摘要:

REPORT. In view of prosecutions which may be raised under this clause, it is desirable that an agreement should be come to among analysts as to the method and the analytical criteria which should be employed to raise a presumption, until the contrary is proved, that the amount of butter-fat in margarine exceeds the statutory limit.3 10 TEE ANALYST. On the suggestion of the Principal Chemist of the Government Laboratory, a Committee of the Council of the Society of Public Analysts was appointed to confer with him on this subject. After a careful examination of methods of analysis and a series of determinations, made independently, of various samples of commercial margarine of known composi- tion, and of mixtures prepared in the Government Laboratory of margarine with varying but known proportions of butter-fat of different Reichert-Wollny values, it has been agreed to recommend : (1) That the proportion of butter-fat should be deduced from a determination of the amount of the volatile acids,” as ascertained by the Wollny modification of the Reichert-Meissl process, described below.(2) That no presumption against the margarine in regard to its content of butter-fat should be raised unless the Reichert-Wollny number as ascertained by the method described exceeds 4. (3) That the amount of butter-fat in margarine, when it exceeds the legal limit of 10 per cent., as determined by the method prescribed, shall be assumed to be as follows : Reichert- Wollny Number of the Mixture. 4.0 ... 4.3 ... 4.6 ... 4.9 ... 5-2 ... 5.5 ... 5.9 ... 6.2 ...6.5 ... 6.8 ... 7.1 ... Percentage of Butter-Fat present in the Mixture. ... ... ... 10 ... . . . ... 11 ... ... ... 12 ... ... ... 13 ... ... ... 14 ... ... ... 15 ... ... ... 16 ... ... ... 17 ... ... ... 18 ... ... ... 19 ... ... ... 20 The foregoing table is to be regarded as applicable only to the determination of butter-fat in margarine. (Signed) T. E. THORPE, W. W. FISHER, A. H. ALLEK, E. J. BEVAN, 0. HEHNER. THE REICHEItT-WOLLNY METHOD FOR DETERMINATION OF VOLATILE FATTY ACIDS IN MARGARINE AND BUTTER. Five grammes of the liquid fat are introduced into a 300 C.C. flask, of the form seen in the figure (length of neck 7 to 8 centimetres, width of neck 2 centimetres). Two C.C. of a solution of caustic soda (98 per cent.) in an equal weight of water -preserved from the action of atmospheric carbonic acid-and 10 C.C.of alcohol (about 92 per cent.) are added, and the mixture is heated under a reflux con- denser, connected with the flask by a T-piece, for fifteen minutes in a bath containingTHE ANALYST. 311 boiling water. The alcohol is distilled off by heating the flask on the water-bath for about half an hour, or until the soap is dry. One hundred C.C. of hot water which have been kept boiling for at least ten minutes are added, and the flask heated until the soap is dissolved. Forty C.C. of normal sulphuric acid and three or four fragments of pumice or broken pipe-stems are added, and the flask is at once connected with a condenser by means of a glass tube 7 millimetres wide and 15 centi- metres from the top of the cork to the bend, At a distance of 5 centimetres above the cork is a bulb 5 centimetres in diameter.The flask is supported on a, circular piece of asbestos 12 centimetres in diameter, having a hole in the centre 5 centimetres in diameter, and is first heated by a very small flame, to fuse the in- soluble fatty acids, but the heat must not be sufficient to cause the liquid to boil- The heat is increased, and when fusion is complete 110 C.C. are distilled off into a graduated flask, the distillation lasting about thirty minutes (say from twenty-eight to thirty-two minutes), the distillate is shaken, 100 C.C. filtered off, transferred to a beaker, 0-5 C.C. of phenolphthalein solution (1 gramrne in 100 C.C. alcohol) added, and the filtrate titrated with decinormal soda or baryta solution.Precisely the same procedure (with the same reagents), omitting the fat, should be followed, and the amount of decinormal alkali required to neutralize the distillate ascertained. This should not exceed 0.3 C.C. The volume of decinormal solution of alkali used, less the figure obtained by blank experiment, is multiplied by 1.1. The number so obtained is the ‘‘ Reichert-Wollny Number.”312 THE ANALYST. Notes on the Method-The sample is melted and filtered from curd and water through a dry filter. From the filtrate the 5 grammes of fat for the process a m taken. The soda solution is filtered clear from carbonate formed in its preparation, and kept in a special bottle. The Soxhlet spherical condenser is a convenient one for the reflux distillation.This is fixed near the water-bath in which the saponifica- tion is to take place, and is connected with the flask by means of a T-piece and indiarubber tubes inclined at an angle of 45". During the saponification the free limb of the T-piece is directed upwards, and its end closed by a short piece of india- rubber and glass rod. At the end of fifteen minutes this limb is turned downward, and the piece of glass rod replaced by a tube carrying away the alcohol. One hundred C.C. of hot distilled water are added, and the flask frequently shaken until the soap is dissolved. One con- taining a column of water 30 to 35 centirnetres in length gives sufficient condensing surface. After shaking the distillate, about 5 C.C. are filtered through a dry paper into a 100 C.C.flask. This serves to wash out the flask. When the 100 C.C. are transferred to a beaker, the flask is not washed out, but the main quantity is neutralized with the standard solution of alkali and returned to the flask, then again transferred to the beaker and the titration completed. The Liebig is a convenient form of condenser. The PRESIDENT then said that some explanation might be given of the adoption of a Reichert-Wollny number of 4 as representing 10 per cent. of butter-fat. Ten per cent. of butter-fat, if the butter had a Reichert-Wollny number of 30, would be represented by a Reichert-Wollny number of 3. The margarine itself, however, must always count for something, and the traces of volatile acids which it would probably contain might raise the number 3 to 3.5 or 3.7 ; so that, by way of margin to avoid disputes about very small proportions of butter-fat, which, after all, were immaterial, the number 4 was adopted, as being a whole number and more satisfactory than 3.85 or 3.9 would be, and giving the same practical results.The appendix to the report contained a description of the method of analysis, with a diagram of the apparatus. The apparatus should be constructed in accord- ance with the measurements given, in order that the results might not be affected by minor differences of procedure. Dr. RIDEAL said that this report was especially to be welcomed because it marked a new and satisfactory departure in the history of the Society and its relations with the Government Laboratory.The method described was practically the one which he had been in the habit of using for some years past. He would be quite prepared, and he hoped that every public analyst would be prepared, to adhere rigidly to all the details of the method as now laid down, because he believed that only by so doing could uniformity of results be secured ; and from personal experience he was sure that its employment would lead to the avoidance of many disputes. He had much pleasure in moving that the Society formally adopt this method as an official method. He agreed that the action which had been taken by the Society in this matter was one of considerable importance, and it was desirable that action of a similar kind should be taken in regard to other products. Major CASSAL seconded the motion.THE ANALYST.313 The adoption of an official process was necessarily a matter of compromise under certain circumstances, and it would appear that the labours of the Committee had resulted in the adoption of a process which was satisfactory to both parties con- cerned. It was obviously important that in this, as in other matters, the Society should be in agreement with the Somerset House analysts, who had met the Society in a fair and proper spirit, which he had no doubt whatever would also be exhibited by them in the future in regard to any other questions that might arise. Mr. EMBREY supported the motion, on the ground that it was quite as important that public analysts should agree amongst themselves as that they should agree with the Government chemists. There were, he thought, points in the method recom- mended which were open to criticism, but he nevertheless would be prepared to adhere to it, seeing that it had been agreed upon. The motion, on being put to the meeting by the President, was carried unani- mously. A certificate of proposal for election to membership in favour of Mr. John Stewart Remington was read for the second time. Certificates in favour of Messrs. Percy Henry Carpenter, 46, Streathbourne Road, Upper Tooting, S. W., assistant to Mr. Alfred C. Chapman; and Samuel Russell Trotman, M.A., F.I.C., 1, Waverley Street, Nottingham, Public Analyst for the City of Nottingham, were read for the first time. The following papers were read : (‘ The Determination of the Available Brewing Extract of Malt,” by Lawrence Briant; and ‘( Notes on certain B. P. Tests,” by C. G. Moor, M.A., and Martin Priest.

