摘要:

THE ANALYST. DECEMBER, 1891, PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. A MEETING of the Society of Public Analysts was held on the 4th November, 1891, the President being in the chair. The minutes of the last meeting having been read and confirmed, Mr. Edgar B, Kenrick, of Winnipeg, Manitoba, was elected a member of the Society, The following gentlemen were duly proposed :- As member :-Dr. W. R. Smith, Public Analyst for Woolwich and Plumstead. As associate :-Mr. E. H. Roberts, Assistant to Mr. Bernard Dyer, The Secretary then read the following paper:- NOTE ON TABARIE’S PROCESS FOR THE INDIRECT DETERMINATION OF ALCOHOL. BY THOMAS P. BLUNT, M.A. I HAVE used Tabarie’s method for several years w a check upon the distillation process in the analysis of wines and beers, and have found the results approximate very closely.Allen describes the process in his Commercial Organic Analysis, volume I, page 71, and makes the observation that ( 4 When beer or wine is examined by this method, the estima- tion of alcohol has a tendincy to be too low,” This is perfectly true when the usual formula is employed in the calculation, but it appears to be the formula, and not the process, which is principally at fault. The rule given is to divide the specZc gravity of the original liquid (8) by that of the (‘extract” (s’), the assumption being that the difference between these two gravities is proportional to that between 1, the gra~rity of water, and the required gravity of the alcohol distilled away, Let us examine this assumption and see how far it tallies with the facts.A given measure of an alcoholic liquid containing a fixed extractive, of which the gravity is known, is boiled until the whole of the alcohol is driven off; it is then made up fo the original volume with distilled water, and the gravity again taken ; it is clear that we have in the first case a certain quantity of fixed matter dissolved in a given bulk of dilute alcohol, in the second the same quantity of fixed matter dissolved in the same bulk of water ; it would seem, therefore, that the difference between the two gravities should222 THE ANALYST. be identical with, not proportional to, the difference between 1 and the required gravity, and this would be correctly represented by the formula 1 - (s‘- 8). The amended formula has the advantage not only of superior accuracy, but also of demanding much simpler arithmetical work than the old one.Where the gravities concerned lie near to unity, the difference between the results given by the two formulz is unimportant, but where liquids of high gravity are under examination, such as sweet wines and liqueurs, the error may become serious. The following practical example will illustrate this: nine volumes of weak syrup were mixed with one volume of ordinary rectified spirit ; the gravity of the mixture was 1.1228 (8). A measured quantity was distilled with the proper precautions, and the distillate made up to bulk a t the same temperature; the gravity was 0.988. The residue in the retort was now made up to bulk as usual, and the gravity taken.1.1228 It was 1.1343 (s’), then - - ($) = 0.9899 ; and 1-(1°1343-1~1228)=(l-(s’-s)) = 0.9885. It will be seen that there is still a deficiency in indicated spirit-strength, and this is greater than I have usually met with in practice. I believe it t o be due to the difficulty of concentrating a syrupy liquid without some slight decomposition; the residue in the retort was in fact slightly coloured. The quantity of extractive in ordinary wines and beers is of course much less than that used above, the object of the experiment being to emphasize the erroneous indications of the old formula. DISCUSSION. The President thereupon stated that Mr. Allen was unavoidably absent that evening and had requested him to give an abstract of the paper which Mr. Allen had intended to read, and which was the outcome of a conversation he had had with MI-.Blunt. He (Mr. Hehner) had also made some experiments, t o ascertain experimentally, which He prepared a dilute alcohol, the specific gravity of which, when 50 c.c., were, by the addition of water, made up to 100 c.c., was 0,9775. This alcohol, after distillation again, showed a specific gravity of 0,9775, showing that careful distillation did not entail any loss of alcohol whatever. He further made a sugar solution, 50 c.c., of which, when made up with water to 100 c.c., had a specific gravity of 1.0575. A mixture of 50 C.C. each of the alcohol and sugar solution, also made up to 100 c.c., had a specific gravity of 1.0356, determined twice on separate mixtures. 100 C.C. were then distilled, and both the distillate and the residue in the retort made up to 100 C.C.The gravities were determined, and found to be 0.97757 and 1.0577. Now, calculating by the division formula, the speciik gravity of the spirit would be 0.9791, and by subtraction 0.9779, the former corresponding to 29.92 per cent oE proof-spirit, the latter to 32.19 against 32.91 taken. of the two formulie for calculation was the correct one.THE ANALYST. 223 These figures, which were, as far as he (Mr. Hehner) could see, free from any source of error, absolutely confirmed the conterition of Mr. Blunt, that the division formula was incorrect. It was remarkable that this matter had escaped notice so long. In the work on Wine, written by Dr. Thudichum and their distinguished and respected past President, Dr.Dupre, the matter was discussed a t some length ; but, while the division formda was declared to be the correct one, it was stated that by the subtraction method the more accurate results were generally obtained. In quite a modern work, by Dr. J. Kenig (Untersuchung landwirthschaftlich : wichtiger Stoffe), the difficulty is got over by the bold declaration that the two formule were identical. This is, of course, not the case, as can readily be seen from an example. If a mixture of sugar solution and alcohol had a specific gravity before boiling of 1.2, and after boiling of 1.4, then the division formula would give O*S57, and the subtraction formula 0.800 as the gravity of the alcohol. Mr. Bodmer said that he had not had the advantage of hearing the commencement of the paper, but that he had nevertheless gathered its meaning.He had recently had occasion to sample commercial spirits, and had generally found that the subtraction method was inaccurate; but when the amount of sugar present was not excessive then the division method and distillation method agreed very closely. The President asked Mr. Bodmer how much sugar he had found in gin? Mr. Bodmer replied that he had never determined the amount of sugar directly, but the gravity of the de-alcoholized gin was as much as 1.010, and, in extreme cases, 1.015. Since the reading of Mr. Blunt’s paper, my assistant, Mr. Skertchley, has, at my request, made the following determinations. A number of mixtures of alcohol, sugar and water were made. 100 C.C. were distilled, and the specific gravities of the original mixtures, and of the distillates, and of the residues in the retort were carefully taken in duplicate, after the fluids had been made Up to 100 c.c., all measnremeilfa bekg made at 15.5C. Specific gravity of Mixtme. Sugar sol. Distillate. Division. Sub traction, 1.0036 1.0175 0.9855 0.9863 0.9861 1.0211 1.0468 0.9738 0.9754 0.9743 0.9831 1.0254 0.9579 0,9587 0.9577 1.0504 1.0626 0.9866 0,9885 0.9878 Thus, in all cases, the results obtained by subtraction are closer t o those obtained by distillation than are those by Tabarie’s formula, and the results we better the greater the alcoholic strength. 0, H,224 THE ANALYST. The Secretary then read the following paper, also an extract from a letter received from the author,

