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just as it does upon phenol :

/OH /O.POCL

C 6 H 4 <; + POC1 3 = C 6 H 4 < 4 HC1.

\COC1 \COC1

The pure chloride distils at 285 295 under the ordinary
pressure. If it be submitted to slow distillation, a mixture of
phosphorus oxychloride, orthochlorobenzoyl chloride and ortho-
chlorotribenzenyl chloride is obtained, boiling at 270 290. If
the distillation be now continued under diminished pressure,
Couper's salicyl monochlorophosphate, or orthochlorocarbonyl-
phcnyl metaphosphate passes over; it is formed, together with
orthochlorobenzoyl chloride, according to the following equation :

/O.POC1 2 ,C1 /OP0

2C 6 H 4 / = C 6 H 4 < + C 6 H 4 < "+POCL,

\coca \coci \coci

It boils at 187 under a pressure of 11 mm., and solidifies on
cooling to crystals, which melt at 30.

The chloride is decomposed by a small quantity of water into
hydrochloric acid, phosphoric acid and salicylic acid ; in moist
air, on the other hand, or on distillation with anhydrous oxalic
acid, it is converted into orthochlorocarbonylphenyl meta-
phosphate :

/OPOCL /OPO 2

CA< +C 2 H 2 4 = C 6 H 4 < +2HC1+CO + C0 2 .

\COC1 N30C1

It dissolves, however, in a large quantity of cold water, with
formation of orthocarboxylphenylphosphoric acid, C 6 H 4 (CO.OH)
OPO(OH) 2 , which on evaporation in a vacuum over soda lime
gives a crystalline mass, which melts at 147 and is readily
soluble in water.

If the chloride be heated to 165 170 with phosphorus
pentachloride, lenzenyltrichlorophosphoryl chloride, C 6 H 4 (OPOCL)



312 AROMATIC COMPOUNDS.

CC1 3 , is formed ; it is a powerfully refractive liquid, which boils
at 178 179 under a pressure of 11 12 mm., and is not con-
verted by water into hydroxybenzenyl trichloride, as might have
been expected, but into phosphosalicylic acid.

When it is heated with phosphorus chloride to 180, ortho-
chlorobenzenl trichloride is formed : l



PC1 5 = C 6 H + 2POCL



/OPOCL, Cl

6 H 4 <

\CCL

2176 Salicylamide, C 6 H 4 (OH)CO.NH 2 , is obtained by the
action of concentrated ammonia on methyl salicylate ; 2 it cry-
stallizes from ether in lustrous, yellow plates, melting at 142 , 3
and sublimes when carefully heated. As a phenol it forms
metallic salts ; its ethers are formed when ammonia is allowed to
act upon the ethers of salicylic acid.

Benzoylsalicylamide, C 6 H 5 (O.CO.C 6 H 5 )NH 2 , is formed when
salicylamide is heated to 180 with benzoyl chloride, or fused
with benzamide. 4 It is slightly soluble in alcohol, but almost
insoluble in ether, and crystallizes in needles melting at 200.

Disalicylamide, (C 6 H 4 (OH)CO) 2 NH, is prepared by heating
salicylic acid in a current of hydrochloric acid. It crystallizes
in yellowish white needles, which resemble asbestos in appearance,
and melt at 197 199 with partial decomposition ; it is in-
soluble in water, but readily dissolves in alcohol and alkalis. The
alcoholic solution is coloured red by ferric chloride. 5

Scdicylanilide, C 6 H 4 (OH)CO.NH(C 6 H 5 ), is obtained by gently
warming aniline with salicylic acid and then gradually adding
phosphorus trichloride to the cooled mass. It crystallizes from
dilute alcohol in small prisms, melting at 134 135; ferric
chloride colours the solution violet. 6

Salicyluric acid, C 6 H 4 (OH)CO.NH.CH 2 .CO 2 H. When salicylic
acid is administered internally, it appears in the urine partly in
an unaltered state and partly as salicyluric acid. This is slightly
soluble in water, readily in alcohol, and crystallizes in fine
needles, which melt at 160 and give a violet colouration with
ferric chloride. On heating with concentrated hydrochloric acid,

Anschutz, Ann. Chem. Pharm. ccxxviii. 308, and private communication.

