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amalgam and water reduce it to meconin, while on evaporation
with caustic potash it is converted into the latter and hemipinic
acid (Matthiessen and Foster, Beckett and Wright). When its
sodium salt is heated with soda lime methylvanillin is formed,
and isovanillin when it is heated with dilute sulphuric acid to
160 170. Concentrated sulphuric acid converts it on heating
into a red colouring matter, which Anderson mistook for alizarin,
C U H 8 O 4 , but which was shown by Liebermann and Chojnacki to
be the closely allied substance rufiopin, 1 C 14 H 8 6 .

The salts of opianic acid have been investigated by Wohler
and Wegscheider. 2

Potassium opianate, C 10 H 9 O 5 K, is readily soluble in water and
crystallizes in several forms, which differ in the amount of water
they contain. It crystallizes from ordinary alcohol in compact,
white prisms containing two and a half molecules, or transparent,
rhombic tablets with one molecule of water of crystallization.

Barium opianate, (C 10 H 9 O 5 ) 2 Ba+2H 2 O, forms a radiating mass
of prisms, which are readily soluble in water and effloresce when
kept in a warm place.

Lead opianate, (C 10 H 9 O 5 ) 2 Pb + 2H 2 O, is only slightly soluble,
and forms very lustrous, transparent crystals, apparently of the
same form as sphenite.

Silver opianate, 2C 10 H 9 O 5 Ag + H 2 O, is described by Wohler as
forming short prisms, which readily become coloured yellow.
Wegscheider found that when the acid is rapidly dissolved in
presence of silver carbonate, complete saturation does not take
place, and that reduction ensues on boiling. On precipitating
the potassium salt with silver nitrate, he found that the greater
portion of the silver salt was removed by washing, and therefore
prepared it by mixing concentrated solutions of silver fluoride
and potassium opianate. The tough, amorphous, yellowish pre-
cipitate changes on stirring into hemispherical or warty masses
consisting of small prisms, which can be completely washed
with a small quantity of water.
1 Ann. Chcm. Pkarm. clxii. 321. 2 Monatsh. Chcm. iii. 348.


Methyl opianate, C 10 H 9 5 (CH 3 ), was prepared by Wegscheider
from the silver salt by the action of methyl iodide. It is also
formed, as found by Liebermann and Kleemann, when opianic
acid is boiled with methyl alcohol. 1 It crystallizes from alcohol
in Hat, monosymmetric needles, and from ether in thick, vitreous
tablets or short prisms, which melt at 102 and partially sublime
on careful heating. It rapidly decomposes into methyl alcohol
and opianic acid when boiled with water, the latter being ob-
tained pure by this method (Liebermann and Kleemann).

Ethyl opianate, C 10 H 9 O 5 (C 2 H 5 ), is readily formed, according to
Wohler, by saturating a hot, alcoholic solution of opianic acid
with sulphur dioxide, while it could not be prepared by means
of hydrochloric acid. Anderson, however, noticed its formation
when hydrochloric acid was added to an alcoholic solution of
the potassium salt, and Prinz prepared it by the action of the
chloride on absolute alcohol. According to Liebermann and
Kleemann, it may be most simply obtained by boiling the acid
with absolute alcohol.

It crystallizes from alcohol in needles or fine prisms, which
melt at 92 and sublime when carefully heated.

2264 Opianic anhydride, C 20 H 18 O 9 . Wohler found that
opianic acid undergoes a remarkable change when it is kept in
a state of fusion for some time, becoming insoluble in water,
and he assumed that it is thus converted into an isomeric modi-
fication, while Matthiessen and Wright concluded that it loses
water and forms the compound C^HggOjg. 2 Wegscheider, on the
other hand, considered the substance to be formed from three
molecules of opianic acid, and named it triopia.nide, C 30 H 18 O 14 . 3 ;
Liebermann has, however, found 4 that it is formed when opianic
acid is heated for two hours at 160 in a current of air, and
explains the reaction by the following equation :

2(CH 3 O) 2 (COH)C 6 H 2 ,CO.OH =

(CH 3 0),(COH)C 6 H 2 .CO V

)0 + H 2 0.
(CH 3 0) 2 (COH)C e H 2 .C(K

Opianic anhydride is also obtained when opianic acid is heated
with phosphorus pentachloride, and crystallizes from hot acetone
iu needles, which melt at 234.