ISSN:0003-2654    

DOI:10.1039/AN8911600221

出版商:RSC    

年代:1891

数据来源: RSC

摘要:

224 THE ANALYST. Total Mineral Matter (Ash) ... ... ... ... Sand in Ash ...... ... ... ... .,. Sulphate of Lime in Pepper ... ... .. Carbonate of Lime in Pepper ... ... .., Microscopical Examination for Foreign Structures . . , Woody Fibre ... ... ... ... ... ... ON THE ADULTERATION OF WHITE PEPPER. 2.25 o/o 9.90 o/o 8.35 o/o 5.55 o/o 1.82 o/o 9.66 ,, 9.73 ,, 9-74 ,, 3.66 ,, 3.40 ,, trace -28 ,, a38 ,, -23 ,, 043 ,, trace 2.85 ,, -57 ,, 2.10 ,, -12 ,, -29 ,, 5-07 ,, 5.59 ,, 2.20 ,, *27 ,, none none none none none BY W. F. K. STOCK, F.C.S., F.I.C. JUDGING from numerous papers to be found in THE ANALYST, the analysis of White Pepper has already often been a subject of enquiry, and much useful information has been afforded by former investigators. There are, however, certain facts connected with the sophistica- tion of White Pepper which either have not attracted the attention of analysts, or which, if known, have not been made public; and it is with these facts that I shall deal in the present communication. Some time ago a firm of retail dealers in this county was proceeded against for selling White Pepper containing 4 per cent.of added mineral matter, which proved to be a mixture of sulphate and carbonate of lime. The case was strongly defended, the whole- sale merchants guaranteeing all cost. A conviction was obtained, and a fine of &2 was inflicted. The cost8 reached &34. Shortly after this the merchants wrote to me asking me to undertake the analysis of all their Peppers-Wbite and Black-and it was arranged, at my suggestion, that the analysis should show the following items :- Total Mineral Matter (Ash at low redness), Sand in Ash, Sulphate of Lime in Ash, Carbonate of Lime in Ash, Woody Fibre, Microscopical Examination.It was clear that nothing in the shape of adulteration could escape such a method of examination, and I shortly had an opportunity of proving its usefulness. I received a parcel of 5 Samples of White Pepper upon which I was asked to report as to whether they were genuine. No information was given. The results of my analyses were RS follows :- Nature of Determination. I No. j No. 1 No. 1 No. 1 No. ‘--I- I I I I tTHE ANALYST. 225 Tellicherry. Siam. 4.43 ,, Ash ... ... ... ... 1.05 o/o 1.45 o/o Fibre ... ... ... ... ... 4.86 ,, Calc. Carb. in Pepper ...... I.. -58 ,, -62 9 , Calc. Carb. in ,48h ..* ... ... 55.20 ,, 42.70 ,, I I Determination. Lampong. Penang. 4-90 ,, 6.06 ,, 2-20 o/o 2-75 O/,, -81 ,, 1.67 ,, 36.80 ,, 60.70 ,, Ash ... *.* ... ... ... Pibre ... ... ... ..* ... Calc. Carb. in Pepper ... ... ... Calc. Garb. in Ash ... ... ... * By decorticated corns is meant those pepper corns which are imported for the purpose of producing White Pepper, and from which the true cortical layer of the berry has been removed by a rough process. There ia a decorticated white known in the trade, but in this the inner layer corresponding to the liber of an exogeneous stem has also been removed, and only the clean kernel remains. 1-10 o/o 2.65 o/o 3.65 o/o 3.10 o/o 4-10 ,, 4.93 ,, 6.60 ,, 6.16 ,, -54 ,, 1.88 ,, 2.43 ,, 2.20 ,, 49.00 ,, 71.00 ,, 66.60 ,, 71.00 ,,226 THE ANALYST.Ash ... . .. ... ,.. Fibre . . , ... ... ... Calc. Carb. in Pepper ... Calc. Carb. in Ash ... ... Six samples of Blended and Graded White Pepper also said to be poduced from the above. 1.47 "lo 2.45 "lo 3.05 o/o 3-55 o/o 4-90 O/, 1.70 ,, 3.33 ,, 3.43 ,, 4.00 ), 8.23 ,, -69 ,, 1-61 ,, 2.20 ,, 2.50 ), 3.15 ), 47.0 ,, 66.0 ,, 72.0 ), 70.4 ,, 64.3 ,, Determination. 1 N o . l . 1 No.2. I No.3. 1 No.4. 1 No.5. I I I I I- I i I I- No. 6. 4.35 o/o 10.43 ,, 2.16 ,, 49.6 ,) I n connection with these analyses, I may say that I was well aware of the practice of bleaching and facing white pepper corns, having got samples of both bleached and faced corns from well known houses; but I was hardly prepared for the great differences found in the percentage of ash and the percentage portion of lime to ash in terms of carbonate exhibited by these samples.The latter comparison is an idea which has proved of the greatest service in the analysis of White Pepper. I was quite satisfied, from the figures obtained, that the samples sent ready ground had received an addition of carbonate of lime, but in order to set the matter quite at rest, a flotation experiment with chloroform was made, and the carbonate of lime, in, the form o j chalk, was duly discovered and identified. The analyses of the graded samples, in spite of the alleged increase of ash by grading, show that carbonate of lime has been added, but it was thought worth while to ascertain by experiment what foundation such an allegation could have in fact.To this end, two samples of Tellicherry Pepper were analysed ; the one undecorticated, the other decorticated, when the following results were obtained : - Determination. Decorticated. I Undecorticated. Total Ash .., ... ... ... ...I 4.02 Fibre ... ... ... ... .-. ... 