Effect of electrodialysis using ion-exchange membranes on the viability of bacteria was investigated. Overnight cultures in peptone water of Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Salmonella heidelberg, Proteus vulgaris, and Pseudomonas aeruginosa, and suspension of Bacillus subtilis spores were passed through a chamber of the apparatus with ion-exchange membranes at a constant speed. Bactericidal effect of such electrodialysis was markedly influenced by the current density and by the velocity of flow of bacterial suspension passing through the chamber. Higher bactericidal effect was obtained at higher current density and lower velocity of flow. No viable bacterium was observed at current density of 1.53 A/dm² and flow rate of 7 ml/min. Electron microscopic studies showed atrophy of the treated cells, and a distinct decrease of nitrogen and phosphorus contents was observed in the treated cells compared with that of the intact cells.

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A new spectrophotometric method for the determination of tin in canned food is proposed. A small amount of tin (IV) can be selectively extracted into nitrobenzene, when a moderate amount of tris-(1, 10-phenanthroline)-iron (II) chelate cation and a large excess of oxalic acid are contained in the aqueous phase. Thus, tin (IV) can be determined spectrophotometrically by measuring the absorbance of the extract at 516 mμ. To obtain optimum conditions for the determination of tin in canned foods, various factors were examined. A maximum extraction is obtained at pH 0.8-1.8, when an excess of at least 30-fold molar amount of the phenanthroline-iron (II) chelate and 1000-fold molar amount of oxalic acid to that of tin are present. Possible composition of the extracted species is suggested to be [Fe (phen.)₃]²⁺[Sn (C₂O₄)₃]^2-. Beer's law is obeyed up to about 60 μg of tin in aqueous solution. The effect of several ions on this method was examined. Satisfactory results were obtained by applying the proposed method to the analysis of tin in several canned foods.

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A mixture of Tween 80 and sodium salicylate was used as a reagent for the estimation of fat content in various kinds of milk products, and the results obtained were compared with those obtained by official methods. The method presented was shown to be more favorable than the official methods in its simplicity and rapidity. The results obtained in raw milk, concentrated milk, and coffee milk were satisfactory and statistically no significant difference was seen between this method and official method at the 0.01 level. Furthermore, the mechanism of separation of fat by this method was discussed.

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For the estimation of fat content in ice cream, the detergent method using Tween 80 with sodium salicylate was described. Fat content (F %) in ice cream is given by the following formula : F (%)=(0.1125×f)/W×100 where f is the fat content (%) in butyrometer and W is the weight of ice cream used. The results obtained by this method was found to agree approximately with those obtained by the Rose-Gottlieb method.

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The detergent method using Tween 80 with sodium salicylate was applied for the estimation of fat content in condensed milk and powdered milk. This method was found to be more useful than the official method.

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Effect of food dyes on the amidase activity of trypsin was examined by using a synthetic substrate, N^α-benzoyl-L-arginine amide. Xanthene dyes strongly inhibited the tryptic activity, as shown previously in the case of hydrolysis of casein. The effects of xanthene dyes including fluorescein and its lower halogenated derivatives were also examined. From the experimental results, it was found that the extent of inhibition becomes stronger in the following order : fluorescein, 2', 7'-dichlorofluorescein<4', 5'-diiodofluorescein, 4', 5'-dibromofluorescein<eosine<3, 4, 5, 6-tetrachlorofluorescein<erythrosine<phloxine<rose bengal. It seems that the extent of inhibition is related to the number and position of halogen atoms on the structure of xanthene analogs. From Lineweaver-Burk's plots, xanthene dyes exhibited non-competitive inhibitions. Ki values of these dyes were 4.7. 0.7, 0.4, 0.1, and 0.9 mM, respectively, for eosine, erythrosine, phloxine, rose bengal, and 3, 4, 5, 6-tetrachlorofluorescein.

