In 35 healthy individuals, the number of amalgam surfaces was related to the emission rate of mercury into the oral cavity and to the excretion rate of mercury by urine. Oral emission ranged up to 125 micrograms Hg/24 h, and urinary excretions ranged from 0.4 to 19 micrograms Hg/24 h. In 10 cases, urinary and fecal excretions of mercury and silver were also measured. Fecal excretions ranged from 1 to 190 micrograms Hg/24 h and from 4 to 97 micrograms Ag/24 h. Except for urinary silver excretion, a high interplay between the variables was exhibited. The worst-case individual showed a fecal mercury excretion amounting to 100 times the mean intake of total Hg from a normal Swedish diet. With regard to a Swedish middle-age individual, the systemic uptake of mercury from amalgam was, on average, predicted to be 12 micrograms Hg/24 h.

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Urine samples that have been cold-digested by potassium permanganatesulphuric acid mixture overnight are analysed in apparatus consisting of an automatic sample changer, pumps for transferring the sample solution to a purgation tower and adding tin(I1) chloride solution, which reduces mercury(I1) to metallic mercury, and a spectrophotometer. The mercury vapour is liberated from the solution in the tower by a flow of nitrogen and then taken through the absorption cell in the spectrophotometer where the light absorption at a wavelength of 253.7 nm is continuously recorded. After completion of the purgation, the mercury-free solution is transported back to the original tube in the sample changer by reversing the pumps, and the next analysis is started. The mercury content in the sample is calculated from standard graphs drawn from results with known amounts of mercury. Sixty digested samples, each containing 1 ml of urine, are analysed in about 2 hours without any manual work or supervision. In each sample about 1 ng of mercury can be detected, but normally the working range for urine samples is 0 to 400 ng ml-l of mercury(I1). The analysis can be applied to biological or any other samples that can be digested in a similar manner.IN a previous paper,l one of us described a rapid method for the determination of mercury in digested urine, which was based upon the reduction of mercury(I1) to the metallic state by tin(II), followed by removal of mercury vapour by purging with air and cold-vapour atomic-absorption determination of mercury. The speed of analysis was fairly high, and the detection limit about 2 ng of mercury in a 1-ml urine sample.At present, there is a great demand for trace determination of mercury in large series of samples of water, food, urine, blood and organs. To reduce the cost of such analyses it is essential to find methods which can bring down the amount of work needed to a minimum. Therefore, we have worked out an automatic method for the determination of mercury in samples that have been wet digested. This method depends upon the same basic principle as * For particulars of Part I of this series, see reference list, p. 229.