摘要:

(1) EXAMINATION OF WORT. (2) ESTIMATION OF STARCH. BY E. W. T. JONES, F.I.C. (Read at the Neetiny at Learnington in July.) Looama over my notes, it has occurred to me that a short paper, compiled from those having reference to the above subject, may interest public analysts. Although the work does not come under our official duties, doubtless many like myself have been con- sulted by private clients on the subject, with a view of rebutting excise charges as to the alleged improper use of sugar. This subject has more or less occupied my attention for many years, and the more one works at it, the greater do the complications appear, and, with all due and very great respect to the Somerset House chemists, whose work, I am sure, is always conscientious, I have strongly felt, with increasing conviction, that the testimony on which they base their charge of added sugar to wort is of the most inconclusive character.(1st) The specific rotatory power of the solids of the wort, i.e., the deviation in angular degrees [a]j or [a],, of 10 grms. of the solids in 1OOc.c. through 1,000 m.m. (2nd) The cupric reducing power of the solidsof the wort, i.e., the initial reduction with (‘ Fehling ” of the wort calculated in p. c. of dextrose on the solids. These terms will be better elucidated for those unacquainted with the subject by the methods, the use of which I propose t o describe in detail. When a sample of sweet wort is submitted for examination, if salicylic acid has not been added, it is desirable to add some at once for its preservation.1 grain per fluid oz. I find will keep wort in a quiescent state for months. This gives an additional gravity of 0.7, which correction can be made. Take carefully the specifk gravity at 15*5W., and divide all above 1,000 by 3.86; for giving grms. of solid matter per 100 C.C. (3.95 is, perhaps, the more correct di- vision, but 3.86 is generally used, and is retained here). They rely upon what is called164 THE ANALYST. Now take 50 c.c., most carefully measured, of the wort, put into a correct 100 C.C. flask, add 2 C.C. of solution of basic acetate of lead, mix and make the bulk, with dis- tilled water, exactly 100 c.c., pour on to a dry filter and collect the clarified wort, which will be fit to examine in the polariscope. I use a Soleil-Venkyke-Scheebler, but, of course, it is not essential to use this particular instrument, though personally I like it.Whatever instrument be used the result must be expressed in angular degrees through 1,000 m.m., for 10 grms. of the solid matters of the wort per 100 C.C. This is the specific rotatory power, either [u]j or [aID according as the sensitive tint or the yellow sodium light is employed. My results are with the former. Example-a sample of wort was found to have a sp. gr. at 15-5OC. 1,077.24. 77’24- - 20.01 grms. of solid matter per 100 C.C. 3.86- Sp. ry. pr.-50 C.C. of the wort clarified with the lead solution as described, and diluted to 100 C.C. (hence remember only half the original strength), gave in the polariscope, with the 100 m.m. tube, a scale deviation of +30*1 (three observations agreeing).This scale reading is now multiplied by 0.385 to obtain real angular degrees, and by 10 in order to obtain the rotation for 1,000 m.m. thickness of the solution. Thus 30.1 x ~385 x 10 =115*885 ; the solution, however, contains 10°005 grms. of solid p. 100 C.C. Consequently we have 10.005: 10 : : 115*885 : x=115*8, the sp. ry. pr. required. Cupric Reducing Power.--20 C.C. of the clarified wort, being diluted to 100 c.c., 10 C.C. (equal to 1 C.C. original wort) with 35 C.C. Fehling solution diluted with 70 C.C. water and heated in a beaker surrounded by boiling water for 15 minutes, gave after ignition of the precipitate (1) 0.2215. (2) 0.2220 grm. CuO. mean 0.2217 ; this X 0.4535 gives a reduction equivalent to 0.10056 grm. dextrose for the solid matter in 1 c C.of the original wort, viz., 0.2001 grm., calculated into a percentage on this equals 50.25, and this is the cupric reducing power of the wort, proposed, I believe, by O’Sullivan to be shortly designated K. I would here emphasize what Mr. O’Sullivan hang long ago pointed out, that the best way (if not the only correct one) of taking the cupric reducing power of a solution such as wort, is that described by him in the J.C.S., 1876, vol. ii., p. 130, viz., to di- lute a suitable amount of the Fehling solution with twice its bulk of water, and after it has attained the proper temperature by standing in boiling water, to add the sugar solution, and digest 14 to 15 minutes in the beaker, surrounded by the water kept boiling. The volumetric method, with its variable time and other conditions, is not admissible in the presence of dextrin or with such solutions as wort.The Somerset House chemists assert that a genuine malt wort should have a sp. ry. pr. not less than 120 [u]j 3.86 and a cupric reducing power not over 50 or 51. In the example given the wort was made by myself, under carefully observed conditions, with some of the same malt as used by the brewer who was charged with using sugar. Sp. ry. pr. 115.8 [.]j 8 . 6 K3%6 50.25. Note the result of the examination of this wort :-THE ANALYST. 165 Some of the defendant’s wort, forwarded from Somerset House by his desire, Sp. ry, pr. 116.5 K 50.8 The Somerset House chemists’ results, as given in Court, being : - Sp. ry. pr. 120.0 I< 57.2 gave on analysis:- They made no remark on the sp.ry. pr.; but on the cupric reducing power of 57.2 they based their charge of 1.60 p. c. of added sugar (glucose) to the wort. Now, as all of my experiments were made in duplicate, I assert that the analysis of the wort made by myself, and known to be free from added sugar, absolutely disallows any proof based on this result, of any having been used in the brewing complained of, and the mashing temperature and other conditions in the experimental brewing were those not unreasonable but even likely for the actual working. The malt is somewhat ex- ceptional in giving so low an optical activity, but on looking at the table and the in- fluence on the optical activity by keeping worts it was probably slightly higher when first examined, as the Somerset House result goes to show, but I am convinced that their 57.2 for cupric reducing power is an error caused by using the Fehling solu- tion volumetrically in the presence of dextrin.I append a table showing (1) Difference in character of worts from two different samples of malt, (2) Influence of mashing temperature on the wort. (3) Influence of time (4 months) on wort preserved by salicylic acid. I believe that the Somerset House chemists place some reliance for detecting the presence of added cane-sugar to wort on the extra reduction of Fehling after heating in boiling water bath for 15 minutes with 2 p. c. of normal sulphuric acid but all the worts I have examined give a little extra CuO after this process, which is probably due only to the hydrolysis of some of the dextrin, and not to cane-sugar at all.For instance: the I< of 50.25 in the wort I made myself, became 57.34, aild the sample received from Somerset House went to 56.25 after this treatment. Dextrirt.