摘要:

THE ANALYST. DECEMBER, 1888. - - PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. THE above Societyresumed its meetings on the 14th ult., when an ordinary meeting was held at Burlington House, Piccadilly, Vice-President Dr. Muter being in the chair. The minutes of the June London meeting and the Country, meeting at Sheffield were read and confirmed. The following gentlemen were proposed for election : As member-R. W. Woosnam, analyst to the Dairy Supply Company. As On the ballot papers being opened, it was announced that the following gentlemen Christopher Rawson, P.I.C., F.C.S., analytical chemist, Bradford ; Dr. E. B. True- The following papers were read and discussed :- “ Determination of the Melting Points of Soap-Thickened Oils.’’ 6‘ On Condensed Milk.” ‘‘ On the Preservation of Milk Samples.” The paper announced to be read by Dr. Dupr6 on a recent river pollution case was The next meeting of the Society will be held at Burlington House on Wednesday, The papers by Messrs, Stock and Richmond will be published next month, associate-A. J. Stoney, assistant to Mr. L. Briant. had been elected as members :- man, public analyst, Nottingham. By W. F. K. Stock. By J. C. Shenstone. By H. D. Richmond. postponed. the 12th inst., at 8 o’clock.

ISSN:0003-2654    

DOI:10.1039/AN888130221b

出版商:RSC    

年代:1888

数据来源: RSC

摘要:

222 THE ANALYST. NOTES UPON THE ANALYSIS OF CONDENSED MILK. BY J. C . SHENSTONE. (Read at Meeting November, 1888.) I HAVE recently had occasion to analyse a large number of samples of condensed milk, and I venture to place before the Society an acoount of some experiments whioh appear to me of interest. In order to estimate the commercial value of condensed milk the following d a b are necessary :-Total Solids, and by inference water, Fat, MiZk-:-Suga;r, Cane-Sugar, combined proteids and ash. On opening a tin of condensed milk I pass a portion of its contents several times through a sieve of wire gauze, in order to separate any clots, and to secure uniformity of composition, and I preserve it in a well-closed bottle. No time is saved by making a solution and using separate portions, for owing to the Viscosity of the product, each separate portion has still to be weighed to secure accurate results; moreover, suoh a solution soon coagulates.I estimate total solids by diluting 0.5 grammes of condensed milk with about 5 C.C. of water, and after mixing them, dry by the water and air bath to a constant weight, but the solids of condensed milk rich in fat appear to yield the last traces of moisture even more reluctantly than natural milk, and, therefore, it is quite necessary to adopt all the precautions usually adopted in drying natural milk. Two grammes of condensed milk may be diluted with about three grammes of water for this purpose. Ritthausen’s method for estimating the combined proteids in milk gives very satis- factory resultsin analysing condensed milk.I dilute 2 grammes of condensed milk with about 400 C.C. of boiling water, precipitate the proteids and the fat by adding 3 C.C. of solution of sulphate of copper, then add sufficient solution of potash to nearly, but not quite, neutmlise the liberated acid. I collect and thoroughly wash the precipitate upon a weighed filter paper, dry, extract the fat, dry to a constant weight, and weigh ; lastly reduce to an ash, and correct by deducting the weight of the filter paper and of the ash, this latter corrected for the calculated weight of the ash of the filter paper. I find the most convenient method for extracting the fat from the proteids is by means of ether with tt Soxhlet tube; a thread can be attached to the filter paper with which to withdraw it..In washing the proteids care must be taken that they remain well spread over the surface of the filter, or in drying they may run into a mass from which it is almost impossible to eliminate both the fat and the moisture. The greatest difficulty which presents itself in the analysis of condensed milk is estimating the cane and milk-sugar. If the gravimetric or volumetric methods be employed, the milk-sugar must be always estimated before inversion, and if mineral acid be used for inversion, allowance be made for the change in the copper reducing power of the milk-sugar that follows its inversion. The precautions to be observed in estimating by means of Fehling’s solution have been fully described by Soxhlet. A method has been described by Messra.Stokes and Bodmer by which they avoided the inversion of the milk-sugar, by employing a dilute solution of citric acid for tbe For estimating fat the paper coil method gives very satisfactory results.THE ANALYST. 223 inversion of the cane-sugar, and adopting Pavy solution for estimating both sugars, but their method for inverting the cane-sugar by citric acid can of course be equally well used in conjunction with Fehling’s solution. It appeared to me that the difficulties accompanying the inversion of sugars could be entirely evaded by a process combining the use of the polariscope with the volumetric or gravimetric method, and my method having thus f a r given satisfactory results I will describe it in detail. Dilute 30 grammes of condensed milk, boil and when cool make up to 97 C.C.by the addition of water, then add 3 C.C. of acid solution of nitrate of mercury. I f now the mixture be poured to and- fro between two beakers the proteids will coagulate almost immediately, and very uniformly, yielding a perfectly bright whey on filtration. To prevent a possibility of birotation it isessential to heat the solution to boiling point, for condensed milk will by microscopical examination be found to contain two forms of crystalline sugar : (a) cubical crystals, presumably cane-sugar, (6) crystalline needles, most likely milk-sugar. Immediately sufficient whey has been separated 10 C.C. of it are diluted to 100 c.c., and retained for estimating the milk-sugar, whilst another portion should be at once examined by the polariscope, for after additicn of the mercury solution, the inversion of the cane-sugar commences, and although during the few minutes necessary for completing these operations, the loss is inappreciable, if the process be delayed unduly, loss might occur.I have, however, satisfied myself that a diluted whey containing only 0.3 p . ~ . of the mercury solution may be kept for a short period without appreciable change ; in practice, therefore, I conduct this operation last, though for convenience I describe it first.82.1 THE ANALYST. - ~ _ _ _- The diluted whey may be titrated either with Fehling solution or with Pavy soh- tion. I have found so far that the latter gives with milk-sugar very reliable results, and it offers some advantages over Fehling. One great disadvantage attached to the Pavy process has been that as soon as all the ammonia escapes from the solution oxidation commences, thus frequently bringing the experiment to an untimely end.I have sur- mounted this difficulty by a modification of the apparatus used by Messrs, Stokes and Bodmer, which I proceed to describe. I titrate the dilute whey with 40 C.C. of Pavy solution, the formula for which is given below, using the following modification of the apparatus usually employed. Fig. 1 shews that the modification consists of the reservoir B. containing strong solution of ammonia, and connected with the flask D. containing the Pavy solution; by means of this the ammonia driven off from the latter can be replaced, and the process continued for an indefinite period.It is necessary the burette be placed as shewn in the figure, that it may be well removed to one side of the flask to avoid an error due to the expansion of the contents of the burette. The Prtvy solution was standardized with milk-sugar, the purity of which was previously determined with the polariscope : so much of the whey is at first introduced from the burette into the flask containing the cupric solution as is expected should change the colour in that solution, without completely decolouring it. If there be no clue to the amount necessary for this purpose, the whey may be dropped in slowly until the change in colour is evident. Then before adding more whey one must boil until the colour remains constant, introducing fresh ammonia if necessary from time to time.The change in colour proceeds at first fairly quickly, but later very slowly. I find it is usually six or seven minutes before the coloiir can be said to be constant, and in order to be on the safe side I continue the boiling for about six minutes, then add more whey and again boil for six minutes, completing the process when the colour is reduced to an almost imperceptible blue, and after the boiling has been continued for ten minutes subsequent to the last addition of whey, I n the case of milk-sugar I find the results are not affected by the rate a t which the whey is added. It is not necessary to neutralize the diluted whey, for I have found that the presence of so small a quantity as 0-3 per cent. of the acid solution of nitrate of mercury does not appreciably affect the result.I have invariably obtained correct resulbs by the first titrations, but confirm them by a second titration, adding the full amount a t one time. A portion of the whey is now examined by the polariscope ; the indications on the scale of that instrument will be due to the combination of cane-sugar with milk-sugar, but a deduction can be made corresponding to the amount of the latter found by the Pavy test. It is also necessary to correct both for the space occupied by the fat, and the pro- teids, using the following formulae upon the data given by Dr. E, Vieth. Fat: supposing our sample contains 10 per cent. fat by weight, the necessary calculations to obtain the percentage of fat by volume is as follows :- 93:100=10:x x= l o 75.It was pointed out by Dr. P. Vieth that milk contains 3.5 to 4 per cent. proteids,THE ANALYST. 223 ~ 28- 4. 121 2.37 14.9 38.7 hence in estimating the sugar he allows 3 per cent. for the space occupied by these. I find that if I calculate that every 3.75 per cent. by weight of proteids in a condensed milk are the equivalent to 3 per cent. by volume after making the necessary calculations for these and for fat, the percentage of sugar found is approximately correct ; therefore the following is the necessary calculation for the space occupied by the proteids, suppos- ing that they are found to be 11.25 per cent. by weight : - 5 : 4 = 11.25 : x x = 9 I get more accurate results by estimating the space occupied by the proteids and the fat in this manner, than by washing the precipitate and adding the washings to the whey, both because the latter gives too dilute a solution to give satisfactory results, a t any rate with my polariscope," and further because the results are apt to be vitiated by the sugars becoming more or less inverted, when left for any considerable time in contact with mineral acid.In order to test the accuracy of my process, I prepared some solutions of cane- sugar in milk, and proceeded as in analysing a condensed milk. The following are the results :- Aaaea. Found. Error. Cane-sugar 8 grms. 7 94 grms. - *06 9.2 ,, 9.08 ,, - *12 10.5 ,, 10.59 ,, + a 0 9 9 5 7, 9.6 ,, +*I The following is a series of complete analyses of condensed milk :- Moisture . . Fat . . . . Proteids . I Ash . . . . Milk-sugar .. Cane-sugar . . Total . . . . Error . . .. 