摘要:

ON THE COMPOSITION OF MILK AND MILK PRODUCTS. BY DR. P. VIETH, F.C.S. Read at the Meeting, Feb. 9th, 1887. THIS is the sixth time that I bring before you what may be called an annual report on the work done in the laboratory which is under my charge. I f the yearly repetition of statements of a very similar character may appear to some unnecessary and tedious, others, I hope, will find them increasing in value with the extension of the period which they cover. In order to avoid going again over the same ground, I shall not speak on the circumstances under, and the purpose for, which the samples were taken, but refer you, with regard to these points, to former communications. (THE ANALYST, VIT. p. 53, VIII. p. 33, IX. p. 66, X. p. 67, and XI. p. 66.) The total number of analyses made during the year 1886 is 18,862, of which 17,269 are analyses of milk, 1,082 1, 1, 9, cram, 355 ,, ,, ,, skim milk, 34 ,, ,, ,, buttermilk, 27 ,, ,, ,, butter and butter fat, 48 ,, ,, ,, milk preparations for infants and invalids, 24 ,, ,, ,, sundries.10 9 , 99 $9 ch-0, 13 9 , ?9 9, water,40 THE ANALYST. Of the milk samples 12,181 were taken from the railway churns on their arrival in the dairy, while 4,135 were taken by the inspectors employed by the business, from the men, when delivering the milk to the customers. Of all these samples specific gravity and total solids were determined, and the percentage of fat calculated from these two items, using Fleischmann’s formula (THE ANALYST, XI. p. 6s). The monthly averages of the results are contained in the following table :- Yearly Average .. AVERAGE COMPOSITION OF MILK. 1.0322 1886. ~ January .. February March . . April .. May .. June .. July . . August . . September October . . November December .. . . . I .. .. .. .. .. .. .. .. .. SAMPLES TAKEN. ON ARRIVAL. -___- Spec. Grav. 1.0322 1.0322 1.0323 1.0321 1.0323 1.0322 1.0318 1.0319 1.0321 1.0321 1.0322 1.0324 Total Solids. 12.87 12.83 12.78 12-75 12-so 12-78 12-67 12.77 12.98 13-26 13-32 13.27 12.92 --____- Fat. 3.77 3.73 3.69 3-70 3.71 3-70 3-69 3.74 3.89 4.1 1 4.14 4-06 3.83 Sol. n. f. 9.10 9.10 9.09 9-05 9.09 9.08 8-98 9.03 9.09 9.15 9-18 9.21 9.09 ON DELIVERY Total Solids. 12-78 12.82 12.74 12.71 12.79 12-74 12-67 12.77 12.93 13-09 13.15 13-13 12.86 Considering the circumstances under which the samples were taken, the differences between the two series must be looked at as very insignificant. In all the samples of milk, which were not mere control samples, the fat was determined gravimetrically, employing what is known as Soxhlet’s, or the plaster of Paris, process; in all there were 550 fat extractions made in this manner, which, however, do not relate to milk exclusively, but also to cream, skim milk, etc.In addition to the two instances, which I have brought under your notice last year, with regard to the composition of ice formed in milk (THE ANALYST, XI. p. 68), I am in the position to-day to give you two more illustrations of what takes place when milk freezes. Milk, which arrived in a partially frozen state, was strained, the ice melted, the quantities of liquid and frozen part ascertained, and samples of each analysed with the following results :-THE ANALYST.41 1886. SAMPLES TAKEN. - Before sent out. On delivery. i - I January February March . . April .. May .. June .. July . . August September October November December .. .. .. .. .. .. a . . . . . .. .. .. .. . . .. .. * . .. .. . . .. . . .. .. .. .. .. .. .. . . .. .. .. .. .. .. .. .. . . .. .. . . .. .. .. .. .. .. . . . . .. .. .. .. .. .. .. .. .. .. I ~ I I I 44'3 per cent* Yearly Average . . .. .. . . I 44.2 per cent. I The rather large differences, which occur between the two series of samples, must be assigned to various causes : firstly, absolute correctness cannot be expected from the mode of calculating the fat ; secondly, the consistency of tho cream makes thorough mixing and drawing real average samples rather difficult ; and thirdly, the two kinds of samples do not exactly correspond with each other, the samples taken before sent out referring to morning and afternoon cream, while the samples taken on delivery refer * By difference.42 THE ANALYST.to afternoon cream only. The morning cream being handed over to the men, and by them to the customers in sealed cans, taking control samples is not only superfluous, but impossible. Calculating the fat in cream from the total solids, in the manner mentioned, has in my hands always given very satisfactory results, agreeing with the results arrived at when extracting and weighing the fat in far the larger number of cases, within *Ei per cent.An addition of milk or water to cream, which does not alter the normal relation between fat and solids not fat, does not interfere with the calculation. In cases, however, where the relation between fat and non-fatty solids has been disturbed, the table for calculating the fat is not applicable; this is the case, for instance, with clotted cream. Of this preparation twenty-one samples were submitted to analysis, and found to be of the following composition :- COMPOSITION OF CLOTTED CREAM. Limits. Water .. .. .. . . 32.59 to 42013 Fat . . .. .. .. . . 50.36 to 61.43 Proteids and Sugar . . .. . . 4-61 ,, 8.93 Ash .. .. .. .. -42 ,, 077 For the determination of water, fat, and solids not fat, Average. 36.1 1 57.36 6.01 -52 in products containing a very high percentage of fat, such as clotted cream, cream cheese, and butter, I am in the habit of using a method, which is virtually the same as the flask method proposed by Mr.Carter Bell, of Manchester, for the analysis of milk. About 5 grms. of the material are introduced into a conical flask, and dried to constant weight in an air bath at looo C., the fat is thoroughly washed out with ether-an easy task, where so much fat is present- and the solids not fat, dried again and weighed. For the determination of the ash, a separate sample is taken, dried, and ignited. In 74 samples of separated skim-milk, the fat was determined and found to amount to from -14 to -42 per cent. in 71 samples, while in 3 samples there were -55, *62, and 063 per cent. of fat present respectively.The composition of 19 samples of butter varied between the following limits :- Fat .. .. .. .. , . 82-33 to 88.95 average 85.37 Water . . .. .. .. . . 10.82 ,, 15.94 ,, 12.93 Proteids, etc. .. .. .. .. -08 ,, 3-20 ,, -9 7 Ash .. .. .. .. .. -02 ,, 2 73 ,, -74 - Insoluble fatty Acids . . .. . . 87.60 to 89.30 ,, 88.33 When the clarsed fats were treated according to Reichert’s method from 12.2 to 15.0, and in average, 14.0 cc. decinormal potash were required to neutralise the distillate. In butter-fat about one year old and bleached by the action of air and light, the insoluble fatty acids were reduced to 84.03 per cent., and 15 cc. decinormal potash were required to neutralize the distillate from 2.5 grms. Some time ago I have made you acquainted with the composition of an English cream cheese, containing an exceedingly high percentage of fat.(THE ANALYST XI. p. 163). Perhaps it might interest you, if I give you the analysis of another cream cheese made according to a French recipe : COMPOSITION OF FROMAGE GERVAIS. I. 11. 1x1. IV. Water . . .. . . 47.94 45.69 42.07 33.57 Fat .. .. . . 43.76 45-96 48-41 58.58 Casein, etc. .. * . . . 7.49 7160 8-77 7.1 4 Lwtic Acid. . .. . . -29 03 1 .zg 9 5 Ash, soluble . . . . 4 6 .oci -0 9 -04 ,, insoluble . . .. .4 6 -3 8 -44 *42THE ANALYST. 43 d Fat. Caseine $ 5 Q) I The differences in composition are chiefly due to the different ages of the cheese, No I. and 11. being quite fresh, while No. 111. was one, and No. PV. two days old when analysed. The average composition of koumiss and other milk preparations for infants and invalids, calculated from analyses made in 1886 and preceding years, is given below.COMPOSITION OF MILK PREPARATIONS FOR INFANTS AND INVALIDS. Ash. 3 m' 2 ; 34 o o Lactic 55 Acid, Sugar. Remarks. gFu Soluble ';:!'- - Water. 88.90 90 35 90.57 87.55 88 39 88-62 89-74 90.63 91-07 92-24 92.38 92-55 91-87 92-26 93-52 4lcohol -1 5 *94 1 *04 -29 -97 1 0 5 *30 1.03 1.38 FULL KOUMISS. 1.35 2.01 *30 034 *34 1-36 1 1.96 1 023 1 *53 1 -96 1.38 I 1.88 *20 I *77 1.40 6.03 3.10 2.18 MEDIUM KOUMISS. 1.54 1-46 043 048 068 6.80 1-56 1-40 076 1.20 4.70 1-58 1 1.30 1 :;: 1 9 7 1 1.67 1 3.90 DIABETIC KOUMISS. -28 -51 2.19 030 036 *75 ::; 051 1 2.05 1 :4," 1 :;: 1 1:; -22 *34 2.32 008 032 006 -45 1 033 1 2.17 I 9; I : 1 *31 -57 *33 2.03 056 -52 2.13 RUSSIAN KOUMISS. A~TIFICIAL HUMAN MILK. 7.48 5.52 4.34 2.78 2.42 1-64 3-95 3.08 2.45 N.B.-In tbe anaIyses of the various kinds of koumiss, the carbonic acid present has not been taken into account.44 THE ANALYST. With regard to samples which come under the head of “ Sundries,” I wish only to mention that I have examined a number of the powders which are so widely advertised and recommended as milk preservatives, and invariably found them to contain boracic acid. A liquid called “ Anti-Bacterion,” and recommended for cleansing purposes, consisted of a twenty per cent. solution of impure aluminium sulphate.