--To estimate this in a wort I take 10 C.C. of the clarified wort, add 16 C.C. normal sulph. acid, dilute to about 70 c.c., and boil on the hot plate for 4 hours in a flask covered by a glass marble, keeping at the same bulk by additions of water ; when cool I add 16 C.C. N. soda and make to 100 C.C. 10 C.C. (equal to 0.5 C.C. orig. wort) submitted to the Fehling test, and the CuO calculated for 100 c.c., deduct from this the CuO found in the initial Fehling test, after multiplying it by 1.68436, for the amount of CuO yielded when maltose is converted into dextrose, and multiply the remainder by 0-40816 for dextrin.Table showing difference in Wort from two samples of Malt, tho effect of temperature and time in maahing on the constitution of the Wort, etc. :-166 TRE ANALYST. Maslier1 Temperature ...... ::: ... ...IF. 135-140°F. 20-165°F. - Sp. Gr. at 15.5' C. . . . . . . 1067.49 107098 Holids, per 100 C.C. by divisor' 3 086 . . . . . . 17.48 18.39 Sp. Rt. Pr. [a]j . . . . . 121.14 134.42 Cupric Reducing Pr. ... 47.99 I 39-50 Gmmmes per 100 C.C. Maltose, (i.e., all the initial cupric reduction calculated as such) . . . . . . . . . . . . Dextrin . . . . . . . . . . . . . . . Albuminous matter, etc. (by difference) ... Percentage on the Solid Hatter. Maltose, as above computed .. . . . . . . . Dextrin ... . . . . . . . . . . . . Other Bodies (by t%fference) . . . . . . . . . Worts made by myself in Lahratory. - __ __--- I 135-140' 2 liours. I? 1077.24 20.01 50.25 115.8 16.08 1.57 2.36 S0.36 7.85 11-79 3 hours. 35-140Q E 1062.24 16.12 51-84 113.6 13.37 1.27 1.48 82.94 7.88 9.18 Somerset I souse Publican's Wort alleged to contain Sugar. Analysis Gample forwarded from of the foregoing Wort. I 6ornerset House. Analyzed by me. 1 Jan. '86 10s0*00 20.72 53.01 114-4 17.57 151 1-64 84.80 7.29 7.91 Experiments with Starch.-As allied to the subject of my wort paper, I propose to give an analysis of a sample of maranta starch (arrowroot) by O'Sullivan's method, and the subsequent treatment of the wort (I may call it) by acid to complete hydrolysis, also the result of treating a portion of the starch directly with acid to complete hydrolysis, For O'Sullivan's paper see J.C.S., 1884.Six grammes of arrowroot, being gelatinised in about 80 C.C. water, after cooling to 62O C., 0-04 grm. diastase dissolved in about 2 C.C. of water was added, and the temperature kept 62O to 63O C. for about an hour; the solution was then boiled, and filtered through a weighed filter, the reBidue left on the filter after washing and drying and allowing for the ash equalled 0.18 per cent. on the arrowroot. The solution being more than 100 C.C. was evaporated, and made exactly 100 C.C. at 15*5O C. ; its sp. gr. was 1020.34. This solution examined by the polariscope through the 200 m.m. tube, gave a deviation of + 46.2 scale degrees.3.021 grms. of the solution gave with B'ehling 0,1645 grm, CuO; this equals 5556 grms. CuO for the 100 C.C. 5.556 x 0.7256 = 4.031 grms. of maltoss in the 100 c.c., and as 1 grm. of maltose p. 100 C.C. gives with the 200 m.m. tube a, deviation of 8.02 scale degrees, with this instrument 4.031 grms. would give 32-33 scab degrees of deviation as due to maltose; the remainderof the 46.2 total deviation, viz., 13.87, must be due to dextrin, 1 grm. of which p. 100 C.C. with the 200 m.m. tube gives a deviation of 11.56 scale degrees, hence the 13-87 equals 1.200 grms. dextrin. Now we have in the 100 c.c.-THE ANALYST. 167 Maltose, 4.031 X 0.9478 = 3,821 grms. starch. Dextrin, 1.200 = 1*200 ,, ,, - 5.021 grms. of starch in the 100 c.c., or, from the 6 grms. taken, a percentage of 83.69.gave 0030 per cent. of ash, hence we get- The sample of arrowroot used lost 15.40 per cent. by drying in water oven, and it Moisture .: .. .. .. 15.40 Starch . . .. .. .. . . 8369 Fibre . . .. .. .. . . 0.18 Ash .. .. .. .. . . 0.30 Loss, etc. .. .. .. . . 0.43 100~00 Having ascertained that we have in this solution of starch products- Maltose, 4.031 grms. p. 100 C.C. Dextrin, 1.200 ,, 9 , Diastase, 0.040 ,, ?, let us treat it with acid to complete hydrolysis, and see how the chemical mothod of estimating the dextrin agrees with the optical. About 20 C.C. (weighing 20.4245 grms.) of the solution, being diluted to about 60 c.c., is submitted to hydrolysis by boiling for 4 hours with 16 C.C. normal SO,, then 16 C.C. normal NaHO added, and made exactly 100 C.C. - 10 C.C.of this solution yielded with Fehling solution 0.2500 grm. CuO, or 2.50 grms. for the 100 c.c., which corresponded to 20.4245 grms. of original solution of the starch Weight of 100 C.C. of the starch products found from sp. gr. products-20*4245 : 102.034 : : 2.50 : x = 12.49 grms. CuO for 100 C.C. of the starch products. Now from the initial cupric reduction, and that after full hydrolysis, we should be able to calculate the dextrin, and so compare it with the amount found with the polariscope. The initial cupric reduction of the starch products solution was 5.556 grms. CuO for the 100 c.c.-remembering that when maltose is converted into dextrose by hydrolysis the original reduction of 471.276 CuO for the molecule becomes 793.80 CuO for the molecule of dextrose formed-we know that the initial reduction of CuO due to maltose must be multiplied by 1.68436 to give the amount of CuO that would be yielded when converted into dextrose, hence 50556 x 1.68436 = 9-36 CuO as due to the hydrolysis of the maltose ; this deducted from the total CuO found after full hydrolysis, viz., 12.49, leaves 3.13 CuO as due to the hydrolysis of the dextrin.This multiplied by 0*40816, the factor to convert CuO produced from the hydrolysis of the dextrin into dextrose, gives 1.278. So we find- By the optical and chemical method combined. By chemical method alone, i.e., initial CuO and after hydrolyeis. Maltose, 4.03 Maltom, 4-03. Dextrin, 1-20 Dextrin, 15%. To complete these experiments I treatod 1 grm. of this starch mixed with 46 C.C.168 THE ANALYST. H20 with 5 C.C. strong HCI and boiled for three hours-neutralised with soda and made exactly 100 C.C. With Fehling this gave 2.056 CuO for the 100 C.C. 2.056 x 0.40816 = 0.8392grm. starch, or 83.92 per cent., against 83.69 per cent. found by O’Sullivan’s method. As a summary t o these statements, I would say that, although genuine malt worts made under ordinary conditions from most malts would have a sp. ry. pr. [a]j 3.88 of over 120 and a cupric reducing power of under 50, there are malts that give worts having n lower sp. ry. pr. and a higher cupric reducing power under conditions that small publicans may reasonably subscribe t o in their brewing, and thus it is unsafe to base a charge of fraud on these data. My notes on the starch estimations illustrate the exact procedure by 0’8ullivan’s method, and the full hydrolysis by acid of the solution of starch products of known com- position. The mode of calculating the results and their comparison with the former method may prove interesting to many members, as may also the direct full hydrolysis of some of the same starch by acid.

