摘要:

THE ANALYST. JUNE, 1904. OBITUARY NOTICE. PROFESSOR A. W. WILLIAMSON, P.R.S. THE death of Professor Williamson, F.R.S., in his eighty-first year, at Hindhead, Surrey, on May 6 last, removes from our ‘list of Honorary Fellows one who connects this Society and present chemists with the past, Early in life Dr. Williamson visited the Continent, and at Heidelberg and Giessen studied under Gmelin and Liebig, and thus became intimately acquainted with those early investigators in chemistry, from whom the developments of the last century originated. After leaving Liebig’s Labora- tory he did not immediately return to England, but realized that the study of the higher mathematics under Compte in Paris for three years would further equip him for his life-work. At last, in 1849, an opportunity presented itself, and he was elected Professor of Practical Chemistry at University College, London, where Graham had been prosecuting his researches on the physics of liquids, in the laboratory which was at that time unique in this country.For nearly forty years, until his retirement in 1887, Dr. Williamson held the chair of chemistry at this college, and many hundreds of students received from him their early training in the science. Not only from England, but also from the Continent and from Japan, did students come to his classes, and at the present time there must be men in all parts of the world who will recollect the energy, patience, and clearness with which his lectures and demonstrations were given. AIthough it will be as a thorough teacher that Dr.Williamson will be chiefly remembered, his early work in enunciating the type theory of t h e constitution of a11 compounds, and especially in clearing up and establishing on a firm basis the theory of etherification, renders his contribution to our knowledge of the chemical constitution of matter of no mean value, and warrants his being ranked as one of the pioneers in founding our conceptions of the atomic theory. He realized in etherification the mobility of the ions and the dissociation which is involved in mam action, and this at a time when the moleculttr aggregate was believed to be a rigid unit incapable of rupture without external agencies. Thus he was quite in line with the recent developments of modern thought. I n addition to his work as a teacher, and in the domain of pure science, Dr.Williamson, as chief gas examiner to the Metropolis under the Board of Trade, held a judicial position between the gas companies and the consumers, and in other branches of applied chemistry brought his legal faculties to bear upon problems of practical utility. He was elected Fellow of the Royal Society in 1855, was President of the Chemical Society in174 THE ANALYST. 1563-65 and in 1869-71, and was one of the six Past Presidents that had been members of the Chemical Society for fifty years who were entertained at the memorable dinnbr in 1898. He was elected an honorary member of the Society of Public Analysts at an early period of its existence. S. R. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. THE monthly meeting of the Society was held on Wednesday evening, May 4. The President, Mr. Thomas Fairley, occupied the chair. The minutes of the previous meeting were read and confirmed. Certificates of proposal for election to membership in favour of Messrs. A. E. Brown, B.Sc., and L. G. Paul, Ph.D., were read for the second time ; and a certificate in favour of Mr. Harold Sankey Hammond, Assistant Chemist in the Government Laboratory, Jamaica, was read for the first time. Mr. J. H. Ball, B.Sc., was elected a member of the Society. The following papers were read : u Cod-liver Oil and other Fish Oils,” by J. F. Liverseege ; ‘‘ Note on Mushroom Ketchup,” by J. F. Liverseege ; ‘‘ Note on some Constants obtained in the Examination of Margarine,” by Edward Russell, B.Sc., and V. H. Kirkham, B.Sc. ; and a “Note on the Estimation of Sugars in Concentrated Malt Extract,” by Arthur R. Ling and Theodore Rendle.

ISSN:0003-2654    

DOI:10.1039/AN9042900173

出版商:RSC    

年代:1904

数据来源: RSC

摘要:

174 THE ANALYST. ANNIVERSARY DINNER OF THE SOCIETY OF PUBLIC ANALYSTS. THE anniversary dinner of the Society took place on Tuesday evening, May 3, at the Trocadero Restaurant, under the chairmanship of the President, Mr. Thomas Fairley. About eighty members and guests were present. Among the latter were Sir Thomas Elliott, K.C.B., Secretary of the Board of Agriculture; Sir Ernest Clarke, M.A., Secretary of the Royal Agricultural Society of England ; Mr. John Lithiby, Assistant Secretary of the Local Government Board; Dr. T. E. Thorpe, C.B., F.R.S., Principal Chemist of the Government Laboratory ; Professor W. A. Tilden, D.Sc., F.R.S., Presi- dent of the Chemical Society ; Mr. David Howard, J.P., President of the Institute of Chemistry ; Dr. Clarence Cooper, Master of the Society of Apothecaries ; Mr. C. H. Babington, President of the Inatitute of Brewing ; Dr. Groves, President of the Society of Medical Officers of Health ; Professor J. Millar Thomson, LL.D., F.R.S. ; Mr. Thomas Terrell, K.C.; Professor A. K. Huntington; Mr. Richard B. Pilcher, Secretary of the Institute of Chemistry ; Nr. F. W. Beck ; Professor Herbert Jackson ; and Mr. Aubrey W. Rake. After the usual loyal toasts had been given by the President, the following were proposed : ‘‘ Government Departments,” by Mr. W. W. Fisher, M.A., responded to by Sir Thomas Elliott, K.C.B., and Dr. T. E. Thorpe, C.B., F.R.S. ; ‘‘ The Society of Public Analysts, by Mr. David Howard, J.P., responded to by the President; and The Guests,” by Rlr. Otto Hehner, responded to by Professor W. A. Tilden, D.Sc., F.R.S., and Mr. Thomas Terrell, K.C. There was also a programme of music.

ISSN:0003-2654    

DOI:10.1039/AN9042900174

出版商:RSC    

年代:1904

数据来源: RSC

摘要:

THE ANALYST. 175 THE IODINE ABSORPTION AS A FACTOR IN THE EXAMINATION OF OTTO OF ROSE. FREDERICK HUDSON-COX AND WILLIAM H. SIMMONS. (Read at the Meetiiig, March 2, 1904.) THE iodine absorption of essential oils appears to have received very little attention from chemists. Barenthin first drew attention to it in 1886; Kremel did a little more in 1888, and Williams, Snow, and Davies in 1889, the last-named examining, perhaps, the largest number of samples. More recently (the early part of lgst year) Sangtb-Ferridre and Cuniasse (Jozmi. de Pharm., 1903, 169) added a further number to the list, but none of these examined sufficient samples of any particular oil to be of real value, and those who have special facilities for observation do not appear to have carried out any experiments with the process.We quite agree that the iodine absorption is not applicable to all essential oils. Still, it seems to us that in some cases it does give extremely valuable information, and in no case, perhaps, is it more useful than in the examination of Otto of rose. I t has always been considered dif5cult to detect careful adulteration of this oil by chemical means, and the artificial Otto recently put upon the market by various firms hw added to the difficulty. I t was the fact that large quantities of this substance were etated to be imported into the Otto districts which first,raised our curiosity. As chemists to a firm using very considerable quantities of Otto of rose, it was of interest to us to know what became of this imported article, for, although excellent in its way, it did not seem likely that the growers of the natural should prefer the artificial product, and we could not learn that any of it came out of the country under its own name.Two.makes of artificial Otto gave in our hands the following data,* from which Specific gravity 30" C. ... Optical rotation 30" C., . . . Saponification number . . . 15.5" 100 millimetre tube Setting point . . . ... KO. 1. No. 11. A. 0-8629 - 0" 50' 20-5 22.5' C. 13. 0-8717 - 1" 2 0 13.4 A. 0.8589 -0" 14' 3.8 21.9" C. 1%. 0.8658 -0" 52' 5.7 it will be seen that large quantities could be added to the natural oil without fear of detection by the ordinary methods; indeed, a mixture of 1 part artificial and 2 parts natural oil of good quality gave figures well within the accepted limits, and ih odour was not by any means to be despised.We have not determined the acetyl number, because, owing to the large quantity required and the range for the natural oil, we do not consider it generally applicable. The refractive index gives usefu I n the above table A is with, and B without, in each case. These ottos can he obtained either with or withont stearoptene.176 Rotation 30" C., 100-niillimetre 'hibe. THE ANALYST. Setting- Saponificatio,, h'uniber. Point. information in some cases, but since Parry has promised a further report on that, we have not examined the test at any length. While debating as to what course we should pursue, Sangtb-Ferrihre and Cuniasse's paper revived our interest in the iodine absorption, and we determined to see if some use could not be made of that method, and this we did, with results which we think worthy of bringing before the Society.I n our experiments we have used from 0-1 to 0.2 grammes of Otto, added 10 C.O. of 90 per cent. alcohol, 25 C.C. Hub1 solution, and allowed to stand for three hours at the temperature of the laboratory. It has been stated that the temperature has 8 marked effect upon the absorption, but although we have worked at all temperatures from 4" to 27" C., we have not found any appreciable difference. The age of the Hiibl, however, is of very great importance, a solution three weeks old being much less active than a freshly-prepared one. The plan which we find to give the best results is to keep the iodine and mercuric chloride solutions separate, and to mix them the evening before they are required.Another point is that the titration must be carried out as quickly as possible, a8 the colour rapidly comes back. These remarks, of course, apply also to the fixed oils more or less, although not to anything like the extent they do here. We also in some cases substituted 10 C.C. chloroform for the alcohol in order to dissolve the stearoptene, for fear the latter should enclose some of the oil, and SO prevent or retard its absorption of iodine, but we found it made no difference to the result. For use in our experiments we first took samples of Otto of known brands which had previously been examined by the ordinary methods and passed as being of good quality. We examined, in all, twenty of these samples, taken from the seasons 1896 to 1903 inclusive, and found them to have an absorption of from 187 to 194.We give a table of a few of these : No. - 1 2 3 4 5 ~ Specific p v i t y 30 ~ 15.5" c. 0.8531 0.8512 0.8541 0,8587 0.8534 I I - 2" 40' - 2" 35' - 2 O 7' - 2" 30' - 2" 45' 7.5 8.3 8-1 15.5 11.7 20.4" C. 21.0" c. 20.8" c. 2 0 . 3 O C. 20.6" C. Iodine Number. 187 191 192 187 193 This is a larger range than one would wish, and we hope tl reduced to a considerable extent after further work, especially since we have so far been unable to invariably obtain good duplicates, the difference being sometimes as much as 4 per cent. We next took samples of artificial Otto and of a number of oils, either found by ourselves or said by other workers to be used as adulterants.As will be seen by the following table, these, with the exception of citronellol and citrsl, all gave rtbsorp-THE ANALYST. 177 tions well over 200, geranium oils being the lowest with an absorption of 213; but, since these oils have a comparatively &h eeter content, their presenoe is at once demon- strated by the high potash absorption. A point worthy of note is that while artificial Otto is considerably deodorized by iodine, the odour of the natural oil is not affected : Oil. Artificial Otto with stearoptene , . . ..- Artificial Otto without stearoptene . . . ... Palms rosa ... ... Geranium, African . . . ,, Bourbon ... ), Spanish ... Iodine Kumber. 221 to 254 261 279 296 ,, 307 213 ) ) 225 213 ,) 215 211 Oil. Geraniol ... ... Citronella .. . ... Citronellol . . . ... Linalol ... ... Citral ... ... ... Guaiacum wood ... Stearoptene . . . ... Iodine Number. 239 and 307" 217 187 230 175 298 None Having obtained these results, we applied the process to a number of samples submitted to us from time to time, and which we had rejected as being of suspiciousl~ poor odour, adulterated, or suspected of adulteration, and, as will be seen by the following table, we were confirmed in our opinion in each case : N 0. Specific Gravity 30" c. 15.5" 0.8553 0.8561 0.8554 0.8581 0.8797 0.8434 0.8659 0.8550 Rotation 30" C., 100-millirnetre Tube. - 2" 45' - 2" 17' - 2" 42' - 1" 24' - 19" 50' - 0" 47' - 1'24' - 2" 2' Sa onification !hum\>er. 8.9 8.4 8-1 10.3 40.8 16-1 17.3 9.8 Setting- Point. 