摘要:

PkOOEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. AN ordinary meeting of the Society was held at Burlington House, on Wednesday, the 10th alt. In the absence of the President through indisposition, the chair was taken by Mr. C. Heisch, Vice-president. The minutes of the previous meeting were read and confirmed. On the ballot papers being opened, it was reported that the following gentlemen had been elected as members :- W. W. Fisher, M.A., F.C.S., Public Analyst for Oxon and Bucks; H. Tomkins, M.D., B.Sc., Public Analyst for Leicester. The following were proposed for election as members :-George Embrey, Public ilnalyst for Gloucester; C. M. Aikman, M.A., B.Sc. As Associate, A. Pike, Assistant to Dr. DuprB. The adjourned discussion on the report of the Milk Committee was then resumed and concluded.

ISSN:0003-2654    

DOI:10.1039/AN886110061b

出版商:RSC    

年代:1886

数据来源: RSC

摘要:

62 TEE ANALYST. ADJOURNED DISCUS8ION ON THE REPORT O F THE MILK COMMITTEE AND RESOLUTION ON THE SAME. Eeveral letters from members not able to attend the meeting were read, including Br. W. Thomson and Mr. A. H. Allen. Mr. Hehner said : I would like to bring forward a few results which Dr. Vieth has obtained in conjunction with myself, both with a view to see how near two observers could agee, working independently of one another, and also to compare the results so obtained by Mr. Adam' method with those obtained by the plaster of Paris method. Dr. Vieth analysed 24 milks, and despatched a portion of each sample to me, and we did not communicato the results to each other until the whole series of analyses were completed, so that me could not be biassed in any manner. These milks were as various as they could possibly be, the fat, by the plaster method, ranging from -21 to 7~97.In all cases Dr. Vieth used coils previously extracted by ether, whilst I used coils which had not been so extracted, but I estimated the amount of ether extract in three coils, and subtracted that as a constant quantity. I found, how- ever, that my correction was not quite accurate, as in consequence of doing three coib at once the soluble matter was not completely extracted. The following were the results obtained :- Adams' extraction. extraction. Soxhlet No. Vieth. Hehner Vieth. No. 1 *25 -27 *2 1 13 2 *24 *47 .2,2 14 3 -31 -54 -24 15 4 *37 -56 -28 16 5 -31 *52 -32 17 6 -38 -54 .36 18 7 1.90 2-12 1.83 19 8 1.92 2.08 1-85 20 9 2-31 2.29 1.96 21 10 - 2.61 2.3 1 22 11 3.46 3.72 3.32 23 12 3-74 3.82 3.36 24 Adama' Vieth.3.57 3.62 4.02 4.05 3.90 4.45 5.87 7.12 7-19 8.04 8.21 - extraction. Hehner. 3-65 3.58 4.04 3.87 4.23 4.46 5-94 7.12 1-67 7.38 8-12 8.36 Soxhlet extraction. Vieth. 3.37 3'48 3-70 3.83 3-84 4.37 5-51 6.8s 7.29 7.33 7.79 7.97 As will be seen, the general tendency is that my results are somewhat higher than Dr. Vieth's ; in only one case is there any considerable difference. As I have said, Br. Vieth extracted his paper coils, whilst I made an allowance for the ether extract which, I believe, mas under-estimated, the extract for each coil amounting to *00884. Dr. Vieth had also estimated the ether extract, and got an average of about -0120, so that my correction is too small, the difference amounting to about -1 per cent.of fat. A comparison between the extrsct from paper and from plaster of Paris shows that in almost every case the amount of plaster extract was the smaller, the difference amounting on the average to very' nearly .16 per cent. Roughly speaking, we may say that from -15 to -25 per cent. more fat is extracted by the coil process than by the plaster process. It must be admitted that there is no absolute uniformity; in some cases the difference is very slight, and in others it is larger ; I should perhaps mention that no duplicate analyses were made at all, and in Home cases the samples had stood several days because I was away. We have also carried out a series of comparisons with the plaster process, which has no direct bearing