摘要:

PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. AN ordinary meeting of this Society was held at Burlington House, on Wednesday, the 8th June, the President, Mr. A. H. Allen, in the chair. The minutes of the previous meeting were read and confirmed. On the ballot papers being opened the following gentlemen were declared to be As asscci- elected: As member:---We T. MacAdam, public analyst for Portobello. ate :-T. W. Cbss, assistant to Dr. T. Redwood. The following papers were read and discussed :- (( Notes on the Logwood Test for Alum in Bread, etc.,” by W. C. Young. Quantitative determination of Pepper Mixtures,” by A. W. Stokes. Note on Pepper Adulteration,” by T. Stevenson. Dr. Muter’s paper The President then referred to On the American Methods of Manufacturing Oleomargarine, and the laws on the subject in the United States,” was taken as read. THE BILLS FOR DEALING WITH BUTTER SUBSTITUTES.The PRESIDENT said :- A Committee of the House of Commons is now sitting, under the presidency of the Right Hon. G. Sclater-Booth, to consider the two Bills proposing to deal with butter substitutes that were published in the last number of THE ANALYST. As you are aware, the Council have had the Bills under very careful consideration, and Mr. Hehner and myself have attended the meeting of the Committee on the two occasions on which wit- nesses have been examined. The first witness was SIR FREDERICK ABEL, who commenced by describing the process of manufacturing butterine, as he had seen it carried out in Holland. He drew124 THE ANALYST.a sharp distinction between butterine and oleomargarine, stating that the former was the finished product and ordinary article of commerce, while the latter was merely a manufacturer’s intermediate product, and not sold retail at all. In fact, he described butterine as a mixture of 50 to 60 per cent. of oleomargarine (the more fluid portion of animal fat), with ground-nut oil or sesame oil, churned milk or strongly-flavoured butter, and annatto or other harmless colouring matter. By an oversight he omitted to mention salt. Sir Frederick considered the term ‘‘ butterine ” preferable to “ oleomargarine ” aa a generic name for finished butter-substitutes. He considered butterine perfectly whole- some and unobjeotionable. When asked some questions relating to the analytical examination of butter, the witness stated that he had had no experience in that direction, and recommended that the inquiry should be made of an expert analyst. Mr.HERBERT P. THOMAS, the principal clerk of the Local Government Board in charge of the Public Health Department, was the next witness. He doubted the necessity for any special legislation on the subject of butter-substitutes, believing the existing laws were sufficient, provided that they were better administered. There was a great disinclination on the part of many of the local authorities to carry the Sale of Food Act into operation, and the fines inflicted were generally insufficient. He was not prepared to recommend that any minimum number of samples per 1,000 of population should be collected annually.The analysts had generally been exceedingly well-selected and performed their duties in a satisfactory manner. The witness thought the existing provisions respecting the declaration of the nature of mixtures were sufficient. He had known instances in which the last three letters of the word ‘‘ butterine ” had been covered up with a price label. I was the next witness called. I handed in a draft bill, drawn up by me after con- sultation with the Council of this Society. This draft wholly omitted the clause relating to informers, made the labelling of all butter-substitutes sold retail compulsory, and ren- dered an invoice equivalent to a warranty. In place of the unwieldy provisionsrelating to the employment of Inland Revenue officers, the draft contained a clause exactly similar to that in the Sale of Food Amendment Act, dealing with examination of milk in transit.Another clause of the draft bill was one which the Council agreed with me in con- sidering of great importance, and which ran as follows :- ‘‘ I n the event of any sample analysed under this Act being referred to the chemical officers of the Inland Revenue Department at Somerset House, under the provisions of the Sale of Food and Drugs Act, 1875, the chemical officersaforesaid shall, in their cer- tificate, state whether the sample had, by keeping or other muse, undergone any change that would interfere with the analysis, or the correct interpretation of the results of the analysis, and shall set forth fully their analytical facts and figures, and the r w n s for their conclusions ; and, in the event of their being unable to confirm the certificate of the public analyst, shall also state definitely whether they are in a position positively to con- tradict his conclusion; and in the event of the certificate of the chemical officers of the Inland Revenue Department failing substantially to support the certificate previously given by the public analyst, the public analyst may insist on being examined, and the prosecutor may require the attendance, for cross-examination, of the officer or officers of the Inland Revenue Department who made theanalysis, and the court shall take his or their evidence and that of the public analyst, into consideration in deciding on the caw.’’ Unfortunately, I was allowed no opportunity of explaining the unsatisfactory natureTHE ANALYST.125 of the present system of reference to Somerset House, although it is evident that the successful working of any Act dealing with butter-substitutes will be largely dependent on this point. Sir Richard Paget, who held a copy of Dr. Bell’s book in his hand, asked if it were not the case that the methods of detecting and determining butter-substitutes were based on the differences of specific gravity, of the percentage of soluble and insoluble fatty acids, and on the differences of the melting points. I replied that they were good as far as they went, but if relied on exclusively, 35 to 40 per cent. of adulteration might be overlooked. The method of Dr. Bell, based on specific gravity, which had done good service in its day, was only a rough test, and there were two other tests which, nowadays, no analyst would think of omitting.These were the methods of Koettstorfer and Reichert, the latter of which gave the sharpest existing distinction between butter and butter-substitutes. I n answer to Sir Henry Roecoe I described these processes in outline. Much of my examination was devoted to the question of the desirability of abolishing the word ‘‘ butterine ” in favour of ‘‘ margarine ” or ‘‘ oleomargarine.” I stated that all were equally unscientific, and that ‘‘ butterine ” being now a generally accepted name for butter-substitutes, I saw no reason for prohibiting its use, provided that a clause were inserted in the Bill making it illegal to cover up or hide in any way the terminal letters.I stated that, according to my recollection, (( oleomargarine ” was the original name given to the finished article or factitious butter, though it might now be employed to designate an intermediate product. Still, “ oleomargarine ” is recognised as the ordinary name for butter-substitutes in America, and has recently been made compulsory all over the United States. Hence we have the anomaly that an article will be exported from New York as oleomargarine," and on arrival at Liverpool the same name, according to Sir Frederick Abel and Mr. Lovell, has ceased to be applicable to it, is not correctly descrip- tive of it, and the article henceforth becomes “butterine.” Whatever name be ultimately legalised for finished butter-substitutes generally, it is evident that the name ‘( oleomar- garine ” is not obsolete, and has not the limited application attributed to it.In the course of my examination I expressed the opinion that special legisla tion with respect to butter-substitutes was desirable, as there was no other article of an exactly parallel nature, except factitious wine. Thus, mixed coEee, adulterated pepper, and watered milk, contained some of the article under the name of which they were sold ; but butterine often contained no real butter, except perhaps the trifling pro- portion added to give it a characteristic flavour. He