20.8" C. 19.2" C. 19.8" C.21.3" C. 28.4" C. 18.5" C. 16.8' C. 20.6" C. 2 19 212 206 234 142 133 245 215 Of these samples, in Nos. 1 and 2 we suspect the presence of geraniol and in No. 3 artificial Otto. Nos. 4 and 7 appear to be chiefly artificial, No. 5 is grossly adulterated, but the quantity submitted did not allow of a thorough investigation. No. 6 contained a considerable quantity of alcohol, and No. 8 is the mixture (artificial 1 and genuine Otto 2) already mentioned. A point yeti to be determined is the time required for complete saturation, for, although we have made most of our determinations after fhree hours' standing, it is certain that the reaction is not complete by then. So far we have found that the absorption takes place rapidly to commence with, and then slowly up to at least forty-eight hours, but we have not obtained closer duplicates at any interval between three and forty-eight hours than we have at the end of the first- * Distinctly different oils.The latter apparently artificial, the other natural.178 'I'HE ANALYST. named period, and so have confined ourselves rather to the finding of the exact conditions under which regular abeorption takes place than to the point of saturation, as a process which takes forty-eight hours to complete can hardly be said to recommend itself. We are still working on this subject, and hope to give another note at a future meeting. DISCUSSION. The PRESIDENT (Mr. Fairley) inquired whether in the case of the sample which contained 20 per cent. of alcohol any other adulterant had been found.Sample No. 6 seemed a peculiar one, and it would be interesting to hear how the authors accounted for its very low iodine absorption. Mr. L. MYDDELTON NASH asked what were the constituents in these oils that combined with the iodine. The stearoptene, of course, which constituted a large proportion of the oil, did not combine with iodine at all. He should also like to hear at what temperature the specific gravity of the Otto W ~ B taken. At ordinary tempera- tures it would be solid. Mr. CHAPBXAN said that substances like citronellol, linalol, geraniol, and so on, were extremely reactive bodies, very unstable, and liable on the slightest provocation to undergo intramolecular change, sometimes accompanied by changes in the degree of their unsaturatedness. In attempting to prepare bromine addition compounds from some of the terpenes one often found that a great deal depended upon whether the addition was effected in some one particular solvent in preference to some other, or at a very low as distinguished from merely a low temperature, or even in darkness or in light.The fact that such comparatively small differences in the conditions of working were capable of exercising so great an influence on the product obtained, together with the liability to intramolecular change, seemed to indicate that the absorption of iodine in these cases was frequently by no means a simple process of addition. Experience showed that in the case of unsaturated fatty compounds the Hub1 addition compounds were very complicated, and this seemed to be also the case with the compounds under discussion.Geraniol and linalol being both alcohols containing two doubly-linked pairs of carbon atoms, while citronellol had only one such pair, if there was a simple addition of halogen it might be expected that the numbers for geraniol and linalol would be, roughly, twice those for citronellol. He did not quite understand the figures which the authors had obtained for geraniol. Geraniol was, of course, a definite chemical compound-a definite alcohol-and it was hard to see how two samples could yield numbers so widely separated as 239 and 307. Even assuming the sample yielding the former figure to be exceptional and very impure, the absorption of the other was by no means twice that of the citronellol, which would be the case if it were a simple process of addition.This brought him to a suggestion which he would like to make to the authors, that they should try working in a somewhat different way-namely, by running a well-cooled solution of bromine in glacial acetic acid, chloroform, or some other solvent into a thoroughly well-cooled solution of the Otto of roses or other substance under experiment. This would, at any rate, tend to minimize intramolecular change, and,THE ANALYST. 179 he thought, to produce moresimple addition compounds. In that case any difference in unsaturatednees between these various bodies would probably have a much more marked effect on the numbers, which would, in consequence, be rendered more generally useful. Mr. ARCHBUTT suggested that it would be desirable to state, in connection with these results, how long the oils were allowed to remain in contact with the Hub1 solution, whether the determinations were carried out in the light or in darkness, and what excess of iodine was left at the end of the process.Although he had had no personal experience in regard to essential oils generally, he,had made a large number of determinations of the iodine absorption of oil of turpentine, and had long since abandoned the use of Hub1 solution, having obtained much more satisfactory results with Wijs's solution. Iodine undoubtedly continued to be taken up as long as contact was allowed, substitution no doubt taking place after the formation of the primary addition compound. I n practice, however, ih the case of oil of turpentine, one could learn all one wanted to know by allowing the Wijs solution to act for twenty minutes, and during that time it did not matter whether the action took place in darkness or in the light.He laid great stress on the exact number of minutes being adhered to, as there was a considerable difference between the amount of iodine absorbed by oil of turpentine during twenty minutes and that absorbed during an hour or even half an hour. This he had ascertained from a number of determinations made with the same sample, in which the action was allowed to go on for varying periods up to as long as seventy-two hours. The amount of iodine left unabsorbed at the end of the test also greatly influenced the absorption ; it should be as nearly as possible equal in amount to the quantity taken up.Mr. HUDSON-COX said that in the case of sample No. 6 an excess of stearoptenc had undoubtedly been added to bring up the setting-point, but no further examina- tion had been made of the sample. Otto of rose being an expensive substance, it was the custom for samples to be paid for, but in this case the sample was of such poor quality that it was returned forthwith. The specific gravity of the Otto had been taken in each case at 30' C., as compared with water at 15-5" C. With regard to the samples of geraniol, one of these (iodine number 239) was natural geraniol, probably from Piilma rosa, of which it had a distinct odour. The other, apparently artificial, was purer ; it had no rotation at all. Mr. CHAPMAN remarked that the first sample must be very impure, and it was important to bear in mind that the numbers it yielded could not be taken as applying to pure geraniol, which was a definite chemical compound. Mr.HUDSON-COX, continuing, said thiit there could be no doubt as to the com- plexity of the reaction, but they were able to obtain in most cases duplicate results which agreed fairly well. The process, however, was not applicable to all essential oils. With regard to the conditions of working, all the determinations had been made in the dark, and various periods of contact had been tried, from three hours up to forty-eight hours. The change was certainly not complete in less than forty-eight hours, but it took place very rapidly up to about three hours, and then very slowly ; and, as they had found that the results obtained after a longer period were no more concordant than those after three hours' contact, three hours had been adopted.180 THE ANALYST. Mr. CHAPMAN said that if bromine were used all the absorption required to satisfy the double linkage would take place in a few minutes, and the end-point would be fairly sharp. Mr. HUDSON-COX, continuing, said that the amount of iodine in excess was kept at about the same as that absorbed. They had tried the use of Wijs’s solution, but could not get a satisfactory end reaction. Mr. ARCHBUTT was surprised to hear that, and inquired whether any difficulty had been experienced in getting a constant absorption. Mr. HUDSON-C.OX said that the difficulty was in titration. Decolorization was no sooner obtained than the colour began to come back again. Mr. CEAPMAN said that possibly hydrogen peroxide was formed, which would constant 1 y liberate iodine. Mr. HUDSON-COX said that that was probably so, and he would have expected the same thing to occur in the case of oil of turpentine. Mr. AHCHBUTT said that. turpentine absorbed about 300 per cent. of iodine in twenty minutes under the conditions he had specified. The end-point was quite sharp in titrating, and closely agreeing results could be repeatedly obtained with the same sample. ______ ___

ISSN:0003-2654    

DOI:10.1039/AN9042900175

出版商:RSC    

年代:1904

数据来源: RSC

摘要:

180 3.91 4.17 4-14 THE ANALYST. 8.84 8.88 8.93 THE COMPOSITION O F MILK. WITH SPECIAL OBSERVATIONS OK THE CONSTITUTION OF THE FAT (;LOBULES. BY H. DROOP BICHMOND F.I.C. (Bead at the Meeting March 2 1904.) OF the 37,589 samples examined in the Aylesbury Dairy Company's laboratory during 1903 33,063 were analyses of milk. The average composition of 15,313 samples received from the company's farms is given in the following table : AVERAGE COMPOSITION OF MILK DURING 1903. hi0RNINCi MILK. MONTE. Jaiiuary . . February . . Narcli . . April . . . . May . . June . . July August . . September October Novemher . . December . . Specific gravity. 1 *0321 1.0324 1 -0325 I *0324 1.0325 1 *0324 1 -0320 1 *0320 1.0321 1.0321 1-0324 1 '0324 Average 1 1.0323 Total 3olidn.12'68 12.51 12 -52 12-47 12'40 12-25 12.29 12.53 12.61 12.82 12 '86 12.73 12-56 ~ Fat. -3.71 3'56 3-55 3'52 5.45 3'34 3'46 3.67 3-69 3.87 3-86 3.75 3 -62 Yolide-not-fat 8.97 8 .!45 8.97 8-95 8.95 8.91 8-83 8-86 8-92 8 -95 9.00 8.98 8'94 Specific gravity. 1 *0322 1 '0322 1 '0323 1 -0322 1.0322 1 '0322 1.0316 1'0315 1.031 8 1.031 9 1 -0320 1.0320 1 -0320 AVERAUE. Total mlidH. 13.07 12-85 12'91 12.88 12.92 12.91 12.78 1 3-0:i 13.07 13 2 8 13 '23 1.1'08 13-00 4.05 I 8.95 Specific p v i t y . 1.0323 1 '0323 1 '0324 1 -0323 1 '0321 1.0323 1'0318 1-0315 1 '0320 1 '0320 1 '0322 1 -0322 _-1 '0322 Total solids.12-38 12'68 12-67 12.67 12.66 12-58 12.53 12.79 12-84 13-05 13 -05 12'90 12.78 Fat. -3-89 3-72 3'69 3.71 3%9 3'64 3 *70 3 -92 3.92 4'09 4 -05 3'93 3'83 ~ 3olids-lot-fat. 8 '99 8 '96 8 -98 8.96 8-97 8-94 8-83 8.87 3 -92 S.96 9.00 8.97 8-9 THE ANALYST. 181 The composition of the morning and evening milk is given separately and the usual difference in fat averaging 0-43 per cent. is observed. The average fat (3-83) is slightly higher than in 1902 (3.82) and as almost invariably observed the poorest milk occurred in June and the richest in October and November. The records of which the above table is a continuation which were published by Dr.Vieth in whose footsteps I have endeavoured to follow are sometimes quoted as representative of the composition of English milk. They are however often disputed, and are alleged to seriously overstate the amount of fat ; it is therefore advisable to examine the figures to see whether there are any strong grounds for supposing that the samples which passed through Dr. Vieth’s and my hands were of exceptional quality. The first point which I have examined is the influence of the geological forma-tion. I have been able to pick out four formations on each of which there are a sufficient number of farms to give a fair average-the New Red Sandstone the Oxford Clay the Upper Greensand and the Chalk. I t is of course doubtful whether the influence of the underlying formation is as great as that of the surface deposits, modified as they are by artificial manuring; but it is practically impossible to obtain any other classification and any conclusions which can be drawn must be received with caution and merely as indications.With these reservations I give the average composition for each month during 1902 and 1903 on each of the four formations : 1902. January February March . April . May . June . July . August . September October . . . November December . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ Average . . Fat. 3.94 3-75 3.61 3.55 3.58 3.46 3.57 3-63 3.83 4.11 4.14 4.14 -Solids-not-fat. 8 a96 8.98 8.91 8.89 8.88 8.90 8.85 8-80 8-87 8.94 8.92 8.92 3.78 1 8-90 Fat._-3.77 3.76 3.68 3.75 3.62 3-56 3.62 3-82 3-89 3.96 4 -02 4-03 3.79 Solids-I io t - fa t. 8-91 8.91 8-90 8.94 8.96 8.87 8.79 8.76 8.89 9.01 8.99 9.02 8.91 Fat. 3.93 3.88 3.88 13-85 3.68 3-63 3.7 7 3.88 3-93 3.99 3.94 3.99 3-86 -Solids-not- fat. 9.00 9.01 9.02 9.02 9.01 8.92 8.80 8.i4 8.86 8.98 8.95 9-00 8.94 -C H A L K . Fat. 3.88 3.92 3-85 3 -82 3.67. 3.55 3.67 3.82 3.88 4.01 3.94 4 -03 3.84 Solids-not- fat. 8.92 8.94 8-95 8.90 8.93 8.84 8.79 8.75 8-87 8.94 8.93 8-99 8.9 182 THE ANALYST. 1903. January February March . April .May . June . July . August . September October . . . November December Average . . . . . . . . . . . . . . . . . . . . . . . . . .-. . Fat. 3.84 3.60 3.59 3-57 3.63 3.49 3-60 3.84 3.91 4.07 3.97 3.90 Solids-not - fat. 8.96 8.9 1 8-93 8.92 8.95 8.93 8.83 8.84 8.92 8-96 8-97 8.91 3-75 1 8.92 OXF(JI<D CLAY. Solids-Fat. not-fat. -3.90 9-00 3.80 8-99 3.77 9.00 3.73 8.97 3.66 8-96 3.55 8.92 3-67 8-81 3.86 8.86 3.82 8.90 4-05 8.94 4.04 9.02 3.91 9.01 3.81 8.94 -____-UPPER GREENSAN D. Fat. 3.89 3.78 3.84 3-89 3.72 3.71 3.78 3-93 3.92 4.08 3.95 3-82 3.86 -Solids-not-fat. 9.01 8.97 9.00 9.01 8.98 8.93 8-83 8-86 8.93 8.93 8.96 8.96 8.95 CHALK.Solids-Fat* not-fat. 3.9’7 9.03 3.81 8-99 3.83 9.00 3-80 8.99 3.67 8-97 3.66 8.93 3-74 8-84 3-92 8.87 3.93 8.91 4-12 8-98 4.08 9.00 3.97 8.97 3.88 8.96 The only conclusion that I venture to draw seeing the possible influence of other conditions is that the milk raised OE the two cretaceous formations tends to be better in quality than the others; but the difference is not SO marked as to permit of any sweeping assertion. The second point is the influence of the times of milking. I t is quite well known that the more equal the intervals between milkings are made the more even is the quality of the milk. As near as I can ascertain the average intervals of milking of the cows from which the samples I examined were drawn are 10.8 hours between the morning and evening milkings and 13.2 hours between the evening and morning.If these intervals tend to become less equal the morning milk will tend to be poorer and the evenjng richer though the average is only slightly affected. I t is hardly necessary to give :my examples of this but I mention it as it is a possible cause of instances of milk being very low in fat. A third point lies in the consideration of the incidence of the samples on varying percentages of their constituents. An average tells us nothing of the variations ; thus 50 represents the average of 0 and 100 as well as the average of 49.9 and 50.1 but it is evident that the average is a very much better representation of the latter pair of figures than of the former.I t would be impossible to give the whole of the figures obtained but the practical effect can be obtained by the use of the theory of prob-abilities. The range of incidence of the samples can be expressed by the probable error,” It is necessary in the first instance to make sure that the deviation of milk samples from the mean follom the law of errors which is expressed by the formula - Jt 2. 2 y = k THE ANALYST. 183 0.067 As a convenient and suflicient series I have taken the aggregate of six years’ analyses published in the Report of the Milk Standards Committee 1901 Appen-dix xxv. p. 394 and have tried whether this series agrees with the law of errors. Taken as a whole such wide divergences are found that the law cannot apply to these samples; it only appears to apply to quite low percentages 6f fat.I find however, that by splitting the series into two a sufficiently good agreement is found. By means of the formula Below 3.0 the probability (9) of samples occurring with a percentage of fat (f) can be calculated to agree very closely with the facts. The formula was calculated empirically but 3.59 and 4-0 agree with the averages of morning and evening milks and 0.19 and 0.25 are in very close agreement with their respective deviations from the mean and the numbers of samples of morning and evening milks are practically equal. The follow-ing table shows the probability of a sample falling at the percentage of fat named : Percentage of Fat. Above 5.3 5.0 4.9 4.8 4.7 4.6 4.5 4.4 4.3 4-2 4.1 4-0 Calculated.0.001 0.001 0.003 0.005 0.009 0.015 0.022 0,031 0.042 0.053 0.066 0.078 Actiial. 0 a003 0.002 0 903 0.006 0.008 0.013 0.020 0.029 0.042 0.052 Perceii bge of Fat. 3-9 3.8 3.7 3.6 3.5 3.4 3.3 3.2 3.1 3.0 Calculated. 0.090 0.100 0.104 0.101 0.089 0.07 1 0-051 0.033 0.018 0.010 0.007 Actual. 0.091 0.098 0.100 0.100 0.089 0.072 0.055 0.034 0.018 0.010 0.007 The above figures relate to analyses of single churns of milk which contain the The milk of single cows will vary much more and mixed milk of several cows. though the averages may be the same the ‘‘ probable error ” will be greater. Other series of analyses may give less favourable results : (a) Because owing to some cause connected with the breed or individuality of cows the soil etc.tho average is lower. ( b ) Because owing to less regular intervals of milking the morning milk is poorer and the evening richer ; or, (c) Because owing to the milk of a smaller number of cows than will fill a churn being mixed or from greater individual differences the ‘‘ probable error ” is greater 184 THE ANALYST. In a recent paper ( J o u r ~ . SOC. Chem. Id. 1904 p. 3) S. H. Colline has stated that his figures suggest that there is some truth in the opinion that milk in the North of England is not as rich as that in the South; unfortunately he does not give hie figures but only the p7oportion of samples from single cows which fall below the Board of Agriculture standard.As he takes my figures as representing the South I should have liked to have been able to compare the two. I would point out that so far from considering the cow the analyses of whose milk I published last year (ANALYST xxviii. 290) a remarkably bad one as he assumes it is really a rather good cow and above the average and therefore my figures showing that 5.5 per cent. of the samples were below 3 per cent. of fat are not so greatly different to his 6.7 per cent. of the samples below 3 per cent. of fat; the difference is still less when the fact that the somewhat unusual practice of milking three times a day with very unequal intervals was followed at one of the two farms from which his samples were drawn and were this undoubted cause of low fats eliminated his figures would probably be more favourable than mine.His method of preserving the samples (by the addition of a mixture of ether and chloroform with or without formaldehyde) is one which will conduce to inaccurate results. I assume that the preservative mixturelwas added soon after milking when the fat would be largely in the liquid condition and the fat would then diseolve a considerable amount of ether and chloroform which would tend to prevent solidiha-tion and the consequent rise of density ; as his solids-not-fat were calculated from the fat and density this would tend to give low results and doubtless some of his low figures are due to this cause. On the other hand his fat which was estimated by the Gerber method would be rather too high owing to the presence of chloroform in the fat.That these errors are actually caused is shown by the following figures ; a milk in which the fat was liquid and which was a little frothy was used. The fat by Gerber was 3.85 and 3.90 and after the addition of ether-chloroform it was 4.02 4.05 and 4-05. The specific gravity was 1.0319 and remained the same after the addition of ether-chloroform ; next day the specific gravity of the original milk had risen to 1.0327 while that of the preserved sample was 1.0323. After eighteen hours 1 C.C. of ether-chloroform was added to 100 C.C. of the milk and its specific gravity was 1.0327 ; the specific gravity of neither milk changed during two days longer. This shows that the fat when solid does not appreciably dissolve ether and chloroform while it doeti so when liquid.This was confirmed by the fact that after three days the sample to which the ether-chloroform was added at once had an acidity of 25" and after five days of 55" while the sample which had stood eighteen hours before the mixture was added had acidities of 20" and 31" at the same times; this difference can only be due to the withdrawal of the preservative by the liquid fat. The results of Collins do not therefore afford any conclusive evidence that milk in the North of England is poorer than that in the South and do not bear out the contention that the standard should be lowered. I t will be remembered that in 1897 Professor Storch published an important paper on the '' Structure of the Fat Globules of Milk " (ANALYST xxii.197) and in the discussion I took exception to his view that the fat globules in milk were sur THE ANALYST. 185 rounded by a semi-solid membrane of mucoid substanoe. In a reoent paper (Revue Gdndrale du Lait II. No. 15 et seq. 1903) M. Beau has given 8 recapitulation of the various theories of the physical constitution of the fat globules including that of Storch with which he agrees and has given details of many experiments not included in Storch’s paper in the ANALYST ; he has further criticised my views and in doing so has used arguments which appear to me fallacious. To briefly recapitulate Storch bases his theory on the facts that he has separated a new proteid from milk ; that it is impossible to free cream entirely from proteid by washing with a cane-sugar solution or with water in a centrifuge ; that the composition of the mucoid membrane is established by a series of differences of analyses of cream and butter and butter and buttermilk as Proteid .. . . . 6.42 Aeh . . . . . . 1.03 Water . . . . . . 