摘要:

THE ANALYSIS OF GOLDEN SYRUP. BY NORMAN LEONARD, B.Sc. IN the December number of the Journal of the Society of Chemical I n d m t r y (1899, xviii., p. 1091) there appears, under the title of “Notes on the Analysis of Some Sngar Syrups,” a criticism, by Messrs. A. K. Miller, Ph.D., and J. H. Potts, of a recent paper on the analysis of golden syrup by Mr. R. Bodmer, Mr. H. M. Smith, and myself (ANALYST, 1899, xxiv., p. 253). Whilst admitting the fairness, from their own standpoint, of the objections raised to our work by Dr. Miller and his colleague, I wish to emphasize the fact that our paper was communicated to the Society of Public Analysts, and was written from the point of view of the Public Analyst; it was not in any way intended as an introduction of new processes for the exact analysis of sugar syrups.At the time we wrote, the analysis of golden syrup was new to Public Analysts, qud Public Analysts, and since numerous inquiries addressed86 THE ANALYST. to one of us indicated a lack of information on the subject, we thought it useful to outline a scheme of analysis, the details of which might be altered or extended to suit individual preferences, and to show how, by a balancing of probabilities, a fairly safe and generally intelligible opinion as to the nature of a sample might be arrived at. It is doubtful if any Public Analyst would care to certify the amount of glucose added to golden syrup more accurately than t o the nearest 5 per cent., and even then, seeing the variable composition of glucose and golden syrups, the adoption of such expressions as ‘‘ about 50 per cent.of glucose syrup ” or ‘ I at least 70 per cent. of glucose syrup” is advisable. I t will thus be seen that the meanings attached to the word “ approximate ” by Messrs. Miller and Potts on the one hand, and by ourselves on the other, are rather different, and that consequently many of the objections raised to our analyses lose somewhat of their force. Messrs. Miller and Potts seem not to appreciate the position of the Public Analyst, who is bound by the form of certificate prescribed by the Sale of Food and Drugs Acts to give a quantitative expression of the composition of an article which he believes to be adulterated ; he is not permitted to ‘( be content with a qualitative test.” This being so, recourse must be had to the method of averages, so much deprecated by Dr.Miller and Mr. Potts, which those whose business it is to examine products of variable composition are often obliged to employ. An exact determina- tion of all the constituents of a sugar syrup would doubtless be of great interest to the chemist and to the manufacturer, but such an analysis would, as a rule, be quite unintelligible both to the magistrate and to the vendor charged with adulteration. The analytical results would therefore require to be expressed in terms of such comparatively familiar substances as cane-sugar syrup and glucose syrup, and this would again necessitate the use of averages, for it would be impossible to say accurately how the water, ash, and organic matter were distributed between the two syrups in a mixture.Respecting the errors introduced into the estimation of the water by neglecting the influence of the ash on the specific gravity of the syrup solution, I may observe that the amount of water present is, to the Public Analyst, of very little importance. We were aware of this source of error, but it may be pointed out that large amounts of ash are, I believe, rarely found except in crude, genuine syrups which would be passed without comment by a Public Analyst, whilst in those samples which are largely adulterated with glucose syrup the ash is usually low, and the resulting error, which here becomes of niore importance, is also small, and comparable with that inherent in the divisor process when applied to such complex mixtures as those in question. Although not claiming so much accuracy for our analyses as Dr.Miller appears to have thought was the case, it may be of interest to make some remarks on the minus values obtained for invert sugar in No. 4 sample and some others. These values, which we had understood were not uncommonly obtained in the indirect analysis of complex and impure syrups, had not escaped our notice, and we had followed the matter up even farther than our critics seem to have done. For although it is quite true, taking i = 0 in the equation K = i + 0*53x, that the maxi?nzLnz percentage of glucose (on the basis of the 53 factor) in No. 4 sample is 62.6, it isTHE ANALYST. 87 possible to look at the matter from another point of view. Thus, in the equation , if there is no invert sugar i must equal 0 and x (glucose) becomes 75.8; and this is the minimzm percentage of glucose on the basis of the 134" factor.This sample is not improbably adulterated with a glucose syrup having a lower reducing power than the average assumed by us, and we have here an example of the discrepancies inseparable from the use of averages, which, however, as already stated, must necessarily be employed. I t should be remembered that the Public Analyst, whilst making use of average analyses as a basis for calculation and comparison, is, or should be, fully aware of the greater or less amount of reliance to be placed on them, and is accustomed to regard his results from various points of view, knowing that the most elaborate and accurate analysis may lead him astray unless due regard is paid to modes of interpretation and to other circumstances than analytical details. The statements of the proximate composition of the mixed syrups given at the close of our paper (ANALYST, xxiv., p. 257) are to be regarded in this light, and, although more accurate methods are greatly to be desired, Messrs. Miller and Potts appear unable to suggest a process better adapted to the wants of the Public Analyst than that described by Mr. Bodmer, Mr. Smith, and myself. ~ 66.5s + 134z - 23.li 100

ISSN:0003-2654    

DOI:10.1039/AN900250085b

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

THE ANALYST. 87 TREACLE, OR GOLDEN SYRUP. BY E. W. T. JONES. AT the request of certain friends, I beg to lay before the Society of Public Analysts my method of treating the subject of the adulteration of golden syrup with starch glucose syrup, because, although there have been several excellent papers bearing on the subject, I believe my view of the question simplifies matters without detracting from the practical accuracy obtainable by more detailed methods. Of course, I do not advocate blindly applying my formula to every sample that may be presented. I am taking things as we find them at present, and a public analyst will naturally adapt himself with intelligence to any varying conditions which may arise. Golden syrup, whether the natural by-product of the sugar industry or the artificial product from refined sugar, consists essentially of Bucrose and invert sugar, the difference between the two classes of products consisting mainly in the relative proportions of sucrose and invert sugar.By converting the sucrose into invert sugar considerable uniformity, from a polarimetric point of view, is obtained in the case of genuine samples, which at the same time are made to exhibit a greater divergency from glucose syrup, which always has a high dextro-rotation, genuine samples of golden syrup being, after inversion, laevorotatory. The following two samples will illustrate this statement. The one is Crosfield’s genuine cane syrup, and the other is Lyle’s golden syrup, the former containing nearly 40 per cent. of sucrose and the latter about 30 per cent.:88 THE ANALYST. SPECIFIC ROTATORY POWER, at 17.5" C. Original. After Inversion. \ -h----- r- blJ [UID [alj [UID No. 1. Crosfield's ... ... +26*90 +24.21 - 12.30 -11.07 No. 2. Lyle's ... ... ... +16.13 +14*52 - 15.37 - 13.83 Glucose syrup is not sensibly altered by a careful inversion treatment. The sample in my possession, which is representative of what is used, has a specific rotatory power at 17.5" C. of [a], + 121 or [.ID + 109. I therefore suggest the following simple formula for arriving at the percentage of glucose syrup in a sample of golden syrup, if the same after inversion has a dextro-rotation : A sample of golden syrup was sent to me, said by the manufacturer to contain 18 per cent. glucose syrup. It had a specific rotatory power after inversion of : [aIj +12.3 [a], +11*07 By the above formula3, it shows 18.4 per cent.of glucose syrup. I have taken the figure of the No. 1 syrup because these darker-coloured syrups are those used generally to mix with glucose syrup. The way I actually proceed with a sample is to make a 10 per cent. solution a t 15.5" C., and take the specific gravity. This should not be sensibly less than 1032, which indicates 20 per cent. of water, for I have found by carefully estimating the water in vacuo, or by drying after incorporation with thirty times its weight of sand, that the divisor 4 for specific gravity over 1,000 in a 10 per cent. solution is practically correct for the solid matter. The divisor 3.86 is correct for about 10 per cent. solution of p u r e sucrose, but gives low results, to the extent of about 3 per cent.of water in the case of ordinary golden syrup, thus all Messrs. Bodmer, Leonard and Smith's estimations of water given in their paper (ANALYST, vol. xxiv., p. 255) are about this much too low. The 10 per cent. solution above mentioned (if I wish to estimate the sucrose) I raise to a temperature of 17.5" C., and examine in the polarimeter in 100-millimetre tube. Fifty C.C. of the same solution + 5 C.C. N acid are heated in a 100 C.C. flask in boiling water for twenty minutes, then cooled, and 5 C.C. N soda are added, and the bulk made up to 100 C.C. at 15.5" C. This solution is examined through the 100- niillimetre tube at the proper temperature, 17.5" C., and the reading multiplied by two to make it correspond to the 10 per cent.solution. I do not use the 200-millimetre tube, since the inverted solution is often too dark, and I purposely avoid the use of decolorizing agents. Mine is a Ventzke- Scheibler polarimeter, and, as a matter of fact, I generally for this purpose work with scale degrees.THE ANALYST. 89 The sample referred to as adulterated with 18 per cent. glucose syrup, gave for the 10 per cent. solution after inversion + 3.2 scale divisions : Plus sale divisions observed in sample after inversion + 3.2 -per cent. glucose syrup. 0.347 _ - Thus it comes to 18.4 per cent. For the copper reduction, if it is required, I take 10 C.C. of the first solution and make up to 100 C.C. ; 20 C.C. of this (=0.2 gramme of the sample) I add to 50 C.C.of Fehling solution diluted with 30 C.C. of water, which has acquired the temperature of, and still stands in, boiling water. The mixture is allowed to remain twelve minutes, and then filtered through an ashless filter, well washed, dried, ignited in a porcelain crucible (very slowly at first, only just smouldering the filter away. The CuO then does not cohere, and is fully oxidized). The CuO x 04307 (Log i.63414) =invert sugar. Of the inverted solution I take 20 C.C. and make up to 100 c.c., and take 20 C.C. (=0*2 gramme of the sample), add to Fehling solution, and proceed as above. The quantity of CuO found in the preceding experiment is deducted from that obtained after inversion, and the difference x 0.4091 (Log 1.61186) = cane sugar in 0.2 gramme of the sample. I have examined a great many samples very thoroughly, and find that the simple method I gave at the commencement of this paper has afforded very consistent results. I t has been suggested that the alcohol test for dextrin is of no use, but if it is always applied in a definite way, viz., taking 2 C.C. of the 10 per cent. solution and adding 20 C.C. of strong (miscible) methylated spirit, the zuhite cloudiness formed is quite distinguishable from the occasional turbidity of some samples not containing dextrin.