ISSN:0003-2654    

DOI:10.1039/AN887120039b

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年代:1887

数据来源: RSC

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44 THE ANALYST. ON THE ESTIMATION OF GLYCERINE I N FATS. BY OTTO HEHNEE. Read at the Meeting, Fe6ruary 9th, 1887. IN the publication of the principle upon which the method to be described in the follow- ing paper is based, I have quite recently been forestalled by L. Legler ( ANALYST, January 1887), and I, therefore, cannot lay any claim to originality. But as I operate in a manner quite different fram that adopted by Legler-his process being only applicable to some- what concentrated glycerine liquor, whilst I am enabled t o determine the glycerine in even the most dilute solutions-I venture to lay a description of it, and of results obtained, before the members of the Society. A portion of my investigation is, further- more, of general importance, and concerns all methods of glycerine estimation, since it treats of the question of the volatility of glycerine with aqueous vapour.Glycerine decomposes, on treatment with bichromate of potassium and sulphuric acid, into carbonic acid and water. Legler weighs the carbonic acid, or rather the loss of carbonic acid, in an ordinary carbonic acid apparatus. Messrs. Cross and Bevan (Chmicd News, Vol. 56, p. 2) measure the volume of the gas evolved. It is evident that both these modifications require limited bulks of fluid, and, there- fore, exclude the estimation of glycerine in very dilute solutions, such as are obtained in the analysis of fat-tho washings, in fact, of the insoluble fatty acids. The process which I have described (ANALYST, XII, February) for the estimation of methyl in the presence of ethylalcohol, and which consists in the measurement of the quantity of bichromate reduced, is, as I hope to show, particularly suitable for the analysis of such washings.One part of glycerine requires, for complete oxydation, 7.486 parts of potassium bichromate. Solutions reqzci~ed.--( 1.) Bichromate, cmtaining in each litre about 80 grammos of bichromate and 150 C.C. of strong sulphuric acid. The exact value of the solution should be ascertained by titration with solutions of known weights of iron wire. 2. Ferrous and aamonia aulphate containing about 120 grms. per litre. 3. Bichromate ten times more dilute than the above. The ferrous solution is exactly standardised upon the chromate solution, and the glycerine value of the chromate (contents of K,C,O, divided by 7,486) is calculated.The chromate solution used in my experiments standardised as follows :- 2.8412 grms. iron-wire = 2.8327 pure iron, required 35.94 C.C. bichrome. 1 C.C. = 2.7078 grms. iron-wire = 2.6997 iron used 32.3 c.c., bichrome 1 C.C. = *07344 007333 bichrome, or ,009796 glycerine.THE AN BLY ST. 45 bichrome or -009810 glycerine. Average 1 C.C. bichrome = -07338 grms. bichrome or *009803 glycerine. Test ~~~erisltents.-Glycerine, specific gravity 1.2572, containing, according to Lends tables, 95.55 per cent. of pure anhydrous glycerine-was taken, a solution of 12.5798 grme. per litre, corresponding to 12.0200 grms. of pure glycerine, being used. 26 C.C. of this eolution, equal to *3005 glycerine were taken in each of the following experiments.25 c.c heated with 40 C.C. bichromate, without further dilution for two hours to Rear the boiling point : 30.41 C.C. bichromate were consumed, corresponding to 9981 grms. glycerine, or 99.2 per cent. of the glycerine taken. 25 c.c., heated with bichrome and 25 C.C. strong hydrochloric acid for one hour, consumed 31.16 C.C. bichrome, equal to 30546 grms. or 101-6 per cent. 25 c.c., diluted with 600 C.C. of distilled water, reduced in three hours 23.93 C.C. bichromate, equal to 023458 grm. or 78.1 per cent of glycerine. The same quantity, diluted with 500 C.C. of water, plus 25 C.C. strong hydrochoric acid, heated for one hour, reduced 22.3 C.C. bichrome, indicating ~2186 grms., or 72.7 per cent. 25 c.c., diluted with 600 C.C. of water, plus 25 C.C.sulphuric acid, consumed in one hour 29.34 C.C. bichrome, = 02876 grms., or 95.7 per cent. of the glycerine taken. Conditions the same as in the previous experiment, only the heating continued for two hours. Bichromate consumed 29-89 C.C. = *2930 grms., or 97.6 per cent. of glycerine taken. 25 C.C. were diluted to about 300 c.c., the solution evaporated to about one-half upon the water bath, and then heated with 25 C.C. strong sulphuric acid and chromate. After two hours 30.54 C.C. bichromate were found to be reduced, corresponding to -2994 grms. or 99.6 per cent. of glycerine. In a similar experiment the diluted solution was vigorously boiled down over the naked flame to about one half (the basin being, of course, covered with a dock glass to prevent loss by spurting), and heated for two hours with sulphuric acid and bichromate.Found -2961 grms. or 98.5 per cent. of the glycerine taken. In a precisely analogous experiment 10 C.C. of strong alcohol were added to the water, before boiling, over the naked flame. After two hours 30.33 C.C. of chromate were reduced, equal to -2973 grms. or 98.9 per cent. of glycerine found. The alcohol experiment repeated, but the fluid concentrated on the water bath, an amount of bichromate was reduced corresponding to 107.6 per cent. of glycerine. An odour of aldehyde was perceptible during the oxidation. Deductiom-From these test experiments the following conclusions can be drawn. 1. In a fairly concentrated solution glycerine is quantitatively oxidised by acid 3. In a very dilute solution the oxidation is not complete even after many hours’ 3.The addition of hydrochloric acid does not materially help oxidation. 4. In solutions containing about 10 per cent. of strong sulphuric acid the oxidation is complete after two hours, even in exceedingly dilute solutions (06 glycerine per lOOOof fluid). 6. .From such dilute solutions, glycerine does not, as is commmzly asmcrned, volatilise 0% concentrating the fluid, be it on the wates. bath OT over the nu7cedJEame. bichr oma te. heating.46 THE ANALYST. 6. Shonld alcohol be present it is completely volatilised by vigorously boiling the fluid dJwn to one half, but not on the water bath. The non-volatility of glycerine from dilute solutions may further be readily demonstmted by distilling from a large retort 500 C.C.of water, containing about *3 grms. of glycerine, catching the first 250 C.C. of the distillate. This distillate does not, even on heating, decolourise more than’a few drops of a dilute permanganate solution, such as is used in water analysis. Method for Estimating Glyceke in Fats.-Saponify about 3 grms. of the fat with alcoholic potash ; do not drive off all the alcohol, lest glycerine should volatilise from the concentrated solution, but dilute to about 200 C.C. ; decompose the soap with dilute sul- phuric acid, filter off, and estimate insoluble fatty acids as usual. Vigorously boil the filtrate and washings (amounting to about 500 c.c.) in a covered beaker or basin, down to one-half, add 25 C.C. strong sulphuric acid (suitably diluted) and 50 C.C.standard bichro- mate. Heat to near boiling for two hours, and titrate back the excess of bichromate with excess of ferrous sulphate, and ultimately the latter with decichromate using ferricyanide as indicator. Calculate from the chromate consumed the amount and per- centage of glycerine. Finally, I will add a few results obtained on applying the method to a few fats : Olive oil . . .. . . . , 10.26 per cent. glycerine. Cod liver oil . . .. . . . . 9-87 per cent. Linseed oil . . , .. . . . . 10.24 and 10.20 per cent. Butterine . . .. . . , . 10.01 per cent. Butter - 0 .. . . . . 12.40 and 11.96 per cent. Of course, I am fully aware that other substances, should they be present, might reduce bichromnte as well as the glycerine does. The analgous objection applies to Dr. Muter’s and . Mr. FOX’S processes ; I have, however, convinced myself that soluble fatty acids, like butyric, do not act upon bichromate, nor do fatty acids of higher molecular value. The method may not simplicity and rapidity in and soluble fatty acids. be theoretically perfect, but it may commend itself for its cases of fluids which cannot contain anything but glycerine NoTE.--I here correct two errors that have crept into my paper on methylalcohol. Dr. Duprt5 did find -58, not -42 per cent. of methylalcohol, for 10 per cent. of The ferrous sulphate solution employed contains 120, not 240, grammes of iron and methylated spirit. ammonia sulphate per litre.

