The only attempt thus far to determine the effeet of temperature on the rate of destiHu-tiou of aneurin is that of Riee and Beuk (1945), wlio studied the rate of destruction of aneuriu in pork at temperatures from 121° 0. to 49° C. Tlicy show a doviaiinii ffom the Arrhcuins etiuation (whieh relates lop; /.• and 1/T) below 77" C. which could bo related to enzyme activity. It has been shown iti the earlier papers of this series that the effect of various faetors on the rate of destruction of aneurin can be motlifled by the eleeti'olytP system, i.e. by the various buffer solutions used to establish the pll, and, consequently, the effect of temperature on the reaction velocity of aneurin (iestructioii has beeu studied in three different buffers. This work thus forms a continuation of the earlier investi{?ations but opportunity was takeu to determine whether there was any deviation from the Arrhenius equation below 77° C. in the absence of biological materials.Tho simplest method of studyiuf; buffer solutions at temperatures «;reater than 100° C. was thotight to be the use of sealed ampoules in whiv^h the solution under investigation could be heated iu an oil hath. When this procedure was adopted with the phosphate buffer, which was studied first, the anomalons results which were obtained led to the discovery that oxygen was capuhle of accelerating the rate of destruction of aneurin, though to different oxtents in different buffer solutions. Thus, in ypt another connection the importance of tlie electrolyte system is apparent. EXPERIMENTAL. Beagenis.The preparation of reagents was carried out in n similar manner to that used in earlier pnpers of this series (Farrer, 1947(Farrer, .i, 1947.Buffer aaJtg. The following solutions were made from A.R. reagenta and distilled water and purified by the CaCOa nbaorption method of Stout and Arnon (1939): 0-5 M Na2lTPO4; potassium hydrogen phtlialate, KHoPO, (0-5 M with respect to each salt). After filtriitioii. the COj was removed Iiy Iioitiiig followin}; the acidification of the fioliition with fiN ITCl (q.v.) He adjustment of the volume was carried out with twice distilled water after the solution had cooled.