360 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS and sintered disc types tend to become clogged with the precipitated sil,rer chloride and consequently give false readings. APPLICATIONS OF FLAME PHOTOMETRY 1. Sulphate The familiar gravimetric method for sulphate can be applied to deter- gents, but it is very tedious because both surface active matter and silica must be removed before the barium sulphate is precipitated. A rapid method of relatively low precision has been developed •ø'n in which barium sulphate is precipitated, dissolved in EDTA and determined by flame photo- metry, using the E.E.L. Flame Photometer. This is a low-sensitivity in- strument which uses filters to select wavelength, and a low flame temperature to minimise interferences. This means that it is not really suitable for the determination of metals other than the alkalis and calcium, which are easily stimulated and give strong radiations. It has, however, been found possible to determine barium, using much higher concentrations than usual (several hundred parts per million as against the usual ten or twenty). A sample of the detergent containing 0.25--0.50 g of sulphate as SO• • is dissolved in water. Excess hydrochloric acid is added and the surface active substances are extracted with ether. The aqueous layer is diluted to 250 ml and mixed. A 5 ml aliquot is pipetted into a 10 ml centrifuge tube, and a 5 ml aliquot of the standard (sulphuric acid solution containing about 0.2% or 2000 ppm of SO• • and accurately standardised) into another. 5 ml of 1% barium chloride solution is added to each tube. After mixing, the precipitates are centrifuged out and washed twice with water to remove sodium ions, which cause serious interference. They are then dissolved in 1 •o E.D.T.A. solution made alkaline with ammonia, and diluted to exactly 10 ml still in the tubes, with the same reagent. The filter used in the flame photometer is a Wratten 65A, which transmits the barium line at 493 m•. The ammoniacal E.D.T.A. is used to set the zero, and the treated standard to set the galvometer to full scale deflection. The test solution is then read. The concentration of sulphate ion in the detergent is given by scale reading x standardisation factor on H2SO• % SO,F = 2 x weight of sample The calibration curve for sulphate is linear to at least 1000 ppm. The precision is about 4-2% of the concentration found for a scale reading of 50, or 4- 0.4}/0 if the sodium sulphate content is 20%. This is poor compared with the gravimetric method, but a complete analysis takes only about 45 minutes instead of several hours.

SOME ASPECTS OF THE ANALYSIS OF HOUSEHOLD DETERGENTS 361', 2. Phosphate and borate It has recently been found that phosphate can be determined with the E.E.L. flame photometer, by measurement of a so far unidentified radiation in the region of 625 ms. For the analysis of detergents it is necessary to remove sodium ions by ion exchange. The method is not fully developed,, but in one experiment the P205 content of a detergent powder was deter- mined in 20 minutes and the result agreed well with that found by volumetric analysis. Boron can be determined by flame photometry, by measurement of any- of several oxide bands. Both sodium and phosphorus obliterate the radiation, and this interference is avoided by blowing the air supply to the instrument through an acidified methanolic solution of the detergent, and feeding the resulting mixture of air, methanol and methyl borate directly into the flame. This too is not fully developed, but it appears possible to, carry out a quantitative analysis by this means. (Received: 18th April 1962), REFERENCES Heirlet, C. Analyst 83 223 (1958) Blakeway, J. M. and Thomas, D.B. J. Chromatography 6 74 (1961) Holness, H. and Stone, W.R. Analyst 82 166 (1957) Holness, H. and Stone, W.R. Analyst 84 392 (1959) Epton, S.R. Trans. Faraday Soc. 44 226 (1948) Burr, T., Oliver, J. and Stubbings, W.V. J. Soc. Chem. Ind. London 67 45 (1948) Cullum, D.C. Proceedings of Third World Congress on Surface Activity (] 42 {1960), Cullum, D.C. and Thomas, D.B. Analyst 85 922 (1960) Cullum, D.C. and Thomas, D.B. Anal. Chim. Acta 24 205 (1961) Cullum, D.C. and Thomas, D.B. Analyst 84 113 (1959) Cullum, D.C. and Thomas, D.B. Analyst 85 688 (1960)