10.40 27-30 Percentage proportion of Lime t o ash i n ' terms of Carbonate 1.64 6-80 62.00 These figures prove beyond doubt that the natural calcium compounds of Pepper are more abundant in the kernel than in the husk, and that instead of the calcium compounds augmenting directly as the proportion of husk, they are in inverse proportion. The analyses just given cannot be compared with analyses of bleached samples, because the calcium compounds and the fibre are profoundly affected by the bleaching process.I n dealing with this question, we must keep the fact in view that by no process of grading can the normal relation of the ash constituents of the kernels be disturbed. This fact,THE ANALYST. 227 Between Between Between Between 1 o/o & 1.5 o/o 26 Samples. 37 Samples. 18 Samples. 9 Samples. 1.50 o/o & 2.0 o/o 2.0 o/o & 2.50 o/o 2.50 o/o & 3.0 o/o I___----- joined with a knowledge of the natural percentage of ash, and the normal relation of lime to ash in terms of carbonate, gives the necessary data for determining any abnormal proportion of calcium salts in white pepper. I was assured by the grinders of these Peppers that analysts, members of this Society, were in the habit of passing, as genuine, ground White Pepper with 5 to 6 per cent.of ash. If this be true, the said analysts are not doing their duty. No genuine White Pepper, according to my experience, contains more than 2.75 per cent. of ash; and if grinders choose to bleach and face White Pepper, they must expect to share the fate of those who, a while ago, put a false complexion upon Tea. For myself, I shall pass no sample where the ash exceeds 3 per cenl;., and where I find the proportion of lime to ash, in terms of carbonate, to exceed 60 per cent. Whilst adopting these figures, I have no doubt they allow considerable latitude, for they are got from the analysis of Penang White, which is apparently lower in quality than any other White Pepper used. That the ash standard is quite fair for commercial samples is shown by the following table of analyses of 100 samples of White Pepper, collected indiscriminately by the Inspectors of Food and Drugs acting for the County of Durham :- Determinations OJ Total Ash on 100 Samples of White Pepper.Between 3.0 o/o & 3.45 o/o 10 Samples. - - ~~~~~ Lowest Ash ... ... ... 0.80 per cent. Highest ,, ... ... ... 3.45 ,, Average ,, 8.. ... ... 1.914 ,, In conclusion, I feel that when an adulteration amounting apparently to only 2 per cent. is in question, the lay mind is apt to look upon the offence with considerable leniency; and, if it were only a question of bulk and weight, it would, comparatively, be of small importance. But there are two points which the analyst must always have clearly defined in his own mind. The first is, whether the article is, according to the best of his knowledge and belief, genuine.If not, he cannot ti7uthfdly pass it aa rich, ilc matter hmv small the proportion of adulterant used ; and one has only to turn one’s thoughts to the presence of aluin in bread to see the force of this, Then he must have regard to the purpose for which the adulterant is used : and in the case of White Pepper-an article of which colour is a gniding feature of quality, there can be no doitbt that chalk or other lime compound, when present, is used to produce fictitious whiteness. The President, having invited discussion, A Member enquired whether. the sample referred to in Mr. Stock’s letter was purchased from a wholesale film, or from a retail dealer ? Mr. Bernard Dyer replied that he could add notliing to the information afforded by228 THE ANALYST.Mr. Stock, which was, that the sample in question was purchased from ‘ I a well-known firm in the City of London.” Mr. Stokes remarked that anybody who tried to get the fibre out of pepper by the ordinary method of treating it with sulphuric acid and potash, was well aware, that on treating by potash one got a gelatinous mass which would not pass through a filter. He would like to know how Mr. Stock managed to make a separation. Mr. Bernard Dyer said that he could not reply on the author’s account, as he was not acquainted with the method followed by him. But he might tell Mr. Stokes, from his own experience, that he could avoid the trouble he had mentioned by extracting his pepper first with ether, and then with alcohol. The pepper, after being thus extracted, was treated with acid and alkali in the ordinary way. By following that course himself, he had altogether overcome the difficulty which Mr. Stokes mentioned, and the fibre could be filtered easily and quickly. The President wished to draw the attention of the members to a very interesting paper on this subject, which had appeared in a recent number of Zeitschrift f. angewandte Chemie,* and of which an abstract would appear in the ANALYST shortly. Mr. Stock appeared to doubt that genuine pepper could be graded; but he (the President) ventured to think that he would be of a different opinion if he had read the paper in question. For his own part he did not like a hard and fast line being drawn with reference to the amount of ash which white pepper should contain.

