6 
BULLETIN 79, HAWAII EXPERIMENT STATION 
REFRACTIVE INDEX 
The method described by Coleman and Fellows (2) was used in 
determining the refractive index of macadamia kernels: A weighed 
amount of the material is ground in a mortar with a known amount 
of Halo wax and the index of refraction of the liquid determined. 
By referring this value to a curve of the refractive indexes of varying 
proportions of Halo wax and oil of the material being determined, 
85 
80 
75 
UJ 70 
u. 65 
60 
55 
50 
0.96 
N 
< 
• 
SM001 
"H-SHELL 
TYPE^ ( 
o 
R0UGH-S 
HELL TYF 
1 Z^A 
'E 
\\ 
vs 
1.08 
1. 10 
0.98 1.00 1.02 1.04 1.06 
SPECIFIC GRAVITY OF KERNEL 
Figure 1.— Relation of specific gravity of macadamia kernels to ether extract. 
the percent of oil in the Halowax is read off and the percent of oil in 
the original material calculated. 
In the construction of this curve, oil was extracted from the smooth- 
shell type of macadamia kernels with ethyl ether. The oil was dried 
in vacuo at about 60° C. and filtered through filter paper. Varying 
amounts of this oil were added to constant amounts of Halowax for 
refractive-index determination. The Halowax was measured with a 
pipette, the same pipette being used for all determinations both of 
the oil and of the kernel. To 5 ml of Halowax weighing 6.06 ± 0.0 1 g 
weighed amounts of macadamia oil were added to provide a range oi 
U to '_ ,( .) percent of oil in the mixture 
ae i 
efractive index was deter 
