摘要:

T.HE ANALYST. MARCH, 1894. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. THE usual Monthly Meeting of this Society was held on February 7th at the rooms of the Chemical Society, Burlington House. I n the absence of the President, Mr. Otto Hehner occupied the chair. The minutes of the last meeting were read and confirmed. The following gentlemen were proposed as members : Leonard Archbutt, F.I.C. , 11, Charnwood Street, Derby ; B. E. R. Newlands, 27, Mincing Lane, E.C. ; T. H. Pearmain, Apothecaries’ Hall, Blackfriars, E.C. As associate : Raymond ROSS, Assistant to Dr. Horace Swete. The following gentlemen were duly elected members : Frederick Dunn, James Edmunds, M.D., A. R. Ling. Papers were then read on “The Detection of Cotton-seed Oil in Lard,” by Edward J. Bevan ; Milk and Milk Products,” by H. Droop Richmond; and on a ‘‘ Suggested Addition to Richmond’s Milk Scale,” by Walter J. Sykes. The publica- tion of these is unavoidably held over.

ISSN:0003-2654    

DOI:10.1039/AN894190049a

出版商:RSC    

年代:1894

数据来源: RSC

摘要:

THE ANALYST. 57 THE ANNUAL DINNER. Immediately after the Annual Meeting the members of the Society and their friends adjourned to the Criterion, where the annual dinner took place. The chair was occupied by the President, Sir Charles Cameron, supported by Captain Verney Cameron, C.B., R.N., Dr. F. Allan, Dr. Abraham, Mr. Otto Hehner, Dr. Muter, Mr. Alfred H. Allen, Dr. Stevenson, Mr. C. E. Cassal, Dr. Alder Wright, Dr. J. A. Voelcker, Mr. J. A. R. Newlands, Mr. B. Newlands, Mr. E. W. Voelcker (Hon. Treasurer), Dr. Bernard Dyer (Ron. Sec.), Mr. Edward J. Bevan (Hon. Sec.), Mr. Aubrey Rake (Solicitor to the Society), etc.58 THE ANALYST. The following toasts were proposed by the President : (‘ The Queen and all the Royal Family ;” “ The Army, Navy, and Reserve Forces.” Captain Cameron responded for the Navy, and Captain C.E. Cassal and Surgeon-Major Smith for the Army and Reserve Forces, Dr. F. Allan proposed the toast of ( ( The Society of Public Analysts.” The public analyst, he said, was an indispensable ofKcial. Some public authorities, apparently, thought that he was only an ornament, and that he was unnecessary. Others looked upon him as a necessary evil that the Local Government Board insisted upon, who should be paid as little as possible, and about whom it was hoped that he would do as little as possible. He fancied that the public knew very little of what a public analyst was, or what his duties consisted in. He thought that if the public and their representatives as a rule knew what public analysts did, the arduous work, acd the skill that was required to carry out the intricate processes, they would more highly appreciate his services than was at present the case, The work of the public analyst was becoming more and more intricate as science advanced. As new methods were discovered for detecting adulteration, the adulterator found out new methods for deceiving ; he invented more complicated methods of adulteration.It was even asserted, but by suspicious persons, that the cows found methods of getting water into their milk before they were milked, It was high time that the Society should pfit themselves more prominently before the public. He was sure very few of the public realised the trouble which was required to make an analysis of even the most simple substances, which were so very freely ordered to be analysed.H e believed his seiection to propose the toast might have arisen from the fact that he was one of the few medical men present who was a public analyst. I n coupling the toast with the name of the Society’s distinguished President, he could, without the slightest fear of contradiction, congratulate it on having one very specially fitted by nature for the post. He had had the good fortune to serve under him in a body with which they were both connected, and the way in which he performed his duties was one which gained praise and honour on all sides. He was sure that the Society of Public Analysts must be proud to have such a man at their head. Sir Charles Cameron, on behalf of the Society of Public Analysts, thanked Dr.Allan for the way in which he had proposed the toast. The Society of Public Analysts was EL society composed of men who were all earnest in their work, though they were not always very highly paid. He could only say this, that there was no society with whom he felt more enjoyment in mixing than with his colleagues in the Society of Public Analysts. Dr. C. R. Alder Wright said he felt it was a great honour to be asked to propose the health of the Vice-presidents of the Society. When he looked back upon the last twenty years, and saw the progress which the Society had made, the difference between the position in which the public analyst now stood and that in which he stood at the earlier period was exceedingly great. This advance was largely due to the Vice-Presidents, many of whom had, in their time, occupied the presidential chair, There were, of course, two kinds of Vice-Presidents-those who had not yet attained to presidential rank and those who had passed it.There were representa- --THE ANALYST. 59 tives of both on the list before him. I t was his good fortune that evening to couple with his toast the names of Dr. Stevenson and Mr. Hehner. A s regarded Dr. Stevenson, he need say nothing to commend him to the sympathy of public analysts. Such men promoted the interests of the Society, gradually raised it in dignity, and advanced it so far in the estimation of the public that it might rank with the highest learned society extant, Of Mr. Hehner he need say even less. He was well known, first as an ordinary member, then as a honorary secretary, as a President, and finally as a past and Vice- President.He wished to emphasize what he had already said, that the progress which the Society had made was very largely due t o his hard and good work in every sense of the term. Dr. T. Stevenson, in replying to the toast, said that he was very much obliged for the kind manner in which the toast had been drunk, and to Dr. Wright for the exceedingly kindly manner in which he had spoken of the Vice-presidents and of himself. Although of late years he had taken but very little active part in the Society, yet he could claim that he was one of its founders. He had been associated with it from the first ; and, as he looked around, he noticed with melancholy regret the absence of many of his old colleagues among the officers. It was now more than twenty years ago when he, with others, met to found the Society of Public Analysts, a society which had since advanced very much in the estimation of the public, and in that of chemists generally, and this advance was due chiefly to the activity of younger and more active members of the Society. It was always a very great pleasure to him to see his name among those who held office in it; to read the journal of the Society, and to associate himself, so far as his other duties permitted, with the advances of analytical science. Although, as had been said, his own special line lay outside the Society in a great measure, yet he was always very proud to be considered as ranking among those humble people who, while taking very small fees, did excellent work in the service of the public.This Society had done as good work as any other Society of a like standing, and it had a great future before it. Mr. Otto Hehner said that he would like to add his mite to the remarks which had fallen from Dr. Stevenson at the regret which he felt at the absence of old faces that evening. Some, alas ! had gone never to return, but their memories would ever remain fresh in the miuds of those who had known them as dear friends. He was, however, glad to see present his old friend Dr. Muter ; he regretted the absence of Dr. Dupre, Mr. Adams, and