A method for the determination of cadmium in bone by the flameless atomic absorption spectraphotometry was studied. Because calcium and phosphorus in the bone digested solution interfered with the determination of cadmium, removal of these elements from the bone digested solution was examined. Calcium and phosphorus were removed from the bone digested solution, former as calcium sulfate with sulfuric acid and the latter as ammonium molybdophosphate with ammonium molybdate. Thereafter, cadmium was extracted with the system of diethyldithiocarbamate-methylisobutyl ketone extraction and the organic layer was applied to the flameless atomic absorption spectrophotometry. The recovery by this procedure was 70-80%, and 10 to 100 ng of cadmimm per g of bone was able to be determined.

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The protective effect of six selenium compounds (sodium selenite, sodium selenate, selenocystine, selenocysteamine, selenocystamine, and selenomethionine) on the acute toxicity of methylmercuric chloride on rats was compared on the basis of survival rate and body weight change. Distribution of mercury and selenium in the rat tissues 24 hr and 1 week after the simultaneous injection of methylmercuric chloride and various selenium compounds was determined by non-destructive neutron activation analysis. All of the six selenium compounds were found to have some protective effect on the acute toxicity of methylmercuric chloride. The protective effect of six selenium compounds decreased in the order of selenomethionine, sodium selenate, selenocysteamine, selenocystine, selenocystamine, and sodium selenite. Correlation between the distribution of mercury and selenium was rarely found in the animals given simultaneous injection of methylmercuric chloride and various selenium compounds. This result suggests that the protective effect of selenium is not due to the direct binding of methylmercury and selenium.

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Mercuric chloride or methylmercuric chloride was reacted with sodium selenite in the presence of bovine serum albumin (BSA) and reduced glutathione (GSH), and these reaction mixtures were injected into tail vein of rats. Distribution of mercury in the rat tissues 1, 4, 24, and 168 hr after injection of the reaction mixture was determined by atomic absorption analysis. These experimental results were compared with the distribution of mercury in rats given mercuric chloride or methylmercuric chloride with sodium selenite. Unusual accumulation of mercury in the liver and spleen was found in the group given the reaction mixture of BSA, GSA, GSH, sodium selenite, and mercuric chloride, and in those given mercuric chloride and sodium selenite. This result supports the presumption that colloidal mercuric selenide is formed in the blood by simultaneous injection, because liver and spleen have phagocytic cells that engulf colloidal foreign particles. The significant accumulation of total mercury in the brain was found in the group given the reaction mixture of BSA, GSH, sodium selenite, and methylmercuric chloride, and in the group given methylmercuric chloride and sodium selenite. This result suggests that the reaction of methylmercury with selenium occurs in blood by their simultaneous injection, and that the reaction product easily permeates the brain.

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In order to establish a simple method for the determination of phenols in river water and industrial waste water, conditions were examined for the reaction used for the determination of hydrogen peroxide ; the reaction using 4-aminoantipyrine, phenol, hydrogen peroxide, and peroxidase, and the following method was established. The sample water (200ml) is distilled, 50 ml of its distillate is placed in a 50 ml test tube with a stopper, and 2 ml of 1 M phosphate buffer (pH 7.25) containing 5 mg of 4-aminoantipyrine and 0.5 mg of an enzyme (horseradish peroxidase), and 1 ml of 0.3% hydrogen peroxide solution are added, and the mixture is incubated at 37° for 15 min in a water bath. The reaction mixture is cooled to 5° and absorbance of this colored solution is read at 510 nm. Recovery of phenol added to distilled water by this method was 98.9-99.7% and its coefficient of variation was 0.61-0.84%. Coloration rate of phenols by this method was compared with the rate by the ferricyanide method, using 52 kinds of phenolic compounds, and the total of coloring rate by the present method was higher than that by the ferricyanide method. Correlation between the result of the present method and that of the ferricyanide method was examined with river water and industrial waste water collected in Wakayama city. Calculation of the linear regression line (y=1.119x+6.364) and correlation coefficient (r=0.943) indicated correlation between these methods.

