74 PROCEEDINGS OF THE AMERICAN ACADEMY. 



contained gas, the vessels after return to the laboratory were placed 

 vertically in a large box having glass sides, and in such a position that 

 the lower stopcock projected through a thick rubber disk set in the 

 bottom of the box and having an opening just large enough for the stop- 

 cock to pass through it. The temperature in the box was indicated by 

 a thermometer, which could at all times be read through the glass panes. 

 When this temperature had remained constant for at least one hour, the 

 lower stopcock was opened for an instant allowing the surplus gas to 

 escape. A glass tube, connected by rubber joint with the lower end of 

 the stopcock, and just touching, but not dipping under the surface of 

 water, afforded a simple and safe means of preventing the possibility 

 of the entrance of air during the equalizing of the pressure. After 

 opening and shutting the stopcock the pressure of the contained gas was 

 assumed to be that of the air outside, as indicated by the barometer. 

 A drop of water was always introduced into the sample vessel before it 

 was filled, so tliat the gas could be regarded as saturated with moisture 

 when used for analysis. 



The gas vessel was connected with a mercury bottle B, the capillary 

 tubes at the ends of the cylinder having been filled with mercury befcre 

 the connections were made. By raising the bottle B and opening the 

 stopcocks the gas was slowly driven over from A through the glass tube 

 WD into the porcelain combustion tube HH, which contained a layer 

 of heated copper oxide forty centimeters long. The porcelain tube was 

 heated in a combustion furnace (partly shown in the sketch). The pro- 

 ducts of combustion of the gas passed by way of the glass bulb / and 

 the stopcocks W and X to the absorpion vessel Q, in which the carbon 

 dioxide was absorbed by solution of potassium hydroxide. This solu- 

 tion was delivered over when needed from the bottle 0, by pouring 

 mercury into the tap funnel U. The residual gas, after the absorption 

 of the carbon dioxide in Q was then caused to return by the same route 

 to the cylinder A, by adjusting the levels of the mercury reservoirs B 

 and R. A third passage of the gas over from ^ to ^ rendered it certain 

 that all hydrocarbons were completely burnt. The bulb J, and the 

 combination of bulb with three way tube Z)FF served to condense and 

 hold as water any steam due to burning of hydrogen of the gas in the 

 combustion tube, and prevent its return into the heated porcelain tube. 

 These bulbs proved very necessary to prevent breakage. The stopcock 

 on the bulb J served to discharge this condensed water. As it was 

 necessary to rinse the porcelain tube and its glass connections after the 

 passage of the gas from A to Q, or from Q to A, this was accomplished 