ISSN:0003-2654    

DOI:10.1039/AN8871200044

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年代:1887

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46 THE ANALYST. A CONVENIENT APPARATUS FOR SUGAR ESTIMATION. BY ALFRED W. STOKES, F.C.S. IN the discussion that ensued on the reading of Dr. Vieth’s paper, Mr. A. W. Stokes, F.C.S., stated that the method he had used to verify the readings of Dr. Vieth’s polariscope, was that described by Mr. Bodmsr and himself in THE ANALYST (vol. X. p. 62). Dr. Pavy’s ammoniacal cupric solution was used. A greatly improved apparatus was, however, employed ; this he exhibited to the Society, We give herewith a drawing ofTEE ANALYST. 47 it,* noting that it may be useful for other colour reactions. It consists of a buretts one, lateral, half of which is of opal glass to show more sharply the divisions, and to mark accurately the centre of the meniscus. india-rubber tubing, a flask of about 150 C.C.capacity. The cork used is of india rubber, with two perforations; into one of these fits a short glass tube, connected with the burette by the piece of tubing mentioned above, and dipping a short wag into the flask, where it is drawn out to a moderately fine point. The other perforation is fitted with a tube leading off to two Woulffe’s bottles, one of which is about one-third filled with water. The tube between the flask and burette is best compressed by the specially-devised screw-tap figured, The ordinary spring-clip brings the fingers too close to the flame to be pleasant ; nor does it allow so regular a succession of drops to fall. Behind the flask, to form a white background, is arranged the half of one of the ordinary white, opal gas-globes. By this white light is concentrated on the flask, and an admir- able background formed. The method of using is described in the paper referred t o above. The results obtained agree very closely with those of the polarhope. From this is pendent, by a short piece of

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DOI:10.1039/AN8871200046

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年代:1887

数据来源: RSC

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THE ANALYST. 47 FURTHER NOTE ON POIVRETTE. BY PROFESSOR J. CAMPBELL BROWN, D.Sc. Read at the Meeting, February 9th, 1887. IN addition to the microscope examination with a Q objective in good daylight, a lower power, such as a 3 objective, with the polariser and analyser placed parallel, and with Klein’s quartz plate or selenite plate, in daylight or strong lamplight, brings the ligneous cells into marked prominence, and enables the counting to be done on a tolerably large field. This does not distinguish between the cortical cells of pepper and poivrette cells. If, however, the quartz or selenite plate be removed, and the polarising and analysing Nicol prisms crossed, any power from a 3 to a 4 object glass in good lamp-light will show the poivrette cells glittering with a bluish white light, while the cortical cells of pepper, even if bleached, show a yellowish-white glitter.The final examination should be made with a i, or better Q, in good daylight without polariser. * By kindness of Editor of 66BtgZi& Mechania.”48 THE ANALYST. ~~ Following up a hint received from a friend, I have found the following an easy method of demonstrating the presence of poivrette to an unskilled person. Boil a portion of the sample in water to which a little caustic alkali has been added, dilute the thin mud with much water, allow to stand, and pour off the liquid from the remaining solid particles, and wash two or three times by decantation. The yellow particles are poivrette, the dark particles are husk. I f any particles of bleached husk cells slightly resemble the poivrette, they may be distinguished by their softness and by the microscope. Conclusion of the Society’s Proceedings. Liverpool, 4th February, 1887.

ISSN:0003-2654    

DOI:10.1039/AN8871200047

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年代:1887

数据来源: RSC

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48 THE ANALYST. ESTIMATION OF MANGANESE BY PRECIPITATION WITH MERCURIC OXIDE AND BROMINE." BY C. MEINEKE. IN his excellent treatise on the separation and estimation of manganese Volhard gives a method for the precipitation of the same by means of mercuric oxide and bromine from its nitric or sulphuric acid solution. His process, however, has attracted little notice. He described and explained it as follows :-The precipitation of manganese as peroxide by chlorine or bromine is accompanied by the formation of hydrochloric or hydrobromic acids, which would again dissolve the peroxide if no alkaline acetate were added. The liberated acetic acid is, however, not strong enough to prevent precipitation of other oxides, for instance, manganous oxide. I f , however, a solution of manganous sulphate or nitrate in nitric acid is heated with argentic nitrate, and mixed with chlorine or bpomine, all the manganese separates as peroxide. It, of course, contains argentic chloride or bromide, but is perfectly free from other metals.A solution of mercuric chloride evolves no chlorine when heated with sulphuric acid and manganic peroxide. Instead of using silver me may therefore use the mercuric nitrate, which has the advantage of not forming an insoluble chloride. The not too dilute solution of the manganese solution is mixed with nitric acid and heated to boiling with a little pure mercuric oxide, then mixed with chlorine or bromine water till the fluid turns reddish. This is, however, not always readily noticed. To see if precipita- tion is complete allow to settle, and see whether more chlorine water will produce any further turbidity.A solution