Dr. Hill, but he was sure they were all present in spirit. He remembered when this was a struggling society; he had seen how it gradually grew from youth to adolescence, from adolescence to manhood, and now its position, he was proud to say, was acknowledged even by those who were once its bitterest opponents.He did not mean to say that the fog was even yet altogether dispelled; on the contrary, it still lay over the country. Few people recognized that public analysts did work of the utmost importance. Those who ought to be most grateful to them for safeguarding their interests, ought to be the first to acknowledge that analysts were their protectors and faithful servants. He had only quite recently seen in a country newspaper an appeal to public analysts to turn their attention to ascertaining the distinction between the water of the pump and the water They all knew him by his work. His work spoke for him.But they did not.60 THE ANALYST. natural to milk, and to leave off harassing honest traders. He also saw the fog, which sometimes came up the Thames Valley, rise over Waterloo Bridge and creep over a certain building close by, and he saw that building and those within it covered by that fog, which seemed to be impenetrable. Still, ‘ 4 hope springs eternal in the human breast,” and that hope which had upheld public analysts through the past twenty years would carry them on still further. This was an epoch-the end of a chapter-in the history of the Sale of Food and Drugs Acts. They had had foisted upon them by Act of Parliament a body of referees, with whom they were anxious to work in unison ; but, in spite of all their efforts, they had not succeeded. I t might in the past have been in some part their own fault-he did not say it had not been ; but it had certainly not been entirely their fault that they could not work in harmony with those referees.Although the public might not be aware of the fact, analysts had done a great deaI for them. Nor did the various authorities who were the guardians of the public weal recognize adequately the services of the analysts. He knew that an immense amount of work was set before them, and he hoped that they would not cease their efforts, but persevere in the path they had trodden hitherto. Mr. Alfred H. Allen said he sympathised with and endorsed everything that had been uttered by Mr. Hehner, and he could only say that, as one of the Vice-Presi- dents of the Society who had passed the chair, he was sorry to think that some of them had been lost to the Society by death and others were absent that evening through circumstances over which they had no control.When he contrasted the small gatherings of eight or ten years ago with the numerously attended dinner of to-day, it showed that the influence and position of the Society of Public Analysts, and the interest taken in the Society, was materially increasing; and if the members would only do justice to themselves, have confidence in their own powers, and stick together, there was no object which they could not achieve. He looked forward to the day when it should not be simply a society banded together by a subscription of a guinea a year, but that it should be the Chartered Society of Public Analysts, oflicially recognized ; that it should have the power-the legalised right-of laying down limits and standards, and possibly methods of analysis, which should be recognized just in the same way that Parliament had for years past legalized the limits of strengths of spirits.Then the Society would be looked up to as the authority-subject, of course, to sanction by the Privy Council or similar body- which should lay down standards and limits and frame definitions. Then there would not be any possibility of a defence being put forward to the effect that beef- fat was necessary in the manufacture of lard, and that malt vinegar was anything which contained malt. If public analysts would only stand by each other they would have in the near future the power of settling these matters on a fair foundation, so as to do no injustice to innocent manufacturers and tradesmen or to interfere with harmless trade practices; but, at the same time, they would prevent a great deal of the fraud which went on at the present day, and which caused hundreds of thousands of pounds of loss annually to the people of this kingdom, Mr.J. Newlands, in a humorous speech, proposed the health of the other officers. Things such as these were public scandals.THE ANALYST. 61 Mr. E. W. Voelcker, in responding, said he felt that he could only express his intention of doing his best for the interests of the Society in endeavouring to fill the place of the late hon. treasurer, Mr. Heaton. Mr. E. J. Bevan, in returning thanks, said that he felt great difficulty in occupy- ing the position that he did owing to the fact that the late lamented Mr.Davies had filled the office with such complete satisfaction to all the members. He could only hope, in some small degree, to follow in his footsteps. Dr. Bernard Dyer, in returning thanks, said that he had a message of greeting to give to the Society from Dr. Vieth, who was continuing his labours in milk chemistry at the new dairy station at Hammelin in the Province of Hanover. Dr. Sykes returned thanks, and gave some statistics regarding the financial aspect of the Journal of the Society. Dr. John Muter thought he was very lucky in getting the toast he was about to propose assigned to him, because good wine needs no bush; and, when he stated that it was I t The Health of the President,” he thought he scarcely need say any more.As regarded the presidential duties, of course Sir Charles Cameron, being so much in Ireland, had not been able to attend many of the meetings, but he came over on every important occasion. I t was the regret of his life that he was not able to go to Dublin last year, for he understood, from the accounts he had heard, that the members had had a pleasant time. The President, in replying to the toast, said that he felt most grateful to Dr. Muter for the way in which he had proposed his health and to the members of the Society and the guests for the way in which they had received it. He did feel very proud indeed to be the President of the Society because, as he had already stated in his address that day, although he performed other functions than those o€ an analyst, yet he had all his lifetime been an analytical chemist.He had also great pleasure in stating that it gave him much gratification to undertake the duty of President. It had always been a matter of regret to him that more members did not come over to Ireland to attend the meeting of the Society to which Dr. Muter had referred; but he might mention to those who were not present at the annual meeting held that afternoon that he had been asked by another kindred ssaociatiofi-tho British Medical Association-to deliver the address on public medicine in Bristol; and he hoped that on that occasion the country meeting of this Society would simultaneously take place with the meeting of the British Medical Association; and that the members of the Society would do him the honour of dining with him in Bristol some time towards the end of July. That would be the way in which he would feel most grateful to the members of the Society-to make the next summer meeting as successful a meeting as the one which he had the pleasure of welcoming in July last. Dr. J. A. Voelcker proposed the toast of (( The Visitors,” which was responded to by Messrs. B. J. Newlands, Dr. Phineas Abraham, and Dr. James. Messrs. Septimus Marsland and Walter Fletcher favoured the cornpany with62 THE ANALYST. songs, and several solos were very tastefully rendered on the violoncello by Herr von Mulder. The musical arrangements were under the direction of Mr. Alfred Smythson.

