A procedure has been developed for determining calcium with glyoxal bis-(2-hydroxyanil) . In alkaline solution, calcium reacts with the reagent to form a red complex, which is stable in an aqueous alcoholic medium and has an absorption maximum a t 520mp. The colour obeys Beer's law in the range 0 to 4 p.p.m. of calcium, and no interference is encountered from up to 50 p.p.m. of magnesium.

The more commonly occurring metallic salts in industrial effluents are those of cadmium, chromium, copper, iron, lead, manganese, nickel and zinc, and their determination in concentrations as low as 0.1 p.p.m. is necessary. Various simple colorimetric procedures were tested, and the amount of interference caused by other metal ions was noted and, if possible, eliminated. As well as being suitable for measurement in photo-electric absorptiometers, the colours can be measured in visual colorimeters or by visual comparison with a row of standards in Nessler tubes.The method finally recommended is given in full only if it differs from published procedures; if a simple amendment suffices or if the published method is completely satisfactory, the reference to the original publication is considered sufficient. Methods published for cadmium,2 lead by the mono-colour dithizone procedure3 and nickel by dimethylgly~xime~ were found to be satisfactory for the types of sample concerned, and are not dealt with further in this paper.Procedures are recommended for chromium, copper, iron, manganese and zinc and, although the methods are not original, they are set out in some detail, as no one reference could be found to incorporate all the modifications required.

A rapid radiochemical method is described for determining radon in water, based on the equilibrium of bismuth-214 with its parent radon. This bismuth isotope is precipitated from solution by n-propyl gallate, with inactive bismuth as a carrier. The precipitate of bismuth propyl gallate is collected on a filter, dried, mounted anti p-counted on a conventional instrument. The lower limit of sensitivity is about 20 picocuries per litre when a simple Geiger assembly is used.The storage in polythene containers of water samples taken for analysis is not recommended, as this polymeric material can absorb radon gas from aqueous solutions.RADIOCHEMICAL DETERMINATION OF RADON VIA BISMUTH-214-THE radioactive disintegration products of natural radium are produced according to the decay scheme shown in Table I, the daughter nuclei being indicated in descending order. The minor branching at radium C by a emission to thallium-210 has been omitted from the Table, since 99.96 per cent. of the disintegrations are , & decays, the branching ratio being 2500 in favour of polonium-214.

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