364 
MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 
Still it appears to me exceedingly probable, that in the rational formulae for this 
and similar groups of resins exhibiting striking sensible properties, common to all, 
we may hereafter find that connexion in constitution which the irrational formulae 
do not exhibit, and the absence of such connexion is not without its weight in favour 
of the opinion, that the resins in general are not mere oxides of a carbo-hydrogen 
radical, but are in many cases at least made up of two or more compound radicals. 
Into the consideration or development of this view, I do not propose to enter, until, 
in the sequel of the present and in some subsequent papers, I shall have brought for- 
ward facts and analytical results by which it may be better sustained. 
XIX. Euphorbium Resin. 
This resin occurs in commerce in the form of tears, generally enveloping small 
twigs or thorns of the shrub from which it had exuded. It is largely mixed with 
seeds and spines, and sometimes with at least three-fourths of its weight of clay and 
other earthy matters. It is of a pale-yellow colour, and is distinguished by its pecu- 
liarly hot and acrid taste, and its stimulating action on the organs of smell and even 
externally upon the skin. 
When digested in cold alcohol (0*8) a pale-yellow solution is obtained, which by 
evaporation gives a yellow resin. After being treated with cold alcohol as long as 
anything is taken up, a large insoluble residue remains. Boiled in alcohol, this 
residue yields a solution, from which, on cooling, a white resinous substance is depo- 
sited in a crystalline form. This sparingly soluble resin has been examined and 
analysed by Rose. To the results of these analyses I shall presently have occasion 
to advert. 
I. Resin A. of Euphorbium ( readily soluble in cold alcohol). 
1 . When the native tears of euphorbium are digested in cold alcohol, a pale-yellow 
solution is obtained, and from this by evaporation, a brownish -yellow resin, readily 
fusing at 212°. If this resin be treated with boiling water, the first portion of the 
liquid employed acquires a pale-yellow tinge, and a small quantity of oil is removed. 
By subsequent washing nothing further appears to be taken up by the water. Sepa- 
rated from the water, the resin is pale-yellow and opake, like common Burgundy 
pitch, and requires long drying at 212° in a thin film to render it perfectly dry and 
transparent. It is now less fusible, though it still becomes semifluid at 212°, and 
when cold is brittle, in mass of a brownish red colour, and in fragments exceedingly 
electric. 
In this state, when burned in the air, 5*605 grs. left 0*075, or 1*34 per cent, of ash; 
and with oxide of copper, 
A. 9*1 grs. (8*978 grs. pure resin) gave C = 24*39, and H = 7*9 1 grs. 
B. 7*19 grs. (7'094 grs. pure resin) gave C = 19*29, and H = 6*3 grs. 