stated that the mixhgof butter with butter-substitutes was a manufacturer’s operation, and was rarely praclised by the retailer, and in instances within his knowledge the retailer had been misled by the wholesale dealer as t o the nature of the article supplied to him.Mixtures con- taining a considerable proportion of real butter had recently become very common, and these mixtures he would wholly prohibit, asmuch increasing the tendency to fraud. He would not allow real butter to be added to a butter-substitute, except in the trifling pro- portion in which i t is employed to communicate a butter flavour. I do not know how the trade would regard this, but it would certainly get rid of a11 difficulties for the analysts. A similar provision is contained in the German Butter-Substitutes Bill now under consideration. Our friend Mr. OTTO HEHNER was the next witness. Dr. JAMES BELL, of the Inland Revenue Laboratory, was the first witness examined on the re-assembling of the Committee on June 7th. He considered the retailer should always be the person proceeded against, even if he could shorn that he had been deceived126 TEE ANALYST.by the wholesale dealer. He recommended that an inspector should ham the power to go into any butter-store, either wholesale or retail, and take a sample for analysis of any article of the character of butter, which was not distinctly labelled by the name which might be eventually adopted for butter-substitutes. In other words, the failure to label a butter-substitute as such should be made an offence, even when no sale took place. This appears to me a very valuable suggestion, and it is satisfactory to find that it met the approval of a subsequent witness, Mr.Lovell, who spoke on behalf of the wholesale butterine merchants. Dr. Bell did not approve of the proposed employment of Inland Revenue officers, and saw no object in providing for the taking of samples in transit. He thought it unnecessary to insist on any general name for butter-substitutes, and would not take the responsibility of suggesting one. Some questions were put to Dr. Bell by Mr. Mchren, relative to a letter of mine in the St. James’s Gazette, describing the objections of public analysts to the present system of reference of perishable articles to Somerset House. The portion of my letter bearing more particularly on the point was a9 follows :- “But a far graver cause of the inefficiency of the Sale of Food and Drugs Act, especially with regard to milk and butter, is the position of the Somerset House chemists, who are appointed referees under the Act.These gentlemen are placed in a very disagreeable and invidious position. Thus, they are required to certify whether the condemnation of a sample by a public analyst was correct, when it very frequently happens that they are not in a position to certify either one way or the other, But, instead of stating this in their certificates, these gentlemen consider it their duty to give the benefit of any doubt which may exist in their minds to the vendor of the article. The wording of their certificates has commonly been that they were ‘ unable to affirm that the sample in question was adulterated ; ’ thus leaving $he magistrates to imagine that they affirmed it to be unadulterated, whereas what they actually meant was that, from decomposition or other circumstances, they could not form any positive opinion on the matter.That this is frequently the case is evident from the fact that it has often been five or six weeks before the sample in dispute has reached their hands. Naturally, under such circumstances, no reliable analysis of milk has been possible; and, although the referees have attempted to avoid the difficulty by making an allowance for change in the milk according to the number of days it has been kept, it is evident that, without a knowledge of the circumstances and temperature under which it has been kept, whether the bottle was wholly or partially filled, and whether the milk was originally watered or not, any such corrections are of a wholly worthless character.Similarly, Dr. Bell, the head of the Somerset House laboratory, has published figures which show that a genuine butter is liable, by keeping for six or seven weeks, to undergo such changes as to make the analyrsis unreliable. It is, therefore, much bo be regretted that the chemists appointed as referees under the Act should not definitely state these facts in their certificates, instead of leaving it to be inferred that the analyst who analysed the milk or butter when in a fresh condition had been in error. I may point out also, with every personal respect for the Somerset House chemists, that the assumption that they are bound to give the benefit of any doubt to the defendants is not in accordance with their position &s impartial referees.It is their duty to state fairly the result of their analysis, and whether from it they believe the milk to have been adulterated. I f they cannot speak with certainty, they might speak of probabilities; and, if they cannot make up their minds a t all, they should say so candidly, and leave the course of giving the benefit of any doubt to theTHE ANALYST. 127 Bench in the usual manner, and not exercise the prerogative of mercy them- selves. “ It must further be borne in mind that the number of cases in which the analysts’ certificates are disputed, and which therefore are referred to the Somerset House chemists, are very small, amounting only to a dozen or two of all kinds per annum. Hence the experience of Somerset House of such kind of work is necessarily limited, and the chemists there have no incentive to keep themselves en rapport with the advance of food analysis, in which public analysts are so much interested.One of the practical effects of this is that the Somerset House chemists habitually express themselves ‘ unable to affirm the fact of the adulteration ’ of butter with butterine when it occurs to a less extent than 35 to 40 per cent. j whereas public analysts are able to detect with absolute certainty something like half this proportion. Bearing in mind, however, the damage to his reputation caused by a failure of the Somerset House chemists to confirm his certificate, the ordinary public analyst is often compelled in self-defence to give a certificate on which no proceedings can be taken, when he is perfectly aware in his own mind that the sample should not be allowed to pass.” On the subject of this letter Dr.Bell gave the following ‘evidence :- “ Q. 551. You have issued statistics yourself, I think, to show that genuine butter is liable by keeping six or seven weeks, to undergo such changes as to make analysis qnreliable ?-A. No, certainly not. If butter is kept for a considerable time it depre- ciates ; but the extent to which it depreciates within the month that it requires to be sent up to us is so infinitesimal that it would not affect any analysis.” “ Q . 552. Is it not the case sometimes that four or five weeks elapse before you make the analysis after the thing is first sent up by the public analyst ?-A.No, not four or five weeks after we receive it.” Q. 553. After it is taken, I mean ?-A. I think that under the present law they are required to send it up within the month.” “Q. 554. Can butter be kept a month and not affected at all ?-A. Not to any appreciable extent .” “ Q . 555. Except as regards flavour ?-A. Yes.” ‘‘ Q. 556. For analysis it is just as good ?