Investigations on the chemical composition of Baltic sea water in the spring 1966 (Summary): The ionic concentrations of the main components are investigated from 40 samples at 7 stations in the Baltic. Sodium and potassium with a Na+/cl and a K+/cl ratio of 0.5547 and 0.0206 respectively, show no deviation from the ocean ratio. The calcium content can be described as functions of chlorinity which differ for surface and deep water. The average value of the Mg+/cl ratio is 0.0672. Contrary to the calcium there is no statistical evidence for an excess of magnesium. All Cl-ratios of the investigated anions show deviations from the ocean ratios. The excess of alkalinity is larger than can be expected from the calcium anomaly; the mean value of the difference is + 0.15 meq./kg. The excess of the sulphate is indicated by the sol-/cl ratio of 0.1403 (water with Cl >4.5 °/oo) and 0.1410 (Cl >4.5 °/oo) respectively. The Br-/Cl value of most samples shows a negative deviation 0 from the ocean ratio. The equation for the bromide content is: Br [g/kg) = 0.000347 Cl °/oo 0.00036. The F-/cl ratio shows a clear dependence on 2 the geographical position and on the depth of sampling. Sometimes the d1fferences are as high as 2 x 10^-5. At 3 stations a fluoride deficiency can be observed