ISSN:0003-2654    

DOI:10.1039/AN8911600224

出版商:RSC    

年代:1891

数据来源: RSC

摘要:

228 THE ANALYST. Mr. Stokes then read the following paper :- THE ESTIMATION OF FAT I N MILK. BY A. H. STOKES. IN the Berichte, vol. xxiv., p. 2204, there is described and 6gured by E. Molinari, an apparatus for rapidly estimating fat in milk. It is also described, and illustrated in the last number of THE ANALYST. The apparatus is very delicate and, as figured, exceedingly difficult to clean, It is claimed that an analysis would take from 30 to 35 minutes, though if you sum up the times given by the inventor for each step of the process, it will take a t least 50 minutes. But then, as a fat determination can, with only a simple tube, already be performed equally accurately in 20 minutes, there is no gain of rapidity. If it requires, as it probably would, half an hour besides to clean up the apparatus, there would be a great loss of time.The idea of the apparatus is to prevent any transference from one vessel to another; the fat is set free, washed and weighed all in the same vessel. 1 have devised a far simpler apparatus which will do this equally effectually. It consists (see fig 1) of an Erlenmeyer flask of about 50 C.C. capacity, to the neck * See abstract in this Journal, page 233.THE ANALYST. 229 ~~ - of which is joined a bulb of about 60 C.C. capacity terminating a t the apex in a short glass tube with a tap to it. At the neck, where the bulb joins the flask, is a short side tube which can be closed by a cork. I t is used thus :- After being weighed, 10 grammes or 10 C.C. of milk are placed in the flask, heated almost to boiling, and about 10 C.C.of strong HCl added, this mixture is boiled over a flame for about one minute, left hot for about three minutes, then cooled down and ether poured in nearly up to the neck. The tap is closed, the cork inserted and the apparatus well shaken and then left for about five minutes to rest with the tap end downwards. The tap is now opened and as much as possible fo the acid liquid allowed to run out. The tap is closed, the cork taken out and about 10 C.C. of water run in and shaken with the ether and allowed to run out again through the tap; after standing awhile a second quantity of water is is thus used. Finally, the tap is closed, the side tube connected t o a condenser, the ether distilled off, and the apparatus with its residual fat placed in the water-bath to dry.This drying, I find, takes a very long time. The apparatus is very simple. The fat never leaves the apparatus after the milk is put into it but is treated and weighed all in the same vessel; no calculation is required. The objections to it are the difficulty of running off the acid or aqueous fluid so close as to leave none in the flask, or, on the other hand, to let none of the ethereal solution escape; the flask, being wet inside with water, takes a long time, sometimes hours, drying. A simpler and quicker process is the use of another piece of apparatus (fig. 2), in which a 25 C.C. flask, having a neck of $-inch diameter and one inch long, is surmounted by another flask of about 35 C.C. capacity, terminating with a mouth of $-inch diameter.Into this 10 grammes or 10 C.C. of milk are placed; it is then heated on the water-bath, directly the milk is near looo C. the HC1 is poured up to a mark near the beginning of the neck. By thus heating the miik before aciding aci;, no clots of cur6 are formed, After boiling for about one minute and leaving it hot for three minutes, it is cooled by placing it in a basin of water; the shape of the apparatus makes it float easily, so that there is no danger of its being immersed, however deep the water may be. It is now filled with ether up to about the middle of the upper bulb, a cork is inserted in the mouth and the whole violently shaken. On letting it stand abut three minutes it will be found that the brown acid liquid comes up to the middle of the neck with a very slight layer of fluffy white casein between it and the ether.Taking out the cork, a double tube arrangement like that of the ordinary wash- bottle is inserted. The cork of this should not be of indiarubber, but of ordinary cork, for two reasons : first, because a glass tube does not slide easily in rubber exposed to ether 3 I Fisl.230 THE ANALYST. - vapour ; second, to avoid any chance of a solution of rubber being weighed off as fat. The longer tube of this is forced down till it almost touches the casein layer. A weighed flmk is placed under the upper end of the tube, and by blowing into the other tube the fat-ether solution is driven into the weighed flask. About 10 C.C. more ether is placed in the apparatus and the whole shaken; after three minutes settling this ether is added to the first quantity.Another repetition of this leaves the liquid practically free from fat. The weighed flask is connected to a condenser and the ether distilled off. I find that if the flask is almost entirely immersed in boiling water, the ether does not boil violently, but is rapidly and quietly distilled off. In fact, it will evaporate as quickly as if placed in an open dish on the water-bath. The flask is now dried in the air-bath for fifteen minutes and then weighed. The weight of fat multiplied by 10 gives the percentage if 10 grammes of milk were taken. If 10 C.C. were taken it is only necessary to divide the weight of fat by the specific gravity of the milk. In about 30 minutes the whole process may be completed.With both pieces of apparatus I have obtained results identical with the calculated results and with those of the paper-coil process. In both cases the acid liquid and the washings are put into residue bottles and the ether afterwards recovered, so that hardly any ether is lost. The principles of these are just the reverse of one another; from one the acid solution is expelled, from the other the ethereal solution is expelled. Apparatus No. 2 is by far the quicker, easier and less liable to error. It embodies Mr. A. H. Allen’s principle of doing away with calculation ; the narrow neck in the middle enables the ether to be drawn off almost entirely each time; the shortness of the bulb containing the ether allows the acid to settle out in the quickest possible time after shaking.But neither of these methods is so rapid as the use of the long tube described in ANALYST XVI., p. 71, a figure of which I show to-night (fig. 3) alongside of the original short tube. By the use of a centrifugal apparatus giving about 3,000 revolutions per minute, I can separate in this the ethereal layer in one minute, and, working in the way described in the ChemicaZ News, of November lst, 1889, can complete a fat extraction in 16 minutes ; without the centrifugal apparatus the fat has been frequently determined in 20 minutes accurately in my laboratory. Before trying any special apparatus, I experimented to see if there could be any destruction or loss of fat. I boiled known weights of butter-fat with HC1 and water, extracted with ether, and recovered exactly the same amount of fat I put in, unaltered I took quantities of the brown acid liquid after it was done with, and found it to be abwlutely free from any fat.The fat obtained in the other cases I have examined and found to be nothing else but butter-fat. I experimented with ether containing known percentages of alcohol; up to 18 per cent, alcohol does not interfere with the process. Ether containing fat can be blown of3 or pipetted off just as easily as water, I tried other solvents than ether and other acids than HCl.THE ANALYST. 