ISSN:0003-2654    

DOI:10.1039/AN900250309b

出版商:RSC    

年代:1900

数据来源: RSC

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THE ANALYST. 313 A NEW COLOUR REACTION FOR DISTINGUISHING BETWEEN CERTAIN ISOMERIC ALLYL AND PROPENYL PHENOLS. BY ALFRED C. CHAPMAN, F.I.C. (Read at the Meeting, June 6 , 1900.) MANY of the odoriferous constituents of essential oils are now known to consist of phenols or their simple derivatives, and some of these are of considerable technical importance, chiefly owing to the fact that they serve as the starting-points in the manufacture of certain well-known artificial perfumes. Thus, eugenol and safrol serve respectively for the preparation of the important perfumes vanillin and heliotropin. Many of these phenolic substances inay be grouped in pairs, the one isomer containing the ally1 grouping CH,. CH : CH,, whilst the other has instead the propenyl group, CH : CH . CH,, and the conversion of the former into the latter can, as a rule, be effected without difficulty.In some cases, as, for instance, eugenol and safrol and their isomers, the general properties of the pair of compounds are so much alike that a simple colour reaction capable of distinguishing clearly and easily between them is of sufficient interest, I think, to warrant me in bringing it before the notice of the Society. The reaction in question is brought albout by simply dissolving 1 C.C. of the314 THE ANALYST. phenol in 5 C.C. of acetic anhydride, and then adding (a) a fragment of fused zinc chloride or ( b ) 1 drop of concentrated sulphuric acid. Experiments were made with the six substances, eugenol and iso-eugenol, safrol and iso-safrol, and estragol and anethol, and the colour changes recorded below were observed : 11, s 0,.ZnC1,. II,SO,. ZnC1,. II,SO,. ZnC1,. EUGENOL. Brown at first, becoming quickly Pale yellow, the colour disappearing SAFl1OL. A bright emerald-green colour, be- coming brownish-green and finally brownish. Pale blue, becoming less intense on standing, and finally light brown. E s TH A ( ; o L . Purple, turning to indigo blue, and then to bluish purple. Hue-violet colour, which becomes deep mauve and finally brownish. purple, and finally wine-red. on standing. TSO-EUGEXOL. -4 rose pink, quickly changing to a Bright rose-pink coloration. light brown. ISO- SAFROL. A faint transient pink, becoming reddish on standing. Pink, becoming brownish-pink and AKETHOL. No colour at first. After a short time a yellowish tinge.A pale yellow colour appearing slowly, which deepens on standing, and finally becomes brick-red. finally brown. Seeing that colour reactions are so largely influenced by the presence of impurity in the compounds to which they apply, I may add that no pains were spared to obtain the above substances in as pure a condition as possible. Some of them (eugenol, iso-eugenol and iso-safrol) were prepared in my laboratory, whilst the remaining three were procured from Kahlbaum of Berlin, and purified by me. I n all cases the chief physical constants were carefully determined and compared with those given by the most reliable authorities, and when possible crystalline derivatives were prepared from them aud identified. There can, therefore, I think, be no reasonable doubt that all were in as high a degree of purity as it is possilde to obtain them. DISCUSSIOX. Dr. LE:\VKO\VITSCII said that, in the case of the so-called colophony test, a more distinct reaction was obtained with sulphuric acid of specific gravity 1.53 than with an acid of greater strength; and perhaps in the case of the test now described a somewhat weaker acid would give a more strongly developed coloration, as seemed to be shown by the zinc chloride. Mr. A. MARSHALL inquired whether any other dehydrating agents had been tried. Mr. CHAPMAN said that the treatment, of these hydroxy-compounds in the manner described was the ordinary method of preparing acetyl derivatives, and his attention had been quite accidentally directed to the reaction in that way. The investigation had not been carried any further, but he thought that the test as it stood would probably suffice for ordinary purposes.

ISSN:0003-2654    

DOI:10.1039/AN9002500313

出版商:RSC    

年代:1900

数据来源: RSC

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THE ANALYST. 315 DETECTION OF MAIZE I N WHEA4TEN FLOUR. BY G. EMIRREY. (Read at the Meeting, June 6, 1900.) DURING the past three or four years English millers have been seriously affected by the introduction of foreign wheaten flour, containing from 10 to 30 per cent. of maize flour ; and yet very few prosecutions of dealers selling such have taken place. Many fancy articles sold, as ‘‘ Self-raising Flour ” and ‘‘ Pastry Flour,” have also been found to contain from 10 to 20 per cent. of maize. I have examined the published methods for detecting and estimating this substance, but find the results are not so constant as is desirable for proceedings under the Food and Drugs Act. If we compare the flours separately as regards their chemical composition, we fail to discover variations sufficiently wide to enable us to estimate one in the presence of the other.At one time I thought it possible to make use of the difference in the aniount of fat found in the flours ; but although the whole-grain of maize contains nearly 5 per cent. of fat, the samples of white maize flour on the market contain only 2.84 per cent. of fat, while wheat flour contains from 1.2 to 2 per cent. of fat. There is some difference in the amount and in the character of the mineral matter. Thus, while maize contains 0.714 per cent. ash, nearly 60 per cent. of which is soluble in water, and which has 38.65 per cent. phosphates, calculated as tricalcium phosphate, wheat flour has usually only 0.42 per cent. of ash, 71 per cent. of which is soluble in water, 22.42 per cent. of the ash being phosphates; so the examination of the ash may be used to confirm the other methods of estimation.I believe the usual method of detecting maize in presence of other flours is by means of the microscope ; and the mode described by Allen, aided by the excellent drawing (facing page 411, ‘‘ Commercial Organic Analysis,” vol. i., third edition), is all that can be desired. I n a paper on ‘‘ The Use of Maize as an Adulterant in Oatmeal,” by J. White, F.I.C. (ANALYST, vol. xx., p. 30), the author gives some excellent advice as to the microscopical examination of flours containing maize. Still, I have been unable to obtain concordant results in quantitative estimations when using only the microscope and its appliances. In vol. xxiv., p. 150, of the ANALYST will be found an abstract from an article by K.Bauman concerning this subject, and a method both for detection and estimation of maize is given; but while his method of detecting it is simple and effective, that for its estimation does not work well in my hands. However, it is an extension of this method which I bring before the society to-night. Bauman points out that a 1.8 per cent. solution of potassium hydroxide will under certain conditions gelatinize wheat starch, but leave maize starch unaffected. This I find to be the case, and taking advantage of this, have worked out the following modification and extension : 1. I t is necessary to provide samples of pure wheaten and pure maize flours.316 THE ANALYST. 2. The following solutions are required : (1) Potassium hydroxide ...... ... 18 grammes. (2) Iodine ... ... ... ... ... 0.25 gramme. Potassium iodide ... ... ... 1 gramme. (Make up to a litre with distilled water.) Distilled water to ... ... ... 250 C.C. 50 C.C. Distilled water to ... ... ... 100 C.C. (3) Hydrochloric acid, specific gravity 1-16 Process.-Weigh out the following : ( a ) 0.2 gramme of the sample under examination. ( b ) 0.18 gramme wheat flour, and 0-02 gramme maize flour = 10 % of maize flour. (c) 0.17 $ 9 $ 9 > 7 0.03 7 , ,, =15 ,) 2 ) (d) 0.16 7 , 7 7 9 , (J.04 8 9 ,> -20 ) ) ,, (el 0.15 ?, 8 , 9 , 0.05 ? 7 7 ) =25 ), 7 9 (f> 0.14 $ 8 7 , 7 , 0.06 7 , , I =30 ,) 7 ) Place each of the above in test-tubes (15 centimetres x 2 oentimetres) fitted with paraffined corks, then add to each 20 C.C.of the potassium hydroxide solution; shake uniformly for three minutes ; add 12 drops of the hydrochloric acid ; place in centri- fugal machine revolving 600 times per minute; remove 1 c . ~ . of the liquid, avoiding carefully the residue at the bottom of the tube ; make up to 50 C.C. in Nessler glass ; add two drops of the hydrochloric acid, then 1 C.C. of the iodine solution; stir and compare tints; this will give the amount of maize flour present in the sample to within 5 per cent. only, which is not near enough for our purpose. But if we take 10 C.C. of the clear liquid from each test-tube, add 1 C.C. of dilute sulphuric acid (1 : 7), and boil for two hours (thus entirely converting the starch into sugar), then neutralize, make up to 50 c.c., well mix, and place in a burette, and run into the following mixture, which is kept boiling : Gerrard’s solution‘: ...... ... ... ... 10 C.C. until the colour is discharged, the made-up specimen, requiring the same amount to discharge the colour as the sample under examination, will give the percentage. DISCUSSION. Mr. BEVAN said that he had recently tried, with satisfactory results, a qualitative method for the detection of the presence of maize in wheaten flour which had been communicated to him by Mr. A. C. Wilson, of Stockton-on-Tees. I n this the flour, or starchy compound, is mixed with clove oil, and examined under a 4- or +-inch objective, when the hilum of maize appears as a black dot or s t a r ; the wheat or other starches are practically invisible.Fehling’s solution ... ... ... ... ... 2 C.C. .* On p. 75 of Allen’s “ Chemistry of Urine,” these directions are given for Gerrard’s process : ‘‘ Ten C.C. of freshly-prepared Fehling’s solution, or 5 C.C. of each of the constituent solutions, both accurately niessured, should be placed in a porcelain dish, 40 C.C. of water then added, and the liquid heated to boiling. A solution of potassium cyanide, of about 5 per cent. strength, is graduallyadded from a burette or pipette until the deep blue colour of the liquid is nearly destroyed. The addition of the cyanide is continued very cautiously drop by drop, the liquid being kept constantly boiling and well stirred until the blue colour just disappears, or only a very slight tinge of blue remains. Excess of cyanide solution must be carefully avoided, so that it is safer to discontinue its addition when the blue colour is still faintly perceptible.”THE ANALYST.317 Mr. JOHN WHITE said that a qualitative test-which might also be made quan- titative-for the detection, and, if necessary, the determination of maize in wheaten flour, was communicated to him some three or four years previously by Mr. E. W. T. Jones, and he had found it to answer all practical requirements. After the sample had been thoroughly mixed in a mortar, 1 gramme of it was placed in a test-tube, 10 C.C. of distilled water added, and the mixture well shaken ; 15 C.C. of a 1 per cent. solution of sodium hydroxide mas then added, and the whole again shaken. After standing for not less than three or four hours, nearly the whole of the wheat starch was gelatinized, as in the case of the treatment with caustic potash ; and, if maize was present, a drop of the emulsion, examined under the microscope with a +inch objective and an A or B eyepiece, showed the granules of maize very distinctly. Wheat of a certain special class appeared to resist the action of the alkali for a con- siderable time, but by polarized light this was easily distinguishable from the granules of maize. I n the case of a sample examined jointly, the conclusions independently arrived at by Mr. Jones and himself had been in very close agreement.

