摘要:

APRIL, 1908. Vol. XXXIII., No. 385. THE COMPOSITION OF MILK. BY IT. DROOP RICHMOND, F.I.C. ( 1 . 2 ~ ~ 7 n t t h e nIccti?ty, MWC~L 4, 1908.) A ccmge Coi/ipsitioii, of JIiZk.-Of the 35,831 samples analysed in the Aylesbury Dairy Coinpany’s Laboratory during 1907, 31,143 were samples of milk. The average coulposition of 14,967 samples of milk received from the farms is given in Table I. (see p. 114). The difference between the percentages of f a t in the morning and evening milk -0.38 per cent.-is very near to that usually found. As has been generally observed, the f a t wag lowest in June, and highest in Novem- ber. Low solids-not-fat occurred in July and August, but the average was scarcely114 THE ANALYST. so low as in former years. The average amount of fat-3-75 per cent.-is slightly higher than has been found for the past three years, and during the later months of 1907 the milk was distinctly better than the average. TABLE I.AVERAGE COMPOSITIOS OF MILK D ~ R I N G l!K. Morning Milk. Evening Milk. A vorage. Solids- not- Fat. 3olids- not- Fir t . Jolids- not- Fat. 8 98 9.00 8.97 8.93 8'94 8 9 4 8-83 8'85 8-90 8.99 8.98 8.96 8.94 Total Solids. Spccific :rarity. Total %lids. Specific Gravity. Total Solids. Specific ;ravity. 1 -0325 1.0325 1 *0325 1 -032.5 1 *0326 1 *0326 1 -0321 1 *0321 1 *0322 1 '0324 1 *0325 1 *0322 1'0324 Fat. Blon th . Fat. Fat. 1.0324 1 -0325 1 -0323 1 *0322 1 -0323 1.03'22 1.0316 l'G316 1 *03 1s 1 '0320 1 '031 9 1 '0320 3-56 3.84 3.79 3-68 3.76 3-80 3 -86 3.99 4.07 4.25 .1.30 4'13 3 '91 ~ ~ January ...February ... March ... April ... May ... June ... July ... August . . . September.. . October ... November . . . December ,.. Average.. , 12.55 12.53 12-46 12.36 12'22 12.16 12'26 12.40 12.5; 12.78 12'98 12.;; 12'50 8 '97 8.98 8.96 8.94 8 *93 8-93 8.85 P % i 8 *92 9 .oo 9.00 8.96 8 '91 1 -0324 1 -0325 1.0324 1 *0323 1.0384 1 *0324 1.0319 1.0318 1 -0320 1'0322 1.0321 1.0521 1.0322 12.71 12-70 12.61 18-48 12.46 12-45 12-46 12-61 12.76 13-00 15.12 12.93 12-69 3*;3 3.70 3-64 3-55 3-52 3.51 3 %3 3.76 3.86 4.01 4-14 3.9; :3 ." - i a 3.61 3.55 3-50 3'42 3 2 9 3.23 5'41 3.53 3-65 3.78 3.98 3.81 3.56 12-85 12-87 7 2.76 12.59 12.70 12.74 12.67 12-83 12.96 13.23 13.2; 13.09 12.88 8'99 9.03 8 -97 8'91 8 -94 8 *94 8'81 8'84 8 *89 8 '98 8.97 8'96 8.94 1.0319 I n continuation of the tables published the two previous years (ASALYST, 1906, 31, 180; 1907, 32, 142), showing the incidence of low fats in the inorning iiiilk during May and June, I give the following results : Fat per cent.... ... ... ... 29-3-0 2.8-2.9 2-7-8.8 Below 2.7 Percentage of samples, May, 1907 , . . 3.2 2.0 0.2 0.7 9 9 ,, June, 1907 ... 5.7 2.0 1.0 0.8 TIip li'xamiiintioiz of H?imnii Xilk.--Eight samples of huiiian inilk during 1907 These figures do not appreciably differ frorn those found in 1906. gave the following results : TABLE 11. COMPOSITION OF HUMAN MILK. Specific gravity Total solids Fat ... ... Proteins ... Ash ... ... Solids-not-fat . . . Sugar , . . ... Acidity.. . ... - 1.0314 12.09 10.50 3.40 2.20 7.06 7.07 1.37 1.03 0.26 0.20 8-69 8.30 5.50 2-ao 1.0320 10.37 2-10 7-09 0.98 0.20 8.27 3.7" 1.0320 10.42 2.20 6.95 1 -06 0-21 8.22 3Y0 1.0274 13-32 5.17 6-97 1.01 0.17 8-15 3.7" 1.0287 12.73 4.38 6.87 1.30 0.18 8.35 4.7" 1.0287 12.25 4.05 7-03 0.99 0.18 8-20 9.3" 1.0320 10.10 1-70 7.24 1.04 0.22 8.40 5.5" The wide variation in the fat is remarkable.Proteins and Aldehyde E'iyure.-The aldehyde figure was shown by Steinegger (ANALYST, 1906, 31, 45) to correspond fairly well with the percentage of nitrogen inTHE ANALYST. 115 milk. E. H: ITiller and I ( ibic7., 1906, 31, 224) showed that the aldehyde figure depended to some extent on the alkali used, and practically confirmed the value given by Steinegger. From the result of a large number of estimations, I find that the alde- hyde figure obtained, using strontia as the alkali, multiplied by 0.171, gives the percentage of proteins in milk.From the results of twenty-four determinations on dried milks, I find that the aldehyde figure (expressed as C.C. of N / l alkali per 1,000 grams, not per litre as in the case of milk) multiplied by 0.175 corresponds with the proteins, the factor having varied from 0.185 to 0.162 ; as the average weight of milk delivered by a 10 C.C. pipette is 10.22 grams, these two factors are really identical. The probable error of a determination is k 2-9 per cent., with a maximum error of 7.4 per cent. ; this shows that the aldehyde method gives a rough and very rapid estimation of protein in milk, which is useful for control purposes. As the proteins of human milk are different from those of cow's milk, it is not surprising that the factors should differ.The factor varied from 0.153 to 0.124, and the proteins calculated from the aldehyde figure differed only in one case (0.13 per cent.) by more than 0.1 per cent. from the figure determined gravimetrically. The approximate constancy of the factor indicates that the aldehyde determina- tion will supply the want of a rapid method of protein estimation for clinical purposes that has been long felt. I t must be remembered, however, that the factors given above only apply to fresh milk. 13. H. Miller and I have shown that in sour milk the aldehyde figure goes up, due doubtless to protein hydrolysis (ibid., 1906, 31, 328), and Sorensen has lately published a paper in which this method is used to measure the extent of hydrolysis (Riocl~cm.Xeitsch., 1907, 7, 45).* Milk products also do not give reliable results with the fametor 0.171 ; for instance, the factor for whey is 0.125. The Relation bctzvecn Aldehyde Fiquw u72c7 A c i d i t y of illilX..--In a very large number of determinations on fresh milk it has been found that the two figures differ by less than 9.0" in practically every case. I n only seven samples, all the In nine samples of human milk the factor has been found Co be 0.136. milk of single cows, has a greater difference been found, and six of these are <' abnormal " inilks The following are the figures : > m 1. 3. -1. . ). ti. I . Acidity ... . . . 11.0" l i a . 3 " 15.3" 23.5" 14.9" 14 '3" 23.0" Aldehyde figure . . . 19.5O 21.1" 3 1 . 1 O 16.4" 20.2" 1'3.3" 19.0" Solids-not-fat ...7.01 8.27 5.23 7.64 8.07 7-90 8.53 ' Since reitding tlic: paper I have made soiiie determinations of the inllueiiw o f age on the ddehyde tigure. The results, wliich are the mean of seven deterniinatioiis each on milk keik a t 'LO" C . , show that so long as the milk has not curdled the cliaiige in the aldehyde figure is within the liiiiits of experi- inentitl error ; hut that thcrc is an appreciable increase after the acidity is sufficient to curdle the milk spontaneously. Fresh . . , . . . . . 20%' 20.5" 'LO hou1s ... ... 22.4" '20 .$', 2s , 9 27 -O'> 21.1" 45 :' 58.2" 21 '1 ' 69 ,, ... . 103'8" 22.2 l i g c of Milk. Scidity. Aldehyde Figure. 9.7 ,) ... 118'8" 22 .i'116 THE ANALYST. This fact may be of some use in determining whether samples of milk are sour, especially as a standa>rd for ‘( acidity ” has been proposed.It occasionally happens that milk has a high natural acidity, and in such cases it is shown to be natural by a high aldehyde figure. A New I’wservative.-In view of the recent successful prosecutions for the use ol boric acid in cream, a number of preservatives which it is claimed cannot be detected have been put on the market. Many of these consist essentially of benzoates, and one, which has recently come into my hands, contains formic acid as the preservative agent. I t is a syrupy liquid with a smell resembling ethyl butyrate. The acidity corresponded to 27.7 per cent. of formic acid, and when distilled according to Duclaux’s method, the rctte of distillation of the acid relative to that of water varied from 0.39 to 0.41, giving a mean of 0.40, which I have shown to be that of formic acid (ANALYST, 1895,20,193); it gave all the reactions of formic acid.On drying iiz vaczio at 70” a glassy residue amounting to 41.3 per cent. was left; this reduced Fehling’s solution, and the [u]D was 137.3” ; cane and invert sugar were proved absent Ly Cayaux’s test (Cl~enz. Zeiztr., 1898, 2, 510 ; cf. Anderson, ANALYST, 1907, 32, 87). The ash was 0.4 per cent. From these results it appears that the substance is a mixture of formic acid and commercial glucose, containing a little ester to disguise the smell of the acid. I do cot think that the detection of formic acid is an insuperable problem, especially as at least 0.06 per cent.of formic acid must be used to have a preservative effect. In small amounts, like many other prescriptions, it hastens the development of acidity. DISCUSSION. Dr. Yoer,cmIt said that, although the views formerly held in regard to the i tifluence of food on the quality of milk had of late undergone considerable modifica- tion, and even bearing in mind the fact that Mr. Richmond’s samples were drawn from particularly good sources, he was somewhat surprised to learn that the 190‘7 figures were so like those of 1906. The season of 1907 had been such an exceptional one, alike as regards the absence of warmth, the rapid growth of pastures, and the heavy yields of hay, that he would certainly have expected that, if any modification whatever in the composition of milk could be produced by feeding, it would have been shown in 1907. Mr. GOLDIPU’G asked to what extent the age of the milk influenced the aldehyde figure, and whether it wag possible to determine this when the milk was not fresh. Mr. RICHMOND said that the figures certainly showed to some extent the influence of the season, but it was not very marked in the quality of the milk, though the influence on quantity was great. I t would be seen that the rise in fat in the autumn was greater than usual, while in the spring and summer there was a slightly smaller percentage of fat than in 1906, which in the average figures was niore than com- pensated by the rise in the autumn. The age of the milk certainly influenced the aldehyde figure. I n a paper which Mr. Miller and he had read before the Society (ANALYST, 1906, 31, 32H), a number of results were given showing the increase in theTHE ANALYST. 117 aldehyde figure in sour milk. This increase was probably due to hydrolysis of the proteins into proteoses, and then probably into polypeptides, the latter bodies being (L-amino-acids, of which the aldehyde figure was a measure.

