摘要:

THE ANALYST’. DECEMBER, 1903. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. THE monthly meeting of the Society was held on Wednesday evening, November 4, in the Chemical Society’s Rooms, Burlington House. I n the absence of the Pre- sident, the chair was occupied successively by Mr. Sidney Harvey and Mr. Alfred H. Allen. The minutes of the previous meeting were read and confirmed. Certificates of proposal for election to membership in favour of Meesrs. H. Har- man and C. J. Waterfall were read for the second time; and certificates in favour of Messre. Frederick Hudson-Cox, F.I.C., 46, St. James’s Road, Brixton, chemist to the Vinolia Co., Ltd. ; Norbert van Laer, 69, Calais Road, Burton-on-Trent, chemist to Meesrs. Truman, Hanbury, Buxton and Co., Ltd. ; James Scott Maclaurin, D.Sc., analyst to the Mines Department and to the Public Health Department of the New Zealand Government, Colonial Laboratory, Wellington, New Zealand ; and Thomas Arthur Nightscales, analytical and consulting chemist, Chapel Lane, Hull, were read for the firet time. Mesere. W. Everitt and L. M. Nash were elected members of the Society. The following papers were read : ‘( The Salinity of Waters from the Oolites,” by W. W. Fisher, M.A. ; “Some Indian Oils,” by J. Lewkowitsch, M.A., Ph.D.; ‘‘ Differentiation of Linseed Oil from Boiled Oils,” by J. Lewkowitsch, MA., Ph.D. ; and a ‘‘ Note on the Purification of Hydrochloric Acid and Zinc from Arsenic,” by L. T. Thorne, Ph.D., and E. H. Jeffers.

ISSN:0003-2654    

DOI:10.1039/AN9032800341

出版商:RSC    

年代:1903

数据来源: RSC

摘要:

342 THE ANALYST. SOME INDIAN OILS. BY DR. JULIUS LEWKOWITSCH, F.I.C. (Read at the Meeting, November 4, 1903.) PONGAM OIL. THIS oil is obtained from Pongam beans, the fruit of the Poitgamia ghbra, Vent. (Dahlbergia arborea, Roxb.), a tall tree growing all over East h d i a from the Central and Eastern Himalayas to Ceylon and Malacca. By extracting the beans with ether I obtained 33.7 per cent. of the oil, which is known under the following native names : Kanoogamanoo, Kanoogoo, Kanuga-Karra, Kanuga-Chettu, Kanugoo. The oil is also known under the names Korung oil and Kagoo oil. I suggest the name Pongam oil. At 15OC. the oil is a buttery mass of a dirty yellowieh colour. According to Lepine (Pharm. Jozwn., (3), xl., IS), the seeds yield 27 per cent. of a yellow oil of the specific gravity 0.945, solidifying at 8” C.The authors of the (‘ Pharmacographia Indica ” state (see Watt’s Dictionary of the Economic Products of India,” VI., i., p. 322) : The oil which we have examined (called Houge oil in Mysore) and expressed purposely from fresh seeds was thick, of a light orange brown colour, and bitter taste. I t yielded 93-3 per cent. fatty acids, melting at about 30” C. . . . The bitter principle of the oil appears to reside in a rosin, and not an alkaloid.” I was enabled to examine side by side with the oil I extracted from the seeds another specimen I obtained from India. The following are the characteristics of Pongam oil : The specific gravity at 18” C. was 0.9458. Extracted in the Specimen Laboratory with obtained from Ether. India. 0.9240 0.93693 Specific gravity at 40” C.(water at 40” C. = 1). .. Saponification value ... ... ... ... 178 183.1 Unsaponifiable ... ..- ... ... 9.22 7; 6.96 % Refraction (butyro-refraotometer) ... ... 78.0 “degrees.” 70.0 “degrees.” Free fatty acids (as oleic) ... ... ... 3.05 % 0.5 % 0.9352 Specific gravity at 15” C. (water at 15” U. = 1). .. Iodine value ... ... ... ... ... 94.0 89.4 Reichert-Neissl value ... ... ... ... - 1.1 Melting-point of fatty acids, freed from un- - - saponifiable ... ... ... ... ... 44.4” c. The oil is used in India for illuminating and medicinal purposes. As it can ba obtained in large quantities, it should be possible to find technical application in the soap and candle industries. MARGOSA OIL (VEEPA OIL, VEPPAM F.4T, NEEM OIL).This oil is obtained from the seeds of Xelia azedcirach (Melia Amdircrchta iizdicn, Juss.), a large tree forty to fifty feet in height, common in its wild, or more often cultivated state, throughout the greater part of India and Burma.TEE ANALYST. 343 The oil has been described somewhat fully in the Pharm. Journ. by Surgeon- Major Warden (see Watt’s ‘‘ Dictionary of the Economic Products of India,” vol. v., The specimen submitted to me was solid at the ordinary temperature, and gave p. 211). the following characteristics : Specific gravity at 40” C. (water at 40” C. = 1). .. Specific gravity at 16” C. (water at 16” C. = 1). .. Saponification value ... ... ... ... ... 196.9 Iodine value ... ... ... ... ... ... 69.6 Reichert-Meissl value ... ... ... ... ...1.1 Refraction in butyro-refractometer ... ... ... 52 “degrees.” “Titer ” test of fatty acids ... ... ... ... 42-0” C. ... 0.9023 ... 0.91423 BEN OIL. ,4s it seems to be rather difficult to obtain the oil oommercially, I thought it might be of interest to record a few numbers obtained in the examination of a genuine sample from Moringa Pterygosperma, s. oZeiferu, supplied to me from the Jamaica Section of the Imperial Institute by the kindness of Professor Dunstan. The chief interest in this oil depends on its low iodine value ; this explains why the oil is specially applicable for lubricating watch-springs and other delicate machinery. This oil has been described by Mills.::: The following properties were determined : Specific gravity at 15’ C. (water at 15” C.= 1) ... ... 0.91267 Refraction (butyro-refractometer). .. ... ... 50.0 ‘( degrees.” Iodine value.. . ... ... ... 72.2 !, ,, of the’liquid fktty acids ... ... ... 97-53 ... Through the kindness of Professor Mills, I obtained two specirnent.1 of ben oil, one of which represented the solid portion of ben oil/filtered out at 0” C., and the other the liquid portion. The following characteristics were determined : Portion Solid Freed froiii solid a t 0” C. a t 0” C. Specific gravity at 15” C. (water at 15’ C. = 1) Iodine value ... ... ... ... ... 109.9 111.8 0.91840 0,91998 Refraction in the butyro-refractometer ... 59.0 ‘‘ degrees.” 60.5 ‘I degrees.’’ I further obtained, through the kindness of Professor Mills, a commercial sample of ben oil, for the purity of which he could not vouch.As the quantity was very small, I only determined the refrsction, which was 59 “degrees” in the butyro- refractometer, and the iodine value, which was 112.6. Evidently this also represented a filtered oil. The difference between the genuine sample from Jamaica and the other oils is noteworthy. I need hardly mention that the last-mentioned specimen was not cottonseed oil. * “ Cheinical Aiialysis of Oils, Fats, and Waxes,” second edition, p. 467.344 THE ANALYST. DISOUSSION. The CHAIRMAN (Mr. Allen) agreed with Dr. Lewkowitsch as to the unreliability of the published characters and constants for ben oil. Since the reproduction in “ Commercial Organic Analysis ” of some figures (they were not his own) for this oil, he had had an opportunity of examining a, sample of oil of ben received from the Government authorities in the West Indies, which led him to the conclusion that either the figures and properties of oil of ben had been hitherto misetated or that the oil itself was of very variable character. Dr. LEWKOWITSCH said Dr. Mills had found that the solid portion of a specimen of ben oil had a higher bromine value than the liquid portion. A comparison, which was rather anomalous, of Dr. Mills’s figures with those yielded by the Jamaica oil, however, would seem to indicate that he must have had a genuine sample. The East Indian oil seemed to be still more difficult to obtain, though it was said to be used for perfumery and other purposes.

ISSN:0003-2654    

DOI:10.1039/AN9032800342

出版商:RSC    

年代:1903

数据来源: RSC

摘要:

