Solubility of Radium Emanation. 843 



a three- way stopcock E. These stopcocks are joined to the 

 bulbs as closely as possible, and the glass tubing connected 

 with each stopcock is only about 1*5 cm. long. 



For convenience we shall call the bulb ABC' the mixing 

 bulb, and DEF the sampling bulb. 



The volumes of the bulbs and the tubing connected with 

 them must be known. These are conveniently determined 

 by completely filling with mercury at a definite temperature 

 and weighing the mercury. 



Before a series of experiments the bulbs were thoroughly 

 cleaned, dried, evacuated, and then weighed. In lubricating 

 the stopcocks as little grease as possible was used. It is essential 

 that the stopcocks should be able to maintain a vacuum in the 

 bulbs, and this point was always tested before experiment. 



To perform an experiment the mixing bulb was evacuated, 

 and the emanation to be used was admitted into it. The 

 required amount of absorbing liquid was then forced slowly 

 into the bulb by the pressure of the atmosphere, and air, or 

 other gas, was allowed to fill the bulb to the pressure required. 

 When other gases than air, or air at pressures other than atmo- 

 spheric, were to be employed as carriers of the emanation, the 

 necessary apparatus for the purpose was constructed and used. 



After admitting the emanation and the absorbing liquid 

 into the mixing bulb, both mixing and sampling bulbs were 

 joined together by about two centimetres of very tightly 

 fitting pressure-tubing TT, in the manner shown in the 

 diagram (fig. 1). In order that the joints should be perfectly 

 airtight the pressure-tubing was secured by wire and wax so 

 that when tested the joints showed no leak whatever. The 

 three-way stopcock attached to the sampling bulb was next 

 attached to a Toepler pump, and the interior of the sampling 

 bulb and connexions were exhausted, the stopcock of the 

 mixing bulb still being kept closed. The three-way cock 

 was then closed to the open air and disconnected from the 

 pump, after which the bulbs were placed in a bath maintained 

 at the required temperature of experiment. The manner of 

 connecting the bulbs together made the whole quite rigid, 

 and shaking could be performed by a suitable mechanical 

 contrivance or by hand, whichever was the more convenient. 



The temperature bath used in these experiments was a 

 thermostat controlled by a toluol bulb with attached electric 

 relay and electric heating device. Usually the temperatures 

 were constant to o, l C, but sometimes on account of the 

 sticking of the relay there was a larger variation, but never 

 greater than c- 2 C. 



Although the equilibrium distribution of emanation is 