1 30.3 4.7 12.6 2.1 15-28 35.15 100.13 + 13 I I I I 24.8 4.7 12.4 2.42 15.72 38.7 26.8 4.7 12.37 2.27 14.6 39.9 26.4 11.5 12.6 2.05 14.4 29.95 25.6 10.4 10.67 1.9 14.52 33.59 -I I I I 98-$4 1 100.64 I 100.07 I 96.9 1 96.68 I I I I - 1.26 1 +.64 1 +*07 I -3.1 1 -3.33 7 26-8 10.65 11.07 1.9 14.2 32.15 96-77 - 3.33 The first four samples are brands of condensed skim milk, and the results are very close, but there is a loss in the last three samples, which are brands of condensed milk from which no cream has been abstracted. I believe that this loss may in part be accounted for by the 70 or more per cent. of greasy solid matter retaining a portion of the moisture. My process does not entirely surmount the inaccuracies which would be caused by the presence of invert sugar in condensed milk.I must confess to seriously questioning * The Mitscherlich half-shadow polariscope described by Dr. P. Vieth (ANALYST, vol. xi., p.' 141).236 THE ANALYST. whether invert sugar occurs in more than traces a t all frequently. Though familiar with the process of milk condensing, I do not know of any cause that will account for the presence of invert sugar, but should it be present an approximate idea might be obtained as to the amount present. The existence of 2 per cent. of invert sugar inthe sample would cause the cane- sugar to be estimated at 0 78 per cent. too low, and the total constituents of the samplo to be estimated a t 97-22 instead of 100. Invert sugar having about double the reducing action upon Pavy solution than that oE milk-sugar, the presence of 3 per cent, invert sugar would raise the percentage of milk-sugar found by about 4 per cent,, the total of the combined sugars found being about 2 per cent.too high, thus compensating for the loss to total solids on the wale of the polariscope. Now the normal proportion of milk-sugar to proteids in milk is not likely to exceed 5 : 3.3 or in condensed milk say 15 : 10. If therefore the milk-sugar was raised to so high a proportion as 19 : 10, one mould immediately suspect the presence of not less than 2 per cent. of invert sugar. FORMULB. Solution of sulphate of copper- Crystallised sulphate of copper . . . . t . 34-64 grms. Distilled water to . . .. . . .. . . 500. C.C. dissolve. (N.B.-This solution is of the same strength as that used in preparing Fehling’s soh t ion.) Solution of Titrate o f Mercury- Mercury .. . . . . * . .. 50 grms. Distilled water .. . . .. . . a sufficiency. Nitric acid (sp. gr. 1.42) . . . . .. 100 ,, Dissolve the mercury in the nitric acid, and dilute the resulting solution by an equal bulk of the water. Pavy Sotution- Crystallised sulphate of copper . , .. 34-65 grms. Rochelle salts .. * . . . .. 170 ,, Caustic potash . . . . .. . . 170 ,, make up to one litre with distilled water : 120 C.C. of this fluid with 400 C.C. of ammonia (sp. gr. 88) are made up to one litre. REFERENCES. Report upon Soxhlet’s researches on the quantitative estimation of the sugars by Notes on the estimation of milk-sugar in milk by means of the polariscope by The determination of mixtures of milk-sugar and cane-sugar by W.W. Stokes, C. H. Hutchinson. Dr. P. Vieth, F.C.S., F.I.C. F.C.S., and R. Bodmer, F.C.S. Pharm. Journ., 1881, pp. 722 and 757. ANALYST, vol. xiii., p. 63. ANALYST, vol. x., p. 62.THE ANALYST. 22; DISCUSSION, Dr. VEITII, in reference to the remark of the author that the whey which he pro- duced by adding nitrate of mercury was boiled beFore being put into the polariscope in order to avoid birotation, said he had never noticed birotation taking place under such circumstances in ordinary milk, and he did not think it was so with condensed milk. He did not quite catch what Mr. Shenstone meant when he said the proportion OF milk- sugar and proteids was as 5 to 3.3. 5 was rather high for milk-sugar, and 3.3 would be very low for proteids.I n milk containing 5 per cent. of milk-sugar he should expect more than 3.3 of proteids-3*S 01- 3 9 would more likely be present. The analyses given were very interesting. The most extraordinary point was, in the last three cases, the large error which was not accounted for. 'If anything were going on in the case of whole milk, why should it not happen with the skim milks as well? The only other point which perhaps wanted some explanation was the ash, which in some cases was found rather low. I t was a notable fact that the ash in milk stood in a very close relation to the solids-not-fat. It generally amounted to S per cent. of the solids-not-fat, and he had found this proportion in almost every case. Thus, in the first case, instead of 2.1 it should be 2.4 ; in the three last cases it was also too low--S*O5 should be 2.16, and 1.9 should be 2.0.It was only a small difference, but still, in four cases out of the seven the ash was too low. The whole method which Mr. Shenstone followed in the analysis seemed to him (Dr. Veith) rather cumbersome. He had never found any difficulty a t all in analysing condensgd milk by simply making a solution in such a proportion that he got the constituentsabout the same as in ordinary milk. For instance, he would take one part of the condensed milks in question and dilute with two parts of water, and treat this solution like ordinary milk-that was the simplest way of doing it. Mr. BODMER asked how long was Mr. Shenstone able to continue the boiling by adding ammonia.I n regard to the point mentioned by Dr. Veith, he quite agreed with Mr. Shenstone that it was necessary to make a thorough mixture of the condensedmilk to begin with. Either clots formed as the author remarked, or else the casein was not equally distributed through the milk; but, anyhow, he found it necessary to thoroughly mix the condensed milk before taking a sample for analysis. Mi. DAVIES said ho had been favoured with a preliminary account of the mode adopted by Mr. Shenstone and had found it to answer admirably. He had tried i t side by side with the Stokes and Eodmer process, and of course had required to repeat the process two or three times in order to get a reliable result, but having obtained that;, it was, he found, always possible to obtain it a t one operation by the modification suggested.It was, as Dr. Vieth said, a very extraordinary circumstance that with the whole milks the numbers should have come out so considerably below the 100 per cent. The explanation of Mr. Shenstone had not entirely satisfied him as to the reason, but he could not himself offer a mom satisfactory one at present. Dr. MUTER (Chairman), after complimenting Mr. Shenstone on his paper, desired to make only two remarks. I n the first place he would like to ask the author, if before setting to work to devise a new method, he had ever tried the old process originated by him (Dr. Muter) and communicated to tho Society in 1880 for the estimation of cane-sugar in milk. Several prosecutions for the addition of cane-sugar to ordinary milk (to cover its dilution) had been successfully brought upon its results.It did not require the use of any polariscope or other expensive instrument, and tbe sugar itself was directly weighed. With certain modifi- cations, suggested by experience, it was in daily use and answered all the purposes required. I n the second place he would advise Mr. Shenstone that in estimating his casein he mould probably find it much better not to dry it before extracting the fat, but That process was then favourably received.228 THE ANALYST. to follow his washing water through with strong spirit, then extract with ether and dry once and for all. Mr. SHENSTONE in reply said that asaregards the necessity for boiling the solution of condensed milk, he had already called attention to the prosencc of two forms of crystal- line sugar in that article ; the crystalline needles were most likely crystals of milk-sugar ; if so, as a fresh solution of this crystalline milk-sugar would cause an error through birotation, he recommended the precaution of boiling the solution.Natural milk contained no crystals of sugar, therefore the boiling would be unnecessary in that case. He was aware that the proportion of 5 per cent. milk-sugar t o 3.3 per cent. proteids was very high as regards milk-sugar and low as regards proteids, but such a milk might occur, and therefore, unless the milk-sugar was found in a still higher pro- portion there would be no evidence of the presence of invert sugar. Referring to the question : ‘‘ Why should the error be greater in the case of samples rich in fat than in samples .of skim milk?” he was not prepared with any further explanation a t present ; he might say that all his experiments so far had tended in that direction. With regard to the ash being unusually low as compared to the proteids, he could only say he had incinerated the sample at a dull red heat with an argand burner, possibly the proteids were not quite uniformly mixed in the sample, notwithstanding his having taken the precaution of passing it through a wire sieve.It appeared to him that the Chairman’s method for estimating the sugars possessed some undoubted advantages. I n practice he thought his own method would be found the most expeditious. He hoped to make some comparative experiments, examining the same sample by both methods, the results of which he thought should be very interesting. It was strange that Dr. Muter’s method should have been so entirely overlooked by recent literature. I n reply to a question, Mr. Shenstone said he had continued the boiling of the Pavy solution for as long as half an hour, but could not say how much longer he could have continued it without oxidation. Dr. VIETH asked Dr. Muter to give the details of his process, which had escaped the notice of many of the later members of the Society, owing to the difficulty of getting the earlier back volumes of the ANALYST. Dr. MUTER said that to go into all details a t the late hour a t which they had arrived would be tedious, but he would, when Mr. Shenstone’s paper appeared, give an abstract of the process as it appeared in the ANALYST, vol. v., and mention any subsequent improvements. In compliance with this promise he has contxibuted the following abstract :-