ISSN:0003-2654    

DOI:10.1039/AN894190057b

出版商:RSC    

年代:1894

数据来源: RSC

摘要:

62 THE ANALYST. TKE LEFFMANN-BEAM METHOD FOR FAT-ESTIMATION I N MILK. PART III.* BY H. DROOP RICHMOND AND L. KIDGELL BOSELEY. (Read at the Meeting December 6, 1893.) IN a previous paper (Part I.) one of us suggested that differences between the results obtained by Leffmann and Beam, by Hehner, and by himself were due to diversity in the amount of acid added, the strength of the acid, and differences in the fusel-oil. Inflz6ence of FzcseZ-Oil.-Five samples of fusel-oil were obtained from different sources ; the smell and colour when mixed with hydrochloric acid varied considerably. A inilk was taken which gave 3.66 per cent. fat by the Adams method, and Leffmann and Beam determinations were made in triplicate, using bottles for which various factors had to be used to correct scale readings into actual percentages.No. of Expt. 101 102 103 104 105 Fusel-Oil ... ... A B C D E Fat by Leffmann and Bk'am 1. 3.70 3.62 3.72 3.60 3.62 9 9 ,? ,, 2, 3.70 3.65 lost. 3-60 3.60 9 , 9 , ,, 3. 3.73 3.63 3.73 3.61 3.62 Average ... ... ... 3.71 3.63 3.72 3.60 3-61 Number of revolutions re- quired to produce coniplete I 200 100 250 100 100 ... separation ... f These results show that there is a slight difference in varioussamples of fusel-oil amounting to 0.1 per cent., and also that results are concordant to 0-03 per cent. It is not necessary to multiply these results, but we have several times found the same difference in other experiments. The fusel-oil we use generally is E, and this has a specific rotation [a]u of 1.7", and therefore contains about 30 per cent.of the active amgl alcohol. We thought it possible that by the continued action of hydrochloric acid on the amyi aicohoi, that amyi chloride, and possibiy di-amyl ether (cf. Bogers, Joum. Chem. Soc., lxiii, 1160) might be formed, and that these might influence the results; we find no evidence of this being the case, as freshly-prepared '' fusel mixture " gives results which are identical with a '' fusel mixture " prepared for some months. A slight error may be introduced by the use of different fusel-oils, but a few preliminary experiments with each lot of fusel-oil will soon settle the question. In$uuence of the Strmgth of Acid Used.-Embrey (ANALYST, xviii., 118) has pointed out that in a somewhat analogous process it is very important to work with a fixed strength of acid ; he does not show that the results are influenced otherwise than by a discoloration of the fat by strong acid.+ Part I., Analyst, xvii., 144 ; Part II., Analyst, xviii., 130.THE ANALYST. 63 We have taken milks and made estimations with five differing strengths of acid with the following results : Adams ... 6.10 3-93 3.53 3.49 106. 98.3% acid 6.07 4.00 3.60 3.52 - I 107. 96.8 ,, 5-89 - 108. 96.1 ,, 5.90 - - I - - - 109. 95.3 ,, 5.92 110. 93.9 ,, 5.76 3.77 3.37 3.30 The Leffmann-Beam results are here the readings of the scale, and are not multiplied by a factor for correction. With the strongest acid at the ordinary temperature (about 20" C.), the fat was so dark as to be hardly readable when the whole of the acid was added at once; by cooling the acid and milk down to 5" C., or by adding the acid more gradually, the fat came up in a clear light-coloured layer, and could be easily read ; no difference in the results was, however, obtained ; we have obtained a large number of results point- ing to the same differences by varying the strength of acid. The strengths 98.3 and 93.9 are about the extreme variations for acid sold as '' pure "; in the previow parts of this paper these extreme strengths were not used, and consequently the very small differences with varying strengths were not detected.No practical inconvenience is felt from the differences with varying strengths of acid, as a few preliminary experi- ments with each lot of acid and fusel-oil will give the necessary factor to be applied to the bottles to read correct percentages.For this there are five different methods : I t is advisable to test the strength of the acid before use. (1) Estimation of the sulphion (SO,) by precipitation as BaSO,. (2) Estimation of the acidity by titration. (3) Conversion into ammonium sulphate, and weighing as such. (4) Deducing the strength from the density at 15" C. (cf. Pickering, Joum. (5) Deducing the strength from the freezing-point. Chem. Xoc., lvii., 331, et seq.). If the acid is nearly pure, the density determination is by far the most convenient and exact. One of us has published a table for the calculation of percentages (J.S.C.I., 1890, No. 5), but it has the disadvantage of not being applicable to acids of about 97 per cent. strength; it is necessary to dilute these with 3 to 5 per cent.water (or ice) ; impurities in the acid may make BE appreciable difference. We do not recommend the titration of the acid, as the error of titration is rather large unless done under special conditions, and standard solutions of alkali may be inaccurate to 1 per cent. of their absolute value, unless carefully corrected for tempera- ture and accurately standardized. The estimation as sulphion, of course, will return as sulphuric acid all sulphates present as impurities. The determination of the freezing-point requires some skill, but in the hands of experienced observers yields very accurate results; the tempera- ture of freezing of ordinary strengths of acids are so low as to render this method gen era11 y troubles om e.The conversion into ammonium sulphate is very convenient, but neutral sulphate of ammonium is never obtained, the residue is always acid to methyl orange; if the64 THE ANALYST. acidity be determined by titration and a correction made, the residue ignited and the non-volatile matter weighed, this method gives results which are approximately correct. By estimating the residue upon ignition of the acid and subtracting twice its quantity from the acid deduced from the density, a fair approximation of the strength can be made. We are in the habit of using the (NH,),SO, method and the density determination, and the corrected results are not very far apart. Inflzence of Time and Speed of Whirling.