344 THE ANALYST. THE ESTIMATION O F ARSENIC I N FUEL. BY T. E. THORPE, C.B., F.R.S. (Reprinted, by permission, f r o m the Jozwnal of the Chemical Society, August, 1903.) THE inquiry which followed the lamentable outbreak of poisoning in Lancashire, due to the accidental occurrence of arsenic in beer, has shown that articles of food or drink may become contaminated with arsenic by reason of the presence of that element in fuel. I t has been proved, for example, that malt may become admixed with arsenic owing to arsenical pyrites, and possibly other combinations of arsenic, being contained in the fuel which may have been used in preparing it, and maltsters are now under the necessity of exhrcising care in the selection of the coal or coke to be employed in kilning. I n this communication is given an account of a method of determining the amount of arsenic in fuels which has been worked out in conformity with the recommendation of the Royal Commission on Arsenical Poisoning, that the Board of Inland Revenue should prescribe for the different materials used in the preparation of the individual ingredients of beer an adequate test by which their freedom from arsenic may be ascertained.This method is fairly rapid in execution, is accurate, and it has the further merit of directly distinguishing between the arsenic which is volatilized on burning the fuel and that which remains fixed in the ash. The process consists simply in burning a known quantity of the finely-powdered coal or coke in a stream of oxygen, passing the products of combustion through a euitable absorbing apparatus, and determining the amount of arsenic so absorbed as well as that left in the ash.A piece of hard-glass tube, A , about 60 centimetres long, is drawn out and the drswn-out portion bent, as seen in Fig. 1 (p. 345).THE ANALYST. 345 Ten grammes of the finely-powdered sample of fuel are then introduced into the tube in such a manner that it occupies about 30 centimetres of the length of the tube, leaving empty about 6 centimetres of the tube next to the bent and drawn-out portion. A convenient method of introducing the fuel is to distribute it along a stout glazed cardboard trough or gutter, which can readily be inserted in the tube held in a horizontal position, and with the bent portion pointing vertically upwards.On turning the tube round through 180°, 80 that the bent portion points downwards, the powdered coal falls from the gutter and is loosely distributed along the length of the tube, when the cardboard gutter may be withdrawn. The drawn-out portion of the tube is then connected with the absorption apparatus, B, containing dilute sulphuric acid. A oonvenient form of apparatus consists of a modified De Koninck absorption tube, the straight limb of which contains glass beads or short lengths of thin glass APPARATUS FOR ESTIMATING ARSENIC IN FUEL. FIG. 1. Frc:. 2. FIG. l.-A, Hard-glass tube ; Frc:. 2.-A, Di.;tillation flask ; B, coil- B, absorption tube. deiiser ; C, flask for receiving dis- tillate ; D, funnel. tubing, so as to offer a conaiderable wetted surface to the passage of the gaseous products of combustion.The hard-glass tube, A , is placed in an ordinary combustion furnace and connected with an oxygen reservoir. The burners of the furnace beneath the empty portion of the tube are first lighted, a rapid current of oxygen passing meanwhile through the apparatus. The powdered fuel is then heated at the place where the stream of oxygen first impinges on it. As soon as the combustion has started very little external heat will be required, and the coal or coke gradually burns away without the formation of soot or tarry products. The whole operation is under perfect control, and is finished in from two to three hours, depending on the nature of the fuel. The ash is left in a loose, pulverulent form, and is readily detached from the tube.The arsenic present in the fuel will be found partly in the ash and partly in the constricted end of the hard-glass tube and in the liquid in the absorption apparatus.346 THE ANALYST. To determine the amount of arsenic retained by the ash, this is shaken out into a, Wiirtz flrtak, A , of about 100 C.C. capacity, which is then attached, preferably by means of ground-glass joints, ae shown in Fig. 2, to a small reflux condenser, B, connected with a flask, C, of about 70 C.C. capacity, containing about 10 C.C. of arsenic-free hydrochloric acid (specific gravity 1.1). Into the flaek, A , containing the coal ash, 25 C.C. of areenic-free hydrochloric acid, containing 0-25 C.C. of bromine, are added by means of the ground-in tap-funnel, D.In practice it is convenient to prepare zb stock of brominated hydrochloric acid by adding 1 C.C. of bromine to each 100 C.C. of acid (specific gravity 1.1). The flask is then heated and the liquid maintained in gentle ebullition for about two hours. After cooling, about 1 gramme of potassium metabisulphite is added, and the liquid again heated until the free bromine disappears. The solution is filtered from the suspended silica, which, together with the small filter, is washed with the acid contained in the small flask, C. Unless the silica is removed, the solution is apt to boil irregularly, and it is difficult to distil it properly. The filtered solution is returned to the distilling flask, still connected with the reflux condenser, and boiled to expel the sulphurous acid.The condenser is then reversed and the liquid distilled into the small flask, C, the distillation being continued until the residue in the flask, A, is syrupy, when EL further addition of 10 C.C. of hydrochloric acid is made to the residue and the solution again distilled. The total distillate is made up to 100 c.c., and an aliquot portion taken for testing. This is transferred to a small porcelain dish, 5 C.C. of pure nitric acid (specific gravity 1-4) and 2 C.C. of pure concentrated sulphuric acid are added, and the solution evaporated until fumes of sulphuric acid are freely evolved. The dish is cooled, and the liquid diluted with about 20 C.C. of water and transferred to a small flask. Half a gramme of potassium metabisulphite is added and the solution boiled until free from sulphurous acid, and when cold used for the test.To determine the amount of arsenic which is volatilized in the combustionof the fuel, the acid in the absorption tube is poured into a small beaker, and the1absorption tube rinsed with a small quantity of water. The end of the hard-glass tube is then well washed by repeatedly drawing the liquid in the small beaker into it. Finally, the hard-glass tube is rinsed out with a little more acid, and the whole of the solution and washings made up to 50 C.C. Of this, 25 C.C. are taken and used directly for the test. The estimation of the arsenic in the solutions may be made by mcans of an electrolytic method for detecting and estimating small quantities of arsenic, which has been worked out in this laboratory, and which is the subject of a subsequent communication; or it may be made by means of the Marsh apparatus, but in that case it is unnecessary to remove the hydrochloric acid by evaporation with nitric and sulphuric acids.In either case the amount of arsenic obtained is estimated by comparison with arsenic deposits obtained from known quantities of arsenious oxide. To test the method, a sample of coal, about 4 pounds in weight, taken from EL Lincolnshire malting, was broken into small pieces; a portion, about 1 pound in weight, was reduced to a fine powder by grinding in a small so-called Kugelmuhle,THE ANALYST. 847 Arsenious Oxide found. Volatile ... ... ... 0.000768 Fixed ... ... ... 0.01058 0.01 1348 Arsenious Oxide taken. In 0.0188 gramme of pyrites In 10 grammes of coal ...0.000045 0.010791 0.010836.348 THE ANALYST. EXPERIMENT 111.-Carried out as Nos. I. and II., except that 0-0186 gramme of The results were : pyrites was used. Arsenious Oxide found. Arsenious Oxide taken. Volatile ... ... . . . 0.00201 I I n 0.0186 gramme of pyrites 0.010676 Fixed ... ... ... 0.00917 I n 10 grammes of coal ... 0.000045 0.01118 --I 0*010721 The agreement between the amount of arsenious oxide found and that calculated may be considered satisfactory in the three experiments, and shows that the whole of the arsenic which may be present in the pyrites contained in ooal may be obtained or accounted for by the method described. That by far the greater quantity of the arsenic which may be present in fuel is not volatilized, but is retained by the ash, is confirmed by similar determinations made on a variety of fuels.Thus it was found that a North-Country gas coke yielded no volatile arsenic, but the ash contained arsenic to the extent of 0.28 grain to 1 pound of fuel. An oven coke, also made from a North-Country coal, yielded 0.25 grain of, fixed arsenic per pound of fuel, but no volatile arsenic. This would seem to show that the greater portion of the arsenic which may be found on malt has been deposited on it in the form of coal ash, and ought, therefore, to be removed from it by brushing and soreening. NOTE ADDED JULY 6, l903.-Since the printing of this communication, Mr. Wood Smith has drawn my attention to the fact that he, in conjunction with Mr. R. L. Jenks, has described a very similar process upwards of two years ago (Journ. SOC. Chem. I d , 1901, xx., 437). I regret that I had overlooked this prior communication, and I beg therefore to tender my apologies to the authors for omitting to make reference to it. Combustion of a fuel in oxygen, or, as preferred by Messrs. Wood Smith and Jenks, in air, can hardly, however, be regarded as novel. What I and my colleagues on the Committee::’ appointed by the Board of Inland Revenue were more immediately concerned with was the working out of the manipu- lative details of an operation based on this principle. * The Committee consisted of T. E. Thorpe, Esq., C.H., F.R.S., Principal of the Go\~ernnient Laboratory, as Chairman ; Professor William Angustus Tilden, D. Yc., F. R.8. ; Professor Harold Baily Dixon, M.A., F.R.S. ; Graham Aldous, Esq. ; John Pattinson, Esq., F.I.C. ; with Mr. T. J. Cheater, of the Government Laboratory, as Secretary.

ISSN:0003-2654    

DOI:10.1039/AN9032800344

出版商:RSC    

年代:1903

数据来源: RSC

摘要:

THE ANALYST. 349 THE ELECTROLYTIC ESTIMATION OF MINUTE QUANTITIES OF ARSENIC, MORE ESPECIALLY I N BREWING MATERIALS. BY T. E. THORPE, C.B., F.R.S. (Reprinted, by permission, from the Journal of the Chemical Society, August, 1903.) THE Royal Commission on Arsenical Poisoning, in their First Report, recommended that the Board of Inland Revenue should possess and should exercise powers to specify the ingredients of beer, and the materials used in their preparation which are liable to be contaminated by arsenic, and to prescribe tests by which their freedom from arsenic may be ascertained. With a view to the carrying into effect of the above recommendation, the Board of Inland Revenue, with the approval of the Treasury, decided to appoint a Committee to advise them as to the tests which might properly be prescribed for the several ingredients of beer which may be held to be liable to contamination.:: In their Report to the Board, the Committee state that of the various methods which have been suggested from time to time for the detection and estimation of the relatively small quantities of arsenic which may be present in beer and the ingredients of beer, or in the materials which may be used in their preparation, they are of opinion that those methods which depend on the conversion of the arsenic into hydrogen arsenide and the subsequent deposition of the arsenic in the elementary form by heating the gas are, on the whole, to be preferred.The hydrogen arsenide may be formed in practice by the action of so-called 4 4 nascent ” hydrogen on the arsenic present.The hydrogen may be evolved either electrolytically or through the agency of dilute hydfochloric acid on zinc admixed with, or containing, such an amount of copper or other suitable metal as to give rise to a sufficiently rapid evolution of the gas. t The amount of arsenic deposited by heating the hydrogen arsenide so formed is then determined by comparison with deposits obtained in precisely the same manner from wort, beer, malt extracts, sugar solutions, etc., containing known quantitiei3 of arsenic. An electrolytic method for detecting arsenic appears to have been first suggested by the late Professor Bloxam, of King’s College (Quart. Journ. Chem. SOC., 1861, xiii., 12, 338), but in its original form it had several disadvantages, which have prevented it from being generally adopted by chemists.Modifications of it have been made by Mr. Trotman, Mr. Bevan, and others. The process has been carefully investigated in the Government Laboratory, and in the form now described it is easy of application, and is capable of giving trustworthy results with a comparatively small expenditure of time and trouble. The apparatus employed in the electrolytic method consists of the following parts : 1. A glass vessel, A , provided with a ground-glass stopper and connections, 13, and a drying tube, C, containing calcium chloride. * See note on p. 348. t In the case of the electrolytic method, i t is neoesaary that the araenic should be in the condition of iiii srsenite or arsenious acid.350 THE ANALYST.2. A porous cell, D. 3. A glass vessel, E. 4. A cooling vessel, F. 5. A hard-glass constricted tube, G. 6. A small Bunsen burner, H. The glass vessel, A , forms with the porous vessel, D, the inner cell for the cathode, where the hydrogen and hydrogen arsenide are produced on passing the electric current. The vessel, A , is open at the bottom and fitted at the top with the ground-glass stopper, B, through which is passed to a point just below the neck of the vessel the stern of the tap-funnel. The glass stopper also carries the gas exit tube, on which is a bulb. The tube is bent as shown in the drawing, and is connected by means of a ground-glass joint with the drying tube, C. Through the glass cap is fused a stout platinum wire for making the connection on the outside of the current, and within the vessel with the electrode.The inner electrode, forming the cathode, is of sheet platinum and cone-shaped, with several perforations. I t is suspended from a hook made on the end of the wire passing through the glass stopper, and is adjusted so that when the stopper iR inserted in the vessel the lower edge of the electrode is 1 millimetre above the bottom of the vessel, A. It is then securely attached to the wire by closing the hook.:;: The porous vessel, D, is larger by 2 to 3 millimetres in diameter and in depth than the cylindrical portion of the glass vessel, A . As seen in the figure, A rests by means of its bulged-out shoulder upon the upper edge of D. The porous vessel is of unglazed, highly silicious ware, of the composition employed for the well-known, biscuit filters, first made by Dr.Pukal, and is from 1 to 1.5 millimetres in thickness.-! The cell for the anode consists of the stout glass vessel, E, upon the flat bottom, of which the porous vessel, D , containing the glass vessel, A , stands. The anode consists of a band of platinum 2 centimetres broad passing loosely round the porous cell, and connected with the current by means of a stout platinum wire. The liquid in the vessel, E, should be kept below 50°, and the vessel is therefore placed in a larger dish, F, containing cold water. The drying tube, C, is packed as follows : A plug of cotton-wool is first inserted, and then pure, granulated, anhydrous calcium chloride,: in pieces about the size of small shot or malt grains, for a length of 5 centimetres.Another loose plug of cotton-wool is placed upon the calcium chloride, followed by a roll of lead acetate paper. This is prepared by soaking filter-paper in a cold saturated solution of lead! * Care must be taken that the hook is effectually closed and the contact complete, otherwise there niay be danger of sparking, which might bring about an explosion if the apparatus contained a sufficient proportion of air. By continued use the surface of the cathode loses its polish, and the metal becomes coated with il grey powder, especially on the inside of the cone, In these circunistances the deposit which forms, especially from some saccharine liquids, may retain arsenic. Care should be taken, therefore, that t h e cathode is repolished from time to time.After this operation, it is advisable to immerse the cathode completely in the dilute acid and subject it to the action of the current for, say, half an hour. t The porous vessel may gradually become more or less stained, especially when used with caramels, black beers, and other highly-colourcd liquids. It is advisable, the:efore, from time to time to heat t h e vessel in a muffle fnrnace. Where a series of experiments is carried out with the same apparatus, the calcium chloride should bc renewed from time to tinie-say, after three or four experiments.THE ANALYST. 351 acetate, and then drying the paper in air. The paper is cut into strips about 1 centi- metre broad, and rolled into a, coil fitting loosely in the tube. A small spiral coil of lead acetate paper is also placed within the enlarged end of the exit tube to which the calcium chloride tube is attached. To the end of the drying tube there is fixed by means of a short piece of unvulcanized rubber tubing the hard-glaas constricted tube in which the arsenic is to be deposited.The ends of the drying tube and the hard-glass tube should beinclose contact beneath the rubber. To make one of these tubes, a piece of Jena glass tubing, having an external diameter of 5 millimetres and an internal diameter of 3.5 millimetres, is cleaned by successive treatment with acid, water, and alcohol, and dried. It is then held in the blow-pipe flame, so that a portion of the tube about 2 centimetres in length and 5 centimetres from the end of the tube is thoroughly FIG.1. softened, when the heated portion is drawn out to a length of 7 to 8 centimetres, and having at a distance of 1 centimetre from the shoulder of the tube an external diameter of 2 millimetres, a size which should be maintained as nearly as possible throughout the length of the constricted part. The tube is cut off near the end of the drawn-out portion, the last 1 centimetre of which is turned up at right angles. The hard-glass tube is supported in a horizontal position, when attached to the drying- tube of the apparatus, by resting in the slots on the upper edge of the cone which surrounds the flame of the small Bunsen burner. A piece of platinum gauze about 2 centimetres square is wrapped round the hard-glass tube at the point where it is to be heated by the Bunsen flame.The small Bunsen burner has a circular base 12 millimetres high, and its tube ie 6 centimetres in height and 5 millimetres in internal diameter. The upper portion of the tube is threaded and carries a gallery, upon which rests a copper cone. The upper edge of the cone contains two slots to receive the hard-glass tube. The apparatus, when employed in the manner to be described, has an apparent352 THE ANALYST. resistance of 1.4 ohms, the potential difference between the ends of the wires of the poles being 7 volts with a current of 5 ampAres. This strength of current gives about 40 C.C. of hydrogen in a minute, which furnishes a steady flame about 2 lvillimetres in height, and is the strength of current recommended to be used for the purposes of the test.To effect the reduction of the intensity of the main laboratory supply, which is the most convenient source of the current, rheostat of incandescent lamps may be employed. The lamps are arranged in parallel with each other, but in series with the apparatus, and, a2cording to the current desired, lamps of different candle power may be inserted. The apparatus may be arranged for the simultaneous execution of a number of tests. By suitable construction on the charging board the electric current passes through the solutions arranged in series, and any of these may be brought into or cut out of the circuit as desired. The current ie brought to the required strength--4.5 to 5 ampAres-by the introduction in the rheostat of lamps of the requisite power according to the number of tests to be carried out simultaneously.A diagram illustrating the method employed for this purpose is shown in Fig. 2 (p. 353). The sulphuric acid solution employed in the apparatus is prepared by mixing 1 volume of pure concentrated sulphuric acid with 7 volumes of water. It must, of course, be tested to ascertain its freedom from arsenic before it is used.* Certain of the solutions to be tested are very liable to froth when introduced into the apparatus. This inconvenience may be obviated by adding 1 or 2 C.C. of rectified amyl alcohol (boiling-point 128' to 132') to the acidified liquid undergoing electrolysis. Before describing the application of the test, it will be convenient to give in detail the methods to be followed in preparing the extracts or solutions of thevarious substances in such a form and in such an amount as to render them suitable for testing.1. h~ALT.-unground malt may readily be examined for arsenic by washing the malt with warm dilute acid and testing the acid extract, but this method is incon- venient in the case of a ground or crushed malt, as it is difficult to obtain a suitable extract. A ground malt is therefore incinerated in presence of lime and magnesia and the solution of the ash tested. Direct experiment has shown that deposits of arsenic obtained after treatment of an unground malt with dilute acid are equal in intensity to those obtained by the basic method of treatment of the same malt. The two methods are as follows : Basic Method for Ground MaEt.-Ten grammes of the ground malt are transferred to a porcelain, or preferably a platinum, dish about 3 inches in diameter, 30 C.C.of arsenic-free lime-water+ are added, and the dish heated over a small Bunsen flame for a few minutes. ,About 0.5 gramme of arsenic-free magnesia or lime is then added and thoroughly mixed with the contents of the dish, the heating of which is An ammeter is included in the circuit. * It is advisable to saturate the stock quantity of the dilute acid with the products of its electrolytic decomposition before use in the apparatus. This may bc conveniently eflected from electrodes of platinum wire iinmerscd in the liquid. The advantage of this procedure is that i t destroys any trace of dissolved sulpharous acid, and thereby obviates the formation of sulphuretted hydrogen during the actual testing.t The lirne-water, lime, magnesia, and potassium nieta1,isulphite arc tested as to their freedom from arsenic by the method described iuidrr " Chemicals " (pp. 981, 982).THE ANALYST. 353 continued until the organic matter is completely charred. The dish is then placed in a muffle furnace, or over a low Bunsen flame, and heated at a dull red heat until practically all the carbon is burnt off. When aold, the ash is moistened with water and 20 C.C. of the dilute sulphuric acid added. The dish is warmed and the contents transferred to a 4-ounce flask. About 8 gramme of potassium metabisulphite is added, FIG. 2.-DIAGRAM OF THE RHEOSTAT ASD CHARGING BOARD AHRASGED FOR FOUR 8IMULTBNEOVS TESTS. (THE ARROWS SHOW THE DIRECTIOX OF THE CUERENT.) a, a, a, a, Lamps by means of which the current is reduced to the required strength ; b, b, b, b, switches ; c, ammeter ; d, d, d, d, electrolytic cells, as in Fig, 1.and the solution boiled until free from sulphurous acid. After cooling, the solution is ready to be tested. Acid Nethod for Unground Malt.--Forty grammes of malt are transferred to a, wide-mouthed stoppered bottle. Forty C.C. of the dilute sulphuric acid and 60 C.C. of water are mixed together, raised to a temperature of 50°, and added to the malt. The bottle is shaken at intervals during twenty minutes and the liquid poured off; 25 c.c., representing 10 grammes of malt, are transferred to a small flask, 9 gramme354 THE ANALYST, of potassium metabisulphite added, and the solution boiled until free from sulphurous acid.2. MALT SUBSTITUTES (GLUCOSE, INVERT SUGAR, CARAMEL, Em.).-Five grammes we weighed in a small flask and dissolved in 20 C.C. of water. Half a gramme of potassium metabisulphite and 5 C.C. of the dilute sulphuric acid are then added, and the solution boiled until free from sulphurous acid. When cold, it is ready for adding to the electrolytic apparatus. 3. woRT.-Direct experiments have shown that when using the electrolytic apparatus it is unnecessary to destroy the organic matter of the wort. All the arsenic which may be present is evolved as hydrogen arsenide. For the test, 25 C.C. of the wort are placed in a small flask, & gramme of potassium metabisulphite and 5 C.C. of the dilute sulphuric acid are added, and the solution boiled until free from sulphurous acid.When cold, the solution is used for the test. 4. Hops AND H O P SUBSTITUTES.-Five grammes of the substance, ground if necessary in a mortar, are placed in a platinum dish, treated with lime and magnesia and incinerated, and the examination for arsenic carried out in the same manner as described in connection with ground malt. 5. BEER.