摘要:

ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. (Zeit. fiir angew. Chem., 1903, xvi., 764-773.)-A synopsis is given of all the published methods for distinguishing between raw and heated milk. The author has also made a, number of experiments, in which various amides and phenols were substituted for p-phenylenediamine in Storch’s reaction. The most sensitive and intense reaction was given by a, 2 per cent. solution of dimethyl-p-phenylenediamine hydrochloride. This, when added to 10 C.C. of raw milk mixed with two drops of hydrogen peroxide, gave an immediate carmine-red coloration, changing to violet. Boiled milk, containing five parts of raw milk, readily gave the coloration, but no colour was obtained with boiled milk alone. Detection of Heated Milk.M. Siegfeld. W. P. S.314 THE ANALYST. Determination of Fat in Milk. J. van Haarst. (Zeit. f i h angew. Chem., 1903, xvi., 773-776.)-The author has compared various centrifugal methods for deter- mining the amount of fat in milk. The Babcock-Lister process always gave too low results. Gerber's method, when properly carried out, gave good results, but showed a tendency to be a trifle too high. The method of Thorner, consisting in heating the milk with 50 per cent. potassium hydroxide solution for two minutes on the water-bath, and then adding glacial acetic acid, gave reliable results. The Adams process was used as a comparison. w. P. s. Determination of Succinic Acid in Wine, with some Remarks on the Determination of Malic and Lactic Acids i n the Same. R.Kunz. (Zeit. fiir Untersuch. der Nahr. und Genz~ssrnittel, 1903, vi., 721-729.)-Though many methods have been brought forward for the estimation of succinic acid in wine, these all lack exactitude. To remedy this, the author proposes the following method based on a peculiar property of this acid, in contradistinction to the other acids of wine-namely, its behaviour towards potassium permanganate in acid solution. 150 C.C. of the wine are concentrated to a volume of about 100 c.c., cooled, 4 grammes of barium hydroxide and 3 C.C. of 10 per cent. barium chloride solution added, and, after making the volume up to 150 c.c., filtered. 100 C.C. of the filtrate are boiled for ten minutes under a reflux condenser, then cooled, treated with a current of carbon dioxide, and evaporated to a thick syrup.The latter is taken up with 20 C.C. of water, and 80 C.C. of 95 per cent. alcohol are added. After two hours the precipitate formed is collected on a filter, washed with alcohol, transferred to a basin, and heated with a little water and 15 C.C. of dilute sulphuric acid (1 : 4) on a water- bath. While the solution is still hot, a 5 per cent. solution of potassium perman- ganate is added in excess, the excess decomposed by adding ferrous sulphate, and the whole is evaporated to a bulk of 50 C.C. I t is then exhracted in a Schacherl's apparatus with ether free from alcohol for sixteen hours. The ether is distilled from the extract, the residue being then dissolved in a little hot water, cooled, filtered, and the filtrate evaporated to dryness. The final residue is dissolved in water and titrated with Tc sodium hydroxide, using phenolphthalein as indicator.To allow for traces of sulphuric and acetic acids still contained in the residue, the neutral solution may be precipitated with excess of Tc silver solution, filtered, and the excess of silver titrated in the filtrate by Volhard's method. silver solution corresponds to 0.0059 gramme of succinic acid. The author found from 0460 to 0.115 per cent. of the latter in various wines. A method is given for the determination of malic acid in wine, based upon the fact that at a temperature of 120' to 130" C. sodium hydroxide converts malic acid into fumaric acid. The barium salts obtained by precipitating 100 C.C. of the wine, as described above, are evaporated with sodium hydroxide, the residue is heated for three hours at a temperature of 130" C., then dissolved in dilute hydrochloric acid, and the solution diluted to 100 C.C.after rendering alkaline with calcium hydroxide. The mixture is filtered, and 100 C.C. of the filtrate are thoroughly extracted with 1 C.C. ofTHE ANALYST. 315 ether. Fumaric and succinic acids are thus obtained together in the ethereal solution, from which they may be separated and titrated. Attention is drawn to the fact that, on distilling wine, some of the lactic acid present passes over with the volatile acids. The presence of acetic acid appears to increase the volatility of lactic acid. The results of a number of experiments show that about 3 per cent. of the total lactic acid is found in the distillate. W.P. S. Determination of the Diastatic Power of Enzymic Preparations. A. Pollak, (Zeit. fiir Untersuch. der Nahr. und Genussmittel, 1903, vi., 729-733.)-A preliminary experiment is made by heating 50 C.C. of 3 per cent. starch paste, prepared from arrowroot starch, on a water-bath at 37.6" C. with 10 C.C. of a 2 per cent. solution of the extract under examination. The time in minutes is noted when saccharification has proceeded so far that a drop of the solution tested with iodine gives a pure brown coloration. 250 C.C. of the starch paste are then heated to 39" C., and as many cubic centimetres of the extract solution added as the number of minutes which elapsed during the saccharification in the preceding experiment; the whole is then kept a t a temperature of 37.6" C.for exactly thirty minutes. The action of the enzyme is now arrested by adding about 3 C.C. of 10 per cent. potassium hydroxide solution, and the volume, after cooling, made up to 300 C.C. with water ; the amount of sugar formed in the solution is then determined by Fehling's volumetric method. w. P. s. Determination of Xanthine Bases in Meat, Yeast, and other Extracts. I. In Meat Extracts. I(. Micko. (Zeit. fiir Untersuch. dey Nahl-. und Genussmittel, 1903, vi., 781-791.)-The author has previously (ANALYST, 1902, 153) described a method for determining the total xanthine bases in meat extracts, and now gives the results of work undertaken for the purpose of isolating or separating the various bases, and to ascertain whether the same bases occur in various extracts.The present paper relates to the experiments made with meat (Liebig's) extract. The total bases were separated by the rnethod previously given. After evaporating the solution obtained on decomposing the silver precipitate, the residue was dissolved in a little water and decolorized by the addition of lead acetate and ammonia. On filtering and removing the lead as sulphide, the solution was evaporated, the residue taken up in its own weight of water at a temperature of 40" to 50" C., and allowed to stand for some hours. The evaporated filtrate gave a further amount of insoluble substance (fraction B) on treating the residue as above, and the filtrate from B yielded a residue on evapora- tion (fraction C). Fraction A.-A boiling solution of 3 grammes of the substance in 1,200 C.C.of water was treated with lead acetate, and ammonia added until the liquid above the lead precipitate was colourless. The precipitate was filtered off, washed, and the soluble lead removed from the filtrate, which was then evaporated to a small volume and allowed to crystallize. An analysis of the crystals, as well as the reactions given by them, showed that they consisted of hypoxanthzne. A base obtained from the lead A precipitate formed, which was collected in a filter (fraction A). These fractions were further examined, as described below :316 THE ANALYST. precipitate also consisted of xanthine. This fraction consisted principally of hypo- xanthine, with only a small quantity of xanthine.Fraction B.-On purifying the substance by treatment with lead acetate and ammonia, the resulting product was found to be almost entirely hypoxunthim. Fraction C.-Ten grammes were dissolved in boiling water, and treated with excess of 1.1 per cent. picric acid solution. After cooling and allowing to stand some time, a precipitate was separated (fraction D). The filtrate was extracted with toluene to remove the excess of picric acid, and the bases precipitated as silver salts, the free bases being then obtained by decomposing the silver salts with hydrogen sulphide. On evaporating the solution, a small quantity of hypoxanthine separated out. The filtrate from this yielded a small residue consisting of adenine mixed with hypoxanthine. Fraction D.-The precipitate, after being washed with the least possible quantity of water, was dissolved in hot dilute hydrochloric acid, and the picric acid extracted with toluene.The solution was rendered ammoniacal and precipitated with silver solution, the free bases being then obtained from the silver precipitate. The bases were purified by the lead acetate process, the filtrate from the lead sulphide being evaporated after making alkaline with ammonia. The crystals obtained consisted of udenine. The author concludes from the above results that the greater part of the xanthine bases occurring in meat extracts consists of hypoxanthine. Xanthine only occurs in small amount, and adenine is also present. Guanine and carnine were not detected. w. P. s. A New Test for Phenacetin. G. M.Beringer. (Chemist and Druggist, 1903, xliii., 377.)-One-tenth gramme of phenacetin is boiled for one minute with 3 C.C. of 50 per cent. sodium hydroxide solution. The mixture is then cooled and shaken with 5 C.C. of sodium hypochlorite solution. If the phenacetin be pure a clear yellow liquid will result, whilst a purple-red or brownish-red, turbid solution or precipitate indicates the presence of scetanilide. w. P. s. Separation of Strychnine and Quinine. E. IF. Harrison and D. Gair. (Pharm. Jour., 1903, xvii., 165.)-The following method, depending on the different solubilities of the tartrates of strychnine and quinine in a solution of Rochelle salt, was found to give accurate results. A quantity of the mixed alkaloids containing about 0.05 to 0.1 gramme of strychnine is dissolved in 60 C.C.of water slightly acidulated with sulphuric acid and ammonia added as long as the precipitate redissolves. Pifteen grammes of powdered sodium potassium tartrate are then gradually stirred in, and ammonia added uutil the mixture is slightly acid to litmus-paper, and the whole heated on a water-bath for fifteen minutes and allowed to cool. The quinine tartrate is filtered off, and washed with a, solution of 15 grammes of sodium potassium tartrate in 45 C.C. of water made just acid with sulphuric acid. The filtrate and washings are mixed, rendered strongly alkaline with ammonia, and extracted three or four times with chloroform. After washing the chloroformTHE ANALYST. 317 solution with a little water, it is evaporated to about 5 c.c., when 10 C.C.of alcohol are added, and the mixture evaporated to dryness. The residual alkaloid is washed three times with 1 C.C. of washed ether, the washings being rejected, and the residue of practically pure strychnine dried and weighed. The presence of considerable quantities of other alkaloids does not seriously affect the accuracy of the method. w. P. s. Iodometric Valuation of Chloral Hydrate. E. Rupp. (Arch. Phurm., 1903, ccxli., 326 ; through Chem. Zeit. Rep., 1903, 205.)-Caustic alkali and iodine Eolution convert chloral hydrate into chloroform and carbon dioxide. Twenty-five C.C. of decinormal iodine solution are mixed with 2.5 C.C. of normal potassium hydroxide in a stoppered flask, and 10 C.C. of a 1 : 100 solution of chloral hydrate are added.After standing five or ten minutes, the liquid is diluted with 50 C.C. of water, 5 C.C. of hydrochloric acid are introduced, and the whole is titrated with decinormal thiosulphate. Between 12.9 and 13.5 C.C. (100 to 95 per cent. chloral hydrate) of the reagent should be required. F. H. L. Determination of Oil in Colocynth Pulp. E. Doweard. (Pharm. Journ., 1903, lxxi., 400.)-According to the British Pharmacopoeia, colocynth pulp should only yield a trace of fixed oil to ether. This is to insure the absence of seeds, which constitute about two-thirds the weight of the imported fruit, and contain a large amount of oil. Pure colocynth pulp yields about 3 per cent. of soluble matter when extracted with ether, and this can scarcely be called a trace. The greater part of the extract, however, consists of colocynthin, and not oil.As colocynthin is insoluble in petroleum spirit, the oil may be accurately determined by using this solvent. A number of samples, when extracted with petroleum spirit, gave under 1.5 per cent. of oil. The author suggests that 2 per cent. might be fixed as the maximum amount permissible. w. P. s. TOXICOLOGICAL ANALYSIS. The Guaiacum Test for Blood. D. Vitali. (Boll. chim. farm., 1903, xhi., 177; through Ckem. Xeit. Rep., 1903, 217.)-Tarugi has stated that potassium thio- cyanate is capable of giving a blue colour with guaiacum tincture in presence of old oil of turpentine; and he ascribes this fact to the oxidation of the sulphur in the thiocyanogen by the turpentine, which yields some of Caro’s acid, this in turn reacting with the guaiacum. Vitali remarks that potassium and ammonium thio- cyanate do give the Van Deen test, though much less strongly than hzemoglobin, the main reason being that the commercial potassium salt commonly contains a small quantity of a ferrous compound which acts (like haemoglobin) as EL carrier of the oxygen of the oxidized turpentine to the resin. With pure thiocyanates, free from iron, the blue is muoh weaker, but it still occurs. Vitali finds that if a mixture of potassium thiocyanate and barium chloride is shaken with old oil of turpentine,318 THE ANALYST. allowed to stand, filtered and boiled, the filtrate becomes turbid, which renders probable a formation of Caro’s acid, persulphuric acid, or some similar unstable oxidizing body. Nevertheless, this fact does not diminish the value of the Van Deen test. Thiocyanic acid does actually exist in some animal liquids, such as urine and saliva, but in such small quantities that no confusion can arise between them and blood when examined in the dry state, F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9032800313