upon the question before the Society, but as me have made themTHE ANALYST.63 I should like to mention the results. We analysed 61 samples partly in the way of business and partly otherwise. As is well-known, Dr. Vieth is the chemist to the Aylesbury Dairy Company, and I am their chemical referee, so that if any dispute occurs their samples are sent to me. The results are as follow :- NO. 1 2 3 4 5 G 7 S 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 2s 29 30 31 Vieth. -36 *43 *48 "76 *77 -83 1-16 1.30 2.01 3.34 3.36 3-43 3 4 4 3.45 3-47 3.49 3-50 3.52 3.53 3.57 3.57 3-5 7 3.59 3-59 3.59 3-61 3.61 3.62 3.62 3.65 3.69 Hehner. 2%;- No. -34 *02 a 4 3 *01 *51 ,03 %S -08 -68 -09 *83 -00 1-08 SO8 1-24 -06 1.99 *oa 3.37 -03 3-28 -08 3-41 *02 3.51 *07 3-28 *I7 3-38 *09 3.57 008 3.43 -07 3.47 *05 3.52 '01 3.25 *29 3-64 007 3.47 '10 3-66 -07 3-36 -23 3.48 -11 3.59 -02 3-51 -10 3-50 -12 3.57 -05 3.59 -06 3.65 -04 32 33 34 35 36 37 3 s 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 66 57 58 59 GO 61 Viethe Hehner.Differ- Remarks. ence. Differences. 3.70 3-70 3.72 3.73 3.76 3.77 3-77 3-78 3.78 3.84 4.03 4-17 4.18 4-18 4-19 4*19 4.25 4.47 4.33 4.41 4.44 4.6 1 4.66 4.69 5-58 5.72 5-86 11.47 24-31 36-60 3-1 1 *59 3-81 *11 3.77 -05 3-74 -01 3.76 -00 3.79 -02 3.75 -02 3-78 -00 3.86 -08 3-81 -03 4.13 * l o 4-19 -02 2-70 1.48 4.11 -07 4.04 *15 4-21 -02 4.21 -04 4-25 .02 4.33 moo 4.44 *03 4-72 a28 4-74 *13 4-71 -05 4.74 *05 5.49 -09 5-72 -00 5.85 so1 11-26 -21 24-27 *04 36.88 -28 0.00 in 5lcases -01 *02 -03 -04 -05 -06 -07 -08 -09 -10 -1 1 -12 -13 *I5 -17 -21 -23 -28 *29 *59 1.48 Out of 61 samples examined, in 48 cases the difference between us was within 01 per cent., in 6 it was above -1 per cent.and below -2 per cent, in 5 cases it was between *2 and -3 per cent., whilst in one case we had a difference of *59, and in another 1.48 per cent. ; in this there must of course be a blunder somewhere. I think however you will admit that in 48 cases out of 61 for the difference to be within -1 per cent., was exceed- in@y good. It seems to me that we get a very fair concordance of results if we work with the coil process, and that we get about -2 per cent. more fat out. It is pretty satisfactorily established that by the plaster process at least -3 per cent. more fat are obtained than by the old Wanklyn procem, and another -2 per cent.more by the coil method than by the plaster ; so that at least 05 to -6 per cent. more fat is obtained by the coil than by the old Wanklyn process. We think that the raising of the fat limit, and lowering of the solids-not-fat, is fully borne out by the experiments we have made. Dr. Vieth said : I might say that the filter paper which I have used has always been extracted, as well as the blotting paper which has been used for the coils. Dr. Dupr6 : Dr. Vieth said : My general practice is to take the flask off from the condenser, and put it fist on tho water bath for 5 minutes, and then lying down in the air bath for 10 or 15 minutes. I n case there is no water visible in the glass, this time would be quite sufficient to dry it, but if there is any water you must keep it there as long as you can see any, and then keep it for about 10 minutes in the dry oven.How long do you dry it, and how is it dried ? Mr. Fox : Mr. Heisch said : I think, perhaps, I can answer the question of thelast speaker with respect to oxidation, I confess that when I first tried Mr. Adams' process I was Is not this slight increase due to oxidation of the fat?