MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 
363 
C 40 H 28 0 7 , I think it more safe to represent the resin of galbanum by the formula 
r h o * 
c 40 n 27 '-'7 ’ 
C 40 H 27 °7 g iveS 
'Carbon 74*67 
< Hydrogen 8*23 
Oxygen 17*00 
100 
The carbon by calculation is a third per cent, more than was found by experi- 
ment. But this is the direction in which errors of experiment in organic analyses 
are generally found, and a slight deficiency in the carbon may be expected in the 
case of substances which so readily fuse and give off volatile matter as this and many 
other of the resins. In pumping out the hygrometric moisture, some volatile vapour 
may also be exhausted. 
3. When heated over the lamp in a platinum capsule to a temperature of about 
300° Fahr., the resin above analysed gave off white fumes, and after two hours had 
lost nearly 10 per cent, of its weight, having become of a beautiful brownish-red 
colour. It still softened at 212° Fahr., and retained a little of its original odour. In 
this state 7‘11 grs. = 7‘086 pure resin, gave C = 19*02, and H = 5*18, or per cent., 
Carbon 74*22 40 atoms. 
Hydrogen 8*12 26*7 atoms. 
Oxygen 17*66 7’27 atoms. 
100 
In this result we see an apparent approximation to the formula C 40 H 26 0 7 , the 
hydrogen decreasing, while the oxygen appears to increase. 
In the former of this series of papers (Part IV.), I gave the analysis of the resins 
of ammoniac, opoponax, and assafoetida, which together with those of sagapenum and 
galbanum, constitute the group of foetid resins of some chemists'}'. The odour of 
the last four of these resins is very similar, though that of assafoetida is the most 
powerful and disagreeable. We might anticipate, therefore, some resemblance in 
constitution among these resins, since they exhibit in common this very striking pro- 
perty. In the irrational formulae above obtained, however, we do not recognize any 
close resemblance, either in the proportions of hydrogen or of oxygen which they 
contain. Thus the 
Resin of ammoniac = C 40 h 25 o 9 
Resin of opoponax = C 40 H 25 0 14 
Resin of assafoetida = C 40 H 26 O 10 
Resin of galbanum = C 40 H 27 0 7 
Resin of sagapenum = C 40 H 29 0 9 . 
f Thomson’s Organic Chemistry (1838), p. 567. 
3 a 2 
* See under elemi resin B. 