-Variation in the time of whirling from one half to three minutes produced absolutely no change, Variations in the speed from 700 revolutions per minute to 2,000 produced no change.I t is very unlikely, then, that any fat should be held in suspension,* as in that case variations in time and speed of whirling would then show differences. InJluence of Temperature.-Dr. Voelcker suggested to us that temperature would make a difference in the results ; it does in this respect, that if the milk and acid are at a high temperature when mixed with the higher strengths of acid, the fat is liable to be dark in colour, and is difficult to read. We have very few specific results as to the influence of temperature, but as we find that these tend to show that there is no appreciable difference, and we find that on hot or cold days the Leffmann-Beam results agree equally well with the Adams determinations, we do not attach much importance to this.We give a table of results obtained; in many cases a weak acid has been employed as low as 93 per cent. H,SO,, and the factor for the acid and fusel-oil has been in these cases calculated from a few preliminary experiments; in others the bottles have read directly the percentages of fat, a stronger acid having been used. In correcting for errors in graduation of bottles we always multiply by a factor and never add a constant; if the error is simply due to incorrect graduation, the equation calculated from the results for the relation between Adams (A) and Leffmann-Beam (B) should be A = zB + 0. Were the fat incompletely thrown up, the equation would then become A = xB + K, K being the amount of fat retained.We have taken four of our series, and calculated the equation connecting Adams and Leffniann-Beam, by making every pair of results into a simultaneous equation and combining the solutions ; we have also calculated the probable error in the constant K. These are: 1. A = 1.096B - '04 f -04 n A A n ~ n n %no I ~ 1 . = U'Y~UI, - U L ~ E : G ~ 3. A = O*991B + *01 f *03 4. A = 1.012B - '03 f -03 In each case it is seen that the constant (K) does not exceed the probable error, and it is therefore practically nothing. We have thus experimental proof that no fat is retained in solution, and that the errors of graduation may be compensated by multipIying by a factor. I n order to throw more light on the r6Ze played by the fusel-oil in the Leffmann- Beam process, we have found it of assistance to compare the results obtained by a * We find that we ohtain the same result on adding the " fusel mixture " after the acid, as when the 6 g fusel mixture '' is added first.THE ANALYST.65 process analogous to the Leffmann-Beam with the fusel-oil omitted-the Babcock process. This has been lately treated of by Stokes, Shutt, Embrey, Babcock, and Tich- borne, and our labour in finding suitable results has been greatly increased by the fact that each of these observers to a notable extent contradicts the conclusions of the others. Out of the mass of information we are enable to pick out thirteen results by Embrey from which we can calculate a relation between Adams and Babcock. Tichborne gives in a footnote some data from which another relation can also be calculated.These are : Embrey A = ~ +*35&*04 1.013 B 1.11 Tichborne A = - + ~ 4 5 These two equations only agree in one point, i.e., in showing that there is fat retained by the acid mixture, a conclusion reached independently by Stokes. I t is a well-known fact that when sugar, sulphuric acid, and fat are mixed, combination takes place, with the formation of a compound of red colour. This red colour is noticed when milk and sulphuric acid are mixed. I t is an equally well- known fact that when arnyl alcohol is substituted for the fat, a compound of a reddish-violet colour is formed. This we always notice in the Leffmann-Beam process. We hardly venture to form a theory that the retention of fat in the Babcock process is due to the formation of the red compound, but we think we are quite safe in saying that in the Leflmann-Beam process the fusel-oil itself would combine with the acid and sugar before the fat is attacked, and thus the whole of the fat is available for estimation.The tendency for the fat to enter into combination will be much less in the Leffniann-Beam process than in the Babcock, seeing that in the former the final mixture contains barely 50 per cent. H,SO,; while in the latter the strength exceeds 64 per cent. H,SO,, and it is kept at a high temperature by the boiling water. That the formation of a compound containing a part of the fat is probably not the whole explanation is shown by ths fact that Embrey and Tichborne obtain results showing relations between the Adams and Babcock which are not in accordance, while neither ef these relations expresses the resdts of Stokes and Shutt ; while Tichborne con- fesses that the Babcock is full of hidden errors.I n justification of the error of the Babcock process, Embrey has pleaded that his inaccuracies are the results of the bottles being graduated to show the percentages of butter that can be obtained from the milk, and not the percentages of fat; as this statement is at direct variance with that of the inventor of the method, who says, “The test is designed to show the amount of pure butter-fat in the milk, and not the butter which will be made from it,” we have ignored Embrey’s Statement, and have based the relation we have calculated from his results on the assumption that Babcock’s statement is the more reliable.We have deliberately come to the conclusion that it is to the use of fusel-oil that the Leffmann-Beam method owes its