摘要:

THE ANALYST. MAY, 1903. OBITUARY NOTICE. THE LATE MR. HANBURY. THE Society of Public Analysts, along with many other bodies throughout the country, have cause for sincere regret at the loss sustained through the death, at the height of his activity and power, of the Right Ron. R. W. Hanbury, M.P., the Minister for Agriculture. Of late years legislative changes have brought the members of the Society into closer relations with the Board of Agriculture, and in Mr. Hanbury they found one who was not only sympathetic towards them, but who, as in his agricultural work, exhibited a keen desire to make himself acquainted with all the various subjects brought under his notice. Thus, in the Amendment of the Sale of Food and Drugs Act, so far as this affected milk, cream, butter, and other dairy produce, Mr.Hanbury and the Depart- ment under his control gave a ready ear to the representations of the Society, and availed himself fully of the help of its members in the setting of evidence before the various Departmental Committees which he appointed. On several occasions, too, he had granted interviews to the Society’s representa- tives when Bills affecting the work of Public Analysts were under consideration. To him was due, in great measure, the carrying out of numerous inquiries and investigations in which analysts had considerable interest, and which affected their own work largely, His removal from a sphere in which he had shown so much activity, and where he had already done a great deal to make his Department one of real usefulness to the country at large, and to the agricultural and other interests with which it came into relation, is one that will be severely felt. J. A. V.

ISSN:0003-2654    

DOI:10.1039/AN9032800137

出版商:RSC    

年代:1903

数据来源: RSC

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138 THE ANALYST. NOTE ON THE DETERMINATION OF CASEIN PRECIPITATED BY RENNET. BY H. DROOP RICHMOND, F.I.C. (Read at t b Neetirtg, February 4, 1903.) IN the ANALYST (xxvii., 37) an abstract of a paper on this subject by L. Lindet appears. He objects to the usual methods of casein determination as being inexact, and proposes a densimetric method for the determination of the casein precipitated by rennet. As he mixes up the relations between density, specific volume, and per- centages by weight and volume, I wish to point out that his method and formulae are approximations only. Further, as he does not point out that what he estimates is not casein, but the curd produced by rennet, which contains roughly 10 per cent. of mineral matter, it is advisable to draw attention to the exact meaning of the figure obtained.If we have a solution (milk) containing two substances (whey and curd), the density of one of them (whey) can be calculated, if we know the density of the solu- tion 100 (milk) and of the substance removed (curd) and the percentage removed. Starting from the definition Density = and taking for convenience volume’ C.C. of milk, we have- (100 - c) D, - total weight - weight of curd D, = - 100 - cD, total volume - volume of curd’THE ANALYST. 139 where c =percentage by weight of curd, DM = density of the milk, D, =density of the whey, d = density of the curd. Solving the above equation for c, we get : From my own experiments I deduce the value 0.71 for K. simplified to the approximation formula : This formula may be 100 (DM -- Dw) 100 (D, - Dw) ‘= 1.036 (I - 0.71 x 1.029)’ Or 0.279 ’ which gives the factor for multiplication as 3-58, a figure in substantial agreement with Lindet’s 3.5.Lindet also gives a formula for calculating the specific gravity of the milk free from fat, in order to eliminate the influence of the fat, but his formula is not correct. The true formula should be as above. (loo -.f) DM fDM ’ Ds = 100- - 0.93 where D, = density of the milk minus fat, DM = density of the milk. f =percentage by weight of fat. A very good and simple approximation formula is : ~ 0 0 0 D, + f, 1000 The whey produced from milk containing fat always contains a small percentage of fat, and the density of the whey should be corrected in a manner similar to that of the milk. A small error is introduced by using the corrected densities, because the curd removed is calculated as a percentage of the milk devoid of fat, and not of the whole milk.This can be approximately corrected by using a slightly smaller factor. The difference between Lindet’s figure (8.5) and my own (3.58) may be due to this. A simple approximation formula, which will give very fair results, is : D, = = { GM + fM - (GW + fW) } 0’35, where c =percentage of curd by weight, GM = lactometer degrees of milk, Gw = lactometer degrees of whey, f M =percentage of fat in milk, f = percentage of fat in whey. The weight of cheese obtained does not depend entirely on the percentage of curd, but the fat taken down with the curd is an important factor, The curd esti- mated by this method will not agree with the proteid precipitated, but with proteid140 THE ANALYST.plus mineral matter, the latter being about 10 per cent. of the curd; still less will the figure obtained represent the casein in the milk. It should be clearly understood that Lindet’s method estimates only the per- centage of dry curd produced by rennet, and does not give an estimation of proteid matter. With this limitation, the method should be a useful addition to our dairy tests. DISCUSSION. Mr. RICHMOND, in reply to questions put by the President, Dr. Lewkowitsch, and Dr. Voelcker, said that this was a method for calculating the amount of curd sepa- rated from the milk by the rennet, and was capable of being used as a practical test. It would not indicate directly the amount of cheese produced in practice, because of the variations which occurred in the proportions of fat and water. I t would, how- ever, afford a rough indication of the value of milk for cheese-making, H e had not compared the calculated results with the amount of cheese produced, but they were in agreement with the amount of the curd before it was made into cheese.Mr. LLOYD thought that for the cheese-maker it was less important to know the quantity of casein than to know the quantity of curd which he ought to obtain. The use of such a method as this by anyone but a most careful chemist seemed likely to be fraught with many pitfalls. The composition of the whey would vary with the temperature and with the time for which the rennet was allowed to act. For every moment that the whey acted on the curd precipitated by the rennet there was an increase of acidity, and simultaneously with that a withdrawal of lime-salts from the curd.Mr. RICHMOND said that, whereas at present the cheese-maker worked in the dark, he could by the use of a method such as this arrive at some idea of the amount of curd he ought to obtain ; and then, assuming an average percentage of curd in the finished cheese, he could calculate approximately how much cheese he ought to expect. After all, the increase of acidity referred to by Mr. Lloyd would not, he thought, be so great as to affect very seriously the density factor ; nor mould any great difference be caused by the enzyme action which would be also proceeding. As the density of the actual whey obtained could be determined, any errors due to these causes would be practically eliminated. Dr. SCHIDROWITZ inquired whether any attempt had been made to measure the strength of the enzymic action in whey. Mr. RICHMOND said that a quite well-known method of determining the strength of rennet-which was really the strength of the enzyme-was by adding a known quantity of the rennet to milk, and observing the time in which, at a constant tem- perature, curdling was produced.