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DOI:10.1039/AN908330113b

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年代:1908

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THE ANALYST. 117 AN APPARATUS FOR QUANTITATIVE ESTIMATIONS INVOLVING DISTILLATION. BY GILBERT T. MORGAN AND TAYLOR COOK, B.Sc. THE opjration of distillation is so frequently employed in analytical chemistry that it is scarcely necessary to ernphasise the importance of carrying out the process in apparatus suitably arranged for separating quantitatively the volatile and non- volatile constituents of the material under examination without risk of contamination from extraneous substances derived from corks and indiarubber stoppers or connec- tions. It is with this object in view that, in recent years, many pieces of apparatus have heen devised in which cork or indiarubber fittings have been replaced by ground- i n stoppers and joints. Apparatus arranged in this way is inore costly and less easily repaired than a series of distilling flasks and receivers connected with cork or india- rubber stoppers, but these disadvantages are more than compensated by the increased accuracy and certainty of the results obtained ; moreover, certain operations involviug the use of corrosive liquids or vapours cannot be performed satisfactorily unless the apparatus is constructed entirely of glass, or some other equally resistant material.One of us (‘li.nns. Che?n. Soc., 1904, 85, 1002; ANALYST, 1904, 29, 268) has described a modification of Piloty and Stock’s method for the separation of arsenic and antimony (Bcr., 1597, 30, 1649): in which a distilling apparatus with ground-in glass connections was employed. The process, as carried out in this apparatus, has eince been applied with uniform success to the analysis of tetrahedrite (“ fahl ore ”) and other arseniferous minerals.The apparatus has also been utilised in the quanti- tative hydrolysis of organic amides, such as acetanilide and oxanilide. As the addition of a few modifications to the original apparatus seemed likely to render it serviceable for a much more extensive range of estimations, we have devised the apparatus described in the present pa;er. The original distilling apparatus consisted essentially of a Wurtz flask (about 300 C.C. capacity), the outlet tube of which carried a Kjeldahl safety bulb, and was elongated and bent first upwards and then downwards, so that it finally dipped into a, large conical receiving flask. The ground-in stopper of the distilling flask formed part of an inlet tube passing almost to the bottom of the vessel.In the modified apparatus the general principle of the older form is maintained, but the ground-in stopper, b, of the distilling flask, a (capacity 1,300 c.c.), is modified 80 as to admit of the introduction during distillation of a liquid as well as a gaseous reagent, the gas or vapour being introduced through the side tube, c, whilst the liquid is added through the tap-funnel, d , which forms a vertical prolongation of the hollow stopper. The outlet tube, e, carries a safety Kjeldahl bulb, f (about 18 inches118 THE ANALYST, in diameter), and is afterwards bent round and made to terminate in a ground-glass end fitting tightly into the top of a condenser, g, which is conveniently of the form devised by Cribb.The outlet tube of this condenser is elongated sufficiently to allow of its dipping under the surface of any absorbent liquid contained in the receiver (not shown). This receiver generally takes the form of a conical flask with Peligot f 1 safety tubes, but the size and shape of the vessel arevaried according to the require- ments of the estimation. The apparatus is also provided with a duplicate distilling flask, Ic, of smaller capacity (300 c.c.), the neck of which is made somewhat longer than that of the large distilling flask, in order that the inlet tube may almost reach the bottom of the vessel in each case. The neck of the smaller flask and the ground-glass termination of its aide tube fit the same stopper and condenser respectively as those employed with the large flask.THE ANALYST, 119 This duplication of the distilling flask enables one to carry out operations with varying volumes of liquid, and does not greatly add to the cost of the apparatus.The following estimations are cited as examples of analytical processes which can be conveniently carried out in this apparatus, but the list is by no means ex haus t ive : 1. Estimation of Aiiiinoitin in A4m?iaoiziii,n~ Salts.-The substance is distilled with either aqueous caustic soda or milk of lime, the smaller flask being generally em- ployed in this analysis. Volatile organic ainines could obviously be estimated in :L similar manner. iVitrites by lieduct iou to Ammonia.---These sub- stances were reduced with Devarda’s alloy (aluminium-copper couple) and dilute caustic soda.3. Estimation of Nitrogen by Kjelclahl’s Method.-After destroying the organic matter in the customary manner, the contents of the decomposition flask, con- siderably diluted with water, mere transferred to the larger distilling flask, rendered alkaline with caustic soda, and distilled in steam. 4. Estimations involving the Distillation of Chlorine.-Substances evolving chlorine on treatment with hydrochloric acid can be analysed in this apparatus, the distillation being cltrried out in a current of air or carbon dioxide. The smaller flask is generally employed in these estimations, and is conveniently heated to boiling in a, glycerine or fusible metal bath. This mode of conducting the operation in a current of some inert gas is preferable to distillation in closed vessels, inasmuch as by the former arrangement the internal pressure of the distilling flask need never differ greatly from the atmospheric pressure, thus avoiding any risk of regurgitation from the receiver into the distilling flask.In these experiments the condenser has the useful effect of cooling thoroughly the hydrochloric acid solution which distils over, so that the risk of decomposing any hydrogen iodide by local heating is reduced to a minimum. 5. Sepamtion of the Halogem.-This apparatus is suitable for the separation of chlorine, bromine, and iodine, when present in the form of soluble halide salts, by Jannasch and Aschoff’s method (Zeit. mzorg. C’hem., 1893, 1, 144 and 245 ; also Classen’s Ausgewdhlte Mcthotlen der -Iiznlytischen CJLemic, vol.ii., p. 402). A mixture containing approximately 0.5 gram each of potassium chloride, bromide, and iodide wag introduced into the larger flask, and treated with 1 gram of sodium nitrite and 5 C.C. of 2 N-sulphuric acid dissolved in 750 C.C. of water, the mixture being then distilled in steam until the iodine was entirely expelled, and collected in an aqueous solution of 2.5 grams of sodium hydroxide and 50 C.C. of pure hydrogen peroxide. The liquid in the receiver was boiled with more hydrogen peroxide, to decompose any nitrite, and the iodide then estimated as silver iodide. The solution in the distilling flask wag rendered slightly alkaline with sodium hydroxide, concentrated to 500 c.c., treated with 1 to 1.5 grams of potassium permanganate and 60 C.C. of acetic acid (1 acid, 2 water), and again distilled in steam until all the bromine was expelled and con- verted in the receiver into sodium bromide by the action of sodium hydroxide and hydrogen peroxide.The final residue in the distilling flask w&s treated with alcohol The base is in each case expelled with steam. 2. Estiinntion oj- Nitrates The distillation was efYected in a current of stearn.THE ANALYSTo and sodium hydroxide, to remove excess of manganese, and the chloride estimated as silver chloride. 6. Estimation of Boric dcid.-In this estimation the method of Rosenbladt and Gooch was followed (Zeit. anal. Chem., 1887, 26, 18 and 364), the distillation being effected in the smaller flask at 140” C.The volatilised boric acid was collected in milk of lime containing a known weight of calcium oxide, and weighed as ignited calcium borate. 7. Separation of Anenac and Antimony (Thorpe, Qfiantitatice Analysis, ed. 1891, p. 277; and Trans. Chewt. SOC., 1904, 85, 1002). - I n the analysis of tetra- hedrite and other arseniferous minerals the finely powdered substance is heated in a current of chlorine until the chlorides of arsenic and antimony are expelled and collected in a solution of tartaric acid in concentrated hydrochloric acid, from which the sulphides of these elements are subsequently precipitated by hydrogen sulphide. The mixed sulphides suspended in concentrated hydrochloric acid are distilled in the apparatus in a, current of hydrogen chloride, the arsenic being volatilised as chloride, and reprecipitated as sulphide in an ice-cold saturated solution of hydrogen sulphide contained in the receiver.A sample of tetrahedrite gave the following percentage results : As = 2.23, 2.16 : Sb =; 11.68, 11-74, I t has already been pointed out by one of us (ANALYST, 1904, 29, 268) that the distillation in hydrochloric acid as carried out in this apparatus may be employed to separate arsenic in its two states of combination, providing that the acid employed does not at any stage come into contact with organic materials, for, as Hehner has shown (ibid., 1902, 27, 268), boiling hydrochloric acid free from organic or other reducing agents does not effect any considerable reduction and consequent volatilisa- tion of arsenic present in the quinquevalent condition.8. Proximate Organic Analyses - (a) Estimation of d cetic Acid iit Acetates aid Acetyl Derivntives.--The smaller distilling flask was employed, and the acetate or acetyl derivative distilled in steam with excess of phosphoric acid, the flask being heated in a glycerine bath. The acetic acid was collected in standard caustic soda. Acetanilide and ‘( aspirin ” (acetyl-salicylic acid) were chosen as types of acetyl compounds which are amenable to this treatment. The process is applicable to the estimation of other volatile acids. ( b ) Estiwzatioiz of Methoxyl by Zeisel’s Method.-We find that the smaller flask, with its long neck and bent side tube, giving a total length of 12 inches from the bulb of the flask, plays the same part as the long-necked Wurtz flask employed by W.H. Perkin, sen., in a simple modification of Zeisel’s process (Trans. Chem. SOC., 1903, 83, 1368), whereby a fractionation of hydriodic acid and methyl iodide is effected, the latter alone distilling forward. The outlet tube of the condenser g is placed directly over the alcoholic silver nitrate, so that the vapour of methyl iodide never comes into contact with absorbent corks or india-rubber fittings until it has been at least once in contact with the silver solution. For comparatively simple compounds the hydriodic acid (specific gravity 1.68 to 1.70) was used alone, but with more complex substances it was mixed with acetic anhydride.THE ANALYST. 121 A proximate analysis of phenacetin (acetyl-p-phenetidine) showed that the apparatus may also be employed in the estimation of ethoxyl. SUMMARY OF ANALYTICAL RESULTS. Ihtimation of ammonium salts : 1. NH, ... ... ... ... ... 2. NH, ... ... ... ... ... Estimation of nitrates by reduction to ammonia Estimation of nitrogen by Kjeldahl’s method. N Estimations based on chlorine distillation : 1. I<CIO, ... ... ... ... ... 2. K,Cr,O, ... ... . . . ... ... Separation of the halogens : ... ... . . . ... ... ... . . . ... ... !EL..*- ... CKCl ... . . . ... ... ... Estimation of boron. B,O, ... ... ... 1. Acetates. CH;CO,H ... ... ... Estimation of acetic acid : 2. Acetyl derivatives. (i.) COCH, ... (ii.) COCH,, ... I<stimation of methoxyl. CH;O ... ... l’rosimate analysis of phenacetin : C,H,OC,H;NH*COCH,. (i.) CO*CII,, ... (ii.) C,H;O . . . 1.’ o ii 11 d . 3-79 per cent. 3147 ,, 13.62 ,, (32.86 ,, 132.69 ,, 0.6415 gram. 0.2315 ,, 0.3170 ,, 0.3039 ,, 0.4055 ,, (36.26 per cent. (36.31 ,, 59.81 ,, 23.0 ,, (31.46 ,, (31.40 ,, ( 7.93 ,, \ 8.01 > I 23.50 ,, 25.75 ,, Calciilated. 3.75 per cent. 31.76 ,, 13.86 ,, - T;tkcu. 0.6426 gram. 0,2314 ,, 0.3182 ,, 0.3057 ,, 0.4032 ,, Calciila tecl. 36434 per cent. - 60.30 ,, 23.7 ,, 31-85 ,, -- 8.20 per cent. 24-20 per cent. 35-14 ,,

ISSN:0003-2654    

DOI:10.1039/AN9083300117

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年代:1908

数据来源: RSC

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THE ANALYST. 121 OBITUARY. J . HAXDDY BALL, hl.Sc., F.T.C., from pneumonia, at Limerick, in February. JAMES BELL, C.B., D.Sc. (Dublin), Ph.D. (Erlangen), formerly Principal Chemist t o the Inland Revenue, on March 31st, at Hove.

