1888.] on PhospJiorescence and Ozone. 559 



about two feet in length, resembling to the eye the tail of a comet, 

 appears in the large glass vessel below. This phosj^horescent glow 

 is connected in some way with ozone, as it occurs only with oxygen 

 compounds; impure air is fatal to success in the experiments, 

 the glow being very sensitive to traces of organic matter, especially 

 to the vapour of essential oils and substances which have a smell. 

 Hydrogen extinguishes the light ; pure oxygen increases it, and 

 makes the glow shorter, with a tendency to break up at the lower 

 end ; carbonic acid gives a glow not so bright as air, and ozone 

 is produced from its decomjDosition. Nitrous oxide gives a very 

 bright brush. The phosphorescence disa^^pears at once when a 

 pocket-handkerchief containiug any odoriferous matter is brought 

 near the air inlet, and afterwards much time is lost in getting the 

 apparatus to work as before. It is no easy matter to get the brushes 

 back again ; this was first found out accidentally — for days and 

 weeks they had been puzzled in the laboratory to understand why one 

 tube worked better than another. Bisulj)hide of carbon is an organic 

 body, and is the only one, so far discovered, which allows the glow 

 to be obtained in its presence. That these downward luminous 

 brushes contain ozone is proved by means of the iodide of potassium 

 starch test (and others), which darken in the brushes, but are not 

 acted upon when placed outside them near the inner sides of the 

 lower glass vessel. By suddenly altering the rate of oxygen supply 

 passing through the vacuum tube most beautiful effects of apparent 

 explosions of phosphorescent glows can be produced. It is re- 

 markable that the rate of oxygen or air supply can be so regulated 

 that the luminous emission seems to come from a steady current of 

 gas passing down the middle of the tube, of almost uniform diameter, 

 and blending very little with the surrounding space. 



It is usually supposed that ozone is destroyed by heat, and can 

 only be produced at a low temperature, yet in these vacuum tubes it 

 is produced at a white heat. The piece of aj^paratus represented in 

 Fig. 2 enables the chemist to demonstrate that ozone can be con- 

 tinuously produced by heating pure oxygen to a temperature of 

 about 1600^ C. The apparatus consists of a glass tube bent at its 

 lower end, and passing up the centre of a tube of platinum ; a little 

 hole in the latter is placed just above the top orifice of the glass tube. 

 The upper part of the apparatus is covered with an outer tube of 

 platinum, which at the toj) very nearly touches the inner one. In 

 action a regulated current of water flows up the inner platinum tube, 

 then passes down the central glass tube, which is made longer than 

 the platinum tube; consequently it sucks in and carries down air, 

 which it draws through the little hole in the top of the inner platinum 

 tube. The top of the outer tube is then raised to near the melting- 

 point of platinum, by means of an oxyhydrogen flame, and the oxygen 

 beneath raised to this temperature is suddenly withdrawn and cooled 

 by the water current, and carried down to a collecting vessel for 

 examination. When tested, it is found to contain ozone ; hence ozone 



