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WallersUin laboratoriesA practical method is described for comparing the stability of bottled beers.This technique involves the precise control of filling operations, and the production of definite variations in air content as a basis for rotation and storage tests. In In the first paper of this series (this Journ., 1939, 253), a method for measuring the state of oxidation in beer, tho "Indicator-Time Test," was described in detail.A considerable body of literature has accumulated in the past few years on the general subject of oxidation in beer as related to its stability. It would be superfluous at this time to go beyond the mere statement of the fact that physical stability of beer is definitely impaired by contact with air. Such oxidation reactions are necessarily influenced by other factors; and the insta bility manifests itself in gradual changes in colour and taste, loss of flavour, and haze development.Any loss in colloidal stability of beer usually first appears as a chill haze. For this reason, where continual chill-haze obser vations can be made on beer which is initially chillproof, under conditions con trolled as to oxidation, any increase in chill haze can safely be accepted as representing tho increasing effect of oxidation. Ulti mately, of course, the haze due to oxidation and visible at first only at low temperatures becomes visible at room temperature also. Helm (ibid, 1936, 379), in comparing the stability of beer, employed shaking cabinets, and followed changes in turbidity by compar ing the appearance of the beer in bottles with suspensions of barium sulphate. In the present paper, the method used by us in studying oxidation stability will be described. Tho technique, as given below, was applied to determine the relative stability of differ ent beers when bottled and handled under controlled and experimentally varied con ditions. We have been able to draw certain conclusions regarding the relationship of Indicator-Time Test results to stability. Tho catalytic effect of metals and the in fluence of certain antioxidants on the oxida tion stability have also been studied. Ac cordingly, not only will the procedure be described, but some of the results which have been obtained along these lines will be presented. Description of the MethodThe basis for tho method is the quantita tive measurement in a practical way of the turbidity after icing of samples of beer under conditions which make the results statistically reliable: the use of a suffi ciently large number of bottles; strict control of air content; and adequately controlled experimental conditions in other respects.

Traces of copper in beers and ales act to accelerate oxidation changes which adversely affect flavor and shelflife of the packaged beverage. The brewing industry requires a simple, rapid, and precise method for the determination of these traces of copper. A colorimetric procedure has been developed which requires no ashing of the sample and yields results in about 1 hour. The reagent employed is zinc dibenzyldithiocarbamate, which gives a brownish, solvent-soluble, copper complex in strongly acid solutions of the sample. The colored solvent layer is separated and measured in a photometer. No interference is encountered from the metals normally present in beer.Good recovery of added copper is obtained. Routine