AND RATIO or THEIR ATOMIC WKKIIITS. 108 



extinguished by slight ciror in :ul justmeiit of the stopcocks for .•uluiitting tlie gases, 

 the pressure of tlie hydrogen wouhl, befoiv it wiis [lossihlc to make readjustment, 

 so increase as to bh)w oft' througli tiie nieicury, as once happened even when the 

 safe pressure was two atmospheres, and tlie working [)ressure oidy half an 

 atnios]ihere. 



8. SYNTHESIS OF WATER. THE COMr.IIS'riON. 



The combination of f(M-ty-t\vo liti'es of hydrogen with twenty -one litres of 

 oxygen took about an hour and a half. When the pressure of the oxygen became 

 very small, extreme care was required to continue the combustion. I have once 

 carried it till the pressure of oxygen and water vapor together was only eight centi- 

 metres of mercury. The attempt to do the same again was unsuccessful. 



When the combustion was ended, the stopcocks m and n were closed, the 

 palladium tube was closed by fusion at the point A, Fig. 34, and the globes con- 

 taining oxygen wei'e closed at their stopcocks. In experiments numbered 10, 11, 

 and 12, the globes were also closed in the same way as the palladium tubes. 



The lower part of the combustion chamber was now immersed in a freezing 

 mixture. When the water produced had been frozen and cooled as much as possi- 

 ble, the stopcocks of the apparatus were opened, the mercury was withdi-awu from 

 the tubes 4. and 5, and the Toepler pump was used to ti-ansfer the gas I'emaining in 

 the apparatus and its connecting tubes to an eudiometei-. The tension of the vapor 

 of the water at — 18° C. being only 1.1 mvi., the exhaustion could be made suf- 

 ficiently complete. The phosphorus pentoxide tubes showed no signs of harmful 

 deli(piescence during the half hour they had to serve. 



When the exhaustion was complete, the combustion apparatus was closed by 

 f.isiou at h and /<, Fig. 36. The parts fused oft: from the diffei-ent parts of the 

 apparatus were now cleaned from adhering wax or paraflin, and the points which 

 had been broken off were put with those to which they belonged. The four parts 

 of the apparatus were then weighed. 



9. SYNTHESIS OF WATER. WEIGHING THE OXYGEN AFTER A COJIRUSTION. 



It is obvious that the volumes of the globes when full and when partly 

 empty would differ by the amount of the corresponding elastic compression. In 

 the first and second experiments, the oxygen was withdrawn from the globe as 

 completely as possible ; the globe after the experiment was therefore weighed 

 against the counterpoise proi)er for the empty globe, and a correction computed for 

 the difference of volume. In the experiments from the third to the seventh, the 