1 Her. Dcutsch. Chan. Ocs. xx. 881. " Ann. Chon. Pharm. SnppL vii. 3.
3 Munatsh. Chan. iv. 262. * Her. Dcutsch. Chan. Gis. xix. 2288.


On heating with caustic potash and a little water, it decom-
poses into meconin . and hemipinic acid, while on boiling with
caustic potash solution, or when it is dissolved in sulphuric acid
and the solution poured into water, it is reconverted into opianic
acid, b

Acctylopianic acid. When aromatic aldehydes or aldehydo-
acids are heated with acetic anhydride and anhydrous sodium
acetate, the aldehyde group CHO is converted into the acrylic
acid residue CH=zCH CO 2 H. Opianic acid does not behave
in this way, but forms acetylopianic acid, which crystallizes from
hot water in needles melting at 120 121. It is insoluble in
cold alkalis and is only decomposed on boiling, acetic and
opianic acids being formed ; it therefore does not contain a
carboxyl group, and its constitution must be expressed by the
following formula :

(CH 3 0) 2 C 6 H 2 < >0


It appears, therefore, that opianic acid can behave not only as
an ortho-aldehydo-acid, but also as a lactone. 1 The one form
can pass into the other according to the circumstances of the


iurous acid, C 6 H 2 (OCH 3 ) 2 (CHO SO 3 H 2 )CO 2 H, is
formed when opianic acid is dissolved in a hot aqueous solution
of sulphur dioxide :


(CH 3 0) 2 C 6 .H 2 < +SO(OH) 2 =


On evaporation at a gentle heat, the compound is left as a
fine crystalline mass, which is resolved into its constituents by
water. Its solution has a characteristic bitter taste, and leaves
a persistent, sweet after-taste.

1 Liebet mainland Kleemanu, Bcr. Dcutsch. Chem. Gcs. xix. 2287.


Jiarium opianylsulpliiie , (C 10 H ]0 O 5 .SO 3 H) 2 Ba-|-3H 2 O, is pre-
pared by dissolving barium carbonate in a freshly-made solution
of the acid, and crystallizes in lustrous, rhomboheclral tablets.

Lead opianylsulphitc, (C ]0 H ]0 O 5 .SO 2 H) 2 Pb -f 6H 2 O, is prepared
in a similar manner, and forms very lustrous, four-sided prisms
or six-sided tablets (Wohler).

These salts correspond to the ethidene sulphites (Part II. p. 81).

2265 Thio-opianic acid, (CH 8 O),C 6 H S (CHS)CO 2 H, was ob-
tained by Wohler by passing sulphuretted hydrogen into a warm
solution of opianic acid ; it forms a yellow powder which crystal-
lizes from alcohol in fine, transparent, yellowish prisms, which
melt below 100 and resemble . opianic acid in forming an

Chloropianic acid, (CH 3 O) 2 CHC1(COH)CO 2 H, is formed by
the action of potassium chlorate on a hot solution of opianic acid
in hydrochloric acid, and crystallizes from hot water in small
prisms melting at 210 211 (Prinz).

Bromopianic acid, (CH 3 O) 2 C 6 HBr(COH)C0 2 H, is prepared by
adding bromine to a boiling solution of opianic acid (Prinz) and
by triturating opianic anhydride with bromine (Wegscheider).
It crystallizes from hot water in small, arborescent needles which
melt at 204.

Nitro-opianic acid, (CH 3 O) 2 C6H(NO 2 )(COH)C0 2 H, is formed,
together with nitrohemipinic acid, by the action of concentrated
nitric acid on opianic acid. It is only slightly soluble in water,
and crystallizes in lustrous yellow prisms, melting at 166. Its
salts are readily soluble in water and crystallize well.

Opianylphcnyttiydrazide, C 16 H 14 N 2 O 3 , is obtained by mixing
hot solutions of opianic acid, phenylhydrazine hydrochloride, and
sodium acetate (Part III. p. 333) :

C 10 H 10 6 + C 6 H 6 N 2 H 3 = C W H M N 1 0,+ 2H,O.

It crystallizes from alcohol in almost colourless needles, which
melt at 175, and are insoluble in alkalis, but dissolve in con-
centrated hydrochloric acid, from which solution they are pre-
cipitated by water. It is therefore a weak base, and is very
stable, being unattacked by concentrated sulphuric acid even at
130; it has probably the following constitution :

/CO N.C 6 H 6


Phenylhydrazone nitro-opianic acid, C 16 H 15 N 3 O 6 , is formed in
a similar manner, according to the equation :


(CH 3 O) 2 C 6 H (NO 2 ) < + NH 2 -NH.C C II.