Limpricht, ibid, xcviii. 258.

Grimaux, Bull. Soc. Chim. xiii. 25.

Chiozzaand Gerhardt, Jahresb. Chem. 1856, 502.

Schulerud, Journ. Prakt. Chem. [2] xxii. 298.

Kupferberg, ibid. [2] xvi. 442 ; Waustrat, Bcr. Deutsch. Chem. Gcs. vi. 336.



CHLOROSALICYLIC ACID. 313

it decomposes into salicylic acid and amido-acetic acid. Its
barium salt forms prisms, which are . only slightly soluble in
water. 1

Salicylnitril, C 6 H 4 (OH)CN, is formed by heating the amide
with phosphorus pentoxide, and is a colourless, crystalline
substance, which melts at 195, and on boiling with dilute
caustic potash is converted into salicylic acid. 2

Poly salicylnitril, (C 7 H 5 ON) X . Limpricht obtained this com-
pound by heating salicylamide to 270, and looked upon it as an
imide of the dibasic salicylic acid. 3 It is a yellow, crystalline
powder, which melts at 280 285 (Grimaux), and is only
converted into salicylic acid by fusion with caustic potash. On
heating with phosphorus pentachloride, orthochlorobenzonitril
is formed. 4

Benzoylsalicylnitril, C 6 H 4 (OCO.C 6 H5)CN, was prepared by
Limpricht by heating benzosalicylamide, and called by him
benzoylsalicylimide. 5 Henry obtained it by heating the poly-
nitril with benzoyl chloride. It crystallizes from hot alcohol in
small, brittle, lustrous plates, melting at 148 149. The hot
alcoholic solution is coloured red by ferric chloride.



SUBSTITUTION PRODUCTS OF SALICYLIC
ACID.

2177 Chlorosalicylic acid, C 6 H 3 C1(OH)CO 2 H (5 : 2 : 1), is formed
by passing chlorine into a solution of salicylic acid in carbon
disulphide, 6 as well as by the action of nitrous acid upon

; /3-chloramidobenzoic acid. 7 It may also be obtained by replacing
the amido-group of the corresponding amid osalicy lie acid by
chlorine, 8 and by heating parachlorophenol with tetrachloro-

i methane and alcoholic potash. 9 It dissolves in 1100 parts of
water at 20, and in 80 parts at 100, and crystallizes in small

Bertagnini, Ann. Chem. Pharm. xcvii. 249.
Grimaux, Bull. Soc. Chim. xiii. 26.
Ann. Chem. Pharm. xcviii. 261.
Henry, Bcr.Deutsch. Chem. '-es. ii. 491.
Ann. Chem. Pharm. xcix. 250.

Hiibner and Brenkeu, Ber. Dcutsch. Chem. Gcs. vi. 174.
Hiibner and Weiss, ibid. vi. 175.
Schmitt, Jahrcsb. Chem. 1864, 385 ; Beilstein, Ber. Doutsch. Chem. Gcs.
viii. 816.
9 Hasse, ibid. x. 2190.



314 AROMATIC COMPOUNDS.

needles, melting at 172. The aqueous solution is coloured violet
by ferric chloride.

DicUorosalicylic acid, C 6 H 2 C1 2 (OH)C0 2 H(3 : 5 : 2 : 1), may be
prepared by heating salicylic acid with antimony pentachloride, 1
as well as by the action of chlorine on a solution of salicylic
acid in glacial acetic acid. 2 It is also slightly soluble in boiling
water, and crystallizes from dilute alcohol in small prisms, which
melt at 214, and are coloured dark violet by ferric chloride. Con-
centrated nitric acid converts it into the same dichloronitrophenol
as is formed by the nitration of a-dichlorophenol. 3

a-Bromosalicylic acid, C 6 H 3 Br(OH)CO 2 H(3 : 2 . 1), has been
obtained from the corresponding amidobromobenzoic acid.* It
crystallizes in small, soluble needles, melting at 219 220, and
gives a dark reddish blue colouration with ferric chloride.