-A. Practically the same.” This evidence makes one rub one’s eyes to be sure of being awake! It is simply astounding that Dr. Bell should be so little conversant with that part of the Act for the working of which he is directly responsible as not to know that the interval of time between the purchase of a sample and his receipt of a portion of it in w e of dispute is commonly six or seven weeks, I do not suggest for a moment that Dr.Bell desired to mislead the Committee, but his reply certainly had that effect. Dr. Bell seems to have confounded in an unaccountable manner, the provision in the Sale of Food Amendment Act, under which proceedings in the case of perishable articles must be commenced within twenty-eight days from the time of purchase, with the length of time before he receives a portion of a disputed sample. He wholly ignores the fact that after the issue of the summons a period of not less than seven days must elapse before the hearing, and that in disputed cases there is very frequently an adjournment of the hear- ing for a fortnight or longer before it is decided to refer the sample to Somerset House. And the twenty-eight days allowed for taking out the summons is by no means an excessive time in practice, seeing that many sanitary authorities meet only once a fort- night and do not allow proceedings to be taken except under a special resolution passed by them.128 THE ANALYST.But if Dr. Bell was mistaken as to the provisions and working of the Act, what shall we say of his statement about the change of butter by keeping, in the face of the experiments he records on page 71 of his book 011 the “ Analysis and Adulterations of Foods, Part II,”? There he gives the following data, ( I showing the amount of depreciation which different samples of butter have undergone in the respective times stated ” : - 1. 2. 3. 4. 6. 6. Insoluble acids; original butter. 87.30 87.80 85.50 87.40 87.72 87.65 ?, ,, after keeping .. 88.97 90*00 85-72 87.97 88 40 88-00 $9 ,, increase . . 1.67 2.20 0.22 0.55 0 68 0.35 ------ ------ Length of time kept, in weeks . . 12 7 7 6 8 6 In the most striking case, No. 2, a butter kept for seven weeks showed an increase of 2 20 per cent. in the insoluble acids, the specific gravity at looo Fahr. a t the same time falling from 911-58 to 909.19. It would be interesting to learn from Dr. Bell how in the face of such a result he can state that he has never issued statistics showing that genuine butter, by keeping for six or seven weeks, is liable to undergo such changes as to make analysis unreliable, and that the depreciation in a month is so infinitesimal that it would not affect any analysis. Of course all analysts know that such figures as were obtained by Dr.Bell, after keeping No. 2 sample for seven weeks, are such as indicate a notable adulteration, but having obtained them it is easy to understand how it comes that Dr. Bell fails to detect adulteration of butter even in cases where the admixture may exceed thirty per cent. Personally, I have no confidence in the figures in question, and doubt if butter is liable to undergo the rapid change found in the case of No. 2 sample; but Dr. Call is in a different position. I f he maintains the accuracy of his reply to Q. 561 it is a distinct repudiation of his analyses on page 71 of his book. Dr. Bell’s examination then proceeded as follows :- “ Q . 557. Is it the case that the wording of the certificate from Somerset House frequently is simply that you are unable to affirm that the sample in question is adulterated ?-A.That is so in the case of milk; we have not a certificate in the case of butter worded in that form.” I confess that this reply surprised me, as I was not aware that the objectionable ‘‘ Q. 558. A certificate like that of course leaves the whole thing perfectly vague 1 -A. It leaves the magistrates to deal with the question.” “ Q. 559. Does it not rather give a presumption against the local analyst ?-A, No, I do not see that it does; the terms are rather in favour of the public analyst.” “ Q. 560. 1: should have thought they were against him ?-A. Decidedly not ; it leaves the magistrates either to accept our certificate or not.” “ Q . 561. I am informed that the local analysts feel that that phrase is rather against them, and that, in cansequence, public analysts are often compelled to give certificates on which no proceedings can he taken for fear of your sending down this vague report, when, in reality, they are perfectly aware in their own minds that the sample should not be allowed to pass ?-A.The public analysts are pretty well aware inability t o affirm the fact of adulteration ” was limited to milk certificates.THE ANALYST. 129 now-a-days that they need have no dread of our interfering with their analyses, provided they have kept within a reasonable limit and made an accurate analysis.” “ Q . 562. Then you think that no damage is done to the public interest by long delay in getting the Somerset House decision.-A. No.” I intend in my next batch of quarterly reports to state that Dr.Bell considers the expression we are unable to affirm the fact of adulteration ” of milk to be rat.her in favour of the public analyst, and that it leaves the magistrates either to accept the Somerset House certificate or not. I should recommend all other public analysts to follow my example. Mr. JOHN CARP LOVELL waa the next witness. He said he had had great experience as an importer and distributor of butter-substitutes. He restricted the term oleomargarine to the manufacturer’s intermediate product. He thought the sale of butterine for butter should be put a stop to. He apparently had every confidence in public analysts, and approved of Dr. Bell’s suggestion that an inspector should be allowed to take, without purchase, sa-mples of apparent butter not having a butterine label.All butter-substitutes sold retail should be wrapped in descriptive labels, and the word ‘‘ butterine ” should be branded on all kegs and mses. By inflicting sufficiently heavy fines, and even imprison- ment for repeated offences, the fraudulent sale of butter-substitutes would soon caase. He would apply the term butterine to everything but genuine butter. The Committee will meet again on June loth, when representatives of the whole- sale and retail butter-trade will be heard.” He objected to the suppression of the word butterine. Speaking generally, the provisions of the Bills which public analysts thought mcst objectionable have little chance of becoming law, and if the suggestion of Dr. Bell with respect to taking samples without purchase be adopted, the Act will be of decided public benefit.The attention of the Committee has been directed by letter to the method of deal- ing with suspected milk in Derbyshire, for which county Mr. Hehner and myself are joint analysts. In the case of either of us having a sample of milk believed to be adulterated, he sends it without delay to the other, who also gives a certificate on it (at half fee), so that there are two independent analyses made of the fresh, or nearly fresh, milk. This course practically precludes all chance of error on the part of the analyst, and is a f a r more satisfactory way of checking him than by sending the milk to Somer- set House, when five or six weeks old, and when, therefore, it is quite impossible to make any trustworthy analysis of the sample.As an illustration of this I may state that in a recent case an analyst certified to 16 per cent. of added water in milk, and his certificate being doubted, the sample was sent to Somerset House, whence a certificate was returned stating that the milk was adulterated with 40 per cent. of added water ! The discrepancy is an indication of the value of the Somerset House “allowance for change by keeping.” Mr. HARLAND said that there are in London makers of oleornnrgarine simply, and other fims who mix oleomargarine with oil or milk and produce the articlo butterino. Recently he had had to examine a number of butters as they came into London. A good many brands had been warranted genuine and suspicion had arieen about them. * The witnesses examined on June 10th gave evidence merely of trade interest.130 THE ANALYST. As a matter of fact, more than 50 per cent. of them contained from 30 to 60 per cent. of butterine ; they were branded or warranted genuine and had the name of a respectable trader attached. Dr. MUTER said he could confirm the President’s recollection that the term oleo- margarine was originally applied to the finished product, and not limited to the intermediate article as it now is by some traders. The President announced that the country meeting of the Society would be held at Leamington, on Friday, the 22nd inst., and full particulars would be duly announced. The papers read as above noticed will be published in THE ANALYST for next month, VISIT OF THE SOCIETY TO THE FARMS OF THE AYLESBURY DAIRY CO. ON Thursday, the 9th June, the members of the Society who were in London, for the previous evening’s meeting, journeyed into Surrey, to visit the above Company’s dairy farms, when a very interesting day was spent. A full account of this visit will appear in our columns during the recess.