ISSN:0003-2654    

DOI:10.1039/AN9083300121

出版商:RSC    

年代:1908

数据来源: RSC

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122 THE ANALYST' ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. Estimation of Cocoanut Oil in Butter. R. Ross and J. Race. (Chent. Nczos, 1908, 97, 110-111.)-The process described by Hodgson (ANALYST, 1908, 49) is considered by the authors to be useless for detecting the presence of cocoanut oil in butter. I n the first place, the quantity of sulphuric acid prescribed has itself a considerable action on the permanganate used for the oxidation. With smaller quantities of acid and in the absence of fats, concordant results may be obtained ; but the oxygen equivalents obtained by oxidising fats in the presence of small quantities of acid are unsatisfactory for the purpose of differentiating one fat from another. Two sainples of butter yielded oxygen equivalents of 60.0 and 62.3, whilst two samples of cocoanut oil gave equivalents of 54.7 and 57.6 respectively.Further experiments, in which fats and fatty acids were oxidised in both acid and alkaline solutions, yielded no better results. I t is pointed out that the diEerence in the oxygen equivalents of fats arid their fatty acids is due to the glycerol and the soluble fatty acids. As butter and cocoanut oil contain approximately the same quantity of glycerol, it follows that the soluble fatty acids, which are present in only very small quantities, must have a considerable oxygen equivalent. There is, further, a considerable difficulty in obtaining a definite end reaction in the titration, owing to the retention of manganese hydroxide by the insoluble fatty acids. w.Y. s. Estimation of the Caprylic Acid Value of Butter-Fat. R. K. Dons. (Zeit. Untersuch. N ~ w . Genussiib., 1908, 15, 75-79.) -The following method for the estimation of the caprylic acid value of butter and other fats (c-f. ANALYST, 1907, 32, 383) is described. It depends on the fact that caprylic acid, when mixed with myristic, palmitic, and oleic acids, is practically insoluble in water. The butyric and other volatile acids may therefore be extracted from the mixed fatty acids with water, and the caprylic acid afterwards separated from the insoluble acids by distillation. Five grams of the fat are saponified in the usual way; the soap is dissolved in 100 C.C. of hot water, and decomposed by the addition of 50 C.C. of dilute sulphuric acid. The mixture is placed aside until the fatty acids have solidi- fied, and the clear aqueous portion is drawn off.The cake of fatty acids is now shaken twice with 150 c c . of water a t a temperature of 80" C., and the aqueous extracts are removed. The insoluble fatty acids are then placed in a flask ; 150 C.C. of water, 20 grams of glycerol, 5 grams of sodium sulphate, and a few pieces of pumice-stone, are added, and the whole is distilled until 110 C.C. of distillate have been collected, The addition of the glycerol and sodium sulphate makes the conditions of the distillation the same as in the ordinary Reichert-Meissl distillation. The distillate is filtered, 100 C.C. of the filtrate are neutralised as usual, aud theTHE ANALYST, 123 caprylic acid value of the neutral solution is estimated as described previously.A correction is applied for the solubility of the silver salt in the volume of solution, and wash water used-namely, 0.4 c.c.-which is added to the value obtained. Under these conditions pure butter-fat gives a value of froin 1.6 to 2-0; butter-fat mixed with 10 per cent. of cocoanut oil 2.6 to 3.0; and pure cocoanut oil 5.3. w. P. s. The Refraction of Butter-Fat and its Non-volatile Fatty Acids. A. G. Breen. (Zed Untersuch. Nahr. Gemssm., 1908, 15, 79-80.)-The results of deter- minations of the refractonieter values of forty-eight saniples of butter, and of the insoluble fatty acids obtained from the butters, are given. The figures show that the refractions of the fatty acids do not lie within narrower limits than those of the butter-fats themselves.Whilst the values for the butter-fats varied from 44.1 to 46.8 at 40" C., a difference of 2.7, the refractonieter values of the fatty acids were from 39.6 to 3 6 3 , a variation of 3.7. I\'. P. s. The Relation of the Iodine Value of Lard to the Refraction of the Latter. G. Halfpaap. ( Z e d . 0-utersuch. Nahr. Genussm., 1908, 15, 65-72.)--Xlthough the refraction of lard generally bears a distinct relation to its iodine value, this relation being especially marked in the case of the insoluble fatty acids yielded by the lard, instances are met with where lards having the same refractometer value show different iodine values. This diEerence is considered by the author to be due to the high refraction of some of the lards and the fatty acids obtained from the same.The high value does not depend on the presence of oxy-acids, but is either the result of polymerisation or the formation of lactonep, or more probLtbly a partial change of the oleic acid into iso-oleic acid. w. P. s. Vegetable Fats used as Substitutes for Cacao Butter in Chocolatew 0. Sachs. (Chem. lieu. Fett. ZL. Harx-Ind., 1908, 16, 9-10, 30-33.)-0Of recent years various exotic fats have been used as substitutes for cacao butter in the manu- facture of chocolate, the chief of these being Dika or Gaboon fat (ANALYST, 1905, 30, 394), Tankawang fat (Borneo tallow), and Illip6 fat. Dika fat differs from cacao butter in its higher melting-point and lower iodine value (5-2), whilst it may be readily distinguished from cocoanut '' stearin " by its higher melting-point. Borneo tallow has the following average values : Melting-point, 37.5" C.; solidification- point, 22.0" C. ; iodine value, 30 to 31 ; saponification value, 192.4 to 196; specific gravity at 100" C., 0.8920 ; melting-point of fatty acide, 53.5" C. ; solidification-point of fatty acids, 52.0; iodine value of fatty acids, 31.5; and mean molecular weight of fatty acids, 273.5. I t differs from cacao butter mainly in its lower melting-point and higher iodine value. On the other hand, Illiph fat has a considerably higher iodine value (53.4 to 60), but lower melting-point (24" to 29" C,), than cacao butter. steurins " obtained by expression of cocoanut oil and palm-nut oils are also used as cacao-butter substitutes, usually in adinixture with other vegetable fats.The following values were given by commercial samples : Hard cocoanut stearin : Melting-point, 29.3" to 29.5" C. ; solidification-point. The124 THE ANALYST. 26.5" C. ; specific gravity at 100" C., 0.8700; saponification value, 252 ; Reichert- Meissl value, 3.4 ; iodine value, 4.01 to 4.51; melting-point of fatty acids, 28.1 ; solidification-point of fatty acids, 27.4 ; and mean molecular weight of fatty acids, 209. Palm-nut '' stearin " : Melting-point, 31.5" to 32" C. ; solidification-point, 28" C. ; specific gravity at 100" C., 0.8700 ; Reichert-&hiss1 value, 2.2 ; saponification value, 242 ; iodine value, 8 ; melting-point of fatty acids, 28.5 to 29.5 ; solidification-point of fatty acids, 28.5; and mean molecular weight of fatty acids, 211.A mixture of 75 per cent. of cocoanut (' stearin " with 25 per cent. of Japan wax has given good results as a cacao-butter substitute, and a commercial (Swedish) pro- duct of this composition gave the following results : Melting-poi.nt, 34' to 35.5" C. ; iodine value, 7.8 ; saponification value, 237 ; and Reichert-Meissl value, 5.5. Aniong other favourite substitutes, special mention may be made of a mixture of two-thirds of palm-nut '' stearin " with one-third of cocoanut '' stearin," and of a mixture of 40 per cent. of Tltnkawang fat with GO per cent. of cocoanut " stearin." C. A. M. Constituents of Coffee and Estimation of Caffeine. K. Gorter. (Annalen, 1908, 358, 327-348.)-A hitherto unknown acid (cofulic acid) has been isolated from coffee by the author.I t forms crystalline prisms (melting-point 255' C.), and yields isovalerianic acid when boiled with alkalies. The '' caffetannic acid " of earlier investigators appears to consist of a mixture of this acid with chlorogenic acid, C32H3S01!l, and other uninvestigated substances. A considerable proportion of the caffeine in coffee (1.1 per cent. in a sample of Liberian coffee) is present in the form of the double compound-potassium caffeine chlorogenate, C,,H360,,K,(C,H,oN,0,), + 2H,O, which crystallises in white prisms, turning yellow at 150" C., and brown at 225" C., without melting. The caffeine can only be extracted with great difficulty from this compound by means of dry chloroform, only one-tenth of the total quantity being obtained after nine hours' extraction in one experiment.When the coffee is moistened, however, the whole of the caffeine is readily removed by chloroform within three hours. On this fact is based the following method of estimation : Eleven grams of the finely-powdered coffee are moistened with 3 C.C. of water, and, after standing for thirty minutes, extracted for three hours in a Soxhlet's extractor by means of chloroform. The extract is evaporated, the residue of fat and caffeine treated with hot water, and filtered through a plug of wool and washed with hot water. The filtrate and washings are rnade up to 55 c.c., and 50 C.C. withdrawn by means of a pipette and extracted with four successive portiona of chloroform. The new extract is evaporated in a tared flask, and the residue of caffeine, which is nearly white, dried at 100" C.and weighed. C. A. Ill. I t is soluble in water, yielding a slightly acid solution. Fruit-Juice Statistics for the Year 1907. (Zeit. U7ztersuch. Nahr. Genussm., 1908, 15, 129-148.)-The following are the average results of analyses of fruit-juicesTHE ANALYST. 125 recorded by A. Behre, F. Grosse, K. Thimme, E. Baier, P. Hasse, K. Fiecher, K. Alpers, F. Schwarz, and 0. Weber : Kind of ,Jnice. Raspberry, forty-seven samples ... ... Strawberry, six samples ... ... ... Currant, twelve samples . . . ... ... Cherry, fourteen samples ... ... ... Bilberry, eight samples ... . . . ... Blackberry, five samples ... ... ... Gcoseberry, six samples ... ... ... Cranberry, six samples ... ... ... Elderberry, six samples ...... ... Total Solids. Grams per 100 C.C. Ash. Grams pcr 100 C.C. 4.84 6.33 4-86 10.23 6-74 4.10 3-66 11.50 5.53 0.53 0-60 0.51 0-50 0.29 0.49 0.43 0.35 1.01 Alkalinity of Ash. C . C . N/1 Acid per 100 C.C. 6.24 7-08 5-22 5.25 2-95 6-87 4.38 2.27 1 2 28 w. P. s. The Pulp known as " Nette Meal." A. Goris and L. Crete. (Co?uptcs Rmd., 1908,146,187-189.)--" Netti! meal " is produced from the fruit of the leguminous plant Parkia bigZobosa,Benth., and is highly valued as a food by the natives of tropical Africa. I t is formed within the pod, and when the latter is ripe is a dry, friable substance. A sample twomonths old gave the following analytical results : Water, 4.9 ; ash, 4.96 phosphoric acid ( Y 2 0 j ) , 0.383 ; nitrogen, 0.624 ; substances soluble in carbon bisul- phide, 1.30 ; substances soluble in alcohol, 56.67 ; and substances soluble in water, 72.0 per cent.The fatty substances dissolved by the carbon bisulphide were of a yellowish-red colour, and had the consistency of butter and an odour like that of the pulp. The unsaponifiable matter contained a '' cholesterol " melting at 135' C., and having [ a ] ~ = - 36" in chloroform solution. A pectin with a rotation of +226" was precipitated by the addition of alcohol to the aqueous extract. The meal contained about 25 per cent. of cane-sugar and 20.5 per cent. of dextrose and laevulose, but was free from starch. The proportion of cane-sugar apparently diminishes by inversion on keeping, for certain old samples have been found to contain only dextrose and laevulose.C. A. M. Neurokeratin. A. Argiris. (Zed. physiol. Chem., 1907, 54, 86 ; through Chem. Zeit. Rep., 1908, 32, 107.)-Neurokeratin wm prepared (from human brains) by a modification of the process employed by Kiihne and Chittenden. On hydrolysis this substance yielded- Per Cent. ... ... ... ... ... Lysine ... 2.72 - 2.68 Arginine ... 2-28 - 2.19 Histidine ... ... . . . ... .. 0.76 Tyrosine ... ... ... ... ... 4.60 Cystine ... . . . ... ... ... 1.50 J. F. B. ... ... ... ... ...126 THE ANALYST. Note on Saffron. A. E. Parkes. (Pharm. Jozwn., 1908, 80, 267.)-The figures in the first two columns show the composition of two samples of genuine *' Valencia" saffron examined by the author, while those in the third column represent the average analysis of eight samples by other observers : Total ash ...... ... ... ... Ash insoluble in water ... ... ... Ash insoluble in diluted HCI . . . ... Alkalinity of ash (= C.C. of i'$ acid per 1 gram sample) ... ... ... ... Loss at 100" 0. ... ... ... ... Ether extract ... ... ... ... Extracted by 60 per cent. alcohol ... Cold-water extract ... ... ... Ash of water extract ... ... ... Nitrogen ... ... Woody fibre ... ... . . . ... Potassiuni oxide, K,O ... ... ... Colour with sulphuric acid .., ... ... . . . ... 1. Per Cent. 4.95 1.75 0.50 2.75 C.C. 10.86 1.52 56.76 51.50 3.60 1-90 3.70 2.37 blue 2 Per Cent. 5.00 1-60 0.25 2.80 C.C. 12-40 1 -68 55.92 50.30 3.20 1 *85 3.21 2.39 blue Average of Eight Sani ples. Per Cent. 5.0 1-7 - 3.2 C.C. 11.73 - __ 51.07 3.56 1.94 3-16 - blue Samples of commercial ( ( saffron " were found by the author to be adulterated with potassium nitrate, borax, barium sulphate, sand, and foreign fibres (such as those of sedge grass) dyed a red colour.A. R. T. Characteristics of Solanine from Solanum tuberosum and S. sodo- maeum. A. Colombano. (Gazz. Chim. Ital., 1908, 38, 19-37.)-Elementary analyses of preparations from tbe shoots of the potato and of purified commercial samples of solanine agreed with the formula C,,H,,NO,,, which differs greatly from that found by previous chemists (Cazeneuve and Breteau, C,,H,7N0,, ; Hilger and Merkens, C,2H77N0,,). The average results of analyses of the solanine obtained from S. sodomaunz corresponded with the formula, C27H,7N0,, whilst the physical and chemical properties of this compound were also distinct.Solanine from the potato decomposed completely at 260' to 263' C., and when kept a t 250° to 254" C. changed to a gummy yellowish-red substance, whilst the solanine from S. sodomaurn only became brown. The specific rotation, determined in dilute sulphuric acid solution, was - 42.34" to - 42-59" at 25' C. for the potato solanine, and - 58-31" at 24' C . for the other solanine. The latter treated with 2 per cent. hydrochloric acid gave a clear solution, which on standing deposited a crystalline hydrochloride, C27H,7N0,HCl,, whilst no deposit was given by the solution obtained under similar conditions from potato solanine. Different products were also obtained when the two compounds were hydrolysed. C. A. M.THE ANALYST. 127 The Testing of Sperm Oil and Spermaceti.H. Dunlop. (Joum. Soc. Chem. Id., 1908, 27, 63-65.)-The following table gives the results obtained on the examination of several samples of Southern and Arctic oil which were obtained from reliable sources ; it also gives the figures for a sample of whale-blubber oil : Zeiss Refrac- tonieter Value at 25" c. Free Acid Oleic). Per Cent. (a? Specific Gravity a t 15.5" C. Wax Alcohols, etc. Per Cent. Saponifi- cation Value. Per Cent. Iodine Valne (Wijs). 4.60 1.42 1.39 1.07 0.73 1-43 1-16 2-53 6.28 l a . Cachalot oil (head) ... l b . 9 , (body) * . * 2a. ,, (head) ... 2 b. 9 , (body) - - a 3. Arctic sperm (bottle-nose) 4. Y , 9 , 5 . Southern sperm ... ... 6. ... 7. W hale-diubber oii' * ... 0.8779 0.8772 0.8890 0.8757 0.8806 0.8786 0,8791 0.8798 0.9241 42.28 42.14 41-16 44.30 38.02 39.22 41.16 39.20 - 76.30 92-85 70.35 87.90 88.75 82.80 84.35 84.37 136.3 0 14-02 1.2-48 14.44 12.90 12.90 12.48 12.97 12.90 19.28 49.7 54.8 50.0 54.6 55.2 55.3 54.6 70.5 - The author considers that the unsaponifiable matter (wax alcohols) should lie between 36 and 44 per cent., although by far the greater number of oils will give a figure between the limits 38 and 42.The presence of mineral oil in a sample is detected chiefly by the quantity of unsaponifiable matter yielded by the oil, and, with the exception of Holde's test, which consists in adding water to an alcoholic solution of the saponified oil, when the mineral oil is thrown out of solution, the wax alcohols remaining dissolved in the soap solution, there appears to be no satisfactory test for mineral oil in sperm oil.From 1-36 to 2-56 per cent. of glycerol was found in the oils. The results of the analyses of five samples of spermaceti are given in the following table. The samples 1 and 2 were prepared in the laboratory from the (' head matter " of the Cachalot whale. I ~ \\'as Alcohols, etc. Per Cent. Melting-point of Fatty Acids. O c. Me1 ting- iboiii t. c. Solidify- ng-poin t. C. Iodine Value (Wijs) . Fatty Acids. Per Cent. NO. 32-33 39-5-40 - - - 1. 2. 3. 4. 5. 41-41.5 41-42 44-44.5 45.5-46 45-45.5 41.0 44.0 45.7 45.0 - 54.22 53.20 53.00 51.56 - 49.78 50.58 - - -- 12.90 12.90 12.06 112.18 12.06 w. P. s. - 9.33 7.21 5.32 5.50 Estimation of Esters in Wines. G. Austerwell and P. Pacottet. (Chem. Zeit., 1908, 32, 112-113.)-Untrustworthy results are obtained if the esters be esti-128 THE ANALYST.mated in the distillate of a wine distilled in the usual manner, and the authors there- fore described a method in which the wine is distilled under a very low pressure, the distillate obtained being employed for the estimation, Preliminary experiments were made with known quantities of ethyl acetate and amyl butyrate, to show that the process gives accurate results. From 100 to 250 C.C. of the wine are placed in a flask surrounded by a closed vessel containing ether, this vessel being provided with a reflux condenser to prevent loss of ether. The ether is boiled, and the distillation flask is connected with a condenser and receiver, the latter being surrounded by a mixture of ice and common salt, and the receiver is in turn con- nected with an exhaust pump, by means of which the pressure in the apparatus can be reduced to 60 mm.When the volume of the distillate amounts to about one-- fourth of that of the wine taken for the estimation, the esters in the distillate are estimated in the usual way by saponification. I n four samples of champagne, from 0.065 to 0.124 gram of esters (calculated as ethyl acetate) per litre were found. w. P. s. Estimation of Starch in Maize by Calculation from the Yield of Extract. A. Frank-Kamenetzky. (Chcm. Zeit., 1908, 32, 157-159, 175-176.)- The method proposed by the author is based on the observation that the starch- contents of maize are directly proportional to the yield of extract obtained by the action of diastase uuder standard conditions.Consequently, if the starch equivalents of a series of maize extracts be determined by the usual process of hydrolysis by acid and estimation with E'ehling's solution, these may be tabulated, and future analyses will be confined to a simple determination of the extract and reference to the table for the corresponding starch equivalent. For preparing the extract, 0.2 gram of Merck's diastase is triturated repeatedly with. small quantities of water until the total solution amounts to 15 to 20 C.C. Five grams of very finely ground maize are placed in a tinned copper beaker of about 150 C.C. capacity, 20 to 25 C.C. of water are added, and 1 C.C. of the diastase solution. The beaker is placed in a water-bath, and its contents gradually heated to 70" C.Digestion is continued for one hour a t this temperature, care being taken to replace the water which evaporates, and to prevent the caking of the starch on the sides of the beaker. The water-bath is then heated to boiling, and the mash is stirred at that teniperature for fifteen to twenty minutes. I t is then cooled to 5 5 O C., and the remainder of the diastase is added; saccharification is continued for three to four hours, the temperature being gradually raised to 60" to 63" C. The complete conversion of the starch should be ascertained by the iodine test. The contents of the beaker are transferred to a measuring flask, cooled, diluted to 100 c.c., and filtered. The extract is then determined either by the immersion refractometer at a temperature of 17*5"C., or by the pyknometer used in connection with Balling's extract tables.The optical method is quite a s accurate as the density method, and more rapid. The results should be corrected for the extract due to the diastase when mashed with water alone. In the table below, the column "Apparent Starch " represents the values determined by means of Fehling's solution after hydrolysis of the filtered extracts by hydrochloric acid. The column headed Real Starch Equivalent '' is based on the assumption that the solidsTHE ANALYST. 189 of the extract, consisting of maltose and dextrin in the ratio of 3 : 1, have a, dextrose equivalent of 99 per cent., and are obtained by multiplying the solids expressed as grams per 100 C.C. first by 0.99 and then by 0.90, to reduce the dextrose values to starch, and calculating as per cent. of the maize. This column gives a far closer approximation to the true starch-value of the maize than the third column. The alcohol equivalent is 60 per cent. of the starch value. The method is of course applicable for the estimation of starch in other cereals, but the equivalents in the table worked out for maize would not be applicable to other grains. STARCH EQUIVALENTS OF MAIZE EXTHACTS. (5 ~ Y C L H L S X a i x c pel' 100 c.c.) Scale Divisioiis on Zeiss Immersion Refrnctometcr. Extract 13ullin g , Degrees. 9.9544 2.9801 3.0058 3.0315 3.0572 33.0839 Y.1086 3 * 13 43 3.1600 3 * 1 85 7 5.2114 3 * 2:3 7 1 3.2628 3.2885 3-3142 :3 * 33 99 3 * 3 666 3.3913 3.4170 3.4497 :I *4 68 4 3-4941 3 -5 19 7 Apparcn t Starcli Equivalent. Per Cent. 57.27 57.64 58.00 58.36 58.73 59.09 59-45 59.83 60.18 60.54 60.91 61-27 61.64 62-00 62.36 68.73 63.09 63.45 63.82 64.18 64-54 6491 tit5.37 Real Starch Equivalent. Per Cent. 53.33 53.70 54-18 54.66 55.13 55.60 56.08 56.55 57.02 57-49 57.97 58.44 58.9 1 59.38 59.86 60.33 60.80 61-23 61-75 (i2.22 63-69 63.17 ( i :-Z * 6 4 Real Alcohol Equivalent. Lit res . 31-94 :32*22 32.51 32.79 33.07 33-56 33.64 33.93 34-91 134.49 34.78 35.06 35-35 35.62 35-91 36-19 36.50 36-76 37.05 37.33 37.60 37-89 35.15 J. F. B.

