View Article Online / Journal Homepage / Table of Contents for this issue ANALYTICAL CHEMISTRY. 1049 Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. Analytical Chemistry. A Device for Preventing Over-Titrating, FERDINANDSCHULZ (Chem. Zeit., 1909, 33, 11S7).-In the liquid to be titrated is placed an open tube about 12-15 mm. in diameter, and the titration is carried out as usual whilst rotating the beaker. The column of liquid inside the tube has, however, not yet been acted on, so by using the tube as a stirrer, the two liquids mix and any over titrstion wili be again neutralised. The last drops of the volumetric solution are then added very cautiously. L. DE h View Article Online 1050 ARSTK. ACTS OF CHEMICAL PAPERS. Porcelain Gooch Crucibles with a Layer of Spoiigy Platinum. HENRIJ. F. DE VRIES(Chem. Weeeekblccd, 1909, 6, 816-818. Compare Abstr., 1907, ii, 504, 719 ; 1908, ii, 430, 534 ; Brunck, this vol., ii, S26).-A claim for priority. The crucible described by Brunck has been employed by the author for two and a-half years. The method of preparing the platinum layer is described. A. J. W. Detection of Traces of Chlorides in Gelatin. LUPPO-CRAMER (Zeitsch. Chem. Ind. Kolloide, 1909, 5, 249--250).--The smallest trace of chloride can be detected in gelatin if a 10% solution is dried on a glass plate, and a drop of 10%silver nitrate placed thereon. Sodium chloride present to the extent of 0.001% of dry gelatin gives a white ring, 1-2 cm. in diameter, round the drop. The reaction Ban be used quantitatively if standards asre made from chloride solutions and carefully wmhed gelatin. On exposing the gelatin film so treilted to light, the ring turns bluish-, and the colourless space under the drop reddish-yellow. This indicates that silver chloride is present in both, but in a finer state of subdivision in the latter. The author has shown that the thickening (" reifung ") of the haloid salts in a gelatin plate is due to excess of halogen, and not to excess of silver. The ring is formed where the diffusing colloidal silver chloride arrives at a region where halogen is in excess. G. S. W. The Presence of Iodate in Commercial Potassiuni Iodide. LAUNCELOTW. ANDREWS (J. Amer. Chem. Soc., 1909, 31,1039-1039). -The author states that the general belief as to the presence of iodate in commercial potassium iodide is not justified, and that if any is present its amount cannot exceed 20 parts per million. The blue colour which some samples give on adding starch paste and dilute Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. hydrochloric acid is not necessarily due to iodate, but may be due to traces of iron oxide or cuprous oxide in presence of dissolved oxygen. Potassium hydrogen tartrate in solutions free from air does not give the reaction with those impurities, and is therefore preferable to hydrochloric acid. A convenient arrangement for carrying out the test is described. L. DEK. Photo-electric Measurement of Small Ozone Concentra- tions. Efficiency of Goldstein's Ozonisation Process at Great Dilutions. WILHELMHALLWACHS (Ann. Physik, 1909, [iv], 30, 602--606).-1t is shown that small quantities of ozone can be esti- mated photo-electrically by reason of the large specific absorptive power of the gis for ultra-violet radiation of wave-length in the iieighbourhood of 258pp. For such measurements the pressure of the gas in t.he absorption tube should be of the order of 0.01 mm. of mercury. Attempts to prepare ozone from oxygen by Goldstein's process indicated that this process is ineffective at very low pressures. H. M. D. Bulb Trap for Nitrogen Estimations by the Methods of Kjeldahl and Others. FR. DUDY(Chem. Zeit., 1909, 33, 1158)- By using the following arrangement, all danger of any alkaline View Article Online ANALYTICAL CHEMISTRY. 1051 liquid from the distilling flask getting into the standard acid is avoided. A is a cylindrical tube of a suitable diameter. At a it has an opening of "1 mm., and at b, one of 5 mm. To the cylinder is sealed the funnel-shaped tube c, which has a diameter of about 5 mm. Bis the usual bulb. On account of the great width of the tube A, a wide piece of rubber, not too thin, is used to connect the tube to the distilling flask. L. DE K. Estimation of Total Nitrogen by the Rober Method. F. W. GILLand HARRYS. GRINDLEY(J. Amer. Cl~em.Xoc., 1909, 31, 1249-1252. Compare Sebelien, Brgnildsen, and Haavardsholm, this vol., ii, '757). - Kober (Abstr., 1908, ii, 776) has described a modifica- tion of the Kjeldahl method, in which the ammonia is expelled by adding excess of alkali, and passing a A current of purified air through the solution. Experi- ments have now been carried out which show that the process is well suited to the estimation of nitrogen in organic materials, except when magnesium and phosphorus are both present in comparatively large quantities. In the latter case, the total nitrogen can be accurately estimated if the solutions are kept warm during the passage of the current of air. E. G. Estimation of Nitrogen in Nitrates and Nitrites. VINCENTSCHENKE \Clmn. Zed., 1909, 33, 1203).