CONTROL OF SAPONIFIED SOLUTIONS 11 
is to collect the whole distillate in the tar-acid funnel and to de- 
hydrate it by shaking with a sulphuric-acid solution of definite 
strength. 
EXPERIMENT 4(a) 
Twenty-five cubic centimeters of redistilled cresol L B were dis- 
solved in about TO cubic centimeters of purified kerosene in the tar- 
acid funnel. The solution was shaken with successive 50 cubic centi- 
meter portions of sulphuric-acid solution of known specific gravitv at 
25° 
p^o" C.j and the corresponding changes in volume of the kerosene 
solution were noted, all measurements being made at 25° C. The 
first extraction removed tar bases. Subsequent extractions then 
involved only the distribution of tar acids and water between the 
two layers. Any one acid of specific gravity between 1.315 and 
1.507, after the first extraction, effected a constant diminution of 
0.30 cubic centimeter in the volume of the kerosene solution for 
each successive extraction, owing to loss of tar acids. All sulphuric 
acids of specific gravity between 1.451 and 1.507 were interchange- 
able ; that is, no matter in what order these various acids were used 
for the extraction of a given kerosene solution, the decrease in vol- 
ume was always 0.30 cubic centimeter per extraction, which means 
that all such acids were equally effective as dehydrating agents and 
that all must therefore have acted with practically 100 per cent 
efficiency. However, if treatment with any one of these acids were 
followed by a treatment with acid of specific gravity 1.398 or less, 
the decrease in volume was less than 0.30 cubic centimeter; and, 
conversely, if a treatment with acid of specific gravity 1.398 were 
followed by a treatment with acid of specific gravity 1.451 the 
decrease in volume was greater than 0.30 cubic centimeter, which 
means that acid of the lower gravity is an imperfect dehydrator. 
Acid of specific gravity 1.555 effected a constant decrease of nearly 
0.40 cubic centimeter per treatment; that is, it extracted an inordi- 
nate proportion of tar acids as compared with acids of specific 
gravity 1.507 or less. 
EXPERIMENT 4(b) 
" Cresol H B," similarly treated, showed a constant decrease of 
0.20 cubic centimeter for each extraction with 50 cubic centimeters of 
acid of specific gravity 1.505. Apparently, then, the distillates may 
be effectively dehydrated by extraction in the tar-acid funnel with 
a sufficient quantity of sulphuric acid of specific gravity 1.505 with- 
out danger of loss of tar acids except through simple solution. 
From specific-gravity tables it may be calculated that 100 cubic 
centimeters of an acid of 1.505 specific gravity will require 13 cubic 
centimeters of water to reduce it to a specific gravity of 1.451. 
Therefore the distillate in kerosene of 25 cubic centimeters of a 
cresol containing not over 13 per cent water may be completely 
dehydrated by shaking with 25 cubic centimeters of a sulphuric-acid 
solution of specific gravity 1.505 at a loss of between 0.10 and 0.15 
cubic centimeters of the tar acids, the loss being less the lower the 
proportion of low-boiling homologues present. 
It will be noted that the error due to solubility of tar acids in the 
sulphuric acid is of opposite sign from the errors due to expansion 