ISSN:0003-2654    

DOI:10.1039/AN9002500087

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

THE ANALYST. 89 ANALYSIS OF A SAMPLE O F TREACLE AND OF SO-CALLED GOLDEN SYRUP. BY CHARLES GEORGE MATTHEWS, F.I.C., AND A. AYDE PARKER. (Read at the Meeting, February 7 , 1900.) VALUES USED I N CALCULsTING THE TWO ANALYSES. THE usual divisor for carbohydrates, 3-86. Value of a 1 per cent. solution of the sugar observed in a 200-millimetre tube : Soleil-Ventzke- Laurent Scheibler Divisions. Degrees. Maltose ... ... ... ... 8:;q ‘2.76 Dextrin ... ... ... ... 3.98 Dextrose ... ... 3.05 . x 0.344= Gallisin ... ... ... Cane sugar ... ... ... ... ... ...90 THE ANALYST. Cupric-reducing values : CuO equivalent to 1 Gramme of Substance. Maltose ... ... ... ... ... ... 1.37 grammes Dextrose ... ... ... ... ... ... 2-46 ,, Gallisin ... ... ... ... ... ... 1.01 ,, SAMPLE OF TREACLE (FULL COLOUR, GOOD FLAVOUR, BUT SLIGHTLY SALINE).A. Calculation of the Gravity dzcc to Ash.-Five grammes of the sample yielded 0.373 gramme of non-sulphated ash, equal to 7.46 per cent. This was shaken up with 100 C.C. of water and the specific gravity of the mixture found to be 1,003.25 ; by division o. 373 = 8.7 was obtained as solution factor. Another 5 grammes yielded 0.4485 gramme of sulphated ash, equal to 8.97 per cent., and this, similarly treated, gave a mixture with a specific gravity of 1,004-35 and a solution factor of 9.7. The mean of these two percentages of ash was 8-21, and the mean solution factor 9.2. Determinatioja of the Dry SoZids.-The specific gravity of a 10 per cent. solution of the sample was 1,032*10, and the mean specific gravity due to ash in a solution of the same strength was 1,007.55, therefore the specific gravity due to carbohydrates was 1,024-55, which, divided by 3.86, gives 63.6 per cent.of carbohydrates, and this figure added to that of the ash gives 71.81 per cent. total solids.* B. Determination of the Cane Sugar.-One gramme of pressed yeast was added to 50 C.C. of a 10 per cent. solution of the sample, the mixture kept at a temperature of 52" C. for five hours, boiled to destroy bi-rotation, made up to bulk, filtered, and examined in a 200-rnillimetre tube. 3.25 Soleil-Ventzke- Laurent Scheibler Divisions. Tkvees. ... + 5.56 Before inversion ... ... +16*16 After ,, ... ... ... - 6.33 -- 2-18 Difference . . , ... +2249 + 7.74 The Soleil-Ventzke-Scheibler divisions, 22.49 x 10 and divided by 5.02,t or the Laurent degrees, 7.74 divided by 0.1727, give 44-8 per cent. of cane sugar.C. Cupyic-reducing Pozuer. - Five grammes of the sample were dissolved in 100 C.C. of water, and the amount of cupric reduction in 2 C.C. estimated gravi- metrically by the filter-paper method and weighing as cupric oxide.$ The weight found 0.0305 grammes x 100 gives 3.05 for a 10 per cent. solution, This figure multiplied by 10 and divided by 2.36s = 12.92 per cent. reducing sugars. X Heron (Truns. Fed. Insts. Brewiiig, 1896, p. 449) regards the sulphsted ash as accurately represent- ing the ash without any correction, and he takes the solution factor for the ash as being about double that for the carbohydrates (approximately eight), but seeing that the sulphated ash is perceptibly higher than the plain ash, and the solution factor also higher, the number eight would in our viev be sufficiently accurate as applied t o the sulphated ash.t Divisor for 1 per cent. cane sugar solution in 200-millimetre tube when converted into invert sugar. Vide Morris, Tvans. Fcd. Imts. Brewiiig, 1898, p. 164. § Mean cupric-reducing power per 1 gramme of invert sugar. (Levulose = 2-26.)THE ANALYST. 91 D. Estimation of the Matter disappearing during Fernwztation.-A few granimes of pressed yeast were added to 150 C.C. of a 10 per cent. solution of the sample, and kept at about 18" C . until fermentation ceased (about seventy-two hours). The solution was then found to have the following constants : Optical activity, 0.0 ; cupric- reducing power (K,,,) (10 per cent.solution), 0.65. The specific gravity lost during fermentation was : Original specific gravity ... ... ... ... ... 1,032-10 Extract gravity after fermentation ... ... ... 1,010.78 21.32 This figure, 21-32 x 10 + 3.86 = 55.2 per cent, sugar which has disappeared during This figure, 55.2, may be compared with that obtained by adding the cane sugar fermentation. and reducing sugar estimation, viz. : Cane sugar ... ... ... ... ... ... ... 44.0 Reducing sugar . . - ... . . . . . ... ... ... 10-17 54.97 The residual cupric-reducing power left after fermentation may be regarded as due to unfermented dextrose and lzvulose, and the mean reducing value of these two reducing sugars is 2.36 (I gramme invert sugar =2*36 grammes copper oxide).Consequently 0.65 x 10 + 2.36 = 2-75 per cent. of a mixture of the two sugars, having an optical activity of 0.0. This calculated out to a mixture of 1.78 per cent. dextrose and 0.97 per cent. lamdose.* The composition of the fermented matter consisted therefore of ;- Reducing sugars calculated from original cupric-reducing power 12.92 per cent. 9 , ,, left unfermented ... ... ... ... 2.75 ), ,, disappeared during fermentation ... ... 10.17 ,, > > Estimation of the Reducing Sugars removed by Fermentation.-The amount of these is found by subtracting the polarimetric reading corresponding to the cane sugar from that of the original 10 per cent. solution of the sample : Soleil-Ventzke- Laurent Scheibler Divisions. Degrees. Original solution in 200-millimetre tube ...... 16-16 5.56 Deviation due to cane sugar (4.48 x 3.84) ... 17.20 5-92 Difference ... ... - 1.04 - 0.36 The reducing sugars were found previously to have a copper-reducing value of 2.4 in a 10 per cent. solution, and, since their optical activity was -1.04, they consisted of a mixture of 4-83 parts lamdose and 5.34 dextrose. These amounts added to the Game sugars which were left unfermented equal 5.80 per cent. lamJose and 7-12 per cent. dextrose. (For mode of calculation, see previous footnote.) $6 The composition of the mixed sugars is calculated as follows : Let x = the dextrose and (2.75 - x) =the lmulose, then slx 5 2 ' 8 + ( 2 ' 7 5 - ~ ) x -95*65=0, and ~=1.78.92 THE ANALYST. The complete analysis was as follows : Cane sugar ... ... ...... ,.. ... .. 44-80 Ltmulose ... ... ... ... ... ... ,.. 5.80 ... ... ... ... ... ... 7.12 Dextrose ... ... ... ... ... ... ... 8-21 Ash ... ... Unaccounted for =inactive matter ... ... ... ... 5.87 71.80 Difference =moisture ... ... 28.20 100*00 Had the results been calculated in the old way, viz., by dividing the weight about 1,000 of the 10 per cent. solution by 3.86, we should have the following : 32.1 3' 86 Specific gravity 1,032.1 and x 10 = 83-16 per cent. ; 83.16 would then have been formerly taken as the true solids, and the difference as moisture, and the above analysis (excluding any question of newer methods and values used in calculating the cane sugar, dextrose, and lamdose) would have become : SUMMARY. Lzvulose ... ... ... ... ... ... ... 5.80 Dextrose ...... ... ... ... .., ... 7.12 ... ... ... ... ... ... ... 8-21 Ash ... Iqznct ice matte?. ... ... ... ... ... ... 17-23 Diferemc = m o i s t w e ... ... ... ... ... ... 16-84 Cane sugar ... ... ... ... ... ... 44.80 100~00 SAMPLE OF SO-CALLED GOLDEX SYRUP (FULL GOLDEN COLOUR, PLEASANT FLAVOUR). A. Five grammes of the sample yielded 0,067 grammes of sulphated ash = 1.34 Specific gravity corresponding to ash in 10 per cent, solution 0.134 x 8 = 1,001.07. Correction for ash ... per cent. Specific gravity of 10 per cent. solution of sample ... ... 1,030-40 ... ... ... ... ... ... 1.07 1,029-33 ... . L ... ... ... 1.34 29-33 + 3-86 x 10 = Carbohydrates per cent. ... ... . . I 75.92 Ash ... Total solids ... ... 77.26 B. By inversion with yeast, as in the former c&e, 11.3 per cent.of cane sugar was found. Soleil-Ventzke- Laurent Scheibler Divisions. Degrees. Deviation in 200-millimetre tube for 10 per cent. solution of sample ... ... ... t53.6 + 184THE ANALYST. 93 C. Cupric-reducing power of 100 C.C. of 10 per cent. solution, 7-65 grammes CuO. D. Specific gravity of 10 per cent. solution before fermentation ... 1,030.4 Extract after ... 1,013-5 J 7 9 , 9 , 7 9 Loss ... ... 16.9 16.9 + 3-86 x 10 = 43-70 per cent. fermented. 33.56 , , unfermented. 77.26 ,, total solids. Soleil-Ventzke- Laurent Scheibler Divisions. Degrees. Deviation in 200-millimetre tube after fer- mentation ... ... ... ... ... +31*2 + 10.7 Cupric reduction in 100 C.C. ... ... ... ... ... 1.544 grammes E. Determiiza tioiz of coiizbined Dextriiz (Amy loin-dextriiz).-Any ma1 tose existing in combination as malto-dextrin would reveal its presence by an increased reducing power after treatment of the fermented solution with cold-water malt-extract,':: and this released maltose would be removed by a subsequent fermentation with yeast. To 100 C.C. of the fermented 10 per cent. solution 10 C.C. of malt-extract were added, and the mixture kept at a temperature of 55" C. for two hours. A considerable increase in the cupric-reducing power ensued ( = 18.3 per cent. of dextrin), but inasmuch as the solution after treatment with malt extract was not susceptible of fermentation to an appreciably further point than the non-treated portion, we do not consider ourselves justified in using the figure so obtained for dextrin.The same rather curious fact has been noticed in the case of two or three other syrups which had been undoubtedly manufactured from cereals or cereal starch. This consideration of the failure of the solution treated with malt-extract to ferment further than the untreated solution, also affects the question of the combined maltose, which should be-like the maltose produced from hydrolysed dextrin- rendered fermentable by the action of the cold-water malt-extract, and therefore the whole cupric reduction shown by the 10 per cent. solution after plain fermentation is not to be calculated as combined maltose. There is, on the contrary, every reason to believe that it is mainly due to gallisin, and it will be seen that consistent results are to be obtained if this view be adopted.We assumed the residual cupric-reducing value of 1-46 to be due to gallisin, and 1.46 x 10 + 1-01 = 14.4 per cent. of gallisin. This amount would cause a deviation in a 200-millimetre tube of 1.44 x 4.85 = 6.98 Soleil-Ventzke-Scheibler divisions, or 1.44 x 1.67 = 2-40 Laurent degrees. The deviation observed after re-fermenting the fermented solution which had been treated with malt-extract was 22-8 Soleil-Ventzke-Scheibler divisions, or 7.84 Laurent degrees, and this, less the deviation due to gallisin, was 22.28 - 6.98 = 15.3 Soleil-Ventake-Scheibler, or 5.26 Laurent degrees, and either (15.3 x 10 + 11.56) or (5.26 x 10 -+ 3-98) equal 13.2 per cent. of dextrin. * Made by intimately mixing 100 grammes of finely-ground pale malt with 250 C.C.of water, and allowing the mixture to stand for twelve hours, giving i t an occasional stir. The clear filtrate is used (vide Morris and Moritz, " Text-book of Brewing," pp. 477-480).94 THE ANALYST. The matter remaining after treatment with malt-extract and re-fermentation amounted to 30 per cent., and as 27-6 per cent. was shown to be gallisin and dextrin, 2-4 per cent. was left nnaccounted for. The total matter which had disappeared during the first fermentation was 43.7 per cent., and deducting from this the 11.3 per cent. of cane sugar, 32-4 per cent. of reducing sugars were fermented. These consisted of a mixture of maltose and dextrose, having a cupric-reducing value of 6.106 (original KlOo 7-65 -- residue K,,, 1~544)~ which equals 1.88 grammes of CuO to 1 gramme of substance. The deviation in a 200-niillimetre tube equal to this 32.4 per cent. of substance was :- Soleil-Ventzke- Laurent Scheibler Divisions.Degrees. Original deviation . . . ... ... ... ... 