20 
BULLETIN 1308, U. S. DEPARTMENT OF AGRICULTURE 
Tabije 4. — Estimation of benzophenol in the known mixtures described in 
experiment 8 
Ratios of benzophenol to total phenols 
Quantity of total phenols in sample 

100 
2.5 
100 
5 
100 
10 
100 - 
20 
100 
Per cent 
found 
Per cent 
found 
i 1.9 
2.2 
2.4 
Per cent 
found 
14.0 
4.4 
4.8 
Per cent 
found 
18.5 
9.5 
Per cent 
found 
i 18.6 
2.5 milligrams . ._ 
0.1 
20.0 
i From paper referred to (2). 
FRACTIONAL DISTILLATION OF THE TOTAL PHENOLS 
The isolation of the total phenols from a saponified cresol solu- 
tion in a quantity and condition suitable for a complete fractional 
distillation appears to be too tedious an undertaking to be practical. 
But the determination of benzophenol removes any necessity for 
fractional distillation over the lower range of temperatures, so that 
only a single temperature reading in the higher range is needed for 
the purpose of detecting the presence of significant proportions of 
high-boiling phenols. 
If the sample is a saponified cresol solution, the alkaline extracts 
from the estimation of total phenols are saved and serially shaken 
through 20 cubic centimeters of petroleum ether to insure the re- 
moval of traces of kerosene, etc. They are next united in a 250- 
cubic centimeter Erlenmeyer flask containing a scrap of Congo-red 
test paper and acidified with concentrated hydrochloric acid. The 
contents of the flask, when cold, together with 50 cubic centimeters 
of ethyl ether used to rinse it, are transferred to a separatory funnel, 
shaken, and separated after the ether solution has become perfectly 
clear. After the aqueous layer has been completely drained from 
the funnel the ether solution is transferred to a 150-cubic centimeter 
flask and most of the ether is evaporated on the steam bath. A 25- 
cubic centimeter distilling flask of hard glass, with a neck measuring 
about 6 centimeters in length, and with a side tube at the middle of 
the neck, is weighed when clean, dry, and containing a few grains 
of powdered zinc. The phenolic residue is rinsed into the flask 
with a little ether or benzene ; then the flask is set inside a bottomless 
hard-glass beaker as a shield, which rests on an asbestos board pro- 
vided with an evenly circular perforation 2 centimeters in diameter, 
snugly covered by the bottom of the flask. The thermometer must 
be of the short-stemmed type and should be fixed with its bulb 
midway between the bottom of the neck and the side tube of the 
flask. The flask should be supported in an upright position and 
connected to a condenser of any convenient type. 
Distillation is conducted in the customary manner until the ther- 
mometer indicates the chosen temperature, making allowance for all 
corrections, at which point the flame is quickly taken away. After 
the flask has cooled the corks are removed, the inside of the neck 
above the side tube and the side tube itself are freed from condensate 
by twists of filter' paper or cotton ; then the flask and contents are 
