摘要:

THE ANALYST. J d 3.88 3.81 3.73 3-71 3.64 3-54 3.64 3.82 3.89 4.03 4-04 4.08 3.82 OCTOBER, 1903. m % $ 5 -- 8.96 8.97 8.94 8.94 8.95 8.89 8-80 8-75 8.87 8-97 8-94 8.97 8.91 -- PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. 00; 5 .% g * g; 1.0323 1.0324 1.0323 1.0324 1.0326 1.0325 1.0320 1-0316 1.0320 1.0322 1.0323 1.0323 is0323 THE COMPOSITION OF MILK, BY H. DROOP RICHMOND, F.I.C. (Read at the Meeting, May 6, 1903.) THE average composition of 12,914 samples of milk received from the farms snpply- ing the Aylesbury Dairy Company’s depot in London is shown in Table I. TABLE I.-AVEHAGE COMPOSITION OF MIrx DURING 1902. & . 2: E-cg 12.66 12.61 12.46 12.47 12-32 12.20 12-28 12.35 12.54 12-82 12.90 12-54 -- 12.81 -- MOBNING MILK. EVENING MILK. AVERAGE. I I 4-06 3-97 3-93 3.90 3-91 3.79 3-82 4.05 4.10 4.23 4.21 4.24 4.02 Month.January . . . February March ... April . .. May ... June ... July ... August ... September October ... November December Average ~- ---- 8-96 1.0322 12.84 8-98 1.0323 12.78 8.95 1.0322 12.67 8.93 1.0323 12.65 8-96 1.0324 12.59 8.87 1.0322 12.43 8-78 1.0318 12.44 8.73 1.0314 12-57 8.87 1-0318 12-76 8-96 1.0321 13-00 8.93 1.0320 12-98 8-95 1.0321 13.05 8.90 1.0321) 12-73 - - ~ - - 3-70 3-64 3.53 3.53 3.37 3.29 3.45 3.58 3.67 3.84 3.87 3.91 8.96 8.97 8.93 8.94 8.9 5 8.91 8.83 8.77 8.87 8.97 8-95 8-99 1.0321 1.0322 1.0321 1.0321 1.0322 1.031‘3 1,0315 1.0311 1.0316 1.0319 1.0318 1.0318 13-02 12.95 12.88 12.83 12.87 12.66 12.60 12.78 12.97 13.19 13.14 13.19 12.92 The average percentage of fat (3.82) is higher than that found in 1901, and that, again, was higher than found in 1900, especially during the last four months.As the Sale of Milk Regulations of the Board of Agriculture came into force on September 1, 1902, which is practically the date on which the rise in the quality of the milk commenced, I feel that the view that I ventured to put forward last year-that the promulgation of the official regulations has drawn the farmer’s attention to the necessity of paying attention to the quality of milk produced, as well as the quantity-has290 THE ANALYST. received support by the results for the year 1902. It appears that the evidence cannot be neglected or brushed aside with some vague reference to the weather or the seasons ; when a gradual, nearly regular fall in fat parcentage is checked and converted into a rise at the very time when it is brought home to the milk-producer that the selling of milk below ( ( standard ” may render him liable to prosecution, there is a strong prim& facie case that there is a connection between the two facts, and I prefer to attribute the rise to the foresight, the skill, and the law-abiding sense of the British farmer rather than to coincidences or the vagaries of the British climate.I have had the opportunity of examining 197 samples from consecutive milkings of one cow. The average composition of this milk was : Morning milk . . , ... 12.59 3.71 8-88 Evening milk . . . ... 13-09 4-26 8-83 Total Solids. Fat. Solids-not-Fat. The solids-not-fat varied but little, but, as one might expect, the fat showed The table below shows the frequency with which fat of Percentage of Fat.considerable variation. differing percentages occurred : No. of Samples. 1.0 1 1.1 1 1-6 1 2-4 1 2 *5-3 *O 7 3.0-3.5 36 3-5-4.0 56 4.0-4.5 47 4-5-5.0 32 5-0-5.5 11 5.6 1 6.0 1 6.6 1 7.8 1 I have every reason to believe that all these samples are genuine, and there is even internal evidence that this is so. Taking the five lowest percentages of fat, it is found that they are followed at the next milking by percentages well above the average, thus : 1.05 per cent. was followed by 5.65 per cent. 1-15 ,, 9 ) $ 9 6.60 $ 9 1.60 ,, ,, 9 , 5.10 8 , 9-40 ,, ,? 9 9 4.70 9 , 2.65 ,, 8 9 9 , 4-65 9 ) This is what would be expected if a low percentage of fat were due to a reten- tion of cream, as has been established in other cases (cf.Dyer, ANALYST, xviii., 2). I have long held the view that milk should contain at least 0.5 per cent. nitrogen, and have considered that this is a, valuable datum for distinguishing between genuine and adulterated milks giving less than 8.5 per cent. of solids-not- fat. Cases have been recorded in which milk from Dutch cows has yielded less than 0.5 per cent. nitrogen (cj. Smecham and Ashworth, ANALYST, xxii., 172). I have lately examined some samples of milk from shorthorn cows in which low nitrogen results have been obtained.THE ANALYST. Specific gravity Water ... Fat ... Proteids Ash ... Sugar ... Nitrogen Solids- not-fat A sample of milk was examined, giving the following results : ... Specific gravity ...... 1.0326 Sugar ... ... ... ... 5.00 Water ... ... ... ... 87-26 Fat ... ... ... ... 3.97 Proteids ... ... ... ... 3.17 Ash ... ... ... ... 0.73 1.0308 85-68 5-55 4.42 3.48 0.75 99.88 0.54r 8-77 100.13 Solids-not-fat ... ... ... 8.77 As this was the mixed milk of three cows, and as the nitrogen was practically the figure which has been taken as the minimum, I examined the milk of eeoh cow, and also of one other of the same herd. Eighteen samples were obtained, each of a separate milking. Nitrogen ... ... ... ... 0,498 The results are given in Table 11. TABLE 11. 1.0322 87.90 3.35 4.70 3-30 0.71 99.96 0.518 8.75 Specific gravity Water ... Fat .. Sugar . , . Proteids Ash ... Nitrogen Solids- not-fat 1.0319 10315 8'7.63 87.83 3.81 3.77 4.78 4.88 3.29 2.92 0.70 0-70 100.21 100.10 0.516 0.456 8.56 8.50 1.0324 86-41 4-75 4-80 3.32 0.72 1,0326 86.46 4-56 5.20 2.90 0-73 99-85 0.455 898 100~00 0.520 8.84 1-0320 87.74 3.84 4.89 2-92 0.68 100.07 0.45E 8.62 1.0319 87.33 4.05 4-70 3.35 0.71 100.14 0.526 8-62 Cow No.I. Cow No. 11. 1.0327 87.90 3-28 4.56 3.42 0.75 99.91 0.537 8.82 1 -0307 87.91 3-81 4.53 3.19 0 -69 100.13 0.500 8.28 1.0306 85-89 5-48 4.68 3.26 0.71 100.02 0,511 8.63 1.0323 86.75 4-42 4.92 3.18 0.71 99.98 0.498 8.83 1.0323 86-82 4.50 4.87 3.07 0.74 100~00 0-478 8.68 1.0320 87.79 3.65 4 -83 296 0.73 99.96 -- 0.465 8.56 I cow No. 1x1. c o w No. IV. 1.0335 87.61 3.27 4-89 3.19 0.73 99.69 0.501 9-12 1.0323 87.98 3.46 4.82 3.13 0.71 100~10 0.495 8.56 1.0321 86.81 4.37 5.01 3.09 0.73 100.01 0.484 8-82 1.0316 86.78 4.37 4.70 3 -39 0.70 99.94 0.532 8.85292 THE ANALYST. Several of the nitrogen determinations, especially the low figures, were done in duplicate, and the differences were always less than 0-01 per cent. nitrogen.It is seen that out of four cows three yielded samples of milk containing very appreciably less than 0.5 per cent. nitrogen. Only one sample fell below the limit of 8.5 per cent. solids-not-fat, and watering is quite excluded. All these samples were treated with rennet, and the amount of curd by Lindet's method and its character was observed. The amount of curd followed the nitrogen fairly olosely, and the samples low in nitrogen all gave a softer curd than usual. Though I have made careful inquiries into the feeding and treatment of these cattle, I have been unable to find anything to which I could attribute the low percentage of nitrogen. It sometimes happens that samples of milk have a pink tinge, and this is usually due to the presence of blood, either from a diseased condition of the udder, or, far more frequently, from a kick or other mechanical injury. As blood has a higher specific gravity than milk, centrifugal separation should remove the blood. At low temperatures, however, most, if not all, of the blood is carried up with the cream, and its identification is difficult. By slight warming to about 50" C., and then centrifuging, the blood separates easily, and may be identified by the usual methods. The microscopical appearance of the corpuscles is not, however, the same as of those of fresh blood, as they undergo considerable disintegration. I t is, however, quite characteristic, as is shown in the following photo-micrograph (magnification, 625 diameters).