53.60 18.44 Deviation after first fermentation.. , ... ... 31.20 10.73 22.40 7-70 Deviation corresponding to cane sugar estimation 4-34 1 *49 -- 18.06 6.21 And either (18.06 x 10 + 324 = 5.57, divisor Soleil-Ventzke-Scheibler) or (6.21 x 10 + 32.4 = 1.91, divisor Laurent) equal the deviation in a 200-millimetre tube due to 1 gramme of substance. These values correspond to a mixture of 16-84 parts of nialtose and 15-56 dextrose.* SUMMARY. Cane sugar ... ... ... Maltose ... ... . , . ... Dextrose.. . ... ... ... Combined maltose . . . ... Gallisin ... ... .. . ... Dextrin ... ... ... ... Difference = unfermentable by Ash ... ... ... ... plain fermentation . . . ... Moisture = 22.74 per cent. Per cent. 11-30 16.84 15.56 0-61 14.40 13-20 4-01 1.34 77.26 Soleil-Ventzke- Scheibler. Corre- sponding angle 200 millimetres, 10 per cent. solution. 4.34 13-50 4.74 0.49 6-98 15.26 8.92j- 54.235 Corresponding 10 per cent. solution. K O " C.C.9 - 2.30 3.82 0.08 1-46 - -t -t - 7.6611 * From the cupric-reducing value : 51 109 2'46xfl.37 (1 -.c)=1*88, and :i=- - dextrose. From the rotation : 3'05.c + 8.02 (1 - a) = 5.57, and J; = 245 dextrose. 497 $. Angle disappearing on degrading and refennenting. $ K taken account of already as combined maltose. 5 Compare with original angle 200 millimetres. 1 ' Compare with original K,,, C.C.THE ANALYST.95 DISCUSSION. The CHAIRMAN (Mr. A. H. Allen) invited discussion, with special reference to the question of refermentation after the addition of malt-extract, and to the authors' assumption that gallisin was a substance of definite composition, possessing a definite reducing power and optical activity. Dr. SYKES said that in all starch conversions, whether effected by acid or by diastase, undoubtedly certain bodies were present which could not be fermehted by yeast alone, but which under the combined influence of yeast and diastase were readily fermentable, a fact utilized by the spirit or vinegar manufacturer, who did not boil his wort, and consequently preserved his diastase intact during the fermentation. I n a glucose determination the removal of these bodies was, as mentioned in the paper, secured by fermenting the once fermented solution after the addition of malt- extract.Dr. DYER said he considered that, in dealing with this subject, a mistake had often been made in treating treacle, or any form of sugar syrup-a mixture of cane sugar and invert sugar-as an entity. Glucose syrup, however, for all practical purposes, could be so treated. Certain figures could be assumed as being safe outside limits to take for commercial glucose syrup, but no figures at all could be taken as representing constants for treacle or golden syrup." Probably, indeed, some of the mixtures which had to be dealt with were not mixtures of glucose syrup with what would be called golden syrup or treacle, but consisted of commercial glucose syrup with the addition of crude sugar of some kind dissolved in water.I n such cases the cane sugar was far higher in proportion to the invert sugar than would be the case in ordinary treacle or inverted syrup made from sugar, With the assistance of Mr. Sydney Steel, and from information kindly furnished to him by other chemical friends with experience in glucose syrup, he had arrived at the conclusion that it was quite safe to assume certain constants for glucose syrup : not exactly average figures, but figures representing the outside limits likely to be met with in the glucose syrup used for these mixtures--figures which would, if anything, give to the mixer the benefit of any doubt. Specific rotatory power - [a], . . . ... ... +113*0 Cupric oxide reducing power (" K value ") ...42 Where a polarimeter was used, which was graduated, not for angles, but for percentages of sugar, the rotation for '( normal weight " dissolved in 100 C.C. of water was +170 divisions. Occasionally samples of glucose syrup were met with having a higher rotation, but such cases were exceptional. From polarization at 20" C., before and after inversion (by Herzfeld's method), and determination of the copper reducing power, the percentage of glucose syrup was calculated from the following formula, in which R stands for the specific rotatory power [a],, at 20" C., of the uninverted sample, S for the frotation due to the sucrose present, and K for the copper reducing Dower : The following were the figures assumed for glucose syrup : 0.206K + (R - S) Percentage of glucose syrup = - 1.217 * Mr.Jones, in his paper on p. 87 of this number, suggests that, after inversion, sugar syrup may be regarded as an " entity." This materially reduces the liability to error through the assumption of a constant composition, but appears less satisfactory than tha mode of calculation described in this paragraph.-B. D.96 THE ANALYST. If a polarimeter reading percentages were used, and the observation made on '' normal weight " of the syrup, R being the '' percentage " reading before inversion and S the percentage of sucrose, the formula was : 0.31K + (R - S) ~ I__. 1-83 Percentage of glucose syrup = - The method was substantially that described some time back by Mr. Boseley for the estimation of glucose in marmalade, differing mainly in that the syrup, and not the L' solids '' dissolved in it, was treated as the direct basis of calculation. Mr.Chapman, after making a number of analyses of syrups more or less on the lines of those detailed in the paper of Messrs. Matthews and Hyde Parker, had also applied to his results this simple mods of calculation, and an interesting comparison was thus afforded between this method and the more elaborate and more scientific determina- tions which took into account the percentages of the different individual carbohydrates present. Mr. CHAPMAN said that, whilst the rotation and copper oxide reducing power obtained, after fermentation were assumed by the authors to be due to unfermented dextrose and ltevulose, modern methods of sugar analysis were to a great extent based on the assumption (which was universally believed to be justifiable) that dextrose and lmulose were, under proper conditions, entirely fermentable, and he ventured to think that the numbers referred to should rather be regarded as due to certain unfermentable bodies allied to the carbohydrates, which were well known to exist in raw sugars and in invert sugar, and to be possessed of very little optical activity, but of considerable cupric oxide reducing power.I n some analyses of raw sugar recently published by Mr. Glendenning, unfermentable residues, which undoubtedly did not consist of carbohydrates, being possessed of very little optical activity, but having EL cupric oxide reducing power of about 30, were shown to exist in almost all raw sugars in the proportion of from 1 to 3 per cent.With regard to the question of gallisin, he thought it a pity that definite assumptions should be made in regard to so indefinite a substance. The substance called gallisin had been obtained some years previously by a method which offered practically no guarantee as to its purity, and a body some- what resembling it had since been obtained from glucoses and other commercial carbohydrate mixtures ; but he thought there was insufficient evidence to warrant its being regarded as a body of definite composition. He had, as Dr. Dyer had mentioned, made analyses of a number of samples of adulterated treacle, four of which gave the following results : Cane sugar ... ... Invert sugar . . . ... Dextrose . * .... Maltose . .. ... ... Dextrin ... ... ... Water ... ... ... Ash ... ... ... Undetermined . . . ... No. 1. 20.63 10.80 6.10 26-40 12.95 19.08 1.82 2-22 100*00 Optical activity [a]D= + 77.3" No. 2. 26-10 12-00 22.00 -40 8.98 20.50 5-20 4-82 100~00 + 45.2" -- No. 3. 27.40 23.60 11.40 2-50 22.69 7.24 5.17 -_ 100*00 + 24.6" No. 4. 4.10 31.70 7.50 34.30 2 1 *30 1.10 - .- 100.00 + 99.01"THE ANALYST. 97 From a consideration of their carbohydrate constituents, he had concluded that they contained 52, 32,13 and 87 per cent. of glucose syrup respectively ; the comparatively simple method of calculation explained by Dr. Dyer gave 56.9, 27.3, 10.5 and 864 as the respective percentages of glucose syrup. He was now quite satisfied that the simpler method of dealing with the subject was quite sufficient for the practical purpose of determining the approximate percentage of glucose syrup in these mixtures.Mr. BOSELEY said that he had employed the method referred to in his paper on " The Analysis of Marmalade " (ANALYST, xxiii., 123) in the analysis of a, very large number of samples of jam, and had found it to work most admirably. In determining the cupric oxide reducing power in a jam, however, it was necessary to remember that in some fruits there was present a substance which was not sugar, but which, apart from the natural invert sugar of the fruit, was capable of reducing Fehling's solution, and the results published in 1898 were probably about 2 per cent. too high owing to the influence of this substance, of the presence of which, in sufficient quantity to affect the results, he was not at the time aware.He had examined a great many samples of glucose syrup, and had not found the rotation to vary largely. The figure he had adopted for (or Sp. R. P. [aID= +110"), was an average of between 200 and 300 samples obtained from different sources, the highest result obtained being 173 percentage " rotation (cane sugar = IOO), viz., 166 (Or Spa R. P. [U]D= + 115"). Mr. JULIAN L. BAKER said it seemed very unsatisfactory that in the determina- tion of cupric reducing power the method of weighing as cupric oxide should still be indulged in. It was far more accurate, and was now almost universal-at any rate, amongst Continental chemists-to weigh as metallic copper. It made a great difference whether, in speaking of gallisin, the authors meant conversion products, or whether they meant the unfermentable residues of starch conversion.On degrading starch by means of malt-extract in the cold, a substance was obtained which was practically wholly fermentable; whereas, if the operation were conducted at a higher tempera- ture, conversion products were obtained which were not completely fermentable. Some of these unfermentable products had been examined by Mr. Ling and himself, and had been found to consist of bodies having the formula C12H22011. Their composition thus resembled that of maltose, and they were non-crystalline and had a fairly high reducing power. He was at present working, together with Mr. T. H. Pope, upon a series of polysaccharides, which occurred largely in the vegetable kingdom, and among which was probably the body mentioned by Mr. Boseley. They were non-crystalline, and yielded definite sugars on hydrolysis. He had recently isolated one of these bodies from the ivory nut, having the composition C6H1005, which on hydrolysis yielded considerable quantities of mannose, in addition to a hvo-rotatory sugar, probably Ia?vuIose, and which, while reducing Fehling's solution, decomposed at high temperatures, a peculiarity not possessed by the other members of the series which he had examined. Mr. ARCHBUTT recommended the method of estimating cuprous oxide recently described by Messrs. Caven and Hill before the Nottingham section of the Society of98 THE ANALYST. Chemical Industry,* in which the precipitate was filtered on an asbestos mat in a Gooch crucible, and transferred, after thorough washing with boiling distilled water, to a flask containing a mixture of dilute sulphuric acid and standard potassium per- manganate solution, the excess of permanganate being titrated with oxalic acid or hydrogen peroxide.