ISSN:0003-2654    

DOI:10.1039/AN8881300222

出版商:RSC    

年代:1888

数据来源: RSC

摘要:

228 THE ANALYST. THE ESTIMATION OF CANE-SUGAR IN MILK. BY JOHN MUTER. (For further particulars see the ANALYST, vol. v., pp. 36-40.) TEN grams, of the milk are evaporated to dryness upon 4 grams. of hydrated calcium sulphate with frequent stirring, so that nothing sticks t o the basin. The dry residue is powdered, placed in a dried filter and extracted with etlisr in the “ Soxhlet,” and the fat weighed as usual. The residue 1s transferred to a beaker, together with the filter containing it and 20 C.C. of hot (not boiling) water are added, and the whole is well stirred ; 30 C.C. of rectz3ed spirit (60” 0. P.) are then added, and the mixture is allowed to cool, stirring occasionally. When cool it is thrown on a filter, placed over a long graduated measure, and washed with p o o f spirit until the filtrate measures 120 C.C.(usually sufficient unless the amount of cane-sugar be very large, as in condensed milks). The filtrate is divided into two equal parts, and the one portion is evaporated on the water-bath in a weighed platinuni dish, and then dried a t 212‘) to constancy, weighed, slowly burned to a white sh a t a dull red lieat and again weighed (weight-tare of dish t ash) x 20=per cent. of totalTHE ANALYST. 223 sugars. In the other portion the milk-sugar is estimated by E’ehling gravimetrically by the author’s method of directly weighing the reduced cuprous oxide, and the milk-sugar so found x 20=per cent. This deducted from the total=cane-sugar. In all milks containing over 2 per cent. of cane-sugar the process is accurate, but when dealing with small adulterations the follow- ing allowances must be made :- Per cent.of cane-sugar found. Deduction to be made. Under 0.5 ... ... ... 0.5 ,, 1.0 ,, 1.5 ... ... ... 0.1 Over 0-5 but under i-; ... ... ... 0.2 :, 2 9 ) ... ... ... none. Piire milk thus treated shows a slight difference (abont -3 as a maximum) between the total sugar and the estimated milk-sugar, and therefore a limit of *5 is fixed, below which the process is not to be used, and i t is only t o bs applied when the presence of sugar can be distinctly proved by taste in the original sample. A proper training of the palate can detect the addition of any amount of sugar to milk over half per cent. As to the gravimetric Fehling and direct weighing as Cn,O, although it is apparently against all preconceived ideas, it has still stood the test of time in the author’s hands.He reiterates his opinions (I) That the only reliable reduction of copper obtained from milk-sugar !is when the ‘‘ Fehling ” is added all a t once and in distinct excess. (2) That it is quite possible to dry and weigh Cu,O with sufficient accuracy, if only the method be practised. (3) That by this process the Cu,O found multiplied by the factor *6835, gives the actual amount of milk-sugar as i t really exists in the milk with sufficient accuracy for all ordinary purposes. The author now makes some slight modifications on the original process. Thus instead of a weighed filter as originally used for collecting the Cuao, D pair of tared filters are employed so as to eqnalise any possible action of the ‘‘ Fehling ” on the paper.Again the final washing water is displaced by strong spirit, and then that is in turn displaced with a little petroleuni spirit before putting in the bath. The me of the thick pad of dry white blotting paper below the filter paper in the bath is absolutely necessary, and a slight pressure of the filter and contents between thick blotting paper before putting in the bath is now resorted to. A good quick-running filter paper should be used, and the rapidity of manipulation of the whole process should be aimed at. The author has never himself tried how far Pavy’s method would do for the estimation of the lactose, but for those who prefer volumetric work, i t might possibly answer sufficiently well. For an ordinary analyst, only meeting occasionally with sugared milks, however, the gravimetric process as detailed in the original paper (with the above modifications) is far the best and most convenient, (Conclusion o j Xociety/’s Proceedings )