ISSN:0003-2654    

DOI:10.1039/AN887120123b

出版商:RSC    

年代:1887

数据来源: RSC

摘要:

130 THE ANALYST. TESTING SKIM-MILK BY THE LACTOCRITE. BY HARALD FABEB. Read at the Meeting, April, 1887. IN a previous paper on the Lactocrite I tried to prove how very exact results may be obtained when determining the amount of fat in whole milk by means of this apparatus, and how easilyit is worked. I mentioned that the results obtained, when testing skim- milk, would fall too low, and by two examples I showed that the difference is about 0.1 per cent., when the skim-milk contains about 1.0 per cent. of fat; I shall now give the results of some experiments on milk containing still less fat, viz., skim-milk from very close hand skimming and from cream separators. I mentioned that the differences between the Lactocrite and analysis are found to be about 0.2 per cent. for separated milk, the result of a series of experiments carried out in Sweden being :- Chem.Analysis. Lactocrite Difference. 0.50 0.30 0-20 0.50 0.29 0.21 0.43 0.20 0.23 0.36 0.10 0.26 0.34 0.13 0.22 0.26 0.05 0.21 0.1 9 0.00 0.1 9 0.19 0.00 0.19 My own experience showed me that sometimes the difference was still larger, some- times also less, making the use of the Lactocrite for testingseparated milk rather doubt- ful. Besides, when the Lactocrite shows no fat, it is impossible to know how small an amount has been left by the skimming. In one case I found, in testing a milk contain- ing 0.31 per cent. of fat, that the Lactocrite showed only a trace which could not beTHE ANALYST. 131 measured, so that separated milk with less than 0.3 per cent. of fat can not be tested at all.The reason why the very small amounts of fat, so to speak, disappear, I cannot give. It might be imagined that the boiling with acid would attack the small globules, and in separated milk only the very smallest globules are left; but if that was the case it would seem very strange that so exact results are obtained with whole milk, as the size of the globules varies much in different samples of milk, and especially in milk from Merent breeds. Six sclmples of the same separated milk, containing 0.49 per cent. of fat, were tested in the Lactocrite, three of them being boiled with acid for only four minutes, the other three for eight minutes. The following experiment seems also to controvert this theory :- The results obtained were as follows :- Boiled 4 min S min.Per cent. of fat found 0.2 0.2 19 0.2 0.25 ,,*a 0.25 0.25 If the acid did attack the fat, less fat, ought to be left after the longer boiling with acid, which was not the case. It may seem of little interest to be able to estimate such small amounts of fat with very great m u w , but in butter dairies it will be found of the greatest importance. Farmers look for help and information from agricultural chemists, and chemical analysis can hardly benefit the dairy farmers more than by teaching them how t o skim the milk thoroughly with a separator, if they go in for buttermaking; as by a well-worked good separator the milk may be made to produce 20 per cent. more butter than by the old system, in some cases even considerably more. But this is only done when the sepamtar is made to skim the milk thoroughly, which alone can be controlled by a test of the amount of fat left in the skim-milk.Seeing how great a service the Lactocrite might yield the buttermaker, if it could be made to test the sepamted milk with sufficient exactness and in a simple way, I tried to alter the method of working, and finally found that by using it in the same way as the (( Control Centrifuge ” of Professor Fjord (see ANALYST of January) very satisfac- tory results could be obtained. The method I use is still easier than the ordinary working of the Lactocrite. All t h t is required is to fill the test-boxes with the skim-milk until it reaches about half- way up on the graduated glass, and then place them in the warm disc and make this revolve.It take a longer time for these very small globules to rise in milk not treated with acid, so that separating for twenty or thirty minutes will be necessary. After that time a column of crmm is found in the graduated glass, which it is very easy to read off. This cream, however, does not directly give any information of the amount of butterfat in the skim-milk; a calculation is necessary. I have found that multiplying the degrees of cream [each degree corresponding to 0.1 per cent. of fat when testing whole milk] by the factor 0.03 gives the per centage of fat in the skim- milk with remarkable correctness. Below are the results of fourteen samples, resulting from eleven different sepmtings of different milks, separated by dXerent separators :-132 THE ANALYST.Per cent. of fat by Analysis. 0.08 1.01 0.13 0.22 0.24 0.25 0.28 0.3 1 0.31 0.32 0.35 0.51 0.55 0.76 Degree of cream by Lactocrite. 21 4 7 8 9 11 13 15 168 l2 79 9$ IS$ 22h Degree of cream x 0.03. Difference. 0.075 0.005 0.03 0.08 0.1 2 0.01 0.21 0.01 0.225 0.015 0.24 0.01 0.27 0.01 0.285 0.025 0.33 0.02 0.39 0.07 0.45 0.10 0.495 0.045 0.555 0.005 0.675 0.055 Average 0.007 Numeric average 0.031, Only in four cases is the difference larger than 0.05, which I consider the difference to bs guaranteed by chemical analysis, if this shall claim to be exact. It is, perhaps, not so very strange that tolerably uniform results should in this way be obtained by a test, based on the ‘‘ cream,” which is otherwise not a very uniform product. For, in the first place, the centrifugal force, when, acting strongly for half an hour, is well able to cause all the globules to rise, and pack them closely, and secondly, these globules, including (in separated milk) only the very smallest, are of much more uniform size than the globules in whole milk. At any rate the number of requirements seems sufficient to prove that, worked in this way, the Lactocrite may be used as a practically reliable test for skim-milk. By means of the Lactocrite, therefore, a dairy farmer may examine the working of a separator before buying it, and he may at any time test whether his milk is skimmed so closely as to give him the largest possible yield of butter, since he will be able to perform in a short t h e a sufficiently correct analysis of his skim-milk at very little cost. By this machine, therefore, may be established a control which hitherto h&s been largely neglected. Conclusion of the Society’s Proceedinp.

ISSN:0003-2654    

DOI:10.1039/AN8871200130

出版商:RSC    

年代:1887

数据来源: RSC

摘要:

