The Chemistry of Light-Production in Luminous Organisms. 



195 



form, and also by potato-juice which contains considerable quantities 

 of oxidizing enzymes. In no case was phosphorescence observed. 

 The boiling ethyl alcohol, 1 cold amyl alcohol, and ethyl butyrate must, 

 therefore, break up the photogen. It is the alcohol itself and not the 

 temperature (78.4) of boiling alcohol which is responsible for the 

 destruction of the photogen, as the dried powder will withstand this 

 temperature for 24 hours without any appreciable diminution in its 

 power to phosphoresce. McDermott finds that liquid sulphur dioxide 

 and liquid ammonia also destroy the photogenic power (20). 



EXTRACTION WITH AQUEOUS SOLVENTS AND EFFECT OF OXYGEN. 



If the luminous tissues of the firefly are extracted with water a solu- 

 tion which still gives light on filtration through filter paper is obtained. 

 The light lasts a certain time and then disappears. 



If the dried powdered luminous tissues of the 

 firefly are allowed to come in contact with oxygen- 

 free water, no light is produced, but if we admit oxy- 

 gen, in a few minutes we find the mixture becomes 

 luminous. If we wait for an hour or more before 

 admitting oxygen, no light is produced. The appa- 

 ratus shown in figure 1 is convenient for demon- 

 strating this. 



The material to be extracted is placed in the 

 vessel C (fig. 1), provided with a ground-in stopper 

 connected with a 120 stopcock. The water to be 

 rendered free of oxygen is placed in B after passing 

 hydrogen through stopcock C and closing it. B is 

 connected through A with a hydrogen generator. 

 The hydrogen is passed through potassium hydroxide 

 to remove acid and then over a glowing platinum 

 wire (in A) to remove the last traces of oxygen, a 

 much better method than passing the gas through 

 alkaline pyrogallol. By alternately exhausting B 

 through b, connected to an air-pump, and refilling 

 with hydrogen several times, the water can be quickly 

 rendered free of oxygen. C is then connected to B 

 through c and one of the arms of the 120 stop- 

 cock (d) whose other arm is connected with an air-pump. C and the 

 arms of d are then exhausted. The 120 stopcock is then turned to 

 connect C and B and c is opened, allowing the pressure of the hydrogen 

 to drive the solvent on the material in C. The proper amount of fluid 

 for extraction should be placed in B, so that the hydrogen may follow 

 it through and fill the chamber C. Then d is closed, when C can be 



FIG. 1. Apparatus for 

 extraction of lumi- 

 nous tissue in ab- 

 sence of oxygen. 



1 The 99.8 per cent absolute alcohol was distilled over metallic calcium and collected in a receiver 

 protected from the air by CaCl-j in order to remove the last traces of water. 