ISSN:0003-2654    

DOI:10.1039/AN903280138b

出版商:RSC    

年代:1903

数据来源: RSC

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THE ANALYST. 141 A PLEA FOR THE BETTER CONSIDERATION OF PHYSICS I N ANALYTICAL METHODS. BY H. DROOP RICHMOND, F.I.C. (Rend at the Meeting, March 4, 1903.) I AM using the term (( Physics” in perhaps a wider sense than finds general accept- ance ; I include in it the language of Physics, viz., Mathematics, and also what is on the borderland of Physics and Chemistry- mass action. Our analytical determinations would be more exact if we paid more attention to points other than the chemical reaction which is taking place. For instance, we pay little attention to the fact that small particles hold by surface energy around them a layer of liquid which is appreciable in bulk as compared with the particles them- selves ; if, as usually happens, this liquid contains soluble substances, which we wish to wash away from the particles, we can only remove the soluble substance from the layer round the particles by diffusion.The process of diffusion is a slow one, and as we cannot afford to let our determinations proceed for an infinite time, we must eibher be content with incomplete washing or adopt other means of separation. The usual means of determining completeness of washing may be quite fallacious, as, firstly, reactions in very dilute solutions require time for their completion ; and, secondly, the rate of diffusion from the condensed layer may be so slow that the few drops of filtrate taken may be too weak in the substance sought for to give a reaction indicating the considerable amount of substance left behind. This is partly recog- nised, though not, perhaps, as fully as it should be, when we say that certain piadpi- tates carry down traces of other substances ; we usually dissolve iip and reprecipitate our precipitates, and thereby reduce the concentration of some of the substances in the condensed layer to infinitesimal limits.The largest errors probably occur in volumetric work where a precipitate is formed ; thus a solution of barium hydroxide set with standard sulphuric acid will not give the same titre with standard hydro- chloric acid. Extraction by immiscible solvents is an operation in which diffusion plays a large part ; if our solvent were completely immiscible with water, we could only extract a substance soluble in both by digusion from one solvent to the other, an operation requiring intimate mixture to give large surface, and much time.Petroleum ether is practically a solvent of this kind, and the tediousness of complete extraction by this substance need not be dwelt upon. A solvent fairly soluble in water has the advan- tage that the dissolved solvent bearing the substance to be dissolved diffuses very much quicker into the solvent,.and this explains the rapidity of ether extraction. When we have an emulsion from which the substance insoluble in water and emulsi- fied is to be dissolved, an immiscible solvent is usually quite out of the question, and a partially miscible solvent is generally employed. The drawback of the partially miscible solvent is that substances insoluble in the solvent itself dissolve in the water dissolved in the solvent ; successive me of solvents of decreasing miscibility will frequently be of use in effecting clean and quick separations.142 THE ANALYST.A physical determination which is often employed as an analytical datum is ‘‘ viscosity,’’ and probably no term is more incorrectly used than this. Viscosity is, of course, the internal friction between molecules of a liquid ; as a rule, it is deter- mined by apparatus, which is affected to the minimum extent by viscosity and to the maximum extent by surface energy and the friction between the liquid and the apparatus itself. In an accurate measurement of viscosity it is necessary to exclude all friction between the liquid and the walls of the vessel, and the flow must therefore be suffi- ciently slow not to be turbulent--i.e., the flow must not be rapid enough to disturb the layer held by surface energy against the sides of the vessel-the exit surface of the liquid from the apparatus must not be small, as in this case the attraction due to surface energy between the liquid flowing out and the orifice cannot be neglected.The usual form of apparatus, in which a liquid is allowed to flow through a narrow orifice, allows a turbulent flow through the orifice, and as this is usually made small, the surface energy at issue is an appreciable factor ; in this kind of apparatus the head of liquid is not usually constant, and therefore the impelling force over- coming friction varies. There is no reason why correct results should not be obtained with a varying force, if the rate of variation is known and the resulting equation integrated between the proper limits ; but it militates against accuracy to assume, as is done, that the effect of varying head can be equated to a constant.There is no difficulty in arranging simple apparatus in which slow and constant motion is insured, and the friction between wholly submerged surfaces measured. Many of our processes depend on distillation, more or less fractional. Fractional distillation depends entirely on the rate of condensation, and this, again, depends entirely on the difference of temperatures and the rate at which heat can be abstracted ; if we wish for constancy of results we must arrange our conditions to approximate to one of the two limits. Either we must eliminate condensation by having no difference of temperature between the inside and outside of our still-head, or we must make the condensation approximate as nearly as possible to completeness.It is not enough to attempt constancy of conditions by specifying rate of distillation, size, and shape of cooling surfaces, if the temperature of the outside of the still-head is not kept constant, and the rate of condensation is not kept near one of the limits. The law of mass action is frequently not kept sufficiently in mind; this is that the speed of a reaction is proportional to the mass (measured in molecules) of the reacting substances ; it is also dependent on temperature. In solution water and substances other than the main reagents in solution may take part in the reaction, and therefore concentration and impurities may modify the speed.No reaction, theoretically, proceeds to completeness, and every reaction is reversible ; we very often, therefore, in measuring the end of a reaction, only measure a point of equilibrium, which may vary with dilution and the presence of other substances present. A few simple and well-known examples will emphasize the points. Equivalent quantities of silver nitrate and sodium chloride give a solution which is rendered turbid both by silver nitrate and sodium chloride. (6) Equilibrium point varying with temperature, and the presence of substances (a) Varying point of equilibrium.THE ANALYST. 143 not entering into the main reaction. Boric acid in aqueous solution gives a pink colour to phenolphthalein in cold solution when about one-third is neutralized ; dilu- tion increases the pink colour, warming lessens it ; when polyhydric alcohols are added, the whole of the boric acid can be titrated.Ammonium magnesium phosphate varies in composition according to amounts of ammonium salts present. The reaction between hydrogen peroxide, and iodides is only complete in a reasonable time when a large excess of iodide and acid is present. We very frequently ignore either time, or temperature, or dilution in our deter- minations, when we should, at all events, consider whether the effects of these have been reduced either to a limit or to constancy. For instance, Hubl’s iodine-absorption method has a limit of time, but the effect of variations in the temperature of the laboratory is ignored.Sometimes we try and meamre the speed of a reaction ; in doing this, before we can measure the “ constant,” we must know the kind of reaction which is taking place, and this is a thing which we almost always ignore in analytical chemistry. This is probably because we have neglected to habituate ourselves to use the language in which physical facts can be most simply expressed-the infinitesimal calculus ; it is a matter of regret that an elementary knowledge of mathematics (and the treatment of physico-chemical problems does not require profound knowledge) is not looked upon as more essential for the analyst. The speed of a reaction under deter- mined conditions may be as valuable an analytical datum as the mass of a precipitate or the deviation of a ray of polarized light, and in some cases-e.g., enzyme estima- tion-the only available method of analysis; yet we make but little attempt to estimate it properly.I have ventured to bring this brief sketch before the Society because there is a tendency at the present time to standardize methods of analysis. Standardization usually means laying down a number of exact and sometimes inconvenient condi- tions, and leaving an important one alone ; we may all ‘‘ dry at looo,” but my idea of this may be to pass a rapid current of dry air at about 100” over my sample, and my neighbour may box his sample up in a bath kept strictly at loo”, with but little ventilation ; our results ‘‘ at looo ” very likely will not agree. Because one man has his balance between a window and a flue which gets hot towards the afternoon, it is no reason why we should all effect structural alterations in our laboratories to do likewise. I wish to study the effects of physical conditions and the laws under- lying methods, and to either eliminate them or evaluate them between my limits of working. DISCUSSION.(c) Composition of precipitate affected. (d) Speed of reaction varying. The PRESIDENT (Mr. Fairley) remarked that one advantage of physical methods was that, as a rule, they did not involve the destruction of the substance tested. Of course, Mr. Richmond’s paper was far wider than that in its scope. It represented an effort towards enabling different operators in different laboratories to obtain more uniform results than had been hitherto the case. No doubt greater attention to144 THE ANALYST.constancy of physical conditions would minimize the differences which existed in different laboratories where the work was equally faithfully and honestly done, but where, in some cases, perhaps, there was a little inattention to points such as those which Mr. Richmond had mentioned. With regard to the use of polyhydric alcohols in the titration of boric acid, he would like to ask Mr. Richmond whether that had been proved as a general statement? and whether in place of glycerine (the value of which for this purpose was well known) any other polyhydric alcohol might be used. Nr. BLOUNT, referring to the washing of precipitates, observed that it was not sufficient to put on a precipitate so much water and to take it off, and to go on doing that at a regulated rate until the filtrate, on being tested, indicated that no more soluble matter was passing through.There must be time to allow the water to penetrate into the mass of the precipitate, this being particularly the case with precipitates such as alumina and semi-colloidal matters, which were very loath to take the water poured on to them. That was one of the reasons why the advantage of the Gooch crucible was largely illusory, while the filter-pump was an equal sinner. The extraction by solvents was a parallel case, but he was not quite sure that Mr. Richmond had made out his point in regard to this. Mr. Richmond said that he would prefer to use a solvent which should be soluble to the same extent as ether in the watery solution carrying the material to be extracted.He ( M i . Blount), how- ever, thought that the solvent remaining in the aqueous solution or emulsion might well retain, to the precise extent to which it was there present, a proportion of the material which it was destined to take ouh, and in that degree the action of the solvent would be imperfect, What he thought Mr. Richmond meant to say was that the solubility of the ostensibly non-miscible solvent in the aqueous solution was useful, inasmuch as it would allow the particles to be better mingled with the aqueous material. In that he agreed; but he thought a similar result might be attained by more complete agitation. With regard to the determination of viscosity, he thought it was right that Mr. Richmond should have called attention to an error that was frequently incurred by neglecting the variation of the head.I n Redwood’s viscosi- meter the head was variable, and was designed to be variable, the time being the unit observed. That method, however, was not always convenient, because the time was sometimes too long, and in that case it was better to get the head constant and vary the time. That could be done by a device, pointed out many years ago by Mr. Allen, of closing the top of the viscosimeter and allowing the liquid to dribble out under a constant head.. He would like to hear Mr. Richmond’s views, if he had studied the question, as to the real difference between the determination of viscosity by the flow of a liquid through a tube, and the flow of the same liquid through an orifice. Some years previously he had gone very carefully into this, and had tried to make up his mind from the best authorities he could find and from his own experi- ments as to whether a truer expression of the internal rubbing of the liquid was obtained by allowing the liquid to flow through a sharp-edged orifice or through a tube, according to the method of Pouseille, but he had been unable to arrive at any definite conclusion.Dr. LEWKOWITSCH said that, in shaking out with ether, one knew that the ether was soluble to a certain extent in the aqueous solution, and consequently it was quiteTHE ANALYST. 145 plain that any ether so dissolved would carry with it some of the matter to be extracted; but when a second, or perhaps a third, shaking was given, a point was reached where for practical purposes further shaking was no longer useful or necessary. The point to be considered was how far analytical methods were accurate, and how far they should be carried.With regard to the determination of viscosity, it did not seem necessary to employ the calculus when one could make use of Mr. Allen’s device for keeping the head constant, which was quite accurate enough. For practical purposes the object was to obtain, not the internal viscosity of the liquid, but merely a practical guide as to judging between oil and oil. With regard to distillation, he understood Mr. Richmond to make a plea for determining the distillation point without using any condenser ; but in that case, how did he propose to prevent air condensation ? In distilling benzol or petroleum ether in the laboratory some air condensation was bound to occur, and surely it seemed far better to introduce a Liebig condenser of a certain size or a certain condensation, and insure as much condensation as possible. With regard to the determination of iodine absorption, he thought he need only refer Mr.Richmond to the classical work of Wijs, who hold investigated the process under varying physical conditions, and had shown that its results, under the conditions laid down for its practical working, were in accord with those indicated by theory. Mr. HEHNER said that, from a practical point of view, chemical analysis had always been a compromise bet ween conflicting conditions. The conditions, however, under which reasonable accuracy might be obtained had been investigated over and over again, and were verified every day in the course of laboratory work.This, of course, ought not to prevent every attention being given to the effects of physical conditions. It must, however, be pointed out that the ideas of modern physical chemistry, though expressed in more precise and possibly more correct and intelligible language, were largely ideas with which we were already familiar, though for many years they had been expressed in other ways. Dr. DYER, referring to Mr. Blount’s remark in reference to the Gooch crucible, haid that it did not follow that the use of a Gooch crucible must necessarily involve dispensing with the common-sense precaution of washing by decantation.Many precipitates could be moat satisfactorily washed by decantation, and the Gooch crucible then served well for rapidly finishing the filtration after the precipitate had been washed. Mr. RICHMOND, in reply, said that there were two polyhydric alcohols which had been used in the titration of boric acid with satisfactory results-namely, mannitol and erythrol. His point in regard to extraction was that, in the case of ether, the extraction would be more rapid owing to more rapid diffusion. Similar results would no doubt be obtained with petroleum spirit if the agitation were very prolonged. With regard to the determination of viscosity, he had not overlooked the device referred to by Mr. Blount, but that device-which, by the way, he believed was due jointly to Nr. Allen and Mr. Chattaway-was absent from most of the apparatus at present in use. He thought there was a very apparent advantage in determining the viscosity by some other means than Redwood’s viscosimeter, in which the flow of the oil from the orifice varied at different stages. I n reference to Dr. Lewkowitsch’s remarks, it146 TgE ANALYST. was quite easy to eliminate the effect of air condensation by enclosing the distilling flask in a, tin jacket through which a current of vapour could be passed, or by the use of a good form of fractionating column, it might be made to approximate perfect condensation. I n referring to the determination of iodine absorption, what he had desired to emphasize was that the variation which occurred in the temperature of the laboratory during a period of, say, a couple of hours was in some cases sufficient to exercise an important influence, especially as affecting the speed of a chemical reaction. He could certainly think of more than one analytical process showing the influence of physical methods, as, for instance, Mr. Allen’s method for the determina- tion of urea.