132 THE ANALYST. A METHOD FOR THE SEPARATION AND ESTIMATION OF BORIC ACID. With an Account of a Convenient Term of Apparatus for Quantitative Distillations. BY F. A. GOOCH,~ (Continued from page 94.) To bring the matter to the test, the following experiments were made. In them and in all succeeding experiments the boric acid was weighed in solution, the standard of this having been fixed by dissolving in a known weight of water a known weight of fused boric anhydride prepared in a state of purity by frequent recrystallisation. The magnesium oxide employed was made from the pure chloride by precipitating by * American Chemical Journal.THE ANALYST. 133 ammonium carbonate and igniting, and was free from lime and alkalies, and, 88 far as could be determined, otherwise pure.The whole operation of each experiment was conducted in one vessel, so as to avoid transfers. In all cases a weighed platinum crucible of 100 C.C. capacity received a weighed portion of magnesia, and after ignition and subsequent weighing the weighed solution of boric acid was introduced. In experi- ments (1) to (4) the magnesia was thoroughly stirred in the solution of boric acid, the evaporation carried at once to dryness, and the crucible and residue ignited and weighed ; in experiments ( 5 ) to (8) the magnesia was dissolved, after the addition of the boric acid, in hydrochloric wid sdicient in amount to prevent the precipitation of magnesium hydrate on the subsequent addition of ammonia, ammonia introduced in considerable excess in (7) and (S), in distinct excess in (5) and (6), the whole evaporated and ignited, the residue moistened and again ignited, and this last treatment repeated until the residue ceased to yield vapour of hydrochloric acid when heated.MgO + R,O, B,O found. found. taken. Gram. Gram. Gram. Gram. (I) 0.1’734 0.5005 0.6607 0.1602 (2) 0.1804 0.4913 0.6660 0.1687 (3) 0.1793 0.4949 0.6640 0.1691 (4) 0,1794 0.4941 0-6627 0.1 686 (5) 0*1807 0,4984 0.6542 0.1558 (6) 0.1’789 0.4974 0-6687 0.1 560 (7) 0.1806 0.4944 0,6684 0.1 740 (8) 0.1789 0.4959 0.6672 0.1713 MgO taken, B203 i Error. Gram. 0*0132- 0.0117- 0*0102- 0*0108- 0,0249- 0*0229- 0,0066- 0.0076- From these results it appears plain that under the conditions of the experiment& neither magnesia alone nor the magnesia mixture is efficient in fixing boric acid ; but in experiments (’7) and (8), in which ammonia was employed in large excess, the loss of boric acid is least, so that it would seem to be the case that though ammonia is not a perfect preventive of volatilisation, it does exert a restraining action on the boric acid, That the magnesia mixture should be incapable of retaining entirely the boric acid present is, as has been pointed out, not surprising ; but that the loss should be so great is rather startling, and more than suggests that the errors of Marignac’s process are seriously excessive.The failure of magnesium oxide to hold back boric acid under the conditions of the experiment must be due to a cause other than that which determines the loss during the evaporation and ignition of the magnesia mixture, and for this it is natural to turn to the insoIubiIity of the oxide-a quality likely to oppose some diiliculty in the way of establishing complete contact between the boric acid and the magnesia during a short exposure.Direct tests of this point showed distinctly that mixtures of boric acid in water and magnesia, when submitted at once to distillation, yielded boric acid to the distillate ; but that, if the mixture were permitted to stand some hours before distilling, the oxide passed to the semi-gelatinous condition of the hydrate, and retained the boric acid so firmly that turmeric failed to show the presence of the latter in the distillate. It is plain, therefore, that with sufficient preliminary exposure magnesia might be relied upon to retain boric acid; but inasmuch as long and perhaps somewhat indefinite periods of waiting are objectionable in any analytical process, it was thought be& to try the effect of substituting lime for magnesia.Experiments (9) to (12), con134 THE ANALYST. - - ducted like the previous ones, excepting only the use of carefully prepared and ignited calcium oxide instead of magnesium oxide, were made with this end in view. B2O Error. CaO CaO f B,O, taken. found. found. taken. Gram. Gram. Gram. Gram. Gram. (9) 0-1810 0.9737 1.1560 0.1823 0.0013 + (10) 0*1819 0.9750 1.1583 0.1833 0.00 14 + B,O, (11) 0.1808 0.9922 1*1810 0*1818 0~0010 + (12) 0,1833 0-9715 1.1560 0.1845 0*0012+ These figures indicate sufficiently that there is no loss of boric acid by volatilisation when its aqueous solution is evaporated in contact with calcium hydrate ; but, inasmuch as the comparative solubility of the latter ~EI the quality which makes it effective where magnesia is not, it seemed desirable to test the action of calcium hydrate in alcoholic solutions, in which it is very insoluble.The experiment showed that when the solution of boric acid in methyl or ethyl alcohol is put upon lime and distilled at once, loss is apt to take place, and sometimes to a very considerable amount, but that a short period of digestion, with occasional stirring-from five to fifteen minutes--% sufficient to obviate danger of volatilisation of boric acid. It appears, therefore, that, free boric acid being easily uolatilised by means of methylalcohol and fixed completely by calcic hydrate, the separation of the acid from almost everything with which it occurs ordinarily, and its estimation subsequently, depend only upon the practicability of distilling it from its compounds in such company that it may be retained by lime, and its amount determined by the increase in the weight of the latter.Unlike magnesium chloride, calcium chloride does not yield its chlorine readily under the action of heat and moisture naturally retained; so that hydrochloric acid must not be present with boric acid, which is to be estimated in the manner described. Calcium nitrate and calcium acetate both yield the oxide without dXculty upon ignition, and nitric and acetic acids are suitable agents, therefore, for the liberation of boric acid previous to distillation.The actual distillation presented at first some difficulty-for the repeated, thorough, and rapid, evaporation of a liquid charged with soluble or insoluble solid matter is apt to involve some mechanical transfer to the distillate of material which should remain in the residue-but the device of the following description solves the problem sums- The apparatus, which is shown in the accompanying cut, consists essentially of a retort, condenser, and bath for heating. For the last I have used a p a r a n e bath, as being on the whole the most convenient. The condenser is set vertically, to facilitate changing the level of the retort within the bath, and to secure at the same time con- tinual and thorough washing of the tube by its own condensations.The retort, some- what like the well-known drying-tube of Liebig in general h p e , is easily made of a pipette by bending the tube at one end to a right angle, at the other to a goose-neck, as shown. To the former end is fitted, by a rubber stopper or section of tubing, a glass funnel-tube provided with a stopcock; the end of the goose-neck pwms tightly through a rubber stopper in the upper end of the condensing tube. This is essentially the apparatus, but it is convenient to attach to receive the distillate a small Erlenmeyer fully.THE ANALYST. 