19161 AGRICULTURAL CHEMISTRY — AGROTECHNY. 713 



On the mechanism of oxidase action, G. B. Reed {Bot. Gaz., 62 (1916), No. 

 1, pp. 53-6^, figs. 4)- — In connection with certain experiments tlie autlior has 

 observed that diffex-ent samples of colloidal platinum and silver (prepared by 

 passing a direct current between two electrodes of the metal under water) 

 behaved differently toward solutions of gum guaiac. The guaiac was in some 

 cases oxidized directly, while in others only after the addition of a peroxid. This 

 phenomenon suggested that samples of colloidal metal might contain different 

 proportions of oxygen, and further that the amount might be varied by suitable 

 treatment. The following experiments which prove the supposition to be cor- 

 rect are reported : 



A large platinum crucible with a surface of about 150 sq. cm. (al)out 23.25 

 sq. in.) was platinized in the ordinary manner, by making it a cathode in a 

 solution containing 2 gm. platinum chlorid and 0.16 gni. lead acetate in 60 cc. 

 water, until tlie surface was uniformly coated with a black deposit of colloidal 

 metal. It was then subjected te active hydrogen by making it a cathode in a 

 dilute solution of hydrochloric acid. The crucible thus treated when placed in 

 a solution of gum guaiac free from peroxid or any solution of potassium iodid 

 produced no oxidation. After subjecting the colloidal metal to active oxygen, 

 however, it produced rapid oxidation when placed in either of these solutions. 

 Although the reaction took place rapidly it was observed that only a very small 

 amount of material was oxidized. 



To determine whether only sufficient oxygen for a limited oxidation was 

 taken up by the platinum, the oxidation of formaldehyde to formic acid, which 

 is catalyzed by platinum black and which can be accurately and conveniently 

 measured, was undertaken. About 80 cc. of a solution containing 5/100-molar 

 NaOH and approximately 3/10-molar formaldehyde was placed in an open 

 beaker in a water bath maintained at a constant temperature of 30° C. The 

 platinum crucible was freshly platinized, exposed to active oxygen for five 

 nuinutes, and after being thoroughly washed introduced into the solution of 

 formaldehyde. The mixture was kept thoroughly stirred throughout the ex- 

 periment, and at frequent intervals 2 cc. portions were removed and titrated 

 with 5/100-molar hydrochloric acid. The amount of NaOH neutralized by the 

 formic acid generated in the reaction was thus obtained. The results are ex- 

 pressed graphically and support the supposition noted above. 



Other experiments in a study of the mechanism of the oxidation of formal- 

 dehyde to formic acid with platinum as a catalyst are reported. The results 

 show that in the oxidation of formaldehyde by hydrogen peroxid in the presence 

 of platinum black the platinum combines with oxygen from the hydrogen 

 peroxid as it combined with oxygen when subjected to anodic oxidation. This 

 compound of platinum then gives up its oxygen to the formaldehyde, producing 

 formic acid. 



From the results in general it may be concluded that " when colloidal plati- 

 num is introduced into a mixture of hydrogen peroxid and an oxidizable sub- 

 stance the platinum takes up oxygen from the peroxid, thereby forming a more 

 efficient oxidizing agent than the original hydrogen peroxid. The catalytic action 

 of the platinum in this case, that is its peroxidase action, therefore depends 

 upon its aptitude for forming unstable oxygen compounds when it is in contact 

 with hydrogen peroxid." 



Similar work with plant material is in progress. 



The ferments of pineapple juice, H. FouQXrf: (Compt. Rend. Acad. Sci. 

 [Paris], 162 {1916), No. 12, pp. ^33-435). — In the study reported the pineapple 

 juice was expressed as aseptically as possible, received in sterile flasks, and 

 allowed to ferment, some samples under anaerobic and others under aerobic 