ISSN:0003-2654    

DOI:10.1039/AN9002500089

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年代:1900

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98 THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER 3 0 U RNALS. FOODS AND DRUGS ANALYSIS. The Determination of Cane-Sugar in Condensed Milk. L. Grunhut and S. H. R. Riiber. (Zed. Anal. Clzenz., 1900, xxxix., 19-36.)-This paper contains an account of the authors’ critical examination of various methods of estimating cane sugar in the presence of milk sugar. Of the methods based on reduction with Fehling’s solution before and after inversion, they regard those in which hydrochloric acid inversion is used as of chief importance in the analysis of condensed milk. They point out that, if a correct conclusion as to the amount of cane sugar is to be drawn from the increase in the reducing power after inversion, it is essential that the reductions before and after inversion must be made under exactly the same conditions, since every deviation, either in the concentration of the liquid or the length of time of heating, influences the amount of cuprous oxide deposited.The only gravimetric methods known to them which fulfil this condition are those of Ost (ANALYST, xx., 259) and of Kjeldahl (ANALYST, xx., 227), and the former of these has been shown both by Ost himself and by Schmoger to be unsuitable for the determination of milk sugar. Yavy’s volumetric method is not included in the investigation, since the readiness with which the ammoniacal solution undergoes alteration renders the results uncertain. In applying Kjeldahl’s method, however, in which a specially strong Fehling’s solution is used and the liquid boiled for twenty minutes, there is the probability of a, certain amount of decomposition of the cane sugar taking place, with the formation of decomposition products with strong reducing properties.G. Bruhns, in fact, has shown that this decomposition leads to considerable error (ANALYST, xxiii., 297). A second Eource of error in the copper reduction methods in the analysis of condensed milk is that in the direct reduction too great an amount of cuprous oxide is separated, with the result that the milk sugar is overestimated. The authors’ experiments show that the amount of copper reduced varies with the quantity of the milk taken. For example, a mixture of sixty parts of Passburg’s dry milk (contain- ing 21.38 per cent. of milk sugar) with forty parts of cane sugar yielded by direct * JOW.SOC. Chent. h d . , xvii. (1898), 124.THE ANALYST. 99 reduction in solutions of different degrees of concentration quantities of cuprous oxide corresponding to (1) 21-52 per cent. and (2) 23-20 per cent. of milk sugar. This error depends not only on the relative proportion of milk and cane sugar, since this was the same in the above experiments, but also on the absolute quantity of sugar. In the first case a large quantity of the sugar solution was taken, and the result was nearly correct, whilst in the second much less was used and the milk sugar was too high. The explanation given for this is that the milk sugar commences its reducing action as soon as the liquid begins to boil, and reduction is nearly completed before any decomposition of the cane sugar takes place and causes a secondary reduction.Thus, if there be much milk sugar present, so much of the copper solution is reduced that its subsequent action on the cane sugar is greatly weakened and the error will only be trifling. The action of the solution on the cane sugar is greatest when no milk sugar is present. When both cane and milk sugar are present, less cuprous oxide is deposited than corresponds to the sum of the amounts from the two reactions. Hence, the authors conclude that the only method of accurately estimating milk sugar in the presence of cane sugar by means of Fehling's solution is to construct an empirical table in which a correction is made for each absolute and relative amount of both sugars. Another inherent error in these reduction methods is that it is not correct to simply calculate the quantity of cane sugar from the difference between the amounts of copper reduced by the milk sugar before inversion, and by the milk sugar and the invert sugar after inversion.For example, in the case of the prepared condensed milk mentioned above, this difference for 0.375 gramme or" the mixture amounted to 0.26695 gramme of copper. This corresponded to 0-13517 gramme of invert sugar, or 34.24 per cent. of cane sugar, instead of the theoretical 40 per cent. Somewhat better, though still incorrect, results are obtained by calculating both amounts of copper into the corresponding quantities of invert sugar and taking the difference. In this way the cane sugar (40 per cent.) in the above mixture was found to be 38.64.This deviation is due, in the main, to the fact that the prcducts of the reduction of two sugars causing simultaneous reduction cannot be directly added together. Kjeldahl believed that he had discovered the law underlying this reaction (Zeit. nnal. Clzenz., xxxv., 347 and 646), and gave directions for its application to the determina- tion of two kinds of sugar. The authors, however, have been unable to obtain satis- factory results by using Kjeldahl's directions, and in the case of their prepared condensed milk found - 14.23 per cent. of milk sugar and + 62.81 per cent. of cane sugar. Summing up the results of their experiments on the reduction methods, they have arrived at the conclusion that it is not possible by their means to eftect an accurate determination of cane sugar in condensed milk.A second class of methods is based on the polarization of the solution before and after inversion, and the calculation of the cane sugar with the aid of the Clerget formula.100 THE ANALYST. In order to obtain correct results in this way, the authors adopt several precau- tions. By treating the condensed milk with boiling water and allowing the solution to cool, they state that the influence of the multirotation of the milk sugar is com- pletely obviated. They have not met with the difficulty experienced by Richmond and Boseley (ANALYST, xviii., 141 and 171), who found that the specific rotatory power of cane sugar was considerably altered by heating the solution at 100” C . I n making a correction for the volume of the casein and fat precipitated by means of lead acetate or of mercuric nitrate as proposed by Wiley, they make use of the method of double dilution (cf.ANALYST, xxi., 182). For the calculation of the results they have found Herzfeld’s modification of Clerget’s formula (Zeit. anal. Chem., xxxv., 717) more satisfactory than the original formula. Using the latter, they found 39-12 per cent. of cane sugar in their experimental mixture, whilst with the former they obtained 39.39 per cent. The empirical factor (0-962), which has been prescribed by the Budesrath for the correction of the volume, is objected to on the ground that it is only applicable to preparations of one particular chemical composition, so that when there is any considerable variation from that type the results are much less satisfactory.C. A. M. Gerber’s Process for the Estimation of Fat in Butter. J. Werder. (Chem. Zeit., 1899, xxiii., 1028.)-As originally devised, this process did not give trustworthy results, but it has recently been improved, and is now fit to rank as a regular laboratory method. In a small capsule, which forms the stopper of a specially graduated tube, 5 grammes of the well-mixed sample are weighed out ; it is then put in position, and the tube is filled with 1 C.C. of amylic alcohol and 20 C.C. of sulphuric acid (specific gravity 1.50). After agitation and separation the volume of fat is read off. Double tests carried out on twelve samples of market butter showed maximum differences one from another of 042 per cent., and the mean figures, in comparison with those given by the Soxhlet process, showed maximum differences of +Om30 and - 0.45 per cent., or an average difference of ~ 0 .2 7 per cent. Applied to two remelted butters, the yields were between 99-6 and 100.1 per cent. F. H. L. Contribution to our Knowledge of the Composition of Hens’ Eggs. A. Juckenack. (Zeit. fiir Untersuch. der Nahy. und Genussmittel, ii., 1899, 905.)- On incinerating yolk of egg as a preliminary to the determination of the inorganic constituents, a portion of the phosphoric acid becomes reduced to phosphorus, and is therefore lost, owing to the bases being in insufficient proportion to form metaphos- phates. The difficulty may, however, be overcome by the addition of alkaline carbonate and nitrate before incinerating.In white of egg, and in the combined white and yolk, mixed in the proportion in which they occur in whole eggs, the bases are present in excess, and correct results are consequently obtainable without such addition.THE ANALYST. 101 The following results are given : I. Yolk ... ... ... ... 1,279 per cent. phosphoric acid, 11. White ... ... ... ... 0.031 7 7 9 , (a) By direct determination ... 0.443 9 9 ), (b) By calculation from I. and 11. 0.455 ,> I , 111. Whole eggs : one egg (16 grammes yolk and IV. Average phosphoric acid contents of 31 grammes white.) Table showing the Various Conzbi.lzatioizs and Proportions iiz which the Phosphoric Acid exists in Yolk of Egg. Total phosphoric acid in 100 grammes, 1.279 grammes. . -- I\-_ \ Soluble in boiling alcohol, 0.823 grm.= Insoluble in boiling alcohol, 0.456 gramme. 9.35 gramme distearylleci t hin. A . Extractable direct by Dissolved by alcohol As ' nuclein, As insoluble phos- ether from the yolk, after extraction by 0.178 grm. phate or com- 0.478 gramme = 5-42 ether, 0.345 gramme pounds of phos- grammes f r e e di- =3*93 gramme di- phoglyceric acid, stearyllecithin. stearyllecithin com- 0.278 gramme. bined with vitellin. The cholesterin in yolk of egg was also determined, the result showing 0.91 per cent., corresponding to 1.92 per cent. in the dry substance. H. H. B. S. The Reliability of the Glycerin titration Method for the Determination of Boric Acid in Preserved Meats, and the Separation of Boric Acid from Borax. A. Beythien and H. Hempel. (Zeit. fiiv Untersuch.der Nahr. uizd GenzLssniittel, ii., 1899, 842-851.)-The authors have carried out experiments to test the accuracy of the glycerin titration method, which depends upon the fact that if a solution of boric acid be neutralized, using methyl orange as indicator, and then glycerin added, the solution reacquires an acid character, and can be again titrated with alkali, phenolphthalein being used as indicator. The authors followed in general the directions given by Jorgensen. The results affirmed the reliability of the process, and showed in particular that no appreciable loss takes place, either when the acidified boric acid solution is heated, or when the alkaline residue left after evaporation is ignited. The maximum loss in the experiments amounted to 1.66 per cent.of the quantity taken. The authors also tested the process in its application to the examination of preserved meats. Weighed portions of chopped beef were mixed with measured quantities of solutions of boric acid of known strength. After the addition of water, solution of soda was added until a decided alkaline reaction was produced. The mixture was then warmed 'for several hours and filtered. This procedure was carried out three times, after which the various filtrates were mixed together and evaporated to dryness. The residue was then incinerated, the ash taken up with sulphuric acid, the solution gently heated to expel carbonic acid, cooled and102 TEE ANALYST. neutralized. with standard soda. the boric acid taken. Twenty-five C.C. of glycerin mere then added, and the mixture tjtrated The greatest differences were: -5.06 and + l o 6 7 per cent of Aspirin. F. Goldman. (D. Pharm. Ges. Ber., 1899, ix., 232; through Clzam. Zeit. Rep., 1899, 340.)-Aspirin is a product of the action of acetic acid upon salicylic acid, its formula being C,H,(O.COCH,)COOH. When 0.5 gramme is boiled with 10 C.C. of a 10 per cent. solution of sodium hydroxide, a clear liquid should result, in which an excess of dilute sulphuric acid produces a temporary violet colour, and precipitates the salicylic acid, which can be filtered off and identified by its melting-point and its reaction with ferric chloride. The filtrate from the salicylic acid has an odour of acetic acid, and on boiling with alcohol and sulphuric acid gives that of acetic ether. Aspirin should not contain any free salicylic acid ; to detect it, 0.1 gramme is dissolved in 5 C.C. of alcohol, diluted with 20 C.C. of water, and 1 drop of ferric chloride solution is added; no violet colour should appear. F. 13. L. Its melting-point is 135" C.