135 flask, which moves with the condenser and is joined to it, in the manner indicated in the figure, by means of a thistle-tube and a rubber stopper, grooved to permit the free passage of air. In carrying out a distillation, the liquid to be distilled is introduced into the retort, either by the funnel-tube or previous to its insertion; the glass cock is closed, the water started through the condenser, and the retort lowered into the hot paraffine, care being taken to begin the operation with the retort not more than haIf full, and so inclined that only the rear dips below the surface of the bath.I f the precaution to heat the retort a t the start in this manner be overlooked, it may sometimes happen that the sudden and violent expulsion of air through the liquid will .carry portions of it bodily into the goose-neck, and even into the condenser. With this point considered, the remainder of the operation presents no d a - culty, and requires little care. The size of the retort may be suited, of course, to the particular case in hand, but for most purposes a 200 C.C.pipette makes a retort of convenient dimensions, neither too large for the distillation of small charges nor too small to permit the treatment of 100 C.C. of liquid comfortably. The tube of the goose-neck should be wide enough to prevent the formation of bubbles in it; 0.7 C.C. is a good measure for the interior diameter. It is of advantage to heat the bath to a point considerably above the temperature a t which the liquid which is to be distilled boils-something between 130°C. and 14OOC. does very well for water, and is not too high for methyhlcohol-and under such circumstances, and when the retort is entirely submerged, it often happens that evaporation takes place with extreme rapidity from the surface of the liquid in perfect quiet without actual boiling.With such an apparatus the following experiments were made :- The boric acid was weighed as before in solution, and, to bring the condition of the experiment to that of an actual analysis, 1 grm. of pure sodium hydrate was added in solution, nitric acid or acetic acid to acidity and a little more, and the whole was intro- duced into the retort and distilled to dryness. In those experiments in which nitric acid was employed, the methylalcohol was introduced upon the residue thus dried in six successive portions of 10 C.C. each, and distilled to dryness; but in order to break up the residue of sodium nitrate, which by its insolubility might effect to some extent the protection of the boric acid from the action of the alcohol, 2 C.C.of water were introduced and evaporated between the second and third, and again between the fourth and fifth, distillations. When acetic acid was made use of to free the boric acid, the six distillations with136 THE ANALYST. methylalcohol were made as before ; but sodium acetate being soluble in methylalcohol, the intermediate treatments with water were unnecessary. With the fourth portion of methylalcohol a few drops of acetic acid were added to preserve the acidity of the residue, which, as has been pointed out, tends to become alkaline under the treat- ment. The residues of both processes of treatment were found to be free from boric acid, by the exceedingly delicate test with turmeric, care being taken, in the series of experi- ments in which nitric acid was used, to oxidise nitrates by means of bromine (expelling the latter before making the test), and in the acetic acid series to acidify with hydro- chloric acid sufficiently to counteract the tendency of the acetate by itself to brown the turmeric on evaporation.The lime to retain the boric acid in the distillate was ignited in the crucible in which the evaporation of the distillate was to be made subsequently, and then trans- ferred to the receiving flask attached to the condenser, so that the boric acid might be fixed during the distillation. To prevent the caking of the lime by the action of the alcohol, it was slaked with a little water before the distillation was begun. In experiments (13) to (16) nitric acid was employed, and in (17) to (20) acetic acid was used, with the precaution noted, to liberate the boric acid.B,03 + CaO BBO3 Error. B*03 CaO taken. taken. found. found. Gram. Gram. Gram. Gram. Gram. (13) 0.1738 (14) 0.1806 (15) 0.1779 (16) 0.1824 (17) 0.1806 (18) 0.1812 (19) 0.1788 (20) 0-1813 0.9647 0.0639 0.9665 0.9739 1 *4559 0.9720 0.9986 0.9537 1.1392 1.1456 1.1450 1.1587 1.6371 1.1543 1.1781 1.1358 0.1 745 0*1817 0.1785 0.1 848 0.1812 0.1823 0,1795 0,1831 0*0007 + 0*0011+ 0.0006 4- 0*0034+ 0*0006 + 0*0011+ 0.0007 + O.OOlS+ I n experiments (13) to (16) the mealz error amounts to 0.0012 -c grm. ; in ex- periments (17) to (20) the mean error is a little more than 0*0010+ grm. Throughout the entire series of experiments the tendency to yield figures slightly larger than the truth is manifest, but the error is quite within legitimate limits. The greatest care was taken to secure similarity of conditions under which the crucible and lime were weighed, before and after the evaporation and absorption of boric acid, and the weight after ignition was taken in every case after cooling over sulphuric acid during a definite period of ten minutes, in order to eliminate as far as possible the effect of atmospheric condensation upon the large surface of platinum.Ignitions were always finished over the blast-lamp, and constancy of weights secured. The results of both modes of treatment aro on the whole sakisfactory, and equally so. In the presence of chlorides, it is of course impossible to employ nitric acid to free the boric acid.Oxalic, citric, and tartaric acids also liberate hydrochloric acid to a con- siderable extent from alkaline chlorides. It was found, however, that when acetic acid was distilled over sodium and pobsium chlorides, only traces of hydrochloric acid passedTHE ANALYST. 137 into the distillate, and experiments (21) to (23) were made to determine whether these amounts are sufficient to vitiate the separation of boric acid from alkaline chlorides by distillation in presence of free acetic acid. The details of treatment were identical with those of experiments (17) to (20), excepting only the addition of 0.5 grm. of sodium chloride to each portion before distillation. CaO B,03 + CaO BB03 Error. taken. found. found. taken, Gram. Gram. Gram.Gram. Gram. BB03 (21) 0.1834 0.9842 1 *1675 0.1833 0*0001- (23) 0.1761 0.9740 1-1523 0.1 783 0.0022 + (22) 0.1831 0.9755 1-1593 0.1 838 0*0007 + The mean error of these results is about 0*0009+ grm., and it is plain that the presence of sodium chloride does not materially change the conditions of the experiment. There seems, therefore, to be no reason why boric acid may not be separated by distilla- tion from alkaline chlorides in presence of free acetic acid; but it was found that the presence of any considerable amount of potassium acetate is disadvantageous. Sodium acetate to a reasonable amount does not interfere with the favourable progress of the separation ; but potassium acetate appears to require a much higher temperature for the expulsion of its water, and longer distillation.When, therefore, chlorides are present in the salts from which boric acid is to be removed by distillation, the choice is open between two methods : The distillation may be made directly with an excess of acetic acid; or the hydrochloric acid may be first removed by means of silver nitrate, and the distillation of the filtrate proceeded with, at once, or after precipitation of the excess of silver salt by means of sodium hydrate or carbonate, care being taken to acidify again sufficiently with nitric acid after the removal of the silver. Of these two modes of proceeding, I incline to the treatment with nitric acid, and the removal of the chlorine by precipitation ; and this method has been used with success by others well as myself, for some months, in the analysis of waters carrying boric acid, and natural borater;l.The process in either modification is fairly accurate and easily executed, and admits of very wide application. Insoluble compounds in which the boric acid is to be deter- mined may be dissolved in nitric acid at once, or, if necessary, first fused with sodium carbonate ; and, fortunately, nearly everything which is volatile in the subsequent treatment, and capable of forming with lime compounds not easily decomposable by heat, may be removed by known processes. The combination of fluorine, silica, and boric acid is perhaps most d s c u l t to treat; but the precipitation and removal of the first as calcium fluoride from the aqueous solution of a fusion in alkaline carbonate may, it is believed, be effected with care, and the mode of procedure from that point is simple, The number of distillations necessary depends, of course, upon the amount of boric acid treated. To remove 0.2 grm. of boric anhydride completely to the distillate, six charges of methylalcohol, of 10 C.C. each, proved, as we have seen, to be ample. The apparatus, by the aid of which the distillation processes which have been described were carried out, has found useful application in a number of other processes. In the determination of free and albuminoid ammonia in waters which can be boiled138 THE ANALYEIT. quietly with difficulty, in the methods of estimating hydrofluoric acid which involve the expulsion of silicon fluoride from a mixture of the fluoride with sulphuric acid and silica, in the separation of iodine from bromides and chlorides by distilIing with ferric sulphate and sulphuric acid, and of bromine from chlorides by means of permanganic acid, it has proved of value, and will doubtless be found convenient in many analytical processes in which quantitative separations by the distillation of liquids liable to spatter or boil explosively are involved.