ISSN:0003-2654    

DOI:10.1039/AN9002500315

出版商:RSC    

年代:1900

数据来源: RSC

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THE ANALYST. 317 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. (~&fdch Zeit., 1900, xxix., 593 ; through Chem. Zeit. IZep., 1900, 283.)-The authors publish two sets of observations, carried out at different times and places, to ascertain whether the acidity of milk, as pro- duced under different conditions, is always approximately constant, and whether milk can be delivered to a dairy after a long journey in the hot season of the year perfectly sweet. The figures shorn that a high acidity is found not only when the milk is going sour, but also when- an early souring can hardly be expected ; so that the acidity must be considered natural. I t is also evident that even in hot summer weather delivery of a mixed daily milk in good condition is quite possible, even if part of the bulk was undoubtedly sour.The natural acidity of milk is in no way constant in amount, but varies within sensible proportions. Acidity of Milk. Vieth and Siegfeld. F. H. L. Estimation of Fat in Coadensed Milk. A. E. Leach. (Journ. Amer. Chem. SOC., vol. xxii. [9], pp. 589-591.)-1n the case of condensed milk containing added cane-sugar, the sample is well stirred to render it homogeneous, and 40 grammes are weighed out, washed into a 100 C.C. flask and made up to the mark with water. Twenty-five C.C. are placed in a test-bottle, which is then nearly filled with water and 4 C.C. of copper sulphate solution, of the strength of Fehling’s copper solution, the whole being well shaken up and placed in a Babcock centrifuge, preferably driven by electricity, since heat cakes the precipitate and makes it harder to wash. When the separation is complete, the supernatant liquid is drawn off by a pipette, through n318 THE ANALYST.filtering wisp of cotton, the precipitate is washed thoroughly in the machine; and, finally, enough water is added to amount approximately to the normal volume of 17-6 C.C. usually employed for the Babcock test, the subsequent stages of which are then carried out in the ordinary manner. c. s. Detection of Coal-Tar Dyes in Fruit Products. A. L. Winfon. (Jozcriz. Amer. Chenz. Xoc., vol. xxii. [9], pp. 582-588.)-The author recommends Arata's wool test, applied by boiling 100 C.C. of the liquid under examination for ten minutes with 10 C.C. of 10 per cent. potassium bisulphate solution, and a piece of white wool previously boiled in dilute sodium hydroxide and washed, since the natural colouring matters of fruit impart .tt most a pink or brown coloration which turns green in presence of ammonia, and is not restored on washing with water ; whereas coal-tar dyes-the azo-group particularly-produce colorations either unaffected by ammonia or restorable by washing.Care should, however, be taken to ascertain whether the wool is really dyed, or merely coated with the colouring matter; chlorophyll, for example, and colouring preparations of vegetable origin, since they are merely deposited on the surface, are removed by friction or washing. I t is better to apply the subsequent identification tests to the dyed wool rather than to the dye extracted therefrom. The amyl alcohol (alkaline or acid solution) confirmatory tests for fuchsine may be afterwards employed, as well as Gerard's niercuric acetate method and Cazeneuve's mercuric oxide test.The two last are, however, unsuitable for jellies, though useful for fruit juices and syrups. I n reports it is considered better to avoid attempts at particularizing the dye-stuff present, beyond indicating the colour, e.g., red ' or ' orange coal-tar dye.' C. s. Determination of Vanillin. J. Hanus. (Zed. fiir unterszcch. de?- Nnhi-. find Geizzcssmittel, 1900, iii., 531-537.)-The experiments described were carried out with the object of devising a method for the determination of vanillin by the production of a hydrazone of suitable character by the addition of one of the hydrazines. Of those experimented with only the ,B-naphthylhydrazine hydrochloride and the p-bromphenylhydrazine were found to satisfy the requirements./3-NaphthyZhydrazine hydrochloride (C,,H7.NH.NH,.HCI).-The experiments were carried out as follows: The P-naphthyihydrazine solution was added to the vanillin solution in such proportion that 2 to 3 parts of hydrazine were present for every part of vanillin. The mixture was allowed to stand for five hours, after which it was filtered through a dried and weighed filter, and washed with hot water until the washings no longer exercised a reducing action upon silver nitrate. The precipitate was then dried at 90" C., and weighed. To effect complete separation it is necessary that the mixture be allowed to stand for some time, though, on the other hamd, stahding too long may lead to an error in the opposite direction through the production of oxidation products of hydrazine, which cannot be removed by washing.Stahding for five hours appears to give the best results. p - Bi-onzp heizylhydraxiii e ( C,HB,Br.N H. N H,) .-Two to three parts of hydrazineTHE ANALYST. 319 were used for each part of vanillin. The mixture was allowed to stand for four or five hours, after which it was filtered and washed as before. Finally the precipitate was dried at 100" C., and weighed. The results by both processes were satisfacfory. This method is applicable in all cases where an aqueous solution of the vanillin can be prepared, and it has the advantage over Welman's mefhod (titration with alcoholic potash) of being unaffected by the presence of vanillic acid.H. H. B. S. Researches on Cayenne Pepper. G. Gregor. (Zeit. fiir Untersuch. der NahT. u?ad Genussmittel, 1900, iii., 460-471.) 1. On the Assirnilability of Metallic Salts by the Cayenne Pepper Plant.-In a paper contributed to the Cl'em. Zeit. (1899, xxiii., 433) Jonscher called attention to the fact that 0.91 per cent. of barium oxide in the form of readily soluble salt had been found in a sample of ground cayenne pepper. The publication of this paper, and its subsequent discussion in the columns of the journal, led the author to undertake the present investigation. The experiments were carried out as follows : Cayenne pepper plants were cultivated in wooden boxes filled with ordinary garden soil.In one case the soil was used alone; in two other cases barium sulphate and calcium sulphate respectively were mixed with it, whilst in the remainder the soil was watered respectively with solutions of barium chloride, calcium chloride, lead chloride, and copper sulphate. The experiments were commenced in July, and the ripe fruit was collected in October. After drying in the usual way, the percentage of ash in the fruit from each experiment was determined and examined for the particular metals experimented with. From the results obtained, the author concludes that neither barium nor lead is capable of being assimilated by the cayenne pepper plant, and that consequently the presence of these metals in the ash of the fruit must be taken as a proof of admixture.2. On the Percentage of Ash in diferent So?.ts of Cayenne Pepper.-The fruit grown by the author for the purpose of the preceding investigation was found to yield from 9.74 to 13.37 per cent. of ash, the latter result being obtained in the case of fruit grown upon soil containing calcium sulphate watered with solution of sodium chloride. These figures are not only much in excess of those obtained by other investigators, but are also above the maximum fixed by the German Union for establishing standard methods for the examination of food products, viz., 6.5 per cent., with 1 per cent. insoluble in hydrochloric acid, as well as above the maximum proposed by Swiss chemists, viz., 5 per cent., with 2.5 per cent. insoluble. In order, therefore, to furthert investigate the subject, the author collected local specimens of normally grown fruits for examination, and with these he found from 7.12 to 10.03 per cent.ash, and from 0.22 to 0.34 per cent. of this soluble in hydrochloric acid. Further, the results of the examination of twenty-five commercial samples of ground cayenne pepper from various sources gave from 5.71 to 8.92 per cent. of ash, of which from 0.17 to 2.00 per cent. was soluble in hydrochloric acid. The author remarks that the high percentage of ash insoluble in hydrochloric acid found in some of the samples examined must be due either to accidenta3320 THE ANALYST. impurities, or to admixture with some foreign substance. Further examination of this part of the ash showed that the excess consisted in some cases of barium sul- phate and in others of lead oxide. The proportion of barium sulphate was, in the author’s opinion, too insignificant to admit of the supposition that it was purposely added to increase the weight. He considers it more probably due to the practice of artificially colouring the ground pepper. A colouring-matter sold for this purpose under the name of chrome red ” was found to consist of chrysaurein mixed with 60 per cent. of barium sulphate. H. H. B. S.

