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Retzius, in 1783, treated the dried extract of nut-galls with
cold water, and in this way obtained a substance which had the
properties of an acid and effervesced with alkaline carbonates.
In 1786, Scheele prepared gallic acid by exposing extract of nut-
galls to the air in a warm place and frequently removing the
film of mould which was formed. The crystalline precipitate
which gradually separated out was purified by recrystaliization.
He observed that when gallic acid is heated a body sublimes
which also precipitates iron salts, but which he considered to be
different from gallic acid, a view which was also taken by
Berthollet in his Stalique chimique, 1803, while Fourcroy and
Berzelius believed that the sublimate is the pure gallic acid, this
being denied by Braconnot and also by Pelouze (Part III., p.
189). The astringent constituent of nut-galls, subsequently
called tannic acid, was first recognized as a distinct substance
by Deyeux in 1793, and more definitely by Seguin in 1705,
after which Berzelius obtained it in a pure or almost pure con-
dition. It had already been noticed that it is readily converted
into gallic acid, but the relations of the two substances had not
been explained, although many chemists had investigated the
question.



GALLIC AND TANNIC ACIDS. 305



Pelouze and Berzelius gave to tannic acid the formula
C 18 H 18 12 , which was altered by Liebig to C 18 H 16 O 12 , since tbe
latter explains in a simple manner its conversion into gallic
acid in presence of water and oxygen : " From one atom of
tannic acid and four atoms of oxygen, exactly two atoms of
gallic acid and two atoms of carbonic acid are formed, while
according to the formula C 18 H 18 O 12 , two atoms of hydrogen
remain over, and no one knows what becomes of them." l At
a later period he proposed the formula C 18 H 10 O 9 + 3aq, which
can be expressed as the sum of the formulae of anhydrous
acetic acid and gallic acid ; he had found that tannic acid can
be converted into gallic acid without the intervention of oxygen
by simply boiling for a few minutes with caustic potash, or'
better, dilute sulphuric acid. 2 He could not, however, detect
any acetic acid and suggested that an isomeride of this is
formed, which, however, from the behaviour of tannic acid
towards sulphuric acid, could not be a sugar 3 as had been
suggested by Stas. 4

Wetherill, on the other hand, assumed that tannic and gallic
acids were isomeric, 5 while Mulder gave to the former the
formula C 14 H 10 O 9 , according to which it forms two molecules of
gallic acid by the assumption of the elements of water;
subsequently, however, he altered his formula to C 14 H 12 O 9 , and
looked upon gallic acid as an oxidation product. 7

Tannic acid was then carefully investigated in Liebig's
laboratory by Strecker, who succeeded in resolving it into grape
sugar and gallic acid, expressing the reaction by the following
equation : 8



C 27 H 22 17 + 4H 2 = 3C 7 H 6 5 + C 6 H 12 O



This view was almost universally accepted, the more so as
other tannic matters had proved to be glucosides, and as
the formation of gallic acid by fermentation received a simple
explanation. According to Strecker's equation, 29 "1 per cent.
of grape sugar should be formed, while he only obtained 15 22
per cent., and Rochleder found that by proper purification the
amount can be reduced to 4 per cent, without altering the
chemical and physical properties of the tannic acid to any

1 Ann. Chcm. Pharm. x. 172. 2 Ibid. xxvi. 128.

3 Handb. Chcm. 854. Ann. Chem. Pharm. xxx. 205.

8 Journ. Prakt. Chcm. xlii. 247. 6 Jahrcsb. Chcm. 1848, 524.

7 Ibid. 1858, 261 8 Ann. Chtm. Pharm. xc. 328.



366 AROMATIC COMPOUNDS.

important extent. 1 His results confirmed those of Knop, who
succeeded in converting 95 per cent, of the tannic acid into
gallic acid, ellagic acid, C U H 6 O 8 , and a carbohydrate being also
formed. 2 Stenhouse had previously arrived at similar results,
having found that by the use of sufficiently dilute sulphuric
or hydrochloric acid almost the whole of the tannic acid can be
converted into gallic acid. 3

Rochleder then assumed that the sugar is formed from some
admixture, and that tannic acid stands in the same relation to
gallic acid as dextrin to grape sugar. Hlasiwetz remarks on
this question : " If tannin is not a glucoside, it may perhaps be
a digallic acid, which corresponds to gallic acid in the same way
as diethylene alcohol to ordinary glycol, and it would then have
the formula which was first proposed for it by Mulder :

2C 7 H 6 5 -H 2 = C 14 H 10 9 .