ISSN:0003-2654    

DOI:10.1039/AN9032800141

出版商:RSC    

年代:1903

数据来源: RSC

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146 TgE ANALYST. NOTES ON SOME VANADIUM REACTIONS. BY C. A. MITCHELL, B.A., F.I.C. (Read at the Meeting, Murch 4, 1903.) THE following notes are the outcome of some work I have recently done for a firm of ink manufacturers ; and as some of them have an analytical bearing, I have thought them of sufficient interest to bring before the Society. It has long been known that ammonium vanadate forms a dark soluble compound with gallo-tannic acid, which has the reputation of being an excellent permanent ink, and has been so described in different standard text-books (e.g., Miller’s (‘ Elements of Chemistry ”). The discovery of this fact is attributed to Berzelius (Dingler’s polyt. J., 1835, hi., 237), but I have been unable to discover any reference to the subject in the ‘‘ Jahresberichte ” or ‘‘ Lehrbuch ” of Berzelius.Appelbaum (Diqler’s polyt. J.: 1889, cclxxi., 423), on making experiments with gall extracts and solutions of gallo-tannic acid, found that both the writing and ink faded in a short time, and hence doubted whether Berzelius had ever made any experiments with the ink. I have repeated Appelbaum’s work, and can confirm what he says about gall vanadium ink, though I find that gallo-tannic acid gives an ink of somewhat greater permanency than was found to be the case by him. I n making experiments with other substances, I have found that the law established by Schluttig and Neumann (“ Die Eisengallustinten,” p. 33) for iron salts also applies to ammonium vanadate-viz., that it yields an ink with substances containing three adjacent hydroxyl groups.Thus, gallic acid, logwood extract, and haematoxylin combine with ammonium vanadate to form black inks, whilst phenol, benzoic acid, saccharin, etc., do not form such compounds. Unfortunately, none of these inks has proved to be satisfactory as regards permanency, the writing in each case becoming more or less yellow with the lapse of tinie, and hence ammonium vanadate, apart from its expense, is not a suitable constituent of writing inks. In the course of this work I made a number of experiments on the reducing action of organic acids upon ammonium metavanadate. Though all that I tried gaveTHE ANALYST. 147 a lemon-yellow coloration, probably due to the formation of metavanadic acid (HVO,), only a few showed marked reducing properties, the most notable of these being oxalic acid.If a 1 per cent. solution of oxalic acid be mixed with an ammonium meta- vansdate solution of the same strength, the liquid becomes bright yellow, and on heating is rapidly reduced to a brilliant blue solution, which when concentrated deposits blue crystals, presumably consisting of hypovanadic oxalate, a compound of the oxide V,O,. This reduction is also brought about by tartaric, citric, and, to a much smaller extent, by inalic acid, similar blue colorations being produced in each case. If a solution of ammonium metavanadate be first treated with an ordinary hydrochloric acid solution of hydrogen peroxide, and then a few drops of a solution of oxalic acid be added, there is an immediate ruby-red coloration. Apparently in this reaction the hydrogen peroxide oxidizes the metavanadate to a higher vanadate, and then on adding the oxalic acid reduction takes place, with the formation of vanadic salts (compounds of vanadium pentoxide, V,O,), which have a red colour. This red solution can also be produced by first forming the blue reduction conipound with oxalic acid, and then oxidizing this with hydrogen peroxide.I n the absence of inorganic reducing agents, such as sulphur dioxide, this reaction can be applied &s a test for oxalic acid, Thus, on adding 2 drops of hydrogen peroxide to 1 C.C. of a 0.5 per cent. solution of ammonium vanadate and 0.2 C.C. of a .1 per cent. solution of oxalic acid, an unmistakable ruby-red colour is immediately formed. In the case of tartaric acid, however, there is only a very faint indication of red when 2 C.C.of a 10 per cent. solution are added ; or, in other words, oxalic acid has 1,000 times the reducing power of tartaric acid. The reducing power of citric acid is less than that of cartaric acid, whilst malic acid is weaker still. I n the case of succinic and phthalic acids, the formation of the red reduction compound can only be brought about by using a hot saturated solution of the acids. This reaction can also be used as a simple test for distinguishing between chromates and vanadates, which may be very similar in colour. If hydrogen peroxide be cautiously added to a solution of potassium chromate, the solution is oxidized to bichromate, and on now adding a solution of oxalic acid there is an evolution of oxygen, and a blue solution of the hypothetical perchromic acid is formed, which is speedily reduced to a green solution, probably consisting of a mixture of the yellow chromate and blue compound, and finally to a violet or pale green chromium salt, the exact nature of the change depending upon the relative amounts of the different substances present.DISCUSSION. The PRESIDENT (Mr. Fairley) said it happened that on the previous evening he had been lecturing on inks before the Bradford Society of Dyers and Colourists, and had then shown a number of experiments with vanadium inks. Salts containing certain heavy metals commonly produced dark-coloured solutions with many of the hydroxyl derivatives and with many of the hydroxyl and carboxyl derivatives of phenol, such, for instance, as salicylic acid and pyrogallic acid, which latter had not148 THE ANALYST. been mentioned by Mr. Mitchell, though it produced a very deep colour with ammonium vanadate. So far, however, as modern experience went, inks of this kind appeared not to have so great a, degree of permanence as they were stated by many older authorities to possess. In fact, he had come to the conclusion that, in order to make a durable ink, it was best to add a little finely-divided carbon, such as lamp- black, thus insuring the presence in the ink of a marking substance at least as permanent as the paper. Phenol itself did not strike a dark colour with many iron and other solutions, though it produced a blue colour with ferric chloride, and in that respect came within the same category as the hydroxyl derivatives referred to.

ISSN:0003-2654    

DOI:10.1039/AN9032800146

出版商:RSC    

年代:1903

数据来源: RSC

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148 THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER 30 U R N ALS. FOODS .AND DRUGS ANALYSIS. The Volumetric Determination of True Casein and other Proteids in Milk. (Bull. SOC. Pharm. Bordeaux, October, 1902; Ann. de Chim. anal., 1903, viii., 98-100.)-This is an extension of the author's volumetric method (ANALYST, xxii., 11; xxiii., 38). Twenty-five C.C. of the milk are shaken with 1 C.C. of a 30 per cent. solution of potassium oxalate, and then treated with 20 C.C. of a solution of 13.55 grammes of mercuric chloride and 36 grammes of potassium iodide in a litre, followed by 2 C.C. of glacial. acetic acid. After dilution to 200 C.C. the liquid is filtered, and 100 C.C. treated with 10 C.C. of potassium cyanide solution, equivalent to $G silver nitrate solution and 15 C.C.of ammonium hydroxide, and titrated with :& silver nitrate solution until a permanent turbidity appears. The difference between the number of C.C. used and 48 gives a value corresponding with the total amount of proteids in grammeg per litre of milk (cf. Tables, ANALYST, To obtain the proteids not precipitated by acetic acid, 50 C.C. of the milk are diluted with about 180 C.C. of water, and after the addition of 0.2 C.C. of glacial acetic acid, made up to 250 C.C. and filtered, and the proteids in 125 C.C. (= 25 C.C. of milk) determined as above, The difference between the two results gives the amount of true casein in a litre of the milk. C. A. M. G. Denigbs. loc. cit.]. The Detection of Methyl Alcohol in Absinthe. SanglB-Ferriere and Cuniasse. ( A m .de Chim. anal., 1903, viii., 82, 83.)-Fifty C.C. of the alcoholic distillate from the absinthe are mixed with 1 C.C. of pure sulphuric acid, and then treated with 5 C.C. of a saturated solution of potassium permanganate. The liquid should have a brown colour after a few minutes, and if any excess of permanganate has been used it is necessary to add 1 or 2 drops of a concentrated solution of tannin. After the addition of sodium carbonate to slight alkaline reaction the liquidTHE ANALYST. 149 is filtered, and the clear filtrate treated with 2 C.C. of a 0.1 per cent. solution of phloroglucinol and 1 C.C. of concentrated potassium hydroxide solution, when bright red colour is produced if methyl alcohol was present. No notice is taken of a yellowish-rose or violet coloration. As a confirmatory test, the alkaline filtrate is acidified with dilute sulphuric acid and shaken with a few centigrammes of powdered gallic acid until the latter hrts dissolved, and a little pure sulphuric acid cautiously poured down the side of the tube.After a few seconds a blue coloration appears at the zone of separation of the liquids when methyl alcohol is present. Both this and the preceding reaction are based on the colorations given by the formaldehyde formed by the oxidation of the methyl alcohol. C. A. M. Estimation of Sugar in Chocolate, A. Steinmann. (Schweix. Wochenschr. Chem. Pharm., 1903, xli., 65; through Chm. h i t . Rep., 1903, 56.)-In the original the author gives certain tables by the aid of which the proportion of sugar present can be calculated from an observation of the specific gravity of the aqueous extract of the chocolate and from the opticity of the liquid after decolorization with lead acetate. A correction is also made for the error introduced by the volume of the lead precipitate.The extract is prepared by shaking 50 grammes of the rasped sample with 200 C.C. of cold water at intervals for four hours, then filtering. The entire process is not complicated, and is stated to give concordant results. F. H. L. Occurrence of Salicylic Acid in Fruits. F. W. Traphagen and Edmund Burke. (Journ. Amer. Chem. Soc., xxv., 242.)-A number of fresh fruits were examined for salicylic acid by distilling the fruit with phosphoric acid, extracting the distillate with ether, evaporating the extract, and adding ferric chloride after taking up the residue in water.The quantities found in this way, which were exceedingly small (Eractions of a milligramme per kilogramme of fruit), are not absolute, but only comparative, and represent the amounts the authors succeeded in extracting ; they are important in view of the use of salicylic acid as a food preservative. The fruits from which salicylic acid was obtained were : strawberries, red and black raspberries, blackberries, currants, plums, black cherries, apricots, peaches, Concord grapes, crab-apples, standard apples and oranges. The acid is probably present as the methyl ester. A. G. L. A New Reaction of Cystin. A. Rim. (Bull. SOC. Chim., 1903, xxix., 249, 250.)-According to Benzinger, cystein gives a white precipitate with mercuric chloride, but cystin does not yield an insoluble compound until it has been reduced to cystein by means of zinc and hydrochloric acid.The acid mercuric sulphate of DenigBs, however, gives a white precipitate with cystin without previous reduction, and the reaction, which is extremely sensitive, can be used for the detection of that substance in urine. C. A. M.150 THE ANALYST. Reactions of Antipyrin with Mercury Salts. A. Moulin. (Bull. Soc. Chim., 1903, xxix., 201-203.)-Mercurous nitrate reacts readily with a solution of antipyrin, forming a nitro-mercurate having the formula C,,H,,N20(N0,),Hg. This compound forms small white crystals, which dissolve with difficulty in water, but are soluble in hot alcohol, nitric acid, and solutions of sodium and ammonium hydroxides. They also dissolve in sulphuric acid, yielding a red solution.A neutral mercuroso-mercuric reagent is prepared by dissolving 50 C.C. of mercury in a litre of a mixture of equal parts of nitric acid and water, expelling nitrous vapours by means of a current of air, and leaving the liquid in the dark until completely decolorized. A hundred C.C. of the solution is then mixed with 400 C.C. of a saturated solution of potassium nitrate and heated on the water-bath, whilst the liquid is saturated with yellow mercuric oxide, and is finally cooled and filtered. When this reagent is added little by little to a solution of antipyrin a white gelatinous precipitate is formed, whilst the liqnid assumes a green colour. On heating the flask on the water-bath the precipitate becomes crystalline and changes to a reddish- yellow tint. The precipitate formed in this reaction is a mixture containing the nitro - mercurate described above, together with nitroso - mercurous antipyrin, C,,H,,N,O(NO,),Hg,, and nitroso - mercuric antipyrin, C,,H,,N,O(NO,),Hg. The latter can be separated by their difference in solubility in nitric acid. They decom- pose explosively at about 205' C. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9032800148