ISSN:0003-2654    

DOI:10.1039/AN887120163b

出版商:RSC    

年代:1887

数据来源: RSC

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168 THE ANALYST. UNRELIABILITY OF ANALYSES OF SAMPLES OF MILK WHICH. HAVE BECOME PARTIALLY DECOMPOSED BY KEEPING. C. ESTCOURT, F I.C., F.C.S. THIS matter is becoming of such importance to public analysts generally, that it appears advisable that any special experience on the part of members of our Society should be brought prominently before all interested in the matter. With this view, I will very briefly give the results of analyses performed at different periods, by three different analysts, upon the same sample of milk. The first analysis was made by myself as Public Analyst upon the milk purchased 26th February last, delivered to me and analysed the same day. I certified to 14 per cent. added water. The second analysis was made by a local chemist and druggist upon the portion left with him by defendant on the 12th March.The chemist who performed the second analysis stated that the milk was quite decomposed and yet stated that he performed three separate analyses, all agreeing. How could he possibly mix a decomposed milk so completely as to be able to take out three separate portions which would give exactly similar percentage results for fat and solids not fat? This gentleman, whose whole experience in milk analysis had he said extended over three years, had only had a very recent experience of the method of Somerset House, which he used in the present case. It appears, therefore, more than likely that he did not get off all the fat, and he did not weigh the solids not fat, the discrepancy is easily explained. This analyst said no water had been added, but admitted that the sample mas adulterated as it had been skimmed.The third analysis was made by the chemists of the Somerset House Laboratory upon the third portion sent up by the magistrates on the 25th March, at request of defendant. When the milk reached Somerset House it was undoubtedly in a very decomposed state, and hence this case exhibits the unrelisbility of the analyses in a very pronounced manner. The Somerset House analysts as usual say, that ‘6 after making the allowance for 10s~ by decomposition,” they are of opinion the milk has been watered to the extent of 40 per cent.THE ANALYST. 169 They do not state whether such allowance is included in the figures. 1 2 3 Analysis of Milk when Analysis of Milk when fresh, 26 Feb., 1887. decomposed, 12 March, 1887. Not fat 7.70 8-77 Not fat 4.79 Fat 3-10 Allowance *40 Fat 1-47 Analjsis of Milk quite decomposed, 25 March, 1887. Total solids 1Og8O Not fat 9.17 Total solids 6.26 Fat 2.06 Total solids 11.23 These figures require no further comment.

ISSN:0003-2654    

DOI:10.1039/AN8871200168

出版商:RSC    

年代:1887

数据来源: RSC

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THE ANALYST. 169 NOTES O F LEGAL PROCEEDINGS INTERESTING TO ANALYSTS. (These notes aye collected and edited 6y the Secretaries of the Society df Public A.nalysf8, in viytue of a ~ e 8 o l u t h to that efeot, and theirpublication will be corzti?zued from time to tlmc in the portion of the ANALYST devuted to the Society’s @airs) IN a case heard at Lancaster Police-court, a grocer named Wilson was charged with having sold pepper containing 15 per cent. of olive stones, starchy matter, and other foreign vegetable matter. The case brought into Court representatives of the grinders and the wholesale dealers, and these admitted the adulteration, and that the retailer was quite innocent of this adulteration. The defendant had obtained his pepper from a Liverpool firm, who had in turn been supplied with it by Messrs.White, Palmer, and Co., Limited. Mr. Thomas Vacher Low, the managing director for this firm, said they supplied the pepper and warranted it. He was willing to admit that the pepper complained of was a part of what they supplied, and that the analyst’s certificate was more or less accurate. Owing to a fire at a large grinder’s in London, they had had a most extra- ordinary demand for pepper, and mere compelled to buy to meet the demand, a thing they had never done before. They got it through brokers, and it was guaranteed as genuine. They took every precaution to have it tested, and sent some samples to Somerset House, where it was declared t o be pure, but they had since found that the pepper was adulterated. At Swansea, there have been some interesting prosecutions for selling beer adulter- ated with common salt.In one instance, the Borough Analyst, Dr. W. Morgan, certified to the presence of chlorides in a proportion corresponding to 70 grains of common salt per gallon. The sample was referred to Somerset House, whence a certificate was returned aflirming the presence of chlorine equal to 67 grainsof common salt. Mr. R. Bannister was examined, and stated that some natural waters contained chlorine in greater proportion than this, so that there w a no proof of adulteration. No attempt was apparently made to determine the actual sodium chloride present. In a case heard at Birkenhead, in which Mr. J. Carter Bell condemned a beer as adulterated with water, and evidence was given that there was no standard, and that, therefore, water could not be detected in beer. bar. Bell states that he found on analysis the original gravity of the beer to be 1043,*and consequently wrote to the Inspector, who went to the brewer who supplied the beer. Tho brewer said he supplied the beer, and when it left the brewery the original gravity ww 1051. Hence he had distinct evi- dence of adulteration, and gave a certificate accordingly that there was 6 gallons of added water in every 36 gallons of beer. Com~usion, of the Society’s Proceedings.