ISSN:0003-2654    

DOI:10.1039/AN9002500317

出版商:RSC    

年代:1900

数据来源: RSC

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320 THE ANALYST, TOXICOLOGICAL ANALYSIS. Detection of Sulphonal, Trional, and Tetronal i n Cases of Poisoning. D. Vitali. (Boll. Chim. Farm., 1900, xxxix., 461 ; through Chem. Zed. Rep!, 1900, 243.)-The animal matters submitted for examination are warmed in a porcelain basin three times with twice their volume of 90 per cent. alcohol; after cooling, the extracts are filtered, and the solvent distilled off. The residual aqueous liquid is warmed, filtered, made alkaline with potassium hydroxide, and exhausted three times with an equal volume of ether. (Potash has no effect on sulphonal; it is only employed to prevent colouring matter passing into the ether.) The ether is driven off, leaving the sulphonal behind. It can then be identified by the reactions described by Wefers-Bettinck, Schwarz, Ritsert, and Vulpius, or by Vitali’s own tests as follows : (1) When sulphonal is fused with three times its weight of potash, a garlic-like odour is evolved ; the mass becomes yellow, then red, and scarlet when cold.If the melt is extracted with water, a turbid, bluish liquid is obtained, and in the filtrate polysulphides can be detected by means of sodium nitroprusside, thio- sulphate by acidification. If the mixture of sulphonal with potash is heated to the melting-point of glass, the red colour changes to a blue, owing to the formation of a body analogous to ultramarine. (2) When sulphonal is warmed with a little metallic sodium, sodium sulphide is produced, as may be recognised by treatment with water and nitroprusside. (3) If sulphonal is heated with twice its weight of potassium periodate (only small quantities should be used), a slight explosion occurs, and potassium sulphate is produced.This test succeeds with 1 milligramme of substance. Sulphonal resists putrefaction, and it can therefore be recovered without loss by the above process from animal remains in a state of decomposition. The same method of isolation, and the same tests, are available in the case of trionel or tstronal. They can be distinguished one from another by their different melting- pointE and by the different appearance under the microscope of the crystals obtained by the spontaneous evaporation of their aqueous or ethereal solutions. Sulphonal and trional are only eliminated in their original condition through the urine in small quantities. They may be detected therein by concentrating the urine on a water- bath to the consistency of an ‘‘ extract,” treating the residue with boiling alcohol, filtering, distilling off the spirit, again filtering the aqueous liquid, boiling with potash to destroy urea, and finally shaking out with ether. (Cj. ANALYST, 1899, xxxiv., 129.) F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9002500320

出版商:RSC    

年代:1900

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THE ANALYST. 321 ORGANIC ANALYSIS. The Carbohydrates of Irish Moss (Carrageen). J. Sebor. (Oester. Chela. Zeit., 1900, iii., 441.)-The mucilage yielded on decoction of Irish moss contains a complex carbohydrate yielding on hydrolysis gdactose, dextrose, and Imulose, elso ib small quantity of a pentosan, probably xylan. The sugars, however, are not present in the same proportion as in raffinose. Whether the moss contains a mixture of the three corresponding pentosans or a carbohydrate yielding the three sugars cannot be ascertained; but as the mucilage has an organic structure, is insoluble in water, easily yields colloidal solutions like starch paste, and is readily converted into dextrin-like substances, it would appear to be a vegetable reserve-stuff of great molecular complexity similar to starch.F. H. L. Cedar-nut Oil. L. von Schmoelling. (Chem. Zeit., 1900, xxiv., 815.)-This oil is obtained from the nuts of the Siberian cedar, or stone pine (Pinus cembra), a tree which forms vast forests in the southern districts of that country. It has a golden- yellow colour and a very pleasant, mild taste, though somewhat rancid. It is used in Siberia as a food. The oil is scarcely soluble in cold alcohol, carbon bisulphide or benzene; but in cold petroleum spirit, chloroform, acetone and amyl alcohol it is soluble in all proportions. Mixed with an equal volume of fuming nitric acid, it gives a dark red colour, which is permanent for more than twenty-four hours. Ten drops of oil and 2 drops of strong sulphuric acid show a, dark-brown ring with black streaks in the oil; with 1-53 sulphuric acid it exhibits a yellowish-brown colour.The constants of cedar-nut oil are as follows : The three first liquids dissolve it on warming. Specific gravity ... ... ... ... Hehner number ... ... ... ,.. Saponification value ... ... ... ... Iodine value (Waller) ... ... ... ... Acid value ... ... ... ... Volatile fatty acids ... ... ... ... Free fatty acids ... ... ... ... Total fatty acids .._ ... ... ... Mean molecular weight ... ... ... Glycerin (esters x'0.0547) ... ... ... Acetyl number (after six days' standing) Liquid fatty acids (Muter and De Koninghj" Uneaponifiable matter (Fahrion) ... ... Temperature reaction (Maumenk-Archbutt) ... Solidifying point ... ... ... ... Iodine value of liquid acids ... ...... Oil. 0.930 91-97 191.8 159.2 3.25 10.31 per cent. 3.77 ,, 1.6 9 , 95.74 ), 280 1.3 per cent. - 98" Fatty Acids. 161.3 193.0 290 81.9 87.0 per cent. 11.3 184.0 Kryloff examined a sample of this oil in 1898, and obtained : Rehner number, 93.33 ; saponification value, 191.8 ; iodine value, 149.5 to 150.5 ; acid value, 1-09 ; and volatile fatty acids, 2.0 per cent. Among the constituents of the oil palmitic acid322 THE ANALYST. can be recognised, while the liquid acids consist mainly of linolic acid, with some oleic and very little linolenic acid. On heating the oil with 5 per cent, of manganese borate for four hours to 140" or 150" a varnish " is produced, which dries on glass in double the time taken by linseed varnish similarly prepared ; the product is very viscid, and resembles a blown oil.This last characteristic, coupled with the high price of the original oil, would prevent it from being used in the manufacture of varnish. F. H. L. Testing for Vegetable Oils by a Modified Welmann's Test. T. Geuther. (Zeits, ofentl. Chem., 1900, vi., 328 ; through Chem. Zeit. Rep., 1900, 283.)-Finding that the commercial 10 per cent. solution of phosphomolybdic acid is unsuited for analytical purposes, the author proceeds as follows: 5 grammes of pure sodium phosphomolybdate are mixed with 25 C.C. of water and 30 C.C. of pure 1.39 nitric acid, shaking till solution is complete. A test-tube is tared, and into it are weighed 5 grammes of the lard to be examined, after it bas been melted, mixed together, and carefully filtered.Three grammes of the purest chloroform are next weighed into the tube, and finally 20 drops of the teagent are added from a pipette. After thorough agitation, the tube is set aside, and the colour which develops within two minutes is observed. I n presence of only 5 per cent. of an unrefined and unbleached oil, a distinct dark green tint appears ; while pure, fresh, filtered lard gives only a yellow colour. Any green colour that develops after the two minutes may be neglected. F. H. L. Action of Sodium Ethoxide on Fats-Volumetric Estimation of Water in Alcohol-Determination of Glycerol in Fats. H. Bull. (Chenz. Zeit., 1900, xxiv., 814, 845.)-The process which the author has already described (ANALYST, 1900, xxv., 126) for estimating the unsaturated fatty acids in train oil depends on the assumption that the neutral glycerol esters in those oils are saponified by sodium ethoxide.Such, however, is not the case unless the alcohol in which the original metallic sodium was dissolved contained at least 4 per cent. of water. This quantity of water not only cause6 complete saponification, but also raises the solubility in ether of the sodium salts of the train-oil unsaturated acids, while an increase in the amount of alcohol present behaves in a similar manner. Bull appends to his present article a table giving the unsaponifiable matter and the fatty acids with soluble sodium salts as redetermined after eighteen months' storage in half-filled bottles on the same oils previously examined (Zoc. cit.), the proportions of fatty acids being now considerably lower, owing, no doubt, to the action of air and light on the samples.When sodium ethoxide is shaken with a fatty (e.g,, train) oil not containing any free acid, an emulsion is first produced, which quickly disappears, leaving a clear solution that deposits fine crystals of mono-sodium glyceroxide according to the equation (F being a fatty acid radicle) : C&I,.(OF), + C,H,.ONa + 2C,H,.OH = C,H,.(OH),.ONa + 3C,H,.OF. This reaction occurs almost instantaneously at ordinary temperatures, andTHE AN,4LYST. 323 without the production of a sensible amount of heat ; it proceeds between an equal number of molecules of fat and ethoxide, instead of between 1 molecule of fat and 3 of sodium hydroxide, as takes place during saponification.Estinution of Water in Alcohol.-If, then, a neutral fat is boiled with a solution of sodium ethoxide in absolute alcohol, no saponification occurs ; but in presence of water a certain quantity of ethoxide is decomposed into alcohol and hydroxide (which reacts with the fat), th3s forming a means of calculating the moisture. Normal ethoxide is required, which is standardized by gently warming 10 C.C. r i t h 5 C.C. of a fatty oil as free as possible from uncombined acids (medicinal cod-liver oil, for example) in a perfectly dry flask fitted with an upright condenser. The liquid is cautiously heated for thirty minutes, then allowed to boil for fifteen minutes ; finally cooled, diluted with about 20 C.C. of neutral ether, and titrated with semi-normal hydrochloric acid and phenolphthalein.Repeating the process with an alcohol containing some moisture, less standard acid is used in the titration, and the differ- ence calculated into H,O. Various examples of the iiiethod are quoted which show satisfactory agreement among themselves, and which also indicate accurately the strength of the alcohol employed. I t is clear that the same process is available for the valuation of other alcohols than ethylic. By altering the conditions the reaction may be utilized to prepare strictly absolute ethyl alcohol. In a sample dried over quicklime, the proportion of water still remaining is determined as above ; the neces- sary amount of metallic sodium or sodium ethoxide and an excess of a neutral fat are added to the bulk, the whole is heated for a short time under an inverted con- denser, and the alcohol is distilled off on the water-bath, using diminished pressure towards the end of the operation.Estimation of Glycwol in Fats.-In a vessel graduated at the 50 C.C. point, and provided with a stopper, 3 gramines of fat and 3 C.C. of 2N sodiurn ethoxide are well shaken together and heated to 70" C. for thirty minutes on the water-bath. After cooling for half an hour in the air, 23 C.C. of dry ether are added, the whole is agitated, and diluted with more ether to the mark. In three hours' time the sodium glyceroxide, completely thrown out of solution by the ether, has settled to the bottom, and the supernatant liquid is perfectly clear. Twenty-five C.C. thereof are pipetted oif, diluted with 10 C.C.of alcohol, and titrated with decinormal hydrochloric acid and phenolphthalein, overlooking the brown tint due to the presence of oxy-acids. The residual 25 C.C. in the tube are next titrated similarly, except that 5 C.C. of semi-normal HCl should be run in at once. From the difference between the volumes of decinormal acid absorbed, the emount of glycerol may be calculated by using the factor 0.0092. If the same pipette is always used, the results should be 0.06 per cent. too low, no allowance being made for the volume of the precipitated glyceroxide. The chief difficulty met with in the process is to ascertain the end-point of titration owing to the brown colour of the liquid ; possibly some other indicator would be better than phenolphthalein. Four tests of a whale-oil (acid number, 3.6, saponification number, 188.3) gave 9.69, 9.54, 9-57, and 9.5 per cent.of glycerol; the firsb result being recognised as about 0-1 per cent. too high, due to adherence of the solution to the pipette. The author has not succeeded in determining the amount of glycerol in com-324 THE ANALYST. mercial glycerin by this process. Addition of ether causes a precipitation of sodium oxide as well as of the glyceroxide; in this respect benzene is a better precipitant to employ. The water in glycerin is capable of estimation as above ; but the practical difficulties of the method render it of little interest. I t should be noted that sodium glyceroxide behaves like the ethoxide : it saponifies only in presence of water, and quite slowly, as it is somewhat insoluble in spirit.This fact is important, since such conditions may arise when fats are being hydrolysed in alcoholic liquids of great strength. F. H. L. Detection of Bile-Pigments. Triollet. (Bull. Sciences Pharmacologiques, July, 1900 ; through Chern. Zeit. Rep., 1900, 284.)-This process is a further modifica- tion of that recommended by Gurdin and modified by Jolles. Fifty C.C. of urine are treated with an excess (40 or 50 grammes) of ammonium sulphate, and filtered through cotton-wool, which retains all the precipitated pigments. The wool is extracted with hot chloroform, which dissolves bilirubin and bilifuscin ; the solution is evaporated to dryness. The wool is next extracted with hot alcohol, which dissolves biliverdin and biliprasin; the solution is also evaporated.The two residues are taken up in boiling water, yielding a, faintly-coloured solution free from blood, albumin, pus, and urea. The liquid is then cautiously floated on to nitric acid containing nitrous acid. At the junction of the liquids two coloured zones appear-- one bright red, the other yellow. I n ten minutes a green ring appears between the two former, and five minutes later a fine blue colour will be seen between the violet- red and the green. Afterwards the tints become violet-red, blue, green, yellow, and grow in intensity to a maximum in half an hour. After two hours there is a blue ring between two yellow ones, and in five hours only a uniform yellow tint is left. F. H. L. Valuation of Glue. A. Heinemann. (Chenz. Zeit., 1900, xxiv., 871.)-The author doubts whether the processes hitherto suggested for the examination of glue are of much industrial use.Determination of the viscosity of a solution of known strength may indicate the value of the material if it be required to manufacture “ compositions,” “ hectograph surfaces,” etc. ; but it does not appear to throw any light on the real adhesive power of the glue. Similarly estimation of water, fat, and ash may be important; but there is no evidence that the binding power is in pro- portion to the amount to true gelatin in the sample. Heinemann suggests a process which depends on ascertaining the minimum strength of a solution that exhibits adhesive power. Strips of strong, smooth paper 4 x 3-5 inches are cut u p ; one of these is brushed over with a (say) 1 per cent.solution of the glue to be examined for a length of 2-5 inches, another dry strip is laid over it, and the whole is pressed together under a 5-pound weight for exactly 1 minute, or if the atmosphere be very damp, for 14 or 2 minutes. The papers are then lifted, and it is noticed whether the joint will carry a weight. At or about the “ critical ” degree of dilution, the jointTHE ANALYST, 325 will either support a fairly heavy weight, even 30 pounds, or nothing at all. By simultaneous comparison with a solution prepared from a standard sample of glue, altering the strength of the experimental solution as may be necessary, results can be obtained which should indicate the adhesive power and therefore the commercial value of the glue.[Presumably the second strip is laid on the first so as to overlap only for just over the 2+ inches of painted surface, thus leaving at either end a length of 14 inches of single paper whereby to clip the test piece. F. H. L. F. H. L.] On Certain Peculiarities in the Urine of Vegetarians. J. H. Long. (Jown. Amer. Chem. SOC., vol. xxii. [9], pp. 592-595.)-1n the experiments detailed the reducing power of the urine was apparently about 20 per cent. above the average, but the difference was mainly due to higher concentration, the average daily excre- tion (874 c.c.) being below ‘the normal. The proportion of creatinin was unusually low, the uric-acid creatinin ratio being 1 : 1.2 instead of 1 : 2, and is probably attributable to low f ood-consump tion and rn et abolism. The distribution of the reducing power (total, 6.888 grammes of cupric oxide per 1,000 C.C. of urine) is interesting, 2.373 grammes being allocated, on the basis of previous experience, to uric acid and creatinin, leaving 4.515 grarnmes of cupric oxide as the amount corresponding to the carbohydrates or similar bodies present. Hence it is considered that a purely vegetable diet, wherein fats and carbohydrates pre- dominate, favours the increase of non-nitrogenous (probably carbohydrate) substances in the urine. c. s. A Limiting Standard of Acidity for Moorland Waters. W. Ackroyd. (Chem. News, vol. lxxxii., pp. 162, 163.) - Plumbism, due to the solvent action of moorland water on lead piping, does not, in the author’s experience, occur when the acidity of the water is lower than the equivalent of 0.5 part of aulphuric acid per 100,000 of water, and he therefore proposes this limit should be adopted as a tenta- tive standard of acidity for such waters when the same is estimated by & normal alkali in presence of phenolphthalein as indicator. It is stated that the range of acidity in nine samples of water, not above suspicion in respect of causing plumbism, was 0.53 to 0.91 (average 0-63), whilst in sixty-one samples from places where plumbism is unknown the acidity ranges from 0.20 to 0.41, the average being 0.27. c. s.