marked superiority. The many objections, which seem so apparent to patentees of other methods that they think it unnecessary66 THE 9NALY ST. to detail them, we have not only been unable after long investigation to discover, but we find them to be, in mathematical language, negative quantities. We would like to state, lest any purchaser of Leffmann-Beam machines may be afraid to use them on account of Embrey’s statements ‘‘ that they are dangerous, and that it is desirable to cover them in (presumably with a light tin case), because the cups, which are very liable to come off, would be driven through the operator’s body,” that we have not heard of any accident from this cause, and that in the niany hundreds of experiments we have made, nothing untoward has occurred.We do not, however, think that Mr. Embrey meant this part of his paper to be taken seriously, as the absurdity of putting a, light tin case as a protection against a pro- jectile of sufficient force to penetrate the body of a human being is manifest to all. We wish to emphatically state that the Leffmann-Beam method is quite unsuit- able to be placed in the hands of inexperienced persons, though in scientific hands it is capable of great accuracy, We have endeavoured to study one by one the errors of this method, and to show the means of correcting them.That we have been entirely successful we can hardly hope, but as a long experience has failed to reveal other serious errors, we think that those that have escaped our notice are not important. We hope to find time to study the Babcock method, and to see whether the errors mentioned by Tichborne, and shown by the results of other observers, are inherent or adventitious. SUMMARY OF CONCLUSIONS. 1. As variations in the sulphuric acid and fusel-oil may slightly influence the result, it is well to obtain large quantities of these at a time, and by a few prelimi- nary experinients fix the factor necessary to convert scale-readings into percentages of fat. 2. It is advisable to use the same strength of acid (94-96 per cent. H,SO, is con- venient). This is best estimated by converting a known quantity into ammonium sulphate, drying at 100” C., and weighing; titrating the acidity with & baryta solution, using methyl orange as indicator, and then igniting, and weighing the non-volatile matter (correcting for the barium sulphate formed) ; or by deducing the strength from the density (hydrometers are rarely of sufficient accuracy, and a picnometer should be used), and correcting by subtracting twice the weight of the non-volatile matter.3. If it be necessary to perform the experiment when the atmospheric ternpera- ture is high, the milk and acid should be cooled beforehand, or should this not be practicable, the acid should be added in small portions (2 c.c.) at a time, and the bottle shaken between each addition, or a weaker acid may be used.4. About half to three quarters of a minute’s revolution at the rate of from 1,200 to 1,500 revolutions a minute has been found the most convenient in practice. The machine has not been found dangerous at this speed; but, if wished, a longer period of revolution at a slower speed is equally eficacious. SUGGESTIONS FOR PRACTICAL USE. This method must not be used for accurate work unless the bottles, using the same acid and fusel-oil as are designed for general use, are standardized against the Adams, or other reliable method. If this be done the results can be relied upon toTHE ANALYST. 67 0.15 per cent., and are nearly always accurate to 0-1 per cent. It can thus be used for milk control by a skilled operator. A six-bottle machine is large enough for the most extensive laboratories, as with this 30-50 samples an hour, according to the energy of the operator, can be examined. The total solids and solids not fat can be calculated therefrom by the milk-scale or Hehner and Richmond's formula, provided the density of the milk be not taken until after an expiration of twelve hours from the time of milking. Before this time Recknagel's phenomenon is not complete, and calculation of the total solids may lead to serious errors.I t is quite useless to recommend this, or any other rapid method of fat estimation, combined with any tables for calculating total solids, to farmers, as they will only be led into error if they attempt to do any more than estimate the fat. The very doubtful value that a knowledge of the amount of solids- not-fat might have to cheesemakers, is also reduced to nothing.The proper sphere of this method is the laboratory, and for public analysts for sorting their milks, and for chemists engaged in milk control it leaves nothing to be desired. No. of Expt. 111. 112. 113. 114. 115. 116. 117. 118. 119. 120. 121. 122. 123. 124. 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135. 136. 137. 138. 139. 140. 141. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .., ... ... ... ... ... ... ... ... ... ... ... ... ... ... TABLE OF RESULTS OBTAINED. Adams, 3.80 3.58 3.71 3.61 3.70 2.79 3.40 2.38 2.60 1.44 6.21 3-67 3.77 2.32 2-93 3-40 3.44 2.21 3.19 1.87 2.65 3.00 2.99 3.51 3.64 2.82 2.72 3.50 3.53 3-31 3.51 ... ... ... ... ... ... ... ...... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... Leffmann and Beam. 3.80-3.80 . . . 3.55 ... 3.75-3.70 . . . 3.57 3.72 2-77 3.40 2 *30 2-60 1-45 6.15 3.65 3-65 2.30 2-80 3.35 3.45 3.22 3.20 1.90 2.66 3-15 3.00 3 -40 3.55 2.72 2.75 3.50 3.47 3.30 3.45 ... ... ... ... ... ... .. ... ... ... ... .I. ... ... ... ... ... . .. ... ... ... ... ... ... ... ... ... ... Error. - -03 - - - -06 + -02 - -02 - -08 + -01 - -06 - *02 - -12 - -02 - -13 - -05 + -01 + -01 + *01 + *03 + *01 + -15 + *01 - -11 - -09 - *lo + a03 - - - - '06 - -01 - *0668 THE ANALYST. No. of Expt. Adams. Leffmann and Beam. Error. 142. ... 3 *52 ... 3.50 ... - -02 143. .., 2.26 ... 2.20 ... - 06 144. ... 1.60 ... 1 -50 ... - -10 145. ... 3.66 ... 