ISSN:0003-2654    

DOI:10.1039/AN8871200132

出版商:RSC    

年代:1887

数据来源: RSC

摘要:

138 THE ANALYEIT. A NEW PROCESS FOR THE QUANTITATIVE ESTIMATION OP STARCH." BY PROF. DR. ALEXANDER v. ASB~TH. I HAVE often had occasion to try the various processes for estimating starch, and at one time used the process of Allin, until Marcker and Delbruck pointed out the results obtained by direct inversion are too high, as cellulose is also partly converted into sugar. Marcker proposed in 1885 to first heat the cereals with diastase, which, under favourable condi- tions, rapidly liquefies the starch. The filtered fluid may then be inverted by hydrochloric acid. In theory this process seems very convenient, but in practice it is very difficult of execution. First of all, the cereals must be finely ground, which with maize is a very diilicult matter; then the liquid must be rapidly filtered whilst still hot, otherwise particles of starch will again separate out on cooling, so the operator is always in doubt whether all starch is in the filtrate.A single experiment is, therefore, not to be depended on, but from three to four trials must be made, which takes too much time. The great error in all these methods is, however, caused by the necessity of inverting the starch, which is always attended with loss. Franke has already, in 1882, called attention to the partial decomposition of starch when heated under a pressure of 3-3.5 atmospheres, Maltose gave a loss of 7*4 per cent. My own experiments also prove the decomposition of sugar, both by high pressure and by inversion. For these experiments I have used pure glucose (99.84 per cent.). On treating this first, according to Marcker's process, and boiling for two hours and a half, there mas a loss of 3-84 per cent.sugar. In a second experiment, I first boiled with 30 C.C. of a 1 per cent. solution of lactic acid, under a pressure of 3-3*5 atmospheres, then again with 200 C.C. of water, and 20 C.C. of hydrochloric acid, when the loss amounted to 8-54 per cent. Messrs Conrad and Guthreit have proved that dextrose, and more still, levulose, are completely decom- posed by prolonged boiling with 7 per cent. hydrochloric or sulphuric acid in humic acid, acetopropionic acid and formic acid. After warming 9.5 grammes of cane-sugar with 800 C.C. water and 072 grammes hydrochloric acid for half an hour, Soxhlet did not notice any loss, but on boiling for some time he found a serious diminution of sugar.I t is therefwe plain no satisfa;ctory determination of starch can be made by any process bmed on, i nversion,. I therefore tried my best to estimate the starch by a direct process, and took advantage of a reaction first noticed by Zulkowsky, viz., the behaviour of starch towards baryta water, which yields an insoluble precipitate. My first efforts were now directed to ascertain the actual composition of this body, also to see whether it is constant. I * Fiepert. Anal. Chemie, No. 20.THE ANALYST. 139 - therefore first prepared a soluble potato starch according to Zulkowsky’s directions, and mixed its watery solution with excess of bar+ water. After the precipitate hadsettled I syphoned off the supernatant fluid, and washed the deposit with alcohol of 45 per cent., until all alkalinity was removed. The baryta starch is insoluble in excess of baryta and in weak alcohol, though slightly soluble in pure water.After collecting precipitate on a filter, and washing a few times with ether, I then dried it and made an analysis. 2.0275 grms. were dissolved in hot weak hydrochloric acid, and the liquid made up to 250 C.C. 50 C.C. were then precipitated with sulphuric acid, the precipitate treated and weighed as usual, and calculated to baric oxide. I now found the amount of base to be 19.97 per cent., which fairly well agrees with the formula- which requires 19.10 per cent BaO. c24 Ha 0 2 , BaO The slight excess of BaO is due to a small admixture of barium carbonate.Further experiments proved a similar precipitate is formed, even when the starch is merely in the state of paste, and not actually dissolved. Wheat starch, boiled with water for half an hour, yielded with baryta a compound containing 19.8 per cent. BaO. The gravimetric estimation being too difficult, -L: thought the best and simplest way would be to dissolve the starch, then to add a definite amount of baryta water of known strength. To com- pletely separate the compound I added proof spirit to a definite volume, and afterwards titrated an aliquot part with decinormal hydrochloric acid. As baryta water quickly absorbs carbonic anhydride and gets turbid, I made use of a special apparatus (see illustration), which will not need a detailed explanation. Sufficient to say the tube connected with the jar A is filled with quick- lime, whilst the tube n contains small lumps of caustic potash.Three grms. of the starch were rubbed in a mortar with 150 ex. water, introduced in a 250 C.C. flask, and heated in waterbath for half an hour, with occasional shaking. After cooling, 50 C.C. of baryta water were added from the burette, the flask corked and well shaken for a few minutes, and finally the contents diluted up to the mark with proof spirit. After ten minutes, it was found easy to pipett off 50 C.C. of the clear fluid, and to titmte the excaw of BaO with decinormal hydrochloric acid, using phenolphthalein as indicator. The interval during the settling of precipitate I utilised in standardising the baryta wafer. The difference in BaO between the two determinations wm b t multiplied by 5 then by 4.32 =amount of staroh, The following test andyms show the accuracy of the method :-140 THE ANALYST.PURE WHEAT STARCH. Moisture. Ash. Starch (by difference). Starch (found). MAIZE STARCH. 15.03 - 15.07 -08 84.89-84.85 84*32- 84.52-84.65 Moisture. Ash. Starch (by difference). Starch (found). 13.83 -06 86.11 85.65-85.85 POTATO STARCH. Moisture. Ash. Starch (by difference). Starch (found). The deficiency in starch (about 3 per cent.) is partially accounted for by impurities. I now proceed to give the details of the process when applied to cereals. In every The samples must be finely 18-03 *28 81.72 78*7-78.57 This sample did not dissolve clear in acids. case I have made a full analysis of the other constituents.ground in a coffee-mill. ESTIMATION OF THE STARCH. Weigh out about three grms. of the flour, and rub well in a mortar with ,cold water ; but in the case of hard substances like maize, rice, peas, boiling water must be used. Pour off into a 250 C.C. flask, and rub residue again and again with small quanti- ties of water, until the bulk of the starch is removed ; finally introduce residue also into the flask. Add water up to about 100 c.c., and heat in waterbath for half an hour, with occasional stirring. After cooling, add 50 C.C. of standard baryta water ; cork the flask, and shake well for two minutes. To completely separate the baryta starch, add proof spirit up to the mark. After ten minutes pipette off 50 c.c., but if a floculent precipitate refuses to settle, filter a portion of the fluid through glasswool contained in a tube.I use 10 C.C. baryta water, and add 50 C.C. of thoroughly boiled distilled water before checking it. I must call attention to the fact that if the liquid is not frequently shaken during the heating, there will be a tendency to form lumps of starch paste, which are but imperfectly acted on by baryta water. 