MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 
347 
description of a substance, said to occur in large quantities as a mineral deposit at 
San Juan de Berengela, in South America. This fossil body is a true resin of a brown 
colour, giving with cold alcohol a brown solution, having a peculiar unpleasant 
odour, and a disagreeable exceedingly bitter taste. 
In the same paper I inserted also two analyses of this substance, which gave per 
1 . 
2. 
The formula 
The formula 
c 40 H 31 0 8 gives 
c 41 H 31 0 8 gives 
Carbon 72*47 
72-34 
72-04 
72-53 
Hydrogen 9*20 
9-36 
9*12 
8-93 
Oxygen 18-33 
18-30 
18-84 
18-54 
100 
100 
100 
100 
The analytical results, when compared with the calculated numbers, show an ex- 
cess of carbon above what is required by the formula containing C 40 . Being, at the 
time when these analyses were made, unaware of the apparently universal prevalence 
of this quantity C 40 , in the formulae for the resins, which the present investigation 
seems to exhibit, I was by this excess led to adopt in preference the second formula 
containing C 41 . On deducing for the resin of labdanum, however, as shown in the pre- 
ceding section, a formula approaching very closely to that previously assigned to the 
Berengela resin, I was induced to return to the latter substance, and by a repetition of 
the analyses to test my previous results. 
1. A small portion of the alcoholic solution was therefore evaporated, and the resin in 
the form of a thin film kept at a temperature of 150° Fahr. for twelve hours, and af- 
terwards at 212° for two hours. The resin when cold was brittle, but the particles 
cohered slightly after standing for some time. Burned in the air it left 020 per cent, 
of brown ash. 
A. 10‘3 grs. gave C = 27*26, and IT = 9*41 grs. 
B. 8*17 grs. gave H = 9’45 grs., or per cent., 
A. 
Carbon 73*16 
Hydrogen 9-43 
Oxygen 17*41 
100 
B. 
40 atoms 
9*45 31*6 atoms 
7*3 atoms. 
2. In the result A. the carbon is still more in excess than in the previously published 
analyses, and as the number of atoms seemed to indicate the formula C 40 H 31 0 7 , I 
evaporated another portion, and exposed it in a still thinner film for twenty hours to 
a temperature, until the last two hours, not exceeding 200° Fahr. The resin thus 
obtained retained its natural pale colour and peculiar odour, melted at 212° Fahr., 
was brittle when cold, and when broken up its particles showed little tendency to 
cohere. 
6’667 grs. (6*654 grs. pure resin) gave C = 17*8, and H = 5’62 grains. 
2 y 2 