(CH 3 0) 2 C 6 H(N0 2 )<( +H 2 0.

\CHn:N NHC 6 H 5

It crystallizes in splendid, carmine-red needles, which melt at
184, and form a red solution in alkalis. Acids convert it into
nitro-opianylphcnylhydrazidc, C 16 H 13 N 3 O 5 , which crystallizes in
yellow, silky needles, melting at 173, is insoluble in alkalis,
and hehaves as a weak but stable base. 1

When it is boiled with alcoholic potash, it decomposes
into methyl alcohol and nitromethylnorGpianylvhenylhydrazidc,
C 15 H n N 3 O 5 , which has also been prepared from methylnor-
opianic acid. 2 This substance crystallizes in glittering, yellow
plates, melting at 191, and since it is a phenol, behaves as a
weak acid.

Amido-opianylpJienylhydrazide, C 16 H 15 N 3 O 3 , is obtained by the
reduction of the nitro-compound with tin and hydrochloric acid.
It crystallizes in fine needles, and oxidizes in the air to amido-

2266 Isonoropianic add, C 6 H 2 (OH) 2 (COH)CO 9 H(CO 2 H :
OH : OH : COH 1:3:4:5), is formed when the " following
compound is heated to 170 180 with hydrochloric acid. It
is tolerably soluble in cold, readily in hot water, and crystallizes
in yellowish needles, which melt with decomposition a few
degrees above 240. Its aqueous solution is coloured yellow
by alkalis and dark green by ferric chloride, this colour being
instantly changed to reddish violet by the addition of ammonia.
It reduces ammoniacal silver solution in the cold, and Fehling's
solution on boiling. 3

Methylisonoropianic acid or Aldehydovanillic acid, C 6 H 2 (OCH 3 )
(OH)COH(CO. 2 H), is formed, together with vanillin, when
vanillic acid is heated with caustic soda and chloroform. It
is readily soluble in alcohol, very slightly in cold, somewhat
more readily in boiling water, from which it crystallizes in fine,
silky needles, which melt at 221 222. As an aldehydo-acid

1 Liebermann, Bcr. Dcutsch. Chcm. Gcs. xix. 763.

2 Elbcl, ibid. xix. 2306.

3 Mendelsohn and Tiemann, ibid. x. 393.


it combines with acid sodium sulphite ; caustic soda colours the
solution an intense yellow, while ferric chloride produces a dirty
reddish violet colouration.

Its constitution follows from the fact that, in the synthesis of
aldehydes or aldehydo-acids from phenols by means of chloro-
form, the aldehyde group always takes either the ortho- or para-
position with regard to the hydroxyl. Since the latter is
occupied in vaniliic acid, the aldehyde group must lie next the
hydroxyl, and the two groups are thus found in aldehydovanillic
acid in the same relation as in salicyl aldehyde a view which is
confirmed by its behaviour towards caustic soda and ferric
chloride. 1

As a phenol it forms two series of salts. 2

Methyl aldehydovanillate, C 6 H 2 (OCH 3 )OH(COH)CO 2 .CH 3 , is
prepared by heating the acid with caustic potash, wood-spirit
and methyl iodide, and forms yellow needles, which melt at
134 135, and are soluble in carbonates of the alkalis.

Isopianic acid, C6H 2 (OCH 3 ) 2 (COH)CO 2 H. The methyl ether
of this compound is formed together with the foregoing com-
pound. It crystallizes from boiling water in fine needles, which
melt at 98 99, and are insoluble in the alkali carbonates.
It is readily saponified by hot caustic potash solution. The free
acid, which is precipitated by acids from this product, crystallizes
from water in fine needles, melting at 210 211, which give no
colouration with caustic soda or ferric chloride. It forms a
slightly soluble compound with acid sodium sulphite. 3

Quercimcric acid, C 8 H 6 O 5 +H 2 O. This substance, which is
very similar to isonoropianic acid, was obtained by Hlasiwetz
and Pfaundler by fusing quercitin with caustic potash. It
forms crystalline granules or small prisms, is readily soluble in
water, and reduces Fehling's solution and salts of silver. Ferric
chloride produces a blue colouration in the aqueous solution,
and an alkaline solution turns red in the air. On further fusion
with potash protocatechuic acid is formed. 4