containing in 60 C.C. about -5 grm. of manganous sulphate, boiled with 20 C.C. nitric acid and about 1 grm. of mercuric oxide, is generally completely precipitated by the bromine in twenty minutes. I f copper, cobalt, nickel, zinc, alkaline earths, or alkalies were present the precipitate must, after filtering off, be redissolved and once more precipitated. The peroxide is either ignited and weighed as manganoso-manganic oxide, or dissolved in hydrochloric acid and evaporated with stzlphuric acid, and finally weighed as manganous sulphate. Volhard gives the following test analysis : 50 C.C. of a solution of manganous sulphate, containing 9615 gramme, to which was added *2 gramme of cobaltous sulphate, gave in two experiments ,2618 and 4610 gramme of manganous sulphate, which proved to be perfectly free from cobalt.My own experiments have been conducted with weaker solutions, such as would * Repertorium der Anal. Chem.THE ANALYST. 49 fairly represent a filtrate obtained during commercial analysis. The solutions measured about 250 C.C. and contained -0933 and -3732 manganese. After acidifying and adding mercuric oxide, then boiling with bromine, the liquid remained at first quite clear, and only after prolonged boiling a slight turbidity formed. I f I added coarsely powdered mercuric oxide this got coated with manganic peroxide. However, the separation was not complete until a real excess of mercuric oxide was added, and the acid completely neutralised.Further experiments showed conclusiveIy only mere traces of zina are co-pre- cipitated with the manganese, but it is of the greatest importance that the mercuric oxide and the bromine are free from iron ; then this metal has a great tendency to combine with the peroxide, and even strong nitric acid fails to remove it. To exactly ascertain the quantity of co-precipitated zinc I took 15 c.c of solution of manganous nitrate, containing -0933 of the metal, added some zinc nitrate, diluted up to 250 c.c., heated to boiling, and added lixiviated mercuric oxide and bromine water until the liquid appeared faintly red. After decolourising with a few drops of spirit the precipitate was filtered off and washed. A portion of it obstinately adhered to thesides and was dissolved in a little hydrochloric acid, and treated with bromine water and ammonia.The precipitate was collected and washed separately, but then added to the chief precipitate. The following results were obtained :- The whole was weighed as manganoso-manganic oxide. First experiment. Plenty (but unknown quantity) of zinc nitrate. Impure manganoso-manganic oxide . . *I332 ,, zinc oxide . . .. .. *0015 Including ferric oxide , . .. .. *0020 Difference . . .. .. . . *1297 =*0934 pure manganese. Impure manganoso-manganic oxide . . *1348 Including ferric oxide . . .. .. -0024 Difference . . .. .. . . -1304 = *0938 manganese. Second experiment. After addition of 7.5 grammes zinc nitrate. ,, zinc oxide . . + . .. -0020 I n the meanwhile I had noticed the precipitate was scarcely affected by dilute nitric acid.I n ahother experiment I therefore strongly acidified with nitric acid and kept boiling for five minutes, then neutralised the free acid. As the solution kept reddish no manganese could be in solution (except the trace of the permanganate). If it had turned colourless I would have been obliged to add a little more bromine and mercuric oxide. Used 30 C.C. of the same solution and 17.5 grammes of zinc nitrate. Obtained impure manganoso-manganic oxide *2630 Including ferric oxide ... L.. .. 00015 Difference .. .. .. . . -2607 = el877 manganese, ,, zinc oxide . . ... .. .0008 or 00938 in 15 C.C. The addition of the excess of nitric acid, therefore, practically prevents the co-pre- The same manganese solution waB used for further experiments, which were made to cipitation of the zinc.50 THE ANALYST. settle the question, whether the manganese was really precipitated as pure peroxide, and could be estimated by determining the quantity of oxygen it contained. The best reducing agent for manganic peroxide appears to be oxalic acid, as this can be got absolutely pure, keeps for any length of time if mixed with a ntineral acid, and can be accurately titrated with permanganate.When I treated the precipi- tated peroxide, first with nitric acid, to remove excess of mercuric oxide, and then with oxalic acid, I was disappointed to notice a white precipitate, which gradually dis- appeared on adding the permanganate, but still proved a nuisance. This compound is mercuric oxalate, manganic peroxide chemically combining with some mercuric oxide.The sulphuric acid dissolves this, and the oxalic acid now precipitates the insoluble oxalate. And there is not the slightest objection to this if this acid is not used in excessive quantity. For every one gramme of oxalic acid I add 2 C.C. hydrochloric acid of 1.19 sp. gravity. I n titrating back the excess of oxalic acid I add 10 C.C. dilute sulphuric acid (1 - l), and 20 C.C. of a 5 per cent. solution of manganous sulphate. The end reaction is then very distinctly visible. The precipitated manganic peroxide was carefully rinsed off the filter, back into the beaker, and the filter was moistened with some of the oxalic acid (which was almost super- fluous), then in turn well washed with water. In two experiments the following results were obtained :- 15 C.C. of the solution containing 00933 gramme gave a precipitate absorbing *2152 oxalic acid =no939 gramme. 60 C.C. of the Same solution =*858 oxalic acid= *3745 gramme. It is, therefore, plain the manganese really precipitates as pure peroxide, which I therefore mixed the oxalic acid with hydrochloric acid instead. further test analyses will prove. (To be continued).