23 1 Occasionally on boiling milk with HC1 and shaking it with ether, it forms a gelatinous mass from which the ether will not readily separate. This is usually due to not having boiled the two together long enough.On the other hand, too long boiling causes the casein to form bulky black flakes. The boiling may safely last from one to three minutes. If a milk does not turn the usual dark brown colour after threeminutes, you may be sure it has been watered. After a practical experience of every known method of fat extraction of milk, and a three years’ special devotion to this method, I can assure the Society that there is no other method that at present can possibly compare with it for accuracy, simplicity, rapidity and cheapness, whether applied to cream, whole milk, skim milk, sour milk or condensed milk (sweetened or unsweetened). No analyst of my acquaintance after trying this method has gone back to any other, and I know now,some dozen who habitually practise it.To my assistant, Mr. W. N. Yarrow, I am indebted for the diagrams shown to-night. I am pleased tobear testimony t o the wonderful way in which fats thus determined agree with the calculated results given in the admirable table of Messrs. Hehner and Richmond in THE AXALPST, XIII., p. 26. Mr. Cassal said that while the special object of Mr. Stokes’ paper was not quite clear, all would, no doubt, agree, that the Werner Schmid process was very valuable. The minute description of the pieces of apparatus represented by the diagrams appeared to be hardly necessary. The apparatus, described at such length by Mr. Stokes, seemed to be ingenious, but then Mr. Stokes had said that it should not be employed, as it was no use, and that it was almost impossible to clean it and dry it.He submitted, therefore, that this apparatus would not commend itself to the members of the Society. Mr. Stokes had described another piece of apparatus, which closely resembled a wash bottle. Mr. Stokes stated that he originally used a straight tube, of which an illustration was before them. A highly satisfactory point about the Werner Schmid process as amended, was, that after extracting with ether, one m i d blow out t h e whole of the ethereal solution by means of the apparatus suggested by Mr. Chattaway, evaporate it, and weigh the total amount of fat. The removal of a measured portion of the solution, by the rending off of the residual portion, mas very undesirable in such a process, and formed a source of error. W-hen, without unduly increasing the time legitimately required for such operations, one could obtain and weigh the whole of the fat in the portion of milk taken for analysis, he did not think that there was any advantage to be gained by the measurement modification sufficient to compensate for the risk.He himself had found that excellent results could be obtained by the Werner- Schmid process, and Mr. Stokes was to be thanked for having introduced it to their notice. He (Mr. Cassal) had found that accurate results were most satisfactorily obtained232 THE ANALYST. by the use of a simple tube provided with the wash-bottle arrangement, suggested by Mr. Chattaway, and which he had just referred to. Mr. Cassal wished to state that his approval of the Werner Schmid process was mainly based upon its value for the analysis of decomposed milk.If a large number of analyses of fresh milk had to be done, and something else at the same time, the Adams process should be adhered to, for the simple reason that it would go on automatically. That, however, did not detract from the superior value of the Werner Schmid process when employed under specific circumstances. Mr. Bernard Dyer thought that Mr. Cassal had, he was sure unintentionally, hardly treated Mr. Stokes qnite fairly, though he (Mr. Dyer) agreed with Mr. Cassal that it would have been perhaps better that they should not have been troubled with a lengthy description of an apparatus which they were afterwards advised not to use. One of the features of the Schmid process was that one need not trouble to take off all the ether, but could stop it a t any graduated point which one might think desirable. Mr.Cassal, however, had said that he did not consider that fractional removal was a good method of working, but that it was much better to take off the whole of theether at one operation. Now it seemed to him that Mr. Stokes had devised a simple substitute for the original Schmid tube, by means of which he did take off the whole of his ether, thus doing exactly what Mr. Cassal would do with the original tube, on which he had the graduations, but thought it unnecessary to make use of them. If he remembered rightly, Mr. Stokes had told them on previous occasions that the method of pipetting and not troubling to remove the whole of the ether gave results which were very satisfactory indeed. The President asked Mr.Stokes to state what was the number of analyses which he considered a man could conscientiously and honestly make in a day by means of the process before them. Mr. Stokes replied that he considered the advantage to be this : that whereas it was impossible by the old process to analyse a sample in half-an-hour, it could easily be done by the method which he had brought forward. The President said, that he looked upon methods which were said to give results in such a short time, with the greatest suspicion. Fat could not well be dried in an extraction-flask under a quarter of an hour, and the cask itself would have to stand before it could be accurately weighed for about 10 minutes, which almost made up the half-hour given by Mr.Stokes. He could see no possible object or advantage in these rapid analyses, They were all obliged to Mr. Stokes for bringing the Werner Schmid process so prominently before them, and for proving that it was capable of giving good results. Yet, having heard all that had been urged in favour of the process, he (Mr. Hehner) could yet not see where its advantage over the excellent Adam method lay. That process was absolutely automatic, and required the least possible amount of attention, which was a more important point for the analyst than extreme rapidity. He was of opinion that it would be far better for public analysts to stick to the Adams process, which had been universally accepted as being the most accurate one,THE ANALYST. 