出版商:RSC    

年代:1903

数据来源: RSC

摘要:

150 THE ANALYST. ORGANIC ANALYSIS. Estimation of Starch. 0. Lietz. (Ber. Deutsch. Pharm. Gesellsch., 1902, xii., 153-166 ; through Zeit. fiir Untersuch. der Nahr. und Geizussmittel, 1903, vi., 276- 277.)-A number of estimations of starch by various methods, including digestion under pressure, with or without the addition of lactic acid, inversion with hydro- chloric or nitric acid, and estimation of the sugar by polarization or titration with Fehling’s solution, precipitation with barium hydroxide, etc., were made by the author, who comes to the conclusion that none of these methods give accurate results. Even by heating the substance with lactic acid a certain amount of pentosan was hydrolyzed, causing too high results to be obtained on titrating with Fehling’s solution. As Mayrhofer’s method was not found to yield perfectly ash-free starch, the author has modified it as follows : From 2 to 10 gramlnes of the substance, which should not contain much cellulose, are boiled with 75 C.C.of a 5 per cent. alcoholic solution of potassium hydroxide for twenty minutes under a reflux condenser. After cooling, the solution is filtered through asbestos, the residue is washed with hot alcohol, then rinsed back into the flask, diluted with water to 200 c.c., and, after adding 20 C.C. of hydrochloric acid, heated for two and a half hours on a boiling water-bath. The solution when cold is neutralized, made up to 300 c.c., and the glucose estimated in 25 C.C. by Fehling’s method. Should much cellulose be present in the substance under examination, the residue obtained on digestion with the alcoholic solution of potassium hydroxide is warmed with 30 to 60 C.C.of a 5 per cent. aqueous solution of potassium hydroxide, whereby the starch is dissolved.THE ANALYST. 151 The solution is then made up to 400 c.c., filtered, and 200 C.C. of the filtrate neutralized and inverted with hydrochloric acid, as mentioned above. w. P. s. Estimation of Pentosans. R. J'Ager and E. Unger. (Ber., 1902, xxxv., 4440 ; through Chem. Zeit. Rep., 1903,37.)-From experiments on various substances, such as pure furfurol, pure arabinose, mucilage from linseed, pine-wood shavings, and a mixture of black and white pepper, the authors find that, when a material containing pentosans is distilled with hydrochloric acid, bodies other than furfurol are also precipitated by phloroglucinol from the distillate.It is believed, however, that the condensation product of furfurol and barbituric acid, first described by Conrad and Reinbach, will prove a means of precipitating furfurol only. This product is a pale- coloured amorphous powder which resists the attack of most solvents, and is only slightly soluble in 12 per cent. hydrochloric acid. Further experiments are in progress. F. H. L. The Detection of Small Quantities of Maltose in the Presence of Glucose. L. Grimbert. (Journ. Pharm. Chim., 1903, xvii., 225.)-The method of separation proposed by LQpine and Boulud (Comptes Rend. Xoc. Biol., December, 1901), which consisted in treating the osazones with ether, has not proved successful in the author's hands, since he has found that maltosazone is as insoluble in ether as glucosazone.He recommends, however, the following method as capable of detect- ing maltose in a 0.1 per cent. solution containing from 0.1 to 1 per cent. of glucose : Twenty C.C. of the solution containing the two sugars is treated with 1 C.C. of phsnyl- hydrazine and 1 C.C. of glacial acetic acid, and the whole heated on the water-bath for an hour, and then cooled. The mixed osazones are washed with cold water and dried, then washed with benzene until the washings are colourless, and dried at 100' C. They are then triturated in a mortar with the smallest possible amount of acetone diluted with its own volume of water, and, on allowing the filtrate to stand, crystals, with the characteristic form and melting-point (196" to 198" C.), are de- posited.Or the osazones may be heated in a minute amount of water for five minutes on the water-bath, and then rapidly filtered, leaving the glucosazone, which is much more insoluble in hot water, on the filter. C. A. M. Titration of Aniline Oil by means of Potassium Bromate. W. Schapo- schnikoff and B. Sachnowsky. (Zeits. Farben- u. Textil-Chemie, 1903, ii., 7 ; through Chem. Zeit. Rep., 1903,37.)-In Schaposchnikoff's modification of Reinhardt's process, a solution of aniline in hydrobromic acid, having the concentration of 1 gramme of aniline oil and 60 grammes of HBr per litre, is titrated with a solution containing 8 grftmmes of potassium bromate per litre. The present authors advise that the standard solution should be set by the aid of iodine, and not with aniline.With this alteration the procese gives figures within ~ 0 . 3 per cent. of the truth, provided the strength of the liquid is not departed from. F. H. L.152 THE ANALYST. Synthetical Mixed Glycerides of Fatty Acids. F. Guth. (Zeit. fiir Biol., xliv., 78 ; Biochem. Centralblatt., 1903, i., 181, 182.)-The author has prepared the mixed glyceride of various higher fatty acids by new methods. The mono- and di-glycerides of stearic, palmitic, oleic, butyric, and iso-butyric acids were obtained by the action of the sodium salts of the respective fatty acids upon monochlorhydrin, a-dichlorhydrin, and /3-dichlorhydrin. Triglycerides were prepared by heating the diglycerides with the corresponding fatty acids under strongly reduced pressure in a fractionating flask, and also by the action of tribromhydrin upon their sodium salts.A mixed glyceride of stearic and palmitic acids (and of other fatty acids) was obtained by heating the mixed mono- or di-glycerides with the fatty acids. Mixed glycerides of certain fatty and other acids were also obtained in an analogous manner. Contrary to the experience of Berthelot, the author found the melting-points of nearly all the glycerides higher than that of the original acids. Double melting- points were never observed with crystalline triglycerides. Since heat was found to be liberated at the moment of the first fusion, the author considers that there is not really a second melting-point, but that the phenomenon is to be attributed to the result of a sub-cooling (Unterkuhlung) of the melted substance which has not again become crystalline in solidifying (cf.ANALYST, xxiv., 185). C . A. M. Separation of Unsaturated Fatty Acids. K. Farnsteiner. (Zeit. fiir Under- such. der Nahr. urtd Genussnzittel, 1903, vi., 161-166.)-Principally a reply to Lewkowitsch’s statement (ANALYST, 1900,64-66) that barium oleate is not sufficiently insoluble in a mixture of benzene and alcohol (5 per cent.) to permit of quaqtitative results being obtained. The author now publishes the results of a number of experiments on the solubility of barium oleate in various solvents and on the quantitative separation of unsaturated fatty acids. These results confirm those previously obtained by him. The latter part of the paper is devoted to a discussion on the presence of other unsaturated fatty aoids, besides oleic, linolic, and linolenic, in animal fats.w. P. s. Iodine Absorption of Oils and Fats. L. ‘116. Tolman and L. S. Munson. (Journ. Amer. Chem. Soc., xxv., 244.)-The authors have examined the relative merits of Wijs’ solution (iodine chloride dissolved in glacial acetic acid) and that of Hanus (iodine bromide in glacial acetic acid solution) as compared with the ordinary Hub1 solution. The value of both the Wijs and Hanus solutions remains practically unchanged even on keeping for several months, and they are much quicker in their action, fifteen minutes being sufficient for the absorption in the case of non-drying oils, semi-dryings requiring thirty minutes, and drying oils one hour.On account of the ease with which it may be prepared, the authors prefer the- Hanus solution, which gives values slightly lower than those obtained with Wijs’ solution, but higher than the Hub1 numbers. It may be prepared by dissolving 13.2 grammes iodine in 1,000 C.C. glacial acetic acid (which must give no reduction with sulphuric acid and bichromate), and then adding enough bromine to double the halogen contents of the solution, about 3 C.C. being necessary. On account of the highTEE ANALYST. 153 Sub- ' Insol. in 1 Alcohol. -- 3 -- stance 1 Iodine Value. Saponification Value. q 1 . 2 . 3 . 4 . 1 . 2 . 3 . 4 . -------- 14-40 16-0 16.6 19'5 8.0 212-8221*2260*1 226.8 10.69 7-E 7-7 8-6 3.6 218'42242251'9224*0 3-10 22.2 22.6 23.3 19.0 204'4208'5 215.3212-8 0.93 ' 176.2 186.6 188-6 160.0/ 98'0 103.8 104.9 106.0 3.52 176.2 184.5 291.5 160.0 (100'8 105'5 109.5 106.0 0.88 175'0 183.0 184.7 160.0 156'8 164.0 165'5 176.4 5.26 1645 172.9 183-1 156.7 64'4 67-7 71.7 106.0 0'54 I 91.8 93.6 9 4 2 98.7 162'4 165.7 166.7 170.8 2.30 106.0 108.2 110.8 91-0 187.6 191.6 196.2 187.0 3-39 86'0 87.4 90-6 - 215'6219*3227*1 - 0.10 137.1 138.2 138.3 - 177.8 179'2 179.4 - 0.20 122.0 122.9 123.2 - 182'0 183.4 183.8 - - 1148.5 - - 1 - 121.8 - - - - 109.6 - - - 117.6 - - - 0.10 83.6 83*7* 83-81 - 28'0 28-0 28.0, - ~ - ~ ~ _ _ _ ~ _ _ _ _ _ coefficient of expansion of the glacial acetic acid solution a blank must be made for each set of determinations, as otherwise the error in measuring, due to change in temperature, may be sufficient to vitiate the results.A. G. L. Acid Value. fl . 