ISSN:0003-2654    

DOI:10.1039/AN8881300228

出版商:RSC    

年代:1888

数据来源: RSC

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THE ANALYST. 223 ON THE RELATIVE VALUE OF DIFFERENT PEPSIN TESTS. BY JAMES H. STEBBINGS, JR. (Concluded from puge 212.) 2. We are further instructed to raise the temperature of the mixture after six hours' digestion up to and above 145" F. to destroy the peptic principle, and then the kath, with contained bottles, is allowed to rest over night. It has been shown by numerous experimenh that the peptic principle is not killed at this temperature (145" F. = 6 2 . 2 O C.), but that, on the contrary, digestion may and does continue up to 808 C., though of course much more slowly than at a lower temperature. If, therefore, n bottle containing a quantity of undissolved albumen be subjected to a temperature of 62.28 C., and that only for a comparatively short time (or during the time that the water bath is cooling), it is manifest that the peptic principle would not be injured, and that, con- sequently, digestion will progress all night.We should thus obtain a much too high and an erroneous result. 3. The next step in the process is to pipette off 10 C.C. from the settled contents of230 THE ANALYST. the test bottle, and evaporate to constant weight. Although I have found that, as a rule, the undigested albumen remaining in the test bottle settles pretty well over night, yet there is always a little left suspended in the liquid, which, if pipetted off, as it must be, would add to the weight of the dry residue obtained from the 10 C.C. pipetted off, and hence would be a new source of error. 4. We are next directed to evaporate the 10 C.C. to dryness, and in doing this tho residue chars or carbonises, owing to the free hydrochloric acid contained in the water, so that in reality we weigh a, certain amount of carbonaceous matter, instead of peptone, etc.Does this represent the amount of coagulated albumen dissolved by the pepsin ? It may, but I strongly doubt it. 5. Assuming that the dry residue had not charred, what would we then be weigh- ing ? We would be weighing a mixture consisting of undigested albumen, partially. digested albumen, and fully-digested albumen, or peptune, together with all tho intermediary products which always are to be met with in peptic digestions. Does this represent the efficiency of the pepsin, or is it not more likely that the amount of true peptone formed is an indication of the strength of the pepsin 1 The latter, in my opinion, is the more plausible explanation, especially if it be remembered that only the peptone is assimilable in the human system, while the intermediary products are notl.I n short, if we let the weight of all the products formed in a peptic digestion represent the eficiency of a pepsin, we would be obtaining a result considerably above what it ought to be. 6. As far as the calculations involved in this test are concerned, I mould say that they are very ingenious and eminently fitted to make a pepsin test as high as possible. I will not dispute the accuracy of the multipliers 'i and 8, but do not believe that their accuracy is infallible in every test. As this test was particularly got up to determine the digestive power of coo- centrated pepsins, I therefore append tests made by myself upon two such pepsins.Pepsin E.-One grain of this pepsln was found to digest 819.2 grains coagulated egg albumen in six hours. Pepsin F.-One grain of this article was found to digest 784 grains of coagulatecl egg albumen in six hours. I have found by personal experience that the accumulation of peptone during peptic digestions, hinders, and finally stops, the action of the pepsin upon the albuminoid matter entirely. If now the liquid be diluted, digestion will recommence again, and proceed until the pepsin has become inert. (I do not believe in the theory that one grain of pepsin can go on digesting to infinity.) As Manwaring lays particular stress upon this question of dilution, I think his test is a decided improvement over the U.S. P. test. The next good point in his test lies in the fact that he does not attempt to weigh the undigested albumen, as is done in the U. S. P. test, and thereby does away with a great source of error ; but instead of this he figures the amount of albumen (1) digested npon a dry basis, and then tries to convert this dry basis by calculation into albumen on t'ie wet basis. I n doing this errors are apt to occur, as I have already pointed out, but I do not think that they are errors of such magnitude as are apt to be obtained with the U. S. P. tesb.THE ANALYST. 23 1 Finally, I wish t o say a few words about a test which I consider to be the only approach to an accurate method of testing pepsin that I know of.I do not claim that this test is absolutely accurate either, as slight errors are apt to occur, which, however, do not materially injure the final result. I refer to the Kremel test, which was published some time since in the Druggists' Circular. I n devising this test Kremel has made a radical departure from the usual methods, and bases his test upon the fact that under the conditions in which artificial peptic digestions take place, pepsin alone has Chr: property of converting albuminoid matter into peptone, and that, therefore, from an analytical as well as from a physiological standpoint, the only correct method is to take the quantity of peptone produced as n gauge of the action of the pepsin; or in other words, the teat is made to resemble as nearly as possible the conditions existing in the natural process.Without going into any further detail the test is made as follows : One grm. of egg albumen (soluble) dried at 40° C. and pulverised, and 0.1 grm. of the pepsin to be tested, are placed into a 100 C.C. flask, and dissolved in 50 C.C. of 0.3 per cent. hydrochloric acid. The solution is heated to 38-40" C. for three hours, and then exactly neutralised with sodium carbonate ; it is then heated on a water bath to 90" C., and cooled after coagulation has taken place. The flask is then filled to the mark with distilled water, and 50 C.C. are filtered off and evaporated to dryness in a platinum dish on a water bath. The residue is dissolved in hot distilled water, filtered through a moist filter into a platinum dish, and the filter carefully washed. The solution is again evaporated to dryness and weighed.The peptone is then incinerated with ammonium carbonate, and the weight of the ash deducted leaves the weight of the pure peptone, or the representative of the digestive power of the pepsin. The good qualities of the above test are the following :- 1. Simplicity. 2. No guesswork, troublesome calculations, or the use of qucstionable factors. 3. No weighing of albumen dissolved in hydrochloric acid, undigested albumen and intermkdiary products along with the peptone. This is all obviated by the use of soluble egg albumen, coagulation and filtration or removal of the undigested portion as detailed above. 4. The ease with which it is possible to duplicate and still obtain concordant results.On the other hand, the objections to this process are the following : 1. The great difficulty of procuring absolutely pure soluble dried egg albumen. This source of error, however, in my opinion, is very slight, because in each test; a large excess of albumen is always used, and consequently the pepsin always has enough albumen to act upon. Besides this, it must be remembered that only the peptone formed is weighed, and not the amount of undigested albumen, as is the case with the U. S. P. test. 4. It may be objected t o this test that the results obtained are expressed by tho weight of peptone formed and not by the weight of albumen dissolved, and consequently the figures, being based upon dry peptone, will be much lower than when the result is232 THE ANALYST.expressed as so much moist or coagulated albumen. If this, however, be objected to, it is comparatively easy to obtain higher figures by a simple calculation. Assuming that the amount of dry peptone obtained is equivalent to so much dry albumen, then by mul- tiplying tho weight of the latter by 8 (Manwaring's multiplier) we would obtain the equivalent in coagulated or moist albumen. I do not think it necessary or advisable to follow this course, as it involves the use of a multiplier which, as already pointed out, is questionable. 3. It takes a little longer to make a test by this process, but if accuracy is thereby gained the process is to be preferred, To further illustrate the test, I append the following results, obtained with com- mercial pepkins : Papsin Q .. . . . . ,) E . . . . . . ,, P cryYtal . . .. ,, C (suxharated) . . ¶ > H * . .. .. ,, A (saccharated 1 ) . . ,, A (saccharated) . . ,, D plain, soluble . . ,, D pure, another Eimple ,, I (saccharated) . ,. ,, K (saccharated) . . 11 * * . . . . ,, D pure, scales .. ,, S French . . . . .. .. .. .. .. . . . . .. .. .. * . .. . . .. . . . . . . . . . . . . . . .. . . . . . . .. .. . . .. . . . . .. .. .. .. .. .. . . .. .. - e .. Peptone formed from 0.1 grm. pppsin in 3 hours. . . 0.5844 . . 0.4972 . . 0.4722 . . 0.4682 . . 0.4676 . . 0.4598 . . 0.4370 . . 0.4246 . . 0.3470 . . 0.3250 , , 0,3146 . . 0-2780 . . 0.1848 . . 0,1738 These tests were all made with the same quantity of pepsin, whether the latter was saccharated or not, and, I think, are a fair indication of the relative values of the different pepsins.It may be objected that this test does not do a concentrated pepsin full justice, on the ground that the latter would form a much greater proportion of peptone and thus retard if not completely arrest any further action of the pepsin upon the albuminoid matter. I n order to test this question, I saccharated samples of E, F and H respectively, according to Manwaring's directions, which is equivalent to diluting with mere acidu- lated water, and submitted them to the same conditions as before, and obtained the follow- ing results : Peptone formed from 0.1 grm. pepbin in 3 hours : Pepkin E , , * . .. a . .. .. . . 0.2620 ?, F * ' . . .. . . * . .. . . 0.1240 9 ) H * * . . .. .. .... . . 0.1250 It will be observed that in these tests the figures me considerably lower than in the former ones ; but it must be remembered that the pepsins with which the tests were made were twenty times weaker, or rather more diluted than in the previous tests, and notwithstanding this the peptone formed ia proportionally larger than before. ThisI THE ANALYST. 2 33 mould clearly show that dilution is beneficial in the case of concentrated pepsins, as it cxrects the retarding action of peptone. As the dilution in these last tests was twenty times greater than in the previous ones, we ought, by multiplying each of t,he above results by twenty, to obtain the anioimt of peptone which would be formed by using the pepsins in their concentrated forms, viz. : Pepfone that should be formed frlsm 0.1 grm.concentrated pepsin in 3 hours. . . .. . . . . . . . . . . 5*24@ . . . . .. . . . . . . . . 2.480 .. . . . . .. .. . . . . 2.500 The above figures are not, however, obtained, as has already been shown, and there- fore the calcdation is erroneous. As all the results obtained by strictly following Kremol’s directions are com- parable among themselves, I do not see how the process can well be improved upon. The mere fact that the increased dilution increases the yield of peptone is not, in my opinion, sufficient reason for condemning the process. As the conditions prevail- ing in the stomnch of a full-grown man do not differ materially as to dilution from day to day, it is safe to say that pepsins of varying strength administered to such a person will only perform a certain amount of work and no more, and that, consequently, the results obtained by this test more closely resemble the conditions prevailing inside the stomach than any other. I n conclusion, it will be seen that all the tests mentioned in this paper are siibject to faults and imperfections, some having more than others ; and, therefore, ali we can c‘o under the present unsatisfactory state of affairs is to select the one which i d least objectionable, and this, in my opinion, is the Kremel test.