ISSN:0003-2654    

DOI:10.1039/AN9032800289

出版商:RSC    

年代:1903

数据来源: RSC

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THE ANALYST. 293 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. Detection of Fuse1 Oil in Rectified Spirits. A. IComrtroweky. (Chem. Zed., 1903, xxvii., 807.)-This is a, modification of Saglier’e process, and is claimed to avoid the errors of that test due to inevitable irregularities in heating the samples. If the spirit contains only isoamyl alcohol, 10 C.C. of it are mixed with 1 C.C. of a 1 in 1,000 solution of furfurol in ethyl alcohol, 15 C.C. of strong sulphuric acid are added, and the whole is well shaken up without being artificially heated. After standing till cold, the liquid will be found to have a more or less pronounced rose colour in proportion to the amount of amyl alcohol present, the limit of the test being 0.001 per cent. Spirit free from fuse1 oil assumes a gray coloration with furfurol.If, however, the sample contains acetaldehyde, it must be diluted to an alcohol strength of 50 per cent. by volume (specific gravity 0.934) before applying the fest. Other reagents may be employed-benzaldehyde, ortho- and para-hydroxybenz- aldehyde, for example. When 10 C.C. of the sample are treated as above with 25 to 30 drops of a 1 per cent. alcoholic solution of salicylic aldehyde and 20 C.C. of strong sulphuric acid, a liquid is obtained which is reddish by reflected light, and yellow by transmitted light, provided the amount of isoamyl alcohol does not exceed 0.01 per cent. Para-hydroxy- benzaldehyde in 2 per cent. solution yields a raspberry-red tint, which eventually becomes violet, a pure spirit remaining yellowish.Benzaldehyde gives a brick-red tint. The author is unable to get good results with Beckmann’s process (ANALYST, 1902, xxvii., 88). Above that figure the colour is garnet-red, however viewed. F. H. L. Existence of Salicylic Acid in Wines, Grapes, and Other Fruits. H. Mast- baum. (Chem. Zeit,, 1903, xxvii., 829.)-This article consists partly of a review of the discussion which has been taking place between the Portuguese and the Brazilian chemists upon the question of the pre-existence of salicylic acid, or a compound thereof, in Portuguese wines, partly of a collection of the results obtained by other investigators with different materials, and partly of a statement of the work done by Mastbaum himself since the date of his former paper (ANALYST, 1901, xxvi., 274).The author is still convinced that the substance resembling salicylic acid found in wines is actually sahylic acid, but he has not again succeeded in isolating sufficient of it to determine its melting-point. It exists principally in the stalks, as before stated; but although he has treated some 60 kilos of grape-stalks from Azeitao, and has at last, after repeated purifications, obtained crystalline aggregates, the yield was not pure salicylic acid, so that elementary analysis and determination of molecular weight were out oE the question. Salicylic acid has also been found in strawberries, but here, also, it is mostly294 THE ANALYST. present in the fruit-stalks and calices-25 grammes of the latter will give a crystalline yield; before flowering, noteworthy quantities of gallic acid, but no salicylic acid, have been met with in the plant-stems, the leaves, and the roots.The fruit-staiks of sweet and sour cherries, pears, apples, and bananas, contain no salicylic acid. F. H. L. The Estimation of Starch by Dennstedt 's and Voigtl'kder's Colorimetric Method. H. Witte. (Zeit. fur Untersuch. der Nahr. und Genussmittel, 1903, vi., 625-630.)-The author has obtained satisfactory results by employing this method (ANALYST, 1895, xx., 210), but considers that, as the quantities of material used are necessarily so small, considerable errors may be made in judging the colours produced. PI. P. s. Presence of Heavy Metals in Stored Edible Oils. E. Bertarelli (-4rch. Hyg., 1903, xlvii., 115 ; through Cbm.Zeit. Rep., 1903, 191.)-The author has tested for the presence of heavy metah in olive, rape, sesam6, and fish oils, after the liquids had been kept for considerable periods, and sometimes boiled, in jars having a lead glaze, in '' tins," and in well-cleaned copper vessels. I n certain circumstances, such as very long keeping, presence of much free fatty acid, or boiling, the oils, especially olive and sesam6, take up traces of copper and lead ; but only in the case of terne- plate containing 16 per cent. of lead does the impurity reach a hygienically significant figure. After storage in metal coated with pure tin no foreip matter could be discovered in the oils. F. H. L. The Influence of Certain Coal-Tar Dyes on the Digestion. A. J. Wino- gradow. (Zeit.fiir Untersuch. der Nahr. und Genussmittel, 1903, vi., 589492.)- Safranine, Ponceau R.R., Azofuchsine G., Orange II., Cceruleine S., Phloxine R.B.N., Iodeosine, Chrysaniline, Magdala red, Azoflavine, Benzopurpurine, and Cerise hindered the digestion of albumin by pepsin even when only a few milligrammes of the colours were present, an amount corresponding to from one-tenth to one- hundredth of the digestive solution. The colours -Quinoline yellow, Methylene green, Acid green, Iodine green, Acid azo-yellow, Yellow T., Naphthol yellow, Aniline green, Primuline, Auramine O., Aniline orange, Martius yellow, and Metanil yellow-interfered less than the first-mentioned dyes, but in every case some eBect was noticed. The action was almost inhibitive. w. P. s. Assay and Identification of Powdered Ipecacuanha.A. G. C . Paterson. (Pharm. Jour., 1903, xvii., 73-75 and 101, 102.)