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May, 19-w. ] V. S. RITREAU OF CHEMISTRY NOTES. 669 vapors coming off were conducted through a series of chambers, maintained at different temperatures. The least volatile chloroderivatives separated o'ut in the hotter chambers, whereas the more volatile benzoic acid collected in the colder chambers. THIS investigationwas undertaken to determine the cause of discrepancies between results obtained by different laboratories for the chlorine capacity of the same charcoals.To study the effect of temperature and humidity of the air stream with which the chlorine was diluted (usually I : IOOO), mixtures of known air, chl'orine, and moisture content were passed through the charcoal which was held in a glass chamber in a constant temperature bath. The chlorine and hydrochloric acid in the outgoing gas were determined from time to time.In the particular series of charcoals studied, the variation in chlorine-absorbing power between different charcoals was greater than would result from any a,ttainable variation in humidity, and the order of the charcoals with respect to absorptive power is not the same as that with respect to apparent density.The duration of complete chlorine absorption (I ) increases more rapidly than the thickness of the layer of charcoal, (2) passes through a minimum at a temperature between 0" and I2.5O, and (3) at a humidity in the neighborhood of 50 per cent., and (4) is diminished by increasing the flow of air, the rate of supply of chlorine remaining constant.Reductions in pressure up to two feet of water (barometric pressured down to 71 cm. mercury) has little or no e#fect.For the charcoals studied : Below 12.5 o chlorine appeared beyond the charcoal before hydr'ogen chlorid; above 12.5~ hydrogen chlorid before chlorine, and the chlorine capacity of the charcoal was increased by one exposure to chlorine followed by heating in vacua to dull redness.

The necessity of blanching (scalding) vegetables to be preserved by freezing has been recognized since the report by Joslyn and Cruess (12) in 1929. The deterioration in flavor and color and the off-odors which develop in raw or under-blanched vegetables during freezing storage have been ascribed to the action of enzymes. I n many instances, the enzyme sytem or systems responsible for the deteriorative changes have not been identified. Nevertheless, it has become common practice t o use certain enzyme tests as indices of adequacy of heating in vegetables to be preserved by freezing. Some question still remains as to which enzyme best serves this purpose.Diehl and Berry (6) in 1933 stated that catalase activity served as an index of adequacy of blanching for peas and indicated that Alderman peas blanched for a time sufficient to destroy catalase activity retained satisfactory quality when stored at -5°F. (-20.6"C.). Later, Arighi, Joslyn, and Marsh (1) observed that catalase appeared to be quantitatively inactivated at a much more rapid rate than the enzymes concerned in the production of off-flavors in peas. In view of these findings, Joslyn (11) suggested that "the use of catalase activity as an index of adequacy of scald, particularly when the less reliable qualitative methods are used, is not a generally reliable method."Mergentime (20) and Balls (2) suggested that peroxidase activity might serve as an index of adequacy of heating. In a review paper, Joslyn (11) refers to earlier worE in which it was found that peroxidase activity more closely paralleled the formation of off-flavors in frozen vegetables than did catalase activity. However, he cautions that the correlation varied markedly with nature of the substrate used for detecting peroxidase activity.The first study quantitatively relating degree of peroxidase inactivation to quality retention in frozen vegetables was that of Masure and Campbell (18,28). I n this study, rapid methods were devised for the quantitative and semiquantitative estimation of peroxidase in various vegetable tissues. The latter method was developed for quality control in processing plants. These tests are based on an observed relationship between time required for appearance of color produced by the residual peroxidase in a filtered extract of vegetable in a guaiacol and hydrogenperoxide substrate, on the one hand, and retention of quality in the frozen product 011 the other.Specifications for the semiquantitative test were based on correlation 480

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