-__- ______I__- 64 TEE ANALYST. -_l___l____--__l^ so struck with the colour and odour of the fat obtained that I could hardly get rid of the idea that there must be some oxidation, specially as the drying had been effected in the presence of so great a promoter of oxidation 8,s cellulose, and I confess also that ths experiments of the sub-committee on the constitution of the fat did not entirely remove the impression.I determined, therefore, to test the matter severely (almost unfairly so) in this way. From an ordinary milk residue I extracted the fat by ether, and evaporated the ether off in a flask. I then weighed the butter fat, again dissolved it in ether and absorbed the ethereal solution in one of Mr. Adams’ coils, dried it, and then let it absorb about 100 grains of water, or rather more. Dried it in the water-oven and exhausted it in the soxhlet, letting the ethw run into the same flask which originally contained the butter fat, so as to avoid loss. The ether was then distilled off and the butter fat again weighed, with the following results :- Expt. 1. Butter-fat taken 3.2 ; butter-fat after expt.3.22 Expt. 2. ,> ,, 2-38; ? 2 ,, 2.30 I may mention that the fat had deepened in colour and acquired the same odour as we have observed in that obtained by the Adams process. 3: think, therefore, the question of oxidation to any amount that affects the weight of the fat may be considered as answered. I was also curious to see if the quantity of milk employed in any way affected the results of the process. I therefore absorbed into three coils the following amount8 of the same milk, dried, and extracted them with these results :- Milk Taken. Fat obtained. Per cent. 148.06 grs.. . . . 5-36 . , , 3.62 89.64 , . . 3-27 . . , . 3.64 125.34 , , . . 9-63 * . .. 3.63 An amount of agreement, which I do not think would be obtained by most processes. I therefore had no hesitation in adopting the Adam process as satisfactory.Mr. Hehner asked whether anyone had made any experiments on sour milk. Mr. HeiRch said that was very important, and in fact the one thing which required to be worked out. Mr. Bodmer said in every case where the milks went to Somerset House they would be sour. Mr. Adams said: At the time I brought forwardmy paper it mas merelyinciden- tally mentioned that the difficulty of treating curdled milk might be got over by treatment with ammonia. I have made sundry experiments, but am not prepared to go fully into details to-night. I have made experiments on fresh milk to see if the ammonia in itself has any effect on the milk perse, and there is such an effect, but it is uniform, and I have satisfied myself as to the cause of it.The difference in the results were Without ammonia 12.81 12.82 12.70 With ammonia 12-57’ 12.61 12.63 making a very slight difference of -2 per cent., which is almost universally, in a great number of experiments, exactly the amount. That is in treating fresh milk. I con- vinced myself that this was due to some action upon the lactose, and to test this I made up a mixture of pure lactose, as you would find it in milk, and the result of drying 5 c.c.. of the milk-sugar came out almost precisely that I got about *2 per cent. less than in that treated by ammonia. I noticed, as everyone who has tried the paper process must have done, that there was a darkening of the residue, and there is that same darkening in the sugar. By a little calculation you will see that a single molecule of water would make just -2 per cent.difference in the result, and I am convinced, from the uniformity with which this came out, that somehow or other, by the treatment with ammonia, it gives up one of its molecdes of water. I am glad to make that addition, in order that others might not think I had overlooked it. In my calculations I have added -2, which I believe is sufficient to make up for ths loss which the analysis gives of sour milk so treated. Those who have not tried it have no notion of the ease of it. Even when you have a thick fungus on the milk you can treatTEE BNALYST. 65 it with you get Mr ease and comfort ; by adding 8 or 9 per cent. of ammonia, and shaking it up, a perfect emulsion, and it is as may to work as with fresh milk. .Johnstone inquired how the lactic acid was separated from the fat. Dr. Vieth said : I have made some experiments Tith lactic acid. I worked upon some which had been titrated with sodium hydrate. I took 2 C.C. of this, which would contain 107896, equal to 2.124 ammonium lactate. I treated the 2 C.C. as usual in milk analyses, viz :-4 hours on the water bath and two hours in the hot air bath ; in two experiments the results were Water bath 4 hours Air bath 2 hours 1.5722 1-5073 + 2 hours air bath + 2 hours air bath 1,4736 1-3330 1.3840 1.2704 I then took 2 C.C. of the lactic acid aolution, and added ammonia with the follow- ing results, after the same dryings. 