93.55 or thereabouts ; that on staining cream with picro-carmine and washing it a coloured layer is left ; and on the behaviour of milk with ether. I disputed his conclusions on the ground that if a layer of the composition given existed round the globules cream should contain proportionately less milk-sugar and somewhat less solids-not-fat and rather more proteids than milk which I did not find to be the case and have since confirmed this. I also showed that the behaviour of milk with ether could be explained by the assumption that the fat globules in milk after soma time become solid which in conjunction with my brother I have proved to be the case (Dairy Chemistry Appendix A.p. 338 and ANALYST xxvi. 117) and that Storch’s photo-graphs of the coloured layer round the globules did not agree with the view put forward but was in accordance with the assumption that a liquid layer was con-densed round the globule by surface energy. Beau criticises the latter assumption by saying that Storch does not think that there is a regular membrane but merely a gelatinous one and that this would be analogous to a condensed liquid layer. I must dispute this as if the gelatinous layer has the composition assigned by Storch, it must differ in composition from the surrounding serum and there must therefore be a sharp dividing-line between them which does not exist in Storch’s photographs.Many of the diatoms and alga are surrounded by gelatinous layers and these can be sharply stained though gelatinous ; while Storch’s photographs show a gradual merging of the coloured layer into the colourless surroundings and this is exactly what would be expected in a condensed liquid layer from which the colour could only slowly diffuse. Beau answers my point about the deficiency of milk-sugar which should follow if Storch’s view were correct by saying that this supposes that the absorption of water by the mucoid layer is of a chemical nature and not a physical phenomenon affecting all the soluble constituents of milk. I would point out that the supposition is Storch’s not mine and if it is abandoned the composition-nay even the very existence-of the mucoid membrane must be abandoned too.Before describing some further observations I have made on the question of a membrane round the fat globules I propose to show thGt Storch’s observations ar 186 THE ANALYST. much less conclusive than he has assumed. He relies largely on the fact that proteids cannot be washed entirely out of oream. The question which must first be asked is Cannot solids in a fine state of division in suspension in a liquid be entirely separated from each other? I would answer this in the negative ; thus, Portland cement and Kentish' ragstone suspended in a liquid of density intermediate between the two undergo but a very partial separation on centrifuging.Blood (density 1.06) ie carried up with the fat globules (density 0.93) when suspended in milk serum (density 1-036) unless the temperature is raised; the lighter particles carry up the heavy ones entangled. Storch gives the density of the mucoid membrane as 1.0228. He has used for washing his cream a cane-sugar solution of 33 per cent. (density about 1-1) or of 9 per cent. (density about 1.035). The proteid under these circumstances could not possibly all be separated from the fat. As the fat separation was imperfect the proteid separation would be imperfect too but the same ratio of fat to proteid would be expected in each case were Storch's view correct ; while if as I contend the proteid is simply in suspension and unconnected with the fat globules, the separation of the proteid should be less perfect the lower the density of the medium used for washing.Storch's own figures show this to be the case as only about half the proteid per 100 grammes of fat was found with a 9 per cent. sugar solutiou as with a 33 per cent. solution and less still when water was used. His experiments therefore where they are not inconclusive tend to negative the con-clusions he draws from them. Storch also mentions that the use of a separator tends to remove the mucoid membrane from the globules. Seeing that both fat and mucoid membrane have a lower density than milk serum it is difficult to see why this should be so especially as the effect of centrifugal force ( i e . force multiplied by time) is not so inordinately greater than the effect of gravitation.I t is however quite easy to see that a partial separation should take place if the fat globules and mucoid substance are both free in the milk. I have made some observations which are not in accord with Storch'e view. It is evident that a substance of the composition of his mucoid membrane should not have the same refractive index as milk serum and a layer of a thickness of one-tenth of the radius of a globule should therefore be visible. I have examined milk under various conditions of staining and with powers up to 3,000 diameters and have failed to see any layer. I n milk cream and the serum from butter I have seen, however many solid particles quite separate from the fat which stain differentially. If Storch's view is correct that the mucoid membrane loses water when heated, the mean density of the fat globules should increase on heating.I have found a mean percentage of fat in milk separated at 30" of 0.22 and in milk separated at 70" of 0.08 while Storch's theory 'would rather indicate the reverse. Further milk heated to 70" cooled immediqtely to 30" and separated at once gives identically the same percentage of fat as that separated at 30° and this is not in accord with Storch's theory. More '' separator slime " should be removed at 70" than at 30" and it should contain less water at the higher temperature. The fat globules of milk can be broken up by suitable means and the mean diameter reduced below that of the smallest natural globule. I n doing this the mucoid layer would be removed from at least the greater number and according to I t actually contains rather more THE ANALYST.187 Storch’s theory this milk (or cream) should churn very easily ; it is however nearly impossible to churn it. According to my view the amount of serum as condensed liquid layer should be very greatly increased in cream in which the fat globules are broken up and owing to the greatly increased surface energy of the very small globules diffusion of the milk-sugar should be quite slow. If this view is true estimations of milk-sugar made by adding the minimum amount of precipitant for the proteids should be higher than those made by diluting and precipitating the proteids. ,4 cream containing20.65 per cent. fat gave 3.69 per cent.of milk-sugar with 1-3 C.C. acid mercuric nitrate added to 50 c.c. and only 3.45 per cent. when diluted with an equal bulk of water and precipitated with the same volume of acid mercuric nitrate. By thus exaggerating the effect of the condensed liquid layer definite evidence of its presence is obtained. AS all Storch’s observations can be explained without the rtssumption of a mucoid membrane 8s his experiments are not themselves wholly in accord with his view and as other experiments are against it the theory of the mucoid membrane round the fat globules must be considered as disproved. DISCUSSION. The PRESIDENT (Mr. Fairley) said that as far as his own experience went in the West Riding of Yorkshire he had found no such difference in the quality of the milk as Mr.Collins had suggested in his recent paper before the Society of Chemical Industry. At about the same time Mr. Herbert Ingle who was then a member 01 the staff of the Yorkshire College at Leeds had also obtained at the Garforth Experi-mental Farm some results of a similar character which however he (the President) could not help thinking were rather exceptional. The question of the interval between the morning and evening milkings was a somewhat complicated one. The COW was often treated as though it were merely a milk-making machine but the primary purpose of the milk was to feed the young animals and when the intervals at which the milk was drawn off were lengthened as compared with the natural intervals it seemed obvious that irregularities in the quality of the milk must result.Conditions of teiiiperature and exposure as was shown in the courae of the evidence before the Butter Regulations Committee had a great deal to do with the quality of the butter and milk produced and this would also be influenced by the time and mode of feeding time of lactation and possibly other factors that were not yet known. In connection with the question of the influence of geological conditions he would like to ask whether the ash of these milks had been investigated and whether there was any perceptible difference as regards ash in the milk produced on different formations. I h . VOELCKER said that it was satisfactory to those who whether on the Milk Standards Committee or otherwise had advocated the maintenance of a high standard with regard to milk to find that their views were so fully borne out by these results of Rlr.Richmond’s. I t would however be of particular interest to know what had been the effect c?f such an exceptional season as that of 1903 on the com-position of milk. The season had been one in which grass had been very plentiful, but more or less watery in nature snd roots alsa had been exceptional in thei 188 THE ANALYST. composition. Nevertheless the average figures of Mr. Richmond were practically the same as in the preceding year. One would also like to know whether the figures that Mr. Richmond obtained in the different periods of the year showed any marked differences as compared with the corresponding periods of previous years. He was afraid he could not quite follow Mr.Richmond in the conclusions he drew with regard to the influence of geological surroundings. As a matter of fact the green-sand was quite different in character from the chalk for aa he knew from his own farm the greensand contained very little lime indeed. At all events if he were a dairy farmer he would much rather have a farm on the new red sandstone than one on the upper greensand or on the chalk. The real point was the nature of the herbage grown and it was well known that neither the greensand nor the chalk gave good pasture land or land very suitable for dairy farming generally. Although it might be granted that individual samples or even a series of samples might give actually a higher percentage of fat yet such small differences as were here shown sank into insignificance beside tho difference in the general yield of milk that would be produced on farms situated on one or other of these formations.He had read Mr. Collins’s paper but was not altogether inclined to agree even with its general conclusions for in the milk of individual cows such wide variations occurred that it was really not safe to draw any general conclusions therefrom. Mr. L. MYDDELTON NASH inquired what was meant by the expression degrees of acidity. The PRESIDENT asked whether Mr. Richmond had noticed any constant dif-ference in the milk obtained from different parts of t.he country. Mr. RICHMOND in reply said that with reference to the President’s last question, these figures seemed to show that there was a difference. A large portion of the milk came from the district comprising the middle of Berkshire and a large portion of Wiltshire which was mainly on the chalk and upper greensand and these two forma-tions practically represented one district.Further north the new red sandstone extended over a large portion of the North-West of England including Cheshire, whence some portion of the milk was drawn. Speaking of Wiltshire reminded him, however of the famous Stratton herd the influence ole which would probably be felt over a considerable part of that district and would have something to do with the milk from there being of better quality. I t was quite true that the cow was often regarded merely as a milk-making machine. Artificial selection had much influence on milk production and probably :ts time went on its effect would be actually to con-vert the cow into a milk-producing machine of a more and more perfect kind. -in interesting point in connection with the effect of temperature was that a sudden cold day after a series of warm ones was almost invariably accompanied by a decrease in the quantity of milk yielded; but at the same time the milk contained a higher pro-portion of fat than usual. That seemed to show that the total quantity of fat produced was more constant than the total quantity of milk. He had not he was sorry to say the proportions of ash in the samples as this determination was not made in the majority of cases; and when it was made the samples were often mixtures of various milks. With regard to the eflect of season he did not think he had ever noticed two years in which the results The converse also was to some extent true 190 THE ANALYST. figure. It is hardly necessary to give any description of the construction as the illustration sufficiently explains itself. The blades of the propeller have no twist, and thus simply tend to swirl the beer round ; this motion is opposed by the flat framework the result being that the beer is thoroughly beaten or churned with liberation of the excesa of the dissolved gas