ISSN:0003-2654    

DOI:10.1039/AN8871200048

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年代:1887

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50 THE ANALYST. NITRITES AND NITRATES. BY A. PERCY SMITH, F.C.S., F.I.C., RUGBY. IN the C7bemicaZ News for January 23, 1885, there is a paper, by Mr. R. Warrington, on the various methods of detecting nitrous acid, and he shows that Griess’ napthylamine test is the most delicate of all, being able to detect one part of nitrogen in 100 millions of water. I have lately made some experiments, in order to ascertain whether the total nitrogen, as determined by the copper-zinc couple, agrees with the sum of the separate estimations of nitrogen as nitrites and nitrates. The napthylamine test is one of great delicacy, and requires great care in its application. To 100 C.C. of the water add five drops of a saturated solution of sulphanilic acid, three drops dilute hydrochloric acid, and three or four drops of a saturated solution of napthylamine hydrochlorate; mix, and allow to stand.I n cold weather the water It is made as follows :-THE ANALYST. 51 should be slightly warmed. A pink colour will make its appearance in the liquid, forming slowly or quickly, according to the amount of nitrite present. I n cases of extreme dilution the maximum effect is not developed in less than half-an-hour. Care must be taken not to acidify too strongly, as in such case nitrates give a colour reaction with the napthylamine. To determine the amount of nitrogen represented by the tint, produced, take 10 C.C. of a solution of pure potassic nitrite, containing 0.1 milligram. N, dilute to 100 C.C. with pure water, and apply the test as directed. It will be necessary to make a blank test with the distilled water, which frequently is sufficiently impure to give a decided colouration." It is impossible to take too many precautions respecting the cleanliness of the apparatus employed.On one occasion I used a measuring tube which had been standing on a shelf for some time. I rinsed it thoroughly at the sink, but the colour developed in that tube was three times as intense as that given by the same water in another tube. After cleansing the tube with acid, a fresh determination produced a correct result. The standard nitrite solution is prepared according to the directions given in the ANALYST, vol. TI., p. 38, viz., from silver nitrite decomposed by potassic chloride. I n comparing the intensity of colour in the two tubes it is not sufficient merely to reduce the length of the column of the darker liquid. It is impossible by that means to arrive at any agreement in tint.The darker solution must be poured into a measuring glass, and successive additions of water made, until 100 C.C. (poured back into the comparing tube) equal in tint the 100 C.C. of solution with which it is compared. I estimate nitrates by the phenolsulphonic acid method described in my paper, ANALYST, vol. X., p. 199. I n that paper I have directed five drops of the acid to be used. This amount may be with advantage increased. It is necessary to have liquid enough, when the dish is tilted, to run over the residue left. The dish should, a t the same time, be heated. The ammonia must not be added until theyellow colour is fully developed.In comparing the colour produced with that of the standard solution, it is prefer- able to pursue the same method employed for the nit.rites determination, although it is quite possible to arrive at a correct conclusion by reducing the quantity of the darker liquid. Still, mistakes may be made, owing to difference in distance from the eye, and the amonnt of liquid which refracts the light. It is far the better plan to compare equal volumes. The water I experimented upon contained, by copper-zinc method, 4.316 mg. total N per litre. 200 C.C. were evaporated to dryness in a platinum dish, and gave 3.07 mg N, as nitrates, per litre. Amines form nitro-compounds with great facility. 100 C.C. were tested for nitrites, and gave 1.25 mg.N per litre. ~~ * I have found that ordinary water, kept in an open cistern, is superior to distilled water for this puvose.52 THE ANALYST. f N as N,O, 3.07 ' * 1 N as N,O, 1.25 4.3 2 ,. .. .. Total N, \ 4.316 It is probable that the N205 is in greater, and the NzOs in less than the proper quantity, since it is impossible to acidify nitrous without forming some nitric acid, and the evaporation necessary in the nitrate determination may have an analogous effect. Future experiment must decide how far this is, or is not, the case. Medical officers of health would find the napthylamine test useful to carry with them when inspecting sources of water supply. Three small bottles and a dropping- tube would go comfortably into a waistcoat pocket. The water needs no concentration. The chemicals are inexpensive. The quantity of the reagents used must depend upon the volume of water tested. If a small test tube is used, one drop of each is sufficient. The final result of the astion of sulphanilic acid and u napthylamine upon Azo- a-amidonapt halin-parab en z olsulp honic acid nitrous acid is the formation of N- N The stages of the reaction are :- NH* n (1) The action of nitrous acid on sulphzmilic acid, 'V SO,H gives para~iizobenzolsulphonic acid N = N (2) Tho action of the a napthyhmine on this N = N N -~ N so, NH S0,R N%

