416 On the State of the Manufaelure 
is seen to pervade the surface of the indigo (which becomes a 
erust). It may be detached by means of a delicate spatula. The 
odour at first is unpleasant, but it becomes more mild and some- 
what like that of sweet wort; or it may be obtained by heating 
indigo on a metallic plate. I have seen similar crystals on 
the sides of the indigo vat, from whence it seemed to have su- 
blimed. 
I find that indigogene is readily soluble in sulphuric acid and 
also in nitric acid, communicating to each a green colour. It is 
not soluble in muriatic acid, nor in a solution of boiling caustic 
potassa, nor in ammonia. 
It is soluble in olive oil, even when cold, and in naphtha and 
¢ajeput oil with the assistance of heat. Ammonia added to the 
solution in oil of olives does not materially evolve the substance, 
but from naphtha and cajeput oil it is disengaged unaltered. 
Indigogene is soluble in hot alcohol and sulphuric ether, It 
is instantly dissolved by an alcoholic solution of camphor being 
increased by heat, but is not so soluble in soap dissolved by spi- 
rit, communicating to these a blue tinge. 
Indigogene when projected on melted nitrate of potassa de- 
tonates, and slightly explodes when mixed with oxymuriate 
putassa on the contact of sulphuric acid. 
Indigogene does not combine with mercury by simple triture, 
but forms an amalgam aided by heat. Before the blowpipe 
when in a platina spoon it scintillates and inflames, a violet va- 
pour evolves, and a blue shade crowns the surface of platina.— 
By percussion with oxymuriate potassa it fulminates with flame. 
The effects of various reagents may form the subyect of a future 
paper. 
I am, &e. 4 
Liverpool, June 8, 1816. J. Murray. 
LXXXVII. On the State of the Manufacture of Sugar in France. 
By M. le Comte Cuaprat, 
[Concluded from p. 339.] 
Tux boiler into which the cleared juice falls should be about 
eight feet long, five and a half wide, and twenty-two inches deep. 
As soon as the bottom of this boiler is covered with the liquid, 
the fire is lighted, and the heat raised to ebullition as quick as 
sible. The instant the liquor begins to boil, sulphuric acid, 
diluted with twenty parts of water, is poured into it, in the pro- | 
portion of a tenth part of the lime employed; the whole _ " 
e . 
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