ISSN:0003-2654    

DOI:10.1039/AN9042900180

出版商:RSC    

年代:1904

数据来源: RSC

摘要:

190 THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. A Source of Error in Optical Sugar Analysis. F. G. Weichmann. (School of Mines Quarterly, 1904, xxv., 183-193.)-The presence of the lead precipitate formed in clarifying cane-sugar solutions is a source of error which has been known for years, but which is usually ignored. From the results of experiments described in this paper, it is seen that the volume of the precipitate varies from 0.05 C.C. to 1.1 c.c., no two samples of sugar giving equal amounts of precipitate. The most voluminous precipitates are not always obtained from low-grade sugars, and the composition of the impurities in the different kinds of cane-sugar must vary, for the specific gravities of the lead precipitates differ widely, from 1-65 to 4.38.An average of + 0.25O Ventzke may be taken as the average plus factor of error from this cause. w. P. s. Estimation of Fat in Cheese. B. Sjollema. (Chemisch Weekblnd, 1904, No. 29.)-The author considers that the difficulty of extracting the whole of the fat from cheese dried at 100' C. is due to its becoming incorporated with the casein, which latter coagulates at a high temperature and becomes horny. He therefore concludes that it may be possible to secure good results if the heating be avoided. He tried the three following methods of estimating the fat. ( u ) The cheese was ground both with and without sand, dried for an hour at about 100' C. in a current of gas, and subsequently extracted in a Soxhlet apparatus with ether.After evaporating the ether off, the fat was dried for an hour and a half and weighed. ( b ) This is similar to method a ; the cheese was, however, not dried at 100" C . , but in a vacuum exsiccator over sulphuric acid. ( c ) The Method of Bondzynski.::: The purity of the fat extracted by all these methods was ascertained from its Taking into account that there is always a little decomposition The agreement between the methods b and c is fairly satisfactory, but method The sample No. 2 wa8 not ground up with sand, and this serves refractometer figure. caused by the drying at looo C., the agreement is satisfactory (see following t.able). a gives low results. t o explain the difference of 0.75 per cent. between methods c and b. * For description of this niethud see f'~1lowi11g abstract, p.192.THE ANALYST. 191 Number of Sample. 1 2 3 4 5a .~ _ _ Method a. -- 12.6 13-4 17.0 3.2 12.7 12.1 15.0 Method b. 16.55 16.6 18.4 5.8 15.4 15.6 17.2 I Method c. _ _ 16.0 17.35 18.35 5.4 15.6 17.6 - Refractometer Figure at 25" C. Method a. __. _ _ _ _ 53.2 52.8 53.8 54.3 Method b. 53.8 53.0 54.3 56.0 - -____- Method c. 52.8 53.5 55.0 54.3 Sjollema found that the addition of a little 96 per cent. alcohol (5 C.C. for 3 grammes cheese), very much facilitated the grinding of the cheese. He tried three different methods : The mixture was washed with a little ether, dried in a vacuum exsiccator, and the fat extracted in a Soxhlet apparatus. (p) Similar to a, but filter-paper instead of sand was used to absorb the moisture. (6) The cheese was ground with a little alcohol, and brought at once into a flask After standing some hours with repeated shaking, the (a) The cheese was ground up with a little alcohol and mixed with sand.with about 50 C.C. ether. ether was filtered through a very dose filter, and the fat determinated. The results were as follows : Number. Method (Bondzynski), 17.6 per cent. 16.8 ,, 13.0 ,, 28-0 ,, Method a. 17.2 per cent. - - Method 8. 17.3 per cent. - - Method 6. - 16.8 per cent. 13.1 ,, 28.0 ,, To obtain the result with method p it was found necessary to extract twice with ether. More fat is also extracted when the mass is ground up repeatedly with sand. These results sbow that by using method 6 the fat is totally dissolved, and that it is not advisable to dry the mass before extraction, not even in an exsiccator.When using 50 C.C. ether for 3 grammes of cheese the whole of the fat is dissolved in the ether in a few minutes. I t was found that the presence of the small quantity of alcohol used did not influence in any way the purity of the fat extracted. J. J. L. v. R. Estimation of Fat in Cheese and Foodstuff'. H. L. Visser. (Hoorn 1. CHEEsE.-The author hw compared three methods for the estimation of fat in Chemisch Weekblad, 1904, No. 29.) Dutch cheese.192 THE ANALYST. (a) The cheesezwas ground up with sand, and dried at 100' C., the fat being subsequently extracted with ether. ( b ) The Method of Bodqnski.-From 3 to 5 grammes of cheese are weighed and placed in a dry flask, 10 C.C. hydrochloric acid (20 to 25 per cent.) added, and boiled for about ten minutes. After cooling, a known quantity of petroleum spirit (boiling-point 50" to 60" C.) is then added, the flask closed, shaken repeatedly, and put aside for a few hours to allow the petroleum spirit solution to separate, the fat being subsequently determined in an aliquot portion of this fat.( c ) The Gerber Method.-In this series of determinations Edam cheese, made at the Experimental Farm connected with the Government Agricultural Experimental Station, was used. The quantity of milk uaed was known, also the percentage of the fat in the milk and in the whey, as well as the weight of the cheese when fresh, and after being ripened ready for the market. Eence it was possible to calculate the percentage of the fat in the cheese with considerable accuracy, and to control the reliability of the different methods of analysis.The cheese was inade-as is usual in the provinces of North Holland-with a mixture of skimmed evening milk and full- cream morning milk. Nu. 1408 1409 1410 141 1 1413 1413 1414 Ether Extraction Met hod. { E) { G} { ;;:;] { g::) { ;;:: ;- 16.9 18.1 Bondzynski Met 11 od . 21.44 19.7 18.3 19.3 19.2 19.3 19.5 Gerlwr Met hod. j 20.9 '\21-5/ 19.5 18.5 19.0 20.0 19.0 19.0 Calcnlated. 21.8 20.6 18-4 19.4 19.6 19.4 From these figures it may be seen that there is a satisfactory agreement between the calculated percentage of fat and that obtained by the Gerber and Bondzynski methods, but that the ether extraction method gives low results, the differences being t 3 per cent. Dr. Visser 8160 analysed a, sample of full-cream American Cheddar cheese, and here the results show 8 satisfactory agreement in all the three methods.Ether Extraction. Hondzynski. Gerber. Per Cent. Per Cent, Per Cent. 36-5 ... ... 36.80 ... ... 36.8 31.0 ... ... 36.88 ... ... 36.9THE ANALYST. 193 A skim-milk Gouda cheese gave : Ether Extraction. Per Cent. 2.2 ... Bondzy iiski. Gcrber. Per Cent. Per Cent. ... 5.5 (3.83 \ 144s j * * - ... Several analyses were made in order to ascertain if the composition of the fat was altered by the boiling with hydrochloric acid, and it was found that no decomposi- tion took place. The author therefore recommends the methods of Gerber and of Bondzynski. 2. FOoDsTuFFs.-The method of Bondzynski cannot be used for foodstuffs containing cellulose, since, on boiling with HCl, these yield a thick magma from which the fat cannot be extracted by shaking out with petroleum spirit.He there- fore uses the method proposed by Berntrop for bread: 5 to 10 grammes of the sample are gently boiled for half an hour with 100 C.C. of HC1 (10 per cent.) in a beaker, covered with a clock-glass. After being cooled and distilled with water it is filtered, and the residue is washed with water until it has a neutral reaction. The wash water is then removed as completely as possible, the filter placed in a thimble, and dried at 100" C. in a current of gas. Subsequently the fat is estimated in the usual way by extraction with ether. The iodine value and the refractometer figure of the fat are also taken : Maize ...... Linseed cake ... i ) 1 ) ... Linseed meal ... 9 ) i i .. 9 1 1 1 ... 1 1 1 1 ... Rice meal ... . . . Meat meal ... Ground-nut cake? Gluten meal ... Gluten food ... Rape-seed cake . . . Cotton-seed meal.. . (Arachis) . . . 4.57 8.2 5.08 9.2 9.5 8.9 2.27 15.0 11.2 8.2 6.73 2.5 11-06 9.34 I 91.2 91.3 87.3 86.3 - 48.9 at 40" C. 63.5 at 40" C. - 60.0 at 40°C. 5-21 8-96 5.56 9.8 10.12 9.41 (3-20 15.52 9.7 -\ 3.37 (1;:: 8.1 { E;) 4.82 12-10 10.86 108.4 189-1 17 9.9 - - 86.6 132.3 109.7 108.9 92.8 90 -3 87-0 86.3 47.5 at 40" C. 65.5 at 40" C. 60.5 at 40' C.194 THE ANALYST. It will be seen from these figures that the HC1 method always gives the higher results, and especially so in the case of samples containing gluten. The fat from the meat meal was also found to contain kreatin.The fat of the ground-nut cake consisted almost entirely of free fatty acids. These facts may serve as an explanation of the high results given by the extraction methods. The fat obtained from linseed cake after boiling with HC1 was shown to be pure from its iodine and saponification values and its refractometer figure. For those foodstuffs containing molasses, which are composed of linseed cake meal, the only reliable method is the Berntrop one. J. J. L. v. R. The Composition of Meat Extracts and Yeast Extracts. J. GraE (zeit.fiir Untersuch. der Nahr. uitd Genussmittel, 1904, vii., 389-392.)-Frorn the results given in the following table, it will be seen that the chemical composition of yeast extract does not greatly differ from that of meat extract.For the determination of the xanthine bases Micko's method (ANALYST, this vol., p. 158) was employed : Make. MEAT KXTKACTS. ' I Praerie " Extract .. , Flagge " Extract .. Armour's Extract .. . " Terton " E x t r a c t , fluid ... "Terton" E x t r a c t , solid,, . . . . . . " Bolero Extract, fluid,, . . . .. . ' I Bolero E x t r a c t, solid ... ... Cihil's Extract ... Rio Boiiillon ... ... Tsssen Bouillon . . . Armour's ' I Vigoral " Armour's ' I Beef Juice " A r ni o u r's " Soluble I3cef" ... ... YEAST EXTRACTS. Siris . . . . . . . . Pana . . . . . . . . . Bcdu in ... ... 0l)ron . . . . . . . . , Ovos, fluid .. . .. , ,, solid ... ... Sitogen, fluid ... ... ,, solid ... .., Biou, h i d ... ... ) ) solid ... ... % 16.12 21 *37 21-56 61 *22 16-93 64.77 16.91 63.86 66-11 ti5 '62 55.12 57.79 20'65 28.45 60.52 55.81 66.50 71.09 25'99 61 -5 1 35.43 31 '73 27-92 _I % 9.74 10.01 9 -32 3.64 i.91 2-49 9'94 3.85 1.85 1'89 5.21 4.97 9-56 7.22 1.53 2-67 2.05 2.97 5.71 1 '98 5 -33 4 '54 6.68 z i 22 qz i E - % 2.26 2-78 2-58 1-42 0.82 0'60 1 *98 1.91 0.29 0.92 0.28 0.63 1 *58 0.50 0.19 0.33 0 -29 1-18 0.33 1-41 0.71 1 *02 0.28 5i 23 :; Q hd 3% - % 5-65 5-21 2-97 1 *37 1 *76 0.92 1-98 2-47 0 **52 0'42 0'49 0-53 5.88 2-68 0'58 1'19 0.83 3-03 0.85 1 -79 2.20 3.84 1 -38 - kLt 55 %$ 2r.G u K % 1-38 1.35 1-58 1.20 1-24 3.36 3-48 3.35 1-76 0'34 0-47 D -36 0.39 0'53 0'41 0.27 0.3c 0.2: 0'3( 0'31 0'3: 0'4: 0.26 x 13'90 19'73 20 -25 15'37 23.66 16'69 17-49 13'90 15.43 25 '1 4 16.27 13-67 12.75 15.15 21 '5C 19'4.E 17'4% 25'54 17*3( 22'9: 20.6: 21'5f 2 o a 9 .- 05 2 32 8-7 a- 0 s % 3'65 4 '64 5'01 1 -89 4'75 - - 3'58 0'84 ' L ' i l 2.58 3.09 6'9:3 1.49 2'68 1'99 3 '29 5-67 2-35 5.49 3'65 5-07 - - w. P.s.THE ANALYST. 195 On the Valuation of Quinine by Andre’s Reaction. E. L6ger. (Journ. Phurnc. Chim., 1904, xix., 434-435.)-The author describes a series of experiments which show that up to a certain limit the poorer the solution is in quinine the brighter is the coloration given by AndrB’s reagent (ANALYST, this vol., p. 160). He concludes from thie that the colorimetrical method given by the Swiss and Italian Phsrmacopaeias ought to be abandoned. C. A. M. Estimation of Lead in Citric and Tartaric Acids, and in Cream of Tartar. C. T. Bennett. (Chemist and Druggist, 1904, lxiv., 633.)-The following method is proposed, being based upon the coloration produced by adding sodium sulphide to ammoniacal solutions of the acids or cream of tartar. Ten grammes are dissolved in 15 C.C. of water, 25 C.C. of a 10 per cent. ammonia solution are added and the volume diluted to 50 C.C. One drop of a 10 per cent. sodium sulphide solution is now added, and the coloration produced is matched in Neesler glasses by adding from a burette a standard lead acetate solution (containing 0.0001 gramme of lead in 1 c.c.) to 50 C.C. of water to which a drop of sodium sulphide solution has previously been added. If iron or copper be present, the addition of 1 C.C. of a 10 per cent. potassium cyanide solution is necessary. A yellow coloration sometimes caused by the potassium cyanide may be matched before adding the sodium sulphide, and the amount of standard lead solution so used deducted from the total quantity required. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9042900190

