THE ANALYST. 293 INORGANIC ANALYSIS. Determination of Minute Quantities of Bismuth in Copper and Copper Ores. T. C. Cloud. (Journ. SOC. Chenz. I z d . , xxiii., 524.) - The method is based upon the fact, recorded by Abel and Field (Jourrz. Cfzem. SOC., 1862), that when lead iodide is precipitated in the presence of even minute traces of bismuth the colour of the precipitate is changed to a more or less dark orange or red tint, the intensity of the colour change increasing with the quantity of bismuth present. For qualitative purposes the lead iodide first precipitated by the addition of just a sufficient amount of potassium iodide is redissolved in the requisite quantity of boiling dilute hydrochloric acid, the liquid allowed to cool, and the colour of the resulting crystals examined.The presence of 0.001 milligramme of bismuth may thus be detected. Owing to the fact that the crystalline precipitates vary in lustre and also in the size of the crystals, according to the rate of cooling, the author finds it neces- sary, for quantitative purposes, to examine the colour of the original precipitate of lead and bismuth iodides in comparison with a standard. The method is said to be capable of accurately determining 0.01 milligramme of bismuth. The following solutions are required : 1. Bismuth Nitrate.-Dissolve pure bismuth oxide in nitric acid, and dilute so that 1 C.C. contains 0.0001 gramrne bismuth. Sufficient nitric acid must be present to prevent precipitation of basic bismuth salt on dilution.294 THE ANALYST. 2. Lead ATitmte.-Dissolve 6 grammes of pure lead in nitric acid, evaporate until the excess of nitric acid is removed and the lead nitrate begins to crystallize out, then dissolve in water, making the solution up to 1 litre.3. Potassium Iodide.-Dissolve 35 grammes of the salt in water, and dilute to 4 litres. A suitable quantity of the metallic copper under examination is dissolved in nitric acid, and a solution of sodium carbonate carefully added to the cold liquid, until a small permanent precipitate is produced. The liquid is allowed to stand for some hours with frequent stirring. On filtration, the unwashed precipitate i s dissolved in dilute hydrochloric acid, and hydrogen sulphide passed through the solution. In the case of copper ores, the sample is dissolved in a mixture of nitric and sulphuric acids, and the liquid evaporated until the sulphuric acid fumes. The cold residue is treated with water and a very little hydrochloric acid, and hydrogen sulphide passed through the filtered solution.(This treatment with sulphuric acid is also followed in the case of " copper " containing appreciable quantities of lead.) The washed sulphide precipitate is dissolved in nitric acid, and,the solution made u p to 250 c c. Half of this solution is well shaken with 5 C.C. of the lead nitrate reagent, neutralized with ammonia, and a slight excess of ammonium carbonate solution added with shaking, followed by sufficient ammonia to keep the copper in solution. The liquid is filtered after being digested on the water-bath, and the small precipitate is washed with ammonium carbonate until all the copper is removed.The solution obtained by dissolving this precipitate in dilute nitric acid is evaporated until it crystallizes, when the residue is dissolved in hot water and a little nitric acid and made up to 25 C.C. in a Nessler tube. Twenty-five C.C. of the potassium iodide reagent are next added, and the precipitate produced compared with a standard made by adding a known quantity of bismuth solution to a mixture of 1 C.C. of dilute nitric acid, 5 C.C. of lead reagent, and 25 C.C. of potassium iodide. solution, the mixture being diluted with water to 50 C.C. as before. The contents of both Nessler tubes should be well stirred, and the tints of the precipitates finally compared after standing about fifteen to twenty minutes.A. R. T. The Bismuthate Method for the Determination of Manganese. Andrew A. Blair. (Journ. Anzer. Chcm. Soc., xxvi., 793.)