" The analyses of tannin and its salts agree with this com-
position as well as can be expected in the case of a substance
which is so difficult to purify." 4

Lowe, however, came to a different conclusion ; he found that
silver nitrate and arsenic acid are reduced by gallic acid with
formation of ellagic acid and a substance which has all the pro-
perties of tannic acid, so that he considered the latter to be an
oxidation product of gallic acid. 5 He subsequently found that
the correct formula of tannic acid is C 14 H 10 9 , but assumed that
gallic acid is not formed from it only by assumption of water,
but that a molecular change takes place. 6

Schiff, on the contrary, showed conclusively that arsenic acid
and also phosphorus oxychloride simply exert a dehydrating
action, and that the digallic acid thus formed is identical with
tannic acid. This question will be more fully considered under
the latter.

2202 Gallic acid occurs ready formed in nut-galls, sumach and
divi-divi, the fruit of Caesalpinia coriaria? It is also found in the
leaves of the red bear-berry (Arctostaphylos Uva ursi), s in China
tea, 9 and in red Biiudner wine. 10 Etti obtained it by heating

Chem. Ocntralbl. 1858, 579. 2 Pharm. Centrum. 1855, 658.

Chf/m. Soc. Mem. i. p. 147. 4 Ann. Chem. Pharm. cxliii. 295.

Journ. Prakt. Chem. cii. Ill ; ciii. 446.

Frcsenius' Zeitschr. xi. 365.

Stenhouse, Chcm. Soc. Mem. i. 137.

Kawalier, Jahrcsb. Chem. 18?2, 683.

Hlasiwetz and Malin, Zeitschr. Chcm. 1867, 271.

Simler, Jahresb. Clum. 1861, 923.



GALLIC ACID. 3(57



kinoin, C 14 H 1J? O 6 , with hydrochloric acid; 1 it is also formed
when di-iodoparahydroxybenzoic acid, 2 bromoprotocatechuic acid, 3
bromoveratric acid, 4 and a-bromoresorcylic acid, 5 are fused with
caustic potash. According to Lautemann it is also formed in
tins way from di-iodosalicylic acid, 6 but Demole failed to obtain
it by this method, 7 and it is probable that Lautemann's com-
pound, which was only obtained in small quantity, is the isomeric
pyrogallolcarboxylic acid.

In order to prepare gallic acid, Scheele's method, which is
stated by Liebig to give the best yield, is made use of. Finely
powdered nut-galls are extracted with cold water and the solution
allowed to stand in a warm place, the precipitated acid being
recrystallized from boiling water.

According to Braconnot, the entire nut-galls may be moistened
with water in summer or allowed to stand in a warm place until
they form a paste, which is then extracted with boiling water. 8

The spores of Penicillium glaucum or Aspergillus niger are
necessary to set up fermentation. 9 Wittstein recommends the
addition of beer yeast ; he thus obtained almost 50 per cent,
from Chinese nut-galls, while without the yeast the yield only
amounted to 17 per cent. 10 One hundred pounds of Turkish
nut-galls, treated by Scheele's method, give 24 pounds of gallic
acid. 11

It crystallizes in silky needles or asymmetric prisms, containing
one molecule of water, which is lost at 120, has an acid,
astringent taste, and dissolves in 130 parts of water at 12'5, and
in 3 parts at 100. It is more readily soluble in alcohol, since
27-95 parts dissolve in 100 parts of absolute alcohol at 15,
and 18-90 parts in 100 parts of 90 per cent, alcohol, while 100
parts of ether only dissolve 2'5 parts. 12

Gallic acid commences to melt above 220 and decomposes
into carbon dioxide and pyrogallol when more strongly heated.
It is readily oxidized, reduces Fehling's solution and the salts of
the noble metals, and in alkaline solution absorbs oxygen. When

Ber. Dcutsch. Chcm. Gc*. xi. 1881.

Earth and Senhofer, ibid. viii. 1884.

Ibid. 4 Matinoso, ibid. xi. 140.

Earth and Senhofor, Ann. Chem. Phann. clxiv. 118.

Ibid. cxx. 137.

Ber. Dcutxch. Chcm. Gcs. vii. 1441.

Ann. Chim. Phys. ix. 181.

Tieghem, Zeitschr. Chem. 1868, 222.

