ALCOHOL-TEST FOR THE PURITY OF CASTOR OIL. 223 
ponding diminution of volume. I presume, however, that 
the statement of the Edinburgh college is intended to ap- 
ply to the amber colored East India croton oil. This oil, 
when mixed with an equal volume of alcohol, does not 
form a transparent homogeneous mixture until [a gentle 
heat is applied, and, on standing, the mixture separates into 
two strata — thus far agreeing with the statement of the 
Edinburgh college; but the oilmen separation, is found to 
have suffered a slight augmentation in bulk, and the alco- 
hol a corresponding diminution (See Expt. 2.) 
In the degree of its solubility in alcohol, the pale or amber 
colored East India croton oil agrees with jatropha oil, and 
Mr. Redwood has suggested that it is perhaps mixed with 
the latter oil. 
It is obvious, from what has been now stated, that if En- 
glish expressed croton oil were adulterated with castor oil, 
alcohol would be useless as a test to detect the fraud. 
Leopold Gmelin states, in his Handbuch d, Chemie, vol. 
it., page 45S, 1829, on the authority of Stoltze, that ben- 
zoic acid promotes the solubility of castor oil in spirit con- 
taining seventy-five per cent of alcohol ; and I have been 
informed that camphor is equally efficacious. I have not, 
however, verified either of these statements. 
III. Castor and croton oils enable other fixed oils to dis- 
solve in alcohol. This is a very interesting and important 
fact; and in illustration of it the following experiments are 
adduced. I may premise, however, that I have been ac- 
customed for several years to demonstrate the fact in the 
lecture room. 
If rectified spirit be substituted for alcohol a gentle heat 
is usually required to render the mixture transparent and 
homogeneous; and on standing the liquid, when cold, se- 
parates into two strata, an upper spirituous one holding oil 
in solution, and an inferior oily one retaining spirit in so- 
lution. The relative bulks of the two liquids are, however, 
very different to those of the spirit and oil originally 
mixed. 
