336 History of Luminescence 



a composition, which retains both common light, and that of electricity, 

 much more strongly than either the Bolognian stone, or any other known 

 substance whatever. With this new phosphorus he makes a great number 

 of most beautiful experiments. 



Another observer was Michaele de Grosser who published a small 

 book in Latin *° in 1777 on phosphorescence of the diamond in 

 which he confirmed many previous findings, observed luminescence 

 in a vacuum, and showed that diamonds could be excited not only 

 by warming but by electric sparks. 



The most comprehensive study of phosphorescence excited by 

 electricity was made by Karl von Kortum (1748-1808) , a banker 

 and mayor of Warsaw. In 1794 von Kortum used " fat " electric 

 sparks from a Leyden jar, allowing the spark to pass over the sur- 

 face of the material and observing the color, brightness, and dura- 

 tion of the phosphorescent streak. He studied 168 substances, or- 

 ganic and inorganic, obtaining results similar to those of Beccari 

 and Wilson. Von Kortum found that nuts, seeds, wax, bone, egg 

 shells, silk, wool, cotton, linen, gums, starch, potatoes, etc., all phos- 

 phoresced provided they were dry, but resin, shellac, glass, porcelain, 

 sulfur, butter, amber, tourmaline, and all metals did not. Oxygen 

 was not necessary for the phosphorescence. 



Although pure water had never been observed to be phospho- 

 rescent or fluorescent, von Kortum reported that ice would lumi- 

 nesce on exposure to an electric discharge, and J. Weber (1802) 

 found that it was triboluminescent.*^ 



Van Kortum's success, like that of Beccaria, Mr. Lane, and Canton, 

 was of course due to the abundant ultraviolet wave-lengths in the 

 spark, as indicated in a later section. In the nineteenth century the 

 study of phosphor excitation by electric sparks became an important 

 approach through the work of Dessaignes (1809) , Heinrich (1812) , 

 Pearsall (1830, 1831) , and the Becquerels (1839) . When the effect 

 of electrical discharges on material enclosed in glass tubes was 

 studied, entirely new phenomena appeared, which led to recogni- 

 tion of various radioliuninescences (see Chapter XII) . 



It was E. Becquerel (1839) who pointed out the difference be- 

 tween glass and quartz in allowing certain rays from an electric 



*" Translated in Jour, de Physique 20: 270-283, 1782. De Grosser endeavored to make 

 non-phosphorescent diamonds luminesce by heating but mostly in vain. One diamond 

 heated in borax became phosphorescent but heating diamonds with rocksalt was of 

 no avail. 



*^ P. Heinrich (1811, 1920: 83 and 482) mentioned a number of observations on lumi- 

 nescent ice but he could never confirm its triboluminescence as reported by Wasstrom 

 (1798) . In 1856 M. Ghaye described luminescence of fresh falling snow flakes and also 

 of the rim of his hat, a circumstance which indicates the snow crystals were probably 

 charged and the light an electroluminescence. 