10 Vicrtcljahrsschr. Pluirm. ii. 72.

11 Steer, Jahrcbcr. Chem. 1856, 482.

a - Bourgoin, Bull. Xoc. Chim. xxix. 245.



363 AROMATIC COMPOUNDS.

it is added to ferric chloride, a partial reduction ensues
and a black-blue precipitate is formed, which dissolves in the
excess of ferric chloride with a green colour. According to
Etti, the colouration depends mainly on the concentration of
the solutions, and varies between black-blue, black -green, blue,
greenish and brownish green. An excess of gallic acid destroys
the colour and effects complete reduction to ferrous chloride ; a
solution of pure ferrous sulphate in absence of air is therefore
not altered by it, but on exposure to air is coloured a bright blue,
and deposits a black precipitate without becoming decolourized.

Gallic acid in alcoholic or alkaline solution reduces paranitro-
benzyl chloride to paranitrotoluene. Digallic acid and pyro-
gallol have a similar action. 1

It is converted by the action of potassium chlorate and
hydrochloric acid into tricarballylic acid, C 3 H 5 (C0 2 H) 3 , and
isotrichloroglyceric acid, CC1 3 .C(OH) 2 .C0 2 H, which crystallizes in
needles and is readily decomposed by alkalis into chloroform and
oxalic acid. 2

When gallic acid is heated with sulphuric acid, rufigallic acid
or hexyhydroxyanthraquinone, C U H 2 O 2 (OH) 6 , is formed, while an
acid solution of potassium permanganate produces hydrorufigallic
acid, C 14 H 8 6 .

Gallic acid is not precipitated by gelatine solution, and can
thus be distinguished from tannic acid and other similar
substances.

2203 The Gallates have been chiefly investigated by Buchner.

Sodium gallate, C 6 H 2 (OH) 3 C0 2 Na + 3H 2 O, is obtained by
adding alcoholic soda to a solution of the acid in alcohol as a
granular, crystalline precipitate, which crystallizes from a very
concentrated aqueous solution in pointed yellow plates.

Potassium gallate, C 6 H 2 (OH) 3 C0 2 K + C 6 H 2 (OH) 3 CO 2 H+H 2 0,
is a light, crystalline powder which is prepared in a similar
manner to the sodium salt ; the normal salt has not yet been
obtained.

Ammonium gallate, C 6 H 2 (OH) 3 CO 2 NH 4 + H 2 0, is formed
when ammonia is passed into a solution of the acid in absolute
alcohol, and crystallizes from water in fine needles. When its
solution is boiled, the acid salt, C 6 H 2 (OH) 3 C0 2 NH 4 + C 6 H 2 (OH) 3
CO 2 H, is deposited on cooling in splendid crystals. 3 It is also

1 Pellizzari, Gazz. Clicm. Ilnl. xiv. 481.

2 Schreder, Ann. Chem. Pharm. clxxvii. 282 ; see also Claiscn and Antwciler,
Ber. Deutsch. Chem. Gen. xiii. 1938.

3 Etti. Ber. Deutsch. Chem. Ges. xvii. 1821.



SALTS OF GALLIC ACID. 369

formed when dry gallic acid is saturated with ammonia, the
excess of the latter allowed to evaporate in a vacuum and the
residue crystallized from water ; it contains water of crystallization
(Kobiquet).

Calcium gallate, (C 7 H 5 O 5 ) 2 Ca + 3H 2 0, forms thin, crystalline
crusts, consisting of needles. When lime-water is added to a
solution of the acid a dirty green precipitate is produced.

Barium gallate, (C 7 H 5 O 5 ) 2 Ba + 3H 2 O, is obtained by neutra-
lizing a boiling solution of the acid with barium carbonate ; it
crystallizes in small plates, which do not readily redissolve in
water. If the freshly-prepared solution be treated with baryta-
water, a precipitate of C 7 H 2 O 5 Ba 2 -f- 5H 2 O is formed, which
rapidly becomes coloured dark blue on exposure to the air in the
moist state (Hlasiwetz).

Lead gallate. Lead acetate added to a hot solution of an
excess of the acid produces a precipitate of 2C 7 H 4 O 5 Pb -f H 2 O,
which soon changes to a lustrous, crystalline powder. If, how-
ever, an excess of the lead acetate be employed, a flocculent
precipitate is formed, which becomes yellow and crystalline on
boiling and has the formula C 7 H 2 5 Pb., (Liebig).