ISSN:0003-2654    

DOI:10.1039/AN8881300229

出版商:RSC    

年代:1888

数据来源: RSC

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THE ANALYST. 2 33 ON SOURCES O F ERRORTN DETERMINATION OF NITROGEN BY SODA- LIUE, AND MEANS FOR AVOIDING THEN. BY W. 0. ATWATER. (Continued from page 215.) Loss of Nitrogen in Distilhion Products as indicated by Colouration of Acid Solution in the Nitrogen Bulb. It is frequently urged, e.g. by Johnson and Jenkins," that the combustions should be so conducted as to avoid any considerable discolouration of the acid solution, since the colouring matter may contain nitrogen. I have been at no little pains to learn how to insure this result. I n how far it may ba accomplished by the use of slaked lime, as suggested by Johnson, I am unable to say, having had no experience. One of my asJistants, Mr. G . P. Merrill, made, a t my suggestion, a considerable number of combus- tions with nitrogen-free stear in at different temperatures, with varying degrees of rapidity and different lengths of anterior layers of anterior soda-lime.In general we found that the more the gaseous products of distillatmion in the tube were brought into contact with the soda-lime, the less was the discolouration manifested. But we were un- * Report OP Conn. Ag'l Exp't Station, 1878, 116.234 THE ANALYST. able, even with the highest heat, very long tubes, and slow conduct of the operation, to secure a complete combustion of the distillation products ; materials with the odour of hydrocarbons being always given off in considerable quantities. These and other similar experiences gave me the impression that the largest conveniently practicable contact between the gaseous products of distillation and the soda-lime was desirable, and on that account we practised for a considerable time the use of long tubes with a long layer of soda-lime.Several circumstances, however., have shaken our faith in the need of this precaution. One is found in the comparative results of determinations with the long and the short tubes detailed in Article IV. of this series, in which the same quantities of nitrogen were obtained with tubes of 40 cm. and closely packed anterior layers of soda-lime of 12-15 cm., as with tubes of GO-75 cm. and correspondingly longer anterior layers. The comparative results in the combustion of ammonium sulphate in the long and short tubes, cited in the same article, seem to preclude the assumption that any loss of nitxogen from dissociation in the long tubes could have compensated for what would otherwise have been a gain from more cDmplete ammonification.This effort to secure more perfect ammonification by means which tend to prevent the formation of coloured compounds was therefore without avail. Another fact which militates against the idea that colouration of the solution necassarily indicates the presence of nitrogen compounds which have escaped ammonification, is found in the results of quite extensive experience in this laboratory, in which we have taken pains to note through a period of several months the amount of discolouration in the acid solution as measured by the eye. When we came to collate these observations, which include many scores of determinations, me found to our surprise that we had, with no exceEtions exceeding the practically unavoid- able variation of duplicate analyses, as much nitrogen with the considerably discoloured and turbid as with the nearly clear and colourless solutions; nor did the quantity of nitrogen average materially less in the former than the latter. Johnson mentions that in combustions with the soda-lime made from slaked lime and sodium carbonate, as suggested by himself, ‘‘ the acid in the bulk-tube is frequently coloured more or less deeply rod.’’ On one occasion, in making some combustions with Johnson’s soda-lime, me noticed that the acid in the bulb became reddish in colour during the combustion.The soda-lime was a little moist. It was dried and the same combus- tions repeated.On another occasion I noticed a similar red colour in the solution when moist ordinary soda-lime was used. The same soda-lime was dried and the combustions repeated. The solutions were then colourless. I n each of these two cases the solution was very clear with both the moist and the dry soda-lime, and the red d o u r with the moist soda-lime was very pronounced. What the colouring matter was I am unable to state, but the observation seems to be very similar to the one by E. Salkowski, above cited, from which he infers the presence of the chromogen of urobilin. The following series of determinations of nitrogen in a specimen of (probably impure) albumen prepared from beef, include the observations just referred to as made with Johnson’s soda-lime, and may be worth citing.highest heat the tubes of the most difficultly fusible Bohemian glass we could obtain The solution then remained perfectly colourless. The combustions were conducted at what we have called ‘‘ high heat,” to wit, thTHE ANALYST. 235 would bear without bursting. The time of the combustions was about GO minutes in each case. The determinations were made by a student in this laboratory some years ago, when the investigations here reported were being entered upon. The results are given in Table I. The differences in results, which vary from 15-71 to 16.24 per cent., I presume to be due to differences in the charging of the tube. That is to say, it seems to me most probable that the low results in Nos. 3-S were due to loose packing of the soda-lime in the tube, and consequent incomplete contact of distillation products with the soda-lime.I can think of no other explanation of the wide discrepancies. There is perhaps a rela- tion between either the clearness or the colour of the solution and the apparent accuracy of the results, though it is not very pronounced. The percentages of nitrogen are calculated on water-free substance. TABLE I. Determination of Nit?*ogen in A Zliumeu. Soda-lime . . .. . . 1 Ordinary. 1 Johnson's. 1 Ordinary. .. 75cm. 75cm. 75cm. 75cm. 40cm. 40cm. 40cm. 40cm. Nearly clear. Perfectly clear. * ' I Colourless. 1 Deepred. 1 Length of tube . l l l l l l l l Somewhat turbid. Colourless. Solution . . .. Per cent. N found * Soda-lime moist. Thus in Nos, 1 and 3 the determinations were apparently correct (though there is no proof that such was the case).The solution was colourless and had but little matter in suspension. In Nos. 3 and 4, in which the soda-lime was moist, there was no visible suspended material, but the solution was red, and less nitrogen by about 0.2 per cent. was obtained. In Nos. 5 and 6, which were duplicates of Nos. 3 and 4, except that the soda-lime was dried, the solution was colourless but somewhat turbid from suspended matters, and still less nitrogen was obtained. In Nos. 7 and 8, which were duplicates of Nos. 1 and 2, except that the tubes of the latter were of extra length, the solution was somewhat turbid and the percentages of nitrogen mere small. When these results were obtained we were inclined to interpret them as confirming the idea that turbidity and colour in the solution implied loss of nitrogen.But perhaps all that they amount to is to furnish illustrations of the genaral facts that neither agreement of duplicates (compare 1 and 2 with 3 and 4) nor the clearness or turbidity, nor the presence:or absence of colour of the solutions, can be taken as a test of the correctness or incorrectness of the determinations. Although we were somewhat surprised to find, in comparing the large number of results referred to above, that the nitrogen obtained where the solutions were nearly clear and colourless averaged just about the same as where they were more turbid or coloured, yet it is after all not so strange, in view of the facts that :236 THE ANALYST. (1) Non-nitrogenous materials, such as the decomposition products of fats and carbohydrates, and probably the non-nitrogenous cleavage products of protein c3mponndu as well, may impart turbidity and colour to the solution.That is to say, neither colour nor turbidity is at all an evidence of presence of nitrogenous matters, ( 2 ) Even if the colour be due to nitrogen compounds, it does not by any means prove the presence of enough to have any material effect upon the result, since the quantity which would colour a small amount of solution might easily be far too slight to be revealed by titration. (3) Many volatile nitrogenous compounds such as we should expect to escape ammonification in soda-lime combustions, e.g. amido acids and amines, are colourless and soluble. Hence absence of turbidity or colour is no proof OF absence of non-ammonified nitrogen compounds.I do not by any means mean that turbidity and colour are not to be avoided if practicable, or that they do not indicate imperfect combustion. What I wish to urge is, that neither colour nor turbidity, unless excessive, is an indication of a bad, or their absence a proof of a good determination. The danger of loss of nitrogen through oxidation by nitrates occurring in the soda- lime as impuritiep, or introduced with the substance to be analysed, requires no discus- sion here. What has been urged regarding incomplete ammonification of nitrogen of protein compounds may be briefly recapitulated as follows : (1) Loss by incomplete decomposition would seem to be best prevented by fine pulverisation of substance, thorough mixing with plenty of soda-lime, and heating until no considerable amount of charred residue is left.(2) Loss by formation of cyanides which combine with the bases of the soda-lime, does not seem to ocxr if the substance is mixed with enough soda-lime of proper water content and properly heated. Comparison of results of properly condiicted combustions with those obtained by other methods implies no considerable escape of nitrogen in the free state. (3) There isgreat danger of loss of nitrogen in volatile distillation products which escape ammonification. With some compounds, as alkaloids and leucine, this seems extremely difficult to avoid; but with the ordinary protein compounds of animal and vegetable tissues, and with the casein of milk, the experience of this laboratory implies that complete ammonification can be insured by providing for sufficient contact of the substance and its decomposition products with heated soda-lime, (Le. with water vapour a t high temperature). (4) This needed contact is best secured by ( a ) thorough mixing of substance with soda-lime ; ( b ) use of soda-lime which contains a rather large proportion of lime, is not too fusible and does not shrink too much in heating ; ( c ) carefully avoiding a channel ; (d) providing a considerable anterior layer of soda-lime ; (e) heating this latter to dull redness before bringing the heat to bear upon the substance, and keeping it hot until the combustion is done. (5) While it is desirable to avoid the escape of matters which colour the acid sohl-THE ANALYST. 237 tion in the nitrogen bulb and render it turbid, the presence of these is not an indication of incomplete, nor their absence an indication OF complete ammonification of the nitrogen. (To be continued.)

