Chemiluminescence 437 



the Phosphorus shine, and sometimes not," and endeavored to " ex- 

 plicate this difficulty " by comparison with small (cold) fires that 

 are snuffed out by too much air (wind) , whereas great (hot) fires 

 burn more brightly. The experiments illustrate how important it is 

 to control conditions rigidly and how early in the history of experi- 

 mental science observers were plagued by conflicting results. 



The increase in brightness of phosphorus vapor with decreasing 

 oxygen pressure was also observed by F. Hauksbee, Secretary of the 

 Royal Society. In 1705 he wrote: 



In pursuance to the Commands of this Honourable Society, Having a 

 dark Room provided, the first Experiment was by drawing some Lines 

 on a piece of blue Paper with the Phosphorus, which became imme- 

 diately Luminous in the open Air, having a continual undulating Mo- 

 tion. This being plac'd under a Receiver, after some few Exsuctions, 

 the Undulation ceas'd, but the Luminous Quality appeared to be in a 

 great measure increas'd; the Receiver being farther exliausted, it became 

 manifestly brighter; and so continu'd, till on the admission of Air (which 

 was gradually done) the Light sensibly diminishing all the while. But 

 upon the Repitition of the Experiment, it was the Opinion of those 

 Gentlemen then present, that it did not appear altogether so brisk or so 

 vivid as at first. 



With a piece of solid phosphorus Hauksbee noticed the same 

 thing except that this time " Upon letting in the Air the Light 

 perfectly vanish'd; and it would have been in vain (as I have often 

 try'd) to have awaited in expectation of its Recovery in the open 

 Air." 



After the experiments of Hauksbee, the study of phosphorus be- 

 came largely a search for new sources and new methods of preparing 

 the remarkable material. In fact, the relation of phosphorus to 

 oxygen could not be properly investigated until the various gases 

 had been isolated as entities and purified. Research on the behavior 

 of phosphorus in vacuo or in gases was not carried out until the 

 1790's and early years of the nineteenth century. Included in the list 

 of workers were many prominent chemists— A. F. de Fourcroy 

 (1788), C. L. Berthollet (1795), J. F. A. Gottling (1795). A. N. 

 von Scherer and C. C. F. Jager (1795) , L. Spallanzani (1796) , L. G. 

 Brugnatelli (1797), J. B. van Mons (1797), N. Tychsen (1797), 

 M. van Marum (1797), C. W. Boeckmann (1800), A. Van Bem- 

 melen (1818), A. Bellani de Monza (1813), T. Graham (1829), 

 J. Davy (1833), N. W. Fischer (1845), and others in more recent 

 times. A. Schroetter (1852) was particularly emphatic that the lumi- 

 nescence only appeared as a result of oxidation and not from evapo- 