-The following table shows the percentage composition of the mixed alkaloid from the two varieties of ipecacuanha : Emetine ... ... ... 72-14 ... 40.5 Cephaeline ... ... 25.87 ... 56 8 Psychotrine ... ... 1.99 ... 2.7 100~00 100.0 Brazilian. Columbian. -~THE ANALYST. 295 The authors propose to distinguieh between ahe two roots by determining the proportion of the alkaloids to one another in the total quantity of alkaloid extradied. Twelve grltmmes of the powdered root are agitated for one hour in a stoppered bottle with 10 C.C. of ammonia and 120 grammes (or c.c.) of a mixture of chloroform 1 part, amyl alcohol 1 part, and ether 3 parts. About 10 C.C.of water are then added, and 100 grammes (or c.c.) of the ethereal layer are separated and evaporated to one-half. The alkaloids are extracted with 15 C.C. of & hydrochloric acid and successive small quantities of water. Excess of normal potassium hydroxide solution (about 2 c.c.) is then added, and the mixture is washed with four successive quantities of ether. The mixed ethereal solutions are washed three times with potassium hydroxide solution, and the mixed alkaline washings are extracted once with ether. All the ethereal solutions are then combined, evaporated, and the residue weighed as emetine or titrated, using methyl orange as indicator (1 C.C. of & acid = 0.0248 gramme emetine). The aqueous solutions are acidified with hydrochloric acid, rendered alkaline with ammonia, and extracted several times with a mixture of ether and chloroform (1 : 6).The extracts are evaporated, and the residue weighed or titrated (1 C.C. Tc acid = 0-0234 gramme cephaeline). The details of a large amount of experimental work, both with the pure and mixed alkaloids, are given, showing the Both aqueous and ethereal layers are reserved. reliability of the method. w. P. s. New Colour Reactions of Abrastol. E. Barral. (Journ. Pharm. Chim., 1903, xviii., 206, 207.)-The following reactions of abrastol (asaprol) have already been recorded : (1) Blue coloration with ferric chloride ; (2) red colour with mercuric nitrate ; (3) scarlet colour with uranium acetate ; (4) brown precipitate with chromic acid ; (5) yellow coloration with nitric acid ; (6) mineral acids regenerate @-naphthol, which is precipitated and gives a blue colour when dissolved in sodium hydroxide solution. I n addition to these reactions, the author states that abrastol gives a yellow to dark-brown colour with Frohde’s reagent in the cold, and a yellowish-green colour with a hot solution of sodium persulphate, changing to greenish-brown, and finally to brownish-orange.With formaldehyde and sulphuric acid it yields a bright green fluorescence, which disappears on the addition of a large quantity of water. C. A. M. New Colour Reactions of Cryogenine. E. Barral. (Bull. Phamz. de Lyon, May, 1903; through Ann. de Chim. anal., 1903, viii., 301.)-On treatment with sulphuric acid containing formaldehyde cryogenine gives a reddish-violet colour with a more or less pronounced green fluorescence.Cryogenine is soluble in concen- trated nitric acid, and on the addition of water the solution changss to deep red, and yields a brown precipitate. With sodium peroxide it gives a yellow coloration, changing to red on the addition of hydrochloric acid; whilst with sodium per- sulphate it gives a reddish-orange colour, changing to blood-red. A solution of ammonium vanadate in sulphuric acid gives an orange-yellow coloration, which296 THE ANALYST. gradually ihanges to carmine red. Bromine water and sodium hypobromite give an orange precipitate. With Frohde’s reagent (sodium sulphomolybdate) cryogenine gives a rose coloration changing to red, and, on warming to olive-green, and, finally, to emerald green.C. A. M. A Characteristic Reaction of Cryogenine. Manseau. (BUZZ. SOC. Pharpn., Bordeaux, 1903; through Ann. de Chim. anal., 1903, viii., 300, 301.)-On warming a pinch of cryogenine (benzamido-semicarbazide) with 1 or 2 C.C. of hydrogen peroxide a golden coloration is obtained, which changes to reddish-yellow or to red, according to the amount of cryogenine present (cf. preceding abstract). C. A. M. Reactions of Hermophenyl (Sodium Mercuro-disulphophenate). E. Barrd 1. (Journ. Pharm. Chim., 1903, xviii., 207, 208.)-Hermophenyl is a white amorphous powder, soluble in water (22 in loo), but insoluble in alcohol. Its solutions do not give directly the reactions of mercury, but it is decomposed by boiling hydrochloric acid and by hot ammonium sulphide, which gives a black precipitate. The only recorded colour reaction is the violet coloration given by ferric chloride. The following reactions have also been observed by the author: (1) Concentrated sulphuric acid gives a yellow or orange coloration on heating. (2) Frohde’s reagent, warmed with a little hermophenyl, assumes a yellow colour, which changes to orange, brown, and, finally, amethyst red. (3) Sodium persulphate in the cold gives a rose coloration, which changes to yellow on heating the liquid. On adding sodium hydroxide to the cold liquid a yellow precipitate of mercuric oxide is produced. (4) A solution of ammoniuni vanadate in sulphuric acid (Mandelin’s reagent) dissolves traces of hermophenyl in deep indigo streaks, eventually yielding a deep greenish-blue solution. On heating the liquid the intensity of the colour diminishes, and the liquid becomes first bluish-green and then emerald green as the temperature approaches the boiling-point. (5) Sulphuric acid, heated with herrnophenyl con- taining formaldehyde, gives an iutense reddish-brown coloration. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9032800293

