Triboluminescence and Piezoluminescence 379 



refers to light emission during solution of crystals. Crystallolumi- 

 nescence has been attributed by Trautz and Schorigin (1905) to 

 fracture of the newly formed crystals as they crowd each other during 

 growth. However, not all cases of crystalloluminescence appear to 

 be capable of the above explanation, notably NaCl, KCl or AsCU, 

 as explained later. The interpretation of lyoluminescence is more 

 obscure. 



Triboluminescence and Piezoluminescence 



EARLY OBSERVATIONS 



The first knowledge of triboluminescence appears to be connected 

 with sugar. Many early writers have mentioned the light which 

 appears when lump sugar is scraped. One of the oldest records, 

 already referred to, comes from Francis Bacon (1561-1626) in the 

 Advancement of Learning (1605) , but triboluminescence of sugar 

 must have been observed before Bacon, as cane sugar was prepared 

 since earliest times in India and Persia and introduced into Europe ^ 

 in the twelfth century. The original use of sugar was in medicine 

 and it did not become plentiful until sugar cane was disseminated 

 by the Spaniards in the fifteenth and sixteenth centuries. The early 

 sugar often formed a very hard mass which had to be chipped from 

 the container and any person attempting this at night would be 

 certain to observe the luminescence. 



Members of the Accademia del Cimento of Florence during the 

 decade 1657-1667 noted triboluminescence, judging from the follow- 

 ing statement, taken from Richard Waller's (1684: 158) translation. 



Of Bodies affordi7ig Light. . . . Besides Fires tones there are other Bodies 

 that seem to be greater Conservatories of Light; for by striking them 

 together or by breaking them in the Dark, they Sparkle. Such are White 

 Sugar, Loaf Sugar and 5a/ Gemme [rock salt] in the Stone; all which 

 being broken in a Mortar, give forth so great a Light as distinctly to 

 discern the sides of the Mortar and the shape of the Pestle thereby: but 

 we have not succeeded to see the same appearance in pounding Common 

 Stone salt, Alumn, or Nitre; nor in Coral, the Yelloic or Black Amber; 

 Granats, or Marchasites: But Rock-Chrystal, and Agate, and Oriental 

 Jasper, either struck together, or broken, give a clear Light. 



The Italian scientists thus recognized a number of luminescences 

 from breaking materials and it is significant that they use the expres- 

 sion " hold the light which they receive." The complexity of tribo- 

 luminescence is well illustrated in certain kinds of diamonds, as 



^ See Dissertation on the history of sugar, by Prof. Beckmann, in Phil. Mag. 11: 

 1-7, 1802. Beckmann believed that sugar from sugar cane was unknown to the Greeks 

 and Romans. 