出版商:RSC    

年代:1903

数据来源: RSC

摘要:

318 THE ANALYST. ORGANIC ANALYSIS. Determination of Cellulose and Lignin in Foods and Fodders. J. Konig, (Zeit. fiir Undersuch. der Nahr. und Genussmittel, 1903, vi., 769-781.)-Three grammes of the air-dried substance are thoroughly mixed in a flask or basin with 200 C.C. of glycerol of specific gravity 1-23, containing 2 per cent. of sulphuric acid, and then either boiled under a, refiux condenser, the boiling-point being 1 3 3 O to 135' C., or heated in an autoclave to 137" C. (three atmospheres). After one hour the mixture is cooled, diluted to 500 c.c., boiled once more, and filtered through an asbestos filter. The residue is washed with 400 C.C. of boiling water, then with hot alcohol, and finally with a mixture of alcohol and ether, until the filtrate is colourless. The asbestos filter and residue are dried at 110" C.and weighed. After igniting and sub- tracting the weight of asbestos and ash, the difference gives the amount of ash-free '' crude fibre." Another 3 grammes of the substance are digested with glycerol and sulphuric acid, as described above, the residue obtained, together with the asbestos filter, being transferred to a, beaker, and treated with 150 C.C. of pure 3 per cent. hydrogen per- oxide and 10 C.C. of 24 per cent. ammonia, solution. After standing twelve hours 10 C.C. of 30 per cent. hydrogen peroxide are added, this addition being repeated about five times, or until the " crude fibre" is colourless. At the third and fifth additions 5 C.C. of ammonia are also added. When the substance is completely bleached, the whole is warmed for from one to two hours on a water-bath, and then brought on to a second asbestos filter, washed as before, dried and weighed.On deducting the cellulose thus obtained from the L 6 crude fibre '' the amount of lignin is obtained. To obtain trustworthy results the above conditions $8 to procedure and concen- tration of the solutions must be adhered to. w. P. s. Errors caused by Precipitations in the Polarimetry of Sugar. (1) Wiech- mann (Zeits. Zuckerind., 1903, liii., 498) ; (2) Gonnermann (CentraZbZ. Zuckerind., 1903, xi., 1200; both through Chem. Xeit. Rep., 1903, 225).-A series of experi- ments, in which the Scheibler and Sachs process was employed, carried out by Wiechmann upon colonial sugars coming from different places, show that the normal weight of sugar gives a precipitate which, in the dry state, may vary in weight from 0.1 to 1.5 grammes, in specific gravity from 1.65 to 4-38, and in volume from 0.05 to 0.71 C.C.These variations have no relationship to the quality or opticity of the sugar, and may cause errors of from 0.05" to 0.98" Ventzke. The errors are generally ignored, because it is assumed that the lowering effect upon the results of working at a temperature above the normal com-THE ANALYST. 319 pensates for them. If the working temperature is between 24" and 25' C., instead of 20" C., a mean positive error of 0.38" remains, which on the large scale represents 0.25 per cent. I t is highly desirable, therefore, that ~ o m e Gonnermann expresses the opinion that a lead precipitate, which is produced in a liquid from constituents already therein, and which does not cause any alteration in the volume of that liquid, introduces no error by its formation.This, however, is not the case. ethod of removing this source of error should be discovered. F. H. L. Temperature Coeacient of the Specific Rotatory Power of Sugar. Schon- rock. (Zeits. Zuckerind., 1903, liii., 650 ; through Chem. Zeit. Rep., 1903, 225.)-The author has examined the effect of temperature upon the specific rotatory power Gf sugar and also the effect of the wave-lengths ,UP 589.3 (yellow Na line), 546.1 (yellow- green Hg line), and 435.9 (blue Hg line). For practical purposes the exact wave-length is of no importance, and@@ 589.3 may be employed. For temperatures ( t ) between 9" and 31" C.the rotatory power of a normal sugar solution varies in direct proportion to t ; and if a glass tube is used which has the coefficient of expansion P=O*OOOOO8, the correcting equation becomes : If the normal solution be prepared at 20" C. and is polarized at a diflerent tempera- ture (t), the value 0.061 ( t - 20) must be added to the Ventzke reading in order to cbtain the proper figure for 20" C. a 2 0 D - ~ 4 , + aA0.000461 ( t - 20). F. H. L. An Impravement in Seliwanoff's Test for Sugars. U. Rosin. (xeits. physiol. Chem., 1903, xxxviii., 555 ; through Chem. Zeit. Rep., 1903, 217.)-This test may be made considerably sharper by working in the following manner : The liquid is boiled with an equal volume of hydrochloric acid and a few grains of resorcinol; if the characteristic red colour appears, it is cooled, and sodium carbonate is added till effervescence ceases.This produces a pale orange turbid liquid, which when extracted with amyl alcohol yields to the solvent a red dyestuff having a yellow tint and a slight green fluorescence, which becomes pure rose-red on the introduction of a few drops of absolute ethyl alcohol. If the amyl alcoholic solution is diluted considerably and examined spectroscopically, it shows a single band in the green between the lines E and b ; rather stronger solutions give a very dark band, sharply defined, and overlapping the lines, also a faint ill-defined band in the blue about the line F. Con- centrated solutions absorb the green. Addition of ethyl alcohol also increases the depth of the green band.If the solution in amyl alcohol is repeatedly extracted with water, the alcoholic liquid becomes orange, and its absorption bands disappear ; and if, after all alkali has been removed, ethyl alcohol is introduced into the liquid, the bands still remain absent. F. H. L.320 THE ANALYST. Analysis of Glycogen. E. Pfluger. (Pjliiger's Archiv., 1902, xc., 523, 524; through Zeit. fiir Untersuch. der Nahr. und Genussmittel, 1903, vi., 797,798.)-Glycogen prepared strictly according to the Briicke-Kiila method is rapidly decomposed by even dilute potassium hydroxide on heating. If, however, the glycogen be prepared from the organ without the use of Brucke's reagent, and especially if mineral acids be avoided, it may be heated for several hours with concentrated potassium hydroxide without decomposition taking place.When extracting flesh containing glycogen with 30 per cent. potassium hydroxide the amount of glycogen obtained is not influenced by the time of heating. The author is of opinion that the substance until now known as glycogen is actually a decomposition product of the latter, and terms it '' pseudo- glycogen. " w. P. s. Determination of Glycogen. E. Salkowski. (Zeit. Physiol. Chem., 1902, xxxvi., 257-260 ; through Zeit. fiir Untersuch. der Nahr. und Genussmittel, 1903, vi., 798, 799.) -The determination of glycogen by the Kiilz-Pfliiger-Nerking method is simplified and rendered more expeditious by previously treating the minced liver with absolute alcohol, and then with ether.The liver is thus obtained as a fine powder, which is easily dissolved by dilute potassium hydroxide and by artificial gastric juice. Treatment with diastase completely separates the glycogen without danger of converting it into grape-sugar, as in the ordinary process. The supposition that glycogen is present in liver in com- bination with albumin is open to doubt. w. I?. s. Kapok Oil. E. Durand and A. Baud. (Ann. de Chim. anal., 1903, viii., 328-330.)