-The author strongly recommends this method as being accurate and convenient. He emphasizes the necessity of removing every trace of hydrochloric acid before adding bismuthate. Whenever possible he prefers to dissolve in mixtures of acids free from hydrochloric acid. Chromium steels can be analysed by this method, as chromium is not oxidized in the cold; tungsten is best filtered off. To filter the solution after the addition ofl bismuthate, the author uses the pump, the funnel being placed in the neck of anl exhausted bell-jar, beneath which is placed a conical flask to receive the filtrate.. The same filter will serve for fifty or more determinations. A.G. L.THE ANALYST. 295 The Action of Sodium Picrate on Solutions of Sodium Carbonate. C. Reichard. (Zeit. anal. Clzem., 1904, xliii., 269-275.)-Details of experiments are given, from which the following conclusions have been drawn : (1) The only sodium salt capable of precipitating sodium picrate is the normal sodium carbonate. (2) The precipitation takes place whether the solution of sodium carbonate be added to the solutions of sodium picrate or vice versd. (3) Dilute solutions of sodium picrate (1 per cent.) are rendered turbid, while strong solutions (10 per cent.) solidify to a gelatinous mass. (4) The precipitation, which is gradual, takes place in solutions containing other sodium salts, including the bicarbonate and hydroxide.(5) The reaction may be employed as a teat for sodium carbonate, and conversely as a means of identifying sodium picrate. C. A. M. The Action of Sodium mtroprusside on Carbonates, Bicarbonates, Caustic Alkalies, and Ammonia. (Zeit. anal. Chem., 1904, xliii., 275-279.)- A solution of sodium or potassium hydroxide treated with a drop of a 20 per cent. solution of sodium nitroprusside becomes yellow after a few moments, the colour gradually increasing in intensity on standing. A dilute solution of ammonia, on the other hand, gives no coloration at all, or at most an extremely faint one, whilst strong solutions of sodium carbonate or bicarbonate also remain colourless. If a strong solution of sodium carbonate be treated with a few drops of sodium hydroxide solution, and then with one drop of a, 20 per cent.solution of sodium nitroprusside, no colour appears. And if to a dilute solution of sodium hydroxide, in which the yellow colour has been produced, there is added some powdered sodium carbonate, and the tube shaken, the colour gradually disappears, though it may be restored again by the addition of a relative excess of strong sodium hydroxide. Sodium nitro- prusside thus behaves in an analogous manner to litmus or phenolphthalein with regard to sodium hydroxide, though not in its behaviour towards carbonates and bicarbonates. Thus, if a strong solution of sodium carbonate containing a few drops of concentrated sodium hydroxide solution and one drop of sodium nitroprusside solution (colourless liquid) be exactly neutralized with hydrochloric acid, there is still no coloration.In the case of ammonia, experiments are described to show that when the amount of ammonia falls within certain limits (about 1.5 to 2 per cent.), it is possible to detect as little as 0-02 gramme of sodium hydroxide simultaneously present. C. A. M. C. Reichard. The Analysis of Sodium Nitrite. G. Lunge. (Chem. Zeit., 1904, xlii., 501.) -In this very detailed paper the author compares the various methods for the analysis of sodium nitrite, and gives the following results for the permanganate and sulphanilic acid methods. For the permanganate process a solution of nitrite containing 23 gr. per litre was run from a burette into semi-normal permanganate solution, and five experiments gave the following figures : I., 96.79; II., 97.02; III., 96.87; IV., 96.82; V., 96.96 per cent.NaNO,. Mean : 96.89 per cent. NaNO,.296 THE ANALYST. In the sulphanilic acid method sodium sulphanilate was used which had been dried-A, for two hours between blotting-paper ; B, subsequently kept for eighteen hours over concentrated H,SO,; C, left for further two days over H,SO,. A gave : 96-25 per cent. NaNO, (at ordinary temperatures). 96.39 ,) 9 , 7 , 96.30 ,, , f ,, 96.32 ,, 11 J , 96.44 ,, ,, , I 96.41 ), ,, (ice cold). 96.53 ,, 9 , 9 1 96.29 ,, ,, (at ordinary temperatures). 