ISSN:0003-2654    

DOI:10.1039/AN8871200169

出版商:RSC    

年代:1887

数据来源: RSC

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170 THE ANALYST. ON BECHI’S TEST FOR COTTON-SEED OIL I N OLIVE OIL. Abritlged from the Report of the Commission of Florence, appwinted to examine Test.” See L’Orosi,)’ Feb., 1887,~. 37. TRANSLATED BY JOSEPII W. ENGLAND, PEG.* IN a lengthy and exhaustive communication, the Commission of Florence has made public the results of the experiments upon the value of the “Bechi’s Test,” as a reliable and positive indicator of the presence of cotton-seed oil, fraudulently contained in olive oil. This Commission, appointed in the early part of last year, was as follows : U. Peruzzi, N. Ridolfi, and Prof. G. Roster. The method of Professor Bechi, as used by the Commission, and with successive modifications by the author, consists in the subjection of a sample of the suspected oil to the heat of boiling water, after first having added an alcoholic solution of silver nitrate, and amylic alcohol and oil of rape, il; the manner and proportions hereinafter indicated.Take one grain of crystallked silver nitrate, and dissolve in the smallest possible quantity of water (about 1 c.c.), and add 200 C.C. of alcohol (96O). The addition, also, of 20 C.C. of sulphuric ether is a good one, in that it makes the reagent better miscible with the oil to be examined, but it is not necessary. On the other hand, prepare a solution composed of 85 parts of amylic alcohol and 15 parts of oil of rape seed. These reagents should be made as needed, and not kept on hand for any length of time. Now, to apply the test, Prof. Bechi takes 10 C.C. of the oil to be examined, adds 1 C.C.of the alcoholic solution of silver nitrate and then from 8 to 10 C.C. of the mixture of amylic alcohol and oil of rape ; agitating strongly, and then heating on a water-bath for 5 or 10 minutes. In the case of pure oils the colour remains the same as it was after the addition of the reagents. In the event that sophistication hhs been practised with cotton-seed oil, there will be produced a brownish colour or turbidity, of a varying grade, from a very light brown to a deep maroon or black, according to the quantity of cotton oil present. With these data furnished by Prof. Bechi, and after having assisted in experiments made by him in support of his method, the Commission instituted a series of long and diligent personal experiments, numbering over 200, in the chemical, biological, and hygienic laboratory of the Royal Institute; adhering strictly to the rules as laid down, measuring exactly, in each instance, the quantifies of oils and reagents, and using tubes of equal diameters, or, in one word, employing the same conditions in all experiments, in order to render the result truly comparative.The oils used were furnished in part by Prof. Bechi and in part by this Commission- looking, especially, for those olive oils of whose genuine nature there could be no pos- sible doubt, and then, secondly, taking good olive oil containing cotton oil. Several of the olive oils were from other countries (Spain, France, Tunis, Dalmatia, and Malta, etc.), but the greater number were from various parts of Italy. Some were recent and some old ; others pure of la, 2a, 3a quality ; and others were rancid.In order to ascertain if the reaction outlined by Bechi was peculiar to cotton-seed oil addition, alone, the Commission found it necessary to extend their experiments upon other oils, vegetable and animal, alone and admixed with pure olive oil. Bechi’s * American Journal of Pharmacy.THE ANALYST. 171 Every experiment made was in doubles or triples, that is two samples of the oil (marked No. 1 and No. 3), and another Eample of the oil (marked No. 3), which had added to it cotton-seed oil in a certain proportion ; subjecting No. 1 and No. 2 samples to the heat of boiling water, after the addition of tho reagents, and leaving No. 3 sample without exposure to heat, in order to compare the colours of Nos.1 and 2 with that of No. 3. The experiments were then especially directed toward the mixture of olive oil with oil of cotton seed. The proportion used for the mixture was, generally, 20 per cent. of the latter oil. The Commission held that, if the method of Prof. Bechi will determine any such falsification, it is more than sufficient for any exigency, inasmuch as the fraud practised is always in much larger proportion. The experiments were grouped mder five series. Series A.-Cotton-seed oils of various origins. Eleven samples of oils from the following markets were used :--1. London ; 2. New Orleans; 3. Augusta; 4. Louisville; 5. Sample (S years’ old); 6. English (Hirsch); ‘7. Thorn; 8. Maginnis; 9. Planter’s; 10. Aldigh; 11. Creole. All these oils, treated with the ‘‘ Bechi test,” gave a most intensely brownish colour, that exhibited no appre- ciable variation in shade, according to the origin of the product.The experiments were then repeated upon the oils, using 2 C.C. of oil of cotton to 8 C.C. of olive oil. The olive oil used was from Pons of Scandicci, upon whose genuineness there can be no question. Series B.-Pure olivo oil, alone, and admixed with oil of cotton. The aeries of experiments here outlined were based upon the first, second, and, in some instances, the third, quality of 48 oils, giving also the origin of each oil. The samples were subjected to comparative tests, alone, and then admixed with 20 per cent. of Hirsch’s English cotton-seed oil, the most abundant in Italian markets; in every instance the 48 oli17e oils, alone, were negatively affected by the reagents, but the instant cotton oil was admixed, and the test then applied, the result was promptly given by the formation of the deep, brownish colours, in every instance.series C.-Various oils, alone, or mixed with Hirsch’s English cotton-seed oil. The oils here examined are 25 fixed oils of different qualities, liable to be used as an adulterant. They are, for example, oils of rape (Germany, Milan, Marseilles, etc.), sesame (Levant, Georgia, Bombay, Paris, and Grasse), peanuts, poppy, linseed, cocoanut, castor, almond, peach-seed, and cod-liver ; and the results show that, in every case, there Was no appreciable change with the reagents, but if, prior to the application to the test, 20 per cent.cotton oil was added, the characteristic colour of the reduction was formed. series B.-Pure olive oil with other fixed oils, alone, and with cotton oil. These experiments were made to ascertain if the presence of other fixed oils than cotton seed, in a mixture, mould have any modifying influence upon the reaction, SO ~haracteristic with oil of cotton, It is sufficient to say that the results show that they have none, and the Commission find that the test is therefore limited to that fixed oil alone. The cotton-seed oil was added in 20 per cent. proportion, when used with both oils of olive and benne (in the secondary tests), which latter two were evenly divided (ie., 40 per cent.), while the oil of sesame was added in equal parts to olive oil, prior to the application of the primary tests.Series 3.-Rape oil of different origins, alone, and mixed with cotton oil.172 THE ANALYST. The Commission, in view of the importance that oil of rape obtains, in the applica- tion of Bechi’s test, examined seven oils of various qualities, derived from different provinces. From these experiments the assertion is made that, while several of the finest samples in the pure, undiluted state, furnished a noticeable change in the forma- tion of a reddish-brown colour, this was always made very much darker if 20 per cent. of cotton-seed oil was previously added; and, on the other hand, if the rape oil ex- amined was previously diluted with pure olive oil or smylic alcohol, as, for example, in the proportions used by Prof. Bechi in his test, no change whatever was evinced.Finally, the Commission, wishing to see if a variation of the proportion of the reagents would more clearly demonstrate results, used a stronger solution of silver nitrate, and found that the brownish colour could be made to vary from brown to black, accord- ing to the quantity of the silver salt added. After numerous experiments they decided that the original proportions were the best ones to adopt, in that the test would be much more dolicate, and would not, under any circumstances, be caused by the rape oil. To examine olive oil for admixed cotton oil, with Bechi’s method, the Commission recommend the division of the suspected sample into three parts, as follows :- No. 1. Tube of the suspected oil and reagents.No. 2. Tube of the suspected oil and 20 per cent. of cotton oil, and the reagents. No. 3. Tube of the suspected oil and reagents. Now expose tubes No. 1 and No. 2 to the heat of boiling water for 5 or 10 minutes, but do not heat tube No. 3 ; use it simply as a guide to see if No. 1 remains unaffected by heat or becomes coloured. If the sample is pure, the oil will remain unchanged, that is, the =me in appearance as No. 3, while No. 2 acquires the characteristic colour. If the oil in tube No. 1 has been sophisticated with cotton oil the brownish colouration will soon appear, while tube No. 2 will be a much deeper brown; evidently showing that the brownish colour is due, in part, to the quantity of cotton-seed oil present, as well as the proportion of silver nitrate and oil of rape.From all that has been presented, and more especially from the clear, concording, and uniform results obtained in the experiments herein detailed, it is evident that the method proposed by Professor Bechi, used with care, and in the manner indicated, has not failed the Commission in a single instance, and they feel that they cannot do less than to most strongly urge its general adoption, as a reliable and positive indicator for the existence of cotton-seed oil in olive oil, fraudulently added. In the original article no theory is advanced concerning the chemical reaction that takes place in the application of the (‘ Bechi test,” but it seems highly probable that the change is due to a reduction of the silver nitrate to the state of oxide, through the presence of the peculiar yellow colouring principle present in cotton-seed oil. The product, after the testing is finished, measures 11.5 c.c., showing that the residue is simply a mixture of the suspected oil (10 c.c.) and oil of rape (1.5 c.c.), while the alcohols have been totally dissipated by the heat of the water-bath. The utility of the rape-seed oil in the decomposition is not explained, and whether the amylic alcohol, through any chemical change, exerts any influence is also an unsolved problem.