(3-Bromosalicylic acid (5:2:1) is formed by the direct
bromination of salicylic acid, 5 and also by treating /3-bromamido-
benzoic acid with nitrous acid (Hiibner and Heinzerling). It
crystallizes from hot water in long needles, melting at 164
165 ; ferric chloride colours it violeti

Three dibromosalicylic acids are also known. 6

lodosalicylic acid, C 6 H 3 I(OH)CO 2 H(5 :2 : 1), has been prepared
from the corresponding amido-salicylic acid by means of the
diazo-reaction. 7 It is almost insoluble in cold water, and crystal-
lizes from alcohol in needles, which melt at 196, and decompose
into iodophenol and carbon dioxide when they are rapidly heated.
The same acid had previously been obtained by Lautemann by
treating salicylic acid with iodine and caustic potash solution, 8
while Liechti 9 and Demole, 10 by the action of iodine and iodic
acid on salicylic acid, prepared an iodosalicylic acid which is
slightly soluble in cold, somewhat more readily in hot water, and
crystallizes in needles, melting at 183.

Two isomeric acids are therefore produced by the direct action
of iodine on salicylic acid, 11 and probably in varying proportions.
The following compounds are also formed in this reaction :

Lbssner, Journ. Prnkt. Chcm. [2] xiii. 429.
Smith, Bcr. Deutsch. Chcm. Ges. xi. 1225.
Smith and Knerr, Amer Chcm. Journ. viii. 95.
Hiibuer and Heinzerling, Zcituchr. Chcm. 1871, 709.
Henry, Ber. Deutsch. Chcm. Ges. ii. 275 ; Hiibner and Heinzerling.
Rollwage, ibid. x. 1707; Smith, ibid. 1706 : Hiibner, ibid. 1706.'
Goldberg, Journ. Prakt. Chcm. [2] xix. 368 ; Hiibner, Bcr. Deutsch. Clu-tn.
Gcs. xii. 1347. 8 Ann. Chcm. Pharm. cxx. 302.

Ibid. Suppl. vii. 136. 10 Bcr. Deutsch. Chcm. Gcs. vii. 1437.

11 Fischer, Ann. CJiem. Phnrm. clxxx. 346.



NITROSALICYLIC ACIDS. 315

Di-iodosalicylic acid, C 6 H 2 I 2 (OH)CO 2 H, is best obtained by
the action of iodine and mercuric cxide upon an alcoholic
solution of salicylic acid. 1 It is slightly soluble in cold, more
readily in hot water and alcohol, crystallizes in needles, melting
at 220 230, and, like moniodosalicylic acid, is coloured violet
by ferric chloride.

Tri-iodosalicylic acid, C 6 HI 3 (OH)CO 2 H, is insoluble in water,
and crystallizes from alcohol in yellow needles.

2178 Nitrosalicylic acids. In the year 1806, Fourcroy and
Vauquelin obtained a volatile, crystalline acid, which they
thought was benzoic acid, by treating indigo blue with dilute
nitric acid. Chevreul recognized the individuality of this sub-
stance, which was called indigotic acid, and it was then carefully
examined by Buff, 2 and correctly analysed by Dumas. 3 Marchand 4
confirmed the results obtained by Dumas, and found, as also
did Gerhardt, 5 that indigotic acid is identical with nitrosalicylic
acid. Piria, by the action of nitric acid on salicin, obtained
helicin and anilotic acid, which, according to Major, is identical
with nitrosalicylic acid, although Piria himself was convinced
that the two acids were different substances. 6 In spite of this,
it was generally assumed that only one nitrosalicylic acid existed,
until Hiibner found that two are formed by the nitration of
salicylic acid. 7 One of these is identical with anilotic acid, while
indigotic acid proves to be a mixture of both. 8 These acids are
also formed when the vapour of nitric acid is passed into methyl
salicylate. 9

a- Nitrosalicylic acid, (CO 2 H : OH : NO 2 = 1:2:5), may be
obtained, in addition to the methods given above, by heating
paranitrophenol with tetrachloromethane and alcoholic potash
to 100 , 10 by boiling e-nitro-amidobenzoic acid with caustic potash
solution, 11 and by passing nitrogen tetroxide into a cold aqueous
solution of salicylic acid (Hiibner). In order to prepare it, 100
parts of salicylic acid are dissolved in 800 parts of glacial acetic
acid, 50 parts of pure nitric acid, of sp. gr. of 1'5, being then






