216 Notes. NOTES. The Preparation of Ethyl p-lodopropionate. By JOHN W. BAKER. ETHYLP-chloropropionate (254 g.) was refluxed for 24 hr. with 350 g. of NaI in 300 C.C. of EtOH. The product was largely diluted with Et,O and the filtered solution washed with H,O Na,CO aq. and dil. Na,S,O aq. and dried. Fractionation gave (1) 20 g. b. p. up to 93'/20 mm. mamly impure iodo-ester and (2) 344 g. b. p. 85-95"/14 mm. of almost colourless iodo-ester. From the Na,CO extract approx. 25 g. of P-iodopropionic acid m. p. 80-82" after draining were obtained. The conversion is 92% and the yield of almost pure iodo-ester 81%. The ester condensed with ethyl sodioethanetricarboxylate to give an 80% yield of ethyl butane-app8-tetracarboxylate (Kay and Perkin J. 1906 89 1642 obtained an 85% yield).The author thanks the Royal Society for a grant.-T€IE UNIVERSITY, JXEDS. [Receiwd December 6th 1932.1 The Absorption Spectra of 2 2'-Dimethyl-and 2 2'-L)iethyl-~elenocarbocyanineIodides and of Methiodide. A Correction. By L. MARSHALL p-Dirnethylaminosty~ylbenzthiazole CLARK. THE two iodides have been examined by Dr. F. M. Hamer and Miss N. I. Fisher (this vol. p. 191) who inform me that the spectra of their products are different from those described by me (J. 1928 2313). I have therefore examined alcoholic solutions of my old specimens and of a new preparation of 2 2'-diethylselenocarbocyanine iodide kindly supplied by Dr. Hamer on a direct-reading Hilger spectrometer. From the results now obtained it is clear that the previously reported data are incorrect and that the error is due to a personal misunderstanding of entirely accurate photographs of the spectra supplied by Messrs.Ilfords Ltd. The wave-lengths of the absorption bands are as follows 2 2'-Dimethylselenocarbocyanine iodide A 570 pp ; 2 :2'-diethylselenocarbocyanine iodide A 570 pp ; pdimethylaminostyryl-benzthiazole methiodide A 516 pp.-[Received January 30th 1933.1 HENSTOCK. The Identification of Alcohols in Dilute Aqueous Solution. By HERBERT THE Schotten-Baumann reaction with certain modifications was found to be suitable for the purpose. 2&y0Aq. EtOH at 15" gives no yield of ester but does so at a lower temp. Menalda (Rec. trav. chinz. 1930 49 967) has described a similar phenomenon. If in conjunction with lowered temp.a salt is added prior to the p-nitrobenzoyl chloride the yield is further raised by an amount dependent on the nature of the salt. A solution of 2 g. IiOH and 1 g. NaOAcJ3H,O (or an equiv. molar quantity of other salt) in aq. alcohol of known percentage was cooled to -15",shaken with 1g. of p-nitrobenzoyl chloride for 1 min. cooled and shaken again. Another 1 g. of reagent was added and the process repeated. After dilution with 30-40 C.C. H,O and subsequent shaking the mixture was kept for 30 min. or until it became clear. The filtered ester was washed with H,O air-dried and recrystal- lised from suitably dil. alcohol. For concns. of alcohols below 29% one-half the wts. were used. M. p. of 76 Yield at -15" :( Yield at -15" % Yield at 15" Lowest % alcohol Alcohol.ester. with NaOAc. without salt. with salt. identifiable. Methyl ............ 96" 60 35.4 15.5 0-25 Ethyl ............ 57 35-2 10.0 0.0 1-00 n-Propyl ......... 32 32.3 32.9 25.8 0.50 isoPropyl ......... 55-5 19-4 0.0 0.0 1.50 n-Butyl ......... 35 33.3 22.2 29-6 0.25 isoButyl ......... 67 51-8 48-0 22.2 0-25 n-Amy1 ......... 54 37.0 -0.50 There is an optimum concn. for each salt KOH and alcohol corresponding to a max. yield of ester. Yields with other salts were sodium formate and propionate 26.4 n-butyrate 8.8,succinate 22.0 citrate 10-8 sulphate 29-3 carbonate 23-4 nitrate 17.6 chloride 14.6% and potassium acetate 11.7 propionate 3.5 n-butyrate 16-0 and succinate 6.1% from EtOH.-uNIVERSITY COLLEGE,EXETER.[Received hdarch loth 1932.1