-nirect experiments have shown that when the electrolytic apparatus is used it is unnecessary to destroy the organic matter of the beer. All the arsenic which may be present is evolved as hydrogen arsenide. Twenty-five C.C. of beer are placed in a small flask, + gramme of potassium metabisulphite and 5 C.C. of dilute sulphuric acid added, and the solution boiled until free from sulphurous acid.6. YEAST AND YEAST FooDs.-Five grammes are introduced into a flask and gently warmed with 20 C.C. of water. Half a gramme of potassium metabisulphite and 5 C.C. of dilute sulphuric acid are then added, and the contents of the flask boiled until free from sulphurous acid. Of liquid yeast foods, 25 C.C. are taken and the solution boiled, after the addition of potassium nietabisulphite and sulphuric acid, until free from sulphurous acid. 7. CHEMICALS : (a) SuZphites.-Of solid sulphites, 1 gramme is dissolved in 25 C.C. of vrater in a small flask. Five C.C. of dilute sulphuric acid are added, and the solution boiled until free from sulphurous acid. Of solutions of sulphites, 25 C.C. are taken and boiled in like manner after the addition of 5 C.C.of dilute sulphuric acid. The liquid is tested by the addition of a little more sulphuric acid to ascertain if the whole of the sulphite has been decomposed. ( b ) Acids-Sdphuric Acid.-Five C.C. are diluted with 20 C.C. of water, 8 gramme of potassium metabisulphite added, and the solution boiled to expel sulphurous acid. When cold, the solution is used for the test. Hydrochloric Acid.-Five C.C. are placed in a porcelain dish and diluted with about 5 C.C. of water. Five C.C. of pure nitric acid (specific gravity 1.4) and 2 C.C. of pure concentrated sulphuric acid are then added, the dish placed on a sand-bath, and the liquid evaporated until the sulphuric acid fumes. The dish ie removed, and, when cold, about 20 C.C. of water and 4 gramme of potassium metabisulphite added.When cold the solution is used for the test. The cold solution is used for the test. The cold solution is used for the test. The cold solution is used for the test.THE ANALYST. 365 The solution is transferred to a flask and heated until free from sulphurous mid and then tested, (c) Sulphur.-Ten grammes are taken, and the examination for arsenic carried out by burning the sulphur in a current of oxygen in the manner described in connection with the estimation of arsenic in.fue1 (Jozmz. Chm. SOC., lxxxiii., p. 969)." Owing to the readiness with which sulphur sublimes, the temperature to which the hard-glass tube is heated should be as low as possible, consistent with the burning of the sulphur, and the empty portion of the hard-glass tube next to the bent and drawn-out end should not be heated until the sulphur in the other part of the tube has been burnt.The liquid in the absorption tube is boiled to expel sulphurous acid, and any sulphur or other solid substance which may have passed into the absorption tube in the process of combustion is rendered soluble and in suitable condition for addition to the electrolytic apparatus by the method described for treating the ash of fuel. (d) Other ChmicaZs.-Of solids, 1 gramme is taken and dissolved in 25 C.C. of water. In either cam, if the solution is alkaline, it must be neutralized by the addition of dilute sulphuric acid. To the neutral liquid 4 gramme of potassium metabisulphite and 5 C.C. of dilute sulphuric acid are added, and the solution boiled until free from sulphuroue acid.The cold solution is used for the test. 8. FININas.-Five grammes are weighed out in a flask, 20 C.C. of water added, and gently warmed to effect solution. If sulphurous acid or a sulphite is present, 5 C.C. of the dilute sulphuric wid are added, and the solution boiled until free from sulphurous acid. If no sulphurous acid is present in the finings, 4 gramme of potassium meta- bisulphite is added to the solution prepared $8 above, together with 5 C.C. of the dilute sulphuric acid, and the solution boiled to expel sulphurous acid and then tested. MODE OF WORKING. The electrolytic apparatus, as already described, is arranged for the test, which is carried out in the following manner: The cells, electrodes, and glass v e s d , A , with the cap, funnel, and exit tube, are thoroughly cleaned and rinsed with distilled water.The porous vessel, D, containing the vessel, A , is placed in E, which is surrounded by cold water contained in the glass dish, F. The cdcium chloride tube, C, which has been packed in the manner described, is fitted on the ground-glass connection. The hard-glass tube, G, is attached by the indiarubber connection to the drying tube so that the bent portion at the end is in an upright position, and the platinum gauze is so arranged on the tube that it just overhangs the shoulder. The small Bunsen burner, H, is placed beneath the tube, which rests in the slots on the upper edge of the cone in such a position that when lighted the flame will heat about 2 centimetree of the tube just before the constriction commences.The connections with the battery-wires are made by means of binding screws in suofi a manner that the cumnt will pass from the vessel, E, to the cell, D ; 30 C.C. Of liquids, 25 C.C. are taken. * ANALYST, this nymber, page 344.356 THE ANALYST. of dilute sulphurio acid are then poured into E, containing. the anode, and 20 C.C. of diluteacid are also run into the cell, D, by means of the stoppered bottle, B, the stem of which must be left full of liquid. When all the conneotions are complete and the acid has been added, the current is switched on and the time noted. At the end of ten minutes the apparatus is practically free from air, and the issuing hydrogen may be lighted. At the same time the Bunsen burner is lighted and the flame carefully adjusted, so that the small piece of platinum gauze is maintained at a red heat throughout the experiment.The heating of the tube during the passing of the gas is continued for fifteen minutes, and if during that time no brown ring or deposit of arsenic has been formed in the constricted tube (best seen by holding a white card beneath the tube), the apparatus and the acid may be considered free from arsenic and suitable for the application of the test. Two C.C. of amyl alcohol are then run into the inner cell, D, by means of the tapfunnel, B. This is at once followed by the addition of the solution to be tested, prepared as described, 5 C.C. of water being used for rinsing out the oontaining vessel. No air must be admitted, and the stem of the funnel must be left full of liquid.If arsenic is present in the added liquid, a deposit begins to form in the narrow tube in the course of a few minutes at a point between 1 centimetre and 2 centimetres from the heated shoulder. At the end of thirty minutes the whole of the arsensic, except in very extreme cases, will have been deposited in the tube, which is now sealed up while full of hydrogen. This is effected in the following manner: The stopper of the funnel ie opened, and a small, pointed flame is at once directed against the narrow tube at a point 3 centimetres from the deposit, between the deposit and the turned-up end of the tube, which is meanwhile held by a pair of forceps. The electric current is at the same time disconnected, and then the tube is similarly heated and drawn off just below the shoulder.The deposit of arsenic must on no account be heated by the flame during the sealing of the tube. The short tube, about 4 centimetres long, containing the arsenic deposit may then be mounted on white card for reference. Of course, if the deposit of arsenic thus obtained should be so considerable as to prevent accurate comparison with the standard deposits, the experiment must be repeated upon a smaller quantity of the aubstance. Preparation of the Standard Deposits.-Although there is good reason to believe that the amount of arsenic deposited is in nowise affected by the nature of the spbstance with which the arsenic may be associated-0.01 milligramme of arsenic in beer, for example, giving a deposit of equal intensity with the same quantity of arsenic in malt-nevertheless, as the quantitative estimation is based on comparison, it is expedient to make use of deposits prepared by the addition of known amounts of arsenic to arsenic-free specimens of each class of substance. By so proceeding, all doubts which may arise from differences in manipulation or concerning the possible effect of differences in the nature and composition of the substances on the formation of the deposit are obviated.Thus, for example, in the case of hops and malt, although the final solution to be tested is substantially an acid solution of alkaline earths containing a minute quantity of arsenic, nevertheless, as the malt and hops behave somewhat differently on incineration, and themselves contain different amounts of The tube at once collapses and the end is drawn off.THE ANALYST.357 inorganic matter, it is advisable to make the standards by whioh malt and hops are to be compared directly from these substances. The preparation of a solution of arsenic of definite strength for this purpose must be carefully carried out. Pure resublimed arsenious oxide is ground to a fine powder in an agate mortar and dried at 100’. 0.1 gramme is accurately weighed on a watch-glass and transferred to a litre flask by washing it down a funnel placed in the neck of the 5ask with 1 or 2 C.C. of pure concentrated hydrochloric acid. The liquid must not be heated. When the solution is complete, it is diluted to 1 litre with distilled water and thoroughly mixed.Each C.C. of this solution (conveniently called A ) contains 0.0001 gramme, or 0.1 milligramme of arsenious oxide. Of this solution, 100 C.C. are carefully measured and transferred to another litre flask, and diluted with water to 1 litre. This solution (conveniently called B ) contains in each C.C. 0.00001 gramme (0.01 milligramme) of arsenious oxide. In certain of the experiments malt of this character was obtained by drying green malt by means of steam heat. In others a malt was used which had been dried in cylinders and out of contact with the fumes of fuel, The absence of arsenic in the reagents to be employed must also be ascertained by carrying out a control experiment with the malt, in all respects similar to the actual experiment, but without the addition of arsenic.Ten grammes of arsenic-free malt, previously ground in a mortar, are placed in a porcelain, or preferably a platinum, dish, and 0.2 C.C. of standard arsenic solution B, containing 0.002 milligramme of arsenious oxide, is added from a sufficiently narrow burette.* The whole is then treated in the manner described in connection with the examination of malt by the basic method. Similar deposits are obtained for 0.004, 0.006, 0.008, 0.010, 0.012, 0.014, 0.016, and 0.018 milligrammes respectively. Hops and Hop Substztutes.-A similar series of standards for hops and hop substitutes is prepared by taking 5 grammes of hops, previously ascertained to be free from arsenic, adding definite amounts of the standard arsenic solution, and carrying out the method of examination as described in connection with hops, Wort and Beer.-A series of standards’is prepared for each of these by adding to 25 C.C.of the measured liquid definite amounts of the standard arsenic solution B, the liquid being treated in the manner described in connection with the test for wort and beer. A series of standard deposits is also made for each of the following groups of substances : malt substitutes (glucose and invert sugar), yeast and yeast foods, and chemicals. Fuel.-With regard to the standards for fuel, it has been shown by direct experiments (vide (‘ The Estimation of Arsenic in Fuel,” Journ. Chem. SOC., vol. lxxxiii., p. 969)t that all the arsenic which may be present in fuel is obtained by the method described, partly in the hydrochloric acid distillate from the solution of the ash, and partly in the solution containing the arsenic volatilized during combustion ; and the amount of arsenic in fuel may be accurately estimated by a comparison of the Malt.-It is first necessary to obtain a malt free from arsenic.* The burette used in the experiments had an internal diameter of 7 millimetres, and 1 C.C. occupied f ANALYST, this number, page 344, a lcn th of ‘LO niillimetres.358 THE ANALYST. Standard Solution. As,?, arsenic deposits obtained by testing the fuel in the prescribed manner with the standards employed in the case of chemicals. The following table gives the amounts of arsenic represented by the various standard deposits converted into grains per pound, or per gallon, or per CW~., according to the nature and amount of the substance tested.In the case of malt the amount of arsenic in grains per pound is converted into its equivalent in grains per gallon of beer, on the assumption that a gallon of beer of the standard gravity 1.055 is produced from 2+ pounds of malt : Twenty-five Five Grammes Ten C.C. of Wort, Of Hops, sugar, One Gramnies of Ten Grammps of Malt. R~~~ or Caraniel, Yeast, Gramme of Fuel or Liquid. or other Chemicals. Sulphur. Substance. ARSENIC DEPOSITS ORTAIKED PROM Milli- gramme. 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 Grains per Pound. Equal to Grains per Gallon of Beer. Grains per Gallon. Grains per Pound. Grains per Pound. Grains per Cwt. 0.15 0.31 0-46 0.62 0.77 0.93 1.09 1-24 1.40 The advantages of the electrolytic method are : 1. That it obviates the use of zinc. 2. It is simple in execution, is under perfect control, and may be carried out under such conditions that the results obtained by different operators are strictly comparable, inasmuch as with a current strength of fair regularity the evolution of the gas is practically constant and uniform. 3. The whole of the solution to be tested for arsenii: may be added to the apparatus at once, so that during the whole time of testing the arsenic is under the influence of the '' nascent " hydrogen. 4. It has been established that such amounts of arsenic as are present in beer or its ingredients are evolved as hydrogen arsenide during the thirty minutes occupied by the test. The nature of the material associated with the arsenic is found to exercise no inhibiting effect on the formation and evolution of the hydrogen arsenide. Aqueous extracts of malts and worts may be added directly to the electrolytic apparatus without previous destruction of the organic matter as required by the zinc and acid process. 5. The deposits obtained are more uniform in character than those furnished byTHE ANALYST. 359 the zinc and acid method, and admit therefore of more accurate quantitative comparison. 6. The process allows of the simultaneous execution of a number of estimations of arseuic, depending on the arrangement of the rheostat. The disadvantages of the methods are : 1. The initial coet of the apparatus as compared with that employed in the zinc 2. That it can only be applied when an electric current of sufficient intensity is and acid method. available. I desire to acknowledge the great assistance I have Stubbs in working out the details of the method described received from Mr. George in this communication.