-The seeds of the kapok (Eriodendron anfractuosum) extracted by the authors with ether yielded 24.8 per cent. of a deep yellow oil with the following characteristics : Specific gravity at 100" C., 0.8613 ; oleo-refractorneter reading at 40" C., 51.3 ; solidification point, 29.6" C. ; iodine value. 68.5 ; saponification value, 205.0; and solidification point of fatty acids, 32' C.The most interesting colour reaction of the oil was that it gave an intense red coloration in Halphen's test for cotton-seed oil, and the authors lay stress on this fact from an analytical point. of view. (See this Vol., 40.) C. A. M. The Influence of Atmospheric Oxidation upon the Composition and Analytical Constants of Fatty Oils. (Journ. Amer. Chem. SOC., xxv., 711.)-From a study of the effect of simultaneous exposure t o air and sunlight during several months on samples of different oils-such as olive, lard, cotton-seed, maize, poppy-seed, seal, and linseed oil-the authors show that the oxidation which takes place results in a decrease in the Hub1 figure and heat of com- bustion, and an increase in specific gravity and specific temperature reaction with sulphuric acid.The decrease in the heat of combustion is due to the larger amount of oxygen contained in the exposed sample. In the case of linseed oil, only oxygen is taken up during the oxidation, no hydroxyl groups being introduced, and the ratio of carbon to hydrogen consequently remaining constant. For non-drying and semi- H. C. Sherman and 116. J. Falk.TRE ANALYST. 321 drying oils, which add hydroxyl during oxidation, the increase in specific gravity due to this introduction of hydroxyl groups is directly proportional to the decrease of iodine-absorbing power. Percentage increase in specific gravity : decrease in Hubl figure : : OH : I that is, as 17.008 : 126.85, or as 1 : 7.46. This formula agrees well with direct experiments, and by its help the original Hubl figure of an oxidized oil may be calculated if the original specific gravity is known.Failing this, the average specific gravity of the class of oils to which the sample belongs may be taken as the original specific gravity, and the original Hub1 figure caiculated from this. The relation may be expressed by the formula : A. G. L. New Method of Tannin Determination. P. Feldmann. (Pharm. Zeit., xlviii., 155 ; through Pharm. Joum., 1903, Ixxi., 297.)-The author modifies the Neubauer- Lowenthal method by substituting a standard solution of bleaching powder for the potassium permanganate. As the hypochlorite solution is without action on alcohol, glycerol, and other organic bodies, the method is particularly suitable for the deter- mination of tannin in wine, without previous distillation of the latter.Ten C.C. of wine are diluted with water to 190 c.c., 2 C.C. of 0.5 per cent. indigo solution and 2 C.C. of 20 per cent. sulphuric acid are added, and the mixture titrated with the standard hypochlorite solution. This is prepared by treating 12.5 grammes of bleaching powder with water and diluting to 1,000 C.C. Another 10 C.C. of the wine are mean- while heated on a water-bath after adding 30 C.C. of water and 0.3 gramme of animal charcoal. The mixture is filtered, the filter washed with warm water to make 200 C.C. of filtrate, and then titrated, the indigo and acid being added as before. The difference in the two titrations corresponds to the tannin.The hypochlorite solution is standardized against a solution of pure tannin. With other substances containing tannin the method is carried out in a similar manner, but the tannin is removed before the second titration by treating the solution with a few grammes of hide powder. The latter retains the whole of the tannin. W. P, S. Detection of Indican in Urine. E. Riegler. (Pharm. 2. H., 1903, xliv., 567 ; through Chem. Zeit. Rep., 1903, 226.)-This test depends on the fact that, when treated with hydrochloric acid and an oxidizing agent, indican is converted into indigotin. 0.05 gramme of barium peroxide, 2 or 3 C.C. of chloroform, 10 C.C. of urine, and 10 C.C. of strong sulphuric acid are mixed together in a test-tube and shaken for one or two minutes. When it settles out, the chloroform will be coloured dark blue if indican is present.F. H. L. Determination of Sulphur in Urine by means of Sodium Peroxide. G. Modrakowski. (Zeits. physiol. Chem., 1903, xxxviii., 562 ; through Chem. Zeit. Izep., 1903, 217.)-Fifty C.C. of urine are allowed to flow slowly from a pipette upon 1 or 2 grammes of sodium peroxide in a nickel basin of moderate size. A certainTHE ANALYST. Hydrocyanic acid ... Pyridine ... ... 0.146 ,, Nicotine ... ... 1.165 ,, 0.080 per cent. amount of foaming takes place, but no spirting of the mass. It is next evaporated on the water-bath to the consistency of a syrup, when 2 or 3 grammes more of peroxide are added gradually and stirred in. When the reaction loses its violenoe, the basin is heated over a small spirit-lamp until visible vapours of water no longer appear.The flame is then urged, 1 to 3 grammes of peroxide being again added if necessary, till the mixture yield8 brown drops and becomes finally viscid. The melt is cooled, dissolved in hot water, filtered, rendered faintly acid with hydrochloric acid, and the sulphuric acid is precipitated with barium in the ordinary way. It is necessary that the filtrate shall be absolutely clear, or the barium sulphate will be impure. F. H. L. Ammonia ... ... 0.360 per cent. Carbon monoxide ... 410 C.C. per 100 grammes of tobacco.THE ANALYEIT. 323 Use of Magnesia in the Incineration of Organic Substances. H. Klein. (Chem. Zeit., 1903, xxvii., 923.)-The author strongly recommends an addition of heavy calcined magnesia, to the extent of 60 to 75 per cent.of the weight of material dried at 100" C., to any organic substance which has to be ignited. The organic portion burns off quickly and completely over a small flame ; chlorides and bromides being entirely, and erseuic and antimony partially, retained in the ash. F. H. L. The Determination of Carbonic Acid in Drinking-Water. Fred B. Forbes and Gilbert H. Pratt. (Journ. Amer. Ghem. Soc., xxv., 742.)-From a number of comparative experiments as to the accuracy of the Pettenkofer, Seyler (ANALYST, vol. xxii., 312), and direct gravimetric methods for the determination of carbonic acid, the authors conclude that the Seyler method is, on the whole, the best, the direct method requiring too much apparatus for field use, whilst the Pettenkofer method, although results given by it generally agree well with the values furnished by the other methods, occasionally gives very erratic results. The cause of these irregularities is not clear, although they are generally attributed to the presence of magnesium salts. In their preference for the Seyler method as the most accurate and convenient, the authors agree with Ellms and Benker (ANALYST, 1901, 306). Instead of Trillich's modification of Pettenkofer's method for the determination of half-bound carbonic acid, the authors prefer a method devised by Drown, as being more con- venient. In this method the water is allowed to drop down a tube 24 feet long, Q inch in diameter, drawn out at one end and filled with gravel. This tube is fitted into a bottle, a strong current of air being drawn through the whole. The half-bound carbonic acid is then determined on the water in the bottle by Pettenkofer's method. A. G. L.