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年代:1904

数据来源: RSC

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THE ANALYST. 195 ORGANIC ANALYSIS. The Quantitative Separation of Pyridine Bases from Ammonia and Aliphatic Amines. (Zed. mid. Chew., 1904, xliii., 215-222.)- For the determination of pyridine bases in commercial ammonia 100 to 200 C.C. of the sample are diluted with an equal volume of water, and added to dilute sulphuric acid containing a few drops of a solution of Patent Blue, V.N. (as indicator). The strongly acid liquid is evaporated nearly to dryness and mechanically shaken for ten to fifteen minutes with a sufficient quantity of freshly-prepared sodium bicarbonate solution and an equal volume of ether. The ethereal layer is withdrawn and the aqueous layer again shaken with a fresh quantity of ether. The united ethereal estracts are filtered and thoroughly shaken with an excess of $G sulphuric acid after the addition of a few drops of a 1 per cetit.solution of I’crte?2t IlZue. Sodium chloride is then added in excess, and the liquid titrated back with & sodium hydroxide solution. Under these conditions the end reaction with this indicator is very sharp. I t is advisable to make a third extraction with ether and to titrate the extract as described above, to insure that no pyridine remains in the aqueous layer. The test experiments described show that this method gives accurate results. In determining pyridine bases in ammonium salts 50 to 100 grammes of the finely- powdered salt are treated with 25 to 30 C.C. of water, the solution neutralized, and mixed with a sufficient quantity of pure sodium bicarbonate solution and extrwted J.Milbauer and V. Sta&k.196 THE ANALYST. with ether, as in the case of ammonia solution. If only very slight traces of pyridine are present a larger quantity of the finely-powdered salt should be extracted with hot alcohol, the alcoholic extract acidified and distilled, and the residue treated 8s described above. Salts of pure amines behave like pure ammonium salts in yielding no alkaline base to the ether. C. A. M. The Constituents of the Essential Oil of Californian Laurel. F. B. Power and F. H. Lees. (Proc. Chem. Soc., 1904, xx., 88.)-The Californian laurel, Umbellu- Znriu Califomica (Nuttall), is an evergreen tree growing in California and Oregon. I t is also known as “ mountain laurel,” “cajeput,” ‘( spice tree,” 6 L Californian olive,” “ Californian bay-tree,” and ‘‘ pepper-wood.” The essential oil of the leaves has a pale yellow colour and an odour which is at first agreeably aromatic, but becoming exceedingly irritating when strongly inhaled.I t has a specific gravity of 0.9483 at 16” C. and [ ~ ] , - 2 2 ~ in a 100-millimetre tube. The oil is completely soluble in 1.5 parts of 70 per cent. alcohol, and contains a very small quantity of free fatty acids, including formic acid. The essential constituents of the oil were found to be: cineol, 20; eugenol methyl ether, 10; pinene, 6 ; eugenol, 1.7; and umbellulone, 60 per cent. The latter is a new, unsaturated, cyclic ketone, having the formula C,,H,,O. I t is a colourless liquid with a mint-like odour, having in a marked degree the pungency of the original oil.I t boils at 219 to 220” C., has a specific gravity of 0.9581 at 15” C. and [aID - 37”. Veratric acid and a very small amount of safrol were also present in the original oil. The amount of esters is inappreciable. w. P. s. The Detection of Cryogenin in Urine. R. Courand. (Jount. Pharm. Chim., 1904, xix., 344-347.)-Various colour reactions have been described for the identifica- tion of cryogenin, or metabenzyl-amidosemicarbazide (ANALYST, xxviii., 295 ; xxix., 47), and several chemists have stated lhat its presence in urine is shown by a green coloration with Fehling’s solution. The author, however, has found that an emerald green colour is frequently obtained with normal urines, and not invariably with the urine of those who have taken cryogenin.Of all the recommended reagents the ordinary phosphomolybdic reagent ie the only one that has given satisfactory results in his hands. On adding 2 to 4 drops of this reagent to 10 C.C. of urine containing cryogenin a greenish-blue coloration (with sometimes a blue precipitate) is obtained. For isolation of cryogenin 3 litres of urine are evaporated with neutral lead acetate, the precipitated substances filtered off, and the filtrate evaporated with purified sand. The residue is extracted with chloroform, the extract evaporated to dryness, and the viscous residue extracted with petroleum spirit. The new extract is filtered and the filtrate left to evaporate, first in the air and finally i7z vacuo, until the prismatic crystals of cryogenin are obtained. The most characteristic micro- chemical test for these is the violet colour with green fluorescence given by sulphuric acid containing formaldehyde.THE ANALYST.197 The author's experiments have shown that a single dose of cryogenin is eliminated very rapidly (within thirty hours), but that after continued doses the elimination is very slow. Thus when 0.5 gramme was taken for five consecutive days the drug could still be detected in the urine ninety-eight hours after the last dose. C. A. M. The Determination of Total Carbon in Coal and Soil. S. W. Pam. ( J o P L ~ ? ~ . .i?ncr. Chem. SOC., xxvi., 294).-The carbon is determined volumetrically as carbon dioxide in the residue obtained in the determination of the calorific value according to the author's method (Jozwn.A n w . Chew$. SOC., xxii., 646 ; AKALYST, xxvi., 52). The material is burnt with sodium peroxide, and the resulting mass dissolved in a minimum amount of water. The liquid is boiled for five minutes to decompose the excess of peroxide completely, and is then transferred to the stoppered funnel C (see fig.). The funnel A, of 200 C.C. capacity, contains sulphuric acid of specific gravity 1.4. Acid is run in from A, filling B, which holds 125 to 135 c.c., completely, and to the zero mark at the three-way stop-cock 0 of the jacketed burette P connected with B. Exactly 100 C.C. C of air are then measured in the burette and forced over in the flask B, the greater part of the acid being returned to A. The tap of A is then closed, 0 opened, and the alkaline solu- tion run into the flask.When the liberated gas fills the burette completely, 0 is closed, the gas brought to atmospheric pressure by means of the levelling tube L, the volume read, and the gas discharged into the air, bringing t.he liquid in the burette to the zero mark at 0. The cock is then again opened so as to connect P with B, and the remainder of the alkaline solution is run into B, the con- tents of which are finally heated to boiling. Water is then added through C-until B is completely filled up to the zero mark at 0, and the total volume of gas, ininus the 100 I-i P C L P 3 3 * \ P C.C. of air introduced at the start, is to carbon. A correction must also be calculated made for the carbon dioxide con- tained in the sodium peroxide, which is determined in exactly the same way.All the water used must, of course, be free from carbon dioxide. In the results (ten) given the error ranges from - 0.13 to - 0.87 per cent. For soile, 2 grammes of I n the case of coal, 0.5 gramme is used for each determination.198 THE ANALYST. the sample are mixed with 0-5 gramme sulphur to ensure oomplete oombnstion. The error in ten determinations quoted ranges from 0.00 to 0.13 per cent. A. G. L. The Detection of Urobilin in Urine. L. Grimbert . (Journ. Pharm, Chim., 1904, xix., 425-427.)-Thirty C.C. of the urine are treated with 20 C.C. of Deniges’ mercuric reagent, prepared by dissolving 5 grammes of yellow oxide of mercury in dilute sulphuric acid (20 : 100) and filtering the solution. After standing for five minutes the urine is filtered and the filtrate shaken with 5 C.C.of chloroform. The filtered chloroform extract is then tested with the reagent of Roman and Delluc, which ie prepared by dissolving 0.1 gramme of zinc acetate in 100 C.C. of 95 per cent. alcohol, and adding a few drops of acetic acid. This reagent is added drop by drop to the chloroforni so long as a turbidity is produced, and at the moment the liquid becomes clear the characteristic green fluorescence of urobilin will be observed if that substance is present. The author states that by this method he has been able to detect traces of urobilin in urines rich in biliary products and indoxyl, these compounds being precipitated by the mercuric reagent. C. A. M. The Determination of Halogens in Organic Compounds. H. Baubigny and G.Chavanne. (Bicll. SOC. Chim., 1904, xxxi., 396-401).-The method of deter- mining iodine described by the authors (ANALYST, xxviii., 274) can also be used for the determination of chlorine or bromine, since these halogens are liberated without oxidation, and can be absorbed in a solution of an alkali sulphite. The apparatus recommended consists of a round-bottomed flask, in to the neck of which is ground a series of connected absorption bulbs, whilst a tube, m, n , d, passing nearly to the bottom of the flask, serves for the introduction of air to remove the last traces of chlorine or bromine from the flask. In making a determination, about 25 C.C. of a solution of an alkali sulphite are introduced into the bulb apparatus, and the extremity m of the tube n n’ closed by means of a stopper.From 30 to 40 C.C. of sulphuric acid are then placed in the flask, together with 1 to 1.5 gramme of silver sulphate and 8 to 10 grammes of potassium bichromate, and the whole shaken until the salts have dissolved.. When the liquid is cold, the weighed quantity (about 0.3 gramme) of the organic compound is introduced, and the flask instantly closed. In some cases the reaction takes place spontaneously, but in others the flask must be gradually heated to 135O-14Oo C. in a paraffin bath, the decomposition being complete in thirty to forty minutes. Finally, the last traces of chlorine or bromine are expelled by means of a current of air. In the case of iodine compounds, the iodic acid in the flask is determined as described in theTHE ANALYST. 199 previous commuhicatibn (Zoc. cit.). For the determination of chlorine or bromine, the alkaline liquid in the bulbs is treated with a slight excesB of silver nitrate, then acidified with nitric acid, and boiled until the small quantity of metallic silver formed by reduction of the silver nitrate has been redissolved, and the silver chloride or bromide determined in the usual manner. A series of experimental results is given to show the great accuracy of the method. c. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9042900195