1 Bcr. Deutsch. Chem. Gto.ix. 1278.

2 Mendelsohn and Ticmann, ibid. x. 395.

3 Ibid. x. 397. 4 Jahresber. 18CJ, 560.



2267 Hcmipinic acid or Dimethoxyorthophthalic acid, C 6 H 2
(OCH 3 ) 2 (CO 2 H) 2 , is, as already mentioned, a product of the
oxidation of opianic acid, and has also been obtained by the
oxidation of the alkaloids contained in opium, oxynarcotiu and
narcein. 1 It is readily soluble in alcohol, very slightly in cold,
more freely in boiling water, from which it crystallizes in colour-
less, distorted prisms with acute basal planes, containing two
molecules of water which are lost below 100. The anhydrous
acid melts at 180, and sublimes in lustrous plates, resembling
those of benzoic acid (Wohler). Crystals containing half a
molecule of water are obtained by the spontaneous evaporation
of its solution, while those deposited from a supersaturated
solution contain one molecule (Matthiessen and Foster). It
has a faint acid and slightly astringent taste, is decomposed into
carbon dioxide and dimethylcatechol on heating with soda-lime,
and is converted into rufiopin by hot sulphuric acid. Dilute
hydrochloric acid decomposes it at 160 170 into methyl
chloride, carbon dioxide, isovanillic acid and protocatechuic
acid (Wegscheider). Its aqueous solution is coloured yellowish
brown by ferric chloride, and gives a white precipitate with lead

Normal potassium Am*>mate,C 10 H 8 O 6 K 2 , is very soluble in
water and does not easily crystallize.

Acid potassium hemipinate, C 10 H 9 O 6 K, forms thick, six-sided
tablets, which are readily soluble in water and alcohol, and have
an acid reaction.

Normal silver hemipinate, C 10 H 8 6 Ag 2 , is a white precipitate,
insoluble in water.

Acid a-mcthyl hemipinate, C 6 H (OCH 3 ) 2 (C0 2 .CH 3 )CO 2 H +
H 2 0(OCH 3 :OCH 3 :C0 2 CH 3 :00 2 Hrr4:3:2:l), is prepared
by oxidizing methyl opianate with potassium permanganate, and
crystallizes from hot water in lustrous, narrow, flat needles,
which readily effloresce and when completely dehydrated melt
at 121 122. Its solution gives a yellowish brown precipitate
with ferric chloride.

1 Beckett and Wright, Journ. Chem. Soc. 1876, i. 461.


Acid fi-methyl hcmipinate, C 6 H 2 (OCH 3 ) 2 (C0 2 H)CO 2 .CH 3
(4 : 3 : 2 : 1), is formed by passing hydrochloric acid into a solu-
tion of hemipinic acid in methyl alcohol. It is readily soluble
in water and crystallizes from alcohol in arborescent needles or
stellate groups of prisms, and from benzene or chloroform in
rhombic tablets, which melt at 137 138. Its solution is not
precipitated by ferric chloride (Wegscheider).

Acid ethyl hemipinate, 2C 6 H 2 (OCH 3 ) 2 (CO 2 .C 2 H 5 )CO 2 H -f
3H 2 O, was prepared by Anderson by passsing hydrochloric acid
into the alcoholic solution of the acid. It is also formed
by heating hemipinic anhydride with 90 per cent, alcohol
(Matthiessen and Wright) and crystallizes from hot water in
fascicular groups of needles, melting at 141 142 (Wegscheider).
Its solution is precipitated by ferric chloride, so that it cor-
responds to the a-methyl ether, and not, as might have been
expected from its formation, to the /3-compound.

Hemipinic anhydride, C 10 H 8 5 , is formed when the acid is
heated for an hour to 180 (Beckett and Wright), by the action
of phosphorus pentachloride on the acid (Prinz) and by the
distillation of the methyl ether (Wegscheider). It crystallizes
from absolute alcohol, benzene, and xylene in lustrous needles,
which melt at 167 and readily sublime. On heating with zinc
dust and glacial acetic acid it is reduced to i/r-meconiri (Salomon).

2268 Nitrohemipinic acid, CeH(N0 2 XOCH 3 ) 2 (C0 2 H) 2 + H 2 O,
is best prepared by boiling nitro-opianic acid with pure nitric
acid. It is also formed when meconin or i/r-mecouin is heated
under pressure with nitric acid (Salomon), and crystallizes from
hot water in hard, yellow, vitreous prisms which lose water on
heating, melt at 155, and arc converted into the anhydride at
160 165; the latter crystallizes from benzene incompact, light
yellow prisms, and melts at 145 . 1

Amidohemipinic acid, C e H(NH 2 )(OCH 3 ). 2 (CO 2 H) 2 , was first
prepared from its anhydride and was then obtained by Griine by
reducing nitrohemipinic acid with caustic soda and ferrous
sulphate. The free acid is only known in its aqueous solution,
which is coloured yellow, showing a fine green fluorescence, has
an acid reaction and decomposes on evaporation.