ISSN:0003-2654    

DOI:10.1039/AN9032800318

出版商:RSC    

年代:1903

数据来源: RSC

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THE ANALYST. 323 INORGANIC ANALYSIS. The Volumetric Determination of Mercury and of Hydrocyanic Acid. Launcelot W. Andrews. (Amer. Chem. Journ., xxx., 18'7.)-In principle the method depends on the precipitation of hydrocyanic acid with a neutral mercuric chloride solution, the liberated hydrogen chloride being titrated with alkali, using paranitro- phenol as indicator. To determine hydrocyanic acid or a simple cyanide, the solution is diluted until it contains not more than 1 per cent. of the cyanide ; after adding 2 drops of a saturated aqueous solution of paranitrophenol, either hydro- chloric acid or & potassium hydroxide solution is added, if necessary, until a, faint yellow colour is attained. An excess (15 or 20 c.c.) of a nearly saturated aqueous solution of mercuric chloride is then added, the whole allowed to stand for one hour, and the hydrogen chloride titrated.The titration of mercury is conducted in % similar manner, but in this case a standard solution of hydrocyanic acid is necessary, which may be prepared by dissolving 68 to 80 grammes of potassium cyanide in 500 C.C. of water, adding 5 grammes of barium chloride dissolved in a little water, and filtering from carbonate; 10 C.C. of nitrophenol solution are then added, and the liquid is neutralized, at first with dilute sulphuric acid, and finally with hydro-324 THE ANALYST. chloric acid. The solution, which should be colourless, is then made up to 1 litre, disregarding the barium sulphate, and standardized. The mercuric chloride to be determined is treated with a small excess of this solution, after which the procedure is the same as before.Mercuric nitrate may be converted into the chloride by of sodium chloride. Organic acids must be absent. The good results, especially for dilute solutions. A. G. L. adding a small excess method described gives Analysis of Soft quantity of lead-viz., and other analysts is Lead. 0. Herting. (Chem. Zeit., 1903, xxvii., 923.)-The 200 grammes-which has been recommended by Fresenius too small when the foreign metals present in the highest grades of pure metallic lead have to be determined accurately, 400 to 500 grammes at Ieast being necessary. Whether a lead contains much or little antimony, the solid matter deposited after dissolution never contains lead antimoniate, as stated by Krug and Hampe, but consists of silica combined with a little alumina and iron, tinted perhaps with carbon.If the lead contains much antimony, an antimony antimoniate may be formed, but this is soluble in hydrochloric and tartaric acids. Lead antimoniate assumes a yellow colour on ignition, and is not soluble in the two acids mentioned. After the bulk of the lead has been removed as sulphate from the primary solution, the metals of the copper group are separated with H,S, converted into nitrates, and treated with a large excess of sulphuric acid in order that the residual lead sulphate may not be contaminated with bismuth. Ammonia in excess (not the carbonate) is added next to throw down the bismuth, leaving copper, cadmium, and silver in solution. The bismuth hydroxide, which contains a little basic sulphate, is washed thoroughly with warm ammonia to remove any copper that may be carried down with i t ; it is then taken up in warm nitric acid, and precipitated as a pure basic carbonate with ammoniuni carbonate. The silver is separated from the cadmium and copper by means oi hydrochloric acid, and the latter are isolated by treatment with H,S and 1 : 5 sulphuric acid.The cadmium is finally thrown out of its sulphuric acid solution with potassium carbonate, the sodium salt giving a precipitate that does not wash well. The author remarks that bismuth is the really objectionable impurityin high-grade commercial lead, spoiling the colour of the red lead made from it, and being trouble- some in the manufacture of nitrites.If required for the preparation of red lead, a metal containing more than 0.02 per cent. of bismuth should be rejected. F. El. L. Volumetric Estimation of Antimony in Antimonial Lead. H. Nissenson and P. Siedler. (Chem. Zeit., 1903, xxvii., 749.)-After a critical review of the processes suggested for the above purpose, the authors describe their own, which is an adaptation of the method outlined by Gyory. About 1 gramme of the sample is powdered as finely as possible, covered with 20 C.C. of a saturated solution of bromine and warmed gently (too strong heating only wastes the ,THE ANALYST. 325 bromine) with constant agitation till everything is dissolved, or until only a white residue is left. This brings the bulk of the antimony into solution in the lower state of oxidation.In order to reduce the remainder, the liquid is boiled till the va,pours are only faintly yellowish, allowed to cool a little, and two or three crystals of sodium sulphite are added one at a time. The liquid is next boiled again for about five minutes till all the sulphur dioxide is driven off, 20 C.C. of dilute hydrochloric acid are introduced, the mixture is brought to the boil once more, and titrated while still hot with a decinormal solution of potassium bromate made by dissolving in 1 litre of water 2.7852 grammes of the recrystallized salt, dried first at 100" C., and then in the desiccator. Methyl orange may be used as indicator, but indigo (in sulphuric acid solution) is preferable. If the indigo is only added just before the end of the titration, the blue colour gradually changes to a bluish-green, the penultimate drop of bromate producing a greenish-yellow, and the final drop a faint yellow with a tint of red; but if the indicator is introduced at the commencement, the blue gradually disappears without these alterations.It is therefore desirable not to add the indigo till just before the end of the titration; but if the quantity of antimony is quite unknown, titration may be continued in presence of the indicator till decolori- zation occurs, when three drops more are put in. This will either be bleached at once, or will give the colour play already described. Iron, as it exists in antimonial lead, and copper up to 0-5 per cent., do not interfere with the method; whilst arsenic, even when present in considerable quantity, is entirely volatilized as arsenious bromide during the dissolution of the alloy in the bromine-hydrochloric acid.The examples quoted show the process to be accurate ; it only occupies thirty or forty- five minutes, and half a dozen analyses may be carried out simultaneously. The method may be used for estimating the antimony in complicated ores, pro- vided they are dissolved in strong sulphuric acid treated with sulphuretted hydrogen, the precipitate taken up in hot strong hydrochloric acid, and titrated, as bafore, with bromate. Filtration is not necessary, as sulphur and undissolved sulphides do not affect the process. F. H. L. The Electrolytic Estimation of Antimony and its Separation from Tin. A. Fischer. (Ber., xxxvi., 2348 ; through Zeits.f. angew. Che.m., 1903, xxxiv. 829).- I n the electrolytic deposition of antimony from its solution in sodium sulphide, if the electrolysis be continued too long the result will be low, because the polysulphides have a solvent action upon the metal. This danger can be avoided if potassium cyanide be added to the electrolyte during the electrolysis, the polysulphides being thus reduced to monosulphide, potassium sulphocysnide being formed at the same time. Sufficient of a 30 per cent. solution of potassium cyanide is added to the yellow solution to decolorize it, and the electrolysis is carried out at 60" to 70" C., with 0.45 to 0.8 amphe and 1.7 to 1.8 volts, potassium cyanide being added from time to time. Continuation of the electrolysis after all the metal has separated has no bad effect, provided that sufficient potassium cyanide be run in to keep the solution colourless.For this purpose 20 to 30 C.C. of the 30 per cent. aolution are326 THE ANALYST. necessary. The electrolysis requires five to six hours, whereas without the addition of potassium cyanide fourteen to sixteen hours are necessary. Antimony can readily be separated from zinc by electrolysis in concentrated solution of sodium sulphide by Classen's method, provided the antimony be present in the trivalent form. Sufficient sodium monosulphide must be employed to saturate the electrolyte at 50", and in addition some grammes of pure sodium hydroxide should be added. Using 0.5 to 0.9 ampere at 0.8 to 0.9 volt and 60" to 70" C., the separa- tion is complete in three hours, If the antimony be pentavalent, it is deposited free from tin, but the yield is not quantitative.I t can, however, be rendered quantitative by the addition of potassium cyanide, but the temperature must then not be raised above 30°, and the potential difference must not exceed 1-1 volts. Under these conditions the electrolysis is complete in seven hours. The end of the process may be recognised by the addition of more sodium sulphide solution which should produce no further black deposit on the bright platinum dish. The washing can be carried out after the current has been interrupted. I n order to reduce to a minimum the production of sodium polysulphides by hydrolysis, 10 to 15 C.C. of a 30 per cent. solution of potassium cyanide should be used, and 3 to 5 grammes of sodium hydroxide in concentrated solution.The sodium hydroxide must be free from impurities, and should therefore be prepared from the metal. A. M. The Volumetric Determination of Bismuth as Molgbdate and its Separation from Copper. Herman S. Riederer. (Journ. Amer. Chem. SOC., xxv., 907.)