ISSN:0003-2654    

DOI:10.1039/AN8871200170

出版商:RSC    

年代:1887

数据来源: RSC

摘要:

THE ANALYST. 173 THE COXPARATIVE DELICACY OF SOME QUALITATIVE TESTS. BY J. S. C. WELLS. I HAVE so often been shown tests by students, and asked if they indicated any appreci- able quantity of the substance tested for, that I have thought it might be of interest to know just how delicate some of the more important tests are. I have begun with the metals of the fifth group (according to Fresenius), and the accompanying tables show the results obtained. Many tests might, no doubt, have been carried even farther than shown in table by using larger quantities of liquid and allowing them to stand for a longer time. My idea, however, was to obtain results, such as any student might, with the ordinary apparatus used by him. For this reason the tests were all made in the ordinary six-inch test tube, and, unless otherwise stated, were not let stand more than five minutes.It will be seen from the table that nearly all show, even in very dilute solutions, and that- some of them, such as the precipitation of lead by H2S, are wonderfully delicate. It should be remembered that the results given were obtained in solutions containing nothing but the substance tested for and the reagent; no foreign substances being present. The results in column I. show the point beyond which it was impossible to distinguish distinct particles of the precipitate. After passing this point the reaction was indicated by a mere cloudiness or colour. In column 11. is shown the extreme limit of the test, that is, the most dilute solution in which any reaction was obtainable. In order to get a clear idea of how dilute such solutions are, it may be well to state that one part in one million is equivalent to one grain in seventeen gallons.SILVER (Ag). I. Part of Parts Reagent. substance. of water. NH,Cl . . .. .. 1 20,000 HCl . . * . .. 1 20,000 KBr . . .. .. 1 30,000 K2Cr207.. .. .. 1 3,000 KX . . .. .. 1 5,000" H,S . , . . .. 1 5,000 Part of substance. 1 1 1 1 1 1 11. Parts of water. 350,000 250,000 200,000 200,000 800,000 3,000 MERCURY (Hg). Hg.,O. NH,Cl . . .. .. 1 25,000 1 200,000 HC1 . . .. - 3 1 25,000 1 200,000 H,S . . . . . . 1 5,000 1 1,000,000 SnCI, . . .. . . 1 50,000 1 200,000 K2Cr207. . .. .. 1 20,000 1 100,000 R2S . . .. .. 1 2,000 1 1,000,000 SnCJ, , . .. .. 1 50,000 1 200,000 c u , . .. .. 1 10,000.f. NH,OH . . .. 1 25,000 1 25,000 HgO. NB,OH .. .. 1 4,000 1 4,000 * Only shows on standing some minutes. t Shows in volution of 1-100,000 after standing four hours.174 THE ANALYST. LEAD (Pb) I. Part of Parts Reagent. substance. of water. HC1 .. .. .. 1 500 NH@l . . .. .. 1 600 H2S .. .. .. 1 20,000 H2S in K O H solution . . -- -- H2S04 . . .. .. 1 10,000 K2Cr20,. . .. .. 1 10,000 NH40H .. . c 1 10,000 H,O$ .. .. .. 1 10,000 BIsnf UTH (Bi). H2S .. .. .. 1 13,000 K2Sn02§ .. .. 1 40,000 COPPER (Cu). H2S .. .. .. 1 2,000 NH,OH .. .. K4FeCY6 .. .. 1 2,000 H,S+HCl II .. .. 1 20,000 K4FecY6 .. .. -- -- CADMIUM (Cd). H,S .. .. .. 1 4,000 -- -- Qualitative Laboratory, School of Mines. Parts of substance. 1 1 1 1 1 1 1 1 1 1 1 1 11. Parts of water. 500 600 1,000,000~ 1,000,000" 20,000 t 100,000 1,000,000 12,ooo.F 90,000 90,000 1,000,000 80,000 1,000,000 200,000 200,000 4,000

ISSN:0003-2654    

DOI:10.1039/AN8871200173

出版商:RSC    

年代:1887

数据来源: RSC

摘要:

