Lassaigne on Pyro-citric Acid. 423 
in the receiver. Towards the end of the calcination a brownish 
vapour is seen to form, and there remains in the bottom of the 
retort a light very brilliant charcoal. 
The product contained in the receiver consists of two different 
liquids. One, of an amber-yellow colour, and an oily aspect, 
occupies the lower part; another, colourless and liquid like water, 
of a very decided acid taste, floats above. After separating them 
from one another, we perceive that the first has a very strong bi- 
tuminous odour, and an acid and acrid taste; that it reddens 
powerfully the tincture of litmus, but that it may be deprived 
almost entirely of that acidity by agitation with water, in which 
it divides itself into globules, which soon fall to the bottom of 
the vessel, and are not long in uniting into one mass, in the 
manner of oils heavier than water. : 
In this. state it possesses some of the properties of these 
substances; it is soluble in alcohol, ether, and the caustic 
alkalis. However, it does not long continue thus; it be- 
comes acid, and sometimes even it is observed to deposit, at the 
end of some days, white crystals, which haye a very strong 
acidity; if we then agitate it anew with water, it dissolves in a 
great measure, and abandons a yellow or brownish pitchy matter, 
of a very obvious empyreumatic smell, and which has much ana- 
logy with the oil obtained in the distillation of other vegetable 
matters. ‘The same effect takes place when we keep it under 
water; it diminishes gradually in volume, the water acquires a 
sour taste, anda thick oil remains at the bottom of the vessel. 
This liquid may be regarded as a combination (of little perma- 
nence indeed) of the peculiar acid with the oil formed in similar 
circumstances. 
As to the liquid and colourless portion which floated over 
this oil, it was ascertained to contain no citric acid carried over, 
nor acetic acid ; first, because on saturating it with carbon- 
ate of lime, a soluble calcareous salt was obtained; and, 
secondly, because this salt, treated with sulphuric acid, evolved 
no odour of acetic acid. 
From this calcareous salt the lime was separated by oxalic 
acid ; or the salt itself was decomposed with acetate of lead, 
and the precipitate treated with sulphuretted hydrogen. By these 
two processes, this new acid was separated in a state of purity. 
Properties of the Pyro-citric Acid. 
This acid is white, inodorous, of a strongly acid taste. It is 
‘ difficult to make it crystallize in a regular manner, but it is 
usually presented in a white mass, formed by the interlacement 
of very fine small needles. Projected on a hot body it melts, 
is converted into white very pungent vapours, and leaves some 
traces of carbon, When heated in a retort, it affords an oily- 
looking acid, and yellowish liquid, and is partially decomposed. 
