' ALCOHOL-TEST FOR THE PURITY OP CASTOR OIL 225 
Jard oil were now added, and the mixture well shaken. 
In a short time, and without the use of heat, a perfectly 
transparent homogeneous mixture was obtained. On stand- 
ing, however, fourteen vols, of a spirit, holding some oil in 
solution, separated. 
Expt. 17. — Two vols, of English expressed croton oil, 
one vol. of olive oil, and three vols, of alcohol, were mixed 
together. By shaking, a transparent homogeneous mixture 
was obtained. 
In other experiments, which I need not here enumerate, 
I find that castor oil enables nut oil, (the expressed oil of 
Arachh hypogsea,) jatropha oil, (the expressed oil of Curcas 
purgnns,) and anda oil (the expressed oil of Jlnda brasili- 
ensis,) to dissolve in rectified spirit. 
The various facts now detailed seem to me to be best ex- 
plained by supposing that both castor and croton oils, con- 
tain some principle which confers on their fatty oil the 
power of dissolving in alcohol, and that this principle does 
not exist in all samples of these oils in the same proportional 
quantity, and hence the different samples are unequally 
soluble in alcohol. The same principle enables other fixed 
oils to dissolve in alcohol when they are mixed with either 
castor or croton oil. 
Moreover, if we were further to assume that the quantity 
of this solvent principle, in both castor and croton seeds,in- 
creases the longer the seeds are kept, we should have a 
ready explanation of the greater solubility of castor and 
croton oils expressed in England, from seeds brought from 
India, and which are often musty, than of those oils ex- 
pressed in India from fresh seeds. 
In the Edinburgh Pharmacopoeia it is stated that castor 
oil "is entirely dissolved by its own volume of alcohol. " 
The statement is quite accurate ; but if it is made as a guide 
to enable us to determine the purity of the oil, it is perfect- 
ly useless, for English expressed castor oil adulterated with 
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