Barium amidohemipinatc, C 10 H 9 NO ? Ba, is obtained by boiling
the anhydride with baryta water ; it is a golden coloured crys-
talline powder, which dissolves in dilute acids, but is insoluble
in water.

1 Griine, Her. Dcutsch. Chem. Gcs. xix. 2299.


Anhydro-amidohemipinic acid was prepared by Prinz by the
action of an acid solution of stannous chloride on a boiling
solution of nitro-opianic acid and was named azo-opianic acid. 1
Liebermann then pointed out that this substance is probably the
anhydride or anthranil of amidohemipinic acid : 2

(CH 3 0) 2 C 6 H/NH >0

The accuracy of this view was proved by Grime. It crystallizes
from alcohol in fine, colourless needles, which melt at 200 with
decomposition. When its solution in concentrated hydrochloric
acid is evaporated, the hydrochloride separates in stellate groups
of prisms, which lose their hydrochloric acid on drying. Its
potassium salt, (CH 3 O) 2 CH(CONH)CO 2 K, is a crystalline
powder, insoluble in alcohol. When it is boiled with acetic
anhydride and anhydrous sodium acetate the acetyl-compound
is formed, and crystallizes in needles which form an aqueous solu-
tion possessing a blue fluorescence. It readily decomposes
with formation of free acetic acid, and has the following con-
stitution :

(CH 3 0) 2 C 6 H(C0 2 H)< |

X N.C 2 H 3

Amidohcmipinylphenylhydrazide is formed by the continued
boiling of anhydro-amidohemipinic acid with alcohol, phenyl-
hydrazine hydrochloride, and sodium acetate, and also by the
oxidation of amido-opianylphenylhydrazide in the air :

x CO-NC 6 H 5

(CH 3 0) 2 C C H^CH N + O :

CO-NC 6 H 5
(CH 3 0) 2 C 6 H-C = N +H 2 0.

It crystallizes from benzene or alcohol in small, vitreous, honey-
yellow crystals belonging to the tetragonal system, which melt
at 222, 3

1 Journ. Prakt. Chem. [2] xxiv. 362.

2 Ber. Deutsch. Chem. Ges. xix. 351.

3 Liebermann, ibid. xix. 2275.


Diazohemipinic acid, (CH 3 O) 2 C 6 H(C0 2 H)<^Q>, is ob-
tained by the addition of hydrochloric acid to a cooled solu-
tion of sodium amidohemipinate and sodium nitrite. It forms a
light yellow, crystalline powder, which explodes by percussion or
on heating. When it is dissolved in warm hydrochloric acid, the
chloride, (CH 3 O) 2 C 6 H(CO 2 H) 2 N 2 C1, separates on cooling in long
needles, which are instantly converted by water into their
constituents (Gru'ne).

Opiakearime anhydride, C 10 H i) NO 4 . is formed when an alcoholic
solution of opianic acid and hydroxylamine hydrochloride is
allowed to stand :

C C H 2 (OCH 3 ) 2 < +H 2 N.OH


C 6 H,(OCH 3 ).,< | + 2H 2 0.


It crystallizes from benzene in long needles, which on careful
heating melt at 114 115, and are converted into acid
ammonium hemipinate by boiling with water. 1

Hemipinimide, C^HgN O 4 . This compound, which corresponds
to phthalimide, is formed when ammonium hemipinate is heated
and when an alcoholic solution of opianic acid is boiled with
hydroxylamine hydrochloride, the foregoing compound being
first formed and then undergoing an intramolecular change,
which also occurs when it is rapidly heated to 117; the
temperature rises suddenly to 260, and the liquid solidifies on
cooling to crystals of hemipinimide :

co-o co

- C 6 H 2 (0 ^

It crystallizes from hot water in splendid needles, which melt at
228 230 and readily sublime. Its aqueous solution has a fine
blue fluorescence. When it is triturated with a cold alcoholic
solution of potash, potassium hemipinimide, C 10 H 8 O 4 (NK), is
formed as a crystalline powder, whose aqueous solution gives
white precipitate of silver hemipinimide, C 10 H 8 O 4 (NAg), with
silver nitrate.