Iron gallate. A splendid blue precipitate is obtained when
the acid is added to a mixture of three molecules of a ferrous
salt with two molecules of a ferric salt. 1

Ethyl gallate, 2C C H 2 (OH) 3 C0 2 .C 2 H 5 + 5H 2 O, is formed when
hydrochloric acid is passed into the alcoholic solution of the acid.
It is slightly soluble in cold, readily in hot water and alcohol,
and crystallizes in pointed prisms, which lose their water at
100 . 2 It is slightly soluble in chloroform, from which it
separates in anhydrous crystals. 3 It behaves towards ferric
chloride, silver nitrate, &c., in the same manner as the free
acid, and on heating decomposes into alcohol and pyrogallol,
accompanied, however, by other products. 4 When acid sodium
carbonate is added to its aqueous solution, small crystals of
C ( ,H 2 (OH) 3 C0 2 .C 2 H 5 + C 6 H 2 (OH) 2 (ONa)CO 2 .C 2 H 5 , are formed,
which arc scarcely soluble in cold water (Ernst and Zwenger).
Lead acetate added to an aqueous solution of the ether produces
a finely divided precipitate of (C 6 H 2 (CO 2 .C 2 H 5 )O 3 ) 2 Pb 3 (Schiff).

Triethylgallic acid, C H 2 (OC 2 H 5 ) 3 CO 2 H. The ethyl ether of
this substance is obtained by heating ethyl gallate with caustic

1 Barreswill, Compt. Rend. xvii. 739.

2 Grimaux, Bull. Soc. Chim. ii. 94.

3 Ernst and Zwenger. Ann. G'hem. Pharm. clix. 28.

4 Schiff, ibid, clxiii. 209.

VOL. III. PART IV. B U



AROMATIC COMPOUNDS.



potash, ethyl iodide and alcohol ; water precipitates it from alco-
holic solution in lustrous needles, which melt at 51 and are easily
decomposed by alcoholic potash ; hydrochloric acid separates the
triethylgallic acid from the product as a crystalline precipitate.
It is slightly soluble in cold, readily in hot water, and separates
from the latter in crystals melting at 112 . 1

Triacctylgallic add, C C H 2 (OC 2 H 3 O) 3 CO,H, is prepared by
boiling gallic acid with acetyl chloride and acetic anhydride. It
is only slightly soluble in hot water, separates from alcohol in
small, lustrous needles and gives no colouration with ferric
chloride (Schiff).

Bromogallic acid, C 6 HBr(OH) 3 CO. 2 H, is obtained by triturating
equal molecules of gallic acid and bromine. 2 It separates from
the hot, aqueous solution in monoclinic crystals, resembling those of
gypsum ; its solution gives a splendid violet colouration with ferric
chloride and a fiery red, soon changing to brown with ammonia.

Dibromofjallic acid, C 6 Br 2 (OH) 3 C0 2 H + H 2 O, is formed when
an excess of bromine is employed (Grimaux). It crystallizes
from hot water in long plates or needles, melting at 150 . 3 Ferric
chloride produces a black-blue colouration ; moist silver oxide
decomposes it with formation of pyrogallol, carbon dioxide and
silver bromide, while on heating with water and potassium silver
cyanide it is reconverted into gallic acid : 4

C 6 Br 2 (OH) 3 C0 2 H + 2 AgCN + 4H 2 O =
C C H 2 (OH) 3 C0 2 H + 2CO 2 + 2NH 3 + 2AgBr.

Gallamidc, C C H 2 (OH) 3 CO.NH 2 . This compound, which is also
called gallamic acid, is formed together with gallic acid when a
solution of tannin in ammonia is rapidly boiled :

HO V /OH

\p TT /
/ i ^C 1 2\

HO/ \CO V H(\ /OH

> + NH 3 = >C 6 H / +

HO X /O ' HO/ \CO.NH,

>C 6 H 2 <
HO/ \CO.OH

HO V /OH

>C 6 H 2 /
HO/ \CO.OH.

1 Albrecht and Will, Ber. Deutseh. Ckem Ges. xvii. 2098.

2 Hlasiwetz, Ann. Chem. Pharm. cxlii. 241) ; Grimaux, Zeitschr. Chem. 1867, 431.1
2 Etti, Bar Dcutsch. Chem. Ges. xi. 1182. 4 rriwozmk. ibid. iii. G45. j



TANNIC ACID.