1 Weselsky, Ann. Chcm Pharm. clxxiv. 103.
- Schweigg, Journ. Chcm. Phys. li. 38 ; liv. 163.

Ann. Chim. Phys. [3] ii. 224.

Journ. Prakt. Chcm. xxvi. 385.

Ann. Chcm. Pharm. xlv. 19.

Ibid, xcvii. 253.

Ibid. cxcv. 1.

Masino and Schiff, ibid, cxcviii. 256.

Smith and Knerr ; Amcr. Chcm. Journ. viii. 99.
1 Hasse, Bcr. Dcutsch. Chcm. Gcs. x. 2188.
1 Gricsss, ibid. xi. 1730.



316 AROMATIC COMPOUNDS.

gradually added in the cold ; the solution is then diluted with
two or three volumes of water, and the acid, which separates
out after some time, purified by repeated crystallization from hot
water. The barium salt of the /3-acid may be prepared from
the mother-liquor ; it is only slightly soluble in water.

a-Nitrosalicylic acid crystallizes in long needles, which melt
at 228 and dissolve in 1475 parts of water at 15; it is more
easily soluble in alcohol or hot water. Its solution is coloured
blood-red by ferric chloride. Boiling nitric acid converts it into
picric acid, and when its diethyl ether is heated to 130 with
alcoholic ammonia, the amide of e-amidonitrobenzoic acid is
obtained. On heating with lime it decomposes into carbon
dioxide and paranitrophenol.

Normal barium a-nitrosalicylate, (C 7 H 4 NO 5 ) 2 Ba 4- 4H 2 O/ is
obtained by heating the acid with water and barium carbonate ;
it is readily soluble in water, and crystallizes in compact, yel-
low needles which form fascicular aggregates. The basic salt,
C 7 H 3 NO 5 Ba + 2H 2 O, is formed by boiling the acid with baryta
water, and crystallizes in citron-yellow plates, which have a satin
lustre and are only slightly soluble in water.

/3-Nitrosalicyfa acid, or Anilotic acid, (CO 2 H : OH : N0 2 =
1 : 2 : 3), is formed in largest quantity by the action of the most
concentrated nitric acid upon salicylic acid at a low temperature, 2
and has also been obtained by heating orthonitrophenol with
tetrachloromethane and alcoholic potash (Hasse). In order to
prepare it, 10 grms. of salicylic acid are gradually brought into
a mixture of 10 grms. of concentrated nitric acid with 10 12
grms. of glacial acetic acid at a temperature of about 6. The
solution is then poured into 250 cc. of water and the pre-
cipitated acids separated by means of their barium salts.

/8-Nitrosalicylic acid dissolves in 770 parts of water at 15 '5,
readily in alcohol and ether, and crystallizes in long needles,
which contain a molecule of water, and melt at 125. The
anhydrous acid melts at 144 ; its solution is coloured blood-red
by ferric chloride ; on heating with lime it decomposes into
carbon dioxide and orthonitrophenol, while the amide of -amido-
nitrobenzoic acid is formed by the action of alcoholic ammonia
on its diethyl ether.

Normal barium f3-nitrosalicylate, (C 7 H 4 NO 5 ) 2 Ba > crystallizes
in golden yellow plates or compact, refractive needles, which are

1 Ann. Chem. Pharm. ccx. 344.

3 Scliaumann, Bcr. Dcutsch. Chem. Gcs. xii. 1346.



DINITEOSALICYLIC ACID. 317

ouly very slightly soluble in cold, more readily iii hot water.
Ammonia added to the solution produces a deep-red colouration
and then a precipitate of the basic salt, 2C 7 H 3 NO 5 Ba 4- 3H 2 O, in
thick, blood-red needles.

