Refractive Index and Alcohol-solvent Power 
of a Number of Clearing and Mounting 
Media. 
Contributions from the Zoological Laboratory No. 3. 
BY C. E.. M’CLUNG. 
As far as the author’s observation goes there has not been 
published any very extensive list of the refractive index and clear- 
ing value of the reagents commonly used by microscopists. Such 
a want is noted by Lee in the fourth edition of his ‘‘Vade Mecum,”’ 
page 66. In the hope of assisting in the compilation of such 
valuable information, the writer has experimented on the reagents 
named in the following table with the results there noted. The 
instrument employed in the determination of the refractive index 
was the Pulfrich refractometer, the sodium flame being used as the 
source of illumination and the conditions of temperature being 
kept as nearly constant as possible. 
In ascertaining the clearing value of the substances a number 
of methods were tried but finally abandoned for the simple one of 
testing the strength of alcohol that would dissolve in the reagent 
and produce a clear solution. While this method does not truly 
represent the conditions present in a tissue where the clearing 
agent is replacing the absorbed alcohol, yet actual practice indi- 
cates that the results are approximately correct, at least nearly 
enough so to make the figures of practical value. Strengths of 
alcohol varying by 5 per cent. were employed, and the weakest one 
that the reagent would dissolve is given in the table as the lowest 
grade of alcohol from which it will clear. 
The different substances tested were taken from the ordinary 
laboratory supply and supplemented by others obtained from the 
Pharmacy department of the University. The latter consisted 
almost entirely of essential oils from the house of Lehn & Fink, 
New York. When possible, more than one sample of each 
reagent was obtained and tested. 
(197) KAN, UNIV, QUAR., VOL. VII, NO. 4, OOT,, 1898, SERIES 4, 