ISSN:0003-2654    

DOI:10.1039/AN9083300122

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

THE ANALYST. 189 BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. The Peroxydase of Tyrosinase. A. Bach. (Chenz. Zeit., 19OS, 32, 178.)- By shaking with magnesium carbonate, and by precipitation with methyl alcohol, preparations; may be obtained from solutions of tyrosinase which alone have only it very slow action on tyrosine, but which produce the characteristic black oxidation product very rapidly in presence of hydrogen peroxide. The reaction may be followed130 THE ANALYST. quantitatively by titrating the black product with 0.009-N permanganate solution in presence of sulphuric acid. Tyrosine is not oxidised by hydrogen peroxide alone, nor by mixtures of this with the ordinary peroxydases. The author concludes that tyrosirlase consists of a specific peroxydase, together with an oxygenase, and that, as in the case of ordinary oxydase, the functions of the oxygenase constituent may be performed by hydrogen peroxide.The influence of the concentrations of the ferment solution and of the substratum on the course of the reaction may be studied by means of the permanganate method. The action of tyrosinase, at its middle stages when in full activity, follows the law of mass action, but at the beginning and at the end it departs from this law. J. F. B. Activity of Trypsin, and a Simple Method for its Estimation. 0. Gross. (Arch. experiment. Pathol. ?L. Phar.makol., 1907, 58, 157 ; through Chem. Zeit. Rep., 1908, 32, 77.)-One gram of fat-free casein is dissolved in 1 litre of 0.1 per cent. sodium carbonate solution, saturated with chloroform to prevent bacterial action. Portions of 10 C.C. each of this solution are then placed in test-tubes, heated to 40' C., and kept at this temperature after adding varying quantities of the trypsin solution. After a definite time, a few drops of acetic acid are added to each tube. If the liquid remains clear the casein was completely digested, the time taken being inversely proportional to the quantity of ferment present, the dilution being without influence. A. G. L.

ISSN:0003-2654    

DOI:10.1039/AN9083300129

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

130 THE ANALYST. ORGANIC ANALYSIS. Blackberry-seed Oil. R. Krzizan. (Chem. 12cv. Fett- u. Hurx-Id., 1908, 15, 7-9, 29-30.)-By extraction of the crushed seeds with petroleum spirit, 12.6 per cent. of a greenish-yellow oil with a red fluorescence, and possessing a characteristic odour, was obtained. The fatty acids were fractionated into 4.7 per cent. of solid fatty acids, mainly palmitic acid, and 95.3 per cent. of liquid fatty acids containing about 80 per cent. of linolic acid, 1.5 per cent. of linolenic acid, and 1-5 per cent. of isolinolenic acid. The tetrahydroxystearic acid obtained by oxidising the liquid fatty acids with alkaline permanganate melted at 161" C., instead of the usual 173Oto 174" C. The oil itself absorbed 6.87 per cent. of oxygen in three days in Livache's test, and dried in two to three days in the film test.It gave the following values : Specific gravity, 0.9256 ; acid value; 2.03 ; saponification value, 189.5 ; Reichert-Meissl value, 0.0 ; Hehner value, 96.3 ; iodine value, 147.8 ; and unsaponifi- able matter, 0.83 per cent. Fatty Acids.-Specific gravity, 0.9070 ; saponification value, 199.9 ; iodine value, 155 ; acetyl value, 13.9 ; and mean molecular weight, 280.9. The phytosterol (0.6 per cent.) separated from the oil melted a t 133" C . Neither Halphen's nor Baudouin's colour reaction was given by the oil. C. A. M. The Polarimetric Determination of Cane Sugar. Effect of Basic Lead Acetate on the Optical Activity and Copper-Reducing Power of Sugar Solutions. F. Watts and H. A. Tempany. ( J o z m . SOC.Chem. Ind., 1908, 27, 33-57.)-The authors show that excessive amounts of basic lead acetate exercise anTHE ANALYST. 131 appreciable effect on the optical activity and reducing power of solutions of invert sugar. When excess is avoided, and it is easily avoided in practice, clarification by dry anhydrous basic lead acetate involves no appreciable error. In raw-cane juices a slight excess of basic lead acetate produces a greenish-yellow coloration which may serve as an indicator for the process of Clarification. The reduction of the optical activity of solutions of invert sugar by basic lead acetate is due to the forma- tion of a soluble lead Itmulosate, which can only exist in presence of the basic group of the lead acetate. Low-grade products, such as molasses, can only be clarified by basic lead acetate solution if a large excess of the reagent be employed, and in such cases the errors involved by the volume of the precipitate and the action of the excess of lead on the locvulose are large.On the other hand, dry basic lead acetate only effects a partial clarification of such products. The authors prefer to add the dry basic lead acetate to a solution of twice the normal weight of molasses per 100 C.C. and filter. Of the filtrate, which is still dark, 50 C.C. are saturated with sulphur dioxide, diluted to 100 c.c., and filtered for polarisation. The use of animal charcoal is quite inadmissible. Clarified juices always contain small quantities of lead salts, but these are not sufficiently large in careful working to introduce an appreciable error in the determination of reducing sugars by Fehling’s solution. Direct experiments with solutions of pure invert sugar, containing about 0.5 gram per 100 c.c., showed that 1 C.C.of basic lead acetate solution caused the apparent removal of 0.006 gram of invert sugar, but since the total quantity of lead solution required for clarification rarely exceeds 2 c.c., there is little danger of an excess of 1 C.O. ever being present. J. F. B. A Colour Reaction for Carbohydrates and its Relation to their Molecular Weights. L. Wacker. (Ber. dczit. Ghem. Ges., 1908, 41, 266-275.) --p-Phenyl- hydrazine sulphonic acid condenses with aldehydes and alcohols of the aliphatic series, in presence of air and of alkali hydroxide in excess, to form red colouring matters.The shade of these colouring matters is approximately constant, so that their intensities are comparable and show the following regularities : The intensity of the colours of equimolecular quantities is constant ; i.e., the intensity due to equal quantities decreases with increased molecular weight ; the rapidity of the reaction is inversely proportional to the molecular weight, and is also proportional to the concentration. The simplest aldehydes, such as formic and acetic aldehydes, are the most sensitive ; they react a t once, and may be detected at concentrations of -zaYGa. Polyvalent alcohols and carbohydrates are also very sensitive, and react distinctly at concentra- tions of a&v; in this group the reaction is delayed for a longer or shorter time, according to the molecular weight, and begins to appear after about fifteen minutes.With the primary monovalent alcohols the limit of sensibility is %&. At higher concentrations colorations are obtained with substances such as acetone, lactic acid, citric acid, urine, and proteins. For quantitative determinations, separate portions of 0.25 gram of phenylhydrazine sulphonic acid are weighed out into a series of wide- mouthed bottles (200 grams) of equal dimensions. The substances to be tested, dissolved or suspended in 100 C.C. of water, are then added, and followed imme- diately by 15 C.C. of a 33 per cent. solut.ion of sodium hydroxide to each bottle.132 THE ANALYST. Each series is accompanied by a blank from which the substance, alcohol or alde- hyde, is omitted.The colorations produced are estimated comparatively in colori- meter tubes at the end of four, five, ten, twelve, or twenty hours. The blank should show only a yellow coloration, but it may absorb formaldehyde or other vapours from the air which would interfere with the test. The method, besides being applicable for the qualitative and quantitative estimation of many substances of this class, may also be used with considerable success for the estimation of the molecular weights or number of hexose groups in polysaccharides. As standards for this test, the disaccharides, maltose and lactose, are preferable to the simple hexoses which give colours with a bluish tone: The test may be made in two ways-either direct or after inversion.When tested direct, various multiple weights of the polysaccharide are compared with or a ~ \ c solutions of maltose until equivalent colours are produced; By the inversion method, a portion of the fully inverted polysaccharide is compared with different quantities of the original polysaccharide, and the ratio between the two solutions which match gives the ‘‘ inversion quotient.” By both of these methods it W ~ E found that soluble starch is equivalent to ordinary starch (which, however, had undergone the usual change in contact with the alkali hydroxide of the test solution). These starches are equivalent to three maltose groups, and by the inversion method they show a quotient of six. Erythrodextrin is equivalent to two maltose groups, and has an inversion quotient of four.Glycogen appears to be equivalent to at least two molecules of soluble starch. J. F. B. Estimation of Carbon Bisulphide in Benzene. J. Bay. (Comptes ILeitd.. 1908, 146, 132.)-The method of Liebermann and Seyewetz for the detection of traces of carbon bisulphide in benzene by means of phenylhydrazine may also be used for its quantitative estimation. The crystalline precipitate which phenyl- hydrazine gives with carbon bisulphide, CS,(C,H,.NH.NH,),, is very unstable in solution, but suficiently stable in the dry state for an estimation to be made. Precipitation is complete in two to three hours, and the precipitate is collected on double counterpoised filter-papers, washed with benzene till free from the excess of phenylhydrazine, and dried in VUCZLO.The results are slightly too high, owing to the difficulty of washing the precipitate completely. Thus, in typical test analyses,, in which 1963 and 12.630 per cent. of carbon bisnlphide were added to benzene, the amounts found were 1-269 and 12.640 per cent. respectively. C. A. Ill. Volumetric Estimation of Basic Dyestuffs by Means of Acid Dyestuffs. L. Pelet and Garuti. (Zeit. Fa& Ind., 1908,7,44-45.)-The methods recommended for the estimation of basic dyestuffs comprise: (1) Titration of methylene blue with Crystal Ponceau, Carmine in sodium carbonate solution, Pyramine orange (B. A. S.F.) and Cotton brown (B.A.S.F.). (2) Titration of Safranine with Helvetia blue, Sapthol yellow, S, and Acid violet, 6BN. (3) Titration of Fuchsin and New Fuchsin with Helvetia blue, Alkali blue, and Light green SF, bluish.(4) Titration of Auramine 0 and Auramine G with Congo red, Acid violet, 5BN, Oxamine red, Alkali blue, and Violet black. (6) Titration of Vesuvine with Violet black, Ocelline, Chromazone red, and water soluble Fast blue R. (5) Titration of Chrysoidine with Helvetia blue.THE ANALYST. 133 The methods all depend upon the precipitation of the basic dyestuE and deter- inination of the end-point by ‘‘ spotting ” on filter-paper. Solutions containing 1 to 3 per cent. of known pure dyestuffs have given very accurate results in this way, the precipitates formed being pseudo-salts of definite and constant composition. The end-point of the reaction may also be found by determining the electrical conduc- tivity of the solution, which is decreased by the addition of acid dyestuffs, and reaches the minimum when precipitation is complete.C. A. M. Test for Cholesterol. J. Lifschutz. (Ber. ricut. C‘hem. Gcs., 1908, 41, 252-255.)-The oxidation products of cholesterol, oxycholesterol ester and oxy- cholesterol, may be made to serve as tests for the presence of this alcohol. The oxidation is best carried out in acetic acid .solution by means of a peroxide of an organic acid radical. A few milligrams of cholesterol are dissolved in 2 to 3 C.C. of ,glacial acetic acid, and a little benzoyl peroxide added. The solution is boiled up once or twice, and 4 drops of strong sulphuric acid are added when it is cold. The mixture then assumes a violet-blue or green colour, according to the quantity of peroxide employed ; the first oxidation product giving the blue and the second the green coloration.The green coloration shows a characteristic absorption-band in the middle of the red portion of the spectrum between the lines C and d. Oxycholes- terol itself frequently occurs in the internal organs of animals. J . F. B. New Tests for Cholesterol and Oxyeholesterol. L. Golodetz. (Chem. hit., 19013, 32, 160.)-A new test for cholesterol is described which possesses the advantage that it may be applied to solid preparations of tissues under the micro- scope. The reagent consists of a mixture of 5 parts of concentrated sulphuric acid and 3 parts of formaldehyde solution; 1 or 2 drops of this reagent colour solid cholesterol a blackish-brown. It reacts only with free cholesterol, and may be used for the detection of the free alcohol in preparations of cholesterol esters.Another reaction, which, however, cannot be used as a micro-chemical test, consists in adding to a few drops of a solution of cholesterol in trichloracetic acid 1 drop of 30 per cent. formaldehyde solution, which produces an intense blue coloration. A test for oxycholesterol, the oxidation product of cholesterol, first isolated by Lifschiitz from wool fat, and also observed in bone and blood fats, consists in bringing the substance in contact with a few drops of liquefied trichloracetic acid. Oxycholesterol gives a, green solution showing a dark bend in the red portion of the spectrum. J. F. B. Analysis of Mixtures of Volatile Fatty Acids. A. Lasserre.(Ayzn. de L’Instit. Pastew, 1907, 21, 829 ; through Chm. Zeit. Rep., 1908, 32, 67.)-Acetic and formic acids may be separated from butyric and valeric acids by extracting the aqueous solution of the mixed acids with benzene, in which only the last-named acid dissolves, and from which they may be recovered by treatment with baryts solution. A. G. L. New Reactions for the Characterisation of Mercerised Cotton. d. Hubner, (Jown: SOC. Chem. Ind., 1908, 27, 105-lll.)-The author has standard-134 THE ANALYST. ised the well-known colour reactions between hydrated cellulose and solutions of iodine in presence of various salts, and has deduced therefrom a means by which mercerised cotton may be identified, and the strength of the sodium hydroxide which had been used in the mercerising process approximately determined.The method is based on the observations that mercerised cotton possesses a greater affinity for iodine than ordinary cotton, and that cotton mercerised under tension absorbs less iodine than cotton similarly mercerised without tension. Bleached cotton absorbs less iodine than unbleached cotton. I n carrying out the test, a series of samples of cotton fabric mercerised (under tension) with solutions of sodium hydroxide of various known concentrations must be prepared. If the sample to be tested be coloured, either the colour must be etripped before applying the reagent, or the test standards must be dyed to the same shade with the same dyestuff. ( a ) Iodine-Potassium Iodide Reagent.-The reagent contains 30 grams of iodine dissolved in 100 C.C.of a saturated aqueous solution of potassium iodide. If samples of cotton which have been mercerised with solutions of sodium hydroxide of different strengths be immersed in this reagent, and then washed with wclter, the black- brown coloration which they have acquired disappears more slowly the stronger the mercerising solution, up to R limit of 60" Tw. Unmercerised cotton loses its colour very rapidly. ( b ) Iodi?lc-Zi?zc Chloride Reagent.-The zinc chloride solution must be accurately prepared so as to contain 280 grams of zinc chloride in 300 C.C. of the solution. To 100 C.C. o€ this solution are added either 20, 10, or 5 drops of a solution of 1 gram of iodine and 20 grams of potassium iodide in 100 C.C. of water. The reagents containing 20 and 10 drops of iodine solution are suitable for determining the strength of the mercerising liquid a t concentrations corresponding to 10" to 30' Tw., whilst the reagent containing 5 drops is employed for the recognition of products mercerised with liquors of 30" to 60' Tw.In using the zinc chloride reagents, the colorations of the sample and the test standards are compared directly, washing, as in the case of the potassium iodide reagent, being unnecessary. If desired, the rate at which the colours fade on exposure to the air may also be determined. In applying the test to fabrics, the samples should first be wetted with water and pressed between filter-paper. In testing coloured samples, a piece may be immersed in the zinc chloride solution without iodine, to serve as a blank for comparison. Dark colours and colours dyed on tannin mordants should b3 stripped before testing (cf.ANALYST, 1908, 55). J. F. B. The test may be used in one of two forms : Starch, if present, must be completely removed. Determination of Phenols in Gas Liquors. F. W. Skirrow. (Journ. SOC. Chcm. Ind., 1908, 27, 58-62.)-For the estimation of phenols in gas liquors by the iodometric method, the liquors must first be freed from sulphides and cyanides. For this purpose 100 C.C. of the filtered gas liquor are treated with an excess of ammonium polysulphide, to convert the cyanides into thiocyanates. The mixture is allowed to stand, and is then diluted to 200 C.C. The sulphides are precipitated byTHE ANALYST. 135 the addition of lead carbonate, and the precipitate is filtered off.An excess of sodium hydroxide (25 C.C. of a 50 per cent. solution) is then added to 100 C.C. of the filtrate, and the solution is evaporated until the salts begin to crystallise out. The residue is washed into a distillation flask of 1 litre capacity and diluted to about 150 c.c., and when cold is acidified with sulphuric acid. The liquid is distilled until the salts begin to crystallise out-thus (‘ distillate No. 1 ” is obtained ; 100 C.C. of water are then added to the residue in the flask, and ( ( distillate No. 2 ” is collected in a separate receiver. The whole of the phenol is contained in the three distillates. Each of these is neutralised separately with calcium carbonate and a little lead carbonate, and redistilled in the same order as they were first collected. The final distillates are mixed and diluted to 500 C.C.I n titrating the phenols, the quantity of sodium hydroxide present is of some importance. I t is best to perform a preliminary titration in presence of a, large excess of sodium hydroxide, and to use finally the proportions of 4 molecules of sodium hydroxide to 1 molecule of phenol found at first. The solution is made alkaline with this quantity of sodium hydroxide ; it is then warmed to 60’ C., and treated with excess of TG iodine solution. The flask is immediately closed, and the contents are allowed to cool; they are then acidified, and the excess of iodine is titrated back with :v thiosulphate. One molecule of phenol consumes 6 atoms of iodine.The author has ascertained that the presence of sulphites, thiosulphates, and thiocyanates has no influence on the results. Since cresols are present in the gas liquor as well a8 phenol, the results are about 5 per cent. too law on this account. The liquid after titration has a rose-pink coloration, owing to the presence of tri-iodophenol. This coloration map be made the basis of a colorimetric method for the estimation of small quantities of phenol which cannot be titrated with accuracy. J . F. B. I n a similar manner a, third distillate is obtained. Estimation of Picric Acid. M. Busch and G. Blume. (Zeit. a y c w . Chena., 1908, 31, 354-355.)-The method proposed is based on the insolubility of ‘( nitron ” picrate, a solution containing 1 part of picric acid in 250,000 parts of water giving a distinct precipitate when treated with nitron ” acetate solution (cf.ANALYST, 1907, 32, 349). The estimation is carried out as follows : The picrate solution, containing about 0.15 gram of the acid in 150 C.C. of water, is acidified with 2 C.C. of dilute sulphuric acid, and heated just to boiling. Ten C.C. of icnitron” acetate solution (10 per cent. of ‘( nitron” in 5 per cent. acetic acid) are added slowly, and the mixture is allowed to cool to the ordinary temperature. The precipitate is collected on a weighed filter, washed with from 50 to 100 C.C. of cold water, dried for one hour at a temperature of l l O o C., and weighed. The weight of the ‘( nitron ” picrate- C,,H,GN,.C,H3N307-multiplied by the factor 0.42529, gives the weight of the picric acid. The method is applicable to the estimation of picric acid in mixtures of various high nitrated phenols, pyridin picrate, quinolin picrate, etc., and the above- mentioned limits as to dilution may be varied considerably without influencing the accuracy of the results. The solution, however, must not contain bromides, iodides, chlorates, perchlorates, nitrates, nitrites, or chromates. w. P. s.136 THE ANALYST. Examination of Salicylic Aldehyde for Use in Testing for Fuse1 Oil. H. Kreis. (Cliem. Zcit., 1908, 32, 149.)-The author warns against the use of impure salicylic aldehyde, which may give a red colour even with alcohol free from fusel oil. The aldehyde may be tested by adding 0.5 C.C. of its 1 per cent. solution and 10 C.C. of concentrated sulphuric acid to 5 C.C. of 95 per cent. alcohol known to be free from fusel oil. After cooling, the solution should be yellow in colour, resem- bling picric acid, but not reddish. Or 3 drops of the aldehyde are mixed with 10 drops of sulphuric acid. If the aldehyde is pure, a light orange-red colour will be obtained, impure samples giving brownish-red colours. On adding 5 C.C. of 95 per cent. alcohol to the liquid, it will become colourless if the aldehyde was pure, whilst in the contrary case the solution will turn red (cf. ANALYST, 1903, 28, 293). -1. G. L.

