem. Gcs. xiv. 1848.



SALICYLALDEHYDE COMPOUNDS. 287

As a phenol it forms salts, ethers, and ethereal salts.

Potassium salicylaldehyde, C 6 H 4 (OK)CHO + H 2 O, is obtained
by adding caustic potash to a solution of the aldehyde in dilute
alcohol; it crystallizes in light yellow, nacreous, quadratic tablets,
which are readily soluble in water. The compound C 6 H 4 (OK)
CHO + C 6 H 4 (OH)CHO is obtained in fine, fascicular groups of
needles by adding the aldehyde to an alcoholic solution of the
potassium salt.

Barium salicylaldehyde, (C c H 4 (CHO)O) 2 Ba+ 2H 2 0, crystallizes
in yellow needles, which are slightly soluble in cold water.

Copper salicylaldehyde, (C 6 H 4 (CHO)O),Cu, is a very character-
istic salt ; when an aqueous solution of copper acetate is added to
a dilute alcoholic solution of the aldehyde, the liquid becomes
coloured emerald green, and after a few minutes deposits spark-
ling crystals; the liquid then presents a most beautiful appearance
when placed in the sunlight. The crystals become brownish-
green on drying, and are only slightly soluble in water and
alcohol (Ettling).

Lead salicylaldehyde, C H 4 (CHO)OPb.OH, is formed when
basic lead acetate is added to an alcoholic solution of the alde-
hyde ; it is a yellow precipitate which dissolves on heating, and
separates out on cooling in heavy, light-yellow granules.

Methyl salicylaldehyde, C 6 H 4 (OCH 3 )CHO, is obtained by
heating the sodium salt with methyl alcohol and methyl
iodide. 1 It is an oily liquid which possesses a faint odour, boils
at 238, and, when perfectly free from salicylaldehyde, solidifies
after some time to tough prisms melting at 35. It forms a
compound with acid ammonium sulphite, which crystallizes in
lustrous prisms and is readily soluble in water and alcohol. The
potassium sulphite compound also crystallizes well, but is only
slightly soluble in cold alcohol.

Ethyl salicylaldehyde, C 6 H 4 (OC 2 H 5 )CHO, was obtained by
Ferkin in a similar manner, as a strongly refractive liquid boiling
at 247 249. It is also formed when a mixture of calcium
formate and calcium ethyl salicylate is distilled, while, when
calcium salicylate is substituted for the ethyl compound, only
phenol is formed. 2

Benzyl salicylaldehyde, C 6 H 4 (OCH 2 .C 6 H 5 )CHO, crystallize?
from boiling alcohol in flat, rhombic prisms, which melt at 46,

1 Perkin, Journ. Chcm. .S'oc. xx. 418 ; Yoswiukcl, Her. Dcutsch. Chem. Ges. xv.
2024.

2 Gottig, ibid. x. 8.






288 AROMATIC COMPOUNDS.

and have a faint odour resembling that of cloves. It boils above
360, and forms an irritating vapour. 1

Acetyl salicylaldehyde, C 6 H 4 (OC. 2 H 3 0)CHO, is formed when
the sodium salt is suspended in ether and treated with acetic
anhydride. It is extremely soluble in alcohol, crystallizes in
fine, silky needles, melts at 37, and then solidifies to a mass
possessing a satin lustre. Its boiling-point lies at about 253;
it combines with the acid sulphites of the alkali metals. 2

Benzoyl salicylaldehyde, C 6 H 4 (O.CO.C 6 H 5 )CHO, was obtained
by Perkin by the action of benzoyl chloride on the sodium
compound. It is a thick oily liquid, which boils above 360,
and forms the usual compounds with the acid sulphites of the
alkali metals. 3

2165 Helicin, 4C 6 H/OC 6 H n 5 )CHO + 3H 2 O, is formed by
the action of dilute nitric acid on salicin. 4 In order to prepare
it, salicin is treated in flat basins or plates with eight times
its weight of nitric acid of sp. gr. I'lo, containing lower
oxides of nitrogen, which may be introduced by the addition of
a few drops of the red, fuming acid. The helicin is filtered off
after some hours and washed two or three times with cold
water. 5 It is readily soluble in hot water and alcohol, but not
in ether, and crystallizes in small, very fine needles, which have
a faint, bitter taste, lose their water of crystallization at 100 and
melt at 175. It is not coloured by ferric chloride; if a blood-
red colouration be produced, it contains nitrosalicylic acid. It is
resolved into dextrose and salicylaldehyde by the action of acids,
alkalis and emulsin. It can be synthetically prepared by acting
upon potassium salicylaldehyde with an alcoholic solution ot



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