In order to avoid oxidation, ammonium sulphite must be
added to the solution or the operation must be conducted in
an atmosphere free from oxygen. 1 It crystallizes from hot water
in large, colourless plates and decomposes on boiling with
hydrochloric acid into gallic acid and ammonia.

2204 Diyallic acid, Tannic acid or Tannin, C C H 9 (OH) 3 CO.
OC (i H,(OH) 2 CO 2 H. The name of tannic acids has been applied
to a whole series of substances, which are weak acids, have an
astringent taste, give black-blue or dark green compounds with
salts of iron, and combine with animal skins to form leather, for
which purpose they are largely employed. These bodies do not
stand in any intimate chemical relation to each other, and the
tannic acid derived from nut-galls, the constitution of which is
known, is alone referred to here.

The nut-galls in which it occurs are of two kinds : the ordinary,
Turkish or Levant variety, which are produced by the puncture
of the gall-fly (Cynips Gallae tinctoriae) in the young shoots of
Quercus Insitanica, var. infectoria and probably some other
species, and the Chinese or Japanese nut-galls, which are formed
by a plant-louse (Aphis chinensis) on the leaf-stalks and young
twigs of Rhus scmialata. In addition to these modes of occur-
rence, tannic acid has hitherto only been observed in sumach,
the leaves and twigs of Rlius coriarict?

Stenhouse, who found that tannic acid from sumach is con-
verted into gallic acid by dilute sulphuric acid, says : " Sumach,
therefore, appears to approach the nature of nut-galls more
closely than any of the other astringent substances. This fact
is well known to Turkey-red dyers, who have long successfully
employed sumach as a substitute for galls."

In order to prepare tannin, the method of Pelouze was formerly
employed, according to which the nut-galls are extracted with
ordinary ether, containing both alcohol and water. The
solution thus obtained separates into two layers, the upper of
which consists of water and ether containing gallic acid and a
little tannin, while the syrupy lower layer is a solution of tannin
in water and ether and is evaporated to dryness.

A mixture of 12 parts of ether and 3 parts of alcohol is now
used for the extraction, 12 parts of water being added to the
extract and the alcohol and ether removed by distillation. The

1 Knop, Jahrcsbcr. Chem. 1854, 431 ; Schiff and Pons, Ber. Deutsch. Chem.
Ues. xv. 2591 ; xviii. 487 ; Etti, ibid. xvii. 1820.

2 Stenhouse, Chem. Soc. Mem. i. 137 ; Lowe, Fres. Zeitschr. xii. 128.

JJ B 2



372 AROMATIC COMPOUNDS.

residual aqueous solution is then filtered and evaporated, the
crude tannin being further purified by solution in water and
treatment with animal charcoal. 1

Pure tannin may also be obtained by extracting nut-galls
with anhydrous ether, to which 5 per cent, of alcohol has been
added (Schiff).

While the tannin prepared by Pelouze's method contains more
or less grape sugar or a substance yielding glucose, this is not
the case with that obtained by the more modern process, and
hence it follows that tannin is not a glucoside, but that the older
specimens contained, as was suggested by Rochleder, an admix-
ture of sugar or a glucoside which was brought into solution by
the water present. 2

Schiff, as already mentioned, found that gallic acid is converted
into tannic acid when it is heated with phosphorus oxychloride
or when its solution is evaporated with arsenic acid. According
to Freda, the product obtained by the latter method gives all
the characteristic reactions of tannin, but is nothing more than
gallic acid containing arsenic acid, 3 while Schiff has shown that
this is not the case, but that arsenic acid adheres to the tannin
so obstinately that it cannot be removed without a simultaneous
conversion of a portion of the latter into gallic acid. 4 The
constitution of tannin or digallic acid is expressed by the
following formula :

H(X HO



HO, / O /

HO/ ! \CO.OH.

This explains in a simple manner its conversion into gallic acid
by the assumption of water, its decomposition into gallamide and
gallic acid by the action of ammonia and the formation of
a penta-acetyl-derivative.

The fact that when monobromocatechuic acid is heated
with potassium gallate and alcohol, a substance is formed

1 Biedermann, Ber. Eniw. Chem. 2nd. ; 2 Halfte, p. 456.

3 Schiff, Ann. Chem. Pharm. clxx. 75.
8 Ber. Deutsch. Chem. Oes. xii. 1576.

4 Ibid. xiii. 454.



PROPERTIES OF TANNIN. 373

which gives all the reactions of tannin, is also in favour of this
formula : l

C 6 H 2 (OH) 3 CO.OK + BrC 6 H 2 (OH) 2 CO.OH =
C 6 H 2 (OH) 3 CO.O.C 6 H 2 (OH) 2 CO.OH + KBr.