ISSN:0003-2654    

DOI:10.1039/AN9002500321

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年代:1900

数据来源: RSC

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THE ANALYST. 325 I N O R G A N I C A N A L Y S I S . Influence of Silica upon Silver Assay. L. Strauss. (PYOC. AmeY. 1mt. Mining Eng., Canadian Meeting, 1900; through Cltem, Zeit. Rep., 1900, 275.)- When silver is assayed in presence of silica, some of the metal passes into the slag, causing loss; and experiments have shown that addition of ferrous sulphide to the326 THE ANALYST. mixture renders the loss almost constant. I n order to ascertain the precise action of the silica, Strauss has assayed various mixtures of silver (0.99 fine) and lead with pure ores, such as pyrites, zinc blende, lead glance, etc., sulphur and silica at temperatures of 900" to 1,000" C., keeping the amount of lead and silver so far as possible the same. From his results the author concludes that the effect of the sulphides is not uniform, but depends on the nature of the ore to an extent which demands further investigation.Nevertheless, in assaying pure silver and lead, increasing the proportion of silica increases the loss of silver. I n presence of ferrous sulphide large quantities of silica carry silver into the slags ; but if only a little silica is present, the iron sulphide reduces the loss. I t is therefore impossible to insure obtaining the same yield of silver from different ore mixtures, even if the amount of metal in the assay is actually the same. F. H. L. Estimation of Gold and Silver in Pyrites. W. Buddeus. (Chem. Zeit., 1900, xxiv., 922.)-The ore is reduced till it will pass through a sieve of 300 or 400 meshes per square centimetre-extreme fineness is not essential-and 100 grammes are taken for analysis.If, however, it contains less than 50 grammes of gold per 1,000 kilos., 200 grammes should be employed, all the following figures being then doubled correspondingly. I t is placed in a 70 C.C. biscuit crucible, lightly covered, and put into a bright red-hot muffle for thirty or forty-five minutes until the sulphur flame disappears. The, crucible is then cooled, and the coherent mass is thrown out into a beaker or basin, wiping the crucible with a brush. Without breaking up the lump, it is covered with 250 C.C. of 1 : 1 hydrochloric acid, free from arsenic. After standing one hour in a warm place, a second 250 C.C. of acid are added, and the whole is boiled. The liquid is diluted to 1 litre, allowed to settle, filtered, and the precipitate, which contains all the gold, silver, silica, and alumina of the ore, is washed two or three times with water.The paper and contents are dried, introduced into a 150 C.C. Hessian crucible with 50 grammes of lead and 5 grammes of borax, and well mixed. If preferred, 50 grammes each of lead acetate and dry sodium carbonate may be used instead of the metallic lead. The whole is melted ; the button is taken out, cupelled, and finally parted in the ordinary way. The preliminary removal of the iron sulphide prevents loss of gold and silver in the large mass of slag otherwise obtained, while it avoids the very high temperatures needed to convert the sulphide into a silicate, which tends to cause volatilization. For these and other apparent reasons the process is much cheaper to work ; it gives considerably higher figures than the usual method-figures which agree much better among themselves, and it is therefore more accurate and trustworthy.F. H. L. Estimation of Mercury in Urine. J. Malkes. (Chem. Zed., 1900, xxiv., 816.) -This process, devised by Stukawenkow, has been in use in Russia, for several years, but appears to have been overlooked elsewhere. It depends on the precipita- tion of the mercury with albumin and the find production of mercuric iodide. Five hundred C.C. of urine in a, 1-litre flask are mixed with 5 C.C. of egg albumin andTHE ANALYST. 327 15 or 20 drops of acetic acid, then placed on a water-bath and heated for fifteen to twenty minutes. The whole is poured into a beaker, and allowed to settle for twenty minutes; the clear liquid is run away, and the deposit collected on a filter.The paper and its contents are laid on a porous tile for a few minutes. The pre- cipitate is then removed from the paper, brought into a small cylinder, and covered with 50 C.C. of strong hydrochloric acid, a spiral of copper wire being immersed in the liquid. In about fourteen or sixteen hours all the mercury has amalgamated with the copper, and the acid has become dark in colour. The wire is washed with water, alcohol and ether, and dried between filter-paper. I t is next dropped into a tube 5 millimetres in diameter with a crystal of iodine, and heated cautiously till the mercuric iodide forms a red sublimate on the walls of the tube.The amount of mercury in the original urine is estimated by comparing the size of this ring with that yielded by a urine to which a certain quantity of mercuric chloride has been added, it being convenient to prepare a series of such tubes to act as standards. The method is very exact, especially when only small amounts of mercury are present. F. H. L. Estimation of Tungsten in Ores. F. Bullnheimer. (Chcnt. Zeit., 1900, xxiv., 870.)-Although the determination of tungsten in high grade or purified ores presents no particular difficulty, the presence of inferior material, and especially of phosphorus and arsenic compounds, complicates the process. One or two grammes of the finely- powdered mineral are best mixed with 4 grammes of sodium peroxide and 3 grammes of sodium hydroxide in a nickel crucible, and heated over a smail flame till the mass softens.The temperature is then raised till tbe bottom of the crucible begins to glow and the mixture is thoroughly fluid, stirring continuously. After the melt has solidified, but while it is still hot, crucible and contents are thrown into water. If manganese causes the liquid to be green, it is decolorized with hydrogen peroxide, then cooled, diluted to 250 C.C. and filtered. To half the filtrate 20 grammes of ammonium nitrate are added, and after the tin and silica have settled, a sufficient quantity of magnesium nitrate solution is run in gradually and with agitation. After 6 or 12 hours the precipitate is filtered off and washed with ammonia and water; the filtrate is rendered slightly acid with nitric acid, cooled if necessary, and treated with 20 or 30 C.C.of a solution of mercurous nitrate (200 grammes warmed with 20 C.C. of strong nitric acid and some water, diluted to 1 litre and kept over mercury). After standing a few hours, ammonia is introduced till the liquid is only faintly acid, and the whole is allowed to rest until the supernatant solution is clear. The preci- pitate of mercurous tungstate is collected, washed with water containing mercurous nitrate, dried, and ignited first over a Bunsen and then over the blowpipe to constant weight in an uncovered crucible. The sodium hydroxide in the fusion makes the melt more liquid and preserves the crucible. The nitrates of ammonium and magnesium must be employed, as their chlorides and sulphates would interfere with the mercurous reagent.It is very important not to add the magnesium nitrate till the ammonium nitrate has thrown down the tin and silica. If a considerable amount of molybdenum occurs in the sample, which is not often the case, much time is required to volatilize it completely328 THE ANALYST out of the final tungsten precipitate. The process may then be hastened by igniting shortly, adding ammonium chloride, and igniting again, first in the covered, afterwards in the uncovered crucible. F. H. L. The Determination of Tungsten in Ores and Residues. H. Borntrager. (Zeit. anal. Chem., 1900, xxxix., 361, 362.)-One gramme of the ore is fused with 10 grammes of sodium hydroxide for an hour, when the clear mass is extracted with hot water, the whole made up to 250 c.c., cooled and filtered.One hundred C.C. of the filtrate are added to a mixture of 15 C.C. of concentrated nitric acid, and 45 C.C. of concentrated hydrochloric acid, and evaporated to complete dryness in a porcelain dish. The residue is taken up with a solution containing 10 per cent. of ammonium chloride and 10 per cent. of concentrated hydrochloric acid, filtered, and the residue, which contains silica and tin oxide in addition to tungstic acid, dissolved in warm ammonium hydroxide, with which the filter is also washed. The solution is run into a mixture of 15 C.C. of nitric acid and 45 C.C. of hydrochloric acid, and the whole again evaporated to dryness. The tungstic acid, as thus obtained, is free from silica and tin oxide.In the analysis of metallic tungsten, which also contains oxygen, carbon, antimony, iron, and silica, a preliminary ignition for thirty minutes is necessary, and in the fusion an addition of a little nitre to the sodium hydroxide is advisable. Metallic tungsten, as met with in commerce, usually contains from 95 to 97.5 per cent. of tungsten. The method of precipitation with mercuric nitrate is stated to give very uncer- tain results, owing to the readiness with which the finely divided mercuric tungstate passes through the filter. The method described above is now used in all the larger metallurgical works in Germany. C. A. M. A Method for the Rapid Estimation of Lime. The filter-paper is burnt. W. H. Hess. (Jozun. Amer. Chem. SOC., 1900, xxii., 477.)-The lime is precipitated and separated as oxalate in the usual way.Then the lime in the crucible is mixed with an equal bulk of ammonium nitrate and about twice as much ammonium sulphate. The crucible is then covered with a lid, and ignited cautiously until no more fumes are observed. Intense ignition is unnecessary, and is to be avoided. The lime is thus converted into sulphate, and is weighed as such. The results quoted are all 0.1 per cent. too low. A. M. The Examination of Commercial Thorium Nitrate and Incandescence Mantles. (Berichte, xxxiii., 2028-2031.)