(a) A different correction, owing to the use of different samples of zinc and copper. The best method of obtaining the true end-point was found to be as follows: -: The indicator is a freshly prepared saturated solution of potassium ferricyanide in dilute sulphuric acid. A drop of the solution to be tested is mixed with the drop of indicator on a white tile, and if a blue colour is not immediately developed the drop is covered with a crucible to exclude light and dust, and allowed to stand for thirty seconds. If at the end of this time no blue colour is developed the titration is taken to be complete. It is necessary to wait the full thirty seconds, because in the very dilute state of the ferrous salt the colour only appears slowly. This method of procedure is unnecessary if the dichromate solution is standardised against known amounts of ferric iron, which are reduced with copper under conditions approximately similar to those which will obtain when an unknown amount of iron is being estimated. should be mentioned, perhaps, that great care must be taken in dealing with hydrochloric acid solutions, that the copper is perfectly clean, and not superficially oxidised. It Unless this is so more cuprous chloride will be formed than is equivalent to the iron present, and a high result will be obtained. The superficial layer of oxide is easily removed by boiling with dilute sulphuric acid and rapidly washing with distilled water. The iron solution to be reduced should then be added as quickly as possible. (b) Influence of Varying amounts of Acid on the Reduction.-Table II. shows the effect of varying the amount of hydrochloric acid. To secure accurate results the amount of free acid must not be greater than 25 cc. of acid of strength 1 to 2. Table III. contains a similar series of values obtained when sulphuric acid was used. The amount of acid has no effect on the value found. (c) Reduction of the Ferric Alum Solution.-Twenty cc. of the iron solution, when boiled for five minutes with copper and 15 cc. of HCl solution (1 to 2), required— Cc. K2Cr2O7 (1 cc. = 0.005482 grm.). Dilute HCl for washing 25.82 25.92 25.88 26.08 25'94 (Mean 25'93). Table IV. contains a summary of the determinations of the iron solution for purposes of comparison. The numbers are the mean values of the previous determinations. III. Estimation of Iron in Ores and Alloys. (a) Spiegeleisen.-The material was dissolved in nitric acid. In order to destroy organic matter potassium chlorate was added, and the solution boiled. The iron was then precipitated with ammonia, washed till free from chlorides, and dissolved in sulphuric acid. The results obtained appear in Table V. The corrections in the fourth column are for impurities in the zinc and copper. They were found by performing blank experiments, the details of which appear in Table VI. (b) Hamatite.-The finely powdered specimen was dissolved by digesting with concentrated hydrochloric acid and a little potassium chlorate. The results obtained appear in Table VII. The dichromate solution was standardised on re-crystallised ferrous animonium sulphate, which was oxidised and then reduced with copper in presence of hydrochloric acid. (c) Spathic Iron Ore.-The ore was dissolved by digesting with aqua regia. The results appear in Table VIII. It appears therefore that copper provides a convenient and easily handled reducing agent for ferric salts previous to their estimation volumetrically, provided that the precautions noted above are taken. My thanks are due to Mr. C. T. Heycock, King's College, for much advice and assistance during the course of the work. O. BRUNCK describes in the Zeitschrift für angewandte Chemie, 1907, xx., p. 834, a method for the quantitative determination of nickel with dimethylglyoxime. If a neutral solution of nickel salt be treated with an alcoholic solution of dimethylglyoxime a red crystalline precipitate is produced. The acid set free in the reaction, however, causes the precipitation to be incomplete, and it is necessary to add ammonia in order to get accurate results. The precipitate can be dried at temperatures above 100° C., formula C8H14N404Ni. Cobalt does not interfere, prowithout decomposition (it sublimes at 250° C.) and has the vided that not more than o'i grm. per 100 cc. is present. In working the process, the neutral or faintly acid solution containing nickel is heated and treated with a slight excess of dimethylglyoxime. Ammonia is then added gradually until a slight excess is present, the precipitate is collected | The carbon is evolved in the form of gaseous compounds, in a Gooch crucible, washed with hot water, and dried for three-quarters of an hour at 110°-120° C. If nickel and cobalt are both present, they are determined together by electrolysis, the deposit is dissolved in nitric acid, the solution evaporated with hydrochloric acid, and the nickel determined as described above. Another article appeared by the same author in the Zeitschrift für angewandte Chemie, 1907, xx., pp. 18441850, on the quantitative determination of nickel in the presence of cobalt, zinc, manganese, iron, aluminium, and chromium, by means of dimethylglyoxime. Nickel and Cobalt. The conversion of nitrate into chlorides before precipitation is unnecessary. If more cobalt than nickel is present, a larger excess of dimethylglyoxime is required, and where the quantity of nickel is small, a method is used in which sodium-acetate replaces ammonia. In this case o 5 grm. of the sample is dissolved in hydrochloric acid and the solution evaporated nearly to dryness. To the hot liquid after being diluted to 400 cc., are added o 2 grm. of dimethylglyoxime and 2 grms. of sodium acetate, and the precipitate is filtered off after half an hour. Nickel and Manganese.