Properties. Tannin is a colourless, amorphous mass, which is
left on the evaporation of its solution in brittle, vitreous masses,
which become coloured yellow in the light, even when exposed
in closed vessels. It reddens litmus and has a very strong
astringent taste, is readily soluble in water, less so in absolute
alcohol, and almost insoluble in absolute ether. Finely-powdered
tannin coagulates in ether which contains water, and then de-
liquesces, so that it can be employed to detect the presence of
water in ether. If water be slowly dropped into the vessel
containing the thick solution covered by ether, a point is
attained at which three layers are formed. 2 This occurs when
100 ccms. of water and 150 ccms. of ether are present to 100
gnus, of tannin ; the lowest layer contains most tannic acid, the
middle layer some tannic acid and a large amount of water
while the upper layer consists almost entirely of ether, but
contains a little tannic acid. 3

Tannin is insoluble in carbon disulphide, chlorofofm, petroleum
ether, benzene, &c. Its aqueous solution gives a black-blue
colouration and precipitate with ferric salts, a partial reduction
taking place (Wackenroder) ; ferrous sulphate produces in a
concentrated solution a white, gelatinous precipitate which
becomes coloured blue in the air.

When tannin is heated it darkens at 150 160, and at 215
decomposes into water, carbon dioxide and pyrogallol, which
volatilize, while metagallic acid or melangallic acid is left
behind; this substance alone is formed when tannic acid is
rapidly heated to 250, and is a black, amorphous, tasteless
mass. Tannin very readily undergoes oxidation; strongly
ozonized air produces complete combustion, oxalic acid being
formed as an intermediate product (Schonbein) ; it reduces the
salts of copper, silver, mercury, gold, &c. In alkaline solution
it rapidly absorbs oxygen, the liquid becoming coloured dark.
Tannin is precipitated from aqueous solution by dilute hydro-
chloric acid, sulphuric acid, common salt, potassium chloride,

1 Hunt, Chem. News, lii. 49.

2 Bollcy, Ann. Chem. Pharm. cxv. 63.

3 Luboldt, Jahrcsb. Chem. 1859, 296.



374 AROMATIC COMPOUNDS.



potassium acetate and other salts, but not by nitric acid or
sodium sulphate. Animal skin removes it from solution com-
pletely ; it precipitates gelatine solution, egg albumen, alkaloids
and other substances.

The Tannates. Tannin decomposes carbonates and is a mono-
basic acid, the salts of which are amorphous and difficult to
prepare pure. Many of them are insoluble precipitates, such as
the tannates of lead, copper, tin, and antimony, and these may
be used for the quantitative estimation of the acid.

Tannin, or rather the material containing it, is employed in
medicine, dyeing, the manufacture of inks, the clarification of
beer and wine, &c. It is not adapted for use as a tanning
agent.

Penta-acetyltannin, C 14 H 5 (C 2 H 3 O) 5 O 9 , is obtained by boiling
tannin with acetic anhydride for one hour ; it is insoluble in
water and separates from boiling alcohol in white spherical or
warty aggregates of crystals, which melt at 137. Its solution
is precipitated by lead acetate, but is not coloured by ferric
chloride (Schiff).

Kino'in, C 14 H 12 O 6 , was discovered byEtti in Mnlabar kino, the
dried sap of Ptcrocarpus Marsnpium (p. 351). It crystallizes in
prisms, which are slightly soluble in cold, readily in hot water
and alcohol ; its solution is coloured red by ferric chloride. On
heating to 120 with hydrochloric acid, it decomposes into methyl
chloride, catechol and gallic acid :

C 14 H 12 6 + H 2 + HC1 = CH 3 C1 + C 6 H 6 O 2 + C 7 H 6 5 .

It is therefore gaily Icatechol methyl ether, and probably has
the following constitution : "

HO^ ,OH

HO/ :N \CO.OC 6 H 4 .OCH 3 .

Kino-red, C 28 H 22 O n , is an astringent substance which also
occurs in kino, and is formed by heating kinom to 120 130.
It is a red, resinous substance, which is slightly soluble in water,
readily in alcohol and alkalis, gives a dirty-green colouration
with ferric chloride, and precipitates gelatine solution. On



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