ISSN:0003-2654    

DOI:10.1039/AN9083300130

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

136 THE ANALYST. INORGANIC ANALYSIS. The Action of Arsenic Hydride (Arsine) on Solutions of Halogens, Halogen Acids, and other Oxidising Substances. H. Reckleben and G. Lockemann. (Zeit. anal. Chcm., 1908, 47, 105-125.)-The following is a summary of the results of experiments on the action of oxidising substances on arsenic hydride. Aqueous solutions of iodine, bromine, and chlorine quantitatively absorb and oxidise arsenic hydride, with the formation of arsenic acid, according to the equation : H,As + 41, + 4H,O = H,AsO, + 8HI. Solutions of hypochlorites act in a, similar way, but the absorption is not so good. Hypobromites also absorb the gas slowly. Iodic acid, iodates, bromic acid, and bromates oxidise arsenic hydride to arsenic acid, especially in the presence of a catalytic agent, such as a trace of silver nitrate.Chloric acid is slower in its action, and the product of the reaction is arsenious acid, whilst neutral chlorstes are entirely without action. Periodates oxidise arsenic hydride, but perchlorates, even in acid solution and in the presence of a catalytic agent, act but slowly. Neutral and acid solutions of permanganates, as well as alkaline solutions of ferricyanides and acid solutions of bichromates, absorb arsenic hydride completely, whilst concentrated nitric acid, sulphuric acid, and solutions of persulphates, chromates, bichromates, and neutral ferricyanides, absorb it but slowly and incompletely. Hydrogen peroxide acts very slowly on the gas, arsenic being liberated at first, and afterwards oxidised to arsenious and arsenic acids.w. P. s. The Analysis of '' Golden " Antimony Sulphide. F. Jacobsohn. (I?zdin- Rubber Jozmz.., 1908, 35, 77-78.)--For the estimation of the antimony, 0.2 gram of the sample extracted with carbon bisulphide is oxidised with fuming nitric acid, and the residue heated with ammonium chloride, the loss in weight representing the amount of antimony volatilised in the form of chloride, whilst the residue consists of other mineral matter, such as silica and calcium sulphate. Any calcium present in the form of antimonate or sulphantimonate is converted into calcium chloride when heated with ammonium chloride, so that in such s case there may be a slight error from this cause. Or mineral impurities may be estimated by evaporating theTHE ANALYST.137 original sample with hydrochloric acid, oxidising the residue with nitric acid, taking it up with hydrochloric acid and a little tartaric acid, separating the silica, precipitating the antimony as sulphide, and estimating the substances in the filtrate. In estimating sulphur combined with antimony, the sample previously extracted with carbon bisulphide is heated with strong hydrochloric acid, the hydrogen sulphide evolved collected in ammoniacal silver solution, and the precipitated silver sulphide ultimately weighed as metallic silver. The following results were obtained in the analysis of different qualities of " golden sulphide " : Moisture (loss at 60" C.) ... Free sulphur . . . ... Total sulphur . . . ... Silica ... ... ... Calcium sulphate . . . Sulphur combined with calcium ...... Antimony ... ... ... antimony ... ... ... ... Sulphur coiiibined with 1 Per Cent. 1.03 8.38 33-76 0.23 11.48 2.70 50.55 2.2 -40 2 . Per Cent. 1.15 9.36 31.99 0.23 10-60 2.43 51.29 20 16 3. Per Cent. 0.77 8-00 33.62 10.82 - 2.54 53.74 22-88 4. Per Cent. 0.60 8.38 32.98 11.78 2-77 53.30 21.62 __._ C . A. If. The Determination of' Small Quantities of Bismuth. H. W. Rowell. (Joum. SOC. Chem. I d . , 1908, 27, 102-104.)-The method depends on the colour pro- duced by potassium iodide in solutions of bismuth in dilute sulphuric acid. A nearly pure bismuth oxychloride is obtained by a preliminary treatment as follows : 10 grams of a sample of had, base bullion, etc., are dissolved in 20 C.C. of nitric acid and 80 C.C. of water ; tin and antimony are precipitated by boiling, silver is removed by means of st very small excess of dilute sodium chloride solution, and lead is precipitated by adding to the boiling solution 60 C.C.of boiling dilute sulphuric acid (1 : ZO), drop by drop, and then adding another 30 C.C. of dilute sulphuric acid (1 : 3), cooling, and allowing to stand for an hour. To the filtered liquid are' added 5 C.C. of hydrochloric acid and a slight excess of ammonia, then dilute hydrochloric acid until the liquid is just acid to methyl orange, when it is boiled for a minute, and allowed to stand for an hour in a warm place. The precipitate is filtered off, washed twice, and the filtrate tested for more bismuth. Paper and precipitate are boiled with 10 C.C. of sulphuric acid (1 : 3) and 30 C.C.of water, cooled, filtered, and washed with dilute sulphuric acid. The filtrate, or a fraction containing not more than 2 or 3 mgms. of bismuth, is placed in a Nessler cylinder, together with 5 C.C. of potassium iodide solution (20 per cent.), 5 C.C. of sulphuric acid (1 : 3), and 10 drops of sulphurous acid solution. The resulting colour is compared with that obtained with similar quantities of reagents from known amounts of a standard solution containing 0.1 gram of bismuth dissolved in 10 C.C. of nitric acid, and made up to a litre with water. For138 THE ANALYST. coppe?', 10 grams are dissolved in nitric acid, the solution is neutralised with saturated sodium carbonate solution, of which 1 C.C. is then added in excess; the whole is boiled for five minutes, and the precipitate obtained is filtered off and converted into oxychloride as above.Ores, mattes, etc., are dissolved in aqua regia and evaporated with sulphuric acid, after which they are treated as above. Samples containing large quantities of arsenic, aiztimony, or tin, are best fused with sodium carbonate and sulphur as a preliminary operation. The method will detect 0.00001 gram of bismuth; duplicates agree well with each other. A . G. L. Estimation of Chlorates, Bromates, Iodates, and Periodates by Means of Formaldehyde, Silver Nitrate, and Potassium Persulphate. H. Brunner and R. Mellet. (Jozm~. Prakt. Clbenz., 1908, 77,33 ; through Clienz. Zeit. l t e p . , 1908, 32, 53.)-A weighed quantity of about 0.1 gram of the salt is dissolved in 20 C.C.of water, from 10 to 20 C.C. of -:o silver nitrate solution, 5 C.C. of nitric acid (specific gravity 1.4), 1 gram of potassium persulphate, and 1 C.C. of formaldehyde solution are added, and the mixture is heated. I n the case of iodates and periodates 2 grams of the persulphate and 5 C.C. of formaldehyde are required. For the estima- tion of chlorine it is sufficient to heat the mixture on the water-bath; but with bromates, iodates, and periodates it is necessary to heat over a flame until tht: aldehyde has been oxidised completely, as is ascertained by the disappearance of the odour. After cooling, the mixture is treated with a few cubic centimetres of iron- alum solution, and the excess of silver is titrated with potassium thiocyanate solution. The method is stated to be trustworthy.w. P. s. Test for Copper. E. Knecht. ( J h . . t 7 m t . Clrelu. Ges., 1 9 0 ~ ~ 41, tW499.)--Tllc author describes a delicate test for copper, which consists in precipitating the metal by means of titanium sesquisulphate. If 1 C.C. of a 10 per cent. solution of copper sulphate be added to 1 to 2 litres of water, and if 5 C.C. of the commercial solution of titanium sesquisulphate be then added and stirred up, metallic copper will begin to separate in a few minutes. The precipitate shows the ordinary colour of copper by reflected light, but appears blue by transmitted light. The metal is so finely divided that only a very small portion can be removed by filtration. The reaction is still visible at dilutions corresponding to 1 part of copper per million, but the greater the dilution the slower is the formation of the precipitate.J. k'. 13. Electrolytic Estimation of Minute Quantities of Copper. E. E. Free. (Joz~m. Phys. C.'hen~., 1'308, 12, 4&29.)-A direct electrolytic estimation of quantities of copper less than 1 mgni. may be made by the use of an electrode consisting of platinum wire (weighing about 0.3 gram) bent into a spiral, with a free end, which is wrapped four or five times round a hook of heavy platinum wire. The spiral is suspended in the bath, and the electrolysis made either in nitric or sulphuric acid solution by means of a low current (about 1.8 volts and 0.01 amphe). The electrode is afterwards washed with water, alcohol and ether, dried over sulphuric acid a i dTHE ANALYST.139 weighed, the copper dissolved off it by means of nitric acid, and the electrode washed, dried and weighed as before, the difference in the two weighings giving the amount of copper. c. A. i\r. Electrolytic Separation of Silver and Copper. H. W. Gillett. ( J o u ~ / t . Phy. Chem., 1908, 12, 26-27.)-Good deposits of silver may be obtained from an ammoniacal tartrate solution by means of a current of 0-45 a,mp./dmz at 7OoC., provided either the anode or cathode be meanwhile rapidly rotated. Copper in the filtrate inay be estimated by precipitation as sulphide, dissolving the precipitate in nitric acid containing a little sulphuric acid, filtering off the sulphur, and electrolysing the filtrate by means of a current of density 2 to 4 anip,,dm2, with a rapidly rotating anode.C. A. M. Estimation of Small Quantities of Fluorine. G. Steiger. (Joiim. Anzer. Chem. Soc., 1908, 30, 311)-225.)--The method is based on the well-known fact that fluorine (as hydrofluoric acid) has a bleachiug effect on the yellow colour produced by hydrogen peroxide with a titanous solution, and the extent of this bleaching is found colorirnetrically. Fairly accurate results may in this way be obtained if the fluorine content of the sample does not exceed 2 per cent. For the examination of rock mixtures containing only a few tenths per cent. of fluorine, 2 grams of the finely ground sample are fused with four or five times its weight of a mixture of sodium and potassium carbonates. I n the case of subsilicic rocks, it may be necessary to add silica, 50 per cent.of which should be present. The alumina, and most of the silica are separated from the aqueous extract of the fusion by adding ammonium carbonate, keeping the liquid at 100” C. for fifteen to twenty minutes, and filtering after standing at least one hour in the cold. The filtrate is evaporated to small bulk, and again filtered to obtain a perfectly clear solution, which will by this time be free from alumina, and should contain not more than 25 mgms. of silica, a quantity insufficient to interfere with the test. The liquid is nearly neutralised with sulphuric acid, and well shaken to get rid of the greater part of the carbon dioxide. IZxcess of acid is now added, and 20 C.C. of a standard titanium sulphate solution, foliowed by 2 or 3 C.C.of hydrogen peroxide, and the liquid diluted to 100 C.C. The amount of fluorine in the solution to be examined in this method should not exceed 0.003 gram. LOSS of fluorine occurs if the liquid be shaken after acidification. The colour of the solution is compared with a standard containing similar amounts of titanium and hydrogen peroxide in 100 c.c., the author employing a specially devised form of colorirneter (see p. 147). The extent of the bleaching action is not directly proportional to the amount of fluorine present, which must be found by reference to a curve worked out by the author. Large quantities of sodium salts and small quantities of silica have little effect on the reaction, but alumina must be entirely absent. Phosphoric acid exerts a bleaching action similar to that of hydrofluoric acid, and more than traces of the former should not be present.The presence of iron prevents the bleaching of the yellow colour, but this element is almost completely removed by the imethod described. The standard titanium solution used hy the author was prepared from potassium-titanium fluoride, an140 THE ANALYST. aqueous solution of which was evaporated several times, until " fuming " took place, with an excess of sulphuric acid to ensure the removal of all fluorine. The titanium in the solution obtained by dissolving the residue in water was determined by precipitating a measured amount with ammonia, weighing the precipitate as Ti0 ?, and the solution diluted so as to contain 0*0001 gram TiO, per c.c., 3 per cent.of sulphuric acid being also added. A. R. T. Estimation of Ash in Graphite. S. S. Sadtler. ( JO~LYIZ. J'ruulJiu Iust., 1907, 164, 901 ; through Chenz. h i t . E c p , 1908, 32, 94.)-The author uses a crucible which has a diameter of 25 mm. at the bottom and only 15 mm. at the top, its height being 40 inm. About 0.3 gram of the substance is heated in this crucible by a blow- pipe flame in a current of oxygen. If the graphite be burnt alone, the ash may fuse, and its quantitative examination be thereby hindered. I n order to avoid this, the graphite is mixed in the crucible with SO mgms. of thoroughly calcined magnesia ; i i i the case of coarse graphite9 only 5 mgms. of magnesia are used. Care must be taken that the substance is not blown away by the stream of oxygen, and it is best t o accumulate the fine powder as far as possible in one spot in the crucible.The oxygen tube is gradually advanced deeper into the crucible until the mass softens slightly and coheres. The heat is then increased to a full white glow, and the inass is observed through blue glass until the glow dies out. J. F. B. Separation of Iron from Indium. F. C. Mathers. ( v J o / o - ~ ~ . - 1 7 1 ~ ~ 1 ' . L ' I L ~ I I L . ,SO(:., 1'308, 30, 209-211.)-The author has been unable to obtain a satisfactory quantitative separation of these metals by any of the usual methods, some of which gave an indium free from iron, but involved a serious loss of indium. The following method has been devised, based on the fact that iron is completely precipitated by nitroso-P-naphthol, the indium remaining in solution.The main portion of the iron lilust first be removed by some other procedure, however, since the nitroso-p-naphthol compound with this element is very bulky. The best plan is to precipitate the indium electrolytically from a solution of the two sulphates strongly acidified with sulphuric acid. The indium thus prepared contains only small amounts of iron ; and from the solution of its chloride or sulphate, neutralised by ainmonia, the iron is precipitated by adding to the hot or cold liquid an equal volume of 50 per cent. acetic acid, and then nitroso.9-naphthol dissolved in 50 per cent. acetic acid. The amount of iron present should not exceed 0.05 gram, 5 granis of the reagent being suflicient for this quantity.The solution, after standing several hours, is filtered cold, and the precipitate washed first with 50 per cent. acetic acid, and finally with water. The filtrate contains only the merest trace of iron ; and although indium can be detected spectroscopically in the precipitate, and cannot be completely removed by a second precipitation? it is quite small in actual amount. I n a typical experiment, where 0.3061 gram of indium oxide and 0.0262 gram of ferric oxide were employed, with 2; grams of nitroso-P-naphthol, the separated indium oxide contained less than 0.1 mgm. of ferric oxide, while the latter showed 0.0024 gram and 0*0011 grain respectively of indium oxide after the first and second precipitations. -4, Hi. T.THE ANALYST.. 