THE VARIATIOin OF ANC4LES OBSERVED IN CRYSTALS. 
497 
supersaturated to a saturated solution. In these experiments the constitution of the 
original saturated solution was not known, but that of the diluted solution at the 
close of the series was ascertained, and the former was approximately calculated 
from it. 
(1.) Refractive Indices of Solutions of Potash-alum. 
Ihe refractive index of a saturated solution of potash-alinn was approximately 
determined to be 
r34263 at 14° by total reflection, 1-34220 at 16°-2 by minimum deviation. 
The following numbers represent the observations made l)y the total reflection 
method, with a jjrisni of angle 44° 58' and index 1-51704, upon 50 cub. centims. of a 
saturated solution of alum diluted down by successive additions of 1 cul). centim. of 
water (up to d = 19° 18'), and then of 5 cub. centims. (up to ^ = 19° 8'), and finally 
of 25 cub. centims. 
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VOL. CCII.-A. 