ISSN:0003-2654    

DOI:10.1039/AN9032800349

出版商:RSC    

年代:1903

数据来源: RSC

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THE ANALYST. 359 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. Mixed Glycerides in Lard and Beef and Mutton Fat. H. Hreis and A. Hafner. (Berkhte, 1903, xxxvi., 2766-2773.)-The crystals isolated by the authors from these fats by repeated crystallization from ether (Bey., 1903, xxxvi., 1123) were formerly judged to consist of a-palmitodistearin and j3-palmitodistearin, the latter being yielded by lard. On preparing pure synthetical P-palmitodistearin, however, by Guth's method (ANALYST, xxviii., 152), it was found to crystallize in microscopic needles melting at 52.2' C. (63" C. in the crystalline state), whereas the mixed glyceride from lard melted at 51.8" C. (and 66' C.) and crystallized in plates, showing that it was neither a- nor /I-palmitodistearin. The fatty acids separated from the glyceride of beef or mutton fat melted at 64" C., and those from the lard glyceride at 62" C.The proportion of stearic acid present was determined by Hehner and Mitohell's method, which the authors now strongly recommend for scientific investigations of this kind (cf. ANALYST, xxviii., 115), with the following results : Beef-fat crystals, 70.2 ; mutton-fat crystals, 71.1 ; and lard crystals, 69.0 per cent., whilst the synthetical P-palmitodistearin contained 70.5 per ceut. (theory, 69 per cent.). Hence the authors concluded that the lard crystals contained 2 molecules of stearic acid, and that the other constituent was an acid of the formula, C17H3402. For the separation of palmitic acid from stearic acid, the mixture of fatty acid8 was dissolved in 96 per cent.alcohol in sufficient quantity to keep palmitic acid in solution at 0" C. After standing at this temperature for twelve hours, the filtrate from the deposited stearic acid was treated with pn alcoholic solution of magnesium acetate in equivalent quantity to the stearic acid still present (0.12 gramme per 100 c.c.). The precipitate was filtered off after standing for twelve to fourteen hours360 THE ANALYST. at the ordinary temperature, and the fatty aoids liberated from the filtrate, rediesolved in just sifficient alcohol, and again treated with a third of the quantity of magnesium acetate solution, this process being continued until finally pure palmitic acid was obtained. I t was found that fatty acids from the beef and mutton fat crystals when thus treated yielded pure palmitic acid (melting-point, 62.3' C.), whereas the fatty acids from the lard crystals yielded an acid of the same formula (C17E3402), but melting at 55' to 56' C.I t is pointed out that Holde isolated a similar acid (melting-point, 54.5' to 57' C.) from olive oil, and concluded that it was daturio aoid. In conclusion, the authors describe a synthstical oleodistearin which they have prepared. This melted at 28" to 30" C., which is much lowar than the melting-point of the naturally ocourring oleodistsarin isolated by Heise and by Henriques and Kunne (ANALYST, xxiv., 185 ; xxviii., 40). C. A. M. Detection of Yeast Extract in Meat Extract. A. Searl. (Pharm. Journ., 1903, P. 516.)-Samples of extract recently purchased from high-class shops in London, and labelled Liebig's Extract of Meat (Extractum carnis Liebig), manu- factured by Liebig's process in South America from finest beef only," were found by the author to consist almost entirely, if not wholly, of yeast extract.For detecting this form of adulteration the following method is described, based upon the fact that with a modified Fehling's solution yeast extract gives a copious precipitate, whilst mest axtract yields none. The Fehling's solution is prepared by dissolving 200 grains of copper sulphate and 250 grains of neutral sodium tartrate in 4 ounces of water, and adding to this a solution of 250 grains of sodium hydroxide in 4 ounces of water. Ten grains of the sample &re then dissolved in 1.5 ounces of water, 0.75 ounce of the above Rolution is added, and the mixture is boiled for a minute or two. The precipitate obtained, should the sample consist of yeast extract, is of a bulky, curdled nature, bluish-white in colour, and is allnoct insoluble in water.Several samples of yeast extract have been found to give, for each 10 grains of extract, taken, about 1 grain of this precipitate when washed, dried, and weighed. The author (zbid., p. 704) describes the following modification by means of which admixtures of as little as 1 per cent, of yeast extract may be detected in meat extract : The sample having given doubtful or negative results by the foregoing method, 50 to 100 grains of it a>re dissolved in 1 or 2 drachms of water (according to quantity taken), and alcohol added in quantity sufficient to throw down all matter insoluble in that menstruum, vigorously shaken, the insoluble residue filtered off and dissolved in 1+ ounces of water, and treated as above with the modified Fehling's solution.If yeast extract be present, the characteristic bluish-white precipitate will be thrown down, which may be collected and weighed. w. P. s. Preservatives in Yolk of Egg. A. Juckenack. (Z&t. fur Untewuch. der Nahr: und Genussmittel, 1903, vi., 830.)-Preserved powdered yolk of egg being now fre- quently employed in pastry-making, the author has examined samples of the same,THE ANALYST. 361 and finds that the powder often contains as much as 2 per cent. of boric acid, besides a quantity of formalin in addition.He considers that the use of such egg-powder should not be permitted. w. P. s. Further Application of the Sublimation Test. L. Frank. ( z e d . jiir Untersuch. der Nahr. und Genussmittel, 1903, vi., 880-882.)-Nestler’s sublimation test (see ANALYST, 1902, 153) has been employed by the author for the examination of other substances besides tea, such as coffee, Paraguay tea, kola nuts, cocoa, tobacco, etc., and drawings are given of the characteristic crystals obtained in each case. Caffeine crystals were obtained from coffee husks, showing that the alkaloid is present in the latter as well as in the berry. w. P. s. Physiological Action of Large Doses of Saponia W. Lohmann. (Zeit. fiir Gfentl. Chm., 1903, ix., 320-324.) - Daily doses of saponin, beginning with 0.5 gramme and increasing by 0-5 gramme up to 7 grammes, had no injurious effects on the health of a rabbit beyond a hardening of the excreta.A post-mortem examination showed that the internal organs were not affected. The doses were given mixed with the food. The author then himself took quantities of saponin, starting with 0.1 gramme and finishing on the tenth day with 1 gramme. No ill- effects were observed. w. P. s. Some Colour Reactions of Morphine and Codeine. E. Gabutti. (BoZZ. chim. farm., 1903, xlii., 481 ; through Chem. Zeit. Rep., l903,268.)-The substance is gently warmed in a porcelain basin with a little strong sulphuric acid till a faint pink colour develops. If a small quantity of chloral or bromal is stirred in, and the whole is kept warm, morphine gives a violet, codeine a brilliant blue-green colour. The warming is indispensable.I?. H. L. Colour Reactions of Yohimbine. G. Meillere. (Journ. Pharm. Chim., 1903, xviii., 385.)-If a small crystal of the alkaloid is dissolved in dilute sulphuric acid (1 : l), and the solution heated in a porcelain crucible on the water-bath with a trace of saccharose, dextrose, or furfurol, a wine-red colour is produced, a n d , the liquid, when examined spectroscopically, shows large absorption band in the blue part of the spectrum, extending from 120 to 135 in Salet’s spectroscope graduated for z> = 100. Another colour reaction, which yohimbine shares with other alkaloids, is produced by heating it on the water-bath with an excess of nitric acid. On evaporating the liquid to dryness a bright-yellow residue remains, which becomes brown on treatment with ammonia.C. A . M. Determination of Cinnamic Aldehyde. J. Hanus. (Zed. fiir Unterszbch. der N a h . und Genussmittel, 1903, vi., 817-827.)-The method described depends upon the condensation of cinnamio aldehyde by semioxamazide, the latter being obtained362 THE ANALYST. by the action of hydrazine hydroxide on oxamethane. About 0.2 gramme of cinnamon oil is thoroughly diffused, by shaking, in 100 C.C. of water. 0.35 gramme of semi- oxamazide dissolved in 15 C.C. of hot water is then added, with constant stirring, and the mixture allowed to stand for twenty-four hours. During the first three hours it should be frequently agitated. The precipitate is now collected on a filter, washed with cold water, dried at 105' C.for five hours, and weighed. The weight obtained multiplied by 0.6083 gives the amount of cinnsmic aldehyde in grammes. To determine the amount of aldehyde in powdered cinnamon, about 8 grammes of the latter are distilled in a current of steam, 400 C.C. of distillate being collected. The distillate is extracted several times with ether, and the united ethereal solutions evaporated at a temperature below 70" C. The residue of oil obtained is then treated as above described. Various samples of cinnamon yielded from 1.96 to 2.04 per cent. of cinnsmic aldehyde when examined by this method. w. P. s. Determination of Eugenol. H. Thorns. (Pharm. Xeit., 1903, 781 ; through Chemist and Druggist, 1903, 581.)-When the author's original method was devised, the only constituents oE oil of cloves recognised with certainty were eugenol and caryophyllene.Later discoveries having rendered a modification of the process necessary, the following revised method is given. Five grammes of oil of cloves are heated on a water-bath for thirty minutes with 20 C.C. of 15 per cent. sodium hydroxide solution. After complete separation of the hydrocarbons, the alkaline solution of the eugenol is separated, and the caryophyllene washed twice with sodium hydroxide solution, the washings being added to the eugenol solution. The latter is now treated with 6 grammes of benzoyl chloride, and the reaction completed on the water-bath. When cold, the crystalline mass is collected on a filter, and then washed into a beaker with 50 C.C.of water. I t is melted, well agitated, and again allowed to cool. This washing is repeated twice. The mass is then dissolved in 25 C.C. of warm alcohol (90 per cent.) and allowed to cool. The benzoyl eugenol when cooled to 17' C. crystallizes out in fine needles, and is collected on a tared filter. After washing with about 5 C.C. of alcohol, the filter and its contents are dried at 101" C. and weighed. The allowance for the solubility of benzoyl eugenol in the 25 C.C. of alcohol is 0.55 gramme, and this must be added to the weight obtained. The total eugenol in the oil of cloves, both free and combined, is then found from the formula P = 4,100 (a + 0.55) where P = percentage of eugenol, a = the weight of benzoyl eugenol actually found, and b = the weight of oil of cloves taken. -- 67 b (See also this volume, p. 217.) w. P. s. Oil of Rosemary. G. R. Pancoast and W. Graham. (dmer. Journ. Phrm., 1903, lxxv., 453, 454.)-The Dalmatian oil should have a specifio gravity of 0.900 to 0.920 at 15" C., and an optical rotation of + l o to +4", whil'st the corresponding figures of the French oil should be 0.900 to 0.915 and +lo to +11' raspeotively.THE ANALYBT. 363 Both oils should dissolve in an equal volume of 90per cant. alcohol and in 10 parts of 80 per cent. alcohol. Four samples of Dalmatian oil submitted to the authors varied in specific gravity from 0.895 to 0.904 at 15" C., and from +l0.36 to +1l0*37' in optical rotation. Of the eleven samples of commercial French oil examined, the extreme figures were : Specific gravity, 0.884 and 0.904 ; optical rotation, + O O . 3 0 and 1S3*30' ; aDd percentage of bornyl acetate, 3.0 and 8.3. One of the samples would not dissolve in less than 5 parts of 95 per cent. alcohol, and another in less than 3 parts, whilst five samples would not dissolve in 10 parts of 80 per cent. alcohol. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9032800359