233 unless any other process effected a decided improvement upon it.For his own part, he could not see that the method so strongly recommended by Nr. Stokes possessed such decided advantage. Mr. Cassal said that he had stated that the tube, which formed part of Mr. Stokes’ wash-bottle apparatus, was originally suggested by Mr. Chattaway, but he understood Mr. Stokes to say that that was not correct. He therefore thought it necessary to ask Mr. Stokes to explain to the meeting the precise difference between the two forms of apparatus. His own impression was, that at the time the Werner Schmid process was first introduced to their notice, the we of an ordinary tube-not graduated or narrowed -was recommended by a member present, and that then Mr. Chattaway explained that he had devised a modification of the wash-bottle for the purpose of removing the whole of the ethereal solution after the treatment of the milk.Mr. Stokes, in reply, said the main reason for the modifications which he had intro- duced was that he required to make his determinations quickly, I f he had to wait for every operation he would lose a lot of valuable time, which he could not afford. That brought him to the President’s question, namely, how many could a man honestly do in a day’! He was hardly in a position to give a definite reply to that question, as he had never had occasion to do fat determination only; but he might say that he had 30 or 40 samples to test in a day, and they had to be done promptly. Mr. Dyer had suggested the excision of what he called the intermediate apparatus.The diagram (“ ANALYST ’’ xvi. 209) had already been given in the Journal of their Society, and he conceived that a man on first seeing it might consider it to be a good idea, as it really looked SO theoretically, and waste time in trying to work it. In order to avoid that, he had shown a simpler apparatus that answered the same purpose copld be made for the small sum of 2s., and which would be of use for other purposes than extracting fat from milk. Coming to Mr. Cassal, that gentleman had said that he found a great advantage in blowing off the whole of the ether. He (Mr. Stokes) quite agreed with him, but if Mr. Cassal meant to inform him that ether shaken up with the acid fluid would separate as rapidly in the long tube he had hitherto employed as it would in the short bulbs now before the meeting, he would be surprised indeed.For his own Part, he believed that some day Mr. Caxsal would adopt the apparatus which he had brought forward, and would admit that it had advantages over any hitherto employed for the purpose. The following “ Notes from the Khedivival Laboratory,” by H. Droop Richmond, 1. The relation between Specific Gravity, Fat, and Solids not fat in the milk of the Gamoose. 2. The estimation of Iotloform. 3. The testing of Betrolenm. This termiiiated the proceedings of the Society. were taken as read :-234 THE ANALYST. Rapid valuation of Commercial peptones. By M. A. Denaeyer. (Journal de Pharmacie Anvers. Novembre, 189 I).-Alcohol of 95% added in excess to concentrated solutions of meat peptone precipitates undigested albumins, albumoses, pure peptone and gelatin.(1 .) The extractive principles of meat (carnine, creutines, creatinines, &c.) ; ( 2 ) the products of decomposition of albumins (leucine, tyrosine, aspartic acid, &c.) ; (3) the pro- ducts of decomposition of gelatins (akanine, glycocoll, urnido-butyric acid, &c.). It follows from these facts that alcohol constitutes an excellent agent for the valua- tion of commercial peptones ; the larger the amount of the precipitate the greater will be the strength of the peptone in the nutritive elements ; albumoses, peptone, acid- albumins. We must remember that albumoses and true peptone are only found in peptones produced by the digestion by means of gastric juice; the acid-albumins which enter into the composition of artificial peptones (vupeur peptones 2) have apparently, as far as assimilation is concerned, no higher value than ordinary albumin.The determination in a peptone of the matters soluble in alcohol is made by dissolv- ing 2 grms. of peptone, calculated as dry matter, in about 10 e . ~ . of water. This solution is precipitated by 100 grms. of alcohol, and the mixture is allowed to stand for 24 hours in a cool place. The alcoholic solution becomes quite clear; it is decanted, and the precipitate washed, the alcohol distilled off and the residue evaporated to dryness in a basin on a water bath. The desiccation is completed in an oven at 105' C. to constant weight. On the other hand the alcohol separates by solution :- In the same way the weight of the alcoholic precipitate is taken after complete drying.A well-prepared meat peptone should not give above 30 per cent. of alcoholic extract, but commercial preparations are found which yield as much as 60 per cent. These extracts then contain besides creatines and normal extractive bases, great quantities of the products of decomposition of the albumins (leucine, tyrosine, ccspccrtic acid, caproic acid, &c.), and of the gelatins (ylycocoZZ, leucine, ulunine, anaido-butyric acid, &c.) of muscular tissue. I n fact a few drops of the alcoholic solution evaporated on a glass slide show under These excrementitial products, destitute of alimentary value and formed in defective digestions at the expense of the albuminoids and colloids of meat, represent the deficiency in gelatin, albumin and peptone of these preparations. The estimation of the alcoholic extracts allows, as will be understood froin the above, of the determination of the dietetic equivalent of all preparations of meat peptone : it gives at the same time valuable indications as to the nature of the digestive operations.the microscope leucine and tyrosine with their characteristic forms, besides other things. It will be remarked that in very acid and long sustained digestions the alcoholic extract of the peptone obtained will be rich in the products of decomposition, whilst theTHE ANALYST. 2 35 ~~ ~~ ~~ concentrated solution of peptone (&) will only yield a small precipitate with the alcohol (30 t o 40 per cent.at most). On the contrary, in digestions faintly acid and well regulated in regard to duration, temperature, weight of pepsine, hydrochloric medium, &c., the alcoholic extract which the peptone yieIds will be small, but on the other hand the precipitate of gelatin, albumoses, and peptone very abundant (rising to 70 per cent.). These assays are very interesting ; we recommend them to our confrdres. By a simple precipitation with alcohol they will be enlightened as to the respective merits of the preparations of peptone which they purchase. c. w. H. On t h e Grading of Pepper. By H. Trillich. (Zeit.,f. nngew. Chem. 1891, 1). 51 ti).-The Society of Bavarian Chemists having resolved that the highest permissible limit of ash in black pepper be 5.6, with 2 per cent.of matter insoluble in acid, the mthor investigated the influence of milling and sifting upon pepper. The mill employed consisted of two grooved steel rollers. The crushed pepper pxsses on to a sieve, the siftings being separately collected, whilst the coarser particles went back upon the rollers over and over again, until no more would pass through the sieve. The remainder went into another mill, and was sifted once more. Thus 12 different siftings were obtained, which were separately examined. The first and second portions allowed a fairly equal mixture of black particles of husk and white particles of the inner berry. The subsequent products become successively lighter up to a certain point, znd then again darker until the last consist of greyish black particles, mostly consisting of husk.The first series of experiments were made with Prima Singapore pepper, the berries containing 3.54 per cent. of ash with 0.09 per cent. of sand. 1,000 grammes contained 0.275 grammes of dust, with 0.0s grammes ash (29'lo), and 49.80 grammes of stalks, with 0.655 ash (13-1"/,). 1,350 kilos were ground, and the separate portions gave the following results : - Keight. No. kilo. p.c. 1. 