

DR. EDWARD C. EDGAR ON THE ATOMIC WEIGHT OF CHLORINE. 9 



the prevailing conditions, some hydrogen must still have adhered to the walls of the 

 quartz vessel A ; but preliminary experiments showed the amount could not have 

 been greater than 1 part in 55,000 of the hydrogen used. If a correction could be 

 applied for this small weight of gas, it would have the effect of raising slightly the 

 atomic weight of chlorine. 



The Sprengel pump fastened to m was now separated by fusion from the apparatus, 

 and the tap p was closed so as to isolate the mercury in the manometer from 

 subsequent contact with hydrogen chloride and chlorine. 



The next series of operations was to evaporate the snow-white hydrogen chloride in 

 B and to condense it in the bomb immersed in liquid air. The successful accomplish- 

 ment of this required very careful manipulation, the details of which were only learnt 

 in the light of many failures. 



The first step was to warm gently the mercury in the quartz test tube Q so as to 

 fill the chlorine condenser with mercury vapour. To prevent its diffusion into the 

 bomb the coil R was surrounded by a freezing mixture of solid carbon dioxide and 

 ether. The steel tube X was now partially immersed in liquid air ; the taps n and r 

 and the screw valve W were opened ; and the evaporation of the solid hydrogen 

 chloride was commenced by slowly lowering the- liquid air surrounding the limb B. 

 The solid gradually evaporated into the combustion vessel, whence the gas passed on 

 to the chlorine absorption apparatus. Here all traces of chlorine combined with 

 mercury vapour and condensed as mercuric chloride. That the absorption of chlorine 

 was complete was shown conclusively by the bright surface of mercury in the broad 

 manometer tube T remaining untarnished at the end of the condensation. It was 

 found, in preliminary experiments under similar conditions, that no weighable amount 

 of mercury vapour could diffuse backwards out of Q. 



The purified hydrogen chloride, after its passage through Q, passed on to the steel 

 tube X and there condensed. By repeated trials it was found possible so to lower the 

 bomb into liquid air as to effect the condensation at a pressure never exceeding two- 

 thirds of an atmosphere. 



The condensation took over four hours. When it was complete, the taps n and r 

 and the screw valve W were closed ; and the whole apparatus was taken to pieces. 

 Then the palladium bulb, the liquid chlorine bulb, the chlorine condenser, and the 

 bomb were cleaned and weighed. 



In six experiments, then, the hydrogen chloride formed in the combustion was 

 condensed in a steel bomb by liquid air. In two other experiments Y (fig. 7) was 

 substituted for the bomb and the gas was condensed and weighed in water. In this 

 case the manipulation varied a little from that adopted in condensing the gas by 

 liquid air. Y was placed in a salt-ice mixture so as to freeze slowly the 100 c.c. of 

 water it contained. This done, Y was attached to a pump and rapidly evacuated. 

 At the end of the evacuation the phosphorus pentoxide showed no signs of harmful 

 deliquescence. The taps z and y having been closed, Y was disconnected from the 



VOL. CCIX. A. C 



