322 History of Luminescence 



The discovery resulted by chance, from Baldewein's attempt to 

 collect the universal world spirit (Weltgeist) by setting hygroscopic 

 substances in the air, where they collected the moisture, and then 

 distilling them to concentrate the spirit. One of these substances 

 was calcium nitrate formed by treating chalk with nitric acid. On 

 one occasion the CaNOs was distilled under too hot a fire by mis- 

 take, and there remained behind in the retort a dry yellow material. 

 The retort was broken and about to be discarded when Baldewein 

 noticed that the encrusted surface gleamed at night. The designa- 

 tion, phosphorus hermeticus, came from Hermes, God of Science 

 and Art, the name by which Baldewein was known in the Society of 

 the Naturae Curiosum. A madrigal was composed in praise of the 

 discovery. In this poem, the fiery magnet stone was compared to a 

 sparkling star that ruled the destiny of Jason's ship and proclaimed 

 the progress of discovery as so clear and rapid that already afar off 

 could be seen the golden fleece. 



At first, preparation of the material was kept a secret and it was 

 sold for a high price, but the secret was soon learned by Johann 

 Kunkel von Lowenstern (1638-1703) , the great chemist of Witten- 

 berg, and others. The Baldewinian phosphor was apparently re- 

 sponsible for Kunkel's knowledge of the element phosphorus, the 

 new luminous material of Brandt. During a trip to Hamburg with 

 the Baldewinian phosphor, he was told of the Brandt discovery and 

 learned Brandt's secret also. A little later the new thermophos- 

 phorus was described by Elsholtz, in 1676, thus bringing to four the 

 number of shining bodies available for experimentation. 



In an extensive paper (see title page in fig. 34) published in 

 1675, Christian Mentzel (1622-1701) compared the Baldewinian 

 and Bolognian phosphors, coming to the conclusion that the former 

 absorbed light more easily, and emitted a brighter luminescence. 

 Explanations of the light were still couched in alchemistic language 

 and had no rational meaning. Baldewein's ideas are expressed in 

 his letter of gift to Oldenburg, and his enthusiasm was so great that 

 he, like Liceti, regarded the light of the moon itself to be similar 

 to that of his phosphor drawn from the sun in daytime and then 

 emitted at night. Like Montalbani and Liceti, Mentzel believed 

 the color -^ of the luminescence of phosphors to indicate their con- 

 stituents, yellow from gold, whose symbol was the sun, a bluish light 

 from the sulphur and the vitriol of Venus, the symbol for copper, 



*^ Color naturally played an important part in alchemistic belief. The philosopher's 

 stone, if red or yellow, was thought to impart qualities of gold to a base metal, if 

 white, then the qualities of silver. Hence the excitement at discovery of something 

 which would absorb the light of the sun, the symbol of gold. 



