MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 
343 
the whole, forming a dark brown solution, while the undissolved residue was entirely 
soluble in ether. The alcoholic extract of jalap, therefore, contains only one resin, 
which is soluble in ether, two-thirds or upwards of the whole consisting of one or 
more non-resinous substances soluble in boiling water. It is that portion of these 
non-resinous substances which ether does not take up, that has hitherto been con- 
sidered as the second resin of jalap. This explanation reconciles my results with 
those of Gassicourt, as given in Dr. Thomson’s Organic Chemistry ; but Leopold 
Gmelin states not merely that the alcoholic extract, but that this extract after boiling 
in water consists of two resins, one soluble and one insoluble in ether. I am inclined 
to think, however, that, in transcribing his experiments, Gmelin has written what 
Gassicourt ought to have done rather than what he did. 
The solution of the resin in ether was evaporated and heated at 230° Fahr. till it 
became dry and solid. It was then reduced to powder and heated for several days 
to 200° Fahr. 
A. 1 2*75 grs. gave C = 26T9, and II = 9’467 grs. 
Of another portion dried in a thin film, 
B. 12 - 22 grs. gave H = 8-9/3, the carbonic acid being lost. 
C. 10-49 grs. gave C = 21*79, and id =8-107 grs. 
D. 9"328 grs. gave C = 19"47, and H = 7*056 grs. 
These are equivalent to 
A. 
B. C. 
D. 
Carbon 56*80 
57*44 
57*71 
Hydrogen 8- 24 
8-16 8*58 
8-40 
Oxygen 34 '96 
34-08 
33-89 
100 
100 
100 
I believe that the deficiency of carbon and of hydrogen in the analyses A. and B. 
is due to the employment of sand of too high a temperature while pumping out the 
moisture, and that C. and D. represent more nearly the true constitution of the resin. 
These agree with the formula C 40 H 34 0 18 , which gives 
Per cent. 
40 Carbon = 3057*480 57*88 
34 Hydrogen = 424-306 8'03 
18 Oxygen = 1800*000 34*09 
5281*786 100 
This constitution for the resin of jalap being remarkable not merely for the great 
number of equivalents of oxygen it indicates, but also as presenting the only example 
we have yet met with (with the exception of the resin of scammony) in which the 
number of equivalents of hydrogen is decidedly greater than thirty-two, I was 
anxious to submit it to still further verification : I therefore distilled off the greater 
portion of the ether from the ethereal solution, and digested the resin a second time 