ISSN:0003-2654    

DOI:10.1039/AN8871200050

出版商:RSC    

年代:1887

数据来源: RSC

摘要:

THE ANALYST. 53 MONTHLY RECORD OF ANALYTICAL RESEARCHES mro DRUGS. METHOD FOR DISTINGUISHING CASTOR OIL FROM OTHER FATTY OILS. PROF. DR. FINKENER. Chem. Zeit., vol. 10, p. 1,50O.-The experiments were carried out with the object of finding a suitable method for customs purposes. A 100 C.C. glass cylinder of 25 mm. diameter, is provided with a 10 or 60 C.C. mark (measured from the bottom). The oil is run in to the 10 C.C. mark, and the tube is then filled up t o the 60 C.C. mark with spirits of wine (*829 sp. gr.). Absolute alcohol cannot be employed, but at 17.5" C. spirits of wine of .S39 sp. gr. dissolves castor oil in almost every proportion, the other54 THE ANALYST. oils only slightly. The tube is closed, well-shaken, and the mixture examined after standing two or three minutes.But even with 10 per cent. of other oils (olive, sesam, linseed, cottonseed, rapeseed oils) a turbidity is obtained,' at the normal temperature, which does not disappear even above 20" C. Another test tried was the following :-On treating pure castor oil with sulphuric acid, a product (a sulpho-acid) is obtained, whichgives an almost perfectly clear solution with 40 times the quantity of water. On treating other fatty oils (such as sesam or olive oil) similarly, very milky precipitates are obtained. The method is, however, of no good, as mixtures of 80 per cent of castor oil or 20 per cent. of olive or sesam oil, treated similarly, also give almost perfectly clear solutions. Pure castor oil gives a clear solution. F. W. T. K. ESTIMATION OF COCAINE.E. R. SQUIBB, M.D. Ephemeris.-The coca leaves are ground into coarse powder, 20 or 30 meshes to the inch. OF this powder 100 grams. is moistened with 100 C.C. of water, containing 5 per cent. of sulphuric acid, and is packed moderately in a cylindrical percolator, and percolated to 500 C.C. with the same acid water menstruum. This percolation is best done by means of a Sprengle water pump into a flask marked at about 500 c.c., and this amount of percolate will generally exhaust the coca sufficiently, even when the leaves are of the thick Bolivian variety. A portion of the stock of the acid water used is then balanced against a portion of the stock of re-crystallised carbonate of sodium, and it will generally be found that 6 to 6.5 grams. of the crystals are required to saturate 100 C.C.of the acid water. The percolate is then measured off into a large beaker or other similar vessel, and 50 C.C. of kerosene added to it, and the whole well stirred together. Then as much of the crystallised carbonate of sodium is added as would saturate the percolate if it was all acid water, the sodium salt being added little by little with constant vigorous stirring. I n order to precipitate the alkaloid completely, the sodium salt is required in considorable excess, and the difference in acidity between the percolate, with its large percentage of extract, and the acid water gives about the proper excess. The kerosene is very thoroughly and repeatedly stirred into the mixture during four or five hours of digestion, and is then separated by means of a separatory funnel or a small syphon.Then 25 C.C. of fresh kerosene is added to the percolate and the stirring, digestion and separation are repeated twice, making three washings with the kerosene. I f an emulsion should form between the percolate and the kerosene it will lie next above the percolate in drawing this off, and should be drawn off into a separate vessel with the final washing. A little dry filter paper pulp, or a little asbestos or sand stirred into this emulsion will break it up so that the kerosene can be separated completely, when it is added to the larger portion. If the percolate and the kerosene be shaken together, instead of being stirred as above directed, all or nearly all of the kerosene will be made into an emulsion. On stsnding two or three days this emulsion will separate wholly or partially, but as the operator can never tell beforehand whether it will separate completely or only in part, it is better not to wait, but rather to separate it as directed.Then by stirring rather than shaking, the amount of emulsion is reduced to a minimum, and if the stirring be well done, the percolate is washed free from alkaloid, and this latter is practicslly all held dissolved in the kerosene. But ifTHE ANALYST. 55 the operator wants to be assured that he has washed out all the alkaloid from the perco- late, let him add to the latter about two grams. more of carbonate of sodium and 25 C.C. of ether and again stir, or shake and separate. The residue left on the evaporation of this ether should give no cocaine impression on the tongue, nor any saturating power to a very minute quantity of very dilute acid.The 100 C.C. of kerosene holding the alkaloid in solution is then shaken vigorously in a separator three times-twice with 10 C.C. of the acid water, and the third time with 5 C.C. of water. This washes out practically all the alkaloid as sulphate, and leaves the kerosene ready for another assay. To the 25 C.C. of solution of sulphate of cocaine contained in another separator 10 C.C. of ether is added, well ahaken, and then a moderate excess of crystals of carbonate of sodium. After the effervescence, this is well shaken, and the ether separated. The solution is again washed twice with 10 C.C. more of ether each time. All the ether is then collected entirely free from even a fraction of a drop of the solution, in a beaker of at least three times the capacity of the ether.From this the ether is evaporated, and the alkaloid is left in the condition of a light amber-coloured varnish on the bottom and sides. If a capsule be used instead of a beaker, or if too small a beaker be used, the ethereal solution is liable to creep over the edges and be lost. As soon as the beaker is free from the d o u r of ether, it may be weighed, and the tare subtracted will give the weight of cocaine obtained from the 100 grams. of coca. This weight varies, in the writer’s experience, between a, few milligrams., which is called 0. and -898 grms. equal to ,892 P.c., the highest result yet obtained. I f the beaker, with its varnish-like coating, be set aside, there will appear, in a longer or shorter time-generally within five or eix hours- minute centers of crystallisation, and these will slowly extend until within 24 or 48 hours the whole varnish-like coating will be converted into R white crystalline crust. This crystallisation takes place without any discoverable change in weight when the beaker is kept on a balance sensitive to one-tenth of a milligram. W. H. D.