出版商:RSC    

年代:1903

数据来源: RSC

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THE ANALYBT. 363 ORGANIC ANALYSIS. The Determination of Pyridine in Aqueous Solution. M. Franyois. (Jozmz. Pharm. Chim,, 1903, xviii., 337, 338.)-The method described is based on the precipitation of the pyridine as the aurichloride (C,H,N.HCl. AuCl,), and weighing the gold left on igniting the precipitate. The solution, containing about 0.1 gramme of pyridine or its hydrochloride, is treated with 20 to 30 drops of hydro- chloric acid, and then with excess of a solution of pure auric chloride, the solution evaporated to dryness, and the residue cooled in a desiccator. I t is then washed with ether (free from aldehyde), and dissolved in boiling water in a weighed dish, the solution evaporated to dryness, and the residue ignited. 196.6 parts of gold correspond with 79 parts of pyridine.C. A. M. Estimation of Formaldehyde in Solution. G. Lemme. (Chem. Zeit., 1903, xxvii., 896.)-The compound which formaldehyde forms with sodium bisulphite is SO stable that it is produced immediately when formaldehyde is mixed with a solution of the normal sulphite, an equivalent quantity of sodium hydroxide being set free, according to the equation : HCOH + Na2S0, + H20 = H,C.OH.NaSO, + NaOH. I n order to estimate formaldehyde in this way, a solution containing 250 grammes of crystalline normal sodium sulphite in 750 C.C. of water is prepared. One hundred C.C. of the reagent are taken, and, since the salt is alkaline to phenolphthalein, a bisulphite solution is dropped in till the liquid is neutral to that indicator. Five C.C. of the formaldehyde solution are next added, and the amount of sodium hydroxide set free is titrated with normal sulphuric acid.The colour change is not quite sharp, and readings may vary some 0.1 or 0.2 C.C. ; but in view of the fact that, if the formalin is of 40 per cent. strength, about 70 C.C. of alkali will be required, this does not appreciably affect the accuracy of the process. Since a solution of sodium sulphite is permanent, this method of estimating formaldehyde is very easy to carry out. F. H. L. Iodometric Estimation of Benzidine and Tolidine. A. Roesler and B. Glas- mann. (Chem. Zeit., 1903, xxvii., 986.)-This process depends on the fact that 1 molecule of benzidine or tolidine reacts with 2 atoms of iodine to form 1 molecule364 THE ANALYST. of hydriodic acid and 1 molecule of the mono-iodine derivative of the base taken.These compounds are decomposed by acids, iodine being liberated, therefore the titration must be conducted in perfectly neutral liquids. About 5 grammes of the base are dissolved in warm water with the aid of 5 C.C. of 1.19 hydrochloric acid. When cold, the solution is diluted to 500 c.o., 25 C.C. of it are brought into a 1-litre beaker, and sodium bicarbonate solution is added to incipient precipitation. The precipitate is next taken up in a few drops of very weak hydrochloric acid, the liquid diluted to 500 c.c., and TG iodine is dropped in from a burette with constant agitation, the end-point of the reaction being ascertained either by the uso of starch paper, or by a drop of fresh starch solution on an opal plate.The precipitated iodine derivative of both bases is dark blue, but with a little practice it is easy to tell the end of the titration. The process is simple, and the results quoted are satisfactory. F. H. L. Some Colour Reactions of Sesame Oil. Sesamol a Constituent of Seeam6 Oil. H. Kreis. (Chem. Zed., 1903, xxVii., 1030.)-When 5 C.C. of sesame oil is shaken with an equal volume of an aqueous emulsion-of diazonaphthionic acid about 0.1 per cent. in strength, and sodium hydroxide is added in excess, some samples yield a green azo dyestuff, but the majority give no colour or a faint pink. Those samples that yield the green also give an intense emerald green colour when shaken with 1.4 nitric acid, but the samples that do not give the green strike an orange-red colour with nitric acid.In the original communication the author describes the attempts he has made to isolate the body which produces this green dyestuff; but although he has not succeeded in obtaining a sufficient quantity for the purpose of identification, it is clearly a phenolic substance, to which the name ‘‘ sesamol ” may be given. Sesamol is a normal and constant ingredient of sesame oil ; in the green-giving oils it exists in the free state, in the others it is present in a state of combination (possibly a glucoaide, though sugar has not yet been found), which prevents it from being diazotized. All samples of sesami! oil give the green diazo dyestuff, and are therefore shown to contain sesamol, if they are boiled for a short time with 10 per cent.hydrochloric acid, or shaken in the cold with 1-19 acid ; and after this treatment all samples strike a green only with nitric acid I t is conceivable, though proof is wanting, that the green-giving oils are such have been through some acid treatment during their preparation. Those insolated oils which give the Bishop-Kreis reaction (ANALYST, 1902, xxvii., 363) develop the same colour when shaken with HCl and an ethereal solution of sesamol. It is, therefore, the sesamol that is the cause of the Bishop and of the Bishop Kreis reactions. I t is probably SISO the cause of the Behrena test, and of the green with nitric acid. After addition of a little sesamol, a red-giving sesame oil yields a strong green with nitric acid. The best method yet discovered of extracting the sesamol is to shake the oil five or six times for fifteen minutes with an equal volume of alcohol.The spirit is distilled from the extract, and the residue is shaken with water; this dissolves the phenol and leaves the fatty acids. The aqueous liquid is filtered, and finally extracted withTHE ANALYST. 365 ether. The aqueous solution of the residue does not give a perceptible precipitate with bromine water, but yields a dark violet colour (soluble in ether) with ferric chloride. I t yields a dyestuff immediately on treatment with diazonaphthionic acid and alkali, which is soluble with a violet colour in strong sulphuric acid, dyes wool scarlet in an acid bath, and in aqueous solution is coloured yellowish by dilute acids, becoming bluish on addition of alkali.The author gives the following new colour reaction : Five C.C. of the sample are shaken in a tube with an equal volume of 75 per cent. sulphuric acid and 0.3 C.C. of 2 or 3 per cent. hydrogen peroxide. I n a short time a strong olive-green colour develops, and on dilution with water the acid becomes pale yellow with a green fluorescence. Olive, cotton, arachis, poppy, almond, peach-kernel, linseed, and castor oils do not give any noteworthy colours with the reagent; but the test will show 5 per cent. of sesame oil in a mixture containing it. In certain respects the reaction resembles Bellier's test with vanadic and sulphuric acids. [Kreis makes no mention of the substances, including " sesamin," isolated from sesame oil, by Villavecchia and Fabris (A?rn.del Lab. Chim. centr. delle Gabelle, iii., 13; Jounz. Chem. SOC., Abstract, 1898, lxxiv., [i.], 445).] F. H. L. Salmon Oil. B. de Greiff. (Chem. l i e u . , 1903, x., 223 ; through Clzern. Zed. Rep., 1903, 257.)-This oil, which is produced in considerable quantities in British Columbia, is a pale golden-yellow liquid, with a mild, fish-like odour and a com- paratively agreeable taste. Its constants are as follows: Specific gravity at 15.5°/15.50 C., 0.92586 ; saponification number, 182.8 ; Reichert-Meissl number, 0.55 ; Hehner number, 95.02 ; iodine value, 161.42 ; iodine value of the liquid acids, 197.4 ; unsaponifiable matter, 4.4 per cent. ; and acid number, 4.98. F. H. L. (Note.-The acid number given appears somewhat high.- W. C.) Some Properties of Nerol.H. von Soden and W. Treff. (Chem. Z e k , 1903, xxvii., 897.)-When nerol is thoroughly freed from geraniol it forms a colourless oil, and possesses a still more agreeable rose-like odour than the product usually obtained from the oils of neroli or petitgrain. I n the pure state, its specific gravity at 15' C. is 0.8813. Under a pressure of 755 m.m. it boils at 226" to 227' C. ; at the reduced pressure of 25 m.m. its boiling-point is 125O C. I t s formula is C,,H,,O, and it unites with exactly 4 atoms of bromine. The diphenyl- urethane of pure nerol crystallizes from alcohol in colourless glittering needles which melt at 52' to 53" C. Hesse and Zeitschel have given 73" to 75" C. as the melting-point of the diphenylurethane prepared from a nerol contaminated with geraniol; but this higher figure is simply due to the presence of geranyl diphenyl- urethane, which melts at 82" C.I t is optically inactive. F. H. L. The Determination of Ammonia in Urine. C. Demon. (JozLrn. Pharm. Chim., 1903, xviii., 289-293.)-Ten C.C. of the urine are mixed with 2 grammes of recently, calcined magnesia and 440 C.C. of water, and distilled for exactly forty-five minutes,366 THE ANALYST. the distillate being collected in standard acid, which is titrated in the usual way. The liquid in the flask is then diluted to the original volume and again distilled for exactly forty-five minutes, and the new distillate collected and titrated. I t has been shown by Berthelot and Andrd that the amount of decomposition of urea on boiling with magnesia and water is proportional to the time.Hence the difference between the amount of ammonia found in the first distillation and that obtained in the second distillation gives that yielded by the ammonium salts originally present in the urine. Various samples of fresh urine examined by the author were found to contain from 51 to 790 milligrammes of ammonia per litre, whilst after standing for twenty- four hours the amounts had risen to 119 to 816 milligrammes. By adding 5 per cent. of sodium fluoride to the freeh urine, the amounts of ammonia obtained after twenty- four hours were, as a rule, identical with those first obtained. C. A. M. Determination of Ammonia in Urine, Blood, Etc. A. Schittenhelm. (Zeits. physiol. Chem., 1903, xxxix., 73 ; through Chem. Zeit. Rep,, 1903, 251.) -The author finds the Kruger-Reich method for the determination of ammonia by distillation under diminished pressure with milk of lime and alcohol very accurate and well suited by reason of its simplicity for clinical purposes.He describes it at length, but he remarks that in such cases as the examination of faecal matter the nitro- genous substances are partially decomposed by the caustic alkali, so that it is better to adopt Folin's proposal of adding common salt and making the liquid alkaline with sodium carbonate. So modified, the method is suitable for the analysis of any of the organic materials mentioned, and is carried out as follows: The apparatus consists of a distilling flask carrying a tube closed by means of a clamp, and connected with a Peligot tube to serve as receiver.The exit of the latter com- municates with the pump through a tube, on which also a clamp is placed. Twenty-five to 50 grammes of the substance, rubbed down, if solid, with 0.5 per cent. hydrochloric acid, and made up to a certain volume, are brought into the flask, mixed with about 10 grammes of sodium chloride, and sodium carbonate added until the reaction is distinctly alkaline (usually about 1 gramme) ; 10 to 30 C.C. of decinormal hydro- chloric acid tinted with a few drops of rosolic acid are put into the Peligot tube, which is stood in ice. The pump is then set in action till the highest possible vacuum is obtained. About 20 C.C. of 96 per cent. alcohol, free from acid, are introduced into the flask, and the water-bath underneath is raised to a temperature of 43" C.(not higher). Every ten minutes 15 to 20 C.C. of fresh alcohol are run in, or 10 to 15 C.C. of water if evaporation is proceeding too rapidly. Finally, 10 C.C. of alcohol are introduced to drive over any water drops in the leading tube, the clamp leading to the pump is closed, that on the inlet is cautiously opened, and air is allowed to enter gently. The liquid in the receiver is then titrated with decinormal alkali, the rosolic acid it already contains serving as indicator. In the case of urine, the distillation will be complete in seventeen minutes after the liquid has entered into brisk ebullition, F. H. L.THE ANALYST. 367 Filtration of Liquids which will not Clarify by Subsidence. H. Holldack. (Chem.Zeit., 1903, xxvii., 1034.)-In carrying out such processes as the determination of crude woody fibre in feeding-stuffs by treatment with 1-25 per cent. snlphuric acid, a liquid is obtained in which the precipitate will not settle, so that it cannot be washed by decantation. I t is customary, therefore, to free it from acid by filtration, immersing an inverted funnel in the liquid, connecting the stem to an aspirator, and using a piece of cloth tied over the mouth of the funnel as a filter. The cloth, how- ever, quickly becomes blocked by the finer particles, especially if it is suspended only just below’the level of the liquid, Holldack finds it very much better to push the covered funnel right down till it rests on the bottom of the vessel, when much of the precipitate is caught on the conical sides of the funnel, and the cloth remains porous longer. I n fact, the acid liquid may be drawn off in a few minutes, so that the whole analysis, which usually occupies at least two days, according to Konig, may be finished in half a day. F. H. L. Use of Berthelot’s Bomb for the Detection of Arsenic in Animal Matter. G. Bertrand. (Ann. de I’Inst. Pasteur, 1903, xvii., 581 ; through Chem. Zed. Rep., 1903, 267.)--The author recommends that organic materials in which arsenic is to be sought should be destroyed by explosion in the Berthelot bomb rather than by treat- ment with acids. The sample should be put into a shallow platinum basin-say 40 millimetres in diameter by 5 millimetres deep. The gun-cotton must be prepared with acids perfectly free from arsenic, and for a, like reason the igniting wire must be platinum, not iron. After cooling, the contents of the bomb are evaporated on the water-bath, the nitric acid driven off with sulphuric acid, the residue diluted with water, and the whole introduced into the Marsh apparatus. Tests made by this method fully confirm the previous statements of the author. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9032800363

出版商:RSC    

年代:1903

数据来源: RSC

摘要:

THE ANALYST. 367 INORGANIC ANALYSIS. A New Method of Detecting and Determining Traces of Arsenic. A. Gautier. (Bull. SOC. Chim., 1903, xxix., 859-868.)-This method is based on the fact that on precipitating iron in the ferric state every trace of arsenic in the solution is simultaneously carried down. Thus the author found that 0.001 milligramme of arsenic, added to a litre of water in form of arsenites or arsenates, was completely removed in this way, and could be subsequently determined by treating the pre- cipitate in Marsh's apparatus in the usual way. The iron reagent used for the precipitation was prepared by dissolving 100 grammes of ferrous sulphate in 500 C.C. of water containing 25 C.C. of pure sulphuric acid, and treating the solution with hydrogen eulphide. The liquid was boiled and filtered, and the ferrous salt oxidized by mertnsof 28 grammes of pure nitric acid.The iron was then precipitated as ferric hydroxide by means of pure ammonium hydroxide, and the precipitate washed and dissolved in cold dilute sulphuric acid. The last traces of arsenic (0.002 to 0.003 milligramme per 3 C.C. of Fe,O,) were removed from this solution of ferric sulphate by digesting the liquid for two days with granulated zinc and boiling it in vuczw,368 THE ANALYST. The solution was subsequently reoxidized with nitric and sulphuric acids, and the ferric hydroxide reprecipitated with ammonium hydroxide, washed, and dissolved in cold sulphuric acid in the proportion of 30 grammes of oxide in 100 C.C. of acid Five C.C. of this reagent were found to be capable of precipitating the arsenic in 300 to 400 C.C.of water, whilst itself containing only 0.0000025 milligramme. I n test experiments, 0.002 milligramme of arsenic in the form of sodium arsenate was added to 2 litres of water, and the amount found was identical with that taken ; whilst as regards the sensibility of the method, the author states that he was able in this way to determine 0.001 milligramme of arsenic added to a litre of water. For the detection of arsenic in forensic cases, the organic matter is destroyed by treatment with a mixture of nitric and sulphuric acids, and the charred mass treated with boiling water. The filtrate is cooled, partially neutralized, and treated with the ferric salt until an excess is shown on testing with ferrocyanide. The precipitate formed under these conditions does not remove the arsenic. The liquid is again filtered, and the filtrate treated with 5 C.C.of the ferric reagent, and heated to the boiling-point, neutralized with ammonium hydroxide, and filtered. The precipitate is dissolved in a mixture of nitric and sulphuric acids, and the solution heated so long as nitrqus fumes appear, after which it is diluted and trans- ferred to Marsh’s apparatus. In sea-water from the coast of Brittany the author found 0.010 milligramme of arsenic per litre, whilst in water from the Atlantic, near the Azores, he obtained the following amounts at different depths : 10 metres, 0.025 milligramme 1,335 metres, 0.010 milligramme ; and 5,943 metres, 0.080 milligramme per litre.The greater amount at the lower depths is attributed to volcanic origin. Mineral waters all contain more or less arsenic, which can be accurately deter- mined by the new method. For example, the saline water of Misserey .yielded 0.010 milligramme per litre. Various samples of sea-salt of different origin also con- tained perceptible traces, ranging from 0.001 to 0.045 milligramme per 100 grammes, whilst sodium chloride collected from a recent fissure in Vesuvius contained 0.175 milligramme per 100 grammes. Water distilled with sodium carbonate in a copper vessel contained 0.0007 milli- gramme of arsenic per litre, and slightly more when a glass flask was used for the distillation. Similar traces were also found in all the ordinary laboratory reagents , and especially in hydrogen sulphide, which frequently contained an appreciable amount, even after being thoroughly washed.The following method was found to effect COM- plete purification: The gas, after being washed with water, was passed through a column of moist pumice 30 centimetres in length, then through a combustion-tube filled with fragments of glass (25 centimetres) brought to a red heat, then through serpentine absorption-tubes containing a concentrated solution of barium sulphide, which retained further traces of arsenical compounds, and finally through a tube filled with cotton-wool. Hydrogen sulphide thus treated yielded only 0-0008 milligramme of arsenic when passed for two hours into boiling nitric acid, whilst not the slightest trace was found when the gas wag passed into 300 to 400 C.C. of acidulated water.C. A. M.THE ANALYST. 369 Analysis of Lead Glance. E. Murmann. (Oesterr. Chem. Zed., 1903, vi., 433,)-It is usually assumed that when lead glance is opened up with nitric and tartaric acids and water, the silver remains in solution as nitrate. This, however, is incorrect, for all glances contain more or less chlorine ; and so, when treated in the manner indicated, a certain proportion of, or all, the silver remains in the residue, from which it can be readily dissolved out by ammonia. The author's method of determining silver is &a follows : 20 grammes (or a quantity suited to the amount of eilver expected) of the finely-powdered sample are passed through a very fine sieve, then heated on the water-bath with about 150 C.C.of a mixture of 4 volumes of strong hydrochloric acid and 1 volume of water until the reaction is complete. A small quantity 'of nitric acid (about 3 c.c.) is added, and when the decomposition is completed and the residue of gangue and lead chloride ie white, a, little water is introduced to lessen the solubility of tho lead chloride. The mixture is allowed to become quite cold, the bulk of the lead chloride is collected on a paper carried on a perforated plate in a porcelain funnel and washed with dilute hydrochloric acid ; the filtrate is evaporated to dryness in porcelain, the residue converted into nitrate, dissolved in water acidulated with nitric acid, and filtered. The insoluble portion is washed with dilute nitric acid, then digested with ammonia ; the ammoniacal filtrate is warmed till most of the ammonia is driven off, and the silver chloride is finally precipitated with a few drops of nitric acid.So obtained, the silver chloride will a t the worst be contaminated with minute traces of silica only. The method is based on the slight solubility of silver chloride in strong or m'oderately dilute hydro- chloric acid ; consequently, as had been found by preliminary experiments, the small amounts of silver met with in glance are readily soluble in acid of the strength employed in the process. To determine the lead, about 1 gramme of the sample should be boiled with about 40 C.C. of strong hydrochloric acid in a flask fitted with a reflux condenser. A few drops of nitric acid are then added, and after a, short time the mixture is filtered, the lead being finally determined in the usual way.The finest possible sub- division of the glance (to an impalpable powder) is essential in both processes. F. H. L. A New Method of Decomposing Galena and Chalcopyrites. C. Boucher. (Bzdl. SOC. Chzrn., 1903, xxix., 933-936.)-By boiling the finely-divided mineral with a concentrated solution of ammoniuffi persulphate, the lead sulphide in galena is gradually converted into sulphate, but in order to obtain a rapid reaction a few drops of concentrated nitric acid should be added. I n the case of chalcopyrites, it is necessary to boil the liquid on a sand-bath nearly to dryness in order to melt the separated sulphur, which might enclose other substances. Excellent results can also be obtained by fueing the powdered sample with four or five times its quantity of a mixture of 3 parts of sodium persulphate with 1 part of ammonium nitrate.The use of persulphates alone is insufficient. If the mineral contains muoh manganese, the latter will be found in the residue in the form of manganese dioxide. Other minerals containing sulphur-e.g., pyrites, blende, stibnite, mispickel, etc.-do not give good results when treated by this method, as they offer much greater resistance to the action of persulphates. C. A. M.370 THE ANALYST. Notes on the Sampling of Antimonial Lead. H. Nissenson and P. Siedler. (Berg. u. Huttenmann. Zeit., 1903, lxii., 421; through Chem. Zeit. Rep., 1903, 267.)-The authors have found the antimony to be very unevenly distributed throughout an ingot of hard lead.With a mean of 19.98 per cent., the figures for the antimony have ranged from 13.08 to 21-64 per cent. When an ingot containing between 18 and 22 per cent. of Sb is broken, the upper part of the block always exhibits a silvery-white portion of small crystals, which is surrounded by a zone of coarser crystals, and this by a narrow band of dark gray amorphous matter. Under- neath lie several cavities, and beneath them another amorphous layer. The amorphous material is the pure alloy of lead and antimony; the copper a d other impurities are in the crystals. The best way to take a sample of such hard lead is to make a diagonal saw cut through the block. The powder is mixed up and reduced in size. The coarser part, which contains an excess of lead, and the finer part, which has an excess of antimony, are analysed separately, and the results are adjusted for the bulk. The authors refer to work done by Steed in a similar direction.F. H. L. The Colorimetric Determination of Bismuth. P. Planas. (Journ. Pharm. Chim., 1903, xviii., 385-389.)-The method is based upon the fact that on adding potassium iodide to an acid solution of a bismuth salt containing its own volume of glycerin or vice versd the bismuth iodide formed remains in solution, producing a yellow coloration, the intensity of which is proportional to the excess of potassium iodide added to a bismuth solution, or to the excess of bismuth solution added to a. potassium iodide solution. A standard bismuth solution is prepared by dissolving 1 gramme of pure bismuth in a mixture of 3 C.C.of nitric acid (Codex) and 2.8 C.C. of water, and diluting the solution to 100 C.C. with glycerin (30”). The reagent used contains 5 grammes of pure potassium iodide in 5 C.C. of water, made up to 100 C.C. with glycerin of the same strength. In determining the amount of bismuth in, e.g., bismuth subnitrate, a weighed quantity of the sample (e.g., 0.15 grainme) is dissolved in dilute nitric acid, and, after the addition of 10 C.C. of glycerin and 10 C.C. of the potassium iodide solution, is diluted to 50 C.C. with a mixture of equal parts of water and glycerin (30O). The colour produced is then matched with that given by 10 c.c, of the standard solution of bismuth under the same conditions. The method is stated to be applicable to the determination of bismuth in all inorganic or organic compounds, and can be used inversely for the determination of potassium iodide.C. A. M. Determination of Zinc. 0. Herting. (Chem. Zeit., 1903, xxvii., 986.)--The author finds that Murmann’s plan (ANALYST, 1899, xxiv., 51) of adding mercuric chloride to a zinc solution before precipitating it as sulphide renders the method very exact and rapid in execution. Filtration may be undertaken immediately the precipitate has settled, which is in five or ten minutes’ time. Herting alwap employs either Schleicher and Schull’s paper, No. 589, or Dreverhoff’s, No. 417. It is not necessary to use the ourrent of hydrogen, .for precipitated zinc sulphide is readilyTHE ANALYST. 37 1 converted on ignition into oxide.The method of determining zinc by precipitating it as.basic carbonate and weighing as oxide is one of the most accurate analytical operations known, provided the proper precautions are observed, but unfortunately it is not always available. Volumetric processes have been improved of late years, but they cannot be recommended, and, in view of the excellence of Murmann's method, are not so much required. For all technical purposes, zinc may be completely separated from iron by throwing the latter down twice with ammonia. The separation becomes very exact, even when the proportion of iron is high, if a little ammonium acetate is present in the liquid each time. F. H. L. Colorimetric Estimation of Manganese in Steel. J. Malette. (La Rdvue technique, 1903, xxiv., 327 ; through Chem.Zeit. Rep., 1903, 267.)-This process depenqs on the oxidation of the manganese by means of PbO, or Pb,O, to the state of permanganic acid, and a comparison of the colour with that of a solution of standardized permanganate. One gramme of turnings is gradually warmed with 20 C.C. of 1.2 nitric acid, heated to the boiling-point, and allowed to cool. The solution is made up to 100 c.c., and 20 C.C. of it are placed in a 50 C.C. flaek with 15 C.C. of nitric acid (363 B., specific gravity 1.33, and free from nitrous acid), and raised on 8 sand-bath to 90" C. One gramme of previously ignited red-lead is then added, the heating continued for three or four minutes, a little more red-lead dropped in, and the whole quickly cooled.The liquid is diluted to the mark, filtered through asbestos, and examined in the colorimeter against a solution of permanganate con- taining 1.582 grammes per litre. F. H. L. Separation of the Rare Earths by Fractionation. 0. EIolmberg. (Ofuersigt af kongl. Vetensk. Akad. Forhandl., 1903, xxviii. ; through C h m . Zeit. Rep., 1903, 266.)-For the purpose of separating the rare earths by fractionation, the author recommends their repeated crystallization in the form of salts of the commoner organic acids, or of the sulphonic acids of the aromatic series. The method works the better as the acid is stronger, and therefore the sulphonates of benzene and naphthalene have been mostly employed. As an example, Holmberg mentions that he has succeeded in obtaining pure neodymium from didymium oxide by dissolving it in m-nitrobenzene sulphonic acid.The material was only submitted to one fractionation, which was divided into three stages, the first consisting of fifty, the second of ninety, and the last of twenty recrystallizations. The atomic weight of the product was 143.6, as against Jones' figure, 143.55. F, H. L. The AnaJysis of Persulphates. C. Marie and L. J. Brunel. (Bull. Soc. Chim., 1903, xxix., 930-933.)-The following volumetric method is recommended for the analysis of alkaline persulphates: From 0.3 to 0.4 gramme of the sample is dissolved in 100 C.C. of water, and the solution neutralized (with methyl orange as indicator), heated with 2 C.C. of methyl alcohol, first for fiveminutes at 70" to 80' C., and then boiled for ten minutes.It is then cooled and titrated with sodium372 THE ANALYST. hydroxide solution with methyl orange as indicator. One C.C. of the standard alkali is equivalent to 0.0135 gramme of potassium persulphate, 0.0119 gramme of sodium persulpbate, and 0.0114 gramme of ammonium persulphate. Taruggi's method of boiling a solution of ammonium persulphate with sufficient standard sodium hydroxide to completely replace the ammonium is shown to yield too high reenlts, which is not the case when methyl alcohol is also present. C. A. M. Determination of Sulphuric Acid. R. Silberberger. (Ber., 1903, XXXVi., 2755 ; through Chem. Zeit. Rep., 1903, 266.)-The author recommends that eulphuric acid should be precipitated as strontium sulphate. If an alcoholic solution of strontium chloride is added to a liquid containing iron as well as sulphuric acid, the precipitate will be entirely free from either iron or chlorine, and the process is therefore specially suitable for the estimation of sulphur in pyrites.F. H. L. Estimation of Free Phosphoric Acid in Superphosphates. A. Herefelder. (Laicdw. Versuchsstat., 1903, lvii., 471 ; through Chem. Zeit. Rep., 1903, 252.)-The author finds that none of the methods hitherto suggested for this purpose can be relied upon, and he proposes a new one, which depends on the fact that free phosphoric acid is soluble in ether, while phosphates are insoluble; also on the neutrality of monobasic and the alkalinity of dibasic phosphates towards methyl orange. One gramme of the finely-powdered sample is extracted in a Soxhlet for ten hours with dry ether.The solvent is distilled off, the residue treated three times with 20 C.C. of water, and the liquid passed through a filter. The paper is then washed with water just tinted with methyl orange as long as any reddening is noticeable. The filtrate is titrated with normal alkali, the number of C.C. used multiplied by 7.1, giving the percentage of free phosphoric acid in the material. Should the amount of alkali consumed be less than 0.5 c.c., the whole operation should be repeated on a larger quantity of the sample. As a check, and to see that no combined phosphoric acid has been diseolved, phenolphthalein may be added to the above liquid, and the titration continued till the pink resists two or three agitations ; the volume so consumed ought not to exceed 0.05 C.C. With the aid of this process, the author has found that German and Hungarian superphosphate is much richer in free phosphoric acid than the British or French material.He considers it would be desirable to limit the amount of free acid, and t o sell superphosphate under a guarantee in this respect, as well as under that of water - solu ble phosphoric acid. F. H. L. The Use of a Mercury Cathode in Electrochemical Analysis. Edgar F. Smith. (Journ. A ~ T . Chem. SOC., xxv., 883.)-The electrolysis is carried out in a small beaker, near the bottom of which a thin platinum wire is fused through the side. Internally, this wire dips into a layer of mercury which covers the bottom of the beaker and forms the cathode, whilst externally it touches a disc of sheet-oopper on which the beaker stands, and which is connected to the negative electrode of 8THE ANALYST.373 cell. The solution to be eleotrolyzed is poured on top of the mercury, which Is weighed before and after the determination after washing with water, aloohol, and ether, and then standing over sulphuric acid for fifteen minutes. Using this arrange- ment, good results were obtained in the analysis of the sulphates of copper, iron, zinc, and nickel, the acid liberated being in each case determined by titration; iron was quantitatively separated from thorium, uranium, zirconium, and titallium in sulphuric acid solution ; and fairly good results (error from 0.4 to 0.9 per cent. of NO,) were obtained in the analysis of nickel nitrate, practically none of the nitric acid being reduced, even in the presence of sulphuric acid.The method was also applied to the analysis of the chlorides of sodium, barium, and strontium, a silver-coated platinum gauze being used as anode. As soon as the whole of the salt had been decomposed this was removed and weighed, a platinum spiral being substituted, On now reversing the current, the metal passed into solution again, the alkaline solution being tben titrated. With sodium chloride the results were especially good. The author mentions that these last determinations can also be carried out using a platinum spiral instead of a mercury cathode. (In this case, whilst the chlorine is retained by the anode as fast as it is formed, an alkaline hydroxide is evidently produced directly in the solution around the cathode.-AssTRAcToR.) A.G. L. Preparation of Ammoniacal Cuprous Chloride for Gas Analysis. A. Waegner. (Oesterr. Chem. Zeit., 1903, vi., 410.)-Five parts by weight of crystal- lized cupric chloride are dissolved in 25 parts of water, and 10 parts of strong hydrochloric acid (specific gravity 1.19) are added. The flask is heated to incipient ebullition, the flame is removed, and sodium hypophosphite is introduced in small portions with constant agitation. The liquid, originally olive-green, becomes brown and, finally, colourless, when reduction is complete. I t is cooled quickly by placing the flask in cold water, supersaturated with strong ammonia, and 10 per cent. ammonia is added to any desired amount. F.H. L. Valuation of Explosives by Explosion in Lead Cylinders. (Chent. Zezt., 1903, xxvii., 898.)-The following rules for the above process were laid down at the Berlin Congress of Applied Chemistry last summer. The cylinders in which the samples are exploded are to be made of the purest possible grade of soft lead cast in a suitable mould, so that they may be 200 millimetres high, 200 millimetres in diameter, with a concentric hole 125 millimetres deep and 25 millimetres in diameter, reaching from one of the flat ends. After being cast they must be allowed sufficient time to cool, so that their temperature all through shall not exceed 15' or 20" C. Ten grammes of the explosive to be tested are weighed out, and wrapped up into a cartridge, 25 millimetres in diameter, in tin-foil weighing from 80 to 100 grammes per square metre. In the middle of the material a 2-gramme cap is placed, which is to be ignited by an electric spark. The cartridge is then gentlypushed to the bottom of the hole in the lead cylinder by means of a wooden stick, the electric conducting374 THE ANALYST. wires being held centrally in the aperture. The rest of the hole is then filled up by pouring into it well-dried quartz sand, which has been passed through a sieve made of wire 0.35 millimetre in gauze, and having 144 meshes per square centimetre. The excess of sand is removed. The cartridge is then fired, the cylinder inverted, the residue shaken out, and the hole in the block is wiped out with a brush, I t is finally filled with water, the quantity needed, less that corresponding with the original capacity of the hollow space, being an indication of the power of the explosive taken. All the cylinders used in any series of tests must be made from the one melt of lead. The results obtained must only be considered comparative provided they refer to matends giving the same kind of explosion-explosives in which the development of pressure occum at different speeds cannot be valued in this way. At least three tests muat be made on each explosive. The trustworthiness of the results is greatly influenced-(a) by the uniformity in temperature of the lead cylinders at the time of loading, ( b ) by the homogeneity of the sand filling, and (c) by the mutual agreement of the measurements. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9032800367