-A rep17 to Mitscherlich (Abstr., 1909, ii, 614). Contrary to Mitscherlich s statement, the author remarks that nitrates may be completely Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. reduced in acid solution. L. DE E(. Detection of Nitrates in Presence of Oxidising Substances (Chlorates, Bromates) and Iodides and Bromides. 11. EMMANUEL POZZI-ESCOT(Ann. Chim. anaZ., 1909, 14, 413-414 ; Bull. Assoc. Chim. Sucr. Dist., 1909, 27, 367--368).-The solution containing the above salts is introduced into a distilling flask with a large excess of sodium hydroxide. The flask is fitted with a cork, through which passes a large tube bent at right angles. (If ammonium salts should be present, the ammonia should be completely expelled by boiling.) Two or three grams of zinc dust are added, and the whole is boiled gently, The vapours are received in a conical flask containing Nessler solution, and the least trace of nitrates will then be detected by the brown coloration. L. DE K. Irregularities in the Titration of Arsenic after Previous Dis- tillation. LEOPOLDBXANDT (Chem. Zeit., 1909, 33, 11 14-1 115).- The process generally used for the estimation of arsenic in iron ores or steel (conversion into ferric sulphate by evaporation with nitric and sulphuric acids, and distilling the dry mass with fuming hydrochloric acid with addition of ferrous sulphate) is attended with a number of View Article Online 10.5 2 ABSTRACTS OF CHEMICAL PAPERS. slight errors, which may, however, be readily avoided. No condensing apparatus should be used, but the delivery tube, carrying a bulb and drawn out to a narrow point, dips into a large beaker containing water, which completely absorbs the acid fumes, and, consequently, the arsenic chloride ; the beaker is kept cool by being placed in a larger beaker containing cold water. When distillation is finished, the contents of the beaker are neutralised with ammonia free from pyrrole ; sodium hydroxide cannot be recommended on account of such frequent impurities as nitrites, chlorates, etc. After adding solution of sodium hydrogen carbonate, the arsenic is titrated with N/lO-iodine, using 5 C.C. of a 2% freshly prepared starch solution as indicator; starch containingzinc iodide as preservative must not be used, as this causes precipitation of zinc arsenite. Pyrrole-free ammonia may be read.ily obtained by tinging ammonia with permanganate, and afterwards decanting from the deposit formed. L. DE K. Electrolytic Detection of Arsenious Oxide in Presence of Arsenic Acid. ERCOLECOVELLI (Chem. Zeit., 1909, 33, 1209)- Thirty C.C. of the liquid to be tested are mixed with excess of potassium hydroxide and placed in a U-tube, into the limbs of which are placed two platinum foils, which are connected with the poles of a Grove cell. In the cathode limb is suspended a strip of paper impregnated with silver nitrate, and if arsenious oxide is present, even in fractions of a mg., a decided brown coloration will be noticed in a time varying from a few minutes to an hour. Arsenntes are not affected. L. DE K. The Detection of Arsenic Acid in the Presence of Arsenious Acid by means of Magnesia Mixture. OSCAR LUTZand R. SWINNE(Zeitsch. ccnorg. Chern., 1909, 64, 298-30 l).-Arsenious acid has been stated to give a magnesium salt which is not readily separated Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. from the arsenate. Experiments with solutions of different concentrations show that a qualitative or quantitative separation is not possible, although the precipitation of the arsenite is greatly hindered by the presence of large quantities of ammonium salts. Under these conditions, however, the precipitation of the arsenate also becomes incomplete, C. H. D. Analysis of Orpiment. M. CAFFIN (Collegium, 1909, 26, 225-22 6).-An application of Pearce’s method for estimating arsenic in minerals, The substance is fused with potassium nitrate and sodium carbonate, whereby sulphur is oxidised to sulphuric acid and arsenic to alkali areenate. The solution is made up to a convenient volume, the arsenic precipitated and colle’cted as silver arsenate, redissolved, and titrated with ammonium thiocyanate. Sulphur is estimated as barium sulphate in a different portion of the original solution. F. M. G. M. Modiilcation of the Reduction Process for Copper Spirals Used in Organic Combustions. ADRIANOOSTROGOVICH (Chem.