141 Volumetric Estimation of Lead as Lead Sulphide.H. Koch. (Chcnz. Zeit., 1908, 32, 124-125.)-Lead sulphate is obtained a8 usual, and is then dissolved from the filter into a 400 to 500 C.C. bottle by means of 150 C.C. of boiling ammonium acetate solution and a little water, The solution is allowed to cool, 5 C.C. of acetic acid and 60 C.C. of carbon tetrachloride are added, and the lead titrated with standard sodium sulphide solution. The end-point is readily seen, as carbon tetra- chloride, when shaken with an aqueous liquid holding lead (or copper) sulphide in suspension, absorbs the whole of the sulphide, leaving the aqueous solution clear. The sodium sulphide solution is daily standardized against a copper or silver solution. I t should be kept in an atmosphere of coal-gas. The quantity of lead titrated should not exceed 0.2 grain of metal. I€ more than this amount is present, the author makes the ammonium acetate solution, containing 5 C.C.of acetic acid, up to 300 c.c., in a 500 C.C. flask provided with a rough mark at 300 C.C. ; 5 C.C. are t'hen removed and titrated as above; an amount of sodium sulphide, somewhat less than that calculated to be necessary for complete precipitation, is then added to the flask, the contents are made up to 500 c.c., mixed, and 100 C.C. of the turbid liquid are titrated in the bottle in which the 5 C.C. were titrated. The carbon tetrachloride is readily cleaned with nitric acid, and may be used over again. A . G. L. Sodium Hyposulphite in Volumetric Analysis - I. H. Bollenbach. (Chenz. Zczt., 1908, 32, 146-148.)-The author obtained good results by the titration of ferric iron in sulphuric acid solution with solutions of sodium hyposulphite, containing 30 to 2.5 grams of the salt per litre, and made alkaline with sodium hydroxide. Both the bottle and burette containing the solution should be filled with an inert gas, but the flask, in which the titration is effected, may be left open to the air.The solution t o be titrated should not be at a temperature of more then 30' C. If hydrochloric acid is present, sufficient dilute sulphuric acid must be added to destroy the yellow colour of ferric chloride. Small quantities of nitric acid do not interfere, neither do organic compounds (o.g., tartaric acid, glycerine), zinc, man- ganese, nickel, cobalt, aluminium, or chromium.Metals of the second group, which are precipitated by hyposulphite, must be absent. The actual titration is carried out after adding to the ferric solution a little sulphuric acid and a little potassiuiu thiocyanate. As soon as the red colour begins to fade a drop of indigo solution is added, and the titration continued until the blue colour is discharged. The reaction apparently proceeds according to the equation : Na,SaO, + Fe,(SO4):< + H,SO, = 2FeS0, + 2NaHS04 + 2S0,. A. G. L. The Volumetric Estimation of Sodium Monosulphide. E. Podreschet- nikoff. ( Z e d . Farben In& 1907, 6, 388.)-Sodium monosulphide is decomposed by water into sodium hydroxide and sodium hydrosulphide ; but since the commercial salt usually contains free sodium hydroxide, the volumetric estimation of the alkali liberated in the reaction with water is not reliable as a measure of the original sulphide.To obviate this drawback the author first titrates the solution of the142 THE ANALYST. sodium monosulphide in recently boiled water with ;& sulphuric acid, with phenol- phthalein as indicator, to obtain the amount of free alkali in the salt, together with that produced in the reaction with water. An excees of formaldehyde solution is then added, which decomposes the hydrosulphide according to the equation- NaHS + H.COH + H,O = H,.COH.HS + NaOH ; and on now continuing the titration until the liquid again becomes colourless, the second reading gives the amount of sodium hydroxide liberated in the interaction of the formaldehyde and sodium hydrosulphide.One molecule of sodium monosulphide thus yields two molecules of sodium hydroxide. The results of this method agree well with those obtained by means of the zinc and iodide methods. C. ,4. M. Estimation of the Acidity of Soils. H. Siichting. (Zeit. nngezo. Chem., 1908, 21, 151-153.)-For the determination of the acidity of peaty soils, the author describes a method in which the soil is treated with calcium carbonate, and the quantity of the latter acted on ascertained subsequently. From 10 to 30 grams of the soil are placed in a flask, together with some water. The flask ie closed with ZL cork, through which pass inlet and outlet tubes and the stem of a tapped funnel. A weighed amount of calcium carbonate (about 0.4 gram) is now added to the flask, and a current of hydrogen is passed through it for two hours.The outlet tube of the flask is then attached to an absorption vessel containing a measured volume of standard sodium hydroxide solution, 50 C.C. of 20 per cent. hydrochloric acid are added to the flask, and the current of hydrogen is allowed to pass through the apparatus for one hour. The carbon dioxide liberated from the residue of calcium carbonate which has not been decomposed by the acidity of the soil is thus absorbed by the sodium hydroxide, and its quantity ascertained by titration in the usual way. The difference between the quantity so found and that added originally as calcium carbonate is a measure of the acids existing in the soil. w. P. s. Estimation of Carbon in Soils. D. Chouchak.(BzdZ. SOC. C l z i ? ~ ~ , 1908, [iv.] 3, 75-80.)-1n the method described the carbon is estimated by combustion with potassium bichromate and lead chromate, the carbon dioxide formed being collected and absorbed in a receiver containing barium hydroxide solution. This receiver is provided with mercury traps, and a sulphuric acid tube is interposed between the end of the combustion tube and the receiver. The barium hydroxide solution employed is of known strength, and, when the combustion is finished, the excess of barium hydroxide is titrated back after allowing the barium carbonate to settle. Soils containing but little calcium carbonate are treated directly, the carbon present as carbonate being estimated separately and subtracted from the total quantity found.Calcareous soils are moistened with dilute sulphuric acid, and heated on the water-bath to remove carbon dioxide; the residue is then used for the estimation. w. P. s.THE ANALYST. 143 Volumetric Estimation of Tin by Potassium Bichromate. H. Reynolds. (CkenL. fleu~s, 1908, 97, 13-15.)-The author has studied the conditions necessary for accuracy in following Streng’s method (Sutton’s ‘( Volumetric Analysis,” ninth edition, p. 345), and has found that oxidation is best prevented by titrating in an atmosphere of carbon dioxide, while the end-point of the titration may be more accurately observed by means of a special indicator prepared in the following way : A quantity of azobenzene is heated with concentrated sulphuric acid until a violent reaction sets in, when the liquid is iminediately poured into a large volume of water.A deep-red solution is thus obtained, containing possibly an oxy-azobenzene sulphonic acid. Stannous chloride reduces this compound to a colourless body, but it is restored to its original colour by potassium dichromate, and thus the liquid forms an efficient indicator for use in Streng’s method. Several C.C. of the indicator must be added to ensure that the red colour will completely mask the green of the chromium solution. Ferrous salts do not affect the indicator, so that stannous chloride may be determined in the presence of iron compounds. The method as modified by the author is carried out as follows : Twenty C.C. of strong hydrochloric acid are intro- duced into an Erlenmeyer flask of 200 C.C.capacity. This flask is fitted with a cork having a long and a short tube passing through it. The long tube, through which the carbon dioxide is conducted, is arranged so that the gas is delivered just above the surface of the liquid, The short tube is about 6 mm. wide at the top, and 2 mm. wide at its bottom end, which should be cut off slantwise. This tube is provided with a side-opening just below the cork, to allow of the passage of the carbon dioxide during the titration. The gas used is purified by passing (1) through titanous sulphate to remove oxygen, and (2) through sulphuric acid to free it from titanous sulphate. The current of carbon dioxide having been started, the acid in the flask is heated nearly to boiling, and then allowed to cool. A platinum gauze basket (1 cm.square) containing 0.6 to 1.0 gram of the granulated metal is then introduced, and when no more hydrogen is evolved the acid is heated nearly to boiling to drive off any hydrogen in the solution, the liquid cooled, and standard potassium dichromate solution (1 C.C. = 0.01 gram Sn) run in to within about 1 C.C. of the correct quantity. The azobenzene indicator is next added through the short tube. During the whole of these operations the current of carbon dioxide should be uninterrupted. The flask is next opened, the platinum basket removed, and the titration completed by running the dichromate solution directly into the flask. The test-analyses in the cases of tin, ferro-tin, and Britannia metal are satisfactory, but the method is not applicable to the assay of manganese tin, pewter, and phosphor-tin. A.R. T. The Separation of Tungstic Acid from Phosphoric Acid. G. v. Knorre. (Zeit. aual. Chem., 1908, 47, 37-57.)--An approximate separation of phosphoric and tungstic acids may be effected by diluting the solution containing the phosphate and tungstate to 300 or 400 c.c., adding 3 C.C. of hydrochloric acid (specific gravity 1-12), and precipitating the tungstic acid from the boiling liquid by means of benzidine hydrochloride (cf. ANALYST, 1907, 32, 131). When completely cold the liquid is filtered, and the precipitate slightly washed with dilute benzidine hydrochlorideTHE ANALYST. 144 solution, boiled with about 200 C.C. of water to remove any remaining benzidine phosphate, again filtered off when cold, washed thoroughly with dilute benzidine hydrochloride solution, ignited, and weighed a s tungsten trioxide.The presence of phosphoric acid, even in traces, imparts a bluish-green colour to the residue. A quantitative precipitation of tungstic acid may be effected by means of tolidine hydrochloride. The reagent is prepared by suspending 20 grams OE commercial o-tolidine in water, adding 28 C.C. of hydrochloric acid (specific gravity 1-12>, heating the mixture until solution is complete, and diluting the liquid to a litre. Ten C.C. of this solution precipitate approximately 0.22 gram of tungsten trioxide. The solution, containing, e g . , about 0.5 gram of sodium tungstate and about 0.015 grain of phosphorus pentoxide (in the form of disodium phosphate), is diluted to 300 or 400 c.c., boiled with about 3 C.C.of hgdrochloric acid (specific gravity 1-12>, and treated while hot with excess (50 c.c.) of the benzidine hydrochloride solution. When completely cold the precipitate is filtered off, washed with dilute benzidine hydrochloride solution (1 part of the strong solution with 5 to 10 parts of water), and ignited in a platinum crucible. Any traces of phosphoric acid left in the residue of tungsten trioside are separated by fusing the mass with soda, dissolving it in water, and reprecipitating the tungsten as above described. Tolidine phosphate is much more soluble than benzidine phosphate, whilst tolidine tungstate may be filtered off readily without the necessity of the addition of 10 C.C. of T6 sulphuric acid to the precipitating solution, which was found essential for the good filtration of benzidine tungsta t e.c. A. &I. The Estimation of Minute Quantities of Zinc. G. Bertrand and M. Javillier. (BzdL. SOC. Chim., 1908 [iv.], 3, 114-117.)-The qualitative method based on the formation of calcium zincate (ANALYST, 1907, 32, 133) may be used for the estimation of traces of zinc in the presence of the different substances which it may accompany. The mixture is dissolved in agicn Y-egia, the solution evaporated to dryness, the residue taken up with dilute hydrochloric acid, and the solution treated with hydrogen sulphide, and filtered. The filtrate is boiled and poured into a solu- tion of ammonia (20 to 25 per cent. strength), and the mixture treated with hydrogen peroxide to oxidise any manganese, and filtered.The precipitate is dissolved in con- centrated hydrochloric acid, the solution again treated with ammonia and hydrogen peroxide, and the new precipitate once more dissolved and reprecipitated. The united ammoniacal filtrates, which should contain 4 to 5 per cent. of free ammonia, are boiled, and treated little by little with sufficient milk of lime to liberate all the combined ammonia and precipitate the whole of the zinc, the boiling being continued SO long as the steam is alkaline to turmeric paper, The precipitate of calcium zincate is then washed with water saturated with lime, and dissolved in hydrochloric acid, the solution evaporated to dryness on the water-bath, the residue dissolved in a few C.C. of a 5 per cent. solution of sodium or ammonium acetate acidified with acetic acid, and the solution treated with hydrogen sulphide. After standing for twenty-four hours the zinc sulphide is collected, washed with hydrogen sulphide water acidified with acetic acid, and dissolved in 5 per cent. sulphuric acid, the solu- tion evaporated to dryness in a platinum crucible on the water-bath, and the residueTHE ANALYST. 145 heated over a flame to expel the excess of acid. The weight multiplied by 0.4052 gives the amount of zinc in the original substance. The test analyses quoted of mixtures containing 0.01 gram of zinc in the presence of 0.5 gram of metals of the ordinary groups or of acid radicals agree closely with the theoretical amounts. Nickel or cobalt, however, would he precipitated with the zinc, and would require separation by the ordinary method. C. A. M. Rapid Electrolytic Separation of Zinc and Nickel. A. Fischer. (Chem. &it., 1908, 32, 185-186.)- Nickel may be electrolytically separated from zinc by using an electrolyte containing 5 grams ammonium sulphate, 1 to 3 grams sodium sulphite, and 30 C.C. of ammonia (0*91), for 0.15 gram each of nickel and zinc, dis- solved in a total volume of 250 to 300 c . ~ . The current used is 1.0 ampere, graduaIly lowered to 0.1 ampere ; it is controlled by keeping the drop of potential between the cathode and a standard auxiliary electrode constant a t 1.35 volts. (Cj. Zeifs. Elektrochem., 1907, 13, 469.) As electrodes concentric cylinders of gauze are used. Deposition is complete in twenty minutes. A. G. L. The temperature is kept at 90-92" C.

