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needles, when the acid is heated and melts at 165 166.

a-Mdhylhydroxypliihalic acid, C 6 H 3 (OCH 3 )(CO. 2 H) 2 , is formed
by the oxidation of methylparahydroxyorthotoluic acid with
potassium permanganate, and crystallizes from water in stellate
groups of needles, which lose water on heating, forming the
anhydride, which sublimes in long needles and melts at 93 . 1

v-Hydroxyorthophthalic acid (3:1:2) is prepared by gently
fusing v-methylhydroxyphthalic acid with potash, and by means
of the diazo-reaction from the product of reduction of a-nitro-
phthalic acid, which contains amidophthalic acid. It separates
from hot water as a compact, crystalline mass, consisting of
short, hard prisms, which are partly converted by heating
into the anhydride, melting at 145 148, and are partly de-
composed into phenol and carbon dioxide. Its aqueous solution
is coloured a deep cherry-red by ferric chloride. When it is
heated to 200 with resorcinol, hydroxyfluorescein is formed.

Dinitro-v-hydroxypUhalic acid, C 6 H(NO 2 ) 2 (OH)(CO 2 H) 2 , was
first obtained by the action of nitric acid on juglon, a hydroxy-
naphthoquinone, C 10 H 5 (OH)0 2 , which occurs in green walnut
shells (Juglans regia), and was c&\\ed juglonic acid. It may also
be prepared by the nitration of v-hydroxyphthalic acid ; it is
exceptionally soluble in water, alcohol and ether, and separates
from petroleum ether in small crystals. Its acid potassium salt,
C 8 H 3 KN 2 O 9 , crystallizes in yellow, rhombic plates, which detonate
violently on heating. It can be recrystallized from nitric acid
or dilute sulphuric acid without undergoing decomposition. 2

v-MethylJiydroxyphthalic acid has been prepared by the
oxidation of v-methylorthohomometahydroxybenzoic acid ; it is
tolerably soluble in water, and crystallizes in microscopic prisms,
which melt at 160, and are thus converted into the anhydride,
which sublimes in needles and melts at 87. 8

1 Schall, Ber. Deutsch. Chem. Oes. xii. 829.

2 Bernthsen and Semper, ibid, xviii. 210 ; xix. 164.

3 Jacobsen, ibid. xvi. 1962.


2258 a-Hydroxyisophihalic acid (4:1:3) is formed, together
with a large quantity of hydroxytrimesic acid, C C H 2 (OH)(C0 2 H) 3 ,
when carbon dioxide is passed over disodiura salicylate heated
to 370 380 . 1 It may be obtained in a similar manner from
parahydroxy ben zoic acid, which first changes into salicylic acid. 2
It is also formed by the oxidation of para-aldehydosalicylic acid
or ortho-aldehydoparahydroxybenzoic acid with potassium per-
manganate, and when this acid, 3 a-metaxylenol, 4 or a-metaxylene-
sulphonic acid, 5 is fused with potash. When an alkaline solution
of salicylic acid is heated to 120 130 with tetrachloromethane,
a-hydroxyisophthalic acid is obtained, together with a little
v-hydroxyisophthalic acid.

In order to prepare it, phenol is dissolved in an alkaline solu-
tion which contains one molecule of potash to three of soda, the
mass evaporated and carbon dioxide passed over the dry residue
for some time at 120 160, the temperature being finally raised
to 300 320. The chief product of the reaction is a-hydroxy-
isophthalic acid accompanied by parahydroxy benzoic acid and
hydroxytrimesic acid, almost two-thirds of the phenol coming
over unchanged. The residue is decomposed with hydrochloric
acid, and the a-hydroxyisophthalic acid repeatedly recrystallized
from water. 7

It forms long needles, which cross each other at an angle of
60, melt at 305 306, and dissolve at 10 in 5,000, at 24 in
3,000, and at 100 in 160 parts of water. It is readily soluble
in alcohol and ether, but not in chloroform, by means of which
it can be separated from hydroxytrimesic acid. Its aqueous
solution is coloured a deep cherry-red by ferric chloride. On heat-
ing to 200 with hydrochloric acid, it decomposes into phenol
and carbon dioxide, while on dry distillation it yields salicylic
acid, phenol and carbon dioxide. When its disodium salt, C 6 H 3
(OH)(CO 2 Na) 2 , is heated to 250, the trisodium salt, C 6 H 3 (ONa)
(C0 2 Na) 2 , is obtained, together with phenol and carbon dioxide,
while the potassium salt yields a large amount of parahydroxy-
benzoic acid when heated to 280 300 (Ost).

