The investigation of the equilibrium between 17-keto steroids, acetylene and 17-ethynyl steroids has afforded two possibilities for its analytical application. On the one hand, the 17-ethynyl steroids can be quantitatively converted into 17-keto steroids and the latter determined spectrophotometrically as their 16-glyoxalyl derivatives (Amax. = 294 nm, E = 10 700 and u = 1-1 per cent.). On the other hand, a t 0 "C the 17-keto steroid contaminants in 17-ethynyl steroids can be selectively determined on the same principle.These methods cannot be applied in the investigation of 3-keto steroids.THE introduction of the 17-ethynyl group into various steroid hormones greatly enhances their hormonal activity. The resulting "super gestogens" and "super oestrogens" can be used in very small doses, hence the micro-determination of these compounds is very important. Most of the existing micro-scale methods for the determination of 17-ethynyl steroids involve ultravioletl*2 and infrared3 spectrophotometric, colorimetric4-0 and fluorimetric6 procedures, which usually depend on other functional groups in the steroid molecule such as the a,p-unsaturated 3-keto group of the phenolic A-ring. These and many other methods of similar nature are very sensitive, but are not, however, specific for the ethynyl group, The specific determination of the 17-ethynyl group can be performed by argentimetricacidimetric * For details of Part XXIII of this series, see
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