ISSN:0003-2654    

DOI:10.1039/AN9083300136

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

THE ANALYST. 145 APPARATUS, ETC. A Modification of the Calorimetric Bomb. E. Rengade. (BiiZZ SOC. Chz'??~., 1908 [iv.], 3, 188-190.)-The modification of Mahler's calorimetric boinb shown in the figure was designed for determinations in which the reaction is made to take place in a liquid medium. For the study of the action of water on alkali metals and similar reactions the electric- sparking wires are dispensed with, a movable steel rod termin- ating in a flat disc, d, being used for breaking the glass vessel, a, which contains the substance, and is attached by means of fine wire to a steel support at the bottom of the bomb. The latter has a capacity of about 220 c.c., and is filled with water, with the exception of a space of about 40 c.c., where the gaseous products of the reaction may lodge, B vacuum being produced by attaching a pump to the tube, r , which is opened by turning.The bomb is suspended in the calorimeter by meaus of a cord attached to the wooden rod, t, which is fixed to the end of the crushing rod, whilst a glass rod, b, is placed inside at an anglo of 4 5 O , so that when a rapid rotatory move. ment is applied, first to the right and then to the left, the liquid within the bomb is thoroughly agitated. The tempera- ture reaches its maximum in four to six minutes after the beginning of the reaction. The gases niay subsequently be withdrawn through the tube, T , measured and analysed, a correction being made for the amount dissolved by the liquid. Super- saturation is prevented by vigorous shaking at the end of the reaction, and a correction is usually necessary for the heat of solution of the gas.The calorimetric values146 THE ANALYST. found may be brought to constant pressure by deducting from them the amount of heat that the gases would absorb if liberated under atmospheric preesure. C. A. M. Rapid Estimation of Carbon and Hydrogen in Organic Substances. P. Breteau and H. Leroux. (Bzdl. SOC. Chim., 1908 [iv.], 3, 15-22.)--The apparatiis here shown embodies the different improvements which have been suggested in the electrical method of combustion (ANALYST, 1907, 32, 238). I t consists of a tube, XN, of porcelain or fused quartz, 13 cm. in length and 6 mm. in external diameter, round which is wrapped platinum wire (containing 20 per cent. of iridium), 0.3 mm.in diameter and 30 cm. in length. The first spiral is connected at I wit11 a platinum wire fused into the tube, whilst the other end is attached to the platinuin wire, OP, passing through the rubber cork, C. The porcelain tube, through which no current of gas is intended to pass, is fixed to a tube, DE, of nickel or (preferably) silver, 4.5 em, long and 0.6 mm. in diameter, the other end of which passes through the rubber cork, C, which fits into's combustion tube, XB, of Jena glass, 35 cm. long and 16 mm. in internal diameter. The substance under examination is placed in the porcelain boat, ,,,,,,, ,,,,,, ,,, ,,,,,,, %. ,,, ,, .,,,", ,,, ,,, I I ,I I - .- %, and introduced into the combustion tube by means of the tube, Its, devised by I>ennstedt for the introduction of a double current of dry oxygen through the semi- capillary tube, SV, and the branch, V. The body of this tube is 12 cm.long and 14 mm. in diameter, and its capillary portion, which is 25 cm. long and 6 mm. in external diameter, passes through the rubber cork, 13, closing the other end or' the cornbustion tube. The inner current of oxygen is passed through the apparatus a t the rate of about a bubble in two seconds, whilst the outer current is regulated to give a considerable excess of gas (about 1 C.C. per second). The platinum spiral is brought to a dull red heat by means of the electric current, and the tube beneath the substance is gently heated at intervals by means of a Bunsen burner so as to briDg about intermittent volatilisation or decomposition.In the case of very volatile sub- stances, such a6 ether, the semi-capillary tube is replaced by a closed tube, and only the exterior current of oxygen admitted. External heating is also dispensed with, the heat of the glowing platinum being sufficient to effect the slow volatilisation of the liquid. The duration of a combustion ranges from fifteen to forty minutes for a, quantity of 0.15 gram, according to the nature of the substance, the end being shown by the disappearance of all residual carbon. Experimental results quoted show that the method is extremely accurate. C. A. M.THE ANALYST. 147 New Form of Colorirneter. G. Steiger. (Jouriz. Jwzer. Chem. SOC., 1908, 30, 215-219.)-1n this instrument the ratio of the thickness of the liquids looked through is measured.The colorirneter consists essentially of a box made with two parallel grooves in its base, in which two graduated glass solution-cells can be moved to and fro, the observer looking through one end of the cells. A hole in the under side of the box allows of the admission of light reflected from a mirror below. Into each cell a glass tube is lowered, carrying at its base a small mirror fixed at an angle of 4 5 O . The lower edges of the mirrors touch the bottoms of the cells when in use. The light coming up through the bottom of the cell, and that reflected through the end of it, will go through the same thickness of liquid, and this distance-the distance to be measured-is represented by the length from the end of the cell to a point obtained by producing the line formed by the angle of the small mirror attached to the glass tube, to the base of the cell. A small correction is necessary, owing to the fact that the light must traverse the glass of the mirror before striking the reflecting surface, and the same on leaving. The distance to be thus deducted is represented by twice the hypotenuse of an isosceles right-angled triangle, the equal sides being those of the thickness of the mirror glass. The strengths of the solutions being then inversely proportional to the thickness of the liquid looked through, if R = the reading of the cell containing the standard with concentration C, and T = the reading of the A. R. T. RC unknown solution with concentration c, tben c = ----.