-The author has found that bismuth may be completely separated from copper by adding a considerable quantity of tartaric acid to the acid solution of both metals, making the solution alkaline with potassium hydrate, adding a small excess of potassium cyanide, and then passing hydrogen sulphide through the liquid, The method is especially convenient for the separation of small quantities of bismuth from large amounts of copper. The author also shows that bismuth may be rapidly and accurately determined volumetrically as follows : To the nitric acid solution a large excess of ammonium molybdate dissolved in nitric acid is added, and the solution is neutralized with ammonia till the liquid is only just acid; methyl orange may be used as indicator. The liquid is then heated, but not boiled, for a short time, when a heavy white precipitate is obtained, which has the composition NH,Bi(MoO,), ; a yellow colour of the precipitate indicates the presence of the normal molybdate Bi,( MOO,),, which may be removed by dissolving in nitric acid and again neutralizing with ammonia.The precipitate is washed with a 3 per cent. solution of ammonium sulphate, and ihen dissolved in sulphuric acid; the solution is run whilst hot through a Jones reductor, and the reduced molybdenum titrated with potassium permanganate, the results being calculated on the assumption that the reduction has proceeded as far as the oxide M o , , ~ , ~ .The permanganate may also be standardized against a pure bismuth solution as a check. A. G. L.THE ANALYST. 327 O n the Reduction of Molybdenum by Zinc and the Ratio of Bismuth to Molybdenum in Bismuth Ammonium Molybdate. Edmund H. Miller and Henry Frank. (Joum. Amer. Chem. SOC., xxv., 919.)-The authors confirm Riederer's work on bismuth ammonium molybdate (see preceding abstract), but prefer to use Congo red instead of methyl orange in the precipitation of this salt. They agree with Noyes that a sulphuric acid solution of molybdenum is reduced to a point corresponding closely with an oxide M O ~ ~ O , ~ when run through a zinc reductor, amalgamated zinc giving a slightly less reduction than unamalgamated. m7ith a 15-inch column of twenty to thirty-mesh zinc, the solution having a volume of 200 c.c., an acidity of 10 C.C.concentrated sulphuric acid, and requiring six minutes for its passage through the reductor at a temperature of 70" to 75" C., the factors found for converting the iron standard of the permanganate into the MOO, and phosphorus standards (when ammonium phospho-molybdate is reduced) are : For unamalgamated zinc, 0.88 and 0.01579 respectively ; for amalgamated zinc, 0.8842 and 0.01586 ; the factors based on the reduction to M o , , ~ , ~ being 0.8832 and 0-01584. In these experiments the sir was not displaced by carbon dioxide.Blair's method, on the other hand, in which the molybdate solution is reduced with zinc and sulphuric acid contained in a flask provided with an exit-tube dipping in sodium bicarbonate solution, gives a reduction to Mo203, but the results obtained are not so uniform as those given by a reductor. A. G. L. The Separation of Iron from Manganese by the Acetate Method. A. Mittasch. (Zeit. a d . Chem., xlii., 492-509.)-According to the results of the author's experiments to test the reliability of this method a considerable variation is permissible in the amount of acetic acid, provided that the amount of acetate is increased in approximately a corresponding proportion. Complete precipitation was attained with the greatest certainty when the amounts of acetic acid and neutral acetate were in approximately molecular proportion to one another.The amount of acetic acid required depends mainly on whether the neutral or acid acetate is employed. By adding a larger amount of the neutral salt errors due to the addition of too large an excess of acetic acid maybe obviated. I t is best to add the acid after neutralization of the liquid, and to add the acetate (preferably the ammonium salt) to the boiling solution. The following method embodying these conclusions is recommended : The acid solution of 100 c.c., containing about 0.3 gramme of iron with more or less manganese, is treated with ammonium carbonate, which is added from a burette until a faint permanent turbidity results. From 3 to 5 C.C.of double normal acetic acid are then added if commercial acid ammonium acetate is to be used, or 10 C.C. with the neutral acetate. After dilution to 400 c.c., the liquid is brought to the boiling-point and mixed with 20 C.C. of normal neutral acetate solution, or semi- normal acid acetate solution, and the beaker kept over the flame for a minute. The precipitate is collected, washed with water containing ammonium acetate and acetic acid, dried, and ignited. The use of a closed Hempel's oven for the ignition is shown to give too low results. C. A. M.328 THE ANALYST. The Colour Test in High Carbon Steeis. George Auchy. (Journ. Amer. Chem. SOC., xxv., 999.)-The author claims that the direct test, although usually considered unreliable, gives results generally accurate to within 0.03 per cent. of carbon if it is carried out ag follows : 1 gramme of the sample is dissolved in 20 C.C.acid in a 41 C.C. test-tube provided with a mark at 25 C.C. The liquid is diluted to the mark and well mixed, after which 5 C.C. are withdrawn for comparison. The acid used must be cooled to 0" C. before use, and must be added all at once, whilst the test-tube itself must be vigorously moved about for one minute after the addition of the acid in a beaker containing ice-water before placing it in the water-bath con- taining cold water. In this way the loss of hydrocarbons, if it occurs at all, is rendered uniform. The standard itself should be made from a large number of different drillings. A. G. L. Note on the Estimation of Silicon in Forge-Iron.George Frederick Horsley. (Chem. News, lxxxviii. 136.) -The following process is said to avoid both the liability towards explosive spirting in the preliminary evaporation to dryness usual in most methods, and the formation of gelatinous silica. One gramme of the forge-iron is boiled with 10 C.C. dilute sulphuric acid (1 : 4) and 15 C.C. hydrochloric acid until fumes of sulphuric acid are evolved; 100 C.C. water and 10 C.C. hydro- chloric acid are then added, the whole is boiled and filtered, the residue being washed once with 5 C.C. hydrochloric acid and four times with water, dried, and ignited. A. G. L. A Colorimetric Method for the Determination of Small Quantities of Potassium. (Journ. Amer. Chem. SOC., xxv. 990.)-The nlethod depends on the precipitation of the potassium with chloroplatinic acid and the colour produced by subsequently reducing the potassium chloroplatinate with stannous chloride in the presence of hydrochloric acid.A standard solution is used for corn- parison, made by dissolving 0.518 gramme of potassium chloroplatinate in 100 C.C. water, and diluting 1 C.C. of this t o 100 C.C. ; 1 C.C. of the dilute solution corresponds to 0.00001 gramme potassium oxide. The stannous chloride solution used is made by dissolving 75 grammes of tin in 400 C.C. of hydrochloric acid, the solution being kept in a closed bottle over a piece of tin. The method is carried out by dissolving the precipitate of potassium chloroplatinate, obtained in the ordinary course of analysis, in boiling water, making the solution up to 100 or 200 c.c., placing 50 C.C.of this in a cylinder and adding 3 C.C. of the stannous chloride solution, the colour produced being compared with that produced by known quantities of the standard solution when similarly treated. According to the values given, the method gives good results for quantities of potassium oxide of from 1 to 10 parts per million in the original 100 or 200 C.C. Lucian A. Hill. A. G. L. The Rapid Precipitation of Metals Electrolytically. Franz F. Exner. (Journ. Amer. Chem. SOL, xxv., 896.)-The author makes use of an anode consisting of a spiral of heavy platinum wire 2 inches in diameter, which is caused to rotate atTHE ANALYST. 329 a speed of 500 or 600 revolution8 per minute. Before each determination the electrolyte, the volume of which is kept between 115 and 125 c.c., is heated almost t o boiling, the high current employed keeping the liquid hot during the electrolysis without further heating.The N.D.,oo of the current is usually about 5 amperes at At the end of the electrolysis the rotator is stopped, the current reduced, and the cathode washed and weighed as usual. Using a current of 5 amperes and 12 to 18 volts, 0.25 to 0.5 gramme of copper can be deposited in this way in less than 15 minutes from solutions containing 1 C.C. sulphuric or nitric acid or larger quantities of ammonium sulphate and ammonia 01- ammonium nitrate and ammonia. I n cyanide solutions containing the least possible quantity of potassium cyanide necessary for complete solution, the time required is eighteen minutes when a current of 6 amperes and 18 volts is employed. For nickel, a current of 5 amperes and 10 volts is used; 0.5 gramme of the metal is deposited in seven teen minutes from solutions containing ammonium sulphate, chloride, or acetate and ammonia.Nickel cannot be deposited from solutions containing ammonium nitrate or potassium cyanide. Zinc can be similarly deposited from sulphate solutions containing sodium acetate and acetic acid or excess of sodium hydrate. In the case of silver, using a speed of 700 revolutions per minute and a current of 2 amperes and 5 Volts, 0.5 gramme can be deposited in less than ten minutes from a cyanide solution. For bismuth the high speed of 700 to 900 revolutions should be used, 0.5 gramme of bismuth requiring eighteen minutes for precipitation from a solution containing a small excess of free nitric acid, using a current of 1 ampere and 2.5 volts.The deposition is also very satisfactory when a weighed quantity of mercurous nitrate is added to the solution, a current of 4 to 5 ampdres and 8 to 12 volts being used. The two metals are deposited together as a firm adherent amalgam. Mercury itself required only seven minutes for deposition from a nitric acid solution, a current of 7 amperes and 12 volts being used. Cobalt is best precipitated from a sulphate solution contain- ing sodium and ammonium acetates and a large excess of ammonia with a current of 5 amperes and 7 to 10 volts, the time being twenty-two minutes for 0-5 gramme of metal. Cadmium can be deposited from solutions containing a small quantity of free sulphuric acid or sodium acetate and potassium sulphate, the best results being given by alkaline cyanide solutions. The time required for 0-55 gramme of metal is ten to fifteen minutes, using a current of 5 amperes and about 8 volts.Iron requires about twenty-five minutes for 0-25 gramme in ammonium oxalate solution, a current of 7 amperes and 7.5 volts being used. For the deposition of lead as dioxide a roughened platinum dish is used. (Apparently the cathode was rotated in this case.