It has been found that the texture of canned peas is affected far more by cation exchange with the various solutions with which they are in contact during the canning operation than it is by variations of pH level within the median pH range. By a suitable choice of alkaline reagents applied in a definite sequence, it is therefore possible to maintain a normal canned-pea texture while elevating the pH sufficiently to protect about 60 per cent of the chlorophyll of peas against conversion to pheophytin. A moderate elevation of pH level has an effect on flavor which most observers consider to be favorable. The flavor effect is a reversible function of pH level and appears to be largely due to shifts in the dissociation of those odoriferous natural constituents of canned peas which are weak acids or bases. CONVENTIONAL canning procedures change the color of peas and of other green vegetables from the natural green to what is commonly termed an "olive" color. Willstatter has shown that the natural green pigment is the same in all higher plants and consists of a mixture of chlorophyll A, CsiHrjOjNiMg, and chlorophyll B, CisHToOiNhMg.

It is quite apparent that the flavor deterioration which takes place during the unrefrigerated storage of canned orange juice is greater than that which is encountered during the similar storage of canned non-citrous fruit products. Observations made in this laboratory with canned Florida Valencia orange juice stored a t any temperature above 7O0F.(21"C.) may be described by saying that the predominant off-flavor which develops under such conditions is ' terebinthine " in character. The terebinthine factor is acrid and camphoraceous, and is often most clearly apparent as an after-flavor, perceived after swallowing the juice. Similar juice stored at temperatures which never exceed 70°F.(21"C.) also depart in time from a desirable fresh flavor, but in this case the off-flavor has a complex and variable quality which may be named "stale" for purposes of discussion, and which is conspicuous in such samples because a t the lower temperature the terebinthine factor does not become dominant. Such empirical observations indicate quite clearly that the over-all degradation in flavor during storage involves a large number of different chemical reactions, differing in regard to the temperature coefficient of reaction rate.It has been postulated in the past that flavor degradation is due to microbiological activity (30) o r to changes in nitrogen compounds (19), or to products resulting from a postulated initial oxidation of juice components. The primary oxidation products are not themselves off-flavored but are thought to constitute an unstable system which leads to the ultimate production, from the fatty components of the juice, of substances which impart to the flavor a rancid quality (20). It is probably fair to say that the proponents of these hypotheses were seeking explanations of the stale, rather than the terebinthine, flavor factors.

the course of a biological investigation, the need arose to determine calcium in certain tissues of the rat. In many instances, the amount of tissue available necessitated a method requiring not more than 5 or 10 gamma of calcium per determination.The technic of Miller and Kirk (S), based on the oxalatepermanganate volumetric method, was tried, but was discarded because of the difficulty in determining the end point in the titration. Lindner and Kirk (£) later surmounted the difficulties encountered in the earlier method by replacing potassium permanganate with ceric sulfate, which is added in excess to the calcium oxalate precipitate dissolved in dilute sulfuric acid. The ceric sulfate not reduced by the oxalate is then determined by titration with standard ferrous ammonium sulfate, using phenanthroline-ferrous sulfate as an indicator.