2.0046 2.1386 2.1058 2.1472 2.0722 2-0264 It is well-known that whenever you dry lactic acid you cannot get rid of all the water contained in the lactic acid, and dry lactic acid is not formed, and that it was so in this case is certainly borne out by these experiments. Any loss that was shown by the addition of lactate of ammonia was not nearly so large aB in the case of lactic acid.Another reason from an economical point of view was, in the saving of ether. In a series of experiments by Adams’ process he had an average loas of 7 grms. of ether, whilst by the plaster process the loss was 14 grms. Mr. Hehner said : I am the seconder of the motion now before the Hociety, and do not know if I am in order in moving another amendment; but it seems to me that, after all, as we have not a eingle experiment upon sour milk, it might not be wise to definitely adopt a method which we might have to alter again, and I should like to propose that the members of the Society provisionally adopt the method and the limits recommended by the committee for the rest of the current year, and that the matter come on again for discussion at the first meeting next year.Mr. Johnstone would second thie, but The Chairman said Mr. Hehner could not move it. Mr. Baynes said he thought that, in %he absence of any proof that any other method was better than Adams’, they should adopt this, and if any analysts would not do so, and went into Court with any other, let them fight their battles themselves. I f allowed to go on provisionally for a year, it meant that an old wound would then be reopened, and they mould have to do all the work again.The results which Mr. Adams and he obtained were equally as good as those of Dr, Vieth and Mr. Rehner. Let them adopt this method altogether, and if a sour milk came up, let them take it as it came. He thought it would be a great pity to throw away all the work they had done. A h . Adams’ process was a good one, and they had proved it to be so. Dr. Bostock Hill said : We cannot any longer speak of milk containing solids (‘ not fat ” and ‘ I fat.” We know all the fat is not extracted by the Wanklyn process, andit seems to me that the only course would be, to word our certificates a8 solids-not- fat, with part of the fat, and the rest of the fat, I think, as a Xociety, we should adopt the process of Adams, as altered by the committee. It is a queationof absolute accuracy, as far as we can get it, and there can no longer be any doubt that no process but the paper one does get out the largest quantity of fat. I cannot Bee why, as a body of scientific men, we should be under the ban of using a process which we know does not give us correct resulta. As to sour milk, we ought to face the difficulty at once. The certificate must state that the milk was in a fit state for analysis. Everyone knows that the analysis of sour milk is not correct, and the only wav is to do two or three and strike an average. I f we were to set our face against such analyses, and tell inspectors that they were not reliable, we should at once do away with the question of sour milk.66 TEE ANALYST. Mr. Hehner said that, BB long as there was no fermentation, milk could be safely analysed. Mr.Heisch said that if when the cork was drawn there was any symptom of gas escaping, they might be quite sure that the analysis would be worth nothing. It was then resolved, with only one dissentient, that the Report of the Milk Com- mittee be received and adopted : andit was recommended that all analysts should use the prowas in preference to any other.