- ABSTRACTOR.) From a solution containing 20 C.C. of nitric acid, a current of 10 amperes and 4.5 volts deposits over one gramme of PbO, in fifteen minutes in the form of a black adherent deposit. Manganese cannot be deposited in this way.For molybdenum a solution containing potassium sulphate and a small excess of sulphuric acid is used, 0.22 gramme of molybdenum trioxide being deposited in twenty minutes by a current of 4 amperes and 15 volts with a speed of rotation of 300 to 400 revolutions per minute. Tin, in the form of ammonium stannous chloride to which a large excess of ammonium oxalate is added, requires twenty minutes for one gramme of metal pressure of up to 18 volts. In alkaline potassium cyanide solution the method fails.330 THE ANALYST. with a current of 5 amperes and 4.5 volts, the number of revolutions being 300 per minute. For gold a cyanide solution is used, seven minutes being necessary to precipitate 0.145 gramme by means of a current of 5 amperes and 11 volts.Antimony is deposited from a chloride solution to which sodium hydroxide, sodium hydro- sulphide, and potassium cyanide are added; 0.3 gramme is deposited in eighteen minutes by a current of 5 ampAres and 4-5 volts. With arsenic the method fails. Copper may be separated by this method from nickel in a solution of the nitrates to which ammonium nitrate and a very small quantity of nitric acid have been added. Copper may also be separated from zinc, and the author intends working out other separations. A. G. L. Contributions t o the Study of the Quantitative Electrolytic Separation of Metals. P. Denso. (Zeds. f. Elektroch., 9, 463; through Zeits. f. angew. Chem., 1903, XXXV., 850.)-In a normal solution. the potential difference necessary for the decomposition of copper sulphate is 1.48 volts, whereas the sulphates of zinc, cadmium, and nickel require 2.54, 2.24, and 2.09 volts respectively.Copper can, therefore, be readily separated from the other metals by the use of a current a t 2 volts, such as is supplied by an accumulator. Cadmium, like copper, can be deposited from acid solution, provided that the concentration of the acid be not more than twice normal and a higher potential difference (2.6 volts) be employed. Zinc is not deposited from acid solution; hence it is possible from a mixture of the sulphates of copper, cadmium, and zinc to separate first all the copper, and then all the cadmium. Nickel is only deposited from solutions that are very weakly acid. If it be desired to separate it from copper, the latter is first deposited from acid solution, using one accumulator ; then the electrolyte is neutralized with soda, and two accumulators are used, a resistance being introduced into the circuit.A. M. The Electrolytic Separation of Metals. Edgar F. Smith. (Journ. Amcr. Chem. SUC., xxv., 892.)-Silver can be completely separated from selenium in the electro- lytic way, both in potassium cyanide and in nitric acid solution. For the precipita- tion of 0,1341 gramme silver in the presence of 0.2500 gramme sodium selenate, the conditions found to be best were : Potassium cyanide, 3 grammes ; dilution, 150 C.C. ; N.D.lOO, 0.02 ampitre, increased to 0.05 towards the end of the determination ; pressure, 2.5 volts; temperature, 60" C.; time, three hours; or else, nitric acid (specific gravity 1-43), 1 C.C.; N.D.lOO, 0.015 ampitre ; the other conditions remaining the same. From tellurium silver cannot be separated in potassium cyanide solution, the nitric acid method, however, under the above conditions, giving good results. Both mercury and copper can also be separated from selenium in potassium cyanide or nitric acid solutions. The time required is five to six hours for 0.1272 gramme of mercury, and four to five hours f o r 0.0745 gramme of copper, the other conditions being practically the same as before. From tellurium neither metal can be separated when potassium cyanide solutions are used; nitric acidTHE ANALYST. 331 solutions, however, give good results, and copper may also be separated from bobh selenium and tellurium in the presence of sulphuric acid.A. G. L. The Electrolysis of Alkaline Zinc Solutions. R. Amberg. (Ber., xxxvi., 2489 ; through Zeit. f. angezo. Chem., 1903, xxxiv., 828.)-Zinc may be deposited quantita- fively from an alkaline solution, provided that the caustic alkali be present in very large excess. In a solution of pure zinc oxide in caustic potash the amount of potash must be at least forty-five times the equivalent of the zinc. If there be traces of acid also remaining, seventy-five equivalents should be used, or more. Sulphates and chlorides do not affect the character of the deposit, but from solutions containing nitrates the zinc separates in a spongy form. If potassium cyanide be added to the solution, the zinc forms a very bright bluish deposit, especially if the liquid be heated to boiling before switching on the current.The addition of potassium cyanide retards the deposition considerably, however. At 20" the minimum potential difference required is 2.6 volts; when the cathode is entirely covered with zinc the voltage rises to 3.0 or 3.1. I t is advisable to start the electrolysis at 60" to 70" C., and then t o let the temperature fall spontaneously. Under these conditions, if the initial potential difference be 3 volts, the current density will be 1.5 to 3 amperes per 100 square centimetres. During the cooling the current should be gradually diminished to 0-5 ampAre, but towards the end of the electrolysis it should be raised to above 3 amperes. The deposition of 0.3 gramme of zinc lasts hhree to five hours.I t is not advisable to warm the electrolyte during the whole process, as there would be danger of the metal being deposited in a spongy form. To avoid the inconvenience of having to coat with copper the dish that is used as cathode, the author uses dishes made not of platinum, but of nickel, which does not alloy with the zinc, and can be freed from it by treatment with hydrochloric acid. The anode is made of platinum. A. M. The Action of Ammonium Persulphate on Metallic Oxides. A. Seyewetz and P. Trawitz. (Bull. SOC. Chim., 1903, xxix., 868-873.) -When ammonium persulphate acts on protoxides there may be either a simple liberation of ammonia and probable formation of the corresponding persulphate, or a sesquioxide or peroxide may be produced. The former reaction takes place in the case of potassium, sodium, barium, strontium, calcium, magnesium, and zinc oxides, whilst iron, nickel, cobalt, copper, manganese, chromium, silver, mercury, and tin protoxides are converted into the higher oxides. This reaction can also be utilized as a simple method of preparing pure precipitated lead peroxide.By the action of ammonium persulphate on sesquioxides and peroxides part of fhe ammonia, of the persulphate may be converted into nitrogen with the formation of the corresponding sulphate, as in the case of nickel and copper sesquioxides ; or there may be a liberation of oxygen and formation of the sulphate corresponding to &he higher oxide; or there may be complete oxidation with formation of peroxides, a s in the case of chromium and manganese.If manganese peroxide be boiled with332 THE ANALYST. excess of a solution of ammonium persulphate the oxide dissolves, yielding a violet solution with the characteristics of permanganic acid. This reaction may be used a8 an extremely sensitive test for manganese, the violet coloration being given by solutions containing 1 part of manganese in 100,000. C. A. M. The Titration of Sulphuric Acid with Benzidine Hydrochloride. W. J- Muller and E. DQrkes. (Zeit. anal. Chem., 1903, xlii., 477-492.)-Benzidine hydro- chloride undergoes dissociation in water yielding an acid solution. It does not dissolve completely owiog to the separated benzidine base being only sparingly soluble; but by the addition of hydrochloric acid dissociation is checked and the salt kept in solution.On adding sulphuric acid to such a solution benzidine sulphate i s precipitated, whilst the liquid shows the same amount of acidity as before : C,,Hs(NH2),.2HC1 -j- H2S04 = C,,Hs( NH,),.H,SO, + 2HC1. If instead of free sulphuric acid an alkali-metal sulphate be added, the corre- sponding chloride is left in solution, and the amount of sulphuric acid precipitated can be determined by titration, as described in a previous communication (ANALYST, xxvii., 290). Hence the method demands the presence of a neutral salt, which can be insured by first neutralizing the solution with standard sodium hydroxide solution. Thus the total acidity and the sulphuric acid can be determined in one operation. For the preparation of pure benzidine hydrochloride the benzidine base is dissolved in dilute hydrochloric acid and precipitated by concentrated hydrochloric acid, the precipitate being purified by repeated reprecipitation in the same way.Finally, 25 grammes of the salt are dissolved in 1 litre of water with the aid of 30 c. c. of hydrochloric acid of specific gravity 1.05 ; whilst for the precipitation of smaller amounts of sulphuric acid a reagent containing 7 grammes of the hydrochloride per litre is used. Test experiments on the lines previously described have shown that the addition of too large an excess of the reagent causes the results to be somewhat higher, this being attributed to the greeter absorption of benzidine hydrochloride by the pre- cipitate. In general the results tabulated by the authors are about 1.1 per cent. too high from this cause, but as the amount of absorption is a constant factor when solutions of approximately the mrne strength are used, and an excess of 10 to 20 c.c of the reagent added, the error can be eliminated by determining the relative value of the standard alkali solution in terms of sulphuric acid under the conditions of the experiment.With this correction the results are practically identical with the theoretical amounts. The sulphuric acid in ammonium sulphate may be determined in the same way as in sodium sulphate, with the substitution of luteol for phenolphthalein as indicator. I n the case of ordinary alum, a weighed quantity of the salt should be dissolved in water, and the sulphuric acid combined with the aluminium determined by treating one part of the solution with barium chloride, and titrsting with sodium hydroxide solution the aluminium chloride formed.In the other portion of the solution the sulphuric acid combined with the potassium is found by the benzidine method. In The maximum solubility of the salt in water is 30 grammes per litre.THE ANALYST. 