ISSN:0003-2654    

DOI:10.1039/AN8881300233

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年代:1888

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THE ANALYST. 237 NOTES UPON METHOD8 FOR ESTIMATING THE QUANTITIES OF HOMOLOGOUS ACIDS PRESENT I N ARTIFICIAL SALICYLIC ACID. BY ERWIN E. EWELL AND ALBERT E. PRESCOTT. (Concluded from page 210.) 11.-A Method by Conversion to Phenols. When salicyclic acid and its homologues are distilled from lime tbey yield a distil- late of their respective phenols, the elements of carbon dioxide being retained by the lime, so far becoming a carbonate. Subjecting commercial salicylic acid to this reaction it was undertaken to apply to the distillate a limit test for composition of the produced phenols-namely, the test" by adding an equal volume of 9 per cent. solution of sodium hydrate, and then noting the number of volumes of water to be added to muse beginning precipitation. Experiments were undertaken, with mixtures of a fairly representative oresylic acid and good carbolic acid, to obtain limits of dilution for each 5 per cent.addition of cresol in the mixture. A cresylic acid of the market, of specific gravity 1.04, was found to yield results so far consistent that it was taken as an approximately representative cresol. Best carbolic acid of the market, with water just enough to liquefy it, was taken as phenol. From mixtures of these imperfectly pure articles preliminary data were obtained, as set forth in the following table :- 5 10 15 20 25 30 35 40 45 50 4.9 9.8 14.8 19.8 34.7 29 7 34.7 39.7 44.7 49 7 6.7 6.0 5.25 4.5 4 0 3.6 3.3 3.1 2 -8 2 6 The conversion of the salicylic acid into its corresponding phenols was done as follows : 15 grms.of the acid and an equal weight of lime are thoroughly dried, well triturated together, placed in a glass retort., put over a strong heat, and quickly distilled, * A. H. Allen, 1878 : The Analyst, 3, 321 ; Allen's " Cpmmercial Organic Analysis," 2, 551 ; Lunge's (' Coal Tar Distillation," 63238 THE ANALYST. collecting the distillate in a well-cooled receiver. To promote the distillation with great advantage, dried iron filings may be added in equal quantity to the contents of the retort. When the distillate is complete, it is liquefied by adding just enough water. The sample of commercial salicylic acid previously tested by the method of acid2 metry was subjected to this process, and the distillate tested by an equal volume of 9 per cent. sodium hydrate, and subsequent dilution with measured water, until after stirring there remained visible precipitation.Five volumes of water were required, indicating, according to the table above, some proportion of hydroxy-toluic acid between 14.8 and 19.8 per cent., and agreeing substantially with the result by acidimetry. It appears evident that a method by conversion of phenols can be made effectual for the estimation of homologous acids in the salicylic acid in use, and probably with closer results than those obtained by acidimetry. III.--Xeparation by Solubility of the Calcium Salts. The Metliocl of Williams. This method, cited in the beginning .of these notes, was the basis of the only estimation of the quantity of homologous acids in artificial salicylic acids which has come to the notice of the writers, and they have submitted it to a careful trial.The operation directed by Williams* was conducted three times successively. The products of each operation-that is, the salicylic acid of assumed purity on the one hand and the homologous acids assumed to be free from salicylic acid on the other hand-were subjected to estimation by the method of acidimetry. In each of the three operations the salicylic acid was obtained from the crystals of calcium salicylate in excellent crystals, and in each case acidimetry gave results for pure salicylic acid. The mother liquors, treated for separation of the homologous acids,? yielded acid agreeing with that described by Williams, acid differing greatly from salicylic in physical properties.This (‘ homologous acid,” subjected to acidimetry, gave, for 1 grm. of the acid, (1) 705 c.cm., (2) 699 c.cm., and (3) 697 c.cm. of the hundredth-normal solution of alkali, the average being 700.3 c.cm. By the average of these estimations, then, the “ homologous acid ” still retained 61 per cent. of salicylic acid, against 39 per cent. of hydroxy-toluic acids, and in estimation (3), where the separation was carried further than in the other t’wo trials, there remained over 50 per cent. of salicylic acid. Indeed, the process of crystallisation does not promise well for estimation, unless by some system of allowances and for an approach toward exact determination. * 1878 : Pliar. Jvw. Trans. [S], 8, 785 ; Prvc. An&. Phar. ASSO., 26, 536. t The acid not salicylic has usually been designated in the singular number, and it may be that only one homologous acid occurs in the manufactured article. But as there are three isomeric hydroxy-toluic acids, to say nothing of the hydroxy-xylenic, and in absence of any identification of these isomers in “homologous acid,” it is well to recognise their existence in the plural. Melting points of the hydroxy-toluic acids have been reported as follows :- Acid-CO,H : OH : CH,=l : 2 : 3-melting at 160° C. Acid ,, ,, ,, = 1 : 2 : 4- ,, . ,, 1 7 3 O c. Acid ,, ,, ,, =1 : 2 : 5- ,, ,, 151O C.