1 . 2 . 3 . 4 . 39'2 40'7 47'9 56.0 53.0 54.5 61'1 56.0 58.8 60.0 61.9 64.0 82-3 87.1 88.1 64.0 67.2 70.3 73.0 67.0 72.8 76.1 76.8 84.0 18.5 19.4 20'6 25'0 137'2 140.0 140.8 137'8 136'6 139.5 142.8 150.0 138'9141.3146.3 - 169.7 171.0 171.2 - 157.9 159.1 159'4 - 73.9 - - - 103'0 - - - 22*4 22.4 22.4 - I Iodine, Saponific tion, and Acid Values of Certain Resins. A. Rudling. (Chem. Rev. Fett u. Hb a-Ind., 1903, x., 51-53.)-The analytical figures given in the subjoined table refer only to resins used in the spirit-varnish industry. In the numbers of the columns, 1 represents the crude resin ; 2,. the anhydrous substance ; 3, the anhydrous substance freed from mechanical impurities; and 4, the resin separated from a filtered alcoholic solution by means of steam and dried at 100" C.The iodine values were determined by dissolving the resins in a mixture of alcohol and chloroform, and titrating the excess of iodine after six hours ; the saponification values by boiling the resin with seminormal alkali for fifteen minutes, and then diluting the liquid with 100 C.C. of alcohol and titrating; and the acid values by boiling 1 gramme of resin for five minutes with 100 C.C. of 96 per cent. alcohol, and titrating the liquid after cooling. Stick lac ... ... Seed lac .. ... Button lac ... ... Yellow acaroid resin Ditto (Adelaide) ... Ditto (Victoria) ... Red acaroid resin . . . Sandarac ... ... Msnila (spirit sol- Ditto (hardj' ... White French resin American resin ... Venetian turpentine Elemi ...... uble) ... (genuine) . . . Ditto (spurious) . . . Resin. 3-79 2-63 2-00 5-65 4-50 4.40 4-90 2-00 2.10 1.68 0.80 0.75 - - 0.20 Water. -_ % Sitosterol : A Possible Test for Maize Oil. Augustus H. Gill and Charles G. Tufts. (Journ. Amr. Chem. SOC., xxv., 254.)-The authors show that maize oil contains sitosterol (Burian, Monatsh. Chem., xviii., 551), not cholesterol, as stated by Hoppe- Seyler and Hopkins, and give the melting-point of sitosterol as 1375", of the acetate as 124.5" to 127O, the benzoate 145" to 145*5", and the propionate 108.5". Cotton- seed oil contains phytosterol, but not sitosterol, and the authors propose basing a test for the detection of maize oil in cottonseed oil on this difference. For this purpose, 50 grammes of the oil to be examined were heated to boiling for twenty minutes under a reflux condenser with 100 C.C.of 95 per cent. alcohol. After154 THE ANALYST. allowing to stand overnight, the alcoholic layer was drawn off, boiled for fifteen minutes with 75 C.C. of seminormal alcoholic potash, and evaporated to dryness. The residue was dissolved in 40 to 50 C.C. water, and extracted with 75 C.C. ether and 3 C.C. alcohol, the extract washed repeatedly with water and evaporated to dryness. The yield of solid alcohol by this process was : From pure cottonseed oil, 0.095 per cent. ; from cottonseed oil containing 10 per cent. maize oil, 0.12 per cent. ; and from cottonseed oil containing 20 per cent. maize oil, 0,164 per cent. The crystals obtained were acetylated by boiling for one hour with excess of acetic anhydride, evaporating off the excess on a water-bath, and recrystallizing from alcohol.The melting-points of the acetates obtained were, after drying at 100" C . : From pure cottonseed oil, 120" to 1 2 1 O ; from 10 per cent. maize oil, 121%" to 122.5' ; from 20 per cent. maize oil, 124" to 125". By dissolving the acetates in just enough hot alcohol to effect solution and then suddenly cooling, a portion was obtained from the 20 per cent. maize oil, after recrystallizing four times, which gave a melting-point of 126' to 127O, the melting-point of the acetate from the 10 per cent. maize oil remaining unchanged. The crystals deposited by slow cooling from 95 per cent. alcohol were, in the case of the acetate from pure cottonseed oil, transparent flat needles, whilst the acetate from the 20 per cent.maize oil gave opaque white crystals of a more granular form. In using the above method for the detection of maize oil, the absence of linseed, rapeseed, and sesame oils must first be shown by the ordinary analytical constants, as these oils also give acetates of high melting-points. A. G. L. Estimation of Tarry Matter in Dark Cylinder Oils. D. Holde. (nfitteil. Kgl. Teckn. Vkrsuchsanst., Berlin, 1902, xx., 252 ; through Chem. Zeit. Rep., 1903, 71.)-About 5 grammes of the oil are dissolved in 25 times their volume of ether at 1 5 O C., and into the solution is slowly dropped 12.5 times its volume of 96 per cent. (by weight) alcohol, shaking continuously. After standing for five hours at the same temperature, the mixture is filtered, and the residue is washed with a mixture of one part of alcohol and two of ether till no more oily matter and only traces of tarry matter pass into the washings.The tarry matter separated is then dissolved in benzene, evaporated, dried for fifteen minutes at 105' C., and weighed when cold. F. H. L. A Method for determining the Index of Refraction of Solid Hydrocarbons with the Pulfrich Ref'ractometer. Charles F. Mabery and Lee Shepherd. (Amer. Chem. Journ., xxix., 274.)-In this method the cup containing the solid is heated to a constant temperature above the melting-point of the solid by means of electric currents passed through two coils of German-silver wire, one surrounding the cup and separated from it by a thin sheet of asbestos, whilst the other is placed in the cup itself, and serves to stir the melted substance as well as to heat it.I n this way a temperature of 100' C. may be readily obtained without breaking the joint between the cup and prism. It was found that if the solid hydrocarbon was melted directly on the prism, a thin film of solid persisted on the surface of the latter,THE ANALYST. 155 obstructing the passage of light, and consequently the method of mixtures had to be resorted to, a petroleum distillate boiling constantly at 202" to 203" under a pressure of 50 millimetres being used as solvent. I n this way the indices of refraction of a number of solid hydrocarbons were obtained. A. G. L. Determination of Ammonia in Urine and other Animal Fluids.0. Folin. (Zeits. Physiol. Chem., 1902, xxxvii., 161 ; through Chem. Z e d Rep., 1903, 36.)- Twenty-five C.C. of urine are measured into a glass cylinder about 45 centimetres tall and 5 centimetres in diameter ; 8 to 10 grammes of sodium chloride, 5 to 10 C.C. of petroleum or toluene, and 1 gramme of dry sodium carbonate are then added. A current of air is next passed through the mixture at a temperature of 20' or 25" C. for 1 or 1.5 hours at a speed of 600 or 700 litres per hour till all the pre-formed ammonia is volatilized. The evolved vapours are made to pass through a plug of cotton-wool, which retains any alkali carried over mechanically, and the ammonia is absorbed either in two receivers charged with dilute standard acid, or in one receiver constructed as described below.The acid is finally titrated, using such an indicator as alizarin red. Larger quantities of urine may be taken, but in this case the current of air must be continued for a longer period. For the analysis of blood, 50 C.C. are measured out, and the vessel is packed in ice; next, 16 grammes of sodium chloride, 25 C.C. of methyl alcohol, and 2 grammes of dry, or 5 grammes of crystallized, sodium carbonate are added, and the current of air passed as before for five hours. After about two hours, however, a further 25 C.C. of methyl alcohol must be introduced to prevent frothing. The receiver should contain only 10 C.C. of Tn acid together with some water, and for fifteen minutes just before, or preferably after, stopping the air current it should be stood in water at 30" or 35" C. to drive out any carbon dioxide. The blood should be as fresh as possible. One of the advantages of the method is that several tests can be carried out '' in series," using the same current of air for all. In this case double receivers are inconvenient, and the following device is better: A glass tube, 8 millimetres in diameter, has a bulb blown on it at one end, which is perforated with a number of small holes. By means of a rubber cork it is fastened inside a wider tube, the upper portion of a test-tube, 7-5 centimetres long and 2.5 centimetrss in diameter, this tube being provided with a row of small holes 3 centimetres above the level of the bulb. The whole arrangement is plunged into a vessel containing the standard acid, the ammoniacal vapours being led in through the innermost tube. In this way the air is forced to bubble twice through the liquid in the one apparatus, and the whole of the ammonia is recovered. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9032800150

出版商:RSC    

年代:1903

数据来源: RSC

摘要:

156 THE ANALYST. INORGANIC ANALYSIS. (Bey., 1903, xxxvi., 164 ; through Chent. Zed. Rep., 1903,54.)-If only ferrous salts are present, a known excess of standardized iodine solution is brought into a stoppered flask, a strong aqueous solution of about 5 grnmmes of sodium potassium tartrate is added, and then the neutral, or nearly neutral, ferrous solution. The vessel is tightly closed, kept for three to five hours in the dark at the laboratory temperature, and the excess of iodine is titrated with thiosulphate. The complete conversion of the iron into the ferric state may be confirmed by testing the titrated solution with ferricyanide. I n presence of both ferrous and ferric salts, another sample is treated with 5 or 10 C.C. of dilute sulphuric acid and with 1 per cent. permanganate till a permanent rose colour is produced.The excess is destroyed with a fragment of oxalic acid, the liquid diluted to 75 or 100 c.c., and then titrated by the Mohr process. Having by this second titration determined the total iron, and by the first the ferrous iron alone, the ferric iron is given by difference. Iodometry of Iron Salts. E. Rupp. F. H. L. The Separation and Determination of Manganese in Certain Products. E. Pozzi-Escot. (Ann. de Chiin. anal., 1903, viii., 88.)-It is frequently difficult to eliminate manganese completely from certain products-e.g., when acids of the aromatic series are present-precipitation with ammonia is incomplete, and neither chlorine nor bromine is inadmissible on account of the action of the halogen on the other compounds. In such cases the manganese can be completely separated in the form of peroxide by two treatments with hydrogen peroxide.Ammonium persulphate can also be used with good results for the oxidation and determination of manganese. C. A. M. Note on t h e Volumetric Estimation of Zinc. J. E. Clennell. (Chem. News, lxxxvii., 121.)-In the method proposed by the author, zinc is first precipitated by a slight excess of standard sodium sulphide solution, the excess of which is then removed, after filtration, by means of a solution of potassium silver cyanide, according to the equation : Na2S + ~ K A . A ~ ( C N ) ~ = Ag2S + 2NaCN + SKCN, the alkali cyanide formed being finally titrated in the filtered liquid with a standard silver nitrate solution, potassium iodide being used as indicator.The original solution of the zinc must be strongly alkaline, especially if it contains any ferrocyanide or thiocyanate. If cyanides are present in it, these may either be removed by adding excess of silver nitrate, and then hydrochloric acid, boiling, and filtering before adding the NazS solution, or else the cyanide may be determined with silver nitrate solution, and the amount found deducted from the quantity found by proceeding as above. The results obtained by the use of the method are satisfactory. A. G. L.THE ANALYST. 157 Volumetric Estimation of Cerium. A. Waegner and A. Muller. (Be?“., 1903, xxxvi., 282; through Chem. Zeit. Rep., 1903, 69.)-The authors find that commercial bismuth tetroxide dissolved in strong nitric acid quickly and quanti- tatively converts cerous into ceric compounds at ordinary temperatures, and they therefore propose the following method: 25 to 30 C.C.of the cerium solution are mixed in a 110 C.C. flask with an equal volume of strong nitric acid. When quite cold bismuth tetroxide is dropped in by degrees, with periodical agitation, using 2 to 2.5 grammes for every 0.1 gramme of Ce; then the liquid is allowed to rest for half an hour, filled up to the mark, and well shaken. After one or two hours’ standing the deep yellow solution is run through a dry, folded filter. One hundred C.C. of the filtrate are diluted with an equal volume of water, and standardized hydrogen peroxide is introduced from a burette till the liquid is completely decolorized, the small excess of the latter being finally titrated by means of permanganate.The results obtained agree well with those given by Von Knorre’s ammonium persulphate process. F. H. L. The Reduction of Vanadic Acid by the Action of Hydrochloric Acid F. A. Gooch and L. €3. Stookey. (Amel.. Journ. Sci., xiv., No. 83 ; through Chenz. News, lxxxvii., 133.)-The authors have investigated the accuracy of the method of determining vanadium pentoxide by reducing to tetroxide with hydrochloric acid and estimating the chlorine evolved, and find that when acid of 1-17 specific gravity is used the results obtained are about 92 per cent. of the V,O, actually present, acid of 1-19 specific gravity giving about 94 per cent. By cooling the residual eolution, saturating it with gaseous HC1, and repeating the distillation, higher values may be obtained, the test for complete reduction being the complete solution of the residue in the distillation-flask in concentrated acid to a clear blue liquid showing no brown or green tinge.The authors recommend the use of the method when only com- paratively small amounts of vanadium are being determined, especially if it is desired to titrate the reduced oxide with permanganate, in which case Holverscheit’s hydro- bromic acid method is inadmissible. A . G. L. A New Gravimetric and Gas-Volumetric Method of Determining Phos- phoric Acid and Magnesium. (Zeit. anal. (?hen%., 1902, xh., 675.)- Gravimetric Determination of Phosphoric Acid.-This is based upon the fact that an ammoniacal solution of ammonium phosphomolybdate yields a precipitate with barium chloride, and that this precipitate contains the whole of the phosphoric acid, and has a composition corresponding with the formula Ba,7(Mo0,),,P,0, + 24H,O. Even the smallest proportion of phosphoric acid yields a relatively very large barium precipitate, and it is advisable not to use more than 0.04 to 0.05 gramme of phos- phorus pentoxide for the determination.From 40 to 50 C.C. of the phosphate solution of about this strength axe treated with 5 C.C. of nitric acid (specific gravity 1*2), then heated to the boiling-point, and 50 C.C. of ammonium molybdate solution immediately added. After standing for two minutes the flask is closed, vigorously E. Riegler.158 THE ANALYST. shaken for two minutes, and then left a t the ordinary temperature for two houre, after which the precipitate is washed with about 50 C.C.of a 20 per cent. solution of ammonium nitrate and dissolved in 60 to 70 C.C. of 10 per cent. ammonium hydroxide. About 20 to 25 C.C. of 10 per cent. barium chloride solution are then introduced, and the mixture gently shaken and allowed to stand. The barium precipitate, which separates rapidly, is collected on a dried and weighed filter, washed with water, dried at 100" C., and weighed. I t s weight multiplied by the factor 0.0175 gives the amount of phosphorus pentoxide in grammes. In five test experiments the results agreed within 0.0001 gramme with the theoretical amount. The ammonium molybdate solution is prepared by dissolving 50 grammes of ammonium molybdate in 200 C.C.df 10 per cent. ammonium hydroxide, and pouring the solution little by little into 750 C.C. of nitric acid (specific gravity 1.2). Gas-Volumetric Determination of Phosphoric Acid.-The principle of this method depends upon the action of barium chloride on iodic acid, which yields barium iodate, and the liberation of nitrogen from the barium iodate through the action of hydrazine sulphate. Thus : 1. BaC1, + 2HI0, = 2HC1+ Ba(IO,),. 2. BaIO, + 3N,H,.H,SO, = BaSO, + 2H,SO, + 2HI + 6H,O + 6N. The solution of barium chloride contains 46.4585 of the pure crystalline salt in a litre, 1 C.C. corresponding with 1 milligramme of phosphorus pentoxide. Hence, since 6 atoms of nitrogen correspond with one of barium chloride in the above equations, and one molecule of phosphorus pentoxide corresponds with 27 atoms of barium (vide supra), it follows that 1 C.C.of nitrogen at 0" C. and 760 milli- metres' pressure corresponds with 0.078 milligramme of phosphorus pentoxide. The method is carried out in a similar manner to the author's other gas-volumetric methods (ANALYST, xxvii., 72, 340). Since barium iodate is not absolutely insoluble in water, an addition of 0.4 milligramme per 150 C.C. of filtrate and washings must be made to the amount of phosphorus pentoxide calculated from the nitrogen liberated. The formula for the calculation is P,O, = N - (V, x 0.08 + 0-4 milligramme), where N represents the number of C.C. of the barium chloride solution used, and V, the volume of nitrogen at standard temperature and pressure. Results obtained by this method agreed perfectly with the gravimetric results. Gravimetric Determiization of Magnesium.-The magnesium is precipitated as ammonium magnesium phosphate, and the precipitate washed with ammoniacal water until free from chlorine.It is next heated with 5 C.C. of concentrated nitric acid until the liquid begins to boil, when 50 C.C. of the molybdenum solution are introduced, and the barium compound precipitated and weighed as in the determina- tion of phosphoric acid. The weight of the dried precipitate, multiplied by the factor 0.0099, gives the corresponding amount of magnesium oxide (MgO). Gas- Volumetric Determination of Magnesium.--This is carried out in the same way &R in the case of phosphoric acid, with the following differences: (1) The barium chloride solution used contains 81.7284 grammes of the crystalline salt (BaCI, + H,O) per litre, 1 C.C.corresponding with 1 milligramme of magnesium oxide; (2) 1 C.C. of nitrogen at the standard temperature and pressure correspondsTHE ANALYST. 159 with 0.0445 milligramme of magnesium oxide ; and (3) the correction for solubility is 0-23 milligramme. The formula for the calculation is thus : MgO = N - (V,, x 0,0445 + 0.23) mg., where N represents the number of C.C. of barium chloride solution used, and V, the volume of nitrogen at Oo C. and 760 millimetres’ pressure. C. A. M. Determination of Phosphoric Acid in Thomas Meals containing Silica. 0. Bottcher. (Chem. Zeit., 1903, xxvii., 247.)-Since the publication of Kellner and Bottcher’s last article on this subject (this vol., p.50) the present author has examined some 200 samples of phosphate meal, obtained from different sources, some of which contained considerable quantities of silica, ; and he finds that whenever the original material exhibits the normal slate-gray colour, and whenever it yields the normal pale- green extract with Wagner’s citric acid, the proportiou of phosphoric acid in it, as found by the direct Bottcher process, is the same as that given by Wagner’s molybdate method, even when the Kellner and Biittcher preliminary test shows the amount of silica present to be large. Among the specimens investigated were five from one particular source, which gave large flocculent precipitates with the prelimi- nary test. The amount of phosphoric acid in them ranged from 18.92 to 19.62 per cent.when Wagner’s molybdate method was employed, from 19.40 to 19.96 per cent. by Weibull’s direct citrate method with ferric chloride (Chem. Zeit., 1902, xxvi., 297), and from 22.09 to 25.09 per cent. by the Bottcher process. But these samples had an abnormal pale-gray colour, and they yielded colourless Wagner extracts. Two of these samples, which gave 19-49 and 19.51 per cent. of phosphoric acid by Wagner’s method, 24.55 and 25.09 per cent. by the Bottcher process, and 19.61 and 19.50 per cent. by Weibull’s process, showed only 18.92 and 18.89 per cent. respectively when the silica was removed before precipitating with molybdate ; so that meals extremely rich in silica must have that ingredient thrown out even if Wagner’s method is to be adopted.With its preliminary test, however, the direct process is always much simpler and more rapid than any other, and it is far more convenient than the method pro- posed by Naumann (this vol., p. 123). If the qualitative test shows much silica to be present, the precipitation, agitation, and filtration in the Bottcher process must be carried out as quickly as possible. The figures quoted by the author show that the ferric chloride recommended by Weibull is not competent in all cases to insure the formation of precipitates free from silica. F. H. L. Determination of Citric Acid-Soluble Phosphoric Acid. R. Woy. (Chenz. Zeit., 1903, xxvii., 279.)-The following method of procedure is suitable for all varieties of Thomas meal. The sample is extracted with 2 per cent.citric acid as usual, and 50 C.C. of the liquid are mixed with 30 C.C. of 1.153 nitric acid (25 per cent.) and 45 C.C. of ammonium nitrate solution (340 grammes per litre). The whole is made to boil briskly and precipitated with 100 C.C. of a 6 per cent. solution of160 THE ANALYST. ammonium molybdate previously brought to the boiling-point. The reagent is poured into the middle of the liquid, the beaker being given a circular motion with the hand for about one minute, and then set aside for ten or fifteen minutes. When the heavy precipitate has subsided, the liquid is decanted through a Gooch crucible, and the residue is stirred up with 50 C.C. of ti washing solution (50 grammes of ammonium nitrate and 40 C.C. of nitric acid per litre), preferably used warm, also running it through the crucible after the lapse of five or ten minutes. The yellow precipitate is next dissolved in 10 C.C.of eight per cent. ammonia, treated with 30 C.C. of water, 20 C.C. of ammonium nitrate, and 1 C.C. of molybdate solution, boiled up, and precipi- tated with 20 C.C. of nitric acid which is conveniently dropped in quickly froin a stoppered funnel. The phospho-molybdate is collected in the same Gooch crucible, the beaker and the filter being washed once with the previously mentioned washing solu- tion, and then with half a crucible full of alcohol and of ether, using the pump to extract the various liquids. The precipitate is ignited as already described (ANALYST, 1897, xxii., 250) and weighed. If, as Passon has suggested, a special pipette, holding 39-47 c.c., is used to measure the original solution, the weight of phospho-molybdic anhydride obtained multiplied by ten gives the amount of P,O, in the material.If it is preferred to use the magnesia process, the Gooch crucible is replaced by a filter-paper, from which the small quantity of yellow precipitate ’is recovered by means of ammonia, allowing the liquid to run into the beaker still containing the bulk. If the process described is followed, silica is not thrown down by the phosphoric acid. The nitric acid filtrate sometimes yields a yellow precipitate on standing for fifteen minutes, which is a compound of silica and molybdenum ; but this is distinguished from the ammonium phospho-molybdate by adhering strongly to the glass, by only dissolving with difficulty in ammonia, and by not being thrown out of its ammoniacal solution on addition of ammonium nitrate and nitric acid.The method is said to be very simple and correct, and to be specially convenient when a number of analyses have to be conducted simultaneously. [It will be seen that; certain changes hare been introduced into the process since the author’s former paper (Zoc. cit.).-F. H. L.] The solution so obtained is precipitated with magnesia mixture as usual. F. H. L. Methods for the Estimation of Ozone. A. Ladenburg. (Ber., 1903, xxxvi., 115; through Cherrb. Zeit. Rep,, 1903, 53.)--8s the author has previously shown, ozone can be estimated by the potassium iodide method, provided it is led into a neutral liquid which is acidified just before titration. Fairly satisfactory, but less accurate, results may be obtained by the use of sodium sulphite. Solutions of the latter salt are not changed by oxygen, but they extract ozone from any gas con- taining it if led through very slowly, and if the liquid is sufficiently concentrated. The excess of sulphite may be titrated by Volhard’s iodine method. The author has tried Soret’s process, using a & solution of arsenious acid, prepared by solution in potassium hydroxide, acidification with dilute hydrochloric acid, and supersaturation with potassium bicarbonate. Even if the ozone is highly diluted, the method givesTHE ANALYST. 161 inaccurate and irregular figures, which become less trustworthy as the gas is more concentrated. From his experiments, Ladenburg concludes that ozone generally produces effects in proportion to the quantity present, its catalytic action being only noticeable on rare occasions. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9032800156