174 THE ANALYST. THE POLARIZATION OF MILK. BY H. W. WILEY, CHEMIST TO THE U.S. DEPARTMENT OF AGRICULTURE. 1.-SPECIFIC ROTATORY POWER OF MILK-SUGAR. CRYSTALLIZED milk-sugar when first dissolved possesses a higher rotatory power than it has in the milk from which it was derived. This increased optical activity may be com- pared with the original by the ratio 8 : 5, nearly. After the solution has stood for twelve to twenty hours, or immediately on boiling it, this extra rotatory power is lost. In estimating the specific rotatory power of milk-sugar the numbers given always refer to the constant, and not the transient, gyratory property. Among the earliest numbers assigned to the rotation of lactose are those of Pog- gide (a), = 54.2 and Erdmann (a), = 51.5 [Sucrose (a), = 66.51.places this number for lactose at 60.23, and Berthelot ** at 59.3 for the transition tint (a)j. Hoppe- Seyler, in his ‘‘ Handbuch der physiologisch-chemischen Analyse,” gives this number a t (ax = 58.2. Since the ratio of (a), to (a)j is 1 : 1.1306, the above numbers become for Biot * Seen only on looking down the tube. t Only on standing a few minutes. 6 This is the test with KOH and SnCl,, yield& Bi,O,. 11 I found that the addition of a few drops of HC1 made the precipitate separate much better than 7 Compt. Rend., vol. 42, p. 349. ** Wurtz Dict. de Chim., vol. 2, 1st part, p. 188. This test was made on a solution of Bi(N0. ) in presence of NH,CI. it would in either alkaline or neutral solutions.THE ANALYST. 175 ~ Biot (a), = 53.2'7, for Berthelot (a), =52*47, and Hoppe-Seyler (a), = 51.48.Resse* observed the rotation number to be (a),= 52.67 when the solution contained 13 grams, per 100 C.C. and the temperature was 15O C. On the other hand, when the concentration is only 2 grams, per 100 C.C. the number assigned is (a)D = 53.63. It appears from this that the specific rotation power of a solution of milk-sugar diminishes with the increase of its concentration, and this view is adopted by Landolt, Tollens, and Schmidt. The following general formula? is used to correct the reading of the polariscope for concentration of solution :-- in which c = number grams. sugar in 100 C.C. solution. These observations are contra- dicted by the work of Schmoeger,$ who, in an elaborate series of experiments, using in- struments of different construction and observing all necessary precautions, found the rotation number of lactose sensibly constant for all degrees of concentration up to the saturation point.I n thirty-two series of investigations, in which the degree of concen- tration gradually increases from c = 2.3554 to c = 36.0776, and in which a constant tem- perature of ZOO C. was maintained, the variations in the numbers obtained were always within the limits of error of observation. The mean of all these numbers fixes the value of (a), at 52.53, According to Schmoeger variations in temperature have far more to do with changes in rotatory power than differences of concentration. The value of (a), falls as the temperature rises. Under 20° C. the disturbing influence of temperature is greater than above ZOO C.At the latter degree (a), varies inversely about 0075 for each lQ C. change of temperature. Pellet and Biard,§ as a result of their observations, fix the rotatory power of milk-sugar at 58.94 for (a), [a. ;(a),= 52-12]. After a careful review of the methods used in the above r8suniG and the numbers determined by them, I am inclined to accept the mean obtained by Schmoeger as the one entitled to the greatest credit. It also has the advantage of being almost the mean of all the various numbers which have been assigned as the specific rotating power of (a), = 54*54-*5575~ + *05475~~-*0017746, lactose, viz. :- Poggiale .. Erdmann .. Biot . . .. Berthelot .. Hoppe-Seyler . . H e w .. .. Hesse . . .. Schmoeger . . Pellet and Biard Mean .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 54.20 51.50 53.27 53-47 51.48 52.67 53-63 52.53 52.12 52.65 I n the present state of our knowledge, therefore, the specific rotatory power of milk-sugar should be taken at (a)== 52.5. I propose, at an early date, to make a careful study of this subject, in order to fix, if possible, an exact number for the expres- * Anal. Chem. u. Pharm., vol. 176, p. 98. t Tucker, Sugar Analysis, p. 91. J Ber. chem. Gessell, vol. 12, p. 1922 et. seq. 9 Bull. de 1'Assoc. des Chimistes vol. 1, p. 171 et. 8eq.176 THE ANALYST. sion of the rotating power, and to examine the conflicting evidence respecting the influence of the degree of concentration on the same.The estimation of lactose in milk by the polariscope is rendered difficult also by the presence in milk of various albumens -all of which turn the plane of polarization to the left. As will be seen by the data given further along, the ordinary method of removing these albumens, viz., by a solution of basic lead acetate, is far from being perfect. If, therefore, a portion of the albumen be left in the liquid submitted to polarization, the rotation to the right will be dimin- ished by its presence. Hoppe-Seyler* assigns as the rotation power of egg albumen (a), = - 35.5, and for serum albumen (a),-= - 56. Both acids and alkalies seem to increase the rotating power, which may with acetic acid reach (a), = - 71.Fredericq? gives the rotation number for blood serum for the rabbit, cow, and horse at (a),= - 57.3, and for the dog at - 44. Paraglobulin, according to the same author, has a rotation number (a), = -47.8. Milk albumen: has the following numbers assigned to it :- Dissolved in MgSO, sol. (a)u= - 80 (a)= = - 87 Dissolved in dil. HC1. Dissolved in dil. NaOH sol. (a)== - 76 Dissolved in strong KOH sol. (a), = - 91 The hydrates of albumens have rotation powers which vary from (a),= - 71-40 to (a), =- 79.05. From the chaotic state of knowledge concerning the specific rotating power of the various albumens, it is impossible to assign any number which will bear the test of criticism. For the purposes of this report, however, this number may be fixed at (a), = -70 for the albumens which remain in solution in the liquids polarized for milk-sugar. The phenomenon of ‘‘ birotation ” in milk-sugar has already been noticed.The problem of analysis of this sugar is, however, still further complicated by the facts pointed out by Schmoegerll