Dinitrosalicylic acid, C 6 H. 2 (N0 2 ). 2 (OH)C0 2 H. The methyl
ether of this compound was obtained by Cahours by dropping
winter-green oil into a mixture of fuming nitric and sulphuric
acids. 1 It crystallizes in yellow scales, which melt at 127 128
(Salkowski), and are easily saponified by caustic potash. Sten-
house then prepared dinitrosalicylic acid by the action of nitric
acid on the aqueous extracts of Populus nigra and P. lalsam-
ifera, which contain populin. 2 It is also formed by the
further nitration of both the mononitrosalicylic acids, their
constitution being thus shown. It is best prepared by bringing
10 grms. of salicylic acid into 70 grms. of the most concentrated
nitric acid at 0, and pouring the clear solution into 300 ccm. of
water ; after standing for 24 36 hours the separated acid is
filtered off, pressed, converted into the barium salt by boiling
with water and barium carbonate, and re-precipitated by hydro-
chloric acid. 3

Dinitrosalicylic acid is readily soluble in cold, very readily in
hot water, and crystallizes therefrom in thick, lustrous plates, or,
on rapid cooling, in fine needles containing one molecule of
water. Its solution is coloured dark-red by ferric chloride ; on
heating with water to 200 it decomposes into carbon dioxide
and ordinary dinitrophenol.

Potassium dinitrosalicylate. When caustic potash is added in
excess to the aqueous solution of the acid, the salt C 6 H 2 (NO 2 ) 2
(OK)CO 2 K + H 2 O is formed; it crystallizes in long, dark-red
needles, which detonate violently when heated. Dilute hydro-
chloric acid or nitric acid added to its solution precipitates the
salt C 6 H 2 (NO 2 ) 2 (OH)CO 2 K, which crystallizes from boiling
water in compact, short, dark yellow needles.

Barium dinitrosalicylate, C 6 H 2 (NO 2 ) 2 OBaCO 2 + 3H 2 O, forms
compact, yellow needles, which are only slightly soluble in cold
water.

2179 a-Amidosalicylic acid, C 6 H 3 (NH 2 )(OH)CO 2 H, was ob-
tained by Beilstein by reducing nitrosalicylic acid with tin and
hydrochloric acid ; 4 it is better, however, to employ acetic acid
(Hiibner). It crystallizes in needles which have a satin lustre,

1 Ann. Chcm. Pharm. Ixix. 232. 3 Ibid. Ixxviii. 1.

3 Hiibner, ibid. cxcv. 45. 4 Ann. Chcm. Pharm. cxxx. 243.



318 AROMATIC COMPOUNDS.

and are insoluble in alcohol and cold water, but slightly soluble
in hot water; the solution soon decomposes in the air, a brown,
amorphous substance being precipitated. Ferric chloride pro-
duces a cherry-red colouration, followed by a brownish black
precipitate.

Amidosalicylic acid forms salts both with bases and acids ; it
decomposes on heating into carbon dioxide and paramidophenol. 1

/CO

Trimcthyldmidosalicylic acid, C 6 H 3 (OH)<( ^>O. This com-

\N(CH 3 ) 3

pound, which may also be called hydroxybenzobetaine, is formed
by the action of methyl iodide and caustic potash on amidosalicylic
acid, and crystallizes from water in large, snow-white needles,
often an inch in length, which contain four molecules of water,
have a very bitter taste and are coloured reddish violet by ferric
chloride. It combines with the mineral acids to form salts
which crystallize well.

Methyl dimethylamidosalicylatc, C 6 H 3 (OH)N(CH 3 ) 2 CO 2 CH 3 , is
prepared by heating the preceding compound, after previously
removing its water of crystallization. It forms rhombic prisms,
and is decomposed on boiling with hydrochloric acid into methyl
alcohol and dimethylamidosalicylic acid, which crystallizes in
small, almost insoluble needles. 2

(3- Amidosalicylic acid is not known in the free state ; its
hydrochloride crystallizes in needles which readily decompose
(Hiibner).