a-MethoxyisopUhalic acid, C H 3 (OCH" 3 )(CO 2 H) 2 , is formed by

1 Ost, Journ. Prakl. CJiem. [2] xiv. 99.

2 Knpferberg, ibid. [2] xvi. 423.

3 Tiemann and Reimer, Bcr. Dcutsch. C'hcm, Ges. x. 1571.

4 Jacobsen, ibid. xi. 377.

5 Jacobseu and Remsen, ibid. xi. 377.
8 Hasse, ibid. x. 2195.

7 Ost, Journ. Prakt. Chcm [2] xv. 301


the oxidation of a-metaxylenyl monomethyl ether, 1 or methyl-
parahomosalicylic acid 2 with potassium permanganate, and
crystallizes from hot water in microscopic needles, melting
at 261 (Schall).

Dimethyl a-hydroxyisophthalate, C 6 H 3 (OH)(CO 2 .CH 3 ) 2 , forms
large, flat needles which melt at 96 (Jacobsen).

Dicthyl a-hydroxyisophthalate, C 6 H S (OH)(CO 2 .C 2 H 5 ) 2 , crystal-
lizes in fine needles, which melt at 52 and are soluble in caustic
soda (Ost).

v-Hydroxyisoplithalic acid (2:1:3) is formed when ortho-
aldehydosalicylic acid 3 or sulphamido-isophthalic acid 4 is fused
with potash. It crystallizes in hair-like needles, which melt at
243 244, dissolve in 700 parts of water at 24, and in
35-40 parts at 100. Ferric chloride produces a cherry-red
colouration ; the aqueous and alcoholic solutions show a bluish
violet fluorescence, which is destroyed by alkalis. The acid de-
composes on heating, the chief portion being resolved into
salicylic acid and carbon dioxide.

v-Methoxyisophthalic acid, C 6 H 3 (OCH 3 )(CO 2 H) 2 , is prepared by
the oxidation of methylorthohomosalicylic acid and crystallizes
from water in prisms, which melt at 216 218, turning brown
and subliming at the same time (Schall).

s-Hydroxyisophthalic acid (5 : 1 : 3) is obtained by fusing s-sul-
pho-isophthalic acid with potash, and by means of the diazo-
reaction from amido-isophthalic acid. It crystallizes from hot
water, in which it readily dissolves, in fascicular groups of
needles with two molecules of water, which are lost at 100.
It melts at 288 and sublimes in broad, lustrous needles, which
dissolve in 3280 parts of water at 5 and are coloured a faint
yellow by ferric chloride. It decomposes into phenol and
carbon dioxide on distillation with lime : 5


Dimethyl s-hydroxyisophthalate, C 6 H 3 (OH)(CO,.CH 3 ) 2 , fine

needles 160

Diethyl s-hydroxyisophthalate, C 6 H 3 (OH)(CO 2 .C 2 H 5 ) 2 , mono-
clinic prisms 10SJ

2259 Hydroxytcrcphthalic acid (2:1:4) was prepared by
Warren de la Rue and Mullet from amidoterephthalic acid by

1 Jacobsen, Ber. Dcutmsh. Chcm. Qc*. xi. 898. Schall, ibid. xii. 828.

3 Tiemann and Kleiner, ibid. x. 1570. 4 Jacolwcn.

5 Heine, Bcr. Deutsch. Chcm. Gcs. xii. 494 ; Lonnies, ibid. xin. 705.


the action of nitrons acid. 1 It is also formed when paraxylenol, 2
bromoterephthalic acid, 3 ortho-aldehydometahydroxybenzoic acid, 4
or metahydroxyparatoluic acid 5 is fused with caustic potash.

In order to prepare it, amidoterephthalic acid is dissolved in
dilute sulphuric acid, treated with sodium nitrite and boiled.
It forms a powder, which is slightly soluble in hot water, readily
in alcohol, and sublimes on heating with partial decomposition
without previously melting. Its aqueous solution is coloured an
intense violet-red by ferric chloride. When it is mixed with
sand and submitted to dry distillation, it decomposes into carbon
dioxide and phenol, and on heating with hydrochloric acid to
220 is resolved into carbon dioxide and metahydroxybenzoic
acid, while fusion with an excess of caustic potash converts it
into salicylic acid, together with a smaller amount of metahy-
droxybenzoic acid. 7

Mcthocryterephthalic acid, C 6 H 3 (OCH 3 )(CO 2 H) 2 , is formed by
the oxidation of methylmetahomosalicylic acid 8 and crystallizes
from hot water in small prisms, which melt at 277 279, and
are resolved into methyl chloride and hydroxyterephthalic acid
by hydrochloric acid at 160.