出版商:RSC    

年代:1903

数据来源: RSC

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296 THE ANALYST. ORGANIC ANALYSIS. The Gas-Volumetric Determination of Formic Acid and Formates. M. Wegner. (Zeit. anal. Chem., 1903, xlii., 427-431.)-This is based on the fact that formic acid is quantitatively decomposed by strong sulphuric acid into water and carbon monoxide. The apparatus employed consists of two flasks with a communicating tube, one Aask being connected with a carbon dioxide apparatus and the other with a, nitrometer. The first flask has a dropping funnel passing through its cork, and both are provided with thermometers reaching nearly to the bottom. For the analysis of, e.g., pure sodium formate, 10 grammes of the salt are dissolved in 200 C.C. of water, and 2 C.C. of the solution introduced into the first flask. The tube of the dropping funnel (within the flask) is then filled with water,, and the flask closed.Into the second flask are introduced about 40 C.C. of strongTHE ANALYST. 297 sulphuric acid, whilst the nitrometer is filled with a solution of potassium hydroxide. The air is now expelled from the apparatus by means of a current of carbon dioxide, the acid in the second flask being meanwhile heated to 180" C. The gas burette is then adjusted and closed, and 25 to 30 C.C. of strong sulphuric acid introduced into fhe first flask by means of the dropping funnel, and mixed with the salt by shaking fbe flask. As soon as the carbon monoxide ceases to be evolved, the contents of the flask are heated to 180" C., and, finally, a current of carbon dioxide is passed through the apparatus until the volume of gas in the nitrometer becomes constant.The moisture condensing in the tube between the flasks contains some formic acid that has escaped the action of the sulphuric acid, and must be driven on by heating the ixbe. Neglect of this precaution leads to an error of about 3 per cent. in the results. After the gas has attained the same temperrtture as the room, its volume is corrected to the standard temperature and pressure, and the amount of formic acid calculated from the result. The method is applicable in the presence of acetic acid and volatile inorganic acids. Oxalic acid must be removed by previous precipitation, whilst formic acid can be separated by distillation from tartaric, citric, and malic acids. Since most formates contain sodium nitrite, it is necessary to prevent the influence of the latter.The author found it best to make use of the property possessed by ammonium nitrite of decomposing into nitrogen and water on boiling its aqueous solution. For teat experiments, 10 grammes of sodium formate and 2 grammes of sodium nitrite were dissolved in about 100 C.C. of water, and the solution boiled for an hour with 3 grammes of solid ammonium chloride under a reflux condenser (to prevent loss of ammonium formate). The liquid was then cooled, diluted to 100 c.c., and the formate determined as described above. The results without the addition of nitrite showed the salt to contain 95.33 to 95.84 per cent. of sodium formate, whilst after the addition of sodium nitrite the percentage of sodium formate in the formate used was found to be (1) 95.55 per cent.and (2) 95.47 per cent. C. A. M. Colour-Reactions of Chloroform, Bromoform, and Iodoform. R. Dupouy. (Bull. de la SOC. de Phnrm. de Bordeaux, May, 1903, 140; through Chem. News, 1903, 37, 38.)-On adding sulphuric acid to the compound formed by chloroform and thymol in the presence of potassium hydroxide, a violet coloration is obtained, having a characteristic absorption spectrum. The most convenient method of carrying out the test is as follows: 0.5 C.C. of a 5 per cent;. alcoholic solution of thymol, 1 drop of chloroform, ant! a small piece of potassium hydroxide, are mixed and heated to boiling for about thirty seconds. To the yellow or red coloured solution thus obtained 0.5 C.C. of sulphuric acid is added, and the mixture again boiled.A magnificent violet colour is produced, which must be considerably diluted with acetic acid to allow a spectroscopic examination to be made. The spectrum is characterized by two bands in the green, but nearer to the red than those given by oxyhlemo- globin. If water instead of acetic acid be used as a diluent, a blue liquid is obtained, the spectrum of which shows a band situated between bhe D line and the red. Very small quantities of chloroform may be detected by drawing its vapour298 THE ANALYST. in a stream of hydrogen through an alcoholic solution of thymol, and proceeding with the test as above. Sulphuric acid, in the absence of chloroform, occasionally gives a faint bluish coloration with thymol and potassium hydroxide, but the solution gives no absorption spectrum. The reaction above described is easily obtained with bromoform, but less readily with iodoform.w. P. s. Colouring-Matter in Yellowish-Gray Sugar. Y. Nikaido. (Journ. Amer Chem. SOC., xxv., 857.) -The author investigated the cause of the yellowish-gray tint acquired by a sample of crystallized sugar, and concluded that it wag due to the presence of iron, although the massecuite contained only 0.02 per cent. of ferric oxide, the source of which was probably the lime used for defecation. A. G. L. An Indicator for Use with Fdhling's Solution in Volumetric Determina- tions. E. F. Harrison. (Pharm. Jour., 1903, xvii., 170, 171.)-The indicator is prepared by boiling 0.05 gramme of starch with a few C.C. of water, adding 10 grammes of potassium iodide, and diluting to 100 C.C.A little of this solution acidified with acetic acid gives a blue coloration with a drop of the titration liquid as long a8 unreduced copper is present. The indicator should be freshly prepared, and will detect 1 in 20,000 of copper. w. P. s. Estimation of Starch in Substances containing Pentosans. S. Weiser and A. Zaitschek. (Landzo. Versuc7isst., 1903, lviii., 219 ; through Chern. Z e i t . Rep., 1903, 203.)--The authors describe a process, and give the necessary tables, for estimating starch in foodstuffs by a method in which ti sugar solution is first prepared from the sample and its reducing power determined. A correction is then made for the pentoses present, their copper equivalent being calculated on the basis of the mean figures for arabinose and xylose. F.H. L. Adulteration of Linseed Cakes with Oils others than Linseed. B. Sjollema. (Zeit. fiir Uqztersuch. der Nahr. und Geiaussnaittel, 1903, vi., 631-637.)-Linseed cakes poor in oil are soinetimes enriched by the addition of foreign oils. For the detection of this adulteration the author recommends determinations of the refractometer number and iodine number of the oil obtained from the cake. The refractometer numbers of sixteen samples of pure linseed oil obtained from seeds from various countries are given. At a temperature of 15' C. the numbers varied between 87.0 and 91.5. In case an abnormal refractometer number is found, the free acid in the ssmple should be determined, each 10 per cent. of the latter depressing the reading by about 1.5 scale The iodine values (Hiibl) lay between 165 and 185.degrees . w. P. s. The Stannous Chloride Test for Sesame Oil. P. Soltsien. (Pharm. Zed., 1903, xlviii., 524; through Chem. Zeit. Rep., 1903, 191.)-It is known that theTHE ANALYST. 299 delicacy of this test falls off if the liquids remain too long after agitation without separating. Emulsification can be prevented by dissolving the oil in about twice its volume of petroleum spirit, adding half a volume of stannous chloride solution, shaking well, and standing the tube in water at about 40" C. F. H. 1;. The Solidifying Point of Oils. D. Holde. (Mitteil. kgl. techn. Versuchsamt., Berlin, 1903, xxi., 57 ; through Chem. Zeit. Rep., l902,176.)