ISSN:0003-2654    

DOI:10.1039/AN8861100062

出版商:RSC    

年代:1886

数据来源: RSC

摘要:

66 THE ANALYST. ON THE COMPOSITION OF MILK AND MILK PRODUCTS. BY DR. P. VIETH, 3.C.S. Read at the Zeesting 10th Februwy, 1886. FOR the last three years, I have been in the habit of laying before you a summary of the analytical work done and the results obtained in the laboratory of the AyleBbury Dairy Company, which is under my charge. I n doing the same with reference to last year’s work, I need not enter into details as to the origin of the samples, the purpose for which they were taken, the analytical methods employed, and the like, for all this has been fully described and explained in my former papers on the same subject. (THE ANALYST, Vol. VIl, p. 53, Vol. VIII, p. 33, Vol. IX, p. 56, and Vol. X , p. 67.) I will then proceed to summarise as briefly as possible, what has been done during the year 1885.The total number of analyses made is 17,896, of which 16,031 relate to samples of Milk 1,564 9 , >, Cream 110 9 ) 9 ) Bkim Milk 45 ? ) ,$ Buttermilk 20 ’) 9 ) Butter Of the milk samples 11,389 were taken on the arrival of the milk in the dairy. The I n the preceding years the following average percentages of Total Bolids had been 120 ,, Sundries. average composition of all these samples was as follows :- found, viz :- Total Solids 13*06. Fat 3.93. Sol. n. f . 9a130/0 Spec. Grav. 1.0322. 1881 ., .. .. 4 . . . 12.80 1882 ., .. .. .. .. 13.03 1883 .. .. .. m . ,. 12.97 1884 .. .. . * .. . . 12.96 Again 3,879 samples were taken by the company’s inspectors from the men, vhen In the following table are given the monthly delivering the milk to the customers.averages for all these milk samples. AVERAGE COMPOSITION OF MILK. January 1.0324 13.22 3.98 9.24 13.1 February 1’0323 13.02 3-84 9.1 8 12.8 May July 1.0319 12-94 3.89 9.05 12.8 Sample taken-On Arrival. On Delivery. Spec. Grm. Tot. Sol. Fat Sol. n. f. Tot. Sol. 1885. March 1.0325 12.86 3.68 9.1 8 12.7 April 1.0323 19-74 3-63 9.11 12.6 1-0324 12.90 3.17 9.13 12.s 1.032 3 12.88 3-76 9.12 12.8 June August 1.031 5 13.07 4.11 8.96 13.0 September 1-0317 13.25 4*18 9.07 13-2 October 1,0323 13.41 4.21 9-20 13.3 November 1.0322 13.31 4.14 9.17 13-1 December 1.0322 13.12 3.99 9.13 12.9 Yearly Average 1.0329 13.06 3-93 9-33 12.93 -.lo.. - - - -THE ANALYST. 67 There is a slight difference between the two series of samples in favour of the samples taken on arrival, a difference which can be accounted for easy enough.The samples of the first series are taken from the top of the milk, contained in the railway churns, and though the milk is mixed in a most thorough manner, there is still the possi- bility of the top part being a trifle richer ; while the inspectors’ samples are taken from the tap near the bottom of the delivery churns at a time when some cream might have been thrown up. It is not a mere chance that the smallest differences occur in August and September, this being the time when business is at the ebb. The man charged with that work, has then plenty of time to stir the milk well for taking the samples, and delivering the milk to the customers is done in much less time. Of the 1,564 cream samples 602 refer to cream supplied by farmers on contract, and received from the company’8 own eatate.This cream was partly of poorer quality t h e fat varying from 20 to 40 per cent.-and destined to be churned into butter. The largest part of the cream supplied t o the customers was separated on the company’s premises in Bayawater. Samples were taken regularly before the cream was sent out, aa well as from the men when delivering it to the customers. Of these samples 568 and 341 respectively, were analyaed with the following results :- 1~35. January February March April June July Auguclt September October November December May AVERAGE: AMOUNT OF FAT IN CREAM. .. .. 35.9 per cent. , . .. .. . . 37-8 ) ) .. .. .. . . 37.1 ,, .. .. .. . . 37.9 ,, .. . . .. ., 40.0 ), . . .. .. . . 41.9 ,, .. * . .. . . 42.8 , y .. .. .. . . 45*2 ,, .. . . .. . . 47.8 ), ‘. .. .. . . 48-4 ,, * . .. .. . . 51.1 ), .. .. .. . . 44.6 ,) .. . * Samples taken before sent out on delivery. 36.0 per cent. 37-8 ), 31.0 ,, 37.8 ,, 39.6 ,, 41.1 ,, 43.1 ,, 45.8 ), 48*3 ) ) 49.1 ,) 50.0 ,, 44-4 ,, - II Yearly average . , 42.5 )) .. . . 