Dimethyl hydroxytereplithalate,C^(OW)(VQ v VR.^ Ci , isobtained
by passing hydrochloric acid into a solution of the acid in methyl
alcohol, and crystallizes in splendid, silky needles, which melt at
94 and are soluble in hot water, readily in alcohol. Ferric
chloride gives a somewhat fainter colouration than with the free
acid. When the ethereal solution is shaken up with caustic
soda solution, the sodium compound, C c H 3 (ONa)(CO 2 .CH 3 ) 2 , is
formed as a white paste. On heating the acid with caustic
soda, methyl iodide and wood-spirit, the trimethyl ether, C C H 3
(OCH 3 )(CO 2 .CH 3 ) , is obtained as an oily, pleasant-smelling

Dimethyl acetoxyterepUUate, C H 3 (OCO.CH 3 )(CO 2 .CH 3 ) 2 , is
prepared by heating the dimethyl ether with acetyl chloride,
and crystallizes from alcohol in cauliflower-like masses of fine
needles, melting at 76 (Burckhardt).

DinitroJiyaroxytcrepUJialic acid, C 6 H(NO 2 )(OH)(CO 2 H) 2 , is

Ann. diem. Pharm. cxxi. 96.

Jacobsen, Ber. Dcutsch. Chem. Oes. xi. 570.

Fischli, ibid. xii. 621.

Tiemann and Landshoff, ibid. xii. 1336.

Hall and Remsen, ibid. xii. 1433.

Burckhardt, x. 144.

Earth and Schreder, xii. 1260.

Schall, ibid. xii. 828.


formed by the action of a mixture of concentrated nitric acid and
fuming sulphuric acid on hydroxyterephthalic acid. It is readily
soluble in water, from which it separates in golden yellow, trans-
parent crystals, .resembling those of calc-spar, which are, like the
yellow and red salts of the acid, explosive. 1



2260 In 1832, Couerbe detected meconin, 2 C 10 H 10 4 , in opium,
and Wohler and Liebig, in 1842, obtained opianic acid*
C 10 H 10 O 5 , by the oxidation of narcotin or opian, which is also an
opium alkaloid. This acid was more closely investigated by
Wohler, who found that it is converted by further oxidation into
liemipinic acid, C 5 H 5 3 . He assumed that in its formation one
molecule of opianic acid took up oxygen and formed two mole-
cules of hemipinic acid ; he says : " It contains a radical which
consists of half the radical of opianic acid, and this is referred to
in its name." 4

Anderson, who also investigated the products of oxidation of
narcotin, obtained a substance, opianyl, in addition to these acids,
and pointed out that it shows an interesting relation to opianic
and hemipinic acids when the formula of the latter of these is
doubled, as his and Laurent's 5 researches had shown to be
necessary. " For we have as follows :

Opianyl ..... C 10 H 10 O 4 ,
Opianic acid . . . C 10 H 10 O 5 ,
Heraipinic acid . C^H^O^,

as though these three compounds were different oxidation pro-
ducts of the same radical." 6

He subsequently found that opianyl is identical with me-
conin. 7

Matthiessen and Foster then made the important observation,

Burckhardt, Bcr. Deutseh. Chan. Gcs. xii. 1273.
Ann. Chim. Phys. xlix. 44 ; 1. 337 ; lix. 148.
Ann. Chcm. PJiarm. xliv. 126.
Ibid 1 1 * Compt. Rend. xx. 1118.

Ann. Chcm. Pharm. Ixxxvi. 179. 7 7/. x-viii. 41.



that when opianic acid is evaporated with caustic potash solution
it is resolved into meconin and hemipinic acid :

They also found that opianic acid is reduced to meconin
by the action of water and sodium amalgam :

C 10 H 10 5 + 2H = C 10 H 10 4 +H 2 0.

These highly characteristic reactions receive, according to
them, a simple explanation, if it be assumed that a very un-
stable hydrate of meconin, C 10 H 12 5 , is first formed. The de-
composition of opianic acid then becomes quite analogous to
that of benzaldehyde into benzyl alcohol and benzoic acid, and
the reduction of the former also corresponds to that of benzalde-
hyde to benzyl alcohol.