-Some years ago it was shown that if a sample of petroleum which gave a solid deposit but did hot solidify completely at - 10' C.was kept at that temperature for an hour, and was then further cooled to - 1 2 O C., a larger amount of solid matter separated out, but the sample as a whole remained fluid. If, however, the same specimen was cooled directly to a temperature of - 1 2 O C., it became solid all through. Evidently, in the former case the solidified paraffin was given opportunity to settle, so that during the second cool- ing insufficient solid matter was produced to destroy the fluidity of the upper portion of the oil; whereas, when cooled to the lower temperature at once, the precipitation of solid matter took place uniformly, and caused apparent complete solidification. Recently a similar phenomenon has been observed in a mixture of bone oil and rape oil. F.H. L. Estimation of Free Acid in Dyed Mineral Oils. J. Marcusson. (zitteil. kgl. tech. Versuchsanst., Berlin, 1903, xxi., 48 ; through Chem. Zeit. Rep., 1903, 176.) -Pale mineral oils, especially such as are used in refrigerating machines, are occa- sionally stained red with some kind of dye. If the dyestuff is soluble in dilute hydro- chloric acid the solution of the oil in petroleum ether may be extracted with that liquid, then washed with water, and finally titrated with alkali as usual. But if the dye is not soluble in acid, it may be reduced to a colourless derivative by treating the oil with tin and hydrochloric acid, at an elevated temperature if necessary, then dissolving the oil in petroleum spirit and titrating as before.Another method is to agitate the solution in petroleum spirit with a known excess of decinormal sodium hydroxide in 50 per cent. aloohol, then, without separating the liquids, titrating the aqueous iayer back with hydrochloric acid in presence of phenolphthalein. Fifty or 100 C.C. of the oil should be taken for either of these latter tests. F. EL L. Estimation of Tarry Matter in Dark Cylinder Oils. D. Holde. (&fitted. kgl. techn. Versuchsanst., Berlin, 1903, xxi., 57 ; through Chent. Zeit. Rep., 1903, 176.) -Referring to the method which the author has already (this vol., p. 154) described for this purpose, it should be noted that if the samples contain paraffins, a consider- able proportion of them may be thrown out of the ethereal liquid at laboratory temperatures when the alcohol is added.These paraffins may be separated from the recovered black tarry matter by extracting it; with boiling 100 or 96.5 per cent. alcohol as long as the cooled extracts still deposit white flakes. The amount of paraffin varies betweer 0.2 and 1-0 per cent. F. H. L.300 THE ANALYST. Some Chemioal Constants of Fossil Resins. R. A. Worstall. (Journ. h z e r . Chem. SOC., xxv., 860.)-The author proposes the following scheme of analysis for fossil resins, the results obtained being only comparative, however, when the samples examined are of the same general nature, as ‘‘ chips,” ‘‘ dust,” etc. Moisture.-One gramme of the finely-powdered resin is dried for one hour a t 110” c. Insoluble Matter, Ash, Insoluble Organic Matter.-Two grammes are treated with 25 C.C.benzene and 10 C.C. acetone in a small beaker. For some of the harder resins, epichlorhydrin, aniline, or other solvent may have to be added as well. When solution is ‘complete, the liquid is decanted off, as it would clog a, filter, and the residue is washed with more of the same solvents on to a tared filter-paper. I t is dried, weighed, and incinerated, the difference between the ash and total insoluble giving the insoluble organic matter. Indirect Acid Number.-One gramme is allowed to stand for eighteen hours in a tightly-stoppered bottle with 15 C.C. benzene, 5 C.C. alcohol, and 15 C.C. alcoholic caustic potash; 25 C.C. alcohol and a little phenolphthalein are then added, and the whole titrated back with 2 sulphuric acid.The number of milligrammes of KOH used represents the acid number. Iodine Absorption.-0.2 gramme of the sample and 10 C.C. chloroform are treated with 40 or 50 C.C. of Hub1 solution, and the determination is finished as usual. CoZour.-Ten grammes of the resin are dissolved in 50 C.C. acetone and 50 C.C- benzene, and the colour is noted after settling in a 4-ounce oil-bottle. Appended are results obtained by the above methods : Resin. Kauri ... ... ... Manilla ... ... Pontianac . . . ... Zanzibar ... ... Mozambique . . . ... Madagascar . . . . . . West African . . . ... Sierra Leone ... ... Brazilian . . . . . . Damar ... ... ... Samples Examined. 43 19 2 2 1 1 8 2 3 11 ACID NUMBER. Max. R l i n . 142 72 199 146 143 135 104 79 80 95 152 108 118 114 149 131 51 24 IODINE VALUE.M e n . 170 74 148 104 142 119 123 115 136 126 143 122 105 102 134 123 124 103 In addition, results are given showing the effect of powdering the resins and exposing them for four months to the air. In all cases oxidation took place, witb consequent decrease in the iodine and increase in the ‘acid number, the decrease and increase being roughly equal, so that the sum of acid and iodine number for any one variety is roughly constant, The more finely divided the sample the more rapidly will oxidation take place, and the author recommends that no dust should be rejected as adulterated merely because it shows a high acid value. A. G. L. Examination of Bleached Textile Fabrics. G. Ambuhl. (Chem. Zeit., 1903, xxvii., 792.)-In the manufacture of certain classes of decorated (embroidered)THE ANALYST.301 cotton goods, where the ornamentation is carried out on unbleached fabric, and the whole is afterwards bleached by treatment with caustic and carbonated alkali, chloride of lime, and acid, the practical question arises whether the articles have been efliciently bleached, or whether they are likely to turn yellow again on storage. If satisfactory and representative samples can be obtained, the question may be answered by determining (a) the amount of natural wax, resin, and fat, ( b ) that of the lime soaps, and (c) that of the ash in the finished wares. For the first purpose the samples (15 to 18 grammes), either in the air-dried state or after the moisture has been driven off (and estimated) at 100” C., are extracted with an ether specially redistilled in an apparatus consisting wholly of glass, and put together with mercury seals.The quantity of extract as weighed after drying at 100” or 102” C. may reach 1 or 1.5 per cent. in the unbleached articles, and may be as little as 0.01 or 0.008 per cent. in the best thin bleached goods: 0-025 per cent. may be considered the maximum limit for first-class articles, and 0.04 per cent. as a sign of insufficient treatment. After this extraction the lime soaps can be determined by soaking the samplee for half an hour in 5 per cent. hydrochloric acid, thoroughly washing and drying them, and extracting as before, the yield being either weighed or titrated as stearic acid. 0.03 to 0.04 per cent. of fatty acid may be taken as the limit for the best goods ; 0.08 is a sign of defective washing (with hard water) ; 0-12 per cent.or more is bad. The ash of the best bleached goods should not exceed 0.03 or 0.05 per cent. ; it should be white, and consist of calcium carbonate and silicates. A blue ash indicates an addition of smalt ” to mask the yellow of imperfectly bleached goods ; a red ash points to rusty needles, etc., in the sewing-machines. I n certain cases it may be desirable to look for chlorine and (mineral) acid in the finished cotton materials. F. H. L. A Modified Dumas Method of Nitrogen Estimation. R. Bader and A. Stohmann. (Chem. Zeit. , 1903, xxvii., 663.)-In carbon and hydrogen deter- minations in the substituted naphthylamine sulphonic acids, which are difficult to burn, Liebig’s method fails in yielding satisfactory results, but these can be obtained by Kopfer’s modification of the Lippmann and Fleisher method, in which asbestes, coated with copper oxide, is employed.Since in determining the nitrogen of the above-mentioned bodies Dumas’ method also fails, the authors have devised the following method for this purpoae, which is founded in principle on that of Lipp- mann and Fleisher. The combustion-tube employed is of moderate diameter and 55 centimetres long. At b it is charged loosely with 20 centimetres of copper oxide asbestos, a plug of plain asbestos being placed at either end. At c is a 10-centimetre spiral of copper gauze. Round the parts b and c is wrapped a jacket of brass gauze, and a similar sleeve, 10 centimetres long, is made to slide over the former part of the tube. The apparatus is prepared by removing the copper spiral and igniting the asbestos, etc., in a current of oxygen, applying the heat in the direction of the arrow, and moving the sleeve e suitably. When cold, the copper is put into place, and a current of carbon dioxide passed till all oxygen is driven out; b and c are then302 THE ANALYST. heated by means of the burners 2 and 3 ; the boat containing the substance in very fine powder, mixed and covered with copper oxide, is brought into position (about 1 centimetre from the nearest asbestos plug) ; and by proper manipulation of the burner 1 and the movable sleeve the substance is burnt, without allowing it to volatilize backwards. The copper oxide asbestos only needs to be ignited in oxygen after every combustion or every second combustion to be ready again. The tube will serve for two or three dozen analyses before becoming crystalline. The whole process only takes about one hour. The consumption of gas is small. The apparatus is cheap. The copper oxide asbestos is prepared by treating soft woolly asbestos with hydrochloric acid and water, then agitating it with one-quarter or one-half its weight of freshly precipitated and damp metallic copper, removing the liquid with the pump, and finally igniting in air. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9032800296

