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



and, on a larger scale, in fig. 5) in which mercury could be heated to absorb chlorine, 

 R, a small spiral condenser, X, a nickel-plated steel tube in which to condense the 

 hydrogen chloride, and side tubes leading to two manometers, P and T, and to two 

 Sprengel pumps. 



In order to weigh the chlorine condenser separately, two taps, n and r, were 

 inserted, and ground-glass joints fitted at N and S. The ground-glass joint S led to 

 the apparatus in which hydrogen chloride was condensed and weighed. 



In six experiments this was a weighed nickel-plated steel bomb, consisting of a 

 cylindrical steel tube X (fig. 6), connected by a length 

 of flexible copper tubing Avith a screw valve W. 

 The bomb was connected to the rest of the appa- 

 ratus by the joint V a joint between glass and 

 steel cemented by solid phosphoric acid. 



In two other experiments the hydrogen chloride 

 was absorbed and weighed in water. Fig. 7 is a 

 sketch of the apparatus used. Y was a boro-silicate 

 glass bulb (over 200 c.c. in capacity), fused to which 

 was a tap y and a phosphorus pentoxide tube to 

 absorb water vapour. Z was a thick-walled capillary 

 tube in which hydrogen chloride could be condensed 

 by liquid air. A tap z closed the apparatus. 



Metaphosphoric acid was used as a lubricant on 

 all the taps and ground joints. It is somewhat 

 troublesome to spread evenly on a glass surface, but it has none of the disadvantages 

 of organic lubricants. 



8. Method of carrying out the Combustion and Condensation. When the palladium 

 bulb, the liquid chlorine bulb, the chlorine condenser, and the hydrogen chloride 

 condenser had been weighed, the different parts of the combustion and condensation 

 apparatus were fitted together. Then the pumps, fitted with McLeod gauges, were 

 set working so as to evacuate the combustion vessel A (fig. 3) through the connecting 

 tube m and the rest of the apparatus through t. Since the quartz tube Q and the 

 steel bomb X had been previously evacuated prior to weighing, it was only necessary 

 to evacuate the small portion between V and r. So as to facilitate the removal of 

 traces of nitrogen, most of the glass apparatus was heated by the flame of a Bunsen 

 burner. 



When the pressure had fallen as low as some thousandths of a millimetre of 

 mercury, the now vacuous combustion vessel was isolated from the pump by closing a 

 tap, and the lower end of the vertical limb B was immersed in liquid air. 



The liquid chlorine bulb E was packed into a freezing mixture of calcium chloride 

 and ice, in which it was kept during the combustion. 



The palladium bulb L, enclosed in an asbestos-lined copper box, was gradually raised 



Fig. 7. 