By heating hemipinic acid with concentrated hydriodic acid,
they obtained carbon dioxide, methyl iodide and hypogallic acid,
according to the equation :

C 10 H 10 6 +2HI = C0 2 + 2CH 3 I + C 7 H 6 O 4 -

If hydrochloric acid be employed, methylhypogallic acid,C s H. 8 O i
is first formed, and is converted into hypogallic acid by further

Hemipinic acid, therefore, as well as opianic acid and meconin,
contains two methyl groups, and the three bodies in question
are derivatives of the still unknown normal compounds :

Normeconin . . . . C 8 H 6 O 4 ,
Noropianic acid . . C 8 H 6 O 5 ,
Norhemipinic acid . C 8 H 6 O 6 ,

as they may be shortly designated, ordinary meconin being thus
dimethylnormeconin, &c.

They then succeeded in converting the latter, as well as
opianic acid, into methylnormeconin, C 9 H 8 4 , and methylnor-
opianic acid, C 9 H 8 5 , by heating with hydrochloric or hydriodic
acid. They finally considered hemipinic acid to be dimethyl-
dihydroxyterephthalic acid and looked upon opianic acid as the
corresponding aldehydo-acid, 1 but, as shown by Matthiessen and
Wright, the former can be readily converted into an anhydride,
and must therefore be dimethyldihydroxyphthalic acid.

1 Phil. Trans. 1863, 345 ; Journ. Chem. Soc. [2] T. 342 ibid. vi. 357.


Liebermann and Chojnacki proposed the following formula
for opianic acid :

C H. 2 (OCH S ) /


and this was confirmed by the researches of Beckett and
Wright, who also found that hypogallic acid is identical with
protocateclmic acid.

In the case of meconin there were two possibilities ; it might
be either hemipinic aldehyde or the anhydride of an alcoholic
acid :

C 6 H 2 (OCH 3 ) 2 ( C 6 H 2 (OCH 3 ) 2 < )0.

\COH \CO '

The facts that it is formed from opianic acid by the action of
nascent hydrogen, and cannot be re-oxidized to opianic acid,
while the latter is converted into meconin and hemipinic acid by
heating with caustic potash, are in favour of the latter view.

Beckett and Wright then proved that this view is correct, and
their results were confirmed by the researches of Hessert. 1
Hemipinic acid is dimethylcatecholdicarboxylic acid, and can
readily be converted into protocatechuic acid or catecholcar boxylic
acid, in which the side-chains have the position C0 2 H : OH : OH =
1:3:4. Since hemipinic acid is simultaneously a derivative of
phthalic acid, the second carboxyl group must be either in
position 2 or 6 ; in the latter case it would yield only one
acid methyl ether, while in the former two such compounds
would be possible. Wegscheider has now found that two such
isomerides exist, 2 and he has also obtained isovanillin by heating
opianic acid with dilute hydrochloric acid, 3 while Beckett and
Wright found that methylvanillin is formed when sodium
opianate is distilled with soda-lime.

It follows from these facts that the constitutions of the three
compounds in question are represented by the following formulae :
Mceonin. Opianic acid. Hemipinic a


co co.oH

OCH, \/OCH 3


1 Journ. Chcm. Soc. 1876, i. 164, 281, 461.

* Monatsh. Chcm. iii. 348. 3 /*' m. **

K K L 1


Meconin therefore stands to hemipinic acid in the same rela-
tion as phthalide to phthalic acid.

2261 Meconinic acid or Hydroocymethyldimcthoxylenzoic acid,
C 6 H 2 (OCH 3 ) 2 (CH 2 .OH)CO 2 H, is not known in the free state.
When its lactone, meconin, is dissolved in baryta water, barium
meconinate, (C 10 H 11 O 6 ) 2 Ba, is formed, and is left on evaporation
as a gummy mass x (Kessert), while Prinz obtained it in fine,
silky needles. 2 This salt, however, yields meconin on decom-
position with a strong acid. The copper and silver salts are precipi-
tates, which decompose on heating with formation of meconin.

Meconin, C 10 H 10 O 4 , as already mentioned, occurs in opium.
Anderson obtained it, accompanied by other products, by the
oxidation of narcotin with nitric acid, and it is also formed by the
reduction of opianic acid.