3.61 ... - *05 146.... -40 ... a38 ... - -02 147. ... 3 86 ... 3.92 ... + *06 148. ... 4.00 ... 3.97 ... - '03 149. ... 3.66 ... 3-66 ... 150. ... 6.14 ... 6.16 ... + 02 151. ... 6.1 0 ... 6.22 ... + -12 152 ... 4.48 ... 4.46 ... - -02 153. ... 3.90 ... 4.00 ... 3. .lo 154. ... 3.64 ... 3-67 ... + n o 3 155. ... 3.59 ... 3.63 ... + a04 APPENDIX. (Extracted from the Journ. SOC. Chem. Ind.) - TABLE FOR DEDUCING THE STRENGTH OF SULPHURIC ACID FROM THE DENSITY. Density at 15" C. (Water at 15" C. =I.) Density. 1-8384 ... ... 1.8404 ... ... 1*8418 ... ... 1.8430 ... ... 1.8430 ... ... 1,8425 ... ... 1.8420 ... ... 1.8415 ... ... 1.8410 ... ... 1.8405 ... ... 1.8400 ' ... ... 1.8395 ... . . 1.8390 ... ... 1.8432 (maximum). .. Percentage of Acid. 100*00 99.50 98.98 98-08 97.50 96.93 96.39 96.02 95.67 95.40 95.16 94.96 94.77 94.57 Density.1.8385 1.8380 1.8375 1,8370 1.8365 1.8360 1.8355 1.8350 1.8345 1.8340 1.8330 1.8320 1.8310 Percentage of Acid. ... ... 94.38 ... ... 94.20 ... ... 94.03 ... ... 93.87 ... ... 93.71 ... ... 93.56 ... ... 93.41 ... ..- 93.26 ... ... 93.12 ... ... 92.98 ... ... 92.71 ... 92.46 ... ... 92.22 This method is most unfitted to place in unscientific hands. Even more SO is the Babcock process. DISCUSSION. Mr. E. J. Bevan said it appeared to him that the authors had gone somewhat too minutely into detail, seeing that they admitted the possible error to be 0.15 per cent. Nevertheless, the paper was full of very useful hints, and it cleared up several points which he had noticed during the use of the process, and he thought it was a very welcome addition to analytical literature.With regard to the danger of the apparatus, he could plead guilty to putting up a thick iron screen himself. When in Dr. Muter's laboratory that gentleman had recommended him to be on the safe side. Mr. Burford stated that in using the HC1 mixture four months old .he had obtained precisely the same results as when using the mixture freshly prepared. He also gave his experience of using the small machine, and in obtaining various readings, and referred to the difficulty he found in weather like the present in consequence of the fat actually congealing in the morning before he could read it. What he had toTHE ANALYST. 69 do finally, was to put the bottles in a vessel of warm water and keep them in that temperature until he could get a reading.I t seemed to him that some definite method for reading was desirable. He would like to make a remark with regard to the mixture of diluted acid, the instructions given with the machine of 1 acid to 2 of water, hot mixture, being very vague. At the moment of mixing 105" C. was registered, but if left it would fall below 60". If they had a temperature so variable as that, something more definite in the directions was needed. Mr. Cassal said that the machines ought only to be used by trained chemists. I t was absolutely absurd to suggest that dairymaids, ploughmen, and persons of similar attainments were capable of dealing with the difficulties which might arise in the use of analytical machines, and in drawing conclusions from the results obtained with them.To suggest that people of this sort should manipulate with sulphuric acid and amylic alcohol, and attempt to draw deductions from the ceremonies they went through, was ludicrous. He was glad Mr. Richmond and Mr. Eoseley had put this matter again into definite shape, as he (Mr. Cassal) had done on a previous occasion, and he hoped they would hear no more in that Society about such machines being suitable for use by. the untrained and the ignorant. Mr. Richmond said he always used the acid-mixture for filling up the bottles cold, and kept it in a bottle fitted with a siphon and pinchcock, containing half a litre, He had not found the least appreciable difference between using cold acid or hot. I t so happened that his laboratory was always warm, and he had not been inconvenienced by cold days, buts he could quite understand that if it were too cold it would be necessary to warm the whole bottle up again. With regard to the tempera- ture for reading, as far as his experience had gone he had not foundany trouble.The first, second, third, fourth, or even fifth readings gave exactly the same results. He thought there was a possible explanation why the readings had decreased ; that it was not so much due to contraction of fat in cold weather in the neck of the bottle as to the fact that the fat on cooling adhered to the sides, and could not be properlyread. It was always better in his opinion to take too much trouble to find out whether there were errors than to take too little trouble.The time was not wasted, even if there were no tangible results. With regard to the danger of the Leffmann-Beam process, he might say that when the apparatus was going full speed he accidentally put his arm right into it and stopped it, and no material injury resulted. He did not think it was a very dangerous process, but IVlr. Bevan was no doubt right in thinking it best to be on the safe side. The Addition of Phenolphthalein to Margarine. F. Hart. (Chewz. Zeit., 1893, xvii., 1908-1909.)