TRANSACTIONS OF THE SECTIONS. 51 
product. Its peculiat taste, acrid and sweet at the same time, reminding us of the 
taste of liquorice, is characteristic. With sulphuric acid it takes a red colour; 
distilled with bichromate of potash and sulphuric acid it yields salicylous acid. It 
is more soluble in water and alcohol than salicine. It is curious also to note that 
in this combination the salicine has lost its bitter taste, which renders it probable 
that populine is in reality a compound of benzoic acid, sugar, and saligenine; for, 
when boiled with dilute sulphuric acid, it breaks up into benzoic acid, sugar, and 
saliretine (saligenine minus 2 equivs. of water) :— 
C“H® O+ Saligenine. 
CY HY O Sugar. 
C™“H® O* Benzoic acid. 
C*° H* 01 Populine. 
As soon as the sugar is set free, it takes up 4 equivs. of water and passes into grape- 
ugar (C!? HO), 
he molecule of populine is therefore a very complex one. And these kinds of 
compounds may, perhaps, be compared to the combinations of two or more salts in 
mineral chemistry, for instance to alwm, if we compare the sulphate of alumina to 
the benzoic acid, the sulphate of potash to the saligenine, and the 24 equivalents of 
water to the sugar. 
But I have also found that citric acid and tartaric acid, when taken in equivalent 
proportions, dissolved in water, and the solution evaporated, enter into cheinical 
combination. It is well known that these acids crystallize in two different systems, 
the forms of which are incompatible, and by evaporating a mixture of them we 
should obtain two kinds of crystals if no combination took place. But I find that 
they combine and produce one kind of crystal only, namely, long prismatic needles, 
and when one of these crystals is taken and analysed, it is found to be composed of 
eitric and tartaric acids. ; 
This combination of citric and tartaric acids is probably only one example of 
a new class of organic compounds, similar in some respects to populine, which 
remains to be studied. Already Prof. Williamson has shown that the different 
acetones may he made to combine so as to produce complex acetones. Thus when 
valerate and acetate of lime are distilled together in equivalent proportions, we 
obtain acetovalerone, a compound of acetone and valerone, and so on for the others. 
It is highly probable from what precedes that other organic acids besides benzoic 
acid may be made to combine with salicine; likewise that other bitter principles 
analogous to salicine may be combined with organic acids to produce substances 
similar to populine, 
On the Existence of Aniline in certain Fungi which become Blue in contact with 
the Air, Fc. By T. L. Pureson, WB., Ph.D., F.OS. Se. 
Two years ago I published in Brussels a memoir upon the Boleti which become 
blue when cut with a knife, and upon the formation of colouring matters in fungi*. 
In this paper I called attention to a remarkable set of reactions occurring in nature 
when one substance causes atmospheric oxygen to assume the state of ozone and to 
act upon another substance in contact with the first, a fact originally pointed out 
by Prof. Scheenbein. In this paper also I endeavoured to show that the production 
of the blue colour observed when Boletus cyanescens, Boletus luridus, &c. are cut 
with a knife and exposed to the air, is owing to the existence of aniline in the sap 
of these fungi. 
Nothing is easier than to extract the principle to which these Boleti owe their 
remarkable property of taking a deep, though fugitive, blue colour when their in- 
ternal tissue is put in contact with the air. But it is not easy to obtain it perfectly 
* Sur les Bolets bleuissants : étude sur la formation de principes colorants chez plusieurs 
Champignons (Journal de Médecine et de Pharmacologie, Bruxelles, Mars et Avril 1860). 
See also ‘Comptes Rendus de l’ Acad. des Sciences,’ Paris, 1860, 2i#me semestre. Also my 
prize memoir, ‘‘ La Force Catalytique : études sur les phénoménes de contact,” to which the 
atch Society of Science awarded their Gold Medal, Haarlem, 1858. 
4* 