-1t is well known that the thorium preparations obtained from monazite sand show enormous variations in their capacity for emitting light, so much so that the German factories have their mantles officially tested at Charlottenburg and Karlsruhe, and sell them with a guarantee as to their emission power.This diEerence is altogether apart from the prejudicial influence of common impurities such as phosphoric acid, alkalies, and iron, chromium, and aluminium oxides. W. Muthmann and E. Bauer.THE ANALYST. 329 The authors have examined different samples of commercial thorium nitrate by their cathode-luminescence method (Berichte, xxxiii., 1748 and 1760) and have found them to invariably contain impurities in the form of rare earths. In this method it was found best to convert the nitrates into anhydrous sulphates, and to subject these to the influence of cathode rays in an exhausted tube, the phosphorescent light emitted being decomposed by a prism, as used by Crookes. In all the preparations examined, the occurrence of lines of gadolinium and yttrium was proved, and it was established that the former greatly preponderated. One sample of commercial nitrate (840 grammes) was dissolved in 5 litres of water and fractionally precipitated by means of a solution of potassium chromate, steam being introduced under a pressure of three atmospheres during the precipita- tion (ANALYST, xxv., 130).The first six fractions consisted of thorium chromate yielding a pure white oxide (320 grammes). On further fractionation, a slight quantity of a dirty olive-green chromate was precipitated, and the residual solution, from which nothing more was precipitated by potassium chromate, yielded on the addition of potassium hydroxide precipitates of the hydroxides of gadolinium and yttrium.These gave about 0.5 gramme of the oxides, which, fromt heir luminescence spectrum, were found to consist mainly of Gd,O,. The mixed oxides from the olive-green chromate, which was the last chromium precipitate obtained, were found by spectrum analysis to consist principally of neodymium and praseodymium oxides. Hence the authors concluded that the total amount of these impurities was at least 0.3 per cent. The pure thorium nitrate thus obtained was mixed with the requisite amount of cerium ammonium nitrate, and photometric tests made with mantles prepared from the mixture. I t was found that the addition of the above impurities has a marked injurious influence on the emission-capacity of the mantle, but that the ordinary im- purities in the cerium oxide (neodymium and lanthanum salts, etc.) compose such a trifling proportion of the total earths in the mantle that they appear unlikely to have any appreciable effect upon the light.C. A. M. The Estimation of Cerium in Cerous Salts. G . v. Knorre. (Eel-ichte, 1900, xxxiii., 1924-1929.)-1n order to use the author's volumetric method (ANALYST, xxiii., 191) with cerous salts it is necessary to convert these quantitatively into ceric salts. This may be readily effected by adding sulphuric acid to the solution, then ammonium persulphate in excess, and heating the liquid to the boiling-point. Even a very dilute solution becomes yellow in a few minutes when thus treated, so that the reaction appears to afford a sensitive test for cerium.L4n essential condition is that the sulphuric acid must not be added in too great an excess, since otherwise the hydrogen peroxide liberated would reduce ceric salts when formed. The quantitative oxidahion is carried out as follows : The solution of the cerous salt is acidified with the smallest possible quantity of sulphuric acid, and, after the addition of ammonium persulphate, boiled for one or two minutes. The beaker is cooled in water at about 40" to 60" C., a second portion of persulphate introduced,330 THE ANALYST. and the liquid again heated to the boiling-point. After one more cooling, a third portion of persslphate is added, and the liquid now boiled for ten to fifteen minutes, after which it is advisable to add some more sulphuric acid to destroy the excess of persulphate as far as possible.From 0.2 to 0.3 gramme of cerium require for oxidation about 3 grammes of ammonium persulphate. This is dissolved in water, and about half added for the first boiling, and one-fourth for the second and third boilings. When the oxidized solution is perfectly cold, the cerium is titrated with standardized hydrogen peroxide until colourless, and the excess of the latter titrated back with standard permanganate. C. A. MI. The Determination of Potassium in Potassium Salts. H. Neubauer. (Zeit. anaZ. Chem., 1900, xxix., 481-502.)-For the estimation of potassium in various mixtures of sulphates and chlorides of potassium, sodium, calcium and magnesium, which are commonly known as “ potash salts,” the author recommends the following method, each stage of which is elucidated by experiments described in detail in the paper : Twenty-five C.C. ( =0*5 grainme of substance) of an aqueous solution of the salts are evaporated together with a few drops of hydrochloric acid and sufficient platinum chloride to leave a slight excess after the formation of the double chloride.The evaporation is continued to dryness, but the heating must not be continued longer than is necessary. After cooling the mass is moistened with about 1 C.C. of water, and carefully rubbed with the end of a flattened glass rod. It is next treated with at least 30 C.C. of commercial alcohol (93 to 96 per cent,) in successive portions of 10 c.c., and thoroughly rubbed with the glass rod after each addition. If much sodium or magnesium sulphate be present, the salt is first soft and pasty, but eventually becomes hard and crystalline.The basin is now covered and allowed to stand for thirty minutes, the pre- cipitate receiving an occasional rub during the time. I t is then filtered into it Gooch crucible containing asbestos, after being washed with akohol in the dish, as far as possible. On the filter it is washed with ether, and the latter removed by drawing a current of air through the filter. The crucible is next gently heated while a current of hydrogen or coal-gas is introduced through a hole in the lid. The flame must be very small at first, in order to prevent decrepitation of the crystals. After five minutes it may be slightly in- creased, so that the bottom of the crucible is at a dull red heat in the middle.The reduction is continued for twenty minutes. The contents of the crucible are first moistened with cold water, and then washed with hot water, with the aid of the filter-pump, about fifteen times, and then with dilute nitric acid (5 per cent.) for about thirty minutes without the use of the pump, the acid in the crucible being added to as required. Finally, the acid is drawn off and the residual platinum washed with hot water, ignited and weighed. The weight multiplied by 0.48108 gives the corresponding amount of potassiumTHE ANALYST. 331 oxide (K,O). It is advisable to repeat the washing with nitric acid to insure the complete removal of the salts. As there is a chance of error through the asbestos losing in weight during the washings, the author states that he has made successful experiments in the direction of using spongy platinum instead of asbestos in the Gooch crucible.C. A. M. Diphenylcarbazide as a Reagent for Certain Metallic Compounds. A. Caze- neuve. (Joum. Phaym. Chim., 1900, xii., 150-156.)-The formation of the diphenyl- carbazones of copper and mercury can be utilized for the detection of traces of those metals. Salts of silver, gold, and zinc (in concentrated solution) have also an action on the carbazide, but the faint rose colour produced cannot be confused with those of copper (violet) and mercury (blue). Certain oxidizing agents-e.g., ferric salts and chromates-also produce characteristically coloured compounds. Detection of Copper.-The diphenylcarbazide should be purified by crystallization from glacial acetic acid, and drying at 80" C.For the detection of copper in solutions containing 1 part or more in 1,000, a few drops of a recently prepared 1 per cent. alcoholic solution are added to the previously neutralized liquid, when an intense violet colour is immediately developed. I n solutions of 1 : 10,000 or more, 5 C.C. of a cold solution of the reagent in benzene are shaken with 10 C.C. of the neutral solution under examination. Solutions of 1 : 100,000, which give no coloration with potassium ferrocyanide, show the author's reaction distinctly. Detection of Mercury.-The test is made in the same way as for copper. A deep- blue tint, which is still visible in a dilution of I : 100,000, is obtained. I t can be distin- guished from the copper coloration by the fact that in a solution of a niercurial salt containing 1 : 10,000 it does not disappear on the addition of a drop of concentrated nitric acid.Detection of Iron in Ferric Salts.-These give a red coloration with the benzene solution of the diphenylcarbazide, which is perceptible in solutions containing 1 : 100,000. On adding a drop of glacial acetic acid or of a 1 per cent. solution of potassium ferrocyanide the colour nearly disappears, the benzene only retaining a faint brown shade. The reaction is not so sensitive as those given by copper and mercury. L)etectio?L of Chromates. --The solution of the chromate is rendered strongly acid with acetic or hydrochloric acid and a little powdered diphenylcarbazide introduced. An intense violet coloration is developed on shaking the liquid, and this reaction is sensitive for solutions containing only 1 part of bichromate in 1,000,000. The colour can be distinguished from that given by copper or iron by the fact that it is not es- tracted from its aqueous solution by benzene; moreover, iron and copper do not give aviolet coloration in the presence of an excess of free hydrochloric acid.A chromate can thus be detected in the presence of a ferric salt. C. A. M. The Use of Sodium Thiosulphate in Quantitative Analysis. F. Faktor (Zeit. anal. Chem., 1900, xxxix., 345-354.)