Detection of Adulterations. 77 



accuracy, is sufficient for most purposes. We must refer to the work 

 of Bussy and Boutron-Charlard, for another and more accurate pro- 

 cess, which, owing to the figure required for its illustration, cannot 

 be conveniently introduced into the present paper. 



Oil of Ricinus Communis. — Castor oil, when pure and fresh, acts 

 very mildly upon the system ; but when rancid, it is very irritating, 

 and is unfit for use as a medicine. It should be very nearly colorless, 

 and free from any acrid taste. When mixed with other fixed oils, 

 the impurity may be detected by agitating the oil with eight times its 

 volume of alcohol sp. gr. .827 or .817. Any portion which is not 

 dissolved by the alcohol, may be considered as a different oil. Par- 

 ticular attention is paid to the specific gravity of the alcohol, since a 

 very moderate variation from the weight above stated, will produce 

 a considerable difference in the solvent power of the spirit. Very pure 

 specimens of castor oil sometimes assume the form of a soft solid, 

 by a slight diminution of temperature ; and this has led to an errone- 

 ous opinion that such preparations were adulterated. When, how- 

 ever, an oil appears pure in other respects, this property is not ob- 

 jectionable. 



Volatile Oils. — These substances generally bearing a high price, 

 are very liable to be mixed with various liquids of less value. The 

 fixed oils which are frequently used for this purpose, communicate a 

 greater consistency than the volatile oils themselves possess. The 

 fraud is also discovered by attempting to dissolve them in eight times 

 their volume of alcohol sp. gr. .817 ; the volatile oil being dissolved^ 

 while the other is separated. This, however, does not discover the 

 presence of castor oil ; for the detection of which, we may employ 

 a test applicable to the other fixed oils also and which consists in 

 dropping a little of the oil on a piece of unsized paper, which is then 

 to be moderately heated. If the liquid be pure, it evaporates com- 

 pletely ; while if any fixed oil be present, it gives the paper a greasy 

 stain. The increased tenacity conferred by the castor oil, must also 

 be kept in view. 



Alcohol is sometimes added to the volatile oils, and does not in- 

 crease their consistency, nor does it affect their color, unless its 

 quantity be considerable.* This substance may be detected by agi- 



* Would not a mixture of proper proportions of volatile oil, castor oil, and alcohol, 

 closely resemble the volatile oil ? The proper test in this case would be the unsiized 

 paper. 



