996 Wisconsin Academy of Sciences, Arts, and Letters. 
Refractive index: A refractive index of not less than 1.490 
at 40 °C is required for this oleoresin by the late edition of the 
British Pharmacopoeia. This is in accordance with the observa¬ 
tions of Hill (1913). The statement by Parry (1911), that 
the refractive index should not be below 1.500 when deter¬ 
mined at 20 °C is confirmed by the results which were obtained 
by Harrison and Self (1913), and is more in conformity with 
the observations made in this laboratory at 25° C. When the 
oleoresin is properly prepared, ether being the menstruum used, 
the refractive index appears to vary directly as the crude filicin 
content. A low refractive index, therefore, indicates a pre¬ 
paration naturally low in filicin content. With respect to the 
commercial oleoresins, however, a low refractive index may also 
result from adulteration with castor oil or chlorophyll, or may 
be due to the presence of unevaporated solvent as is shown in 
the tables which follow: 
Table 15.—Refractive indices of laboratory preparations . 
Sample 
No. 
Date 
Observer 
Solvent 
Refractive 
index 
1 . 
1918 - 
DuMez.. 
Ether . 
At 25° C 
1.500 
1. 
Harrison Sr. Self. 
At 20° C 
1.4995 
1.5018 
2. 
3. 
1.5036 
1.5088 
4. 
“ “ 
5 . 
fct tt 
1 5088 
6 . 
1.5102 
7 . 
“ “ 
1.5120 
8 . 
1.5122 
9 . 
f* •< 
1.5126 
0 . 
“ “ . 1 ...... 
1.5145 
.1 . 
1.5157 
1 . 
1.916 
DuMez . 
Acetone. 
1.500 1 
2 . 
Ether . 
1.498 1 
1 These figures represent the refractive indices of oleoresins which had 
stood in the laboratory for six years. 