and, Erdmann,q that when milk is rapidly evaporated in a plain dish the sugar is left in the anhydrous state, and that this sugar in fresh solutions exhibits the phenomenon of “half rotation.” When such sugar is extracted with alcohol and re-evaporated, it, doubtless, is still anhydrous. But in the calculation of results this sugar is generally estimated as containing water of crystallization, and thus an error, which Schmoeger reckons at as much as *2 per cent., is introduced into the results.This fact, not well recognised, combined with the knowledge that in the pro- cess of evaporation many particles of sugar must be occluded by the hardening caseine, tends to throw doubt upon the accuracy of estimating the sugar by the extraction method. The work which I undertook had for its object the determination of the best method of preparing the milk-sugar solution for the polariscope, and a comparison of the numbers obtained by this instrument with those given by the ordinary process of extraction. * Wurtz, lXct. de Chimie, vo!. 1,lst part, p. 91. t Compt. Rend., vol. 93, p. 465. 9 Kiihne and Chittenden, Am. Chem. Jour. vol. 6, p. 45. 11 Ber. chem. Gesell, vol. 12, 1915 et. seq.; vol. 13, p. 212 et. seq. Hoppe-Seyler in Handbook of the Polariscope, Landolt, p.248. Ber. chem. Gesell., vol. 12, F. 2180 et. s q .THE ANALYST. 177 The reagents used for removing the albumens were :- Saturated solution basic lead acetate, specific gravity 1.97. Nitric acid solution of mercuric nitrate diluted with an equal volume of Acetic acid, specific gravity 1-040, containing 29 per cent. HC,K,O,. Nitric acid, specific gravity 1-197, containing 30 per cent. HNO,. Sulphuric acid, specific gravity 1.255, containing 31 per cent. R,SO, Saturated solution sodium chloride. Saturated solution magnesium sulphate. Solution of mercuric ioditle in acetic acid; formula* HI, 33.2 grams. Hg CI,, 13 5 grams. Strong HC2H302, 20.0 C.C. Water, 64.0 C.C. Alcohol, ether, and many solutions of mineral salts, hydrochloric, and other acids were also tried as precipitants for albumen, but none of them presented any advantages which would make a detailed account of tho experiments of any interest.Table No. 9 contains a record of the experiments which led to the adoption of 1 C.C. acetate of lead solution, or 1 C.C. acid mercuric nitrate, as the best amount of each for 50 C.C. of milk. From two to four observations were made with each sample. An average of these readings was taken for each determination. In the calcalations the value of (a), was taken at 53 instead of 52.5, the number which subseqnen% investigations have ied me to believe more exact. The instrument employed mas a ‘ 6 Laurent Large Model ” polariscope. In all cases the volume of the solution was corrected €or the volume of the pre- cipitated caseine.Since in the Laurent instrunlent the weight of sucrose in 100 C.C. to read even degrees on the scale is 16.19 grams, [(u), =66.67], it follows that the weight of lactose in 100 C.C. to read one degree on the scale for each per cent. lactose present would be 16-19 : x =53 : 66-67’; ~=20*37. Nearly all the polarisations were made in a 400 m.m. tube. The volume wag assumed to occupy 2 C.C. for each 50 C.C. milk. If 53.5 be taken as the value o f (u), for lactose, then x = 20.56. In table No. 9, A indicates acc:tic acid,, Pb basic acetate of lead, MR acid mercuric nitrate, etc. The letters C! and H indicate the temperature-C denoting the ordinary temperature of the room, ;and H that tha sample was heated to loo* C. and cooled before filtering.The numbers obtained by extraction with alcohol are taken as the basis of com- parison, not because I believe them to be more reliable, but because that method is the one generally employed in the estimation of milk-sugar. In the alcohol extraction the milk was evaporated to dryness in a thin glass mp- sule, the dish and dried residue pulverised i;n a mortar, washed with ether into a con- tinuous extraction apparatus, exhausted witb ether, and then with 80 per cent. alcohol for ten hours. Duplicate analysesare indicated in the bble by the small brackets. II * Jour. de Pharm. et ae Chim., vol. 10, p. 108.17s THE ANALYST. Pb lcc. Pb 2cc. Pb 3cc. - 2 i E - 1 2 3 4 6 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 - Pb ?oc.f;. A 5cc. Other reagents. a 2 8 gal g!! $a- 7 2 : - a < k 4.5; 45: 4-4t 3.9: 4-3E 3.71 4*1C 41C 4*4€ 4*1C 4.8C 4.77 425 4.22 3.14 3.30 4.72 4.88 431 4.39 4.70 4.96 4-60 474 4 59 4.39 4.60 4-26 4-90 H {i::: H 4.43 H 4.45 (t'8"; El 4.71 [ 4.86 H 4.1 1 4117 4.93 (4.97 H f 4.41 I4.45 f 4.41 1445 H r 4.33 14-37 H 4.18 H 3.67 H 4.68 B 4-18 NaCl { 429 H -7- [ 4.37 14.25 r443 i443H ' 468H 466H 3.98 { :'!: H 4.27 (6.e.) 4.4.3 H,80, {4:51 {4:59 3.96 4 7 9 E 459H I *38 -87 '. IMB 29 B 66 09 3 90 3.90 4.32 4.4PH { i:?: H I I 469 467 H 3.94 410 432 455H {i:?: H -- (lo".: 1.45 (P.) -31 I -38 #65 - 306 3.5 3.3 3 9 - 423 414 3.57 4-32 3-00 {% H { 2% H H2SO.a 3.80 [ 3-67 H 3-47 H, r 4.45 14.43 H f 3.86 .3*86 4-21 .435 El 3.94 3-93 H I I La50 I; 1.88 P= P78 I3 Remarks on Table No.9.-The results obtained by using various other reagents for the precipitation of the caseine, viz., MgSO,, CuSO,, HC1, etc., have not been entered in the table. In none of these cases was there sufficient encouragement to warrant an extended trial. In most cases the precipitation was slow or imperfect, and the filtration difficult. One important fact should not be overlooked, viz., that any excess of basic plumbic acetate causes a rapid decrease in the rotatory power of the solution; whether this decrease is due to precipitation of the sugar or solution of the albumens does not clearly appear. Illustrations of this decrease are seen in analyses 2, la, 13, and 17. It seems to make little difference whether the precipitation is made hot or cold.THE ANALYST.179 - No - 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 62 53 54 55 56 57 58 59 60 61 62 63 64 Av. - The question of temperature is set forth in greater detail in the next table. From all the experiments made it clearly appeared that the best optical results are obtained by the use of a minimum quantity of basic lead acetate, or of either the acid mercuric nitrate or iodide. For 50 C.C. t o 60 C.C. of milk, 1 c c. of the lead acetate or mercuric nitrate solution of the strength noted, and 25 C.C. of the mercuric iodide solution are the proper quantities. It makes no difference, however, if a large excess of the two latter reagents is employed. Of the three the last is to be preferred. In Table No. 10 will be found the results of the comparative determinations of milk-sugar by extraction with alcohol, by precipitation with 1 C.C.basic lead acetate, and the same with 1 C.C. acid mercuric nitrate, hot and cold, to each 60 C.C. of milk. In many of the analyses the large differences in results by the three methods show a fault of manipulation, but all the results have been given without selection. TABLE No. lO.