284 22.7 "t 209 16.9 3. 4. 5 . 1 3 3 8 27.1 G * \ 7. 10. Water, 13-89 14.10 14.22 13-49 13.16 13.34 12-96 13.10 12.87 12.89 Ash. Sand. Pure Ash. 3.71 0.37 3.34 2.S6 0.15 2-71 3.04 0.27 2-97 3.17 0.19 2-98 3-30 0.17 3.13 3-50 0.16 3.34 3.80 0.13 3.67 3.82 0.15 3-67 3.95 0-10 3.85 5.11 0.13 4-98 12.38 7.52 0.09 7-43 "'} 218 17.5 12. 12.91 7.50 0.10 7-40236 THE ANALYST.The greater portion of the sand, therefore, goes into the first part of the product, the percentage of ash in which is large. Curiously, the amount of ash in the following por- tions steadily increases, while the sand remains practically the same, but the last two fractions have a much higher amount of ash with still less sand. The second series of analyses were made upon products similarly obtained with Lam- pong pepper, which is of lower quality than Singapore. The berries contained 4.50 per cent. of ash with 0.52 per cent. of sand. 1,000 grammes contained 6.004 grammes dust, with 2.704 ash, or 45.03 per cent., and 1.957 grammes sand, or 32.58 per cent.; also 1.691 grammes woody pepper portion, with 0.256 ash or 15.14 per cent.; 0,111 sand, or 6.56 per cent., and 4,877 grammes stones. These impurities would raise the percentage of ash and of sand in the pepper to, as near as can be estimated, 5.60 per cent.and 1-50 per cent. respectively, The following are the analyses of the various fractions :- NO. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Weight. kilo. p.c. 72.5 13.8 49.5 9.4 54.0 10.3 63.0 12-1 54.0 10.3 52.5 10.1 30 5.7 42 8.0 43 8-3 35-5 6-8 13.5 2.6 13.5 2.6 Water. 12.72 12.82 12.99 13.37 12.98 13.33 13-29 13.54 13.70 13.18 11.72 11.94 Ash. Sand. 10.92 5-66 6.98 2-86 6.30 1.93 5.82 1.22 5.24 0.71 5.56 0.15 5.18 0.51 5.54 0.64 4.91 0.28 5-67 0.35 7.46 0.43 7.22 0.46 Pure Aeh. 5.26 4.1 2 4.37 4.60 4.53 4.81 4.67 4.90 4.63 5.32 7.03 6.76 Here again the larger fraction of the sand went into the first fraction, whilst the ash proper steadily rose, 0.H. The Adulteration of Basic Slag. Morgen. (Read at the 64th rncetimg of th Beutsch. Naturforsch. u. Aerxte. Through Chem. Zed.)-The adulteration of basic slag with aluminium phosphate can be detected by the loss on ignition, which, when it amounts to 18 per cent. is an almost certain indication of falsification. The addition of Redonda phosphate is detectable by the determination of the specific gravity ; the author prefers to use bromoform for this purpose, rather than the potassium-mercuric iodide solution employed by Loges. Besides these tests, the production of a copious precipitate with caustic soda solution is an indication of the presence of the same adulterant. The best method for the quantitative examination of basic slag consists in treating the sample with a 5 per cent.THE ANALYST.237 ~~ solution of citric acid, in which the phosphoric acid natural to the slag is completely soluble while that of Redonda phosphate is not dissolved. Faffin slag behaves similarly to Thomas slag, save that it remains suspended in bromoform. A new adulterant has been noticed by Loges, containing4 per cent. of caustic lime, 6#4 per cent. of carbonate of lime, and the remainder calcium fluoride ; it is said to be of English origin. [NOTE BY ABSTRACTOR.-A letter appears in the Chem. Zeit. 1591, 1449, signed Warth and Wagner, pointing out that the loss on ignition is not to be relied on for detecting the adulteration of basic slag, as samples that have been exposed to air and moisture may absorb a good deal of water and carbonic acid, which they lose on ignition, An error in the contrary direction is imported by the circumstance that the slag may contain ferrous and manganous oxides and absorb oxygen on heating.The presence of calcium fluoride is not necessarily evidence of adulteration, as it may have been introduced for metallurgical reasons.] B. B. The sensitiveness of various Tests for Arsenic. C, 0. Curtmann. Through Chem. Zed.)-The author has examined a (Pharrn. Rzcndsch. 1891., ix. 175. number of tests for arsenic as fo sensitiveness, and records the following results :- 1. Sulphuretted hydrogen; 0.01 mg. As,06 in 1 C.C. of liquid, gave a slight yellow turbidity after two minutes; 0.001 mg. &,O, gave a yellowish tinge after 15 minutes; when the dilution was greater no reaction was obtained, 2.Silver nitrate; 0.01 mg. As,06 in 1 C.C. gave a slight yellow turbidity after six minutes ; the reaction ceased on further dilution. 3. Scheele’s reaction; [Ammonium-Copper Sulphate] ; 0.1 mg. As4O6 in 1 C.C. gave a slight green precipitate immediately; the limit was reached with 0.01 mg., which gave a scarcely perceptible turbidity after some time. 4. Bettendorff’s method [Stannous chloride in concentrated hydrochloric acid] ; 0.1 mg. As,O, in 1 C.C. gave a slight brown colouration ; 0.01 mg. gave no reaction. solution of silver nitrate]; 0.001 mg. As4O6 in 1 C.C. gave a yellow stain after 30 minutes, which, when moistened, became bright brown. The iimit was reached at G*GOOl mg. which gave a barely perceptible stain after one hour, the colouration becoming more perceptible on moistening and again drying.It is therefore possible, by means of Gutzeit’s reaction, to detect 0” part of arsenious anhydride in 10 million parts of solution. The method is, therefore, eminently suitable for testing reagents for analysis, but is far too sensitive for testing pharmaceutical preparations, for whc\ purpose Bettendorff’s method is better fitted. 5, Gutzeit’a reactiori jactie,ri of a,rgei&zl hydrogen up=^ 8 Trey;. concer,trated238 THE ANALYST. On the estimation of Mixtures of Saponifiable and Unsaponifiable Fats. (Zeit. J. angewcmdt. Chemie. 1891, p . 565).-The absence of concordant results in analyses of mixtures of the above-mentioned substances made by different chemists, may be traced to the inexactitude of the methods employed. These (putting on one side the iodine and bromine addition processes as entirely useless) are the three following :- 1.The mixture is saponified with alcoholic potash, the unsaponified portion being caused to separate either by boiling, or by being kept warm for some time, The separation is never complete, and, consequently, the results are always too low, 2. The soluble soap obtained by saponification with alcoholic potash is either as such, or after conversion into an insoluble soap, thoroughly dried and exhausted with ether or petroleum ether. This process only gives exact results when the soap is absolutely dry, and when the slight solubility of soap in petroleum ether is taken into account. Since the drying and extraction of the soap are both tedious operations, the process cannot be recommended for practical use.3. The alcoholic solution of soap, obtained on saponification, is repeatedly shaken out with petroleum ether, or extracted in a suitable apparatus. This method, as shown by Morawsky and Dembsky (Dinglers Polyteckn. 1885, p . 