出版商:RSC    

年代:1903

数据来源: RSC

摘要:

302 THE ANALYST. l.NORGANIC ANALYSIS. Separation of Gold from Platinum. R. Willstatter. (Be?-., 1903, xxxvi., 1830; through Chmz. Zeit. Rep., 1903, 176.)-Gold chloride can be easily and quantitatively withdrawn from its aqueous solution, even in presence of much hydrochloric acid, by extraction with ether. Since platinic chloride is insoluble in that liquid, the process is available for separating the two metals. A similar treat- ment is also useful in the preparation of pure hydrochlorides of certain basic substances from the corresponding double compounds with auric chloride. F. H. L. Volumetric Estimation of Copper. B. Oddo. (Rend. Soc. chim. di Roma, 1903, i., 54; through Chem. Zeit. Rep., 1903, 202.)--This process depends on the fact that symmetrical diphenylcarbazide reacts with copper salts to form copper diphenylcarbazone, which gives so powerful a violet colour to khe solution that it is visible in dilutions of 1 : 100,000, where the ferrocyanide reaction fails.Secondly, an alkali metal xanthate yields a brown precipitate with cupric salts, which changes to yellow immediately the metal is reduced by the reactions to the cuprous state. If, then, a copper solution is neutralized with sodium hydroxide, mixed with a, solution of diphenylcarbazide in dilute alcohol, and a solution of potassium xanthate is added, the former produces a violet colour and the latter a yellow ; but the violetTEE ANALYST. remains visible until the xanthate is in slight excess, when it disappears directly. The end-point of the reaction is seen better by adding a copper solution to the mixture of diphenylcarbazide and xanthate, and shaking the whole.The yellow cuprous xanthate first falls, but as soon as the copper is in excess a brick-red colour is produced, which consists of a mixture of the yellow with the violet carbazone. Potassium xanthate is very alterable in solution, and must be prepared fresh when wanted. F. H. L. Note on the Effect of Combined Carbon in Iron on the Test for Tin. R. B. Riggs and E. 5. Merriam. (Journ. Arner. Chem. SOL, xxv., 876.)-The authors have found that the hydrochloric acid solution of iron, containing as little &S 0.2 per cent. of combined carbon, 'reduces mercuric chloride sufficiently to give 8 cloudy appearance in a few seconds. Consequently, in testing for tin by the action of staunous chloride on mercuric chloride, if iron is used to reduce the solution supposed to contain tin, care must be taken that this iron is practically free from carbon, otherwise a precipitate of mercurous chloride may be obtained in the abgence of tin.Iron which evolves no odour when dissolved in hydrochloric acid may be taken as being free from combined carbon. A. G. L. Determination of Sulphur in Iron and Steel. Volumetric Estimation of Arsenic. A. Kleine. (Chenz. Zeit., 1903, xxvii., 729.)-The author describes an apparatus for the purpose of estimating sulphur in iron, etc. It is put together without rubber corks, in which the ground-joint at the mouth of the flask is preserved from the danger of becoming fixed by being kept cool. From the annexed illustration it will be seen that the upper part of the device is a hollow vessel which serves as a condenser, and which is expanded near the top to form the ground-joint with the flask, while below tbat spot its diameter is so small as to leave an annular space for the ascent of the vapours.These vapours leave the flask at the point F, where they enter the worm inside the condensing vessel, quitting it at the left-hand side to enter the triple receiver. Two tubes are joined to the condenser for a circulation of water, but as the flame put under the flask is small, it is usually sufficient to fill the inner cylinder with cold water once for all. The stoppered tube €unnel passes right through the condenser as shown; if desired, it inay be fitted at its mouth with a leading tube, ground in, for the supply of a current of carbon dioxide or hydrogen.The receiver is specially designed to prevent any liquid from being drawn back into the flask. B is charged with such a quantity of reagent (say 50 c.c.) that when the stopper is put i n and air is blown in at C, the liquid rises 30 or 35 millimetres in D. I n carrying out the process, the receiver is charged with 50 C.C. of a liquid made by dissolving 20 grammes of cadmium sulphate in 400 C.C. of water and 600 C.C. of304 THE ANALYST. 0.96 ammonia. Ten grammes of steel or 5 of cast-iron are put into the flask, 100 c.c of water are added, and 70 C.C. of strong hydrochloric acid are run in through the funnel. The flask is gently heated till everything is dissolved.The cadmium sulphide in the receiver is collected on a paper, which, without being washed, is thrown into a 200 C.C. beaker half full of water, where it is mixed with a little starch and hydrochloric acid (300 C.C. of strong HC1 diluted with 850 C.C. of water), and titrated with iodine solution. In order to avoid loss of sulphuretted hydrogen, the beaker is brought under the burette containing the iodine solution, the tap of which is turned on till the reagent issues at a speed suiting the quantity of sulphur under estimation, and, while it is flowing in, about 75 c:c. of the above-mentioned hydrochloric acid are introduced gradually. The iodiLe solution may conveniently contain 25 grammes of potassium iodide and 7.928 grammes of iodine per litre, 1 C.C. being then equal to 1 milligramme of sulphur. Matters should be so arranged that not more than 10 C.C.of iodine are required. The arsenious sulphide obtained by the usual distillation process is collected, washed with cold water, and dissolved in ammonia. The solution is mixed with 50 C.C. of the cadmium reagent and allowed to rest till the sulphide has settled. This is filtered, well washed with cold water, and titrated, as above, with iodine solution, I n order to prevent any ferric chloride passing over into the original distillate, the flask should have a capacity of at least 750 C.C. F. H. L. The same reagents are useful in the determination of arsenic. Rapid Determination of Phosphorus in Steel. Gexge Auchy. (Journ. Amer. Chem. SOC., xxv., 772.)-One gramme of steel is dissolved in 50 C.C.nitric acid (specific gravity 1-135), the solution boiled, a little solid permanganate added, the solution again boiled, decolorized with ferrous sulphate or sugar, and cooled. After adding 10 C.C. of strong ammonia and 50 C.C. of molybdate solution, the mixture is shaken as usual according to the Handy method in an Erlenmeyer flask, trans- ferred to a 7-inch test-tube, allowed to stand for half art hour, and whirled in a centrifugal machine. The solution may then be completely poured off the precipitate without filtration. By filling the tube up with water, again whirling it, pouring off the water, dissolving in alkali, and titrating as usual, the error due to the acid adhering to the precipitate is reduced to less than 0.001 per cent.of phosphorus. A. G. L. The Determination of Sulphur in Gunpowder by means of Hydrogen Peroxide. J. Petersen. (Zeit. anal. Chem., 1903, xIii.% 406-417.) 1. Szdphur in Gunpowder.-About 0.5 gramme of the powder is boiled for twenty minutes with about 40 C.C. of a 2 per cent. solution of sodium hydroxide. The liquid is then allowed to cool slightly, mixed with 50 C.C. of hydrogen peroxide solution (about 3 per cent.), and boiled for five minutes. Hydrochloric acid is now added in excess, and the contents of the flask boiled for a momant, and then filtered, and the sulphate in the solution precipitated in the usual manner. The filtrate from the carbon should be evaporated to dryness to expel the nitric acid formed from theTHE ANALYST. 305 nitrate in the powder, the residue dissolved in water containing hydrochloric acid, and the sulphate precipitated with barium chloride.If the evaporation be omitted the results are somewhat too high (e.g., 7.93 per cent., instead of 7.81 per cent. in test experiments). C. A. M. The Determination of Sulphuric Acid in the Presence of Zinc. A. Thiel. (Zeits. Anorg. Chem., xxxvi., 84.)-The author shows that in the presence of zinc salts the precipitation of sulphuric acid by barium chloride is incomplete, although barium is conipletely precipitated by sulphuric acid from a solution containing a zinc salt. The determination of sulphuric acid can be made accurate by first exactly precipitating the zinc as hydroxide by adding a, bare excess of ammonia, then adding barium chloride to the hot solution, and dissolving the zinc hydroxide by means of a small excess of hydrochloric acid.The addition of an excess of ammonia sufficient to dissolve the zinc hydroxide before adding barium chloride gives inexact results. A Method for the Detection of Chlorides, Bromides, and Iodides. Stanley Benedict and J. F. Snell. (Journ. Amer. Chenz. SOC., xxv., 809.)-To a portion of the neutral liquid to be tested potassium iodate in one-tenth normal solution is added, and the liquid acidified with acetic acid. A coloration shows the presence of iodide, which may be confirmed by shaking with chloroform or carbon bisulphide. Should sulphocyanates be present, sodium acetate must be added before making the test. If iodide is found, a little potassium iodate is added to the main portion of the solution, which is then boiled.This procedure is repeated until a small excess of iodate has been added. The liberated iodine is completely expelled by boiling, and enough nitric acid (specific gravity 1-18) is added, to form one-third of the total volume. The solution is then boiled till colourless, 1 or 2 C.C. of potassium iodide solution (one-fifth normal) are added t o reduce the iodate, and the liquid is again boiled till colourless. An equal volume of concentrated nitric acid is then added, followed by a few drops of silver nitrate. A white precipitate indicates chloride. By means of the above method chlorine can be detected in a mixture containing 0.5 C.C. of of potassium bromide or iodide, whereas the limit of delicacy of the chromyl chloride method was reached with a mixture of 5 C.C.of A coloration shows the presence of bromide. sodium chloride and 20 C.C. sodium chloride with 10 C.C. of & potassium bromide. A. G. L. Purification and Estimation of Iodine. Abraham Gross. (Eng. h'oc. West. Penizsylva~izin, xix., 380.)