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441 
In order to approach the equilibrium from the other side the tube was 
then heated for a few hours at a higher temperature and returned to the 
thermostat. The pressure at first registered 34.0 atmospheres and then 
fell gradually as shown in Table IT. 
TaBLE II. 
Time in hours. Pressure in atmospheres, 
0 34. 0 
24 33. 4 
48 32.5 
72 32.3 
According to these data the true pressure of equilibrium lies between 
31.8 and 32.3. The manometer had been verified by comparison with 
a standard manometer but may have been in error by a considerable 
fraction of an atmosphere. Therefore, we will take in round numbers 
32 atmospheres as the decomposition pressure at 325.° 
During this whole experiment there was not the slightest leakage from 
the tube and the whole apparatus was eminently satisfactory. Unfortun- 
ately, the work was interrupted at this point by my removal from the 
chemical laboratory of Harvard College to the Government Laboratory 
of the Philippine Islands and the experiments had to be continued with 
other apparatus. 
THE DECOMPOSITION PRESSURE AT 302°. 
The next experiments were made in a bath of diphenylamine vapor. 
The first method used was an indirect one. It consisted in heating the 
silver oxide in a closed glass tube which was drawn out at one end to 
a capillary; cooling it suddenly by removal from the bath; opening the 
capillary under a gas burette; and calculating from the volume of gas 
thus collected and from the volume of the tube (exclusive of that 
occupied by the remaining mixture of silver and oxide) the pressure 
which had been exerted in the tube at the temperature of the bath. Eight 
tubes containing different quantities of silver oxide were suspended in 
the vapor of boiling diphenylamine contained in a large iron receptacle, 
and were kept in this bath for six days. During this time it was found 
necessary to renew the diphenylamine several times on account of its 
gradual decomposition. ‘The pure substance (Kahlbaum’s) boiled at 
302°. In the course of the experiment several of the tubes were broken ; 
in others the oxide had entirely decomposed, so that finally only one tube 
of the eight could be used for determining the pressure. This was broken 
under water and 8.58 cc. of oxygen was collected in the burette at 
760 mm. and 30°. The tube was weighed, then filled with ether, boiled 
to drive out all the air, filled again and weighed. From these two 
weighings the volume of the tube was found to be 0.92 ce. The pressure 
— 8.58 +0.92 2734-302 
- ° * . ‘ “as ppt laa ee . ; 
at 302° must therefore have been 099 273 430° or 18.0 