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Effect of chlorella, which contained cadmium in its cells, designated as cadmium-containing chlorella, on rats was studied and the following facts were found : 1) When the cadmium-containing chlorella was administered to rats orally for 10 days, no significant difference in body weight from control rats was observed. However, in the case of repeated oral administration of cadmium chloride, the growth of rats was impeded significantly. 2) Cadmium concentration in organs of rats after administration of cadmium-containing chlorella for 10 days was significantly lower than that of rats administered cadmium chloride. 3) Cadmium concentration in blood after single oral administration of cadmium chloride (10 mg/kg) or cadmium-containing chlorella (10 mg/kg) was examined, and 119 ng/ml blood was found 3 hr after cadmium chloride was given but only little cadmium was detected in blood after cadmium-containing chlorella was given. 4) Urinary excretion of cadmium from cadmium-containing chlorella was significantly faster than that of rats administered cadmium chloride.

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A simple method was developed for the determination of chloroform in drinking water by using head space analysis. An suitable amount of sample water (V ml, usually 200 or 300 ml) is placed in 530 ml glass bottle. In order to remove residual chlorine, 0.5 ml of 0.1 N Na₂S₂O₃ solution is added and the bottle is closed with a double rubber stopper covered with aluminium leaf to prevent adsorption of chloroform on the rubber stopper. After shaking for some time, the sample water is maintained at constant temperature (t). Two ml of the overlying air is injected into a gas chromatograph, equiped with a flame ionization detecter, in a glass column (2m×3mmφ), packed with Silicone oil F-50 on 25% Chromosorb W. and concentration of chloroform (A ng/ml) in the overlying air is determined. Concentration of chloroform (C ng/ml) in the original sample water is caluculated from the following equation. C (ng/ml)=(A (ng/ml)×(530 ml-V ml)+A (ng/ml)×1/D_T×V ml)/V ml where D_T is the distribution coefficient (air/water) of chloroform at t. The distribution coefficient (D_T air/water) of chloroform changed with temperature (t), and experimental equation was D_T=0.0071t-0.015 (t, in the range of 14.5-30.0°). When 300ml of sample water was taken, the detection limit of this method was 1.5 ppb of chloroform. The recovery of chloroform in sample water was above 98%.

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Inorganic mercury (HgCl₂) in activated sludge, sewage, urine, and aqueous extract of feces was alkylated under irradiation. A considerable amount of alkylmercury was formed by irradiation of inorganic mercury solution containing acetic acid or propionic acid in the presence of ammonia but only a small amount of alkylmercury formed in the absence of ammonia. This fact suggests that aminomercuric chloride (HgNH₂Cl), formed by the reaction of mercuric chloride with ammonia, accelerated the photochemical alkylation of inorganic mercury. It was also found that creatinine, which was contained in sewage and urine, showed a photochemical alkylating ability but creatine, the open form of lactam ring of creatinine, did not show such ability.

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The effect of tin on body weight, serum glucose level, and calcium concentration in renal cortex was studied in rats that had ingested water containing 50 ppm tin for 100 days. The body weight and the wet weight of kidneys were significantly decreased by drinking of water containing tin compared with those of control rats. There was also a significant reduction of serum glucose and a significant increase in renal cortex after drinking of water containing tin. The present study suggests that the toxicity of tin cannot be neglected.

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A method for thin-layer chromatographic identification of streptomycin was investigated. To visualize streptomycin on a thin-layer chromatography plate, the periodate-thiobarbituric acid method was applied. Silica gel plate was better than ion-exchange cellulose or microcrystalline cellulose in giving a compact spot. Practical use of thin-layer chromatography for checking the purity of ³H-labeled streptomycin and preliminary studies on separation of streptomycin from biological material were also reported.

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The mercury mine in Uda Country was closed in February 1974. Change of mercury accumulation in Oikawa (Zacco platyps) that lived in Hono and Uda River was examined during 1974 to 1976. Mercury accumulation was high every year near the drain exit of the mercury mine and the junction of rivers. At the every investigation station, mercury accumulation was on the decrease every year, and the decreasing rate of mercury accumulation was higher near the drain exit of the mercury mine and junction of rivers. The decreasing rate of methylmercury was lower than that of total mercury.

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