THE ANALYST. 107 I N O R G A N I C A N A L Y S I S . Bromine and Alkali Hydroxides as a Test for Copper. D. Vitali. (Boll. Chin2. Farm., 1899, xxxviii., 665; through Chem. Zeit. Rep., 1899, 349.)-It is well known that when a solution of copper sulphate is mixed with potassium or sodium hydroxide, and an excess of bromine water is added, the original blue precipitate soon becomes black. This substance consists of copper dioxide; it evolves oxygen on warming or on treatment with sulphuric acid, and it gives off chlorine with hydro- chloric acid. The reactions proceed thus : CuSO, + 2NaOH = Cu(OH), + Na,SO,. 2NaOH + Br, = NaBr + NaBrO + 8,O. Cu(OH), + NaBrO = CuO, + H,O + NaBr.108 THE ANALYST. Other oxidizing agents, such as hydrogen peroxide or manganese dioxide, also convert copper hydroxide into dioxide.By evaporating 1 C.C. of a eolution containing copper to dryness, treating the residue with the yellow mixture of alkali and bromine, a black precipitate will be produced if the proportion of copper was 1 : 100,000. If the residue is more simply moistened with saturated bromine water and again dried, a black deposit is obtained, consisting of CuBr,, which becomes blue on being touched with water. This test will show copper in 1 C.C. of a 1 : 1,000,000 solution, and it is therefore more sensitive than sulphuretted hydrogen or potassium ferrocyanide. The black bromide is rendered more visible when moistened with strong sulphuric acid. Other metallic salts yield black precipitates with alkali hydroxides and bromine, e.g., Co,(OH),, Ni,(OH),, MnO,H,O.Mercurous salts give a yellow precipitate of mercuric oxide. Bismuth salts give a reddish-brown precipitate of Bi,O,. Lead salts in the cold finally yield an orange-yellow precipitate of lead oxybromide, which changes into peroxide on warming. F. H. L. The Separation of Tungsten and Molybdenum. F. Ibbotson and H. Brearley. (Chem. News, lxxxi., 13-15.)-Two modes of procedure are recommended : (a) The tungsten and molybdenum are precipitated together by lead acetate, the precipitate washed slightly with hot, very dilute acetic acid and ignited. The ignited precipitate is then dissolved in concentrated hydrochloric acid, using about as many C.C. of acid as there are centigrammes of the lead salts. Two or three times the bulk of boiling water is then added, the solution boiled, allowed to settle, filtered by decantatiou through a small pulp filter, the precipitate redissolved in about half the quantity of acid previously used, reprecipitated with water, and filtered through the same pulp.The molybdenum is determined in the filtrate as PbMoO,. The greater the amount of acid used to dissolve the lead salts, the more water is required for the complete precipitation of the tungstic acid, and the greater the dilution, the greater the liability to contamination with rnolybdic acid. ( b ) When the quantity of tungsten is small in comparison with that of the molybdenum, the former is not completely precipitated. Under these circumstances the following procedure is recommended : A few drops of nitric acid are added to the hydrochloric acid solution of the lead salts, which is then evaporated to a pasty con- sistence.The mass is diluted with 200 to 300 C.C. of dilute hydrochloric acid (1 : 3), the solution boiled, and the tungstic acid filtered off. The precipitate adhering to the sides of the vessel can be removed by dissolving in a few drops of dilute ammonia, which may then be absorbed with a piece of filter-paper, and the latter ignited with the precipitate. H. H. B. S. Estimation of Tellurium Dioxide in Presence of Haloid Salts. F. A. Gooch and C. A. Peters. (Zeits. ayzorg. Chem., 1899, xxi., 405.)-Brauner has shown ( J . Chem. SOC. Trans., 1891, 238) that tellurous acid cannot be determined by oxidation with permanganate if it be dissolved in hydrochloric acid; and he has also stated that if the oxidation take place in sulphuric acid solution a small correction isTHE ANALYST, 109 necessary, which is not required when the oxide is dissolved in alkali.If, therefore, the tellurous acid is dissolved in sodium hydroxide, and if the final titration between the oxalic acid and permanganate is carried out under those conditions which are desirable to avoid the interfering action of hydrochloric acid-Le., presence of manganous chloride-tellurium dioxide can be accurately determined in the manner indicated, even if it be accompanied by chlorides. About 0.1 gramme of TeO, is dissolved in a little sodium hydroxide, and mixed with permanganate solution (standardized on ammonium oxalate) till it remains pink; the liquid is heated, and 5 C.C.more of 1 : 1 sulphuric acid than are needed to neutralize it are added ; excess of standard ammonium oxalate is introduced to destroy the higher oxides of man- ganese and the excess of permanganate ; and finally the excess of oxalate is titrated with permanganate. If the proportion of hydrochloric acid is quite small, e.g., such as is produced by the decomposition of the original tellurium chloride, addition of manganous chloride is not necessary; but it is better always to employ it (0.5 to 1 gramme), as the last titration can then be conducted in the cold. I n the presence of a bromide fairly satisfactory results can be obtained, provided that the excess of sulphuric acid is not greater than 5 C.C. of a 12-5 per cent. acid, that sufficient manganous chloride (0.5 to 1 gramme) is used, and that the liquid is titrated at ordinary temperatures.Themethod described by Norris and Fay (ANALYST, 1898, xxiii., 249) gives excellent results. Instead, however, of titrating the iodine liberated from the iodide and sulphuric acid by means of thiosulphate, it can be determined with decinormal arsenious acid, this modification possessing the advantage that the arsenic serves also to standardize the original permanganate used to oxidize the tellurium dioxide. About 0.5 or 1 gramme of potassium iodide dissolved in 100 C.C. of water is added to the alkaline solution of the tellurium, then standard permanganate is run in till the green colour disappears (about 30 C.C. of the decinormal liquid per 0.1 gramme of TeO,); next a few C.C.of sulphuric acid are added to clarify the liquid, and the free iodine is titrated in presence of potassium bicarbonate. I t is important to have a sufficient excess of iodide, and it is perhaps better to run in some of the arsenious acid before acidifying with sulphuric acid. All the examples quoted by the authors are reasonably satisfactory, and they agree closely with theory when the atomic weight of tellurium is taken at 127. F. E. L, The process is obviously not available in the presence of an iodide. Determination of Sulphur in Bitumens. S. F. and H. E. Peckham. (Journ. Amer. Chem Xoc., vol, xxi. [9], pp. 772.)-The authors have modified their deflagra- tion method by taking such an amount of the assay as will correspond to about (3.2 gramme of bitumen, and mixing it with 15 grammes each of pure, dry sodium carbonate and potassium nitrate, the mixture being then deflagrated in small suc- cessive portions in a %ounce platinum crucible at dull red heat. No blast lamp is necessary, the fusion being complete without ; the excess of flux reduces the violence of the operation and the risk of loss by spattering. The mass is dissolved by immersing the crucible in water over night, and the silica, iron, alumina and sulphuric acid determined in the solution in the usual manner. c. s.