39), gives rigidly accurate results when certain precautions are taken. .Messrs. Honig and 8pitz propose a modifkation which, without interfering with the exactness of the process, considerably shortens the time of its execution. This consists in using, instead of water, 50 per cent, alcohol for wMhing the petroleum ether layer, to remove the small quantity of soap taken up by it. By this means the two layers of fluid separate almost immediately.The two processes recommended are as follows :- (A.) 7 to 10 grms. of the fat are boiled under a reflux condenser, with 20 t o 25 C.C. of strong alcoholic potash and as much alcohol for 5 to 10 minutes; 30 to 40 C.C. of water added, and the whole boiled up once. After cooling, the soap solution is run into a separatory funnel, the flask rinsed out with 50 C.C. of alcohol, then with 50 C.C. petroleum ether, and the whole thoroughly well shaken. The alcoholic soapy layer quickly subsides, and is run off. The petroleum ether layer is now shaken out 2 or 3 times with 10 to 15 C.C. of 50 per cent. alcohol, the washings being added to the original alcoholic soap solution, The petroleum ether is emptied into a tared flask.The alcoholic soap.solution is shaken out with repeated quantities of petroleum ether, until a drop of the latter leaves no fatty stain after evaporation on paper. The dissolved soap is removed from each of the petro- leum ether washings by being shaken out thrice with 50 per cent. alcohol. The united petroleum ether washings are distilled off, a small weighed piece of pumice stone being added to prevent bumping. The last portions of petroleum ether are removed by heating the flask, and blowing into it. Petroleum ether boiling between 50 and 70" C. should be used. The alcoholic soap solution may, after boiling off the alcohol, be used for the esti- mation of the saponifiable fats by the usual methods. The whole process can be performed in an hour. M. Honig and G.Spitz.THE ANALYST. 239 (B.) When many determinations have to be made at one time, the authors propose a method of continuous extraction of the soap solution instead of shaking out, using for this purpose the modified form of a Soxhlet extracting apparatus shown in the accompanying illustration. Instead of the syphon, a small tube (h) is inserted about half way down the container A, and after one right-angled bend, passes downwards and enters the lower tube attached to the evaporating flask. A small thistle-headed funnel of such a length that its head is a short distance below the cork of the container, is inserted, its lower end dipping into a layer of glass beads about 1 centimeter deep. The alcoholic soap solution which, after dilution with water, should amount t o about 50 c.c., is shaken up in the flask with about 20 C.C.petroleum ether, poured into the extracting apparatus, the flask again washed out with petroleum ether, and finally with 50 per cent. alcohol. The surface of the soap solution should be about half a centimeter below the mouth of the draining off tube. After connection with the extraction flask, the small funnel is inserted, and 20 C.C. petro- leum ether carefully poiired in, the apparatus connected with a reflux condenser, and the ether kept boiling until it runs off quite colourless, and the soap solution is perfectly clear. The ether gradually becomes turbid from the soap dissolved ; this must be removed by shaking out the solution several times with 50 per cent. alcohol in a separatory funnel.(C.) If an approximate estimation only be required, the operation may be simplified as follows :-The saponification is effected in the flask shown in the figure, and which contains about 100 C.C. to the mark in the middle neck, this space being divided into two by a mark in the bulb. The amount contained between the marks in the upper and lower necks is exactly 30 C.C. ; 2 to 3 grms. of the fat are saponified with alcoholic potash, after cooling? filled up to the 60 C.C. mark with alcohol, then made up to 100 C.C. with water, 30 C.C. petroleum ether added, and the whole repeatedly shaken. After perfect separation of the ether, 20 C.C. of it are pipetted off, placed in a tared flask, the ether driven off, the fat weighed, and the requisite calculation made.This method, as shown by examples, gives results to within 1 per cent. of the truth. For the estimation of water, which, with the assistance of ammonia or ammonium carbonate, may be incorporated into the oil to the extent of 30 per cent,, without being detected by superficial observation, the authors recommend 20 grms. of the well-mixed sample to be dissolved in about 100 C.C. petroleum ether, and allowed to stand for an hour, filtered through a tared filter into a tared flask, taking care no water reaches the filter. The residue and filter are washed several times with petroleum ether, the240 THE ANALYST. ether driven off from the flask and filter, and the two weighed. The purified fat thus left may be advantageously used for analysis. The water may be also estimated by dissolving 15 to 20 grms.of the fat in petroleum ether, placing the liquid in a burette filled up to the lowest mark with water, and after standing some time, directly reading off the water. The dregs are estimated by atering the solution through a tared filter, washing with petroleum ether, drying and weighing. W. J. S. The Determination of Earthnut Oil in Olive Oil. Holde (Mitt. Karnig. Tech. Perszcchs., 1891, 9, 105, through Chem. Zeit.).-The usual method of detecting and determining arachis or earthnut oil in Olive oil, depending upon the isolation of arachidic acid needs modification in the case of oils containing only 5-10 per cent. of arachis oil, 40 grms. of the suspected oil being taken instead of the 10 grms. ordinarily prescribed, Moreover the aracbidic acid isolated by extraction of the palmitic acid which accompanies it when the lead salts insoluble in ether are decomposed by hydrochloric acid must be repeatedly recrystallized from 90 per cent. alcohol until its melting point ceases to rise, unless it be over 70° C. a t the first trial. B. B. Adulteration of Dried Mushrooms. P. E. Alessandrf (ZeitS. Nahl.ungsmittel-Urztersuchzcng u. Hygiene, 1891, 5, 79, through Chem. Zeit.).-The author found in samples of dried mushrooms offered for sale, about 30 per cent. of unequally thick white discsi, puckered or crumpled in aspect and brownish yellow (not chestnut brown) at the edges, which showed no wrinkles, hollows, or wavy lines like those on true mushrooms. They were coloured blue by iodine and when examined microscopically appeared to be simply pieces of turnip, dried discs of which presented the same appearance and be haviour. B. B. Remedy for ‘‘ Bumping.” E. Pieszezek (Chem. .%it. 1891, 15, P a 1126.)- The plan advocated consists in placing a glass tube about 5-8 cm. in length, and 5-10 mm. in width (the exact dimensions depending upon the bulk of liquid to be boiled) and closed at the upper end, resting against the side of the flask or other vessel to be heated, so that it stands nearly vertical with its open sharp-edged end pointing downwards. Boiling goes on quietly when once started, the bubbles making their appearance at the lower end of the tube. On cooling, the liquid rises in the tube which must therefore be raised and allowed to again become full of air before beginning the boiling again. The tube is best provided with a book of platinum wire fixed in the upper end for ease of handling. The device is said to be efficient even for liquids containing heavy precipitates such as barium sulphate, and lead sulphate, and is also recommended for the Reichart-Vollny process. B. B.

ISSN:0003-2654    

DOI:10.1039/AN8911600228

出版商:RSC    

年代:1891

数据来源: RSC