-The author has made experiments comparing the purification of iodine by the Stas method, in which a strong solution of iodine in potassium iodide is precipitated by water, the iodine being then thoroughly washed, dried over calcium chloride, or nitrate, or sulphuric acid, and finally sublimed three times in a current of dry air, with other methods, in which the iodine, before being dried and sublimed, was washed repeatedly with water, or simply mixed with potassium iodide.The306 THE AEJALYST. Stas method gave the piirest iodine, sulphuric acid being found the best drying agent. I n the method in which the iodine was mixed with potassium iodide before drying, the latter could not be removed completely, even by three sublimations. No chlorine could be detected in iodine which had been dried over sulphuric acid. The purity of the iodine was determined by allowing it to act on an excess of zinc in the presence of water, filtering off the iodide solution obtained, and titrating an aliquot part with silver nitrate, chromate being used as indicator. A. G. L. Titrations with Potassium Iodate. Launcelot W. Andrews. (Joum. Amer. Chem. SOC., xsv., 756.)-The author shows that standard potassium iodate solution may be used for the determination of many substances which are either oxidizable or which liberate iodine from potassium iodide, provided the solution contains a, sufficient quantity of hydrochloric acid.Chloroform is added, and becomes colourless at the end of the titration. Thus, iodides are oxidized according to the equation : 2KI + KIO, + 6HC1= 3KCl+ 3ICl+ 3H20. Chromates may be determined by adding an excess of a standasd solution of potassium iodide and enough hydrochloric acid to form at least half the total mixture at the close of the titration ; 5 C.C. of chloroform are used. Free iodine may be dissolved in a known amount of iodide, and then titrated. Chlorates should be allowed to act on an excess of standard iodide in the presence of a large quantity of hydrochloric acid for about fifteen minutes before titrating.Arsenious chloride is oxidized according to the equation : In this case, the final solution should only contain about 20 per cent. of hydro- chloric acid. The presence of copper does not interfere with the titration, so that arsenic in Paris green may be determined by it directly. The titration of antimonious compounds is similar to that of arsenious chloride. Ferrous salts behave like iodides. The presence of oxalic acid has no influence on the reaction, but the end-point is not 80 sharp with ferrous salts as with iodides, unless a little manganous chloride is added. A. G. L. 2AsC1, + KIO, + 5H20 = 2H,AsO, + KC1 + ICI + 4HC1. O n the Use of Sodium Oxalate in Volumetric Analysis. G. P. L. Sorensen. (Zeit. anal. Chem., 1903, xlii., 333 359.)-In a previous communication (ANALYST, xxiii., 84) the author showed the advantages of using normal sodium oxalate in acidimetry.I n the present paper he describes in detail experiments made to test the reliability of the method. In igniting the sodium oxalate to convert it into carbonate and hydroxide the results are identical, whatever method of ignition be employed, provided that the whole of the carbon formed in the decomposition is consumed; and even when some carbon is left the error is negligible. As regards the temperature of ignition, it is shown that at 200" C. sodium oxalate parts but slowly with its water, but that at 230" C. it loses it rapidly, and is rendered completely anhydrous after being heated for a few hours at 240" to 250° C.The anhydrous salt is not hygroscopic. The pure normal oxalate can be obtained freeTHE ANALYST. from inorganic impvrities, and containing only traces of organic impurities not volatile at 130" C. The latter can be detected by heating 1 gramme of the oxalate with 10 C.C. of pure aulphuric acid (free from dust) at first gently, and finally to the boiling-point, pure preparation giving no brown coloration. For the preparation of absolutely pure oxdate, the author recommends the followiog method : A solution of pure sodium carbonate is mixed with somewhat less thaa the theoretical quantity of pure oxalic acid, and the liquid concentrated to a fourth of its bulk and cooled. The crystals are collected, powdered, thoroughly washed with cold water, and dried in the water-oven.They are then dissolved in as little hot water (LEI possible, and the solution again concentrated, the salt that now separates being nearly free from carbonate. Finally, it is dissolved in nearly boiling water, reprecipitated by means of alcohol, washed with absolute alcohol, and dried first in a hot-water oven, and, finally, at 230' C. C. A. M. Methods for Volumetric Analysis. G. Lunge. (Report to International Congress of Applied Chemistry ; through Zeits. f. angew. Clzem., 1903, xxiv., 560.)- As indicator the use of methyl orange is recommended for all cases except that of weak acids, for which phenolphthalein should be employed. In spite of statements made by J. Wolff, methyl orange is found to yield good results in the presence of boric acid.If it be desired to titrate carbonates, using litmus or phenolphthalein as indicator, the boiling should be carried out in vessels of porcelain, platinum, or silver ; for even Jena glass is attacked by hot soda solutions. As material for standardizing solutions, preference is given to sodium carbonate, made by heating bicarbonate in a half-filled platinum crucible rapidly to 270' C., and maintaining for half an hour at a temperature not exceeding 300' C. This carbonate is used to standardize a solution of hydrochloric acid, with which the titre of a solu- tion of caustic alkali is established. With the latter a solution of oxalic acid is titrated, which in turn serves to standardize a permanganate solution. In the discussion that followed F. W. Kuster called attention to the effect of dilution in diminishing the accuracy of titrations carried out with methyl orange.Lunge, in reply, recommended that the strength of solutions titrated should not be less than one-fifth normal. A. &I. A Colorimetric Method of determining the Oxygen Absorption of Water. C. Lenormand. (Bull. SOC. Chzm., 1903, xxix., 810-814.)-The method consists of boiling the water with a standard alkaline solution of potassium permanganate, and determining from the loss of colour the amount of oxygen absorbed I n the case of sea-water or saline waters containing chlorides or bromides, 100 C.C. of the sample are boiled over a moderate flame for ten minutes with 10 C.C. of a solution of potassium perrnanganate (0.395 gramme per litre ; 10 C.C. = 1 milligramme of oxygen) and 10 C.C.of a saturated solution of sodium bicarbonate, I t is then allowed to settle, and the supernatant liquid decanted, and its colour compared with that of a solution containing 10 C.C. of the permanganate solution and 90 C.C. of water, The results thus obtained are shown to be constant and exact. Thus in fifteen determina-308 THE ANALYST. tions on a srtmple of sea-water the smonnt of oxygen absorbed ranged from 2.10 to 2.20 milligrcbmmes per litre. In the case of potable waters the liquid remains turbid for several hours, rendering a colorimetric comparison impossible. This is obviated by adding with the reagents 1 C.C. of a saturated solution of magnesium hydrocarbonate, so that the water becomes clear in ten to fifteen minutes. C.A. M. The Preparation of Oxygen. R. B. Riggs. (Journ. Amer. Chem. Soc., xxv., 876.)-Potassium permanganate is gently warmed to about 50" C. with excess of dilute (1 to 4) stllphuric acid. 2KMn0, + H2S0, = K,SC), + 2Mn0, + H,O + 30. Thus, 10 grammes permanganate treated with 40 to 50 C.C. of dilute sulphuric acid generate more than 1 litre of oxygen, The reaction proceeds according to the equation : A. G. L. The Detection of Foreign Admixtures in Portland Cement. W. Fresenius. ( 2 e i t s . f . angezo. Ghem., 1903, xxiii., 539.)-R. and W. Fresenius have given the fol- lowing limits for genuine Portland cement : Specific gravity of unignited cement, not less than 3.00 ; afr;er ignition, not less than 3.12 ; loss on ignition, 'not more than 3.4 per cent. ; alkalinity of aqueous extract of 0.5 gramme = 7.2 C.C.& acid ; perman- ganate discoloured by 1 gramme, not more than 2-8 milligrammes; percentage of magnesia, not more than 3 per cent. Nearly all admixtures lower the specific gravity ; high loss on ignition and high alkalinity indicate the addition of hydraulic lime ; high permanganate absorption points to the addition of slag cement. These methods will not, however, always detect admixtures of blast-furnace slag, which resembles Portland cement in compo- sition, though the specific gravity and permanganate absorption will differ from the limits given above. The permanganate test gives a rough indication of the amount of sulphide present, but clearer evidence as to the presence of slag may be obtained by a more accurate estimation of the sulphide. This may be carried out by treating the cement with a standard solution of arsenious acid in hydrochloric acid, filtering from the sulphide of arsenic formed, and determining the arsenic remaining in the filtratd. As an alternative, the consumption of permanganate may be determined in one portion, and another portion may be treated with a solution of a cadmium salt to remove sul- phides, and the permanganate absorption be again ascertained. A normal Portland cement does not contain more than 0.15 per cent. of sulphur as sulphides, whereas a cement to which ground slag has been added may contain as much as 0.8 per cent. In doubtful cases the cement should be mixed with a suitable liquid and centrifuged, and an examination should be made of the different layers. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9032800302

