io8 
PHYSICS: L. B. LOEB 
Proc. N. a. 
be covered with platinum black it is an easy matter to determine the rela- 
tive rise in temperature of the platinum black due to the adsorption of 
alcohol vapor in the presence and in the absence of air. Such experiments 
were performed by the writer. As the results were so decisive and as no 
reference to similar experiments could be found in the literature, a brief 
statement of the observations may be of interest. 
About 0.41 gram of platinum black, prepared from PtCU by precipitation 
with aluminium from an acid solution, was placed in a small beaker in a 
vacuum desiccator. The base of the desiccator contained a small quantity 
of H2SO4 which served to dry the platinum black. The beaker was sur- 
rounded as completely as possible with cotton wool to cut down convec- 
tion currents. The junction of a "Chromel-Alumel" thermocouple 
of No. 18 wire welded by copper was buried in the heap of platinum black. 
The leads passed through a rubber stopper to the circuit of a galvanometer 
which was closed through a key. 
The sensibility of the galvanometer used had several values lying be- 
tween a deflection of 1 cm. scale reading for 4.9 ° C. change in temperature 
to 1 cm. scale reading for 0.36° C, change in temperature. Greater sensi- 
bility could not be used as the temperature changes due to compression 
and exhaustion of the air in the experiments were in the neighborhood 
of one degree. By means of a two-way stopcock the desiccator could 
alternately be exhausted by an air pump or filled with a mixture of CO2 
and CH3OH, a mixture of air and CH3OH, or by CO2 alone. The gases 
were saturated with CH3OH by bubbling through a small quantity of the 
liquid in the bottom of a bottle. 
The following is the record of a typical experiment. After having been 
exposed to air and alcohol, the chamber was exhausted to about 2 cm. 
Hg pressure and washed out with CO2 gas at least three times. The gal- 
vanometer deflection after each filling registered about 4 cm. correspond- 
ing to a rise of about 1.44° C. This was due to the heat of compression 
of the CO2 on filling, as the pressure of the CO2 in the generator was above 
that of the air. Exhaustion of the gas in the desiccator also caused a 
drop of temperature of about 0.4° C. 
Alcohol vapor plus CO2 was then admitted and the deflection amounted 
to 5.5 cm. or to about 1.98°. The rise due to adsorption of the alcohol, 
or due to adsorption and oxidation of adsorbed alcohol by the remnants 
of the adsorbed O2 left on the platinum, therefore, amounted to about 
0.54° C. The mean of a number of results gave the value of the rise 
produced due to adsorption as about 0.36° C. 
If the gas admitted after exhaustion was a mixture of air and CH3OH 
vapor, instead of CO2 and CH3OH, the resulting deflection was on the 
average 24 cm. at the end of about a minute. The sensibility of the gal- 
vanometer was less than before so that this corresponded to a rise of 34° C. 
Different sensibilities gave about the same value for the rise in tempera- 