ISSN:0003-2654    

DOI:10.1039/AN887120053b

出版商:RSC    

年代:1887

数据来源: RSC

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THE ANALYST. 55 MONTHLY RECORD OF GENERAL RESEARCHES IN ANALYTICAL CHEMISTRY. CONTRIBUTIONS TO FORENSIC CHEMISTRY. BY PROFESSOR G. DRAGENDORPF. Phai*mac. Zeitschr. f. Russbnd.-The author reports the results of investigations made under his supervision with a number of drugs more or less employed. Detection of Chloral.-Having previously shown that chloral hydrate may be ab- stracted from aqueous solutions by agitation with ether and acetic ether, Dragendorff recammends, based upon the researches of Baron Tiesenhausen, the treatment of urine, first with petroleum-benzin, then with ether, when, on evaporation of the latter solvent, the chloral hydrate is left behind. Other organic mixtures, such as the contents of the stomach, require to be acidulated with diluted sulphuric acid, and macerated for a day with three volumes of strong alcohol ; the filtrate is evaporated spontaneously until the alcohol has been volatilised, when the aqueous residue will yield fat, etc., to petroleum- benzin, and subsequently chloral hydrate to ether.Blood and organs containing much56 THE ANALYST. blood retain the chloral within the coagulum, in which it is best recognized by the production of chloroform on distilling with sodium hydrate. 0.005 gm. chloral hydrate may, by these processes, be readily recognized in from 75 to 100 C.C. of mixture. The most suitable reactions for the recognition of chloral hydrate are the following:- The dry chloral hydrate is warmed with alcoholic soda solution and a little pure aniline ; the odour of isonitril is still distinct, though faint, with 1-60,000 gm.of chloral hydrate. Heat to 50W. the hydrate with 1 or 2 drops of concentrated aqueous potash solution, and a little naphthol ; the blue colour, produced also with chloroform, is re- cognized with 1-24,000 gm. of chloral hydrate. Experiments with animals show that chloral hydrate is rapidily eliminated and transformed into products which, like urochloralic acid, do not show the reactions of chloral hydrate. Detection of Phenol.-Experiments were mado by Dr. Woldemar Jacobson for the purpose of isolatiEg and recognising phenol. The organic mixtures, 100 ccrn., were macerated for a day with 400 ccm. of alcohol, the filtrate was freed from alcohol by dis- tillation at a low temperature and under reduced pressure, the aqueous residue filtered, agitated with a little petroleum benzin for the separation of fat, and then repeatedly shaken with benzol, which solvent WW evaporated in watch-glasses. The following reactions were employed :- Dragendorff’s Method-The residue was left in contact at ordinary temperatures with solution of mercuric nitrate, containing a little nitrous acid j the red colour appears in half-an-hour with 1 phenol in 100,000 mixture.Jacquemin’s Method-Dissolve 3 drops of colourless aniline in 50 ccm. of water, Dilute 5 or 10 drops of this solution with 5 ccm. of water, and add sufficient solution of sodium hypochlorite (1 sodium carbonate ; 1 chlorir,ated lime j 10 water; filter), until a distinct violet or brown colour is produced. Add’of this freshly prepared mixture to the phenol, previously mixed with ammonia, until the liquid is coloured violet or brownish, when in a short time in the preseme of phenol (1 : 50,000) the colour will change to blue, or with less phenol (1 : 100,000) to green.Landolt’a Reaction-Cloe tta and Schsr have shown that the crystalline precipitate with bromine is still obtained in solutions of phenol diluted to the proportion 1 : 100,000. In separating amall quantities of phenol from animal matter, Jacobson obtained amor- phous precipitates with bromine, which, after drying, dissolving in alcohol, and ovapo- rating slowly, yieldsdi the characteristic groups of needles. Minute quantities of phenol are best dissolved in little water, and then exposed to bromine vapours. Detection of ThaZZine.-Blumenbach found that thalline is not, or only in traces, taken up by agitating acidulated aqueous solutions with benzin, benzol, chloroform, or ether, but is dissolved from ammoniacal liquids by these solvents, however only sparingly by petroleum-benzin.Distinct reactions could be obtained by this treatment with 0 001 gm. of thalline in 100 ccm. of urine ; from a similar amount of blood or food- mixture the reactions were faint, but with 0.005 gm. were distinct. The green colour produced by ferric chloride is distinct in solutions 1 : 10,000, and still recognisable in dilutions 1 : 100,000. A green colour is also produced by gold chloride, silver nitrate,THE ANALYST. 57 chromic acid, chlorine water, and mercuric nitrate, and in acid solutions also by chlori- nated lime and potassium ferrocyanide. Iodine colours it dark brown, then dingy green ; platinic chloride yellowish-green ; and a red colour is produced by warm fuming nitric acid, by sulphuric and nitric acids, and by sugar and sulphuric acid.The solutions of thalline, if not too dilute, yield precipitates with the usual reagents for alkaloids. Given to animals by the stomach or subcutaneously, thalline caused a dark coloura- tion of the urine, which contained very little unaltered thalline, but after acidulation yielded to benzin, benzol, etc., a derivative, coloured green by ferric chloride; after precipitating the phosphoric acid with a few drops of ferric chloride the filtrate yields with more ferric chloride the red colour observed by Jaksch. Detection of AIzt@yrirte.