E. NEWTON HARVEY 289 



or luciferase. Luciferin is not, but luciferase is injured by an excess 

 of dilute acetic acid. 



Dubois^ reports that Pholas luciferin is not precipitated by car- 

 bonic acid in neutal solutions or by acetic acid except in presence of 

 neutral salts and that it forms an insoluble alkali albuminate with 

 NH4OH. The latter is possibly a Mg(0H)2 formed from the mag- 

 nesium in the luciferin solution. 



Adsorbents. 



Proteins are usually separated from their solutions by one or an- 

 other of the following methods: heat coagulation (in trace of acid); 

 precipitation by alcohol or acetone (in large excess) ; precipitation by 

 heavy metal salts (basic lead acetate, HgCh and acid, uranium acetate 

 and acid, etc.); alkaloidal reagents (phosphotungstic, tannic, picric 

 acids, etc.); salting out (by MgS04 and acid, (NH4)2S04, etc.); diges- 

 tion by proteolytic enzymes; adsorption (by chloroform, toluene, 

 Fe(0H)3, 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 pre- 

 cipitates. Their complete adsorption is usually merely a matter of 

 obtaining sufficient adsorbing surface area. For this reason com- 

 parative studies on adsorption of different materials are difficult to 

 carry out because we cannot be sure of uniform surface area. How- 

 ever, it may be of interest to record a few of the experiments on 

 adsorption. 



A neutral dilute solution of luciferase was found to be completely 

 adsorbed by bone-black, Fe(0H)3, AS2S3, infusorial earth (Si02), 

 talc, and kaolin; nearly completely adsorbed by asbestos, pumice, 

 CaCOs, and MgCOs; not nearly completely adsorbed by ground 

 glass, sulfur powder, gelatin or agar-agar threads, heat-coagulated 

 egg albumin, fresh precipitated caseinogen, cotton; or cornstarch. 



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. 