-Soxhlet has proposed, in order to check the adulteration of butter with margarine, which is still extensively practised, that the addition of a small quantity of phenolphthalein to all margarine shall be made compulsory. I n oppositim to this proposal it has been stated that margarine thus treated becomes uneatable within eight days of its preparation.Experiments at the dairy station at Prenelau show that such is not the case. The author has therefore endeavoured to ascertain whether any toxic effect can be ascribed to the small quantity of phenol- phthalein which it would be necessary to add.70 THE ANALYST. Portions of margarine weighing 50 grammes each were intimately mixed with 2, 4 and 6 milligrammes of phenolphthalein and exposed to the air and light for six weeks, at the end of which time no perceptible alteration in their quality could be detected, and all were perfectly edible. That the phenolphthalein was still capable of serving as a means for the detection of margarine was proved by treating each sample with caustic Soda, when a red colour was unfailingly produced. The author then took doses of phenolphthalein, rising from 1 to 20 centigrammes, without experiencing any ill effects.On raising the dose to 0.3 gramme he suffered from diarrhea, which became more severe when the quantity exhibited was increased to 0.5 gramme. When taken in quantities such as these, phenolphthalein had an unpleasant, bitter taste. Assuming that the quantity proposed by Soxhlet, namely 2.2 grammes per centner of margarine, were used, a toxic dose of phenolphthalein would be contained in 13.6 pounds of margarine. The author strongly advocates the adoption of the regulation. B. B. The Use of the Cryoscopic Method for the Examination of Butter, F, Garelli and 1,. Carcano. (Staz. sperim. ngisar. ital., 1893, xxv., 77, through Chem.2eit.)-The authors, having the fact in view that the glycerides present in butter have a lower mean molecular weight than those existing in margarine, have applied the cryoscopic method, now commonly in use for the determination of the molecula'r weights of substances that cannot be volatilised without decomposition, to the detec- tion of margarine in butter. Using the Beckman apparatus with benzene as a solvent, they have found the constant for the molecular depression to have the value 53. Adopting this figure, pure butter has a mean molecular weight of 696 to 716, while that of margarine ranges from 780 to 883. The method, like most of those at present in use, is only available for the detection of fairly considerable additions of margarine.B. B. NOTE BY ABSTRACTOR.-This method, though ingenious, is merely an apotheosis of the ordinary determination of the saponification equivalent. Determination of Free Acid in Solutions of the Salts of the Heavy Metals. F. Hoffmann. (Chem. Zeit., 1893, xvii., 1318, 1319.) -Free acid can easily be determined in solutions of the salts of alkalies and alkaline earths by titration with an alkali, using a suitable indicator, but this method cannot be adopted for solutions of the salts of ihe heavy meiais, as they have an acid reaction even when containing no free acid. The necessity of determining free acid under these conditions becomes especially apparent when solutions of salts that have been used as electrolytes are examined to ascertain what alteration in their acidity has occurred during the passage of the current. Existing methods are comprised under the following heads : (1) Titration with alkali until a precipitate appears.(2) Titration with alkali, using congo-red paper as an indicator. (3) Evaporation of the solution and extraction of the free acid with absolute (4) Titration with a standard ammoniacal copper solution. (5) Determination of the metal and of the total acid, and calculation of the amount of acid corresponding to the metal; the difference between the acid thus calculated and the total acidity giving the quantity existing free. alcohol.THE ANALYST. 71 The method to be described below was devised by the author for ascertaining the acidity of the electrolyte in a copper refinery, and possesses advantages over those quoted above.When excess of potassium ferrocyanide is added to a solution of copper sulphate containing free acid, copper ferrocyanide is thrown down equivalent to the amount of neutral copper sulphate, and hydroferrocyanic acid equivalent to the free acid originally present is liberated. The only condition necessary to be observed in order to convert this into a quantitative method is that the dilution of the solution shall be sufficient to prevent the decomposition of the hydroferrocyanic acid. The details of the method are as follows : A known quantity of the solution, containing 2 to 3 grammes of copper sulphate, is treated with excess of 2.5 per cent. solution of potassiuni ferrocyanide, made up to a litre, shaken, allowed to stand, and 100 to 250 C.C. of the clear liquor (according to its acidity) drawn off and titrated with & caustic soda solution, phenolphthalein being used as an indicator. The solution of potassium ferrocyanide should be well protected from light, and in adding it to the copper sulphate solution care should be taken to prevent any portion of the turbidity that forms in it finding its way into the precipitating vessel, as the settling of the copper ferrocyanide is hindered thereby. A similar inconvenience arises from the use of a large excess of potassium ferrocyanide. The presence of sufficient ferrocyanide can be recognised by utilizing the property of ferric sulphocyanide of dissolving in ether, which is effected thus : A drop of neutral potassium sulphocyanide is added to the liquid to be tested-which, in the case of commercial electrolytes, always contains enough iron for the purpose of the test-and the whole shaken out with ether, which is no longer coloured red, when all the iron exists as ferrocyanide instead of sulpho- cyanide. Seeing that in a mixed solution of copper and iron salts the former is precipitated first by potassium ferrocyanide, the absence of. iron is a proof of the presence of an excess of the precipitant. As all the heavy metals are precipitable by potassium ferrocyanide, the method is generally applicable for the determination of free acid in solutions of their salts. It is much simplified when used for the salts of metals, which give white precipitates with potassium ferrocyanide, e.y., lead, silver, and zinc. In this case no filtration or decantation is requisite, for the turbid liquid can be titrated directly. Small quantities of &‘ ous ” salts, such as ferrous sulphate, do not greatly affect the results, but the method cannot be used when such salts are present in quantity. B. B.