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A new analytical method for the determination of ²²²Rn in air was studied. The method was based on the separation and determination of daughter ²¹⁴Bi which was in radioactive equilibium with ²²²Rn and the procedure was as follows. The air was sampled in a 5 liter round-bottomed flask, then 250 ml of Bi and Pb carrier solution adjusted to pH 1.0 with nitricacid was added, and the air-borne ²¹⁴Pb and ²¹⁴Bi, the daughter products of ²²²Rn, were absorbed in this solution by standing and shaking 5-6 times. ²¹⁴Bi in the solution together with Bi carrier was extracted by shaking with 1% cupferon solution and chloroform, re-extracted with 25% sulfuric acid, and precipitated by the addition of 10% sodium sulfide solution. The precipitate was dried and radioactivity of ²¹⁴Bi was measured with a low background gas-flow counter. The radioactivity of ²²²Rn can be calculated by the equations 1 and 2 shown below. [numerical formula] Where NBi is radioactivity (dpm) of ²¹⁴Bi at the time of separation of ²¹⁴Bi from ²²²Rn, t₁ is the time (min) from the separation to the beginning of measurement, t₂ is the time (min) from the separation to the end of measurement, f is the counting efficiency of ²¹⁴Bi, and A is the total count of ²¹⁴Bi in t₂-t₁. [numerical formula] Where NRn is the radioactivity (dpm) of ²²²Rn at the time of air sampling, t is the time (days) from the sampling to the separation of ²¹⁴Bi. The sensibility of this method was 5×10^-12 Ci ²²²Rn/liter of air, so that this method would be available for the determination of ²²²Rn in air in places such as the bath room of radioactive spa where extraordinary high content of ²²²Rn is expected in air. Using the above method, determination of ²²²Rn content in air was carried out at Misasa and Masutomi spa areas where many natural radioactive fountains are distributed. The ²²²Rn concentration in outdoor air was very low in both spa areas, while the air in bath room showed high concentration of ²²²Rn in both spa areas. The mean value of ²²²Rn content in air of three bath room were 42×10^-12 Ci/liter at Misasa and 13×10^-11 Ci/liter at Masutomi. These ²²²Rn contents are 13 and 4 times higher, respectively, than 1/30 of the "maximum permissible concentration in air"for occupational exposure recommended by ICRP.

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Chromium (III) acetylacetone complex is formed when chromium (III) is refluxed with and excess of acetylacetone at pH 6, and the complex can be quantitatively extracted with methyl isobutyl ketone. On the basis of this result, chromium (III) can be sensitively determined by atomic absorption method. This method, used for fuel-lean acetylene-air flame, is not interfered by iron, or by cobalt, nickel, aluminum, vanadium, titanium, or cyanide. Chromium (IV), can be determined by this method after being reduced to chromium (III) by hydrogen peroxide.

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The modified Henneberg-Stohmann method for determination of crude fibers was simplified as follows. The use of linen, copper net, sintered glass filter, and electric oven was eliminated. Filtration was made only once. In this simplified method, crude fibers are boiled with 1.25% sulfuric acid, 6.43g of solid sodium hydroxide is added in small portions to the boiled solution to bring the concentration of sodium hydroxide to 1.25%, and the solution is boiled for 30 minutes. The boiled solution is filtered through a Gooch crucible, and residue on the crucible is ignited on a direct flame until the dark colour becomes white. Removal of fat with ether is usually not necessary. The time of experiment is markedly shortened and the resultant values were almost the same as that by the usual method.

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In order to determine the amount of carbon monoxide in cigarette smoke, examination was made on how to dilute cigarette smoke with air to 50-fold dilution, and the amount of carbon monoxide in the diluted smoke was determined by the test tube detector of Kitagawa's method. This method may be the simplest and most practical because the values obtained were very close to that of Mumpower and others who had employed gas chromatography to estimate carbon monoxide in cigarette smoke. This apparatus is compact and portable, and the whole determination requires only five minutes. Since the moisture content of cigarettes had little or no effect on evalution of carbon monoxide, as was proved by Mumpower, examination was made on relationship between carbon monoxide content and some other factors.

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