Nitro-amidosalicylic acid, C 6 H 2 (N0 2 )NH 2 (OH)CO 2 H, is formed
by the partial reduction of dinitrosalicylic acid ; it forms crystals,
melting at 220 ; a-nitrosalicylic is obtained 3 when the amido-
group is replaced by hydrogen.

Diamidosalicylic acid, C 6 H 2 (NH 2 )(OH)CO 2 H, was prepared by
Saytzew by the action of hydriodic acid on the methyl ether
of dinitrosalicylic acid. 4 It is very slightly soluble in cold,
more readily in hot water, and crystallizes in small needles. It
combines with acids to form salts which crystallize well ; ferric
chloride produces a brownish red colouration, followed by a black
precipitate.

Sulphosalicylic acid, C 6 H 3 (SO 3 H)(OH)C0 2 H, was obtained by
Mendius by the action of sulphur trioxide on salicylic acid, 5 and

1 Schmitt, Jahresber. 1864, 423.

2 Griess, Ber. Deutsch. Chem. Ges. xii. 2307. 3 Babcock, ibid. xii. 1345.
4 Ann. Chem. Pharm. cxxxiii. 321. B Ibid. ciii.



DIAZOSALICYLIC ACID. 319

may also be prepared by heating salicylic acid with sulphuric
acid. 1 It crystallizes in long, thin, very soluble needles, which
melt at 120, and are coloured an intense reddish violet by ferric
chloride. Its salts crystallize well ; on fusion with caustic potash,
no dihydroxybenzene is formed, the product consisting entirely
of phenol and salicylic acid.

Salicylsulphuric acid, CeH 4 (SO 4 H)C0 2 H. The potassium salt
may be obtained by heating salicylic acid with caustic potash
and potassium disulphate ; it crystallizes in colourless, pointed
prisms and is readily soluble in water, but insoluble in absolute
alcohol. It gives no colouration with ferric chloride and is
decomposed by dilute acids, including even acetic acid, into
potassium sulphate and salicylic acid. 2

,~N^

Diazosalicylic acid, C 6 H 3 (OH)\ | , is formed by passing

N3O.O

nitrogen trioxide into an alcoholic solution of the hydrochloride
of amidosalicylic acid. It crystallizes in fine needles and combines
with acids to form salts which crystallize well ; 3 iodosalicylic
acid is formed on heating with hydriodic acid.

Azobvnzenesalicylic acid, C 6 H 5 .N 2 .C 6 H 3 (OH)C0 2 H, is obtained
by the action of diazobenzene nitrate on an alkaline solution of
salicylic acid ; it crystallizes in orange-red needles, which are
insoluble in water, but dissolve readily in alcohol. Sulphuric
acid converts it into a sulphonic acid, which is probably identical
with the following compound. 4

Sa ! icylparazobenzenesulphonic acid, C 6 H 4 (SO 3 H)N 2 .C C H 3 (OH)
C0 2 H, is formed by bringing salicylic acid into a solution of
paradiazobenzenesulphonic acid in caustic potash. It crystallizes
in golden-yellow needles, which are only slightly soluble in
hot water; barium chloride produces a yellow precipitate of
(C 13 H 9 N 2 SO 6 ) 2 Ba, which is converted on boiling into irregular,
six-sided, lustrous plates. 5

1 Remsen, Ann. Chem. Pharm. clxxix. 107.

2 Baumann, Ber. Deutsch. Chem. Ges. xi. 1914.

3 Schmitt, Jahresber. Chem. 1864, 384 ; Schmidt and Mittenzwcy, Journ.
Prakt. Chem. [2] xviii. 193 ; Goldberg, ibid. xix. 362.

4 Stebbins, Ber. Deutsch. Chem. Ges. xiii. 716.
6 Griess, ibid. xi. 2196.






320 AROMATIC COMPOUNDS.



METAHYDROXYBENZOIC ACID.