333 applying the method to zinc sulphate, the zinc must first be separated by adding ammonia to the boiling solution, and the excess of ammonia removed from the filtrate by boiling. It is also necessary to remove iron or manganese from iron ammonium sulphate or manganese sulphate. For this purpose the iron is first oxidized by the addition of a few drops of hydrogen peroxide and precipitated with ammonia, whilst manganese is separated in a similar manner. C.A. M. The Titration of Sulphuric Acid with Benzidine Hydrochloride. F. Raschig. (Zeits. f. angew. Chem., 1903, xxvi., 617.)-The method, which is a modification of that of Miiller and Durkes (see preceding abstract), depends upon the fact that benzidine sulphate is practically insoluble in cold water containing an excess of benxidine chloride, and that benzidine does not affect phenolphthalein. The reagent is prepared by dis- solving 18.5 grammes of commercial benzidine and 200 c . ~ . & HCl in 1 litre of water, filtering, and diluting to 10 litres. It is not advisable to use a stronger solution, for there would be danger of benzidine hydrochloride being carried down with the benzi- dine sulphate. Of this solution 150 C.C.are taken for each decigramme of H2S04. The precipitation is complete in five minutes, and the liquid is then filtered with the aid of a pump. The precipitate is washed with not too much water, then it is trans- ferred to a flask, 50 C.C. of water are added, a rubber cork is inserted, and the flask is well shaken. NaOH is run in until the red colour no longer disappears rapidly. The contents of the flask are then heated t o 50" C., and the titration is completed. The temperature may be finally raised to looo. Nitric acid does not interfere with the reaction, but ferric salts cause the results to be low, and must be removed by precipitation with ammonia. The presence of starch in solution prevents complete precipitation of the H,SO,. Miiller (Zeits. f. angew.Chem., 1903, xxvii., 653), in objecting to Raschig's modifi- cation, states that benzidine sulphate is somewhat soluble in pure water, and that consequently the results are affected by the extent to which the precipitate is washed, as is shown by a number of results quoted. Muller, therefore, prefers to adhere to his original plan of taking an aliquot portion of the mother liquor and titrating that. The solution to be examined is rendered neutral to phenolphthalein, and the H,SO, is precipitated with an excess of a standard solution of benzidine hydro- chloride, either in the cold, as recommended by Raschig, or hot, with a stronger standard solution. The solution is then allowed to cool, is made up to a known volume, and an aliquot portion of the clear filtrate is taken and titrated with standard caustic soda solution, using phenolphthalein as indicator.The presence of excess of benzidine hydrochloride prevents any of the sulphate passing into solution. The diminution in the titre gives the quantity of sulphuric acid. Phenolphthalein is now added, and A. M. Identification of Portland and Slag Cement. H. Seger and E. Cramer. (Chem. Zeit., 1903, xxvii., 879.)-It has recently been stated that Portland cement cannot be chemically distinguished from cement made from blast-furnace slag except by complete quantitative analysie. This, however, is incorrect, for the two materials.334 THE ANALYST. differ greatly in the amount of water they take up and in the extent to which they are soluble in water. To determine the former, 50 grammes of the sample after passage through a 10,000 mesh sieve should be boiled in a dry flask with 100 C.C.of water for three hours over gauze, loss by evaporation being constantly made good, and the vessel being periodically agitated to prevent a formation of lumps. The solid residue should be collected on a filter, washed twice with hut water, and dried at 110" or 120" C. In 1 or 1.5 grammes of the product so obtained the loss on ignition (b., water of hydration) should be ascertained. Six samples of Portland cement gave losses of from 10.19 to 13.10 (mean, 11.46) per cent. ; three specimens of slag cement gave 0.70 to 0.84 (mean, 0.78) per cent. To determine solubility, 1 to 1.5 grammes of cement and slag which has been ignited at a moderate temperature and passed through a sieve having 10,000 meshes per square centimetre is shaken at intervals for three hours with 3 litres of freshly- boiled and cooled water in a corked flask.The residue is collected on a, paper, washed two or three times with cold water, and dried. The solid matter is brought into a platinum crucible, the paper burnt off, and the whole is ignited and weighed. By subtraction the six samples of Portland cement mentioned above gave from 28.7 to 42.8 (mean, 37.15) per cent. of soluble matter; the slag cements gave from 1.2 to 4.56 (mean, 2.33) per cent. (cf. ANALYST, this vol., p. 308). F. H. L. Standardization of the Permanganate required for estimating Calcium or IOxalic Acid. H. Walland. (Chem. Zed., 1903, xxvii., 922.)- Owing to the solubility of calcium oxalate in water and in the liquids from which it has been precipibated, %he true amount of calcium or of oxalic acid originally in solution will not be given correctly when the precipitate is titrated with permanganate which has been standardized in any of the usual ways.For instance, a reagent was made up which was intended to be a little less than decinormal in strength ; this was Standardized upon iron flower-wire, pure calcium oxide, oxalic acid, ferrous ammonium sulphate, and Rust's MnC,O, + 2H,O. In terms of decinormal strength the permanganate gave with Fe 89.36 per cent. ; with oxalic acid, 89-73 per cent. ; with Mohr's salt, 90.17 per cent. ; and with Rust's salt, 90.66 per cent.': concentration. When, however, the calcium oxide was dissolved in hydrochloric acid, precipitated with ammonium oxalate, and the calcium oxalate was washed with water till the chlorine reaction had disappeared, and when the washed oxalate was dissolved in dilute sulphuric acid, and thbn used to determine the strength of the same permanganate, its degree sf concentration in terms of a decinormal reagent was found to be 92.01 per cent.* The author, therefore, recommends that whenever permanganate is to be employed for estimating the calcium or the acid in calcium oxalate, it shall be standardized on any suitable pure compound of calcium which has been converted into oxalate, and washed in the manner above indicated, calculation being then made, not upon the weight of oxalate actually titrated, but upon the calcium which * The author reniarks that when the second of these figures is corrected for the error introduced by the solubility of the oxalate precipitate, it agrees very closely with the first ; and, therefore, Rdst's inanganous oxalate is shown to be a very good substance for the standardization of permanganate for ordinary analytical operations.THE ANALYST.335 has left that particular weight of oxalate. Experiments show that when a quantity of calcium oxide is treated in this way the loss of oxalate in the washing liquors-- the process being continued just to the removal of chlorine-is remarkably constant, representing from 1.3 to 1.6 milligrammes of CaO in handling amounts of from 0.058 to 0.238 gramme of oxide. The operator may start with calcium carbonate or a, pure solution of calcium chloride in the above process. The plan adopted by T. W. Richards, McCaffrey, and Bisbee for diminishing the solubility of calcium oxalate-viz., washing it with a liquid containing a little ammonium oxalate-is obviously not available for the present purpose. P. H. L. The Technical Estimation of Ozone, 0. Brunck. (Zeits. fiir angew. Chem., 1903, xxxvii., 894.)--It has been shown by Ladenburg and Quassig that, in the estimation of ozone by the potassium iodide method, accurate results are only obtained if the potassium iodide be neutral whilst the ozone is acting upon it (see ANALYST, vol. xxvii., 35). For carrying out the estimation the author has devised the apparatus shown in the figure. This consists of a, conical flask of about 600 C.C. capacity, into the neck of which is ground a stopper. Through the stopper passes a tapped graduated funnel, on to the tube of which is fused a side-kube with cock in such a manner that liquid will not flow into it from the funnel. At the side of the neck of the flask a tube is fused, to which corresponds a hole in the stopper. Two projections D, D enable the stopper to be turned round. The exact capacity of the flask is ascertained by weighing it full of water. The various glass joints should be air-tight ; but if it be necessary to use a lubricant, concentrated sulphuric acid should be employed for this purpose. When using the apparatus the cock B is turned off and the gas to be examined is caused to pass in through A and out Ghrough C until all the air has been swept out of the flask. The cock A is then turned off and a known volume of po- tassium iodide solution is allowed to run in, the gas dis- placed being permitted to escape through C. The stopper is then turned round so as to close the exit tube, and the cock B is also turned off. The action of the ozone upon the potassium iodide is almost instantaneous, but the flask should be well shaken to absorb mist and vapours of iodine. The stopper is then taken out, and the contents of the flask are titrated with thiosulphate solution, a quantity of sulphuric acid being first added equivalent to that of the potassium iodide. A. 11.

