1155
CATECHU ACACIA.
a p a ^ C Catechu. Of lliis I have met with two kinds:—
<e Pie ^ Catechu in broken square cakes; Bengal Catechu of Sir II. Davy ? ( Cachoufin,! .?{ Parallelipipede , Gnibourt; Cachou en maniere d’ecorce d’arbre, A. Jussieu)—Iin r ,. ls to be identical with Dr. Royle’s specimens of catechu, which he saw preparedlou„ 1:1 ^ r [ ,m the Acacia Catechu. It occurs in square cakes, usually about two inches^ r ok t(V ° * nc b es broad, and one in thickness. Frequently these cakes are irregularly"ate/ 1 ’ S -> * s difficult 1° trace their angular character. They are heavier than
tlafij ' Externally their colour is dark-brown, or blackish; internally we observe'Erk^ ^ n< ' hghter layers, disposed in a schistose manner, like the bark of a tree. TheA ( |„ er Eyers are brown and somewhat shiny, the lighter ones are dull reddish-white.Cop:. ° ct,0l > of one part of this catechu and twelve parts of water lets fall, on cooling, aj s whitish precipitate (catechuic acid).
tlii s r a ^ eor Whitish Catechu in irregular lumps. (Cachou blanc, Guibourt)—I receivedin ] <lni Bombay, under the name of Katha suffaid (i. e. pale or white catechu). It is^tal r S) ^hidi vary in size from that of a walnut to that of a small apple. The ge-ana . „ ortn >s rounded or oval, and somewhat flattened, the surface being very uneven,, a dark or blackish-brown colour. Internally this variety is dull, and of a very
of
^ ^ Co] v ‘. ’’ 11 Wiwui* AiJiviuaiij — 'fj
ted ti 10Ur ‘ Guibourt says, it is almost white ; but it has a pale-yellowish or brownish
Its , is bitter, astringent, and sweetish, with a smoky flavour. Hence,
V> *be dark colour externally is derived from the masses being dried, or exposede s nioke of a fire.
'the,. Cr
(fy.^G’osnroN.—Two kinds of Catechu were analyzed by Sir H. Davy <i , )e ' C'rcins. for 1803, p. Q33). In 1833, Buchner discovered in catechuc 4/ lar ac hl> which has been denominated Catechuic acid ( Pharm.al - Blatt.fiir 1833, 629).
n "in
j^'d'ar ..
/'"'"'age
su uble matter (chiefly sand and lime)
extractive
GatechuCatechuit
Bombay.
Bengal.
54o
485
340
36 5
6*5
80
5 0
70
1000
1000
1.
2, p 1lec huic Acid. —This has been already noticed (see p. 1027-8).
' s ce p Acid. The general properties of this acid have also been before described^a'iar •''—^ * s diis substance which renders catechu so valuable to the tanner. The1 v - °' l be tannic acid of catechu have been studied by Berzelius (Traite de Chim.
16 e *"Hi ’ • * n conse( l llence °f hie subsequent discovery of catechuic acid they require
v ? f y The tannic acid of catechu is easily soluble in water and alcohol, but
a ' r . I^ ht y so in ether. The aqueous solution becomes coloured by exposure to thecombinations with acids are very soluble. Alkalies do not precipitate it.
^chn^ 10 -'^ Characteristics. —The brown, filtered, decoction of ca-j c af ec ., re dd en s litmus, yields a blackish-green colour and precipitate^ r °' v ni \ te an< ^ ^ anna ^ e °f iron) with the femiginous salts, and adie C0( /d-whit e one with acetate of lead. A solution of gelatine rendersc °lo Ur decoction turbid (tannate of gelatine ). Alkalies deepen thedie (j ot the decoction, but cause no precipitate. Sulphuric acid rendersT], e ?^ti°n slightly turbid.
tec hu i n / er ed decoction of several kinds of catechu (especially pale ca-
cold
Th £" , J >r °ken square cakes) deposits, on cooling, catechuic acid.dec 0ln ec ° c tion of dark-brown catechu, in circular flat cakes, when cc^Rit - C of starch) on the addition of a solution of iodine.
Ca t ecV Y -; The Edinburgh College states, that “ the finest qualities [of/'doirn,! Deld to sulphuric ether 53, and the lowest qualities28 percent.4S a kst of at This proceeding, however, is not to be relied on
the astringency of catechu, which can only be determined in the