Du Mez—The Galenical Oleoresins. 957 
oleoresin of aspidium. In this case, it has proven to be of par¬ 
ticular value in detecting adulteration with castor oil as was 
first pointed out by Parry in 1911. Subsequent work by other 
investigators has not only confirmed Parry’s observations, but 
has shown that in some instances a low refractive index may be 
an indication of a low filicin content due to natural causes 1 ) 
as well. 
Since most of the other official oleoresins are sufficiently trans¬ 
parent to permit of the direct determination of this constant, 
it was thought that such determination might likewise prove to 
be of some aid in standardizing these preparations. That such 
an opinion has proven to be correct will be shown in connection 
with the discussion of this topic under the individual cases. 
For the determination of this constant in the laboratory, the 
Abbe refractometer was employed, all observations being made 
at 25° C. In those cases (the oleoresins of ginger and lupulin) 
where the color was too intense to permit of a direct determina¬ 
tion being made, the oleoresin was dissolved in an equal volume 
of castor oil and the refractive index computed from the follow¬ 
ing formula: 
n D (b) = 2n D (a + b) — n D (a) 
a = refractive index of castor oil. 
b — 16 il “ oleoresin. 
Chemical Properties 
Loss on Heating: 
The oleoresins without exception lose weight on drying. This 
loss is usually referred to in the literature as the moisture con¬ 
tent. It has been determined by heating the preparation at 
100 to 105° C. for a definite period of time, or until of con¬ 
stant weight. The falacy of designating the loss of weight 
thus obtained as the moisture content becomes evident when we 
take into consideration the fact that these preparations con¬ 
tain volatile substances other than water, which would also be 
removed by heating to a temperature of 100° C. Indeed, the oily 
1 The male fern rhizomes have been shown to vary in filicin content due 
to the climatic conditions under which they were grown, time of harvesting, 
et cetera. See under “Drug used,, its collection, preservation, etc.” 
