14 
GLEANINGS IN SCIENCE. 
3 Phenictn, or Purple Indigo, is obtained by suddenly diluting the sulphuric 
acid which has begun to dissolve Indigo. It separates as an insoluble powder, 
which M ben filtered and washed, is soluble in pure boiling water, and may lie pro- 
cured as a precipitate again by the addition of any neutral salt. Phenicin is sup- 
posed bv Berzelius to lie an intermediate state between soluble and insoluble In. 
digo ; but Crum a serts that 100 parts of Indigo will yield 120 of I’henicin. 
The Indigo of commerce most probably ranks under one of the two latter deno- 
minations, or perhaps both of them ; for there can be little doubt that some new 
combination of elements takes pl.,ce in the sublimation of the “ pure" or " crystal, 
lized Indigo,” since, with the utmost care, not more than one fil th of the weight 
of crystals can be procured ; and, during their formation, first, aqueous vapour, 
then gas is extricated ; and a red coloured oil ; and a large residue of charcoal is 
left behind ; whereas the crystals, once formed, are vol tili/.ahle without any loss 
or carbonaceous residue. As the crystallized state, and the resistance to destruc- 
tive agencies at an elevated temperature, are th sure signs of a definite, and gene- 
rally of a simple atomic composition, we should expect to find tolerable accordance 
in the analyses of the crystals of Indigo. I have only been able to find two 
made by different chemists, but they are greatly at variance with one another*. 
Pure Indigo, analyzed by Thompson by Crum. 
Consists of Oxygen, 46 154 12.60 
Carbon, 40 384 __ 73 22 
Azote, 13.462 11.26 
Hydrogen, 2 92 
100 . 100 . 
The other varieties are stated by Crum to lie thus composed : 
Cerulin. Phenicin. 
Oxygen, 29 0 __ „ „ 21.6 
Carbon, ... ... 57.8 „„ ... „ ... 64.9 
Azote, ™ 8.4 ... 9.5 
Hydrogen, 4.8 q'q 
. . 10 °- 100 . 
If tbe composition given by Thompson be correct, Indigo ought to be a remarks- 
bly easy substance to analyze ; since it would merely Ik- necessary to submit it to 
a destructive beat, —to determine the proportion of carbonic acid, carbonic oxvde, 
and azote,— and to weigh the surplus carbon. The quantity of oxygen in'the 
analyses of Mr. Crum will be proved hereafter, I think, to be too small 
From the almost total insolubility of pure Indigo, it becomes a very simple 
matter to separate the foreign ingredients which are found with it, and come- 
quently to obtain it m a state of purity. All that is necessary is to boil it for a 
sufficient time. 3 
First. In pure water; which removes yellow extract, green matter &c 
Secondlv. In alcohol, which carries off red colouring matter, and resin 
magS & c n dl ' Ute " ,UriatiU a ‘ id > whitU UP lime, of Iron, and 
th/pre^^ t o^whiTh l caivon^y'be V det^S > 'iw S ^mnh!i? C ' ay ’ . a1un y n ? nr ffyP sura ’ 
Chevreiil only obtained 4o per cent, of ,, ™ r V; > ears, ior 
digo, Bergman found 47,-Brmide states It ^tlo pel ^-\v 
mens which 1 analyzed in Calcutta, one contained 7 r , ,l„, “ erea ® *" tlvo s P et '- 
of pure blue; neither were these the ^ 
Deoxydxzing substances, such as the sulphurete, protoxvd^of i™ v 
the sulphites, &c. have the power of depriving iK S a nlTof^. P ^U,^ 
whence it becomes again soluble in water or ilkalin/hJ! P 1 . f u * ox yg ea ’ 
of regaining its colour the moment it '£- V T 
that the dyers are enabled to prepare a solution for it, * ^ en ' r 15 thus 
Sion They are said to 
^^ ■, t , m a 1 , 1 vw ,, l ll |. Indigo, in^L p^ortions^^VTh; 
? Zt' Ox. 14.3, Caib. 
turn -bo. wese "umbers may require a little altera- 