In order to prepare it, the mother liquor of the opium alka-
loids is extracted with ether, the solution evaporated, and the
residue washed with hydrochloric acid and re-crystallized from
water (Anderson). It forms white, lustrous needles, which have
a bitter taste, melt at 102 102'5 (Wright), and when carefully
heated sublime in splendid needles. It is readily soluble in
alcohol and ether, and requires 22 parts of boiling water and
700 parts of water at 15'5 for solution. On heating with
concentrated sulphuric acid, a purple-coloured solution is formed.

It forms ethers when heated with stearic or benzoic acids, as
was shown by Berthelot, who concluded from this that it is an
alcohol. 3

Chloromeconin, C 10 H 9 C10 4 , was prepared by Anderson by the
action of chlorine on fused meconin or on its aqueous solution.
It crystallizes in colourless needles, which are scarcely soluble in
cold, somewhat more readily in hot water, and more freely in
alcohol, melt at 175 and sublime without decomposition.

Bromomeconin, C 10 H 9 BrO 4 , crystallizes from alcohol in colour-
less needles, melting at 167.

Icdomeconin, C 10 H 9 IO 4 , is formed by the action of chloride of
iodine on : an aqueous solution of meconin, and forms long
crystals or needles, which melt at 112, and decompose when
more strongly heated.

Nitromeconin, C 10 H 9 (NO 2 ) 2 O 4 , is obtained by dissolving meconin
in cold, concentrated nitric acid, and precipitating with water.
It crystallizes from alcohol in white needles or prisms, which

1 Bcr. Dcutsch. Chrm. Ges. xi. 240. 2 Journ. Prakt. Chem. [2] xxiv. 373.
3 Ann. Chim. P/njs. [3] Ivi. 51 \Ann. Chcm. Pharm. cxii. 356.


melt at 160, and sublime when carefully heated. It forms a
yellow solution in hot alkalis and is not re-precipitated by acids,
nitromeconinic acid being probably formed.

Amidomeconin, C 10 H 9 (NH 2 )O 4 , is prepared by warming the
preceding compound with iron filings and acetic acid. It is
precipitated by water as a jellowish powder, which is only
slightly soluble in benzene, and melts at 171.

Metkyl normeconin, C 6 H 2 (OCH 3 )(OH)C 2 H 2 O 2 , is formed when
meconin is heated with hydrochloric or hydriodic acid (Mat-
thiessen and Foster), and when meconin or narcotin is carefully
fused with caustic potash (Beckett and Wright). It crystallizes
from hot water in prisms, which melt at 125; ferric chloride
colours the aqueous solution a beautiful blue, which is converted
into red by the addition of ammonia. On further fusion with
potash it is converted into protocatechuic acid.

tjr-Meconin. When hemipinimide, which will be further' de-
scribed below, is boiled with tin and hydrochloric acid, hemi-
pinimidine is formed :


(CH 3 0).,C 6 H 2 < >0 + 4H = (CH 3 0) 2 <( >O +H 2 O.

This substance crystallizes from benzene in small plates, which
melt at 181, and are converted into nitrosohemipinimidinc,
C 10 H 10 O 3 N(NO), by the action of sodium nitrite on their
solution in hydrochloric acid. The latter compound crystallizes
from hot alcohol in silky, yellow needles, and dissolves in caustic
soda solution with evolution of nitrogen. Hydrochloric acid
added to this solution precipitates ^-meconin, which crystallizes
from hot water in colourless needles, melting at 123 124.
Its isomerism with meconin is shown by the following formula :

co >0


Nttro-^-mcconin, C^NO^O,, crystallizes in splendid,
yellowish needles, which melt at 166.

Amido-^-meconin, C^H^NH^O,, resembles amidomeconin,
but is readily soluble in benzene, and melts at 165 . 1
1 Salomon, Bcr. Dciilsch. Chcm. Gcs. x.x. 883.


Meconiosin, C 8 H 10 O 2 , also occurs in opium, and crystallizes in
plates, which melt at 88 and dissolve in 27 parts of cold water,
and in almost every proportion in boiling water. On heating
with sulphuric acid a splendid green solution is formed. 1


C 6 H 2 (OH) 2 <


2262 Noropianw acid, 2C 8 H 6 O 5 -f 3H 2 O, was obtained by
Wright, together with methyl iodide, by boiling opianic acid
with four times its weight of 50 per cent, hydriodic acid. It is
readily soluble in water and crystallizes in fine prisms, which
become anhydrous at 100 and melt at 171. Its solution is
coloured greenish blue by ferric chloride, the addition of
ammonia or carbonate of sodium changing the colour to
brownish red. It reduces ammoniacal silver solution in the cold
and forms a yellow or brown solution in alkalis. The lead salt
is a canary-yellow precipitate. 2