2180 Gerland obtained this isomeride of salicylic acid by the
action of nitrous acid on a hot solution of ordinary amidobenzoic
acid, and gave it the name of oxybenzoic acid, 1 by which it is
still generally designated. It is also formed by fusing sulpho-
benzoic acid, 2 metachlorobenzoic acid, 3 or metachlorocresol 4 with
caustic potash.

In order to prepare it, 2 parts of potassium sulphobenzoate
are fused with 5 parts of caustic potash and a little water, the
melt acidified with sulphuric acid and the whole extracted with
ether.

The metahydroxybenzoic acid is left on evaporation in thick,
white crusts which are purified by re-crystallization from hot
water. Any adhering benzoic acid is finally removed by
washing with carbon disulphide (Earth).

Metahydroxybenzoic acid crystallizes in small prisms or
needles, melting at 200, which usually form warty aggregates.
It dissolves at in 265, and at 18 in 108'2 parts of water, has
a sweet taste, is not coloured by ferric chloride and can be
distilled without undergoing decomposition. It differs from its
isomerides in being reduced by sodium amalgam in an acid
solution to metahydroxybenzyl alcohol, and in blackening at 300
without a trace of phenol being formed ; decomposition, accom-
panied by the formation of small quantities of the latter, only
occurs at higher temperatures. 5

The Metahydroxylenzoates. The salts of the alkali metals are
readily soluble and do not crystallize well ; they are very stable
and only decompose at a high temperature, very little phenol
and no isomeric acid being formed. The basic salts do not
combine with carbon dioxide at a high temperature (Kupferberg) ;
when the acid is fused with an excess of sodium carbonate,
decomposition sets in above 300, the greater portion of the
acid being completely burnt, and only a small quantity of phenol
being therefore formed. 6 If two molecules of the acid are heated

Ann. Clwm. Pharm. Ixxxvi. 143 ; xci. 189 ; Fischer, ibid, cxxvii. 138.

Barth, ibid, cxlviii. 30. 3 Dembey, ibid, cxlviii. 222.

Earth, ibid. cliv. 361.

Klepl, Jaurn. Prakt. Chem. [2] xxv. 464 ; xxvii. 159.

Barth and Schroder, Ber. Dcutsch. Chem. Gcs. xii. 1254.



THE METAHYDROXYBEXZOATES. 321

to 350 Avith three molecules of caustic baryta, no change takes
place, but if seven molecules of the latter be employed, a
complete decomposition into carbon dioxide and phenol occurs
(Klepl).

Ammonium metahydroxybenzoate, C 6 H 4 (OH)CO<,NH 4 , crystal-
lizes in needles which form fascicular aggregates.

Calcium mctahydroxybenzoate, (C^H^OH.CO^gCa + 3H 2 O,
forms readily soluble crystals.

Barium metahydroxybenzoate, (C 6 H 4 .OH.C0 2 ) Ba, is an amor-
phous, gummy mass ; it has been found impossible to prepare a
basic salt.

Copper metahydroxybenzoate, (C 6 H 4 .OH.C(X) 2 Cu+H 2 O, crystal-
lizes from hot water in greenish needles.

Thallium metahydroxybenzoate, C 6 H 4 (OH)CO 2 T1, is prepared by
neutralizing a hot solution of the acid with thallium carbonate ;
it crystallizes on cooling in lustrous, colourless prisms. When a
solution of the hydroxide is neutralized with the acid and an
equal quantity of the hydroxide added to the neutral solution,
the basic salt, C 6 H 4 (OT1)CO 2 T1, crystallizes on evaporation in
yellowish prisms ; it is more readily soluble than the normal
salt and has an alkaline reaction (Kupferberg).

The methylamine salt decomposes into its constituents when
heated, and the aniline salt behaves in a similar manner, a little
hydroxybenzanilide being also formed, while tetra-ethylammonium
metahydroxybenzoate splits up into tri-ethylamine and ethyl
metahydroxybenzoate.

Ethyl metahydroxybenzoate, C C H 4 (OH)CO.,.C 2 H 5 , is formed by



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