-The author has made numerous experi- ments on the behaviour of sodium thiosulphate with different metallic salts, with the332 T E E ANALYST. object of determining to what extent it could replace hydrogen sulphide in quantita- tive analysis.Chromates.-On boiling together aqueous solution of potassium bichromate and sodium thiosulphate, a brown precipitate of hydrated chroniic chromate is obtained, whilst part of the bichromate is converted into normal chromate. After continued boiling with thiosulphate in excess, the whole of the chromate is precipitated, and the precipitate can be ignited and weighed as chromic oxide. Potassium chromate when treated in the same way does not yield a precipitate of chromic chromate, which, however, is obtained quantitatively on adding ammonium or magnesium chloride to the liquid before boiling. Sodium chloride, however, does not induce a precipitate. Chromic salts are decomposed on continued boiling with sodium thiosulphate, yielding chromic hydroxide as in the equation : Cr,Cl6 4- 3Na,S20, + 3H,O = Cr,06H, + GNaCl + 3 S 0 , + s,.As this method did not yield altogether satisfactory results, the precipitation was rendered more complete and rapid by adding to the solution of the chromic chloride a definite quantity of potassium chromate solution of known strength, together with some ammonium chloride, boiling, and deducting from the chromic oxide, obtained on igniting the precipitate, the amount due to the chromate added. Lead Salts.-Good results are given by the following method : The hot solution of lead nitrate is mixed with ammonium chloride, and the resulting precipitate of lead chloride allowed to dissolve in the hot liquid. On now adding a hot con- centrated solution of sodium thiosulphate, the lead is precipitated quantitatively as sulphide. Mercuric SaZts.-On treating a hot solution of mercuric chloride with sodium thiosulphate, the mercury is quantitatively precipitated as sulphide, and the pre- cipitation is much more rapid than with hydrogen sulphide.Silver XaZts.-These react at the ordinary temperature with sodium thiosulphate, yielding a white precipitate (Ag,S,O,), which on warming becomes yellow and finally black (Ag,S). The tabulated results given by the author show that the method is suitable for the quantitative estimation of silver. Nickel and Cobalt Salts.-Nickel salts give a black precipitate of nickel sulphide on being boiled with sodium thiosulphate, but too slowly and incompletely for a quantitative estimation, even after the addition of ammonium chloride.The same difficulty was experienced in the case of cobalt salts. C. A. M. The Iteduction of Nitrates by Lactic Acid. L. Vanino and 0. Hauser. (Zeit. anal. Chem., 1900, xxix., 506,507.)- When bismuth nitrate is heated with lactic acid on the water-bath, it begins to decompose, and at a higher temperature (200" to 210" C.), metallic bismuth separates. In a quantitative experiment the authors obtained from 10 grammes of the salt about 4 grammes of black bismuth powder, or about 93 per cent. of the calculated quantity. Basic bismuth nitrate required a higher temperature for its reduction.THE ANALYST, 333 Mercuric nitrate is slowly decomposed above 100" C. with the deposition of mercury, and a similar reaction takes place in the case of mercurous nitrate, though more slowly.Cadmium, silver, and lead nitrates all yield mirrors of their respective metals. Cobalt nitrate heated with lactic acid at 360" to 370" C. yields a black magnetic powder, consisting of a mixture of carbon and metallic cobalt. The yield of the latter was 1-6 grammes as against 1.9 grammes calculated, and it constituted 52.6 per cent. of the powder. Nickel nitrate is similarly reduced. A strongly magnetic powder was obtained in the same way from ferric nitrate, but this was not proved to contain metallic iron. With the chlorides and sulphates of these metals there was either no reduction or only a very slight one. C. A. M. Estimation of Chlorides, Chlorates, and Perchlorates when mixed together.N. Blattner and J. Brasseur. (Chem. Zeit., 1900, xxiv., 793.)-The author's process is based on the fact that sulphurous acid reduces chlorates to chlorides, but is without influence upon perchlorates. Twenty or 40 grammes of the sample are dissolved in 200 C.C. of water ; in 50 C.C. of the solution the chlorine of the chlorides is determined by titration with silver. Another 50 C.C. are satmated with a current of pure sulphurous acid gas, or mixed with 50 C.C. of a saturated aqueous solution of the gas, then boiled gently, treated with precipitated chalk to destroy the free sulphuric acid, cooled, and titrated as before, giving the chlorine of the chlorides and chlorates together. The amount of perchlorate is deduced by carrying out the process already described by the authors (ANALYST, 1899, xxiv., 26).Examples are quoted showing that sulphurous acid has no effect upon perchlorates. The authors remark that they have analysed a large number of samples of L 6 refined '' Chili saltpetre, and have found between 0.15 and 1.0 per cent. of KClO,, but they have never yet detected the presence of c hlorat es. F. H. L. Erdmann's Reagent for Nitrites in Water. H. Mennicke. (Zeits. angezu. Chem., 1900, 7ll.)-This article describes further minute investigations into the value and delicacy of amido-naphthol-disulphonic acid as a test for nitrites, or as a means of estimating them in water. The results simply confirm the statements already made by Mennicke (this VOI., p. 167) and by Erdmann (p. 81) as to the superiority of the new reagent over starch, Riegler's test, and all the various modifica- tions of the Griess cc-naphthylamine method.Erdmann now employs paramidobenzoic acid instead of the original aniline-p-sulphonic acid, a change which halves the time (now five minutes) required for diazotation, while, as before, the colour attains its maximum in one hour. Fluorescence is very much less noticeable than with any other of the tests; in fact, it can only be seen by examining the upper surface of the liquid with oblique light against a black background. In very extreme dilutions the red colour due to nitrites may be so faint as to be capable of confusion with the fluorescence colour ; while by standing for a long time in an open tube the mixture of water and reagent may acquire a mauve or heliotrope tint.To eliminate the334 THE ANALYST. former source of error, a stoppered tube charged with the reagent and doubly- distilled water (distilled over chalk and permanganate) should be kept for comparison ; whereas the latter will be avoided by working always in closed tubes. With these precautions the utmost limit of delicacy becomes 1 part of NaNO, per 2,000,000,000. I t is worth noticing that in sewage the Erdmann colour is more of a heliotrope than the wine or Bordeaux-red produced by pure solutions of a nitrite ; but if a few drops of strong hydrochloric acid are added to the water the colour becomes normal. The colouring matter always remains in solution, and is therefore susceptible of measurement, even if the liquid contain as much as 0-025 gramme of NaNO, per litre.Various tables are given. P. H. L. Simple and Accurate Method for estimating Dissolved Oxygen in Fresh Water, Sea Water, Sewage Effluents, etc. Letts and Blake. (Chem. News, vol. Ixxxii., pp. 163, 164.)-The authors employ an ordinary separating funnel (332.5 c.c.), which is filled with the water under examination. Seven C.C. of the water are then drawn off and replaced by 5 C.C. of standard ferrous sulphate solution (48 grammes per litre), foll3wed by 2 C.C. of strong ammonia. The stopper being inserted in the funnel, without introducing any air-bubbles, the contents are mixed by gentle agitatic n, and the resulting greenish-turbid mixture becomes darker in colour as the oxygen absorption progresses. After fifteen minutes the funnel is inverted and about 8 C.C.of dilute (50 per cent.) sulphuric acid are run in through the tube in order to dissolve the iron hydrates ; the clear solution is then transferred to a porcelain dish and titrated with permanganate or bichromate (the latter giving b2tter results with s:a water and sewage effluent), preferably of such strength that 1 C.C. = 1 C.C. of dissolved oxygen at 0" C. and 760 mm. c. s. The Quantitative Estimation of Ozone. 0. Brunck. (Berichte, 1900, xxxiii., 1832-1842).-The method most commonly employed for the estimation of ozone consists in titrating the iodine liberated by the gas from a neutral or acid solution of potassium iodide. As many have failed to obtain reliable results by this method, the author has made experiments to determine the cause. He finds that when a neutral solution of potassium iodide is used, the quantities of ozone found are from 50 to 60 per cent. lower than with an acid solution. By using an acid solution of potassium iodide the author states that reliable results are obtained, and that the only source of error is the decomposition of the hydriodic acid if the solution be concentrated; and this may be allowed for by a blank determination. Either sulphuric or acetic acid may be used, but it is advisable to always employ the calculated quantity. I n testing ozonizers, the most suitable method is to pass the current of gas through the acidified iodide solution for a given interval of time, or when frequent estimations are required, a proportional side current, as proposed by Rabe, may be employed. The most suitable strength in most cases for the iodide solution is one-fifth normal, and after the absorption an aliquot portion should be titrated with i+G N. thiosulphateTHE ANALYST. 335 solution. Nitrous acids are best removed by washing the gas with sulphuric acid, which, unlike the potassium hydroxide solution advocated by Cossit, does not attack the ozone. C. A. MI.