1 Licbermann, Ber. DciUsch. Chcm. Gcs. xix. 2923.



Ethyl hemipinimide, C 10 H 8 O 4 (NC. 2 H 5 ), is obtained when tho
potassium compound is heated to 150 with ethyl iodide. It
crystallizes from hot water or benzene in needles, which melt at
96 98. The solution also shows a blue fluorescence. 1

2269 Methylnorhemipinic acid, C 6 H 2 (OCH 3 )OH(CO 2 H) 2 +
2H 2 O (4:3:2: 1), is formed by heating hemipinic acid with
hydriodic acid for a short time, 2 and by heating acid a-methy]
hemipinate with hydrochloric acid. It forms warty crystals,
which are readily soluble in water and alcohol. It reduces
ammoniacal silver solution in the cold and Fehling's solution on
heating, gives a deep blue colouration with ferric chloride, and
melts at 152 155 with decomposition. It separates from
ether as an anhydrous powder, which melts at 223 225 with
evolution of gas (Wegscheider). On dry distillation it decom-
poses into isovanillic acid and carbon dioxide, and is converted
into protocatechuic acid by fusion with potash.

In its preparation from hemipinic acid, the compound
C 9 H 6 O 4 + 2H 2 O is formed as a by-product. It crystallizes in
lustrous prisms or thin tablets, which melt at 148. Its aqueous
solution is coloured lilac by ferric chloride.

This substance, which Liechti named opinic acid, might be
methylnorhemipinic anhydride, but this is considered doubtful
by Beckett and Wright since it contains water of crystallization,
and they assume that it corresponds to salicylide and has the
following constitution :

NitromethylnorJicmipinic acid, C 6 H(NO 2 )(OCH 3 )OH(CO 2 H) 2 ,
is formed when methylnorhemipinic acid is evaporated with dilute
nitric acid, and crystallizes from alcohol in almost white, silky
needles, which are readily soluble in water, and melt at 220 . 3

Amidomethylnorhemipinic acid, C 6 H(NH 2 )(OCH 3 )OH(CO 2 H) 2 ,
is not known in the free state; its barium salt separates in
lustrous, dull yellow plates when the anhydro-acid is boiled with
baryta water.

AnhydTo-amidomethylnorhemipinic acid,

(CH 3 0)(OH)C 6 H(CO 2 H)<^>0, is prepared by adding

1 Liebemiann, Ber. Deutsch. Ghent. Ges. xix. 2287.

2 Beckett and Wright, loc. cit. ; Liechti, Ann. Chcm. Pluirm. Suppl. vii. 149.

3 Elbel, Ber. Deutsch. Chcm. Gee. xix. 2306.


stannous chloride and hydrochloric acid to a boiling, saturated
solution of nitromethylnoropianic acid, and crystallizes in silky
needles, which melt at 174 175 with decomposition. On
boiling with acetic anhydride and sodium acetate, the diacetyl
compound is formed :

CH 3 (X /CO

C 6 H(C0 2 H)



cH 8 .co,CK NN.OO.CH,

It crystallizes in needles, melting at 20o, and yields a solution
in alcohol which has a blue fluorescence. Acetic anhydride is
set free on standing, the monoacetyl derivative, C 6 H(OCH 3 )
(OC. 2 H 3 0)(C0 2 H)(CONH), being formed. This body melts at
198 and does not form a fluorescent solution in alcohol.

Isohemipinic acid, C 6 H 2 (OCH 3 ) 2 (CO 2 H) 2 , is formed by the oxi-
dation of methyl isopionate with potassium permanganate.
The methyl ether is thus obtained, which crystallizes in needles
melting at 167, and yields the acid on hydrolysis. The latter
forms white needles, which are scarcely soluble in cold, more
readily in hot water, and melt at 245 24G (Mendelsohn and

2270 Dikydrnxyisophthalic acid, or Resorcinoldicarboxylic acid,
C 6 H 2 (OH) 2 (CO 2 H) 2 , When resorcinol is heated with caustic
soda and chloroform, dihydroxyisophthalaldehyde, CgH^OH)^
(COH) 2 , is formed, which is almost insoluble in cold water, but
dissolves readily in alcohol and ether, from which it is removed
by agitation with acid sodium sulphite without forming a
difficultly soluble compound. It crystallizes from hot water in

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