in molecular proportions, gave a gummy mass. This was dissolved in a little alcohol, and ether added until no more solid was precipitated. On crystallizing from a mixture of alcohol and ether, colorless plates, melting at 205°, were obtained. The analysis showed that this material is a pseudophenylethylenephenyldithiobiuret: Metaxylylene Thiocyanate, CH,(CH,SCN),, from metaxylylene bromide and potassium thiocyanate, forms colorless prisms, when crystallized from alcohol, melting at 160°-161°. A nitrogen determination gave: Nitrogen.... Calculated for 12.72 Found. 12.74 The crude product of the action of thiobenzoic acid on this substance was a varnish from which nothing solid was obtained. Thiobenzoic acid both with 1,2-propylene dithiocyanate, and 1,2,3tripropylene thiocyanate also gave thick oils which were not further examined. Benzal chloride and potassium thiocyanate, in alcoholic solution, gave a mixture of benzaldehyde and ethyl thiocyanate. Methyldibromhydrocinnamate and Potassium Thiocyanate.-In the introduction it was mentioned that certain 2,3-dibromides react with potassium thiocyanate with the removal of bromine and formation of unsaturated compounds along with pseudocyanogensulphide. This peculiar reaction is well illustrated by the behavior of the dibromide obtained by adding bromine to methylcinnamate. Fifty grams of the dibromide were heated for eight hours with 40 grams of potassium thiocyanate, and 60 cc. of alcohol. In fact on simply mixing in the cold a yellow precipiThis was extracted with water, alcohol, and carbon disulphide and then a nitrogen determination gave 24.65 per cent., while the analyses of various pseudocyanogen sulphide preparations, made by Goldberg, gave 22 to 27 per cent. nitrogen. On the other hand isopersulphocyanic acid contains 18.6 per cent. nitrogen. tate formed at once. The alcoholic solution was evaporated and the residue washed and taken up in petroleum ether, which left a small amount of substance undissolved. On evaporating, crystals sep arated melting at 33°, the melting-point of methyl cinnamate. This product was then distilled, and the boiling-point also agreed with that of methyl cinnamate. The yield after all this treatment was found to be 15 grams or 60 per cent. of the calculated. The dibromide from 2,4-dinitrostilbene (15 grams), when boiled with alcoholic potassium thiocyanate, gave 6 grams of pure 2,4-dinitrostilbene or 64 per cent. of the calculated. The dibromide from the nitrile of phenyl cinnamic acid (60 grams) gave 24 grams of the unsaturated product or 70 per cent. of the calculated. These yields do not represent the total amount of unsaturated material formed, since no special effort was made to obtain the entire amounts. NEW HAVEN, CONN., February 10, 1902. LIQUID MIXTURES OF MINIMUM BOILING-POINT. BY CLIFFORD D. HOLLEY. Received January 24, 1902. N 1899, Dr. Garnett Ryland' reported the results of an investigation of 80 pairs of the more common liquids. He found that 45 furnished mixtures which distilled in the same proportions with a constant boiling point below the boiling-points of the constituent liquids; one which presented no relative depression or elevation of the boiling-point; and 3 which were of an uncertain character. During the same year, E. F. Thayer' and J. K. Haywood investigated several of the same mixtures, but instead of following the method of Ryland, and determining the minimumpoint by repeated distillations, they determined the boiling-points of several mixtures of the liquid constituents, and plotted the resulting boiling-point curve. From a comparison of the two methods it is seen that the proportion in which two liquids give a minimum point on the boiling-point curve is the same in which they distil with a constant boiling-point which lies below that of either liquid constituent, and the boiling-points are the same in both cases. But little having been done along this line during the past two years, it seemed desirable to add to our knowledge of such phenomena, and continue the investigations of such systems as would be likely to furnish mixtures of minimum boiling-point. 1 Am. Chem. J., 22, No. 5. 2 Jour. Phys. Chem., 2, 382; 3, 32. 3 Ibid., 2, 317. In this paper are presented the results obtained with amyl compounds as one of the liquid constituents. The boiling-point method was chosen as the more preferable, as in the distillation of bromides and iodides the formation of tarry residues towards the close of the distillation renders the thermometer readings inaccurate. A slightly modified form of Hite's apparatus was used. Instead of a differential thermometer, one of the ordinary type was provided. It was graduated to fifths of a degree centigrade but with a scale so large that twentieths could be readily estimated. A weighed amount of the lower boiling constituent was introduced into the bulb of Hite's apparatus, boiled for several minutes and the boiling-point and barometric pressure recorded. Weighed amounts of the other constituents were added, the successive boil ing-points noted, and this procedure was continued until the liquids were present in nearly equal proportions. The flask was then emptied and the process reversed, weighed portions of the first being added to a weighed amount of the second constituent. The results obtained are shown in the form of a plot. No corrections were applied to the curves because of variations of barometric pressure, as the error thus introduced is believed to be inappreciable. The liquids used were purified by redistillation, usually the first and last fourth being rejected. The portions reserved distilled at a very nearly uniform temperature. In experimenting with mixtures of amyl iodide the bulb of Hite's apparatus was covered, and the investigation carried on in very subdued light, but even with these precautions the mixtures were noticeably colored towards the close of the operations from the separation of free iodine. Per cent. No. TABLE II.-ISOBUTYL ALCOHOL AND AMYL, BROMIDE. Isobutyl alcohol. Amyl bromide. Per cent. 100.00 Barometer. Temperature. C. mm. Table I. Amyl Alcohol and Amyl Bromide.-In the accompanying plot the left-hand ordinate represents 100 parts amyl alcohol. Amyl bromide (117.9°) and amyl alcohol (129.0° C.) furnish a mixture with a minumum boiling-point of 116.15° C. in the proportion of 12.7 parts amyl alcohol, and 87.3 parts amyl bromide. The minimum point is definitely defined. The first additions of amyl alcohol cause a rapid lowering of the boiling-point followed by a gradual rise until the maximum is reached. The curve exhibits a distinctly wavy tendency. Table II. Isobutyl Alcohol and Amyl Bromide.-Isobutyl alcohol (105°) and amyl bromide (118.1°) in the proportion of 63.6 parts isobutyl alcohol to 36.4 parts amyl bromide, gives a mixture having a minimum boiling-point of 103.4° C. The major portion of the curve is very flat, and the minimum point is not sharply marked. From the curve it is seen that isobutyl alcohol can be diluted with amyl bromide until it contains nearly 43 per cent. of |