ISSN:0003-2654    

DOI:10.1039/AN9002500325

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

THE ANALYST. 335 APPARATUS. A n Apparatus for measuring Gas under Constant (BUZZ. SOC. Chim., 1900, xxiii., 2S8-291.)-The apparatus shown in the figure was devised with the object of measuring the increase of pressure in a closed vessel caused by the evolution of a gas in the course of a chemical reaction. I t consists of a glass vessel, the neck of which has a side tube attached to a mercury manometer of narrow gauge. A tube of special construction terminating in a graduated pipette is fitted into the neck of the flask, and this tube is closed by a stopper, which is in the form of a hollow key, with an opening in its side, which can be turned so as to coincide with a corresponding opening in the pipette. When the key is thus turned the liquid in the pipette runs out, being replaced by the air in the flask.The capacity of the apparatus is determined once for all by weighing it empty and filled with water. I n using the apparatus it should be immersed in a water-bath at the temperature of the room to insure that the initial and final temperatures are the same. The amount of the gas disengaged (reduced to 0" C. and -,in 760 m.m.) is found by the formula X = which t is the temperature of the water-bath, 72 the excess of premure measured, and the last part is to be found in gas-reduction tables. If the apparatus is constructed so V h 760 l + a t as to hold 76 c.c., then - - ' L expressed l + u t in millimetres will Volume. M. A. Job. J d give x directly in cubic centimetres. sermination of carbonates, carbides, sulphides, ammonium salts, and urea.The apparatus is recommended for the de- C. A. &l. Platinum and Brass Electrodes for Analytical Purposes. H. Paweck. (Chem. Zeit., 1900, xxiv., 855.)-This article consists partly of a claim for priority over Winkler in his advocacy of platinum gauze cathodes for electrolytic analysis (ANALYBT, 1900, xxv., 55). Paweck, however, prefers a disc-shaped cathode made of wire 0.15 millimetre in diameter, 10 meshes per centimetre, about 30 square centi- metres in total area,, and with a 1.5 millimetre platinum wire fixed normally to it to serve as a handle and connecting piece. Such a cathode only weighs about 5-5 grammes,336 THE ANALYST. and is therefore cheaper and more convenient than Winkler's gauze cylinder. As anode a perforated disc of platinum foil 6 centimetree in diameter may be employed.Perfectly good results can be obtained in the deposition of copper, zinc, mercury, etc., by using a cathode of brass wire made exactly as above, a similar electrode constructed of platinum serving as anode. Ten grammes of copper may be deposited by working with a current of 1 to 1.5 amphres at 3 volts at a temperature of 30" C., allowing the action to proceed all night. Copper in white cast-iron can be conveniently determined by treating the original solution with sulphuretted hydrogen, dissolving the precipitate in a little nitric acid, diluting suitably, and electrolyzing with a current of 0.2 ampere at 2.2 volts, electrodes 2 centimetres apart. F. H. L. Apparatus for the Determiantion of Ammonia in Water and of Nitrogen by the Kjeldahl Method.R. S. Westoo . (Joum. Anzer. Chem. SOL, 1900, xxii., 468.) -The apparatus is so arranged that the distilling-flask and the receiver can both be got at from in front, The condenser-tank is inclined so as to bring the lower end well forward, as shown in figure. Each distillation-flask is sup- ported by a ring, which is clamped to a separate upright rod. A Bunsen burner is supported beneath each flask from the same rod. The upright rods are fixed to a horizontal support. At the bottom of the condenser-tank is a gutter to carry off moisture condensed from the atmosphere. There is also a, swinging gutter to carry off the distillate whilst the apparatus is being boiled out ready for a determination. A. M. g/DE L-LEVAT/ON An Asbestos Air Bath. 0. Bottcher. (Chem. Zed., 1900, xxiv., 794.)-This piece of apparatus is suggested as a substitute for the water- or sand- bath used in evaporations; it is very simple and cheap, and is very economical in gas. It consists of a plate of asbestos 1-5 millimetre thick, its length and breadth being adjusted according to circumstances. Centrally on the plate is laid a ring of asbestos, 3 or 4 rnillimetres thick in its walls, 30 to 40 millimetres wide (i.e., high), and of a diameter suitable to the flask or basin to be supported. The apparatus is heated with a Bunsen or an Argand burner, and if it be desirable to maintain the temperature of the bath at one particular point, a small hole may be punched in the ring, through which a thermometer is inserted. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9002500335

出版商:RSC    

年代:1900

数据来源: RSC