In mice the oral LD50 values of aluminium chloride and aluminium sulphate were 0-77 ± o0I2 and o098 ± o0og g. Al/kg. (± S.E.) respectively.Mice and rats were fed on a normal diet containing about 170 p.p.m. of aluminium. Doubling this concentration caused a decrease in growth in the second and third generations of mice. A high intake of aluminium sulphate (2,835 p.p.m.) caused a 20-fold increase of aluminium retention in white rats. Aluminium accumulated in various tissues, especially in the skeleton, liver, and testes. A high rate of intake (2,665 p.p.m.) caused a negative phosphorus balance in the rat, with an increased output of phosphorus in the faeces. The lower absorption of phosphorus was also demonstrated with Na2H32PO4. Chronic and acute poisoning by aluminium chloride caused, after intraperitoneal Na2FP2PO4, decreased incorporation of 32p into the phospholipids and nucleic acids of various tissues in the rat. It also caused a fall in the adenosinetriphosphate acid-levels in plasma, and a rise in the adenosine diphosphate level.The results suggest that, the toxic effects of aluminium salts result both from decreased absorption of phosphorus and from interference with phosphorylation processes in the tissues.

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Rats given 4 mg. fluoride/kg./day for eight days excreted more calcium and phosphorus and retained less than the controls. In bone ash from rats given different fluoride doses for 40 days the calcium and phosphorus were maximal after a total dose of about 250 ,tg. fluoride/rat, but fell to subnormal levels after higher doses. The calcium and phosphorus levels in bone ash from rats given 750 pg. fluoride/day fell with the duration of treatment.Rats exposed to 9-4-II .7 ,ug. hydrogen fluoride/litre air absorbed fluoride rapidly, as shown by increased urinary excretion, by changes in the enamel of the teeth, and by rising fluoride levels in the teeth and bones. Radiological examination, however, showed no gross changes. Urinary excretion increased with exposure time.Fluorine compounds are widely used in industry, e.g., in aluminium and glass manufacture. The gaseous or solid fluorides released in these processes affect both the manufacturing areas and their surroundings.There is no general consensus of opinion on the influence of high doses of fluoride on the metabolism of calcium and phosphorus, although most investigators find increased excretion of calcium, especially in the faeces. The interaction of fluoride and calcium ions explains, for instance, why the toxicity of fluorides is increased during growth, lactation, and pregnancy, as calcium requirements are higher during these periods.In this paper the effects on calcium and phosphorus retention of oral sodium fluoride and of inhaled hydrogen fluoride are presented. The work consisted of the estimation of calcium and phosphorus balance, and of retention by bone, and how it is affected by the duration of administration of fluoride and of the amount administered; and an estimation of the retention of fluorides in bones and incisor teeth after inhalation of hydrogen fluoride. Materials and MethodsRats These were of the Wistar strain and weighed 170-250 g. They were fed on the Larsen diet (Fabry, 1955) containing about 6,ooo p.p.m. of phosphorus and I I,000 p.p.m. of calcium. The rats were given drinking Reczived for publication July 7, I967.water ad libitum (distilled in balance studies). They were weighed daily and were kept in metabolic cages, five or six rats to a cage, except in balance studies when they were kept one to a cage.Effect of Dose Rate In the first series of experiments 77 rats, initial mean weight I70 g., were divided into ii equal groups. The control group received by probeper OS 0-2 ml. distilled water and the others received graded doses of sodium fluoride in 0-2 ml. distilled water. The experiment lasted 40 days.Effect of Duration of Experiment In the second series, 6o rats, initial mean weight 200 g., were divided into four groups. The control group received by probe per os 0-2 ml. distilled water. The second, third, and fourth groups received 750 ,g. fluoride as sodium fluoride daily for periods of 40, 6o, and I40 days respectively. At the end of the experimental period the levels of calcium and phosphorus in the bones were determined.Ba...