442 History of Luminescence 



periodic phenomena 



One of the remarkable properties of phosphorus luminescence is 

 the periodic appearance and disappearance of the light under cer- 

 tain conditions. It was noticed by the earliest observers. For exam- 

 ple, Boyle (1680) wrote that the light from material on his hands 

 " seemed to tremble much, and sometimes, as it were, to blaze out 

 with sudden flashes, that were not lasting." Fred. Slare (1681) , 

 noted flashes like lightning in a jar containing phosphorus, while 

 Hauksbee (1705) referred to the " undulating motion " of lines 

 drawn with phosphorus on a piece of paper. 



During the eighteenth and nineteenth centuries, particularly the 

 latter part of the nineteenth, when the behavior of phosphorus in 

 various gases and the influence of inhibiting vapors was being 

 studied, the periodic luminescence was frequently observed. The 

 pulsating light appears when conditions are critical for lumines- 

 cence, for example near the lower or upper luminescence pressure 

 of oxygen or when enough inhibitor is present nearly to suppress 

 the light. Conditions may be chosen so that a wave or pulse of light 

 will spread through phosphorus vapor. 



The meaning of the periodic luminescence has baffled investi- 

 gators. Most of the theories concerning the phenomenon have been 

 suggested after 1900 and only one will be mentioned. The simplest 

 explanation is that an impermeable film, presumably of phosphorus 

 pentoxide, prevents the reaction of phosphorus and oxygen. Such 

 a film would explain the lack of luminescence in pure oxygen until 

 the temperature has been raised to the point where evaporation of 

 phosphorus can take place through the film. Any destruction of the 

 film would allow oxidation and luminescence to proceed. The 

 periodic breaking of a film might occur under critical conditions of 

 oxidation velocity determined by the presence of inhibitors. For 

 example I. Corne (1882) held that the action of turpentine vapor 

 was to form a solid " acide terebenthophosphoreux " film which 

 preserved the phosphorus against the action of oxygen. Corne 

 believed that phosphorus was not attached directly by oxygen but 

 that vaporization must occur first; hence no light appears in pure 

 oxygen because the high pressure of oxygen prevents vaporization. 

 Despite the research devoted to the problem of periodic lumines- 

 cence, a satisfactory explanation has not yet been achieved. 



RELATION TO OZONE 



The peculiar behavior of phosphorus luminescence resulted in 

 many theories of mechanism during the twentieth century and it is 



