592 Profs. B. B. Boltwood and E. Rutherford 



on 



measurement of volumes rather than of pressures as is the 

 usual method of employing this type of apparatus. The 

 volume of the capillary tube E was accurately determined 

 for various lengths by direct calibration with a thread of 

 mercury. The comparison tube e was made from the same 

 piece of tubing as E and had essentially the same diameter 

 and cross-section of bore, so that no correction had to be 

 made for the capillary depression of the mercury in the 

 tube E when the pressure of gas contained in E was 

 measured. Two side tubes entering the tube A from the 

 right could be closed by glass float-valves, the lower of the 

 usual design, the upper of a special design, which prevented 

 the " trapping " of gas between the glass float and outer 

 jacket. The lower tube extended to the phosphorus pent- 

 oxide bulb M, was provided with a stop-cock a, and connected 

 with the carbon tube C, which contained a few grams of 

 coconut charcoal. A side tube c permitted the introduction 

 of small volumes of pure, dry, electrolytic oxygen at this 

 point in the apparatus. The upper of the two tubes leading 

 from A to the right had a thin-walled bend, U, and led 

 through the stop-cock b to the tube M and through the stop- 

 cock d to the transfer pump H. The transfer pump H was 

 used for removing gas from the bulb M and introducing it 

 into A and its connexions. 



Further attachments to this portion of the apparatus con- 

 sisted of the burette B with sealed-in platinum wires between 

 which a spark could be produced. This burette was used for 

 introducing gases into the apparatus by way of the tube L 

 which terminated under mercury. After sparking, the gases 

 could he passed through the tube T, of hard glass, containing 

 copper oxide heated to a red heat. 



The remaining portion of the apparatus, shown on the 

 right, was used for examining the spectrum of the gas which 

 had been measured in A. The details of its construction will 

 not he described in this paper, but it is sufficient to say that 

 it permitted the removal of the residual gas from the tube A, 

 and its introduction into the small tube S where its spectrum 

 could be conveniently examined. 



All of the different vessels, A, H, B, &c. were provided 

 with Bunsen traps to prevent the entrance of air along the 

 mercury columns, and the glass tubes connected with these 

 extended downwards for a distance of over 76 cms. as is the 

 usual practice. The extension of these tubes, the rubber 

 tubes, and the mercury reservoirs attached to the lower ends 

 are not shown in the diagram. 