Methylnoropianic acid, C 6 H 2 (OCH 3 )OH(COH)CO. 2 H, was
prepared by Matthiessen and Foster from opianic acid by
heating it with hydrochloric or hydriodic acid. In order to
prepare it, hydrochloric acid is passed into a warm solution of
50 grms. of opianic acid in 600 cb. cms. of strong hydrochloric
acid until no opianic acid separates after standing for about two
days. The solution is then concentrated, the paste of crystals
thus obtained dissolved in water, the solution neutralized
exactly with ammonia and treated with barium chloride, which
produces a brown precipitate. The addition of ammonia to the
filtrate precipitates the barium salt of the acid, which is then
washed and decomposed with sulphuric acid. 3

It is readily soluble in water and crystallizes in nacreous
] lates, long prisms, or transparent vitreous columns, which contain
different amounts of water, but all readily effloresce in the air.
The anhydrous acid melts at 154; its aqueous solution is
coloured dark blue by fenic chloride, and on the addition of
ammonia light red.

1 T. and H. Smith, Pharm. Journ. Trans. [3] viii. 981.

2 Journ. Chcm. Soc. 1877, ii. 545.

3 Prinz, Journ. Pmkt. Chcm. [2] xxiv. 368.


As a phenol-acid it forms two series of salts.

Silver methylnoropianate, C 9 H 7 O 5 Ag, is a gelatinous precipitate,
which becomes crystalline on standing. It is soluble in hot
water and separates in crystals when the solution is cooled.

Barium methylnoropianate, C 9 H c 5 Ba + H 2 O, is also thrown
down in the gelatinous state and changes into granular crystals
on standing.

Cldoromcthylnoropianic acid, C 6 HC1(OCH 3 )OH(COH)CO 2 H,
is obtained by the action of potassium chlorate and hydrochloric
acid on methylnoropianic acid, and crystallizes from hot water in
large, lustrous needles, which melt at 206 (Prinz).

NUromethylnoropianic acid, C 6 H(NO 2 )(OCH 3 )OH(COH)CO 2 H
+ H 2 O, is formed when methylnoropianic acid is treated with
dilute nitric acid (Matthiessen and Foster). It is also obtained
by heating nitro-opianic acid for some time with hydrochloric
acid. It crystallizes in radiating needles, which lose their water
at 120 and melt at 203 . 1

2263 Dimcthylnoropianic acid or Opianic acid, C 6 H 2 (OCH 3 ) 2
(COH)CO 2 H, was prepared by Wohler and Liebig from narcotin
by boiling it with dilute sulphuric acid and manganese dioxide.
Blyth found that it is also formed by heating with platinum
chloride, 2 and Anderson obtained it by oxidizing narcotin with
dilute nitric acid. In order to prepare it according to the
method proposed by Matthiessen and Foster, 100 grms. of
narcotin are heated with 1,500 grms. of water and 150 grms. of
sulphuric acid until the mixture boils ; 150 grms. of finely
powdered pyrolusite, corresponding to 90 grms. of manganese
dioxide, are then added somewhat rapidly and the hot solution

Opianic acid separates out on cooling and is purified by
recrystallization. Wohler, in order to obtain it perfectly colour-
less, dissolved it in sodium hypochlorite, heated to boiling, and
then added an excess of the hypochlorite. The decolourization
may also be effected, according to Prinx, by passing the gases
evolved from nitric acid and arsenic trioxide through the hot
solution ; and it may also be obtained perfectly white by running
potassium permanganate into the hot solution acidified with
sulphuric acid until it becomes sherry-yellow. 3 The portion
which is left in the mother-liquor from its preparation can be

1 Elbel, Bcr. Dautsch. Chcm. Ges. xtx. 2306.

2 Ann. Chcm. Phnrm. 1. 29.

;t Trinz, Joiirn. Prakt. Chcm. [2] xxiv. 353.


removed by ether, which does not dissolve the colouring matter

It is slightly soluble in cold, readily in hot water, alcohol and
ether, and crystallizes in thin, narrow prisms or silky needles, which
melt at 150 (Wegscheider) and decompose on further heating,
giving off a vapour which smells like vanilla (Wohler). It
has a faint acid reaction and a slightly bitter taste. Sodium

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