出版商:RSC    

年代:1903

数据来源: RSC

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THE ANALYST. 161 APPARATUS. (Chem. Zeit., 1903, XXVii., 69.) -The burette shown in Fig. 1 is filled by opening the cock f, and forcing air into the WolfT's bottle through i. When the burette is nearly full, f is closed, liquid still rising through d till the vessel is full. The surplus pressure is next let off, the burette then emptying itself through the short leg of d till the zero-point is set auto- matically. After titration, the burette may be com- pletely emptied by opening f again. The cap c protects the reagent from the air. Burettes of less than 25 C.C. capacity do not need the metal support k. The pipette shown in Fig. 2 works on a, similar principle, but the ascending tubef is closed at the point e. The pipette is filled as before, by compressing the rubber ball, liquid first ascending and then syphoning back till the zero-point is obtained. When the cock tZ is opened, a strictly constant volume of liquid escapes. For factory purposes the pipette may be made longer and graduated, so that by altering the length of the tube c, the quantity of liquid running out may be set to any desired amount.F. H. L Self-setting Burettes and Pipettes. C. Zahn.162 THE ANALYST. ,THE ANALYST. 163 An Improved Apparatus for Gas Analysis. W. H. Sodeau. (JozLY?~. SOC. Chem. Ind., 1903, iv., 187.)--The author has endeavoured to modify Macfarlane and Caldwell’s apparatus so that it would be adapted for gas analysis of the highest accuracy. In doing this so many additions and alterations have been made that little of the original arrangement remains.The measuring tube M (see diagram on opposite page) is entirely immersed in a water-bath, and is connected, as shown, to the level-tube L, the lower end of which passes through the bottom of the bath, where it is joined by a piece of rubber tubing to a T-piece. One branch of this T-piece is fitted with a stop-cock, and is connected with the mercury reservoir, which is provided with a counterpoise and is so arranged that it can be easily manipulated with one hand. The other limb stretches across the table to a point near the reading telescope, which is not shown in the figure. Here it is connected with a short length of rubber tubing, which can be more or less compressed by means of a screw clip. The scale of the measuring tube is illuminated by means of a screen and a small electric lamp sliding on the rod P.PVhen a reading is to be taken, the stop-cock at the top of L is opened, the rough adjustment is made by means of the reservoir, which is then shut off, and the fine adjustment is made by the pinch-cock near the reading telescope. To ascertain tha correction to be applied for variations of temperature and pressure taking place during the course of the analysis, the tube C is provided. The lower part of this is graduated, and a small quantity of water is placed in it. The stop-cock of C is opened, and closed again at the commencement of the analysis. The reading is taken with the aid of the lens travelling on the rod R, and the correction to be applied is then obtained from a table that is calculated once for all.The pipettes for absorbents are of the form shown, and are mounted on wooden stands which slide in grooves on the stool provided. The bulb E contains about 20 C.C. of absorbent confined over mercury. By means of the 3-way cock H, either of these bulbs can be put in connection with the capillary tube G. Similarly, the capillary tube K is connected through the 3-way cock N with either the measuring tube M or the U-tube U, which contains a little water standing over mercury. Before transferring the gas from M into E, a little water is sucked from U into F, and is then allowed to run back, followed by a little mercury. The gas is then passed from M into E, followed by a little mercury. When absorption has been completed by shaking the bulbs from side to side, a little mercury is passed over.That remaining in the capillaries is passed into U, then the cock N is turned, and the gas is returned to M. The bulb F contains mercury. In this way the capillaries are washed out and filled with mercury. A. M. A Laboratory Steelyard. F. Mach. (Chem. Zed., 1903, xxvii., 249.)-The author has extended the principle of his unequal-armed weighing-out balance already described (ANALYST, 1902, xxvii., 134), SO as to render it more suitable for all classes of technical analysis. It now stands ‘‘ side-on ” in the case, and the substance-pan is provided with a, separate arresting gear, worked, by the finger, which is capable of coming into action even when the pan is high. If fractions of a milligramme may be neglected, the apparatus will be found convenient and rapid to use.F. H. L.164 THE ANALYST. A Platinum Crucible for Carbon Combustions. John V. R. Stehman. (Jourcn. Amer. Chem. Soc., xxv., 237.)-The apparatus shown in the accompanying figure consists of a water-cooled brass cup ( A ) , having two tubes brazed through its bottom and provided with a water outlet, the cup-casing (B), into which the cup is screwed, and the platinum crucible (C), the joint between the flange of C and the casing (B) being made tight by the asbestos washer (d), which is made out of a piece of wick yarn wetted before being placed in position, the excess of moisture being squeezed out by first screwing down the cup before introducing the crucible. If water is supplied to d at the rate of 120 C.C. per minute, the washer is kept moist enough to be per- fectly tight, and a large number of deter- minations may be made without disturb- ing it.The brass cup and casing are protected from the flame during a deter- mination by passing the crucible through an annular sheet of asbestos, about 1 inch of the crucible being heated to redness. The dried plug of asbestos, on which the carbon was filtered, is introduced into the crucible carbon downwards, a platinuni disc being preferably first placed on the bottom of the crucible and another one on top of the plug to confine the heat. The air used for the combustion is purified by means of potash, and the exit gases are led first thr ugh a brass tube 12 inches long and 3 inch in diameter, containing copper oxide heated to redness, the ends of the tube being water-cooled; then through tubes in which C1, HC1, and H,O are absorbed; and finally into the GO, absorption bulbs.The author allows fifteen minutes for combustion and fifteen for aspiration, supplying air at the rate of four bubbles per second during the first part, and of five bubbles per second during the latter part of the operation. A. G. L. A Simplified Apparatus for Testing for Fluorine. H. Kreis. (Chem. Zed., 1903, xxvii., 281.)-Instead of allowing the vapours of hydrofluoric acid to attack a piece of glass which has been partially protected by a coating of wax or the like, and which has to be kept cool, the author suggests placing over the platinum crucibleTHE ANALYST. 165 containing the fluoride and the sulphuric acid, a lead basin about 2 millimetres thick with a hole 0.5 or 1 centimetre in diameter in its centre. In this basin, and above the hole, is laid a piece of glass, say a microscope slide, when the etching of the surface is as conspicuous as in the ordinary test. Moreover, as the vapours always attack an equal area of glass, the test thus becomes approximately quantitative. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9032800161