96.44 l l 9 , 1, 96.34 ,, ? t 1 , -- Mean 96.37 per cent. NaNO,. B gave : 96.71, 96-94, 96.85, 96.65 per cent. C gave : 96.47, 96.67, 96.77 per cent. The use of sodium sulphanilate dried over H2S0, gives, therefore, results only 0.1 to 0.2 per cent.below the permanganate method. When immediate blueing of the starch iodide paper is taken as the end point of the reaction, the latter method gives results comparable with those of the perman- ganate titration ; but as the preparation or purifying of the sodium sulphanilate is attended with considerable loss and trouble, while the permanganate method is very simple in application, he recommends that this be taken as the standard process. It is only unreliable when formic acid salts are present, which very rarely occurs. Mean : 96.74 per cent. NaN02. Mean : 96.67 per cent. NaNO,. H. A. T. The Determination of Nitrogen. L. Ddbourdeaux. (Bull. Soc. C ? L ~ ? L . , 1904, =xi., 578-580.)-The author has established that in the methods of Will and of Kjeldahl the ammonia is often accompanied by various amines.Thus, in the case of pyridine the conversion into ammonia is only partial, whilst caffeine yields a mixture of ammonia and monomethylamine. He has also found that the method in which sodium hypobromite is employed does not liberate the whole of the nitrogen in the amines, even in the case of urines. The method recommended is not capable of general application, but is stated to yield the whole of nitrogen in the form of ammonia without amines in the case of the following compounds : (1) Oxygenated compounds ; (2) hydroxylamine ; (3) nitro derivatives, in which the nitro group has a phenolic function; (4) nitrites, cyanides, and double cyanides ; (5) cyanates and thiocyanates ; (6) certain amides and imides ; (7) amines, in which the radicle has an acid function.This method, which is based on the action of alkali monosulphides on nitrogenous bodies in the presence of certain salts-notably, alkali thiosulphates-consists of two successive distillations in an iron flask connected with a modified Schloesing's apparatus constructed entirely of glass. The substance is first distilled to dryness with 50 grammes of crystalline potassium thiosulphate and 200 C.C. of a solution of potassium monosulphide, prepared by saturating a solution of potassium hydroxideTHE ANALYST. 297 solution of 36' B6. (specific gravity 1.33) with hydrogen sulphide, and adding an equal volume of the same hydroxide solution. In the second distillation, to remove the last traces 0: ammonia, 25 C.C.of potassium hydroxide solution and 250 C.C. of water are added to the residue in the flask, and about 150 C.C. of distillate collected. The ammonia is received in an excess of pure hydrochloric acid, and then determined. C. A. M. The Estimation of Argon in Atmospheric Air. H. Moissan. (Bull. Soc. Chim., 1904, xxxi., 729-735.)-The method was based on the absorption of the oxygen and nitrogen in a known quantity of air and measurement of the residual argon. The apparatus consisted of a graduated measuring vessel, holding about a litre of air, and connected by means of a pump with two tubes kept at a red heat, the first of which contained a mixture of quicklime and magnesium, and the second about 1 gramme of calcium in very small crystals. The air, after being dried over metaphosphoric acid, was introduced into the measuring vessel, where it was left all iiight at a constant temperature, and was then made to circulate through the absorption-tubes for three hours, until the height of the barometer connected with the pump became constant, showing that there was no more absorption of gas.A graduated tube was then attached to the pump, and the residual gas (argon) drawn into it and measured over mercury. Preliminary experiments proved that the first absorption-tube retained the whole of the oxygen and most of the nitrogen, and that the second retained the remainder of the nitrogen, also the hydrogen resulting from the decomposition of traces of moisture in the first tube, and also all gaseous im- purities in the air.The following results were thus obtained with samples of air of different origin : Atlantic Ocean, 0-9492 ; Paris, 0-9337 ; summit of Mont Blanc, 0.9352 ; London, 0.9325 ; Berlin, 0.9323 per cent., etc. In general, air from the interior of continents at heights from 0 to 4,800 metres contained from 0,932 to 0.935 per cent., whilst samples of air from over the sea were usually somewhat higher. C. A. M. Comparison of Methods for the Estimation of Soil Acidity. F. P. Veitch. (Journ. Anzer. Chem. SOC., xxvi., 637.)