MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 349 
me, either that this constant was to be looked for in the expression for a resinous 
substance, or the precautions necessary to be adopted in the extraction and drying 
of the resins themselves. 
The following analyses not only rectify the formula, but show also the cause to which 
the deduction of an erroneous formula from the previous analyses is to be ascribed. 
Retin-asphalt was treated with three successive portions of alcohol, being boiled 
with the last portion till everything soluble appeared to be taken up. 
The resin left by evaporating each of these three portions in a thin film, and heat- 
ing it at 200° Fahr. for twelve hours, was analysed separately. It was in the state of 
a light brown powder, or of a dark brown film. 
Of one of these portions when burned in the air, 
5*774 grs. left 0*04 grs. of gray ash = 0*7 per cent. 
Of another 2*417 grs. left 0*021 grs. = 0*86 per cent., giving as a mean 0*78 per cent, 
of earthy matter in the resin after solution in the alcohol, 
A. of the first portion 5*78 grs (5*735 grs. pure resin) gave 
C = 15*74, and H = 4*571 grs. 
B. Of the second 7'624 grs. (7*565 grs. pure resin) gave 
C = 20*865, and H = 5*995 grs. 
C. Of the third 5*88 grs. (5*834 grs. pure resin) gave 
C = 16*01, and H = 4*56 grs. 
B. Of a mixture of these, heated till the resin began to melt and cohere, being when 
cold very dark brown and porous, 7*13 grs. (7*074 grs. pure resin) gave 
C = 19*51, and H = 5*445 grs. 
E. Of the same fused at the lowest possible temperature for three hours, 7*805 grs. 
(7*744 grs. pure resin) gave 
C = 21*87, and H = 6*063 grs. 
These results gave for the various portions the following constitution per cent. : 
Dried for twelve hours at 200 
° Fahr. 
Afterwards heated to 
incipient fusion. 
D. 
Kept at melting point 
for three hours. 
E. 
A. 
B. 
c. 
Carbon 75 '89 
76-26 
75*88 
76*26 
78*08 
Hydrogen 8*85 
8-80 
8-68 
8*55 
8*70 
Oxygen 15*26 
14-94 
15-44 
15*19 
13*22 
100 
100 
100 
100 
100 
The formula C 40 H 27 O s , gives 
Per cent. 
40 Carbon = 3057-48 76*53 
2 7 Hydrogen = 336*95 8*44 
6 Oxygen = 600*00 15*00 
3994*43 
100 
