ALCOHOL-TEST FOR THE PURITY OP CASTOR OIL. 221 
transparent mixture was obtained ; and no separation took 
place on standing for several weeks. 
In the case of the amber colored East India croton oil a 
separation takes place on standing, as already stated (see 
Expt. 2.) Here then the solubility of croton oil in alcohol 
resembles that of castor oil, in the circumstance that both 
oils obtained by expression in London are more soluble in 
alcohol than the corresponding oils imported from the East 
Indies. 
On what does this difference depend ? Does it arise from 
the differences in the qualities of seeds pressed, or from 
differences in the mode of preparing the oil? On these 
points nothing definite can be stated. In the case of castor 
oil, the mode of preparation adopted in India is different to 
that followed in England. Here the oil is expressed in a 
warm room, and filtered. 
An oil presser of Calcutta informed me that, in Calcutta, 
the expressed castor oil is heated with water, in a tin ves- 
sel, until the water boils, by which a scum forms on the 
surface, and that it is then strained. Dr. Ainslie, however, 
states that, in Southern India, it is prepared by decoction. 
In both cases, however, it is heated in boiling water ; and 
it does not appear improbable that heat may effect some 
change in the oil, or the hot water extract something from 
it, by which its solubility may be lessened. With a view 
of elucidating this poiut, I made the following two experi- 
ments : 
Expt. 7. — Some English expressed castor oil was heated 
with water until the water boiled, and the ebullition was 
continued for several minutes ; but no visible change was 
effected in the mixture. No mucilage, or scum of any 
kind, separated from the oil, which remained as clear and 
transparent after the experiment as before. A portion of 
the oil, when cold, was mixed with an equal volume of rec- 
tified spirit, and the mixture shaken up ; it in a short time 
became clear and transparent. The solubility of the oil had 
