12 



Dr. E. P. Perman and G. A. S. Atkinson, 



of a capacity of about a litre, in others of about 250 c.c. ; its stem, of 

 about 1 mm. bore, was cemented by means of a mixture of litharge 

 and glycerine, to a cup on the capillary tube carrying a ; B a muffle 

 furnace, C a glass globe of about 200 c.c. capacity, placed in a water- 

 bath ; D and E absorption apparatus ; E a large globe of about 8 litres 

 capacity for steadying the pressure ; G a pressure gauge ; H a thermo- 

 electric couple of platinum and platinum-rhodium enclosed in a porce- 

 lain tube; K the "cold junction," each wire of the couple being 

 connected with a copper wire and placed in a test-tube containing 

 alcohol, the two tubes standing in a beaker of water ; L the galvano- 

 meter, which, with M, the resistance box and switch, and N, the scale 

 and lamp, were in an adjoining room. P is a Bunsen valve to prevent 

 back-rush of water from the pump ; a, I, c, d, e, /, g, h, k, and I are 

 stopcocks, a, b, and d being diagonal three-way stopcocks arranged so 

 that air could be admitted from the outside in the directions shown by 

 the arrows. These stopcocks were obtained from Messrs. C. E. Miiller 

 and Co., and have proved extremely satisfactory. The lubricant used 

 on a, h, and c, which came into contact with liquid bromine, was 

 phosphorus pentoxide which had become viscous by exposure to the 

 air. Further action of the air was prevented by a covering of burnt 

 rubber and vaseline. 



Method of Procedure. 



Filling the Globe. — The small globe C containing bromine was heated 

 by means of the water-bath to about 60° C, i.e., about the boiling 

 point of bromine under atmospheric pressure. The globe A was 

 exhausted by means of a water air pump, through the connections 

 shown, to about one-sixth of an atmosphere, sometimes less. The 

 stopcock d was then closed, and b and c opened to admit bromine into 

 the globe A, the connecting tubes being warmed by means of a Bunsen 

 burner to prevent the condensation of bromine in them. After a short 

 interval (15 to 30 sees.) 6 was closed and <i opened; the globe was 

 exhausted to about the same extent as before, and all the bromine 

 carried off was absorbed by strong caustic soda solution placed in the 

 absorption tube and flasks D and E. (The arrangement of the flasks 

 shown in the figure was found to be a very convenient one ; it consists 

 of two small wash-bottles with the long tubes connected, or in one 

 piece ; by this arrangement the liquid was never carried over in either 

 direction.) 



The large globe F was usually kept exhausted and the pump at 

 work. If necessary the globe A could be connected directly with the 

 pump by turning off" stopcock h. 



The globe was again put into connection with C, again exhausted, 

 and so on, the filling process being repeated seven times. Some bro- 