ISSN:0003-2654    

DOI:10.1039/AN9032800323

出版商:RSC    

年代:1903

数据来源: RSC

摘要:

336 THE ANALYST APPARATUS. An Improved Cryoscope. E. Gilson. (Chenz. Zeit., 1903, xxvii., 926.)--This apparatus consists essentially of a Beckmann observing-tube fitted with a mechanical agitator, and cooled by the evaporation of ether. The construc- tion of the inner part of the apparatus is shown by the small left-hand drawing. The tube on the right is of copper, terminating in a ring drilled with fine holes. Through this, air dried over sulphuric acid is drawn through ether by the aspirating power of a water-pump attached to the bent tube, provided with a tap, represented at the left side of the beaker. The latter is provided with a felt jacket, and is adjusted into its correct position with reference to the agi- tator by means of the three centring screws of the ring on the cast-iron base.The motor is a turbine, connected to the counter shaft with a rubber belt running over coned pulleys, so that the speed of the agitator may be controlled either by checking the supply of water or by altering the position of the belt. The active part of the agitator is a platinum coil surrounding the bulb of the inner thermometer, the travel of which may be adjusted by altering the place of connection between the prolongation of the agitator and the vibrating rod driven by the eccentric pin. The temperature in the jacket depends on the speed at which the water-pump works; while if the ether is replaced by water at the proper tempera- ture, the whole apparatus may be employed for determining freezing-points at temperatures above the normal.It is made by F. Hugershoff, of Leipzig. F. H. L.TEE ANALYST. 337 A Non-MetaUic Drying Oven. (1) H. Seger and E. Cremer ; (2) W. Thorner. (Chem. Zeit., 1903, xxvii., 835 and 860.)-The former authors descrihe a drying-oven made of earthenware or porcelain, which is specially convenient for operations in which acid vapours are evolved. As shown in the illustration, it is built out of two of the unglazed earthen cap- sules used in the porcelain industry. These are placed upside down, and serve as base and cover respectively, and between these a suitable number of rings, also used in the same industry, are in- serted to give the necessary height. Holes are drilled in the lower dish for the air-supply to the burner, for the rubber connection, and for the burner tube; and holes are similarly drilled in one of the rings for the escape of combustion products. The partition A is of cast-iron, made in concentric portions.If it is requisite to keep all the combustion products of the gas out of the drying space, a solid sheet-iron disc is laid on it. B is a sheet-iron plate perforated to distribute the heat. As the actual heating surface is metal, the oven soon becomes hot, and as its walls are non- metallic it retains its heat well. The porosity of the material allows the moisture and acid vapours to escape readily. A thick earthenware plate supports the whole, and prevents damage from heat to the laboratory bench. Referring to this apparatus, Thorner remarks that he described an oven con- structed of similar materials for the same purpose in 1888.His oven has been in use ever since, and it is quoted in most of the dealers' lists. F. H. L. The Testing of Coal Tar and Oils and an Improved Testing Still. H. W. Jape. (Joum. Amer. Chem. SOC., xxv., 814.)--The still used for the tests is of thick copper with straight sides to facilitate cleaning. The upper edge is surrounded with a heavy turned ring, on which the brass lid is clamped by a single clamp passing over the top, a paper washer being placed between the two metal surfaces. The condenser consists of a copper trough open at the top, through which passes a glass tube 24 inches long. At the beginning of the distillation the trough is filled with cold water. When naphthalene commences to aooumulate in the tube the water is warmed by means of a small burner, and towards the end of the distillation the trough is emptied by mean8 of a small cock.The still is heated by a ring-burner, which at first is placed very near the top of the still, and is gradually lowered, in order t o prevent foaming over. For water determinations 500 C.C. of the tar are distilled in a still having a capmity of 1,000 c.c., while for a complete examination 1,000 C.C. are distilled in a 2,000 C.C. still. In this case, as soon as all the water has come over, which will be the case when the thermometer reads 200' C., the oil which has distilled over is separated from the water and added to the COOl8d residue in the still, after338 THE ANALYST. which distillation is recommend, the results now obtained being on the dry tar. In the case of some tars, which can onlybe freed from water with great difficulty, crude toluene or other hydrocarbon boiling between looo and 200" C. may be added to Ring Burner B" 0 E facilitate the distillation if only water is to be determined. The residue in the still may be examined from time to time by removing a plug in the lid and taking out a sample by means of a glass rod. A. G. L. _ _ _ ~ ~

ISSN:0003-2654    

DOI:10.1039/AN9032800336

出版商:RSC    

年代:1903

数据来源: RSC

摘要:

338 THE ANALYST. REVIEWS. THE OPTICAL ROTATING POWER OF ORGANIC SUBSTANCES AND ITS PRACTICAL APPLICA- TIONS. By Professor HANS LANDOLT, assisted by Drs. 0. SCHONROCK, P. LINDNER, F. SCHUTT, L. BERNDT, and T. POSNER. Authorized English Translation of the second edition. By Professor J. H. LONU, North-Western University. (Chicago, Easton, Pa. : The Chemical Publishing Go., 1902. Pp. 751, with Index. Price $7.5.) The first edition of Professor Landolt’s book was published in 1879, shortly after the announcement of the well-known hypothesis of vm’t Hoff and Le Be1 on the relation between the optical rotatory power and the atomic constitution of those carbon compounds which exhibit the phenomenon known as optical activity ; an English translation followed in 1882, under the title “ Handbook of the Polariscope,” which has, however, been out of print for some years.The numerous additions to our knowledge of the subject from the standpoints of chemistry, physics, and phyrJiology induced the author to prepare a second edition in co-operation with the specialistsTHE ANALYST. 339 above named. This appeared in 1898, and the volume before us is a translation, with some addenda to bring the work up to date. The theoretical bearing of circular polarization is known to every student of organic chemistry. We owe to its study the origin and development of that interesting branch of chemical science ‘‘ stereo-chemistry.” But before the import of optical activity had been worked out from the theoretical side-in fact, immediately following the discoveries of Biot and Seebeck in 1815 that oil of turpentine and aqueous solutions of sugar and of tartaric acid rotate the plane of polarized light-it was burned to practical use in quantitative analysis.For many years polarimetric methods have bsen employed in the investigation of sugars, alkaloids, and essential oils, so that a spacial work on the subject has becoms almost a necessity to the modern analyst. From an intimate acquaintance during the past four years with the German edition of Professor Landolt’s book, we are of opinion that a more thorough monograph has never been written on any subject. We feel aonfident that the English translation will be in even greater demand than was that of the first edition, a demand, in fact, commensurate with the increased development of the subject and scope of the work.The applications of the polarimeter in analysis are likely to increase, in view of the fact that methods based upon them are, as a rule, very convenient on account of their simplicity, besides which they may often be resorted to as confirmatory of the results furnished by chemical means. Still, there are pitfalls into which the unwary may easily be led. It is therefore essential that those who use the polarimeter should have a thorough acquaintance, not only with its general principles, but also with the construction of the numerous forms of the instrument. The fullest information on these and other points will be found in the present volume. I t is divided into six parts under the following heads: (1) ‘( General Conditions of Optical Activity,” (2) “ Physical Laws of Circular Polarization,” (3) “Numerical Values for Specific Rotation,” (4) ‘‘ Apparatus and Methods for the Determination of Specific Rotation,” (5) “ Practical Applications of Optical Rotation,” (6) ‘‘ Constants of Rotation of Active Bodies.” A.R. L. INTRODUCTION TO THE RARER ELEMENTS. By PHILIP E. BROWNINU, Ph.D. (New York : John Wiley and Sons. London : Chapmitn and Hall. 1903. Price 6s. 6d. net.) The book is well adapted to fulfil its purpose of serving as an introductory hand- book in the study of the rarer elements. The historical notes especially are well written and suggestive, and the student who can find time to work through the experimental portions will acquire a valuable knowledge of an interesting branch of inorganic chemistry.The descriptive parts are not so good, an undue amount of space being devoted to the cataloguing, in tabular form, of the minerals in which the elements occur, and of the various salts which they form. Besides omitting some important reactions and methods, such as the strychnine test for cerium and Muth- mann and Bohm’s method of fractionating the gadolinite earths, the author not infrequently fails to distinguish between methods of separation which are analytically valuable and those possessing only a secondary interest. To radium more than a mere passing mention appears to be due, and the position allotted to this element in340 THE ANALYST. the chapter on unconfirmed discoveries eppears scarcely appropriate. these minor blemishes, however, the volume is well worth studying.Apart from A. G. L. ANIMAL AND VEUETABLE FIXED OILS, FATS, BUTTERS, AND WAXES. By C. R. ALDER (London : Charles Griffin and Co., Mr. C. A. Mitchell has not only edited this, the second edition of Dr. Alder Wright’s book, and brought it up to date, but has largely extended the scope of the work, which may now no longer be regarded as a manual for the use of the manu- facturer and technologist only, but also as one of value to the analyst. Several new sections have been added, and, so far as we are in a position of judging, the technical part of the matter may be relied upon as containing the newest information which is to be found disseminated in the various journals dealing with chemical subjects. To the readers of the ANALYST Mr.Mitchell’s endeavour to convert the book to some extent into a laboratory text-book is of the main interest. He has followed the example set by Benedikt and Lewkowitsch of giving to each kind of oil or fat a separate description and table of composition, and although to a great extent the subject thus treated overlaps the corresponding chapters of the other works referred to, no one can regret this duplication when he considers the rapidity with which new material has latterly appeared, and this necessarily has to be collected from the numerous journals over which it is distributed originally. While cordially acknowledging the pains Mr. Mitchell has taken as a bibli- ographer, we cannot avoid pointing out the fact that his treatment of some at least of the analytical processes is not so careful as might be desired.His description, for instance, of the method for determining the Reichert value of fats would necessarily lead, if followed, t o the loss of a considerable portion of volatile esters. Again, his suggestion to boil the solution of a soap after acidification for the determination of the insoluble fatty acids would be almost certain to lead to a catastrophe. Of the now numerous methods for determining boric acid in butter only a single one is mentioned-namely, distillation with methyl alzohol. The appearance of another book dealing with this subject is a most pleasing indication of the chemical activity in a field which has been for many years one of the most neglected in chemical research, though it is one which yields important results to every intelligent investigator, not only from a, scientific point of view, but which may be possibly of technical value. We are evidently only on the fringe of the recognition of the real nature of fats and oils, and hardly a month now elapses without a discovery of some unexpected compound glyceride contained in, or constituting the greater portion of, some fat or other, the chemical constitution of which chemists thought they had long been familiar with. The old opinion, which has far too long held the field, that fats were mere mixtures of triglycerides, is now fully exploded, and new roads must be apparent to everyone whereby this vast field of research can be opened and explored. A portrait of the late Dr. Alder Wright forms the frontispiece of the work, and will be most welcome to the many who valued Dr. Wright’s friendship. WRIGHT and C. AINSWORTH MITCHELL. 1903. Price 25s. net.) w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9032800338

出版商:RSC    

年代:1903

数据来源: RSC