E. NEWTON HARVEY 287 



Basic lead acetate gives a voluminous heavy precipitate with crude 

 luciferin. After heating, the solution was filtered and the clear fil- 

 trate, which gave no further precipitate with basic lead acetate, gave 

 a brilHant light with luciferase. The precipitate washed twice with 

 water on the filter does not dissolve in water, but suspended in water 

 gives a faint light on adding luciferase. Uranium nitrate + acetic 

 acid does not completely precipitate luciferin from solution. These 

 results are recorded in Table III. 



Luciferin is therefore not completely precipitated from solution by 

 mercuric chloride with or without acetic acid, neutral lead acetate or 

 basic lead acetate, or uranium nitrate and acetic acid. 



Acids and Alkalies. 



As alkalies (KOH or NaOH in small, NH4OH in greater concen- 

 tration) precipitate the Mg of sea water, this salt should be removed 

 from a crude solution of luciferin and luciferase before studying the 

 precipitating effects of the substances. This can be done by the addi- 

 tion of a small amount of sodium pyrophosphate which forms Ca 

 and Mg pyrophosphates insoluble in water. The precipitates are 

 removed by filtration and the photogenic substances are found un- 

 harmed by the addition of pyrophosphate. 



Neither luciferin nor luciferase is precipitated by addition of 

 dilute NaOH or dilute NH4OH to their crude solutions, first rendered 

 free of Ca and Mg. 



Dilute acetic acid added to luciferase solution gives a fine precipi- 

 tate which is filtered off and washed with running water for 24 hours. 

 It does not dissolve completely in water and gives only a faint light 

 with luciferin. The precipitate is probably a mucin and carries down 

 some adsorbed luciferase. The filtrate is perfectly clear, gives no 

 further precipitate (sometimes a slight cloudiness on standing) with 

 acetic acid, but a bright light with luciferin. The addition of slightly 

 more acetic acid results in a clear filtrate giving no light with excess 

 luciferin. The precipitate on the filter does give a faint light with 

 excess luciferin but appears to be injured by the acid. 



Saturation with CO2 causes a precipitation in crude luciferase solu- 

 tion, but the filtrate gives a brilliant light with luciferin. 