ISSN:0003-2654    

DOI:10.1039/AN9083300145

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

THE ANALYST. 147 REPORT OF THE COMMITTEE APPOINTED BY THE TREASURY TO INQUIRE GENERALLY INTO THE WORK NOW PERFORMED AT THE NATIONAL PHYSICAL LABORATORY. THIS report is the result of an inquiry into the work now performed at the National Physical Laboratory, with special reference to the character of the chemical, physical, and mechanical tests undertaken there ; the possibility of their interfering unduly with the business of other agencies ; and the desirability of publishing the resalts of all such testing work. The committee appointed by the First Lord of the Treasury coiisisted of the Right Hon. G. Balfour (chairman), Sir Andrew Noble, Bart., K.C.B., P.R.S., 3Ir. W. J. Crossley, 'hl.P., Sir J. Wolfe Barry, K.C.B., F.R.S., and Mr, R. Chalmeru, C.B., and it is of opinion that the work proper for a National Physical Laboratory to undertake was correctly laid down, so far as the main lines are concerned, by t h e committee of 1898, and that this work should include not only physical research directly or indirectly bearing on industrial problems, and the standardisation and verification of instruments, but also-under proper conditions-the testing of materials. A considerable amount of evidence on the two points to which the committee's attention was specially directed-(i.) the possibility that the mechanical, physical, and148 THE ANALYST.chemical tests actually undertaken by the Laboratory may interfere unduly with private enterprise; (ii.) the desirability of publishing the results of all such testing work-was taken, and on both of them a marked divergency of opinion was disclosed.As regards undue interference with the business of other agencies, the con- troversy has in a large measure turned upon the right interpretation of the Report of the committee of 1898. I n paragraph 9 of that Report the committee stated that it would neither be necessary nor desirable to compete with or interfere with the testing of materials of various kinds as now carried out in private or other labora- tories,” and a little further on they give examples of such matters as would, in their opinion, ‘‘ be proper for investigation at a public institution, as distinguished from the ordinary testing of materials used in commerce or in construction and machinery, which can be, and is now, efficiently conducted at private establishments.” Witnesses, representing professional analysts and engineering testers, naturally point to these passages as showing that the work of testing samples of materials in order to ascer- tain whether they comply with a given specification was laid down by the committee of 1898 as altogether outside the scope of the Laboratory’s activities.The inadequacy of the equipment has, until quite lately, been a considerable check upon the amount of work which it would have otherwise undertaken under the head of “Testing of Materials.” This is especially true of the engineering branch. Up to the year 1905 no complaints had been made that the sphere of private enterprise was being invaded by the Laboratory. The alarm was first raised by the analytical chemists, and in consequence of representations made by the Society of Public Analysts and by the Society of Chemical Industry, certain changes, already referred to, w3re introduced into the pamphlet issued by the Laboratory in 1906.These changes seem to be, on the whole, regarded by those interested as sufficient, if acted up to in spirit as well as in the letter, to afford them reasonable protection. I n the 1906 pamphlet fees are no longer specified, and an explanatory statement is added, making it clear that chemical analyses only form part of the ordinary work of the Laboratory, so far as they may be required for the purposes of the physical or mechanical examination of a material. I n addition, however, to these concessions, the Society of Chemical Industry further asked for the insertion in the opening sentence of the pamphlets of the words given below in italics : ‘‘ The National Physical Laboratory has been established .. . as a public institution for standardising and verifying instruments, for testing materials, as distinguished from ordinar9 testing of materials used iu co7izmerce OY iii, constmction and machiimy, which testing C C L ~ be, aid now is, eficiently conclz~cted at private establisheizts, and for the determination of physical constants.” The In- stitute of Chemistry also asked for a limitation in practically the same words. The Laboratory authorities did not consider that this restriction had been imposed upon them. Public attention has since been called to the matter, and ultimately the ques- tions at issue were referred for consideration to the present committee.The opinion is expressed that private testing establishments, and also professional analysts who are in the habit of adding engineering tests to chemical analyses, were beginning to look on the policy they attributed to the Laboratory as a serious menace to theirTHE ANALYST. 149 interests. These fears are regarded as exaggerated, for it has never at any time been the intention of the authorities of the Laboratory to ignore entirely the limitations of paragraph 9, and compete injuriously or unfairly with private agencies. Even were it otherwise, the unfavourable situation of Bushy House, away from the great manufacturing establishments, and from the offices of consulting engineers, would probably always preclude it from absorbing any large share of the business carried on by those agencies.There is some force in the argument urged by Mr. Maw, that the research work of the Laboratory in devising new methods of testing and elaborating old ones, would probably do more in the long run to increase the business of existing agencies than competition in the work of commercial testing is likely to diminish it. But, while holding that the apprehensions of those interested in testing work are probably excessive, the committee cannot regard them, in view of the diverse interpretation placed upon the Report of 1898, and of the important additions recently made to the equipment of the Laboratory, as unreasonable or wholly with- out foundation. A more precise formulation of the testing work proper to be under- taken by the Laboratory is evidently desirable in order that public and private interests may be as far as possible harmonised.The committee do not attach weight to the argument that unless the Laboratory is allowed to undertake ordinary commercial testing, it will be insufficiently provided with funds for the less remunerative but more important part of its work. Or, on the other hand, that any large development in undertaking commercial testing would gravely impair its usefulness in that higher work of research which is its true and proper function. The experience of the Reichsanstalt and the Material-Priifungs Amt in Germany may be quoted against any such apprehension. No doubt if the energies of the entire staff of the Laboratory were to be largely absorbed in purely commercial work, this would be an evil.But there appears to be no probability that this result will ensue, no matter how the issue at present in controversy is decided. On the other hand, a certain amount of ordinary routine testing is of real value for the purpose of keeping the staff continuously abreast of practice. If all so-called commercial testing of materials is to be rigidly ruled out, its exclusion would, the committee considers, react with serious effect on the research work itself of the Laboratory, as far as industrial problems are concerned. How best to consult the reasonable interests of private testing establishments without impairing the public utility of the Laboratory is a question rather of practice than of principle.Before proceeding further, it seems to be necessary to endeavour f o define what is meant by ‘ I Commercial Testing,” as it appears that there has been some confusion of ideas in much that has been said and written on this subject. I n the first place, there is the ordinary testing of materials to ascertain whether their quality and behaviour are in accordance with the requirements of contracts. Testing of this nature, though much of it is now done in the testing departments of various manufacturers as part of their contract, appears to form a very considerable and probably the most lucrative part of the total work of private testing establishments. I t is usually strictly routine work within defined lines to determine whether samples accord with specification, and does not call for anything but care and observation.The committee denominates this Contractual Testing,” and it occupies a position150 THE ANALYST. apart from other testing or standardising work. So far as public interests are concerned, it is a matter of indifference where such “Contractual Testing” is carried on, and the chief ways in which any restriction upon it would affect the National Physical Laboratory would be in its finances, and in the loss of its effect on the training of the staff of experimenters. The other branch of “ Commercial Testing ” is in the nature of investigation for commercial purposes of various substances in which no question of contract arises. Though distinct from “ Research ’’ in the strict sense of the term, it commonly has in it an element akin to Research. Such enquiries demand much time and skill, and the results may not only affect important commercial undertakings, but also be of great public interest. Many of the tests made in such investigations are of the same nature as those for “ Contractual Testing,” but require to be repeated under varying conditions and for lengthened periods, and to be tabulated and analysed.Taken singly, the tests may be of the routine character familiar in ‘‘ Contractual Testing,” but their scope and outcome are different, and demand invention and adaptation to the end in view, if valuable results are to be obtained. Though such investigations have been and can be undertaken by private establishments with more or less efficiency, the committee considers that applicants for the services of the National Physical Laboratory ought not to be refused its assistance in such enquiries, because the work could possibly be undertaken else- where also, if preferred.Apart from the interests of the applicants, it would be an injury to the public at large to lose the authoritative results of such investigations from a public institution highly equipped both as to personnel and machinery; and it is more than possible that if such investigations cannot be undertaken at the National Physical Laboratory, they will be diminished in numbers or not entered upon at all. Investigatory Testing ” would be to hinder the advance of knowledge. It is not a question of the kind of tests applied to any particular substance or material, but of the nature and objects of the investigation to be undertaken which differentiates “ Contractual ’’ and ‘‘ Investigatory Testing.” The Laboratory should remain absolutely free with regard to “Investigatory Testing,” while the case of those representing private testing establishments would be sub- stantially met, if as a general rule it were debarred from undertaking “ Contractual Testing ” as above defined.The committee recommend this restriction, subject, however, to the follow- ing exceptions : There are some tests, chiefly electrical, thermal, optical and physical, which cannot be carried out adequately, if at all, in any existing private establishment. I n such cases it would obviously be absurd to debar the Laboratory from undertaking the work merely on the ground that the tests are intended to ascertain whether certain materials comply with the requirements of a contract.I n the second place, no restriction should apply to ‘( reference ” testing wherever, in cases of dispute, the parties concerned agree to refer their differences to the authoritative decision of the Laboratory, or where the Laboratory is called in by a Court of Law or of Arbitration. Lastly, in view of the character of the Laboratory as a public institution, it ought to be free to accept any work which any Government Department may desire to commit to it. Reference testing, for the To place restrictions uponTHE ANALYST. 151 settlement of disputes, would not involve any undue interference with the work of outside agencies; while as to Government work, it is improbable that much of this would in any circumstances find its way to private testing establishments.As an additional safeguard against injurious competition with private enterprise, wherever the same tests of materials are carried out, both by the Laboratory and by outside agencies, care should be taken that the fees charged by the former should be at least as high as those normally current. In the case of reference testing they should be distinctly higher. It has been represented that the fees at present charged by the Laboratory for ordinary commercial tests are in some instances lower than those usually charged by private establishments. Whilst accepting the assurances of the Laboratory authorities that it was not their intention in any case to undercut prices, the committee think more attention should be paid to this matter than appears to have been done heretofore.The existing rule, based on the recommendation of the committee of 1898, is immediate publication of all results, except in special cases approved beforehand by the executive committee. I n practice very few, if any, exceptions have been admitted. This rule, as interpreted, has proved too rigid, and should be relaxed. There is evidence that insistence on immediate publication of results has already deterred, and must often deter, manufacturers and others from submitting to the Laboratory investigations likely to yield new results of great importance that would hardly be attainable through any other agencies.It is recommended that in cases where publication is deferred a considerably higher fee should be charged to the persons for whose immediate benefit the investigation is to be carried out. I t is possible that by raising the fees for reference testing and by increasing the number of research investigations carried out on behalf of private persons, and the charges made for them, the Laboratory may be enabled to recoup any loss of prospective income caused by the restriction on Contractual Testing. I t has been suggested that the authorities of the Laboratory might with advantage be kept more closely in touch with the practical needs of industry by the institution of small advisory committees representative of different technical interests. The executive committee has already power to appoint sub-committees of this kind, including members not already on the General Board or executive committee; such committees were, in fact, appointed at the institution of the Laboratory, and their members are frequently consulted by the Director, although no regular meetings are held. These committees should, however, be kept up-to-date and in close touch with the executive committee. Sir A. Noble and Sir J. Wolfe Barry are of opinion that the restriction recom- mended in respect of “Contractual Testing” should come to an end after a definite time. A restrictive period of ten years would adequately meet the case presented on behalf of private testing establishments, and would safeguard the interests of the public, which will be best served by leaving the authorities entrusted with the administration of the National Physical Laboratory completely free (as is the case in the National Laboratories of Germany) to exercise their discretion in accepting or refusing any description of testing work.

ISSN:0003-2654    

DOI:10.1039/AN9083300147

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

152 THE ANALYST. LOCAL GOVERNMENT BOARD REPORTS. On Certain Imported Meat Foods of Questionable Wholesomeness. (Reports of Inspector of Foods, No. 3 and 4,1908).-The data which are embodied in Report No. 3 relate to imported boneless scrap-meat, imported pork (in regard to tuberculosis), and imported tripe, tongues, and kidneys, which are heavily dosed wit11 boron and other preservatives. I t is considered that the unchecked admission of boneless scrap-meat into the United Kingdom constitutes a definite risk to health, and as the volume of trade in this commodity is small, prohibition of its importation would cause but little interference with trade. Tripe, tongues, and kidneys are some- times imported in strong solutions of :preservatives, and the meats take up large quantities of the preservatives from the solutions.Samples have been met with containing up to 2.18 per cent. of boric acid. I t is therefore considered desirable for the Board, under the Public Health (Regulations as to Food) Act, 1907, to prevent the introduction from abroad of tongues, tripe, and kidneys, which arrive in receptacles containing any preparations consisting of or comprising boric acid, borax or other borates, sulphurous acid or sulphites. To these may be added preparations of formaldehyde, benzoic acid or benzoates, salicylic acid or salicylates, or fluorides. Report No. 4 deals with the circumstances attending the preparation and sale of tripe and its importation from abroad, The conditions in London and Lancashire appear to be generally wholesome and cleanly.The consumption of imported tripe lnvolves a risk to health from the preservative compounds present, and there is the further danger that decomposition may have taken place before the sense of smell can detect it. w. P. s. The Preparation and Sale of Vinegar in Relation to the Administration of the Sale of Foods and Drugs Act. J. M. Hamill. (Reports of Inspector of Foods, No. 5, 1908.)-A description is given of the general methods of preparing brewed and artificial vinegars, together with typical analyses (cf. ANALYST, 1891, 16, 83; 1894, 19, 15, 26), and it is stated on the authority of information supplied by different firms that the cost of raw materials is about the same (twopence per gallon for a vinegar of 5 per cent. strength), though the greater cost of manufacturing brewed vinegar brings the final costs to about fivepence and threepence per gallon respectively.The attempts made by the London and County Vinegar Brewers’ Association to agree upon a definition and fix a standard for malt vinegar have not been successful, and the minimum for the specific gravity (viz., 1.017 to 1.021 for a, vinegar containing 5-17 per cent. of acetic acid) proposed by the Association in 1907 is here adversely criticised, as is also the provision of official definitions. Reference is also made to the question of the supervision of vinegar factories, which is favoured by many brewers. It is recommended that genuine vinegar should contain a t least 4 per cent. of acetic acid, and that artificial vinegar should not be sold as “ vinegar ” unless some word be added to make the nature of the substance apparent.The addition of sulphuric acid must be regarded as an adulteration, and the forma- tion of Prussian blue in a vinegar which has been clarified by mean8 of potassiumTHE ANALYST. 153 ferrocyanide must be looked upon with suspicion. This last recommendation is based upon the results of experiments made by Dr. A. Harden, from which it appears that an acid solution of potaseium ferrocyanide is slowly oxidised, with the formation of Prussian blue and hydrocyanic acid : 7H,Fe(CN), i- O,= 24HCN + 2H,O + Fe7(CN),,. This formation of Prussian blue also took place in vinegar to which had been added the proportion of potassium ferrocyanide ordinarily used in the trade for clarification. On boiling the clear filtrate from the Prussian blue with magnesium chloride in neutral solution, no hydrocyanic acid could be detected, this being apparently due to a combination of that acid with some other constituent of the vinegar, possibly the aldehyde. But the hydrocyanic acid could be set free to a large extent by boiling the vinegar, and only disappeared very gradually on keeping. No opinion is offered as to the toxicity OE vinegar thus treated. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9083300152

出版商:RSC    

年代:1908

数据来源: RSC