出版商:RSC    

年代:1903

数据来源: RSC

摘要:

374 THE ANALYST. APPARATUS. A New Absorption Pipette. E. H. Wikander. (Chew. Zed., 1903, xxvii., 845.)-This is a modification of the Ettling gas pipette, having the advantage that the capillary tube is straight, and therefore easier to clean, while the whoIe apparatus is more convenient to manipulate. It is charged with the liquid reagent through a funnel by means of the orifice b,. the quantity admitted being sufficient to fill the lower bulb and just to enter into the upper one. As the liquid rises into the capillary the amount added can be told exactly. The gas is introduced under pressure by connecting e through a narrow rubber tube with the measuring vessel, the liquid being thus displaced into the upper bulb. A clamp on the rubber is then tightened, the pipette is held with a finger over b, and shaken till absorption is complete.Gas is not likely to escape during the process because the lower end of the tube in c is depressed so far into the bottom projection. The apparatus is emptied of reagent and rinsed by forcing air in through e till all the liquid is in the upper bulb, then inverting the pipette and allowing it to run out of b. For employment with solid absorbents, the extremity of the lower projection may be cut off and a rubber cork used to close the hole ; through it the reagent can be introduced. F. H. L.THE ANALYST. 375 A New Kjeldahl Apparatus. M. Vogtherr. (Chem. Zeit., 1903, xxvii., 988.) -The accompanying illustration represents an improved form of apparatus for nitrogen determinations which has the advantage that both the treatment with sulphuric acid and the subsequent distillation of the ammonia are carried out in the aame vessel, while, arrangements being made for the absorption of the sulphurous oxide evolved, the operation need not be performed in the fume cupboard.The reaction vessel is a Jena flask holding 500 c.c., and it is connected by means of a ground joint to the cap and leading tube, which supports a pear - shaped receiver with the aid of a com- mon or rubber cork. The Erlenmeyer flask is held on a stand which can be altered in height. The substance under treatment, toget her with the sulphuric acid, etc., is brought into the re- action flask, a sufficient quantity of sodium hydroxide to cover the exit of the pear tube is placed in the conical flask, and the flame is started.The SO, formed is practically all absorbed by the soda, 80 that the laboratory atmosphere is not vitiated, the size of the pear preventing all danger o the liquid being drawn back. When all the gas is given off, the adjustable stand is lowered till the liquid clears the mouth of the pear tube; heating is then continued in the usual way, the sulphuric acid volatilized condensing in the hollow stopper of the flask, and thus rinsing down any particles of carbon. When this stage of the operation is ended, the pear is carefully rinsed with water, a new receiver is put in place charged with standard acid, soda is introduced into the Jentt Assk through a tube-funnel, and, in presence of zinc, the distillation is performed aa usual. It may be modified by fusing into the hollow stopper a glass tube leading to the bottom of the reaction flask, so that a stream of gas or vapour may be passed through the whole; and the pear may be replaced by a worm condenser or the like.The same apparatus is available for several other purposes. F. H. L.376 THE ANALYST. A Combined Waah-Bottle Tube. (Chem. Zeit., 1903, xxvii., 826).-The annexed illustration sufficiently explains the construction of a combined inlet and outlet tube for wash-bottles, which requires a cork having only one hole, and which can therefore be used in flasks having very narrow necks. The device may be employed in a reversed direction for the inlet and outlet tubes of a gas-washing flask, for which purpose a rubber ball, bored with numerous small holes, attached to the base increases its efficiency.F. H. L. Heating Arrangement for Extraction Appazatus. (Zeit. fiir ofentl. Chent., 1903, ix., 305.)-For extracting substances in a Soxhlet apparatus at the boiling- point of the solvent used a device is described which consists of a metal jacket enclosing the Soxhlet tube. The jacket may be filled with water or glycerin and water where higher temperatures than 100' C. are required, and is connected by tubes to a reservoir for maintaining a constant level of liquid in the jacket. A ring burner, placed just under the jacket and above the flask containing the solvent, is employed w. P. s. for heating the contents of the jacket to the desired temperature. A Uaa Drying Apparatua. F. Bolm. (Chem. ,Yeit., 1903, xxvfi., 1037.)-Thia is an appamtne intended for the drying of either air or oxygen in organic combustions. I t consists of two portions.The former is a vertical cylinder with 8 constriction a short distance above its base, on which lies a perforated lead plate. Its stopper is hollow, and is itself stoppered, the bottom of the hollow space being prolonged as. a tube through the lead disc to the base of the cylinder. Laterally there is an orifice in the outer stopper which may be brought into juxtaposition with either of two side- tubes in the neck of the cylinder, so that either air or oxygen may be passed through the vessel. The cylinder is charged by drawing out the main stopper a short distance and then dropping on to the lead plate in succession glass beads, cotton-wool, soda- lime, and a small quantity of calcium chloride. The main stopper is put back, the inner stopper is removed, and through the aperture, viti the hollow space and the descending tube, strong sulphuric acid is charged into the portion of the cylinder below the waiet until the extremity of the tube is sealed. The second portion of the apparatus coneiets of an S-shaped vessel built up of two U-tubes lying one above the other on their sides, conneoted at the one end by means of a bent tube with the lateral exit of the aforesaid oylinder, and at the other with a short tube for connec- tion with the oombnstion-tube. The system of tubes is carried in slotted supports, and is joined together with three rubber sleeves. The apparatus is made by P. Altmann, of Berlin.

ISSN:0003-2654    

DOI:10.1039/AN9032800374

出版商:RSC    

年代:1903

数据来源: RSC

摘要:

376 THE ANALYST. Erraturn.-Page 324, bottom line, in blank space insert “in strong hydro- chloric acid.”

ISSN:0003-2654    

DOI:10.1039/AN9032800376

出版商:RSC    

年代:1903

数据来源: RSC