On the Chemistry of Light Production in Luminous Organisms. 103 
(NH,)2SO., ete.). (6) Digestion by proteolytic enzymes. (7) Ad- 
sorption (by chloroform, toluol, Fe(OH)s3, kaolin, and gum mastic). 
We have already noted the behavior of luciferase and luciferin 
toward the first six methods. Both of these substances can also be 
separated from solution by adsorption on appropriate material—in 
fact, they are rather readily adsorbed, especially by inorganic precipi- 
tates. Their complete adsorption is usually merely a matter of obtain- 
ing sufficient adsorbing surface area. For this reason comparative 
studies on adsorption of different materials are difficult to carry out, 
because we can not be sure of uniform surface area. However, it may 
be of interest to record a few of my experiments on adsorption. 
A neutral dilute solution of luciferase was found to be completely 
adsorbed by boneblack, Fe(OH)3, As2S3, infusorial earth (SiO,), tale, 
and kaolin; nearly completely adsorbed by asbestos, pumice, CaCQOs, 
and MgCOQ3; not nearly completely adsorbed by ground glass, sulphur 
powder, gelatin or agar-agar threads, heat-coagulated egg albumen, 
fresh precipitated caseinogen, cotton, or corn starch. 
A solution of luciferase shaken with five successive additions of fresh 
chloroform, until the chloroform is no longer emulsified but separates 
as readily as with water, is reduced considerably in luciferase content, 
but the luciferase is not completely removed by the chloroform. 
Neutral luciferin is completely adsorbed by boneblack, Fe(OH)s, 
kaolin, tale, and CaCO;, but not by many organic precipitates, as 
caseinogen, corn starch, or gelatin threads. There is the difficulty in 
studying adsorption of luciferin that oxidation may be accelerated by 
the presence of finely divided material. 
Luciferin can also be removed practically completely from solution 
by gum mastic according to the method of Michaelis and Rona! for 
removing proteins from blood serum. 
CONCLUSIONS. 
There seems to be very little doubt that luciferase is a protein or so 
closely associated with proteins that their removal destroys its charac- 
teristic properties. Thus, it is destroyed by proteolytic enzymes in 
neutral solution, completely precipitated by saturation with (NH,4) SOx, 
almost completely precipitated by MgSO, but not by NaCl or half- 
saturated (NH,4)2SO,, insoluble in all except aqueous solvents, readily 
absorbed by various inorganic precipitants, completely precipitated 
by phosphotungstic acid and basic lead acetate, and almost com- 
pletely precipitated by tannic and picric acids. The particular group 
of proteins to which it belongs may be arrived at by a process of exclu- 
sion. Some of the above characteristics, together with the fact that it 
will not dialyze and is coagulated on heating, are sufficient to exclude it 
1 Michaelis, L., and P. Rona, Biochem. Z., 1907, ii, 219; iii, 109; iv, 11. 