-The author proceeds as follows to determine the reaction of a soil : About 10 grammes of the soil are allowed to stand overnight with 100 C.C. of distilled water in a Jena glass flask. Fifty C.C. of the supernatant liquid are drawn off and boiled in a covered Jena beaker, after adding a few drops of phenolphthalein, until a pink colour is developed or until the volume has been reduced to 5 C.C.without the appearance of a colour. The pink colour shows the soil to be alkaline, while no colour shows it to be acid or neutral. The degree of acidity is determined by means of lime-water as follows : To three portions of soil, each consisting of as many grammes as the standard lime- water contains milligrammes of CaO per c.c., are added 50 to 60 C.C. of distilled water, and different amounts-e.g., 10 c.c., 20 c.c., and 30 c.c.-of lime-water. All three portions are at once evaporated to dryness on a steam-bath, the residues298 THE ANALYST. transferred to stoppered Jena flasks with 100 c,c.of distilled water, and allowed to stand overnight. Fifty C.C. are then drawn off from each portion and boiled, after adding a few drops of phenolphthalein, until a pink colour is produced, or until the volume is 5 C.C. The test is then repeated on three more portions of the soil, the amounts of lime-water added in this case differing from each other only by 1 or 2 C.C. The quantity of lime-water necessary to produce an alkaline reaction is taken as a measure of the acidity of the soil. The results will serve as a guide to the acidity of the soil. A. G. L. Standard Substances for Alkalimetry and Iodometry. F. Ra schig. (Zeit f. angezu. Chem., 1904, xviii., 577-584.)-1n the preparation of the standard hydro- chloric acid solutions, hydrogen chloride is passed into a flask containing water ; this is weighed before and afterwards, and then made up to a known volume.Standard solutions of sulphur dioxide may be prepared in a similar manner. The strength, however, should not be allowed to exceed &, as there is a great tendency for the gas to escape. Iodine solution is standardized against the sulphurous acid solution, and the same quantity of acid solution may lhen be used to ascertain the titre of an alkali solution. After the colour of the iodine has been exactly discharged methyl orange is added and alkali solution run in to neutralize the acid formed, in accordance with the equation- The results of the iodometric titration are liable to be rendered inaccurate by oxidation of the sulphurous to sulphuric acid. The solution of sulphur dioxide must therefore be freshly prepared, and be delivered into the iodine solution froin a pipette dipping below the surface of the liquid. In a subsequent issue of the Zeitschrif't fiir angezunndte Chenzie (1904, xxii., 716) W. A. Roth claims priority of the method for preparing standard solutions for hydro- chloric acid, on the ground that he recommended it at the Fifth Congress of Applied Chemistry in 1903. I t was, however, fully described by Dr. G. L. Moody in 1898 SO, + 21 + 2H20 = H2S0, + ,HI. (Tmizs. Chem. SOC., lxxiii., 658). A. M. The Filtration and Incineration of Precipitates. M. Dittrich. (Berzchte, 1904, xxxvii., 1840; through Chem. Z e d . Rep., 1904, xiii., 156.)-For the latter filtration, washing, and ignition of gelatinous precipitates, the author recommends the addition, to the liquid to be filtered, of finely pulped filter-paper. Washing is much more thorough, and instead of forming a hard thick mass, the ash is pulverulent. This method is of especial advantage when the precipitate has to be dissolved and reprecipitated, and when iron and alumina are to be separated by fusion with caustic alkali. H. A. T.