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DOI:10.1039/AN9002500098

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年代:1900

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102 TEE ANALYST. ORGANIC ANALYSIS. Estimation of Benzene Vapour in Illuminating Gas. 0. Pfeiffer. ( J . Gasbeleuclzt, 1899, xlii., 697 ; through Clzem. Zeit. Rep., 1899, 333.)-The author suggests a modification of Harbeck and Lunge’s nitration process ( A 4 ~ ~ ~ ~ ~ 1898, xxiii., 101) which makes it far more simple to carry out. The gas is measured and nitrated in a large separating funnel holding 3 or 4 litres; it is filled through the stopper-hole by displacement, and 10 C.C. of the mixed nitrating acids are introduced through the ordinary exit tube.* The acids are made to spread over the internal surface, and are allowed to act for an hour, when the whole of the benzene will be absorbed. The vessel is then rinsed out with 100 C.C. of water, which is brought into a small separating funnel, and neutralised with crystallised sodium hydroxide (40 grammes).It is extracted two or three times for five minutes with quantities of 50 C.C. of ether, each of which is afterwards washed two or three times with 10 C.C. of water to remove some brown substance. The solvent is finally evaporated, the residue taken up in a little anhydrous ether, filtered through freshly calcined sodium carbonate into an evaporating basin, and dried over sulphuric acid--it should neither be warmed nor placed in vacuo. To convert the weight (9) of dinitrobenzene into the percentage by volume of benzene vapour, the author gives the following simplified formula; C is the capacity of the measuring vessel, t the temperature, and b the height of the barometer : 36080 273+t c x g x b .Having a, complete analysis of the gas, and knowing its specific gravity, it is Calling the specific gravity of also possible to calculate the proportion of benzene. * The stopcocks should be L b lubricated ” with strong sulphuric acid.THE ANALYST. 103 the gas S, the specific gravity of the 6 t heavy hydrocarbons" (C,H,) s, and the total volume of the latter ZJ, we have : s = 100s - (CO x 0.9621 + CH, x 0.5530 + H x 0,0692 + N x 0-9701 + CO, x 1.5197--- -- C*,Hll, ' > whence the percentage by volume of benzene vapour becomes : ( s - 0.9674)~ _____ 1.7367 As an example of this method, the author quotes a sample of gas in which the proportion of benzene mas calculated to be 1.57 per cent., and that of ethylene 1.83 per cent. ; by direct analysis the benzene was returned at 1-52 per cent., and the ethylene 1.88 per cent.F. H. L. The Volumetric Estimation of Quinones of the Benzene Series. A. Valeur. BUZZ. SOC. Chim., 1900, xxiii., 58-61.)-This method is based on the reduction of the quinones by hydriodic acid.* When the latter is replaced by an equivalent quantity of hydrochloric acid and potassium iodide, the reaction takes place in accordance with the equation : In the determination a quantity of the pure dry quinone, sufficient to liberate from 0.20 to 0-50 gramme of iodine is dissolved in a little 95 per cent. alcohol. To this solution is added a rapidly-prepared mixture of 20 C.C. of a 10 per cent. solution of potassium iodide with 20 C.C. of concentrated hydrochloric acid previously diluted with an equal volume of 95 per cent.alcohol and cooled. The liberated iodine is titrated with standard thiosulphate, and the corresponding amount of quinone calculated. C,'H,O, + 2HC1+ 2KI = C,H,O, + 2KC1 +I,. The following results show the accuracy of the method : Tolucjuinone, Thymoquinone, C,H,( CH,) (C,H,)O,. C,H,(CH3)0,. I. 11. I. 11. --- -- /-- - ,.--, Weight of substance, gramme 0.2057 0-2707 0.2130 0.1663 Iodine per cent. . . . ... 208.5 207.9 155.4 154-7 (Theory 208.2) (Theory 154.8) Iodine liberated I 9 0.4290 0.5629 0.3311 0.2574 I t is necessary to mix the hydrochloric acid and the potassium iodide, and not to add them separately to the quinone, since the acid would immediately react on the quinone, and the iodide would cause partial oxidation.This method appears to be applicable to the majority of true quinones. I t can be used to determine their solubility in different solvents, which is not easily determined by other methods, on account of the volatility of the quinones and the difficulty of drying them without loss. It can also be employed €or the determination of quinones in somewhat unstable combinations, such as the phenoquinones and quinhydrones. In the case of * Reduction with HI yields a mixture of hydroquinone and quinhydrone ; from what is stated in the paper it appears that with KI and HC1 the reduction is carried o step further, and gives only hydro- quinone.104 THE ANALYST. ordinary quinhydrone the following percentages of iodine were obtained : 116.6,116*3 and 116.1, whilst the calculated percentage for C,H,O;CGHGO, is 116.5.The author therefore concludes that this compound, contrary to the view of Wichelhaus, results from the union of equal molecules of quinone and hydroquinone. C. A. M. The Properties of the Oils of Lemon, Bergamot, and Orange. A. Soldaini and E. Berth. (Boll. chim. farm., 1899, xxxviii., 537; through Chew. Zeit. Rep., 1899, 323.)-Some constants of these three oils in the pure state are given in the annexed table : Lenion. Bergamot . Orange. Specific gravity at 15' ... ... . . . 0.854-0.860 0.882-0.886 0*847-0+353 Rotatory power at 20" (100 millimetres tube) 56-66' 8-20" 96-98" Boiling-point at ordinary pressure . . . ... 171-172" - 173-174" Lemon Oil.-In lemon oil the proportion of citral should not be below 6.5 per cent.; and when 20 grammes are fractioned at a pressure of 20 to 30 miilimetres, the first 10 C.C. of the distillate should have as high a rotatory power as the original oil. The presence of orange oil is shown (a) by a yellow colour when a drop of the sample is mixed with 15 or 20 drops of brominated chloreform, ( b ) by a yellow flocculent precipitate instead of a white crystalline one when sodium bisulphite solution is added. To determine the percentage of citral, a 5 C.C. pipette graduated in fortieths is required, and also a pear-shaped flask, the neck of which has the same diameter as the pipette, and which has a lateral tube bent upwards at a right angle to carry a funnel. Five C.C. of the sample are run from the pipette into the flask, 25 C.C. of a solution of potassium bisulphite containing an excess of sulphur dioxide are introduced, the lower end of the pipette is connected to the neck, the whole is shaken and warmed for twenty minutes on the water-bath, then cooled and warmed again for five minutes.When finally cold, the volume of oil still remaining liquid is read off in the pipette by adding water through the side funnel ; and the difference between it and the 5 C.C. taken represents the volume of the aldehyde. Bergamot Oil.-The proportion of linalyl acetate usually varies between 21 and 22 per cent. When 15 C.C. are fractioned at the above pressure, the first 5 C.C. of the distillate should have a rotatory power 2$ times as great as the oil itself; and the next 9.5 C.C. should be almost inactive. Evaporated on the water-bath, the residue should be between 5 and 6 per cent.The oil should be soluble in ij vol. of 90 per cent. alcohol, and the clear solution shouldnot be rendered turbid on dilution. SchiiY's reagent for aldehydes should fail, or at most give a faint tint in half an hour ; an immediate colour, or a strong red in half an hour, indicates lemon oil. To estimate the linalyl acetate, 1.5 grammes are saponified with an excess of seminormal alcoholic potash, diluted with a little 80 per cent. spirit, and titrated with semi- normal sulphuric acid and phenolphthalein ; the volume of alkali multiplied by 0.09775 (mol: wt. of the ester, 195.5) gives the acetate. OrcLnge Oil.-When 20 C.C. are fractioned at a pressure of 10 or 20 rnillimetres, the distillate should have a rotatory power from I" to 3" higher than the original. Schiffs reagent should give no colour.F. H. L.THE ANALYST. 105 Determination of the Solidifying-point of Fatty Acids. I. Freundlich. (Chem. Zeit , 1899, xxiii., 1014.)