出版商:RSC    

年代:1903

数据来源: RSC

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THE ANALYST. 165 HIGH COURT DECISION IN A CASE UNDER THE SALE OF FOOD AND DRUGS ACTS. THE following judgment, given by the Divisional Court of the High Court of Justice on Thursday, March 26, in the case of Hudson v. Bridge, is taken from the Clwmist and Drzlggbt of April 4, 1903. The appeal was against a conviction under the Sale of Food and Drugs Acts in respect to the sale of vinegar of squills alleged to be deficient in acetic acid as required by the British Pharmacopceia. The LORD CHIEF JUSTICE said that there were in substance two questions raised to this conviction. He said two, because the two questions really raised the same issue in a different shape. The first one was whether the Justices were right in holding that the certificate of the analyst was valid and sufficient.He dealt with that first because, although he did not think it was absolutely necessary to decide that point in this case, the discussion they had had had brought out in relief the importance of the certificate and the importance of the directions with regard to the certificate being complied with. The statute [1875] by Section 20 provided that, when the analyst had analysed an article and given his certificate of the result (from which certificate it might appear that an offence against some one of the provisions of the Act had been Committed), he should report whether the article was liable to decomposition. He rather thought that in one of the cases to which Mr. Avory called attention he did say that at least that condition must be fulfilled. If he said so, he adhered to it ; and, if he did not say so, he said it now.The objection to this certificate was that the analyst did not comply with a mandatory direction contained in the schedule. The section said that the certificate of the analyst should be in the form set forth in the schedule, or to the like effect. Then there were directions as to percentage. Then came this-that in the case of a certificate regarding milk, butter, or any article liable to decomposition, the analyst shall specially report whether any change has taken place in the composition of the article which would interfere with the analysis. This certificate said nothing about the article being liable to decomposition, and contained no statement that a change had taken place which would interfere with the analysis.I t was said that defect in the Certificate was cured by the presence of the analyst and his examination in court. Although he did not think it necessary finally to decide that point, he was by no means satisfied such a defect could be so cured. He wished to express his own opinion that it was estremelyimportant in all cases in which the article was liable to decomposition that that direction should be fulfilled. I t was a statutory condition of the prosecution that a certificate should be given showing that an offence had been committed. If the article was one in which decomposition could have any bearing on the offence, in his opinion that direction ought t o be fulfilled. He abstained from expressing any opinion whether in cases in which decomposition might affect the condition of the article from the point of view of an offence having been committed, the absence of that state- ment could be cured by evidence given.He thought that in all cases in which it was shown that the analyst was of opinion that decomposition might affect the result of the analysis, he166 THE ANALYST, ought to comply with it. He did not wish to go further in this case, because he thought the second objection was a fatal one. The second objection was raised in this way : whether the magistrates were right in holding on the facts that there was no standard for the percentage of acetic acid to be present in vinegar of squills, and whether they were right in holding that there was a sale to the prejudice of the purchaser.They had prefaced that by a finding that, having regard to the extent of the deficiency of acetic acid, howsoever arising, the drug was not composed of the ingredients in such proportions as demanded by the purchaser, and that the sale was accordingly to his prejudice, and it was not material to consider whether the medicinal properties of the drug were affected. That would amount to this-they came to the conclusion that it was immaterial to consider whether or not there was less acetic acid in the article as sold to the purchaser than the purchaser would have required if he had known the drug had been kept, or if he had known that circumstances might have reduced the quantity of acetic acid, because if made in the way described in the B.P. it would have considerably more acetic acid than this would have.I t was agreed the article, as stated in the B.P., which was the standard relied on, if made in a particular way, would originally have a certain amount of acetic acid in it. I t was also agreed there was no direction in the B.P. that the vinegar of squills would have, when it was kept, a given amount of acetic acid. I t was not a statement to be found in the B.P., nor to his mind was it the fact, that a purchaser when he asked for vinegar of quills wanted acetic acid, or knew anything about the amount. Therefore it seemed to him that that which the magistrates had excluded from their consideration--namely, the materiality of the presence of that element in the vinegar of squills-was a matter which they certainly ought to have considered.One might state it in another way : Say that vinegar of squills, properly made, might contain 4.8 per cent. of acetic acid, and that vinegar of squills properly kept would, by the internal action of the drugitself, go through some change which would reduce the acetic acid, but still, from the point of view of the drug, it would be none the worse. That was a possible hypothesis which was excluded from consideration by the decision of the tribunal. He was, therefore, of opinion that there was not any material evidence that the purohaser had demanded, in asking for vinegar of squills, the proportion of acetic acid which would be present in new vinegar of squills, but which would be, or might be, absent from perfectly properly made vinegar of squills which had been properly kept for some time.Therefore this conviction could not be suppwed, because the hypothetical standard which the Bench had set up for the purpose of considering whether an offence had been committed was not the standard which ought to be set up in favour of a man who asked to be supplied with vinegar of squills. What he had endeavoured to make clear with regard to this point brought out in relief how important in some cases the certificate as to the result of the decomposition might be. He was of opinion, certainly on the second ground, that the conviction could not be supported, and if it had been necessary to deal with the first ground, he was by no means certain that there would not be a serious objection to this proceeding.Mr. JUSTICE WILLS said he agreed entirely with the judgment of the LordChief Justice. He only wished to add that the certificate was made by Act of Parliament a document of very great importance, to which consequences were attached by the Act of Parliament which would not naturally attach to it. Under these circumstances it was of great importance that the certificate should comply in all respects with the Act of Parliament. The analyst knew perfectly well whether a substance was liable to spontaneous decomposition or whether it was not. In this case it was so. Under these circumstances he thought the analyst was bound to fulfil the obligation imposed by the last clause in the schedule of the Act. The certificate of the analyst was made a condition precedent to any prosecution, and it ought to be properly certified.He did not think that was done if the analyst, knowing a subject was liable to decomposition, failed to m&e that clear. The analyst had to make a statement, one way or the other, on whichTHE ANALYST. 167 would depend the question whether any offence was or was not committed. On the second point he entirely agreed with what the Lord Chief Justice had said. He did not think it was necessary to give a judgment on Mr. Compton Smith’s point that the objection to the certificate was one which possibly might have been waived and cured by the fact that parole evidence was in fact given by the analyst himself on the point. It was not necessary to say whether that was a good point or not, having regard to their viewe on the second point.I n his view the magistrates misconstrued the words of the note upon this matter contained in the schedule of the Act of Parliament. That note was that in the case of a certificate regarding milk, butter, or any such article liable to decomposition, the analyst should specially report whether any change had taken place in the constitution of the article that would interfere with the analysis. He did not think ‘‘ interfere with the analysis ” meant, as the magistrates seemed to have thought, prevent the possibility of accurately analysing the substance as it existed at the time of the attempted analysis. They said that the decomposition to which vinegar of squills was liable was of such a nature as to render the article incapable of accurate analysis He thought “ interfere with the analysis ” meant prevent the analysis being effective for the purpose of showing what the constitution of the article was at the time of the sale. Where the article was an article which varied in its COIE- position, so that at one time it would contain more of a particular ingredient than another, then the analyst ought in his certificaie to state that no change had taken place at the time of his analysis which would prevent it showing what the condition of the substance was when it was sold. The result of that was the analyst here did not give a proper certificate, and undoubtedly if it had been the sole evidence it would be a h t a l objection. He did not give any evidence on the point whether it was a defect of a character which might be cured by supplementing it with parole evidence. On the other point he had nothing to add. Mr. JUSTICE CHANNELL said he agreed with the judgments delivered. That was what the magistrates said. The appeal was accordingly allowed.

ISSN:0003-2654    

DOI:10.1039/AN9032800165

出版商:RSC    

年代:1903

数据来源: RSC

摘要:

THE ANALYST. 167 REVIEWS. A SHORT MANUAL OF INORGANIC CHEMISTRY. By Messrs. DUPRE and HAKE. Third edition (reissue). Pp. 391. Price 6s. net. This is a reissue, at a lower price, of the work published and reviewed in the QNALYST, xxvi. 196. We can only add that the work is specially adapted for the use of medical and other students where chemistry forms only a small part of the course of studies. One-fourth of the book is devoted to General and Physioal Chemistry, and the remainder chiefly to typical elements, special attention being given to the relations between the members of each group. With such a vast field treated in a limited compass many important things must be very briefly referred to. Thus the modern theories of solution occupy about half a page. Room is made, however, for an account of Kundt’s experiment for determining the relative velocity of sound in gases, of importance as affording an independent met hod of determining their molecular formulE.We notice that P,O, is given as the formula for phosphoric anhydride, whereas in 1896 Messrs. Tilden and Barnett showed that it is more correctly P,Ol0 (Journ. Chem. SOC., 1896, p. 154). Perhaps the authors may bear this in mind in a subse- quent edition, which we hope may soon be required. T. F.168 THE ANALYST. SUGGESTED STANDARDS OF PURITY FOR FOODS AND DRUGS. BY C. G. MOOR, Mr. Moor has attempted in this book to bring together all the evidence possible which will throw light on the usual ‘‘ constants ” of drugs and foods. The preface most clearly sets forth the purpose of the book, and the author has certainly shown how important it is to have such a collection of results as his book contains for reference.The figures given are not intended or wished to be regarded as definite standards of purity, but rather as an extension of the principles which have long been in use in regard to other cases, such as milk and butter, to a very large number of official and non-official substances. I t is the wish of the author that these figures be regarded as ‘I tentative only,” and yet, on closely looking into the large number of suggested limits, one is struck with the extreme care which has been taken to lay down as correct a limit as possible. As the work started by Mr. Moor grows-as it must do-the suggested limits will obviously alter from time to time, but this cannot detract from the value of the book, which consists not so much of expressions of personal opinion of the author as a careful collection of the most reliable data obtained by well-known observers, conveniently arranged for reference.Whatever views may be held with regard to the general adoption of standards by analysts, it is abundantly clear that some such principle determines the inter- pretation of nearly all figures obtained by the analyst ; and such a collection of data as is to be found in the book must prove of great value. Foods and drugs would appear to be better treated under two headings, so as to avoid the juxta- position of exceedingly dissimilar substances, which must always occur when such an alphabetical order is adopted. There are very few mistakes noted : one, obviously overlooked, in the footnote of P. 97, and dealing with citrate of iron and quinine, and a misprint on p. 190, where the solids-not-fat in milk is given as 8.53, which is obviously an error for 8.5. The main feature of the book deals with the data obtained in official drugs and their preparations, and no other publication has embodied so much useful information on this subject. As might be expected, there are many instances where the figures obtained show large variations, and where it is clearly necessary, as pointed out by the author, that M.A., F.I.C. (London : BailliBre, Tindall, and Cox. Price 7s. 6d.). The leading fault of the work appears to be in its arrangement. fuller investigations be undertaken. w. c. .

ISSN:0003-2654    

DOI:10.1039/AN9032800167

出版商:RSC    

年代:1903

数据来源: RSC