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年代:1904

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THE ANALYST. 199 INORGANIC ANALYSIS. L. Dbbourdeaux. ( A m . cle Chhi. unal., 1904, ix,, 121-123.)-The determination of the amount of chlorine that can be liberated by oxides of manganese, and of the amount of hydrochloric acid required to liberate the chlorine, can be effected in one operation, which is as accurate as and much more convenient than the ordinary methods employed. I t is based on the destruction of oxalic acid by the manganese oxides in the presence of dilute sul- phuric acid. VuliictlioiL of Oxides of Manganese.-The following equations represent the reactions that take place in the industrial manufacture of chlorine, and in the author’s new method : Mn02 + 4HC1= MnCl, + CI, + H20. Mn,O, + 6HC1= 2MnC1, + C1, + H,O. Mn,O, + 8HC1= 3MnC1, + C1, + H,O. The Valuation of Oxides of Manganese.MnO, + &C20,.2H20 + H,SO, = MUSO, + 2C0, + 4H2O. Mn,O, + H2C20,.2H20 + 2H,SO, = 2MnS0, + 2C0, + 5H20. Mn,O, + H,C20,.2H,0 + 3H,SO, = 3MnS0, + 2C0, + 6H,O. Hence, each molecule of oxalic acid corresponds to a molecule of chlorine liberated. In making an estimation, from 0.75 to 1 gramme of the sample is placed in a small flask with 50 C.C. of a solution containing 35 to 40 grammes of crystallized oxalic acid, and 120 C.C. of sulphuric acid-specific gravity 1*82-(6S0 Be.) in a litre of water. The flask is connected with a reflux condenser, and gently heated over a small Bunsen flame until all the oxide has dissolved, this requiring about forty- five minutes. The clear solution is then diluted to 200 c.c., and 150 C.C. titrated Kith standard potassium permanganate solution containing about 15 grammes per litre.A parallel determination is made by diluting 50 C.C. of the oxalic acid solution to 200 c.c., and titrating 150 c.c., and from the difference between the results of the titrations the amount of oxalic acid destroyed and the corresponding amount of chlorine can be calculated. Detewuiiration of the L4itwtuzt of Hydrochloric Acid Required.-According to the above equations the amount of hydrochloric acid used in the preparation of chlorine corresponds with the sum of the sulphuric acid saturated and oxalic acid destroyed. Thus, if the residual 50 C.C. of each of the diluted liquids (used for the permanganate titration) be titrated with a standard solution of ammonia, with fluorescein as indicator, the difference between the two results will furnish a, measure of the200 quantity of hydrochloric acid required.The accuracy of this method is shown by the results of test experiments. This method might also be adapted to the valuation of the higher oxides of lead. C. A. M. On a Reaction of Lanthanum Salts. N. A. Orlow. (Farmaz. Jwrn., 1903, xlii., 1737 ; through Chem. Xeit. Rep., xxxiii., 36.)-Attention is called to the well- known action of iodine on lanthanum hydroxide, and especially on the basic salt produced by the action of ammonia on lanthanum aoetate, by which a blue colour is produced. A. G. L. Colour Reactions of Molybdic Acid. E. Poeei-Escot. (Ann. dt? Chim. anal., 1904, ix., 90-92.)---A solution of molybdic acid, or of a molybdate, gives an orange or reddish-orange colour with a solution of tannin, and by means of this reaction it is possible to detect 1 part of molybdic acid in 100,000.The solution should prefer- ably be neutral, since an excess of acid diminishes the sensitiveness of the re- action, or prevents it altogether in very dilute solutions. Resorcin, hydroquinone, guaiacol, and phloroglucinol do not give any coloration with molybdic acid ; but gallic acid and pyrogallol give similar colorations to that of tannin. In each case the colour is not modified by boiling the solution. Iron does not interfere with the reaction unless the quantity of tannin is sufficient to form the molybdo-tannate. The intensity of the colour is not proportional to the amount of molybdic acid, so that the reaction cannot be used for a colorimetric determination.Tungstic acid also gives a yellow coloration with tannin, but the reaction ie much less sensitive than in the case of molybdic acid. I t is also easy to distinguish between the two acids by the fact that tungstic acid gives a reddish-black coloration with hEmatein, whereas molybdic acid gives a precipitate. C. A. M. Determination of Boric Acid as Boryl Phosphate. F., Mylius and A. Meusser. (BeT., 1904, xxxvii., 397; through Chem. Zeit. Rep., 1904, xxviii., 78.)- Boric acid when treated with phosphoric acid yields a white, insoluble compound, which is not decomposed by heat. I t has the formula BPO,(probably po,,/O). BO\ In the determination of boric acid in foods, etc., the dilute alcoholic distillate obtained as usual is treated with an excess of ammonia, to decompose boric esters, before adding the phosphoric acid and proceeding with the evaporation.The residue obtained is heated for one hour at a temperature of 400' C. in a current of steam, and then weighed as BPO,. The method is suitable for determining boric acid in both organic and inorganic substances. w. P. s. Estimation of Hydrogen Peroxide i n the Presence of Potassium Persulphate by means of Potassium Permangsnate. John Albert Newton Friend. (Proc. Chem SOL, xx., 65.)-The author finds that hydrogen peroxide can be correctlyTHE ANALYST. 201 determined by means of permanganate, in the presence of potassium persulphate, only when the time of titration is short and the volume titrated small, whilst the concentration of the ealphuric acid added is fairly great.A. G. L. A New Reaction of Hydroxylamine. L. J. Simon. (Comp. rend., CXXXVii., 986 ; through Fham2. J011r92., 1904, lxxii., 247.)-When a dilute solution of m y salt of hydroxylamine is treated with a few drops of a dilute solution of sodium nitro- prusside and a slight excess of alkali, and the mixture is boiled, the original yellow c o h r of the solution becomes orange-red, changing to deep cherry-red. Nitrogen and nitrous oxide are evolved during the heating. The colour produced by a 1 in 1,000 solution of hydroxylamine hydrochloride may be again diluted to 1 in 1,000, a d is still distinct. Aldehydic and ketonic oximes, and the oximes of various glucoses, do not give the reaction. w. P. s. On the Cause of Manganese Deposits from Well-Waters. C.A. Neufeld. (.&it. fiir UTitersnch. der Nahr. m d GePiiissmittel, 1904, vii., 478, 479.)-The author draws attention to the frequent occurrence of deposits from manganiferons waters, and considers that this is due to the presence of C'reuothria: ?uaitganifera in the water, and probably not to Creizothris polyspora, as stated by other observers. I n one instance mentioned, the water passed through iron mains, and then through lead supply-pipes. The iron mains were found to be coated on their interior with a deposit 10 to 12 millimetres thick, and containing 69 per cent. of iron oxide. The lead pipes were similarly encrusted, but in this case the deposit contained 48.7 per cent. of manganese sesquioxide, with but little iron oxide.It has been noticed that only deep well-waters give this deposit. w. P. s. On the Quantitative Determination of Potassium in Mineral Waters. N. A. Orlow. (FW~UUZ. Joiim., 1903, xlii., 1737; through Chem. Zeit. Rep., xxviii., 36.)-The method is a modification of the colorimetric one of Lucian A. Hill, and depends on the colour produced by the action of potassium iodide on the aqueous solution of the potassium platinochloride after acidulation with a few drops of hydro- chloric acid. As a standard, a solution containing 0.518 gramme K,PtCI, (equivalent to 0.001 gramme K,O) in 100 C.C. of water is used. A. G. L. '1he Direct Estimation of Free Carbonic Acid in Natural Waters. A McGill. (Journ. dmer. Chem. SOC., xxvi., 183.)-The free carbonic acid is deter- mined at the source of the water, about 500 C.C. being generally used.The gas is liberated, as in Drown's method (ANALYST, xxviii., 323)) by forcing air, freed from carbon dioxide by previous passage through a soda-lime tube, through the water at the rate of about five bubbles per second. The expelled carbon dioxide is absorbed in bottles containing T& barium hydroxide solution coloured with phenolphthalein, the number of bottles needed to absorb the gas completely being a measure of its amount. Each202 THE ANALYST. bottle is 7 inahes high and 14 inches in diameter, and is n d y filled with solid glass balls& to $ inch in diameter. The inlet tube passes to the bottom of the bottle, and has its delivery end contracted to +'g inch. The outlet tube just paesea through the stopper. For a first trial on an unknown water three or four bottles are used, each charged with 10 C.C. of the barium hydroxide solution. It is advkable to add a little phenolphthalein to the sample of water used, since, if the current of air is too rapid, some of the half-bound carbonic acid may be driven off, when the monocarbonates formed will at once give a pink colour. The air necessary is conveniently supplied from a rubber bag of 1 quart size inflated by means of a bicycle-pump. Each bottle holds about 30 C.C. of liquid, A. G. L. Detection of Traces of Bromine and Iodine in Running Water. N. A . Orlow. (Farmaz. Journ., 1903, xlii., 1737 ; through Chem. Zeit. Rep., xxviii., 36).- Freshly precipitated silver chloride is folded up in a hardened filter-paper, and the packet, fastened to a piece of string, is immersed for twenty-four hours in the spring. If the water contains bromine or iodine, some of the silver chloride will be converted into the bromide or iodide. A. G . L.

ISSN:0003-2654    

DOI:10.1039/AN9042900199

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年代:1904

数据来源: RSC

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202 THE ANALYST. APPARATUS. A New Gasometric and Absorption Burette for Technical Gas Analysis. 0. Tollens. (Chem. b i t . , xxviii., 303).-The chief novelty in the construction of the burette described is that its upper end is closed by means of a movable piston constructedof metal and rubber, which is made to fit tightly by means of a little oil. To make it firmer, the rod of the pieton passes through a cork placed in the upper extremity of the burette. The latter is graduated in such a way that it holds 100 C.C. from the zero division to the mark ( a ) placed a little above the stop-cock; it also holds 100 C.C. from the mark ( b ) in the upper part to the stop-cock. The burette is filled with gas to be examined through the side-tube (c), the piston being first drawn up above the latter.The piston is then brought down to ( b ) , and the gas pressure is equalized by opening the stop-cock for a moment, when the burette will hold exactly 100 C.C. of the gas. The absorb- ing reagents are sucked into the burette by raising the piston and opening the stop-cock; after absorption is complete, the burette is rinsed out with water, and the level of the water brought to (a), after which the volume is read off. To render readings easier to take, a, disc with sharp edges is placed at the lower end of the piston. The burette can be obtained from the firm of Gebr. Ruhstrat in Gbttingen. A. G. L.THE ANALYST. 203 The Nephelometer, an Instrument for Detecting and Estimating Opalescent Precipitates. Theodore William Richards and Roger Clark Wells. (Amer.Chem. Journ., xxxi., 235).-The apparatus described is designed to determine the quantity of precipitates when less than 1 or 2 milligrammes are suspended in 1 litre of solution. The method depends on the facts that these Precipitates reflect light, and that the intensityof the light reflected is a function of the quantity of precipitate, other conditions being constant. The apparatus consists of the main frame A , which holds in position the two tubes con- taining the liquids to be compared, a movable top B, containing two prisms, and a, large box C, in which is the source of light. The tubes themselves are clear glass test-tubes, holding 32 c.c., and painted outside around the top and bottom with black asphalt paint in order to oblite- rate reflections from the meniscus and the bottom of the test-tube.The space between the two bands should be the same in each case. The tubes can be completely covered by the sliding jackets S, S, made of glass thickly painted, and held in any desired position by a brass spring. On the two wooden pillars which support the test- tubes scales are marked, which indicate the length of each tube exposed to the I Tmnt light when the jackets are raised. The top B is light-tight, but easily removable. I t contains a small frame, which can be adjusted to any position by the screw R. This frame holds two 15' prisms, with their thin edges ground together. By looking down through the prisms half of each tube may be seen side by side. The length of tube exposed, or the strength of the standard solution used, is adjusted until the two halves appear equally bright. An incandescent electric light is used as the source of illumination. For stirring the liquids in the test-tubes, propeller-shaped pieces of platinum foil sealed upon glass rods are used. I n determining precipitates with this apparatus, they must always be precipitated under the same conditions, preferably in the test-tubes themselves, as otherwise the time elapsed since the precipitation may influence the reading. Results obtained with known amounts of silver chloride in suspension show the method to be exceed- ingly accurate. A. G. L.:

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DOI:10.1039/AN9042900202

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年代:1904

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204 THE ANALYST. EKI~hTA.-In the table on it. 111 : Last line but two, f o r “ about al) . . . - 4”” rcnd “a,, ... about - 4”.” Last line, for ‘ ‘ v I , ’ ’ wad ‘ ‘ ? ~ l l . ’ ’

ISSN:0003-2654    

DOI:10.1039/AN904290204b

出版商:RSC    

年代:1904

数据来源: RSC