-The ordinary Dalican process for determining the exact solidifying-point of fatty acids is not quite accurate, for the temperature to which the thermometer finally rises is partly dependent on that to which it was made to fall during the stirring of the fat. The following modified way of carrying it out leads to absolutely concordant results, or at the worst to differences of 0.05 to 0.1" C. At the lowest temperature above the expected solidifying-point at which the sample round the thermometer bulb remains perfectly liquid, the thermometer is moved quickly two or three times backwards and forwards through the fat, and the mercury is observed ; if it falls sharply, the operation is repeated until the column remains constant for thirty or forty seconds; then the sample is stirred fifteen or twenty-five times, and if the mercury falls during the agitation and risee immediately afterwards to a maximum s t which it stands unchanged for three or five minutes, that maximum is the true solidifying-point.The great thing to avoid is too prolonged stirring. F. H. L. The Becchi and Halphen Colour Reactions for Cotton Oil. P. N. Raikow and N. Tscherweniwanow. (Chem. Zed., 1899, xxiii., 1025.)-At the present time there exist some ten different modifications of the Becchi test for cotton oil ; and statements as to its utility and the best proportions for its several ingredients vary enormously.Benedikt and other authorities question whether cotton oils do not occur which cause no reduction of the silver nitrate at all; this, however, seems problematical, unless the samples have been specially treated in order to prevent their giving the Becchi reaction. I t is not possible to render cotton oil indifferent to the Becchi test by blowing air through it in the cold; nor can the same object be attained by repeated extractions with alcohol, the latter fact being in contradiction to Benedikt's assertion that the true cause of the reaction is an aldehyde-like body which is readily soluble in spirit. Even the fatty acids of cotton oil after alcoholic saponification and liberation from their barium salts, or after aqueous saponification and liberation from the sodium salts, give the test, while the small proportion of unsaponifiable matter in the original oil does not give it.Treated with ordinary steam even for long periods of time, cotton oil still retains its usual properties ; but superheated steam, or a simple heating of the oil to between 210" and 220°, quickly destroys its reducing power, which also vanishes more slowly at 150", the residual material being almost unaltered, except that its colour is slightly darkened, and that it possesses a faint burnt odour. Precisely the same remarks apply to the Halphen test : one hour at 150" hardly affects the reaction, five hours reduce its intensity to one-half, ten hours to one-third ; in time, probably, it would fail altogether.[Cf. Holde and Pelgry, ANALYST, 1899, xxiv., 214.1 After elaborate experiments, the authors find that the details of the Becchi test are most important : the proportion of silver nitrate to the oil, the proportion of free acid to the silver, ought to be kept uniform ; and they decide that the method adopted by the Italian Commission (cj. ANALYST, 1895, xx., 222, last paragraph) should be taken as the standard. The latest modification of the Becchi test described by106 THE ANALYST. Tortelli and Ruggeri (ANALYST, 1898, xxiii., 179) was not examined; in comparison with the more certain and very delicate Halphen reaction, it is too complicated to be generally useful. I t appears to be universally admitted that the Halphen reaction (ANALYST, 1897, xxii., 326 ; 1898, xxiii., 131) is better than Becchi’s ; the only points of divergence are its degree of delicacy and the best method of carrying it out.The actual temperature employed is only a matter of convenience; a cherry-red colour is pro- duced in the cold by bright sunlight in three hours. The part played by the amylic alcohol is obscure, but it does not serve simply to retain the carbon disulphide in the hot liquid; it should, therefore, not be omitted. A faint Halphen red is manifested when the free sulphur is left out of the regular mixture; an excess of sulphur is use- less, and in the testing of oils containing only a little cotton oil, it tends to decrease the delicacy of the reaction. The present authors accordingly reject Soltsien’s proposals ; there is no objection to the use of plain water instead of the brine bath, but in other respects Halphen’s prescription should be retained in its integrity.The behaviour of olive, been studied under bath nor in sunlight oil can be readily sensitiveness. walnut, linseed, poppy, and arachis oils towards the test has various conditions ; neither by prolonged heating on the water- did they respond. I n pale-coloured oils 0.5 per cent. of cotton detected, and this proportion may be taken as its limit of F. H. L. The Determination of the Bromine Absorption of Oils. P. C. McIlhiney. (Journ. Amer. Chem. SOC., 1899, xxi., 1084-1089.)-1n a former communication (ANALYST, xix., 141) the author described a process for the determination of this con- stant in which a distinction was made between the bromine addition and bromine substitution values.He has now simplified his process by making use of the iodometric method of Schweitzer and Lungwitz (Journ. SOC. Chem. Ind, 1895, 130), and shortening the time in accordance with the fact that the addition of bromine to fats is practically instantaneous (ANALYST, xx., 146). I n the modified process a weighed quantity of the oil is dissolved in 10 C.C. of carbon tetrachloride in a stoppered bottle and 20 C.C. of one-third normal bromine in carbon tetrachloride added. Simultaneously a blank determination is made, and subsequently titrated with standard thiosulphate to determine the strength of the bromine solution. After the lapse of one or two minutes, 20 to 30 C.C.of a 10 per cent. solution of potassium iodide are introduced, the bottle shaken to insure the absorption of the bromine and hydrobromic acid, and the iodine titrated with deci- normal t hiosulphat e. After the titration, 5 C.C. of a neutral 2 per cent. solution of potassium iodate are introduced, and the amount of iodine liberated, which is equivaleut to the hydro- bromic acid formed, is titrated, and gives the bromine substitution figure. In order to prevent a loss of bromine or hydrobromic acid on removing the stopper to introduce the potassium iodide, a piece of wide indiarubber tubing is slipped over the neck of the bottle, thus forming a well round the stopper. TheTHE ANALYST. 107 potassium iodide is poured into this well and the stopper slightly opened, preferably after the bottle has been cooled in ice to create a partial vacuum in the interior.The following figures were thus obtained with various representative oils. The difference between the figures given in the last column and 1.000 are intended to represent the degree of substitution which occurred in the determination of the Hub1 value : I HUN l Value. - _ - - Raw linseed oil, several years old ,? ,, ,, average of seven samples ... ... ... Boiled linseed oil, average of eight samples ... .., ... Third run rosin oil ... ... ‘‘ Java” boiled rosin oil ... ... Menhaden oil, average of three samoles ... .._ . _ . 157.3 183.8 - 63.9 73.3 174.9 Maize oit average of three samples- I - Cotton-seed oil ”.. ... - Turpentine ... ... ... ... - Ceylon cocoanut oil ... - Tallow rendered in laboratory ... - Hard paraffin ... ... Black rosin ... ... ... -- ... ... ... - Bromine I I I 99.1 99.2 115.7 1 112.0 46.2 ~ 101.9 110.2 I 110.6 - 75.8 - I 65.8 - 1 266.1 - 5-36 - 1 24.0 - , 3.55 I 135.4 92.0 106.6 103.0 7.7 8.3 95.6 72.9 3.6 2.7 3.2 42.3 46.8 7.5 1-5 62.2 1.8 166.1 50.0 4.7 0.33 21.481 1.26 1 -06 65.0 Calcu- lated Bromine Value divided Bromine Addition Valne. 1.077 1.083 bY ___-- - 5.231 5-685 1.154 - - - - - - - The advantages claimed for this method are that the bromine solution is readily pre- pared and does not change on keeping, that it is exceedingly rapid, and that it dis- tinguishes between the halogen absorbed by addition and by substitution. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9002500102