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DOI:10.1039/AN8881300237

出版商:RSC    

年代:1888

数据来源: RSC

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THE ANALYST. 239 MONTHLY RECORD OF GENERAL RESEARCHES INTO ANALYTICAL CHEMISTRY. F. P. TREADWELL AND H. N. STOKES. Berichte, Nov. 12, p. 3131.-Using Berthelot’s method (Con@. Rend., 83, p . 1255), d.e., absorbing GO, with caustic potash, unsaturated hydro-carbons with bromine water, and benzene with fuming nitric acid, the authors obtained discordant results, They find that the nitric acid used oxidises some of the CO present to CO,, which it absorbs (see Hasenbaoh, Journ. pr. Chem. II., 4, l), and also that the bromine water dissolves some benzene. Drehschmidt (see Jul. Post’s Chern. Techn. Analysen, p. 108, 1888) previously obtained similiar results. THE DETERMINATION OF BENZENE IN A MIXTURE OF GASES. A. L. G, THE ELECTROLYTIC PRECIPITATION OF COPPER, FR. RUDORFF. Berichte, Nov.12, 1888, p. 3050.-As is well known, copper is best precipitated eleotrolytically in nitric Mid solution. When chlorides are present the addition of nitric acid is disadvantagous. The author, therefore, attempted to electrolyse ammoniacal solutions, but obtained spongy precipitates. He obtained a hard, bright precipitate by adding 2 to 3 grammes of potassium or sodium nitrate to the solution, and then about 10 c.cm. of ammonia to each 100 c.cm. of solution containing 0.1 to 0.3 gramme copper. A. L. G. PRESERVING SOLUTIONS OF TARTARIC OR CITRIC ACID. C. REINHARD. 2eitschr.f. angew Chemie, No. 22.-Watery solutions of these acids, as is well known, do not keep well, and therefore it is the custom in most laboratories to keep the acids in the solid state and not to dissolve them until wanted.This inconvenience may be avoided by the addition of a small quantity of salicylic acid. The solution of tartaric acid employed by the author is made by dissolving 100 grammes of the crystals in one litre of water and *1 gramme of salicylic acid. These small quantities of salicylic acid, which cannot possibly interfere with any analysis, are yet sufficient to keep these solutions for years. It is, however, astonishing that salicylic For citric acid solution he uses twice as much salicylic acid. acid does not preserve a solution of sodium succinate. L. DE K. ANALYSIS OF MEAT REFUSE MANURE. J. KONIG. Zeitschr. f. ungew Chemie, No. 23.- Owing to the great difficulty of getting a proper sample it has often happened that there was a serious difference in the percentage of nitrogen got by different operators. This may be to a great extent avoided by adopting the author’s plan. 16 grammes of the manure (mixed as thoroughly as possible) are heated in a porcelain dish on the water- bath, with 150 C.C. of a mixture of 3 volumes of common sulphuric acid and two volumes of fuming acid, When everything has dissolved, the mixture is brought into a 200 C.C. h k , the dish is rinsed with acid and the whole finally made up to the mark. After proper mixing, 20 C.C. (= 1-5 grammes of manure) are now treated B la Kjeldahl, as usual. The advantage of this mode of proceeding, instead of weighing out about one gramme of the manure, is very plain. L. DE K,

ISSN:0003-2654    

DOI:10.1039/AN8881300239

出版商:RSC    

年代:1888

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240 THE A.NALYS!I!, REWARDS FOR MERITORIOUS DISCOVERIES AND INVENTIONS. WE have been requested by the Committee on Science and the Arts OP the Franklin Institute, of the State of Pennsylvania, to make known to our readers the fact that the Committee is empowered to award, or to recommend the award of, the following medals for meritorious discoveries and inventions, which tend to the progress of the arts and manufactures. The Elliott Cresson Medal (Gold) was founded by the legacy of Elliott Cresson, of Philadelphia, and conveyed to trustees of the Franklin institute. Bythe Act of the Institution, May 17th, 1849, the Committee on Science and the Arts was designated and empowered to award this medal, and the Committee decided to grant it,% after proper investigation and report by sub-committee, either for some discovery in the arts and sciences, or for the invention or improvement of some useful machine, or for some new process, or combination of materials in manufactures, or for ingenuity, skill, or perfection in workmanship.The John Scott Legacy Premium and Medal (Twenty dollars and a medal OE copper) was founded in 1816, by John Scott, a merchant of Edinburgh, Scotland, who beueathed to the City of Phila- delphia a considerable sum of money, the interest of which should b&devoted to rewarding ingenious men and women who make useful inventions. The premium is not tp‘exceed twenty dollare, and the medal is to be of copper, and inscribed To the most de8mvVing.” Full particulars will be sent on appli- cation t o Mr. William H. Wahl, Secretary, Franklin Institute, Philadelphia. APPOINTMENT. Mr, R. Bodmer, F.I.C., F.C.8., has been appointed Public AnaJyst for Bermondsey.

ISSN:0003-2654    

DOI:10.1039/AN888130240b

出版商:RSC    

年代:1888

数据来源: RSC