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An electrochemical ion-selective electrode detector in conjunction with the gas chromatograph and the TCD in series is described and its operating characteristics are discussed. Under optimal conditions for resolution, mercaptans are absorbed in 1 . 10-4 mol l-1 AgNO3 absorption solution at a flow rate 1.2 ml min-1 and detected by Ag2S-solid membrane electrode. The detection limit 6 . 10-11 mol S calculated for propyl mercaptan is achieved, however, only in 1 . 10-5 mol l-1 AgNO3, where a poor resolution of mercaptane occurs. Other parameters affecting the separation and sensitivity are flow rate of absorption solution and geometry of the cell and of the absorber.

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The thermally initiated cyclocondensation of 1,3-dimethyl-4-alkylamino-5-nitrosouracils (I), giving rise to the 8-substituted theophyllines (II), was studied by DSC. The corresponding reaction enthalpies were determined for six derivatives of I.