-Blumenbach recommends treating the aqueous infusions with petroleum-benzin, and after the addition of ammonia with benzol, chloroform, or amylic alcohol, when very distinct reactions will be obtained with 0.01 or 0-005 gm., and faint reactions with 0.001 gm. of antipyrine in 100 ccm.of organic mixtures. The alkaloidal reagents produce precipitates in not too diluted solutions of anti- pyrine, and ferric chloride gives in neutral solution 1 : 1,000 a dark brown colour, 1 : 10,000 a light brown, and 1 :50,000 a light yellow colour. Fuming nitric acid colours dry antipyrine dark red, and in liquids green, recopisable in solutions 1 : 10,000. The solution, mixed with concentrated sulphuric acid and warmed with a little fuming nitric acid, becomes deep red.Observations with animals prove that antipyrine is rapidly absorbed, and for the next eighteen to twenty-four hours may be detected in the urine; but only for a few hours in the different organs. On the other hand, antipyrine was found, after putrefac- tion of two weeks, in all organs of animals that had been killed about two hours after swallowing the chemical, or receiving it by hypodermic injection. W. H. D. ESTIMATION OF PHOSPHORIC ACID IN THOMAS’ PHOSPHATE. G. LOGES. Repert. Anal. Chemie, No. 6, 1887.-The increasing demand for Thomas’ slags for manure causes large numbers of mmples to be sent for analysis. The usual process is the well-known molybdate method; but the preliminary treatment of the slag varies in many laboratories. Either oxidising agents are used-fusion, with potassic chlorate and sodic carbonate ; treatment with nitric acid or nitrohydrochloric acid; or non-oxidising bodies, such as hydrochloric acid.The use of oxidising agents gives a too high result, as the farmer wants to know the amount of real phosphoric acid, and does not attach any value to the ferric phosphide, notwithstanding the latter gradually oxidises to ferric phosphate. Even by using non-oxidising materials, a small portion of the phosphide oxidises to phosphate, but the results are much nearer the truth. The process, as it stands now, is inconvenient, as it requires the separation of the silica and the expulsion of the hydrochloric acid by nitric acid. The removal of the silica does not seem so important, but the hydrochloric acid must, it seems, be completely driven off.The use of concentrated sulphuric acid much simplifies the analysis, as no evapora tion is needed, and it gives results accurately corresponding with those obtained by the hydrochloric acid method. The details are as follows :-58 THE ANALYST. Ten grammes of the phosphate flour are moiBtened in a porcelain dish, with as little water as possible, and then mixed with dilute sulphuric acid (1 - 1) until all the lime has become gypsum, and carbonates and sulphides are completely decomposed. The mass, which becomes somewhat solid, is now slowly mixed, with constant stirring, with 50 C.C. concentrated sulphuric acid. The action is very energetic, but there is little risk of loss by spurting. The dish is now put on a sand-bath, and heated for about half an hour, with occasional stirring, until a thin paste has formed, The temperature must be high enough to cause fumes of the sulphuric acid.The gypsum partly dissolves as acid salt, and but few black particles are noticed, probably metallic iron. After cooling, the mass is diluted with water, and introduced in a litre flask half filled with water, when a large quantity of calcic sulphate separates out, After making up fo the mark, and filtering, 50 C.C. are taken for precipitation with the molybdate. It is not necessary to oxidise any ferrous iron, tw there is already sufficient nitric acid in the molybdate solution, and if a blue colour forms by reduction of the molybdate, it is soon destroyed on warming. The presence of free sulphuric acid does not in the least inter- fere. From 100 C.C. of a solution prepared as described, only a0006 gramme of silica could be recovered, and as this looked brownish, it is doubtful whether it was silica a t all. TEST ANALYSES. Sample. Hydrochloric acid method. Sulphuric acid method. Difference. Silicic acid can only be present in traces. . . . . . . . . . . . . . . . . * . .. * . . . . . * . .. .. .. * . 23.02 19.66 23.1 7 19.76 15.62 19.66 15.68 19.37 18.32 . . .. .. .. . . . . . . .. .. .. .. . . ,. . . .. . . . . . . 23.1 1 19.71 23.36 19-71 15.70 19.77 15-60 19-33 18.47 .. .. .. .. .. .. .. .. .. .. *09 .. *05 * . -19 .. -0 5 .. -08 .. -1 1 .. -08 .. -04 . . -15 I n conclusion, the author states, this process has been used in his laboratory for some time, and has considerably lessened the labour of the analyses. L. DE K. APPOINTMENT. Dr. WILLIAM JOHNSTONE, F.I.C., F.C.S., has been appointed Public Analyst for the Borough of St. Ives, Cornwall.

ISSN:0003-2654    

DOI:10.1039/AN8871200055

出版商:RSC    

年代:1887

数据来源: RSC

摘要:

58 THE ANALYST. CORRESPONDENCE. [The Editor is not in any way responsible for opii~ims expressed by his correpm&de!uts.] To the Editor of the ANALYST. SIR,-Could our medical friends give us some information in reference to a disease which has lately broken out among Analysts, and which threatens to spread rapidly? It is, apparently, infectious and incurable, and attacks only certain constitutions. It first shows itself by the eruption of the two consonants Dr. on the note headings of the individuals affected; it gradually spreads upon their door-plates, and ultimately finds its way as an appendage to their signatures. The period of incubation varies much. I have heard of a case in which this stage lasted some years. In the earlier stages some of the patients blush when spoken to, but in the more aggravated cases the blush is absent. Am I right in believing the disease to be a variety of the American doctor fever ? And should not, seeing the virulent character of the affection, the individuals who suffer from it be subjected to disin fection and quarantine ?-I remain, sir, yours faithfully, HYDROXYL. -

ISSN:0003-2654    

DOI:10.1039/AN8871200058

出版商:RSC    

年代:1887

数据来源: RSC