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

THE ANALYST. 107 I N O R G A N I C A N A L Y S I S . Bromine and Alkali Hydroxides as a Test for Copper. D. Vitali. (Boll. Chin2. Farm., 1899, xxxviii., 665; through Chem. Zeit. Rep., 1899, 349.)-It is well known that when a solution of copper sulphate is mixed with potassium or sodium hydroxide, and an excess of bromine water is added, the original blue precipitate soon becomes black. This substance consists of copper dioxide; it evolves oxygen on warming or on treatment with sulphuric acid, and it gives off chlorine with hydro- chloric acid. The reactions proceed thus : CuSO, + 2NaOH = Cu(OH), + Na,SO,. 2NaOH + Br, = NaBr + NaBrO + 8,O. Cu(OH), + NaBrO = CuO, + H,O + NaBr.108 THE ANALYST. Other oxidizing agents, such as hydrogen peroxide or manganese dioxide, also convert copper hydroxide into dioxide.By evaporating 1 C.C. of a eolution containing copper to dryness, treating the residue with the yellow mixture of alkali and bromine, a black precipitate will be produced if the proportion of copper was 1 : 100,000. If the residue is more simply moistened with saturated bromine water and again dried, a black deposit is obtained, consisting of CuBr,, which becomes blue on being touched with water. This test will show copper in 1 C.C. of a 1 : 1,000,000 solution, and it is therefore more sensitive than sulphuretted hydrogen or potassium ferrocyanide. The black bromide is rendered more visible when moistened with strong sulphuric acid. Other metallic salts yield black precipitates with alkali hydroxides and bromine, e.g., Co,(OH),, Ni,(OH),, MnO,H,O.Mercurous salts give a yellow precipitate of mercuric oxide. Bismuth salts give a reddish-brown precipitate of Bi,O,. Lead salts in the cold finally yield an orange-yellow precipitate of lead oxybromide, which changes into peroxide on warming. F. H. L. The Separation of Tungsten and Molybdenum. F. Ibbotson and H. Brearley. (Chem. News, lxxxi., 13-15.)-Two modes of procedure are recommended : (a) The tungsten and molybdenum are precipitated together by lead acetate, the precipitate washed slightly with hot, very dilute acetic acid and ignited. The ignited precipitate is then dissolved in concentrated hydrochloric acid, using about as many C.C. of acid as there are centigrammes of the lead salts. Two or three times the bulk of boiling water is then added, the solution boiled, allowed to settle, filtered by decantatiou through a small pulp filter, the precipitate redissolved in about half the quantity of acid previously used, reprecipitated with water, and filtered through the same pulp.The molybdenum is determined in the filtrate as PbMoO,. The greater the amount of acid used to dissolve the lead salts, the more water is required for the complete precipitation of the tungstic acid, and the greater the dilution, the greater the liability to contamination with rnolybdic acid. ( b ) When the quantity of tungsten is small in comparison with that of the molybdenum, the former is not completely precipitated. Under these circumstances the following procedure is recommended : A few drops of nitric acid are added to the hydrochloric acid solution of the lead salts, which is then evaporated to a pasty con- sistence.The mass is diluted with 200 to 300 C.C. of dilute hydrochloric acid (1 : 3), the solution boiled, and the tungstic acid filtered off. The precipitate adhering to the sides of the vessel can be removed by dissolving in a few drops of dilute ammonia, which may then be absorbed with a piece of filter-paper, and the latter ignited with the precipitate. H. H. B. S. Estimation of Tellurium Dioxide in Presence of Haloid Salts. F. A. Gooch and C. A. Peters. (Zeits. ayzorg. Chem., 1899, xxi., 405.)-Brauner has shown ( J . Chem. SOC. Trans., 1891, 238) that tellurous acid cannot be determined by oxidation with permanganate if it be dissolved in hydrochloric acid; and he has also stated that if the oxidation take place in sulphuric acid solution a small correction isTHE ANALYST, 109 necessary, which is not required when the oxide is dissolved in alkali.If, therefore, the tellurous acid is dissolved in sodium hydroxide, and if the final titration between the oxalic acid and permanganate is carried out under those conditions which are desirable to avoid the interfering action of hydrochloric acid-Le., presence of manganous chloride-tellurium dioxide can be accurately determined in the manner indicated, even if it be accompanied by chlorides. About 0.1 gramme of TeO, is dissolved in a little sodium hydroxide, and mixed with permanganate solution (standardized on ammonium oxalate) till it remains pink; the liquid is heated, and 5 C.C.more of 1 : 1 sulphuric acid than are needed to neutralize it are added ; excess of standard ammonium oxalate is introduced to destroy the higher oxides of man- ganese and the excess of permanganate ; and finally the excess of oxalate is titrated with permanganate. If the proportion of hydrochloric acid is quite small, e.g., such as is produced by the decomposition of the original tellurium chloride, addition of manganous chloride is not necessary; but it is better always to employ it (0.5 to 1 gramme), as the last titration can then be conducted in the cold. I n the presence of a bromide fairly satisfactory results can be obtained, provided that the excess of sulphuric acid is not greater than 5 C.C. of a 12-5 per cent. acid, that sufficient manganous chloride (0.5 to 1 gramme) is used, and that the liquid is titrated at ordinary temperatures.Themethod described by Norris and Fay (ANALYST, 1898, xxiii., 249) gives excellent results. Instead, however, of titrating the iodine liberated from the iodide and sulphuric acid by means of thiosulphate, it can be determined with decinormal arsenious acid, this modification possessing the advantage that the arsenic serves also to standardize the original permanganate used to oxidize the tellurium dioxide. About 0.5 or 1 gramme of potassium iodide dissolved in 100 C.C. of water is added to the alkaline solution of the tellurium, then standard permanganate is run in till the green colour disappears (about 30 C.C. of the decinormal liquid per 0.1 gramme of TeO,); next a few C.C.of sulphuric acid are added to clarify the liquid, and the free iodine is titrated in presence of potassium bicarbonate. I t is important to have a sufficient excess of iodide, and it is perhaps better to run in some of the arsenious acid before acidifying with sulphuric acid. All the examples quoted by the authors are reasonably satisfactory, and they agree closely with theory when the atomic weight of tellurium is taken at 127. F. E. L, The process is obviously not available in the presence of an iodide. Determination of Sulphur in Bitumens. S. F. and H. E. Peckham. (Journ. Amer. Chem Xoc., vol, xxi. [9], pp. 772.)-The authors have modified their deflagra- tion method by taking such an amount of the assay as will correspond to about (3.2 gramme of bitumen, and mixing it with 15 grammes each of pure, dry sodium carbonate and potassium nitrate, the mixture being then deflagrated in small suc- cessive portions in a %ounce platinum crucible at dull red heat. No blast lamp is necessary, the fusion being complete without ; the excess of flux reduces the violence of the operation and the risk of loss by spattering. The mass is dissolved by immersing the crucible in water over night, and the silica, iron, alumina and sulphuric acid determined in the solution in the usual manner. c. s.

