184 ESSAYS BIOGRAPHICAL AND CHEMICAL 



bulb of about the same size ; on each side of the second 

 bulb there was a stop-cock, as shown in the sketch. To 

 begin with, the bulb A was pumped empty of air; it 

 contained the dry bromide of radium. The 

 stop-cock B was then shut. Next, some 

 water was placed in bulb (7, and it too was 

 pumped free from air, and the stop -cock D 

 was closed. B was then opened, so that 

 the water in C flowed into A , and dissolved 

 up the bromide of radium. As it was 

 dissolving, gas bubbles were evolved with 

 effervescence, and that gas collected in the 

 two bulbs, A and B. The sketch shows the 

 state of matters after the water had been 

 added and the gas evolved. The apparatus 

 was then permanently sealed on to a tube 

 connected with a mercury-pump, so con- 

 trived that gas could be collected. The stop- 

 cocks having been opened, the gas passed 

 into the pump, and was received in a small 

 test-tube. From the test-tube it was passed into a reservoir, 

 where it was mixed with pure oxygen, and electric sparks 

 were then passed through it for some hours, a little caustic 

 soda being present. This process has the result of causing 

 all gases except those like argon to combine, and they are 

 therefore removed. It was easy to withdraw oxygen by 

 heating a little phosphorus in the gas ; and it was then 

 passed into a small narrow glass tube, which had a platinum 

 wire sealed in at each end a so-called Plticker's vacuum- 

 tube. On passing an electric discharge from a Ruhmkorff 

 induction-coil through the gas in the tube, the well-known 

 spectrum of helium was seen. 



Thus helium was proved to be contained in radium 

 bromide which had stood for some time. The specimen 

 used was said to be about three months old, and the 



EXTRACTION OP 



GASES FROM 

 RADIUM BROMIDE 