1. MAIZE. Difference 12.6 C.C. acid = 68-04 per cent. starch. The titration and calculation have already been described. An analysis can be finished in about an hour and a half. The following results have been obtained with various cereals * :- (a) Used 3 grms., 60 C.C. = 19.5 C.C. acid; 10 C.C. baryta water = 32.1 C.C. acid. (6) Used 3 grms. filtrate = 19.5 C.C. acid = 68.04 per cent.starch. (a) Used 3 grms., 50 C.C. filtrate = 20 C.C. acid ; 10 C.C. baryta water = 32.3 C.C. (6) Filtrate = 19.9 C.C. acid = 66.96 per cent. starch. (c) Same as 6. (a) Used 2-75 grms. filtrate = 19 C.C. acid; 10 C.C. baryts water = 30.70 C.C. (6) Used 2.018 grms. filtrate = 22 C.C. acid = 69-83 per cent. starch. (c) Used 2.34 grms. filtrate = 20.8 C.C. acid; 10 C.C. baryta water = 30.8 C.C. 2. BUCKWHEAT (THE HUSK REMOVED). acid. Difference 12#3 C.C. acid = 66.42 per cent. starch. 3. BARLEY. acid. Difference llT C.C. acid = 69.68 per cent, starch. acid = 69-22 per cent. starch. it If dextrine is present., this is also precipitated, and will count as starch.THE ANALYST. 141 4. WHEAT FLOUR. (a) Used 2.936 grms. (by accident a, 6, c, only mixed with 49.8 C.C.baryta water), filtrate = 17.08 C.C. acid, 10 C.C. baryfa water = 30.4 C.C. acid = 73.49 per cent. starch. (b) Used 2.903 grrn., filtrate = 17.23 C.C. acid = 73.52 per cent. starch. (c) Used 2.97 grrn., filtrate = 16-92 C.C. acid = 73.52 per cent, starch. (d) Used 3.032 grm., filtrate = 16.7 C.C. acid = 73-22 starch. (a) Used 3.212 grrn., filtrate = 19.05 C.C. acid, 10 C.C. baryta water = 30.4 C.C. (b) Used 2.969 grms., filtrate = 19.96 C.C. acid, 10 C.C. baryfa water = 30.35 C.C. acid I now proceed to give in detail the methods used in estimating the other con- MoISTuRE.--Weigh in a platinum dish about 5 grms. of the flour, and dry at ASH.-NOW incinerate, and burn to white ash. TOTAL ALBuMINoIDs.-Treat 1 grm. of the flour according to my modification of 5.PEAS. &d =57*24 per cent. starch. =57-29 per cent. starch. stituents. 105°C till constant weight. Kjeldhal’s process (see ANALYST, May, 1886). Multiply percentage of nitrogen by 100 15.5 FaT.-Put 10 grms. of the flour into a filter-paper cartridge, and extract, in a Soxhlet’s apparatus, with pure ether. FIBRE.--Boil 3 grms. with a mixture of 150 C.C. water, and 50 C.C. 5 per cent. aulphuric mid for half an hour. Filter by aid of filter-pump, wash once or twice with water, rinse precipitate back into the beaker, and boil with a mixture of 150 C.C. water, and 50 C.C. of 5 per cent. caustic potash, for another half an hour. Finally collect residue on a weighed filter, wash first with water, then withspirit, then with ether. Dry till constant weight is obtained. As it always contains some mineral matter, incinerate, and weigh the ash, FULL ANALYSIS OF SOME OF THE MORE IMPORTANT CEREALS.Name. Moisture. Ash. Albuminoids. Fibre. Fat. Starch. Total. Maize 12-68 1.78 9-63 1.97 6.12 68.04 100*22 per cent. ** 9’58-9 69 -- -- 68.04 - - Buckwheat (the I 13-23 1.85 13.51 2.24 2.46 66-78 100.07 per cent, husk removed) 66.96 -_ -- -- - -- $9 9 , 66 43 1, 66.96 Barley 13.07 2.65 9.94 2.67 1-99 69.58 99.90 per cent. 19 69.83 -- -- - -- - 69.23 - -- -- __ 69.86 Wheat flour 9.56 1.77 12.51 1.04 1.63 73.43 99.94 per cent. ?, 1.09 - 73.49 1.78 -- 99 73-49 1.02 -- 99 73-52 73.22 $9 57.24 ?? 57.29 - -- -- -- - __- - -- -- -- -- -- - -- -- 9 , 9 9 - -- - -- -- - -- -- ~ _ _ _ -- _- - -- $9 Peas 11-47 2.34 22.34 5.57 1-12 57-26 100.1 percent - -- - - _- -- - - _ I - -142 THE ANALYST.It will be noticed, my analyses of these cereals rather differ from the published ones, in so far as there is no room for sugar, which is supposed to be present in percept- ible quantities, sometimes as much as 4 per cent. Sugar is certainly not precipitated by baryta water, not even if proof spirit is added. I have also never been able to detect it in the filtrate, but in peas I have found an albuminous body which, after boiling with hydrochloric acid, acquired the property of reducing Fehling's solution. No doubt this process will work well with such bodies as mixed mustard, pepper, etc., if they are first washed with alcohol and ether, to remove resinous and fatty matters.-L. DE K.] [NOTE BY TRANSLATOR. MONTHLY RECORD OF ANALYTICAL RESEARCHES INTO FOOD.STARCH IN MUSTARD.-h the American Record of Pharmacy, H. Trimble suggests the amounts of ash found in ground mustard as a guide to the amount of starch found previously by the microscope. Experiments are given by R. C. Werner, who finds the normal ash t o be 6 per cent., but it is not stated whether this figure applies to the mustard previously dried at 2 1 2 O or not. The experiments are only 5 in number and the idea wants confirmation because it is evident that the ash in any commercial sample depends a good deal upon the degree of refinement from husk, etc. W. H. D. MONTHLY RECORD OF ANALYTICAL RESEARCHES INTO DRUGS. A TEST FOR MORPHINE. G. VULPIUS. Arch. d. Pharm., 225--256.--The author substitutes sodic phosphate for potassic arseniate. If a little morphine, not less than .00025 gram,, is first moistened with six drops of sulphuric acid, then mixed with a few centigrammes of sodic phosphate, and now heated, until white fumes appear, the colour first becomes violet, afterwards brown.If after cooling a few drops of water are added, the colour turns a fine red, but the addition of about 5 C.C. of water makes it dirty green. If the liquid is now put into a test tube, and shaken with an equal volume of chloroform, the latter will, after subsiding, be found to be of a fine blue colour. The blue d o u r obtained in the well known test with morphine and neutral ferric chloride is not soluble in chloroform. L. DE I(. MONTHLY RECORD OF GENERAL RESEARCHES I N ANALYTICAL CHEMISTRY. DIRVELL. Dingl. pol. Journ. 263, 538.-The sulphides, precipitated by hydrochloric acid from their solution in ammonic sulphide, are dissolved in nitro-hydrochloric acid, and mixed with a small quantity of a saturated solution of sodic oxalate. A solution of oxalic acid is now added, and then an excess of pure sodic hydrate. If sodic oxalate separates out this must be removed by filtration. The liquid is now heated to looo C., and the gold and platinum precipitated by a small excess of chloral hydrate. The filtrate is diluted with water, and boiled for some time to remove the chloral, then acidified with hydrochloric acid. Excess of sulphurous acid is now added, and the antimony precipitated hot by sodic bisulphite and sodic hyposulphite. The filtrate is mixed with large excess of hydrochloric acid, and precipitated hot with hydric sulphide, to get the arsenic. The large amount of acid prevents precipitat,ion of the tin, which is then estimated aa usual. SEPARATION OF GOLD AND PLATINUM FROM ANTIMONY, ARSENIC, AND TIN. L. DE I(.

ISSN:0003-2654    

DOI:10.1039/AN8871200138

出版商:RSC    

年代:1887

数据来源: RSC