ISSN:0003-2654    

DOI:10.1039/AN9002500107

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

110 THE ANALYST. R E V I E W S . DETERMINATION OF RADICLES IN CARBON COMPOUNDS. By Dr. H. MEYER (Prague). Authorized translation, by Dr. 5. BISHOP TINGLE (Chicago). New York: J. TViley and Sons ; London : Chapman and Hall, 1899. This small book is a valuable addition to literature, containing as it does witbin the limits of 120 pages much useful information and many valuable hints. Its scope is broader than might be inferred from the title; it really deals with the principles of methods for the proximate analysis of organic compounds. Although it might appear at first sight to appeal more particularly to the investigator in organic chemistry than to the technical analyst, it must not be forgotten that the problems with which both are confronted very frequently differ only in the form in which they are presented.Methods which depend on the determination of certain atomic groups and radicles find in point of fact frequent application alike in purely scientific investigations and in the technical analysis of organic products. Some of these have, in their technical application, become quite stereotyped, and are perhaps too often used by analysts without regard to the scientific principles on which they are based. acetyl value,” ‘‘ iodine value,” convenient though they may be, are doubtless largely responsible for this, yet the analyst should in all cases consider what he is actually measuring. Thus, that the acetyl value is a measure of displaceable hydrogen in the groups - OH, = NH, etc., and that the iodine value indicates the presence of unsaturated compounds.To briefly summarize the contents of the book, it describes methods for the determination of the following groups : - OH, - OCH,, - OC,H,, - COOH, = CO, - NH,: - CN, - CONK,, = NH, = NCH,, the diazo, hydrazine, iodoso, iodoxy, and peroxide groups. Instructions are also given for the determination of the IC iodine value.” Methods for the determination of the basicity of acids, and for the introduction of acid radicles, notably acetyl and benzoyl, and of alkyl groups are fully described, and wherever chemicals rarely met with in laboratory practice are referred to, details for their preparation are given. The arrangement of the matter and the style of writing are all that could be desired, and the numerous references to original papers cannot but add to the utility of the book.The only typographical error noticed is on page 41, where the group carboxyl is represented as CHOR instead of COOH. Price 4s. 6d. The use of such terins as A. R. L. DAIRY CHEMISTRY: A PRACTICAL HANDBOOK FOR DAIRY CHEMISTS, ETC. By H. D. RICHMOND, F.I.C. London : Charles Griffin and Co., Limited. Price 16s. If the question were raised as to the necessity for a work specially treating on the chemistry of milk, it should certainly be answered in the affirmative. Not only is the public analyst called upon to examine large numbers of samples of milk and milk products with the object of detecting and checking adulteration, but other chemists are also frequently called upon to analyse and pass opinions on materials directly or indirectly connected with the dairy, and last, but not least, practical dairy work nowadays demands a considerable amount of scientific knowledge if itTHE ANALYST. 111 is to be performed in a satisfactory and successful manner.The days are gone for ever in which a very limited amount of experience was considered either sufficient to judge whether a milk was pure or sophisticated, or to support and aid the practical dairyman with scientific counsel, or to fill up a responsible position in the dairy industry. If, then, a work on dairy chemistry must be considered highly desirable-nay, necessary-nobody could be better fit for producing such a, work than the author of the book lying before us. Mr. Richmond has for nearly eight years superintended the Aylesbury Dairy Company’s laboratory, which was erected in the year 1880.Although established to serve the special requirements of that large firm in exercising an extended and minute control over the milk and milk products there dealt with, Mr. Richmond, like his predecessor, has not confined himself to exercising control alone, but has taken good care to make extensive use of the oppor- tunities given to work out as many questions as possible which in one way or another are connected with the chemistry of milk, milk products and dairy work generally. In the course of twenty years a vast amount of facts and experiences has been thus accumulated, which in itself would have been quite sufficient to form a valuable publication. By collating and studying the respective publications of others, and reproducing them in a digested form, he has succeeded in putting before the reader a complete work on dairy chemistry.I t would take up far too much space merely to indicate the contents of the various chapters of the book, to draw attention to the useful tables, and to enumerate the numerous illustrations. Less still could justice be done to Mr. Richmond’s work by an attempt to specially mention the most important parts and statements. I n fairness we must also abstain from noticing the weaker portions of the book, and as these are scant and of little importance we can do so without remorse. Suffice it to say that Richmond’s ‘‘ Dairy Chemistry ” forms a complete r6sum6 of theoretical and practical knowledge, written in easily intelligible language, and is a work useful to everyone desiring instruction in the chemistry of milk and milk products, a work which the A TEXT-BOOK OF PHPSI& CHE~VIISTRP.But the author has done much more. attentive reader will study with the greatest satisfaction. P. v. By Dr. R. A. LEHFELDT. London : Edward This branch of general chemistry has developed so enormously during the past twelve years or so that it now constitutes a department of considerable size and importance ; and as its teachings already to some extent exert on analytical problems an influence which in all probability will become more marked as time rolls on, it behoves every analytical chemist to become acquainted with the general principles of this subject, especially as analytical processes depend ultimately on a knowledge, not only of chemistry in the restricted sense, but of the physical behaviour of the materials dealt with. The work before us is eminently adapted for this purpose ; it forms a well-written digest, couched in terse but intelligible language. Although mathematical formulz are indispensable in illustrating a subject of this nature, the work is ingeniously arranged so as to be intelligible to the non-mathematical reader who is content to take the mathematical proofs on trust. The general get-up of the book is good; it is printed in clear, bold type, contains numerous illustrations and has a copious index. Arnold. Price 7s. Gd. W. J. S.

ISSN:0003-2654    

DOI:10.1039/AN9002500110

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

112 THE ANALYST, MISCELLANEOUS. QUALIFICATIONS OF PUBLIC ANALYST. THE following extracts are taken from an Order and accompanying Circular, dated March 7,1900, issued by the Local Government Board to those local authorities who are required by law to appoint a Public Analyst : “ Every person appointed on or after the first day of January, one thousand nine hundred, to the office of Public Analyst shall furnish such proof as we may deem sufficient of his competent skill in, and knowledge of, (a) analytical chemistry, ( b ) therapeutics, and (c) microscopy. “ Such proof shall in every case comprise documentary evidence that such person holds the requisite certificate, diploma, license, or document conferring the qualification, or attesting his possession of the skill or knowledge to which the same applies, and granted or issued by any person or body of persons for the time being recognised by us as conipetent to confer such qualification, or to test such skill or knowledge.Such proof shall also comprise such further evidence as we may in any particular case require. ‘‘ All such documentary evidence as is hereinbefore mentioned shall be furnished by such person to the local authority by whom he is appointed, and shall be transmitted to us by the local authority when applying for our approval of the appointment. “Provided that nothing in this regulation contained shall, in the case of any person who was appointed to the office of Public Analyst with our approval, between the first day of January, one thousand eight hundred and ninety-one, and the date hereof, or of any person who is so appointed for the first time after such last- mentioned date, apply upon any subsequent appointment of such person to the said office.” (‘ AS regards the reference in the Order to a person or body of persons whom the Board may from time to time recognise as competent to confer the requisite qualifica- tion, or t o test the skill or knowledge of which proof is required by the Order, the Board may state that it would accord with their existing practice to accept as sufficient documentary evidence of the requisite qualification under the Acts the Diploma of Fellowship or Associateship of the Institute of Chemistry of Great Britain and Ireland, together with the Certificate grantcd by the Institute after an examination, conducted by them on lines approved by the Board, in therapeutics, pharmacology, and microscopy.” ‘‘ The possession of a diploma as a registered medical practitioner is accepted as sufficient proof of competency in microscopy and therapeutics, and it would only be necessary that a medical practitioner appointed as a public analyst should furnish evidence of competent skill in, and knowledge of, analytical chemistry.” ‘( Evidence of skill or knowledge on the part of a candidate in respect of any of the qualifications referred to as requisite, which is tendered by an individual, must be from a person recognised as entitled to speak with authority as to proficiency in -the parbicular qualification in question.”

ISSN:0003-2654    

DOI:10.1039/AN9002500112

出版商:RSC    

年代:1900

数据来源: RSC