-Sodium acetate is used instead of ammonia to neutralise the mineral acid. Nickel and Zinc.-The separation succeeds in the presence of ammonia or acetic acid, but the latter is preferable. Nickel and Iron.-To the solution containing iron, in the ferric state. tartaric acid is added before precipitation, to prevent the subsequent formation of ferric hydroxide on adding ammonia. The method is applicable to nickel steels, since manganese does not interfere. Nickel and Aluminium.-The method is similar to the "nickel and iron " method. Nickel and Chromium.-Tartaric acid is added as above to prevent the precipitation of chromium by ammonia, but CO, CO2, &c. The loss is halved if the organic analysis of the carbonaceous residue is carried out without previous drying. Moreover, all loss is avoided if the cupric solution is boiled and the gases set free are passed over red-hot platinum in presence of excess of oxygen, and the carbon dioxide formed is received in baryta water. No. 16, April 19, 1909. Determination of Moisture in Altered Milks.— André Kling and Paul Roy.-The water in milk is generally determined by finding the percentage of dry residue after the fat has been extracted. This method is satisfactory for fresh milk, but when it is kept it undergoes changes owing to which the amount of dry residue varies progressively and shows a decided decrease. The total nitrogen, corresponding to the albumenoids of the milk, however, remains absolutely unaltered, and from the | determination of this constituent it can be ascertained with certainty whether water has been added to the milk or not. MEETINGS FOR THE WEEK. MONDAY, 7th.-Royal Institution, 5. General Monthly Meeting. TUESDAY, June 8th.-Royal Institution, 3. "Biological Chemistry," by F. Gowland Hopkins, F.R.S., &c. "Estimation of WEDNESDAY, 9th.-Society of Public Analysts, 8. Iron by Permanganate in presence of Hydro chloric Acid," by G. C. Jones and J. H. Jeffery. 'Jaffé's Colorimetric Method for the Estimation of Creatinine," by A. C. Chapman. "Estimation of the Alkalinity of Bleaching Powder Solutions," by K. J. P. Orton and W. J. Jones. "Sabatier-Senderens Test for distinguishing between Primary, Secondary, and Tertiary Alcohols" and "New Test for the Halogens," by G. B. Neave. it is necessary to have a sufficiency of ammonium chloride THURSDAY, 10th. - Royal Institution, 3. "A Modern Railway Problem present also. Nickel in nickel chrome steel may be thus directly determined. The methods are very accurate and rapid; a determination requires one hour, and the somewhat costly reagent may be readily recovered from the precipitates. - Steam v. Electricity," by Prof. W. Ě. Dalby. FRIDAY, 11th.-Royal Institution, 9. "Problems of Helium and Radium," by Prof. Sir James Dewar, F.R.S., &c. Physical, 8. "The Arthur Wright Electrical Device for Evaluating Formula and Solving Equations," by A. Russell and A. W right. "The Echelon Spectroscope, its Secondary Action and the Structure of the Green Hg Line," by H. Stansfield. "Proposed International Unit of Candle Power," by C. C. Paterson. "Inductance and Resistance in Telephone and other Circuits," by J. W. Nicholson. "Terrestrial Magnetism," by G. W. Walker. "Form of the Pulses constituting White Light," by A. Eagle. Plants," by F. F. Blackman, F.R.S., &c. H. Vdoviszevski publishes an article on "The Determination of Nickel in Nickel Steel and Nickel Chrome Steel by means of Dimethylglyoxime" in Stahl und Eisen, 1908, xxviii., p. 960, which is a modification of Brunck's method. The igniting of the precipitate is done in an ordinary platinum or porcelain crucible instead of using Gooch's crucible. The sublimation of the nickel SATURDAY, 12th. - Royal Institution, 3. "The Vitality of Seeds and oxime precipitate is prevented by careful manipulation. For the separation of nickel from iron Rothe's iron extraction method by means of an ether-acetone mixture is used. After the solution is freed froin iron, the nickel is precipitated with the respective amount of a 1 per cent alcoholic dimethylglyoxime solution. In the preser.ce of chromium 0.5 to 1 grm. of tartaric acid and an excess of ammonia is added to the solution before precipitation. The method requires about three hours and is very accurate. -The Chemical Engineer, ix., No. 4. CHEMICAL NOTICES FROM FOREIGN NOTE-All degrees of temperature are Centigrade unless the wa Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences. Vol. cxlviii., No. 15, April 13, 1909. Study of Gases Disengaged by the Action of Cupric Salts on Steels.-E. Goutal.-When steel is attacked by slightly acid copper chloride or potassium chloride at a moderate temperature in a current of nitrogen a loss of carbon amounting to o'or to o'05 per cent occurs. NOW READY. Cloth, 3/6; Paper covers, 2/6. (Postage, 4d. extra). THE WHEAT PROBLEM: Based on Remarks made in the Presidential Address to the British Association at Bristol in 1898. REVISED WITH AN ANSWER TO VARIOUS CRITICS By SIR WILLIAM CROOKES, F.R.S. SECOND EDITION. With Two Chapters on the Future Wheat Supply of the CHEMICAL NEWS OFFICE. 16 NEWCASTLE ST., FARRINGDON ST., E.C. Advertisements. JENA LABORATORY CLASSWARE. COMPOUND TUBING (D.R.P.) 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