出版商:RSC    

年代:1903

数据来源: RSC

摘要:

THE ANALYST. APPARATUS. 309 Bormann’s Improved Bunsen Burner. (Chem. Zeit., 1903, xxvii , 435.)-The accompanying sketch shows an atmospheric burner which is claimed to be specially easy to take to phees and clean, having no screws, and also to be more efficient &an others. The upper tube rotates, and carries with it the upper horizontal disc, and this move- ment regulates the supply of air through the holes in the lower disc. As the parts have plenty of play, they do not become fixed by corrosion, even when constantly used in an acid atmosphere. The burner is made by Gerhardt of Bonn. F. H. L. A New Extraction Apparatus. W. Pip. (Chem. Zeit., 1903, xxvii., 706.)-This is an apparatus for extract- ing a liquid with an immiscible solvent. The vappurs rise from the distillation, pass through the inverted U-tube, and finally enter right at the bottom of the vessel containing the liquid to be extracted, where they condense, and rise to the surface in very small drops.Further subdivision of the ascending liquefied solvent may be obtained by the use of the perforated porcelain plate shown in the sketch. After arriving at the surface of the liquid, the solvent runs back to the flask through the oblique pipe. The apparatus has the advantage that the distilling flask can be changed without trouble, while, since the condensing worm can be removed with the cork at the top of the extractor, any desired adjustment of the liquid under extraction may be made without interrupting the process. The ends of the U-tube on the vapour ascension pipe are made to enter for a distance of 2 centimetres into the latter, and thus contact between the solvent and the rubber connections is avoided.F. H. L.310 THE ANALYST. Description of a Bomb-Calorimeter and Method of its Use. W. 0. Atwater (Joum. Amer. Chem. Soc., XXY., 659.)-The bomb described is a modification of Berthelot’s. I t is made of steel lined with platinum or gold-plated copper, and consists of three parts-a cup (A), a cover (B), and a threaded collar (C) to hold the oover in place. The joint between the cup and cover is made tight by means of a lead-washer (K). The conductor ( H ) is insulated from the cover by being surrounded with a rubber tube at M, the rubber being protected inside the bomb by a mica disc held in place by a platinum nut.The lining of the cover is sweated on to the steel, while the lining of the cup is removable, being spun so as to fit the cup exactly. The authors prefer gold-plated copper to platinum for this lining. The plating must be put on in layers, each layer being burnished before the next one is applied, as otherwise blisters are produced in the plating when the bomb is used. Instead of platinum capsules to hold the substance to be burnt, nickel vessels are used, which are first superficially oxidized by being heated in a Bunsen flame. The thermometer is tapped by means of an electrical hammer before any reading is taken. As standard sub- stances to burn the authors recom- mend benzoio acid (6,322) and cane-sugar (3,959), which latter has the disadvantage, however, of not being ignited by the iron wire alone, but requires a further kindler, such as a pellet of naphthalene. and J.F. Snell. A. G. L. An Adjustable Hydrometer. Ulrich. (Chem. Zeit., 1903, xxvii., 705.)-This is a hydrometer of the conventional form, but provided, below the weighted bulb, with a depending hook from which any one of a series of glass bobs loaded with the proper quantity of mercury can be suspended. The usual scale in the cylindrical portion of the instrument is divided vertically into as many faces as there are detachable bobs, each face being marked to indicate the bob belonging to it. Thus, for example, ifTHE ANALYST. 311 bob I. is attached to the hydrometer, the uppermost figure on Scale I. may be 0.7, and the lowest figure 1.0; if bob 11. is used the corresponding figures on Scale 11.may be 1.0 and 1.5 : and if 111. is hung on to the hook, the readings on Scale 111. range from 1.5 to 2.0- the three specific gravities 0.7, 1.0, and 15, all being at the same horizontal level on the stem. By this method of construction, the hydrometer becomes much shorter than one of the ordinary type covering the same range of gravities, and it is therefore more convenient and less fragile to handle; while, as each scale bears only one-third of the readings given by the entire instrument, the divisions near the lower end of the stem are not so compressed, and they are accord- ingly legible to a greater degree of accuracy. F. H. L. A New Gas-Burner. L. Quennessen. (Chem. News, lxxxviii., 66.) - The burner shown in the figure is intended for use in assaying for dissolving the silver from the button of silver and gold.It may also be used in Kjeldahl’s method. The gas issues through holes arranged around the interior of the crown, so that the heating takes place around the sides of the matrass, not from the bottom. By means of the clip shown, the height of which can be regulated by a screw, the matraw or flask may be supported in a convenient way. The bottom of the flask rests on a support of the form of a tulip, which is brazed on to a crew turn- ing along the axis of the heating-crown, so that the bottom of the matrass can be raised or lowered at will. A. G. L.312 THE ANALYST. A Method for Calibrating Burettes. D. W. Horn and Elimbeth M. Van Wagener. (Amer. Chem. Journ., xxx., 96.)-Two burettes are mounted in an upright position on a tall iron stand, their tips being joined by a piece of rubber tubing.One of them is kept in a fixed position, whilst the other is raised or lowered. The calibration of the movable burette in terms of the stationary one is effected by filling it with water, and gradually raising it so as to transfer the water to the fixed burette. The calibration is duplicated by lowering the moveable burette, thus causing the water to flow back into it. The readings are taken at any convenient points. The relative calibration thus obtained may be made absolute by weighing the quantities of water which the stationary burette delivers between selected marks along its scale, any number of other burettes then being standardized by its help.The rubber tubing connecting the tips of the two burettes should be of such a length that about 20 centimetres of it hangs vertically below each burette, and it should hang freely, without coming in contact with anything that might help to support its weight. A. G. L. A New Separating Funnel. E. Thon. (Chem. Zeit., 1903, xxvii., 796.)-This is a funnel of the usual pear shape, but without the ordinary stopcock at the base, the projecting plug of which is not only liable to drop out when the liquids are being shaken, but is prone to catch in the ring of the stand when the funnel is suspended during use. Through the usual aperture at the top of the funnel passes a hollow tube of glass, closed at its lower extremity, prolonged downwards a short distance below the base of the pear. I t makes a ground-joint with the body of the funnel both at the neck and at the mouth of the delivery-tube. At the top it is fitted with a ground stopper, and just below it has a lateral aperture for the passage of liquid (and air) from its interior to the cavity of the apparatus itself. The ground-joint in the delivery-tube is made to act as a stopcock by forming a longitudinal depression at one spot on the exterior of the inner tube, and a corresponding bulge on the wall of the funnel-tube ; and thus, if the said inner tube is rotated into a certain position the bulga and depression coincide, and the funnel empties itself. Y. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9032800309

出版商:RSC    

年代:1903

数据来源: RSC