ISSN:0003-2654    

DOI:10.1039/AN8941900062

出版商:RSC    

年代:1894

数据来源: RSC

摘要:

THE ANALYST. 71 REVIEWS. MANURES AND MANURING. By C. M. AIKMAN, M.A., B.Sc., F.R.S.E. (William This is a valuable handbook, exhibiting, throughout, the work of a conscientious agricultural chemistry of We had the pleasure some Blackwood and Sons.) and painstaking writer, well up in the contemporary Germany and France as well as that of our own country,72 THE ANALYST. time since of noticing an ( ( advance ” portion of this treatise, published under the title of ( ( Farmyard Manure.” The complete work, which is now before us, is written on the same lines, and does not belie the promise of the preceding fragment. The work is, throughout, lightened for the general reader by the relegation to appendices of statistical and tabular matter, reference to which is facilitated by note marks in the general text.The aim of the author has been to provide a text-book on manures midway, in the scope of its treatment, between Professor Storer’s elaborate treatise and the smaller and more popular manuals, and he must be admitted to have carried out his by no means easily effected task with a near approach to satisfaction. Mr. Aikman has had, during a number of years past, an exceptional experience as a lecturer on agricultural chemistry, not merely in the comparatively easy work of the class-room, where regular students imbibe their knowledge systematically, but also iu the much more difficult work of expounding its doctrines to ‘‘ popular ” or unscientific audiences in isolated and disjointed discourses. This experience lends probability of fulfilment to the hope expressed by himself that the work now under notice may be of especial value to those engaged in teaching agricultural science, At all events, no agricultural teachers or practitioners of agricultural chemistry shoilljl fail to provide themselves with it.JOHNSTON’S ELEMENTS OF AGRICULTURAL CHEMISTRY. From the edition by Sir Revised and in great part re-written by C. M. Mr. Aikman, whose original work on manures we have noticed in the foregoing paragraph, is indefatigably industrious. Simultaneously with the publication of his own volume there issues from the press this new edition-the seventeenth-of one oE the most popular technical treatises known to agricultural science. I t is thirteen years since Sir Charles Cameron revised aad brought up to date the excellent and once unique work of Professor Johnston, and during these thirteen years the rapid progress of agricultural chemistry has rendered even Johnston and Cameron,” as it is familiarly called, an old-fashioned book, that has been calling out with increasing stress for further revision.This revision has been very fairly accomplished by Mr. Aikman, and as the demand for so time-honoured a text-book is sure to be sustained even in the face of many new ones, agricultural students will be grateful to him for his labours. I n these pages it is pleasant to note that while the book remains, and must always remain, associated with the name of its earlier editor, Sir Charles Cameron, the present President of the Society of Public Analysts, the present edition is dedicated by its new editor to one of the present honorary secretaries of that society. PRINCIPLES AND PRACTICE OF AGRICULTURAL ANALYSIS.By HARVEY W. WILEY, (The Chemical Publishing Professor Wiley’s name is so well known in connection with the scientific investi- gations conducted over a large continent under the superintendence, direct or indirect, of a very active and well-organized Government Department, that anything emanating from his pen cannot fail to arouse interest and to command attention. The work under notice is the first monthly part of what promises to be a very comprehensive manual of agricultural chemistry for the use of analysts, teachers and students. The author hopes to complete the work in twenty-four monthly parts at twenty-five cents each, but this may not prove to be possible. The first part, which begins the subject of soils, contains some excellent plates showing the microscopic structure of various rocks. CHARLES A. CAMERON, M.D. AIKMAN, M,A., B.Sc., F.R.S.E. (W. Blackwood and Sons.) Chemist to the U.S. Department of Agriculture. Company, Easton, Pa., U.S.)

ISSN:0003-2654    

DOI:10.1039/AN8941900071

出版商:RSC    

年代:1894

数据来源: RSC