-Percentage of milk-sugar. - Nc - 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 - Extractec )y alcoho' Per ct. 4-55 4.10 4.51 4.36 4.05 3-84 4.52 4.25 4-45 4-92 3.84 4.53 4.57 4-66 4.1 7 5.02 4.68 4.2 3 4.9 6 4-85 4.63 4.47 4-46 4-47 4-40 4-85 4-45 4.44 4-10 4.38 4-20 4-69 4.52 Reagents employed. C. Pb. lcc Per d .... .... 4.54 4.55 4.14 4.67 4.2 1 4.6 1 5-20 4.6 1 4.54 4.29 3.65 4% 6 4.03 3.82 4.70 4.39 4.47 4.39 4-23 4.59 4-4 1 4.6 7 4.2 1 3.98 4.21 5.57 4.2 1 4-69 4.27 ........ H. Pb. lcc - Per ct 4-74 4-22 4-22 4.53 4.09 3.84 4.73 4.26 4.54 5.22 3.72 4.64 4.55 4.45 3.75 4.64 3 -94 3.89 4.84 4.41 4.47 4.45 4.31 4.67 4.55 4.73 4-33 4.10 4.69 4.37 4.67 4.4 1 .... - C. MR. lcc Per ci .... .... 4.68 4-89 4-48 5-01 4-87 5.43 4.00 4-87 4.9 1 3.95 4.86 4.39 4.08 4.04 4.53 4.69 4.67 4.65 5.01 4.45 4.97 4.57 4.28 4.55 4-89 4.57 4.89 4-41 3.98 .... .... H. MR. lcc ~ Per ct 4-92 4-50 4.62 4.90 4.39 3.98 5.00 4.5 1 4.87 5.47 3-96 4.85 4-44 4 63 3 *87 4.86 4.37 4.02 5.04 4.65 4.67 4.71 4-63 4-95 .... .... .... .... .... .... .... .... .... Extracted 3y alcohol Per ct. 4.37 4.52 4.88 4.61 4.79 4.67 4.79 3.95 4.00 4.63 4.77 4-85 4-71 4.34 4.05 3-67 3.78 4.1 9 3.83 3.86 4.59 4.02 4.36 4.20 4-09 4.09 4.1 2 4-20 4.45 4.33 4.62 4-33 Reagents employed. C.Pb. lcc Per ct 4-65 4.27 4-83 4-30 4-59 4.26 4.64 4.1 0 4-61 4.24 4.64 .... .... 4.06 4.67 4.1 2 4.58 4-27 4-68 3.97 4.59 4.26 4.62 4.18 4.52 .... .... .... .... .... .... -- 4.34 H. Pb. lcc Per ct 4.93 4.41 4-93 4-43 4-67 4-41 4.74 4.26 4.6 1 4-37 4.70 4.5 3 4-67 4.12 4.77 4.1 8 4.62 4.57 4.78 4-07 4.61 4.36 4-76 4.28 4-56 4-28 4.49 4-33 4-25 4.09 4-33 4.38 ~ C. HR. lcc - Per ct 4-93 4-56 5.17 4.5 7 4.9 1 4-5 1 4.94 4.38 4-77 4.57 4.94 4.73 4.93 4.40 4.83 4.36 4-82 4.53 4.97 4.2 1 4-83 4.40 4.94 4-48 4-74 4-46 4-81 4.41 4.77 4.37 4-99 4-58 -- H. dR. ICC. E'er ct. .... .... .... .... .... .... .... .... .... .... .... .... .... .... ..1..... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... 4-63180 THE ANALYST. acetate :- Number. I n the following table will be found the percentage of milk-sugar obtained by using varying quantities of the mercuric iodide reagent, and a comparison of the results obtained with those given by the use of acid mercuric nitrate and basic plumbio TABLE No. 1 1 .-Pe?eentuge of milk-sugar. 1 2 3 4 5 6 7 8 9 Av. Pb. Per ct. 4.28 4.46 4.37 4.37 4-38 4-33 4.30 4.33 4-37 4.34 Reagents employed. I MR. t- 20cc. I Per ct. 4-48 4.57 4.65 4.53 4-63 4-67 4.67 4.59 4.60 4.60 Per ct. 4.5 6 4-62 4.63 4.60 4.50 4-43 4.67 4.50 4.6 3 4.5 7 Mercuric iodide. 25cc. Per ct. 4.56 4.66 4.63 4.53 4.53 4.53 4.67 4.5 3 4.60 4-58 30cc. Per ct. .... .... 4.60 4.63 4.53 4.60 4-59 4.50 4-66 4.61 36cc.Per ct. .... .... 4.65 4.60 4-59 4.66 4.57 4-59 4.66 4.62 If- ALBUMEN REMAINING IN FILTRATE FROM LEAD ACETATE AND MERCURIC IODIDE SOLU- TIONS. From the fact that the polariscopic readings show that solutions of milk prepared with lead acetate have a lower rotating power than those prepared with mercury salts, it is to be inferred that the lead reagent either leaves certain soluble and transparent kinds of albumen in solution, or else dissolves a portion of those which are at fist precipitated. To test the accuracy'of this supposition a few analyses were made to determine the amount of albumen left in the filtrate from the lead and mercury reagents. At the same time different quantities of the mercuric iodide solution were used, in order to determine the amount which would give the best results. For 60 C.C.milk thequantity of mercuric iodide to be used should be 25 C.C. to 30 C.C. I n the following table will be found the percentages of albumen in the whey after precipitating with the reagents noted and filtering. Ten cubic centimetres of the filtrate were evaporated to dryness in a thin glass dish, and the dried residue (with the glass) burned with soda lime. The calculated nitrogen was then multiplied by 6.25 and the product taken as the percentage of albumen :-THE ANALYST. 181 TABLE No. 12.-Der cent. albumen in fitrate. *0789 Av* From Pb. -0888 *0839 -0964 *0828 -0865 01 130 *1130 *0865 -1130 -1130 -1130 -1 950 01130 -1412 -1130 .... .... .... From HgI,. 15cc. *1950 -0674 *0674 ~0674 00674 -0090 .... .... .... .... .... .... .... .... From HgI,. 20cc. *0865 00865 *0562 *0562 -0562 -0865 -1412 -1412 -1412 *1130 -1362 01250 *0090 *0090 From HgI,. 25cc. *0865 *0865 -1 130 *1130 003 12 *0300 -1130 01130 00865 -1412 *0090 .... .... .... From HgI,. 30cc. -0562 -0865 -0562 -0562 *0865 00865 -1412 *1412 01412 -1130 .... .... .... .... From HgI,. 35cc. 00865 *0m5 003 12 -0562 ,0562 -1412 $0562 *1412 *0865 *Of365 .... .... .... .... Number. ~ 1 2 3 4 6 6 7 8 9 10 11 12 13 14 15 Per cent. *250 *306 -135 ,272 *134 0239 -301 *305 *237 *339 0271 *305 -267 -237 *271 Number. 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Per cent. -237 -237 -169 -1 03 -271 -237 -271 -235 -271 -237 0237 a271 -339 0350 *374 Number. 31 32 33 34 35 36 37 38 39 40 41 42 Av. .. .. Per cent. -329 *305 -305 -237 -305 -339 -237 -374 *203 -373 -305 -339 -278 (TO be continued).

ISSN:0003-2654    

DOI:10.1039/AN8871200174

出版商:RSC    

年代:1887

数据来源: RSC

摘要:

182 THE ANALYST. APPOINTMENT. AT the Annual General Session of the Peace for the county of Lancashire, held at Preston on June 30th, Mr. Walter Collingwood Williams, of Liverpool, was appointed deputy analyst of food and drugs for the county, at a salary of 3150 per annum, and a fee of 8s. for every certificate .of analysis. Dr. J. Campbell Brown is still the head analyst for the county, at a salary of %300 per annum and fees.

ISSN:0003-2654    

DOI:10.1039/AN887120182c

出版商:RSC    

年代:1887

数据来源: RSC