42.5 t , The two series of figures agree on the whole as closely as can be expected. 8amples of akim milk and buttermilk were analped in order t o control the work of separating the cream from milk and churning cream into butter. The amount of fat left in skim milk varied generally from 02 to *5 per cent., a proof that the centri- fugal cream separators did their work very well. The buttermilk in the majority of cases contained about 1 per cent of fat and even more, which is rather too much.The compofilition of butter varied between the following limits :- Pat , , 78.06 to 89.36 average 85.85 per cent. Water 8.17 ,) 17-26 ,) 12.45 ) y Curd, etc. -28 ,, 2.17 ,. 1.04 ,) Ash . , *07 ,, 2*53 ,) *66 ,, Insoluble fatty acids were found to vary in pure butter-fat from 87.11 to 88-85 per cent., and averaged 88.08 per cent., while in three samples of oleomargarine butter,68 THE ANALYST. analysed for the sake of comparison, they were found to amount to 95.37, 94.87, and 95.22 per cent. Under the head of sundries are comprised analyses of medicinal milk preparations, water and some others. In addition to the above report I wish to make a few further remarks. FZeischmnm's formula for calculding milk resuZts.-Last year I have communicated to you two formulE worked out by Fleischmann and Morgen'which allow to calculate, the one, the percentage of fat in milk from its specific gravity and the percentage of total solids, and the other, the percentage of total solids from specific gravity and percentage of fat.These formulm were based on the assumption, that the specific gravity of pure butter-fat at 15'0. is 994. An extensive series of experiments carried out in Professor Fleischmann's laboratory at Raden has proved, however, that the specific gravity of pure butter fat varies from *9223 to -9377 and averages *93071'i: at 15OC., a rest& which is entirely in concordance with observations made by several investiga- tors in this country.Professor Fleischmann consequently altered his formulE, which stand now as follows :- I. t = 1 * 2 f + 2.665 l o " sbs l o o 11. f = -833 t - 2-22 'O0 s - 1''0 In these formulaj t = percentage of total solids f c > 9 ) > fat s = specific gravity of milk (water = 1.) Though it makes a trifling difference only whether the old or the new formike are applied, I thought it right to coinmwicate to you the corrected fomulm, which I have checked against a great number of analyses with the most satisfactory results. I am happy to say, that other analysts have likewise found the formub both correct and useful. Composition. of Froze% XiZk.-I have pointed out repeatedly, that of an originally rich milk a sample deficient in fat may be drawn, notwithstanding that an abstraction of cream has not taken place.I refer to instances where cream has risen unexpectedly, an occurrence which happens sometimes even under 80 rznfavourable conditions as the calving about of the milk on vans, carts, or perambulators in the streets, To-day I should like to draw your attention to another circumstance which may seriously interfere with the composition of milk. During the froaty weather in the early part of January one night the milk arrived in a partially frozen state, Now, I do not know if you are aware of the fact, that milk does not freeze bodily, like water for instance, but in-what may be called-a selective manner. The ice which had been formed in the milk in queBtion and which was a small proportion of the milk only, waa atrained off and thrown away.I n one churn I determined the proportion of ice present on the following morning and found it, after it had been melted, to amount to 1-2 per cent. of the bulk, the liquid part which had been strained off amounting to 98*8 per cent. In a second churn the ice was likewise strained off, but the proportion not determined. On anctlyaia the different liquids were found to be of the following composition,TEE ANALYEIT. 69 COXPOSITION OF PARTIALLY FROZEN MILK. I. 11. Liquid Part Melted Ice Liquid Part MeIted Ice Water . . 86.72 , . 91.63 . . 86-86 . . 90-46 Fat .. 4.11 . , 2.40 . . 4.08 . 3.18 Proteids . . 3.56 , . 2.40 . . 3.46 . , 2-67 Sugar . . 4-87 . . 3-05 . . 4.90 . , 3.1 9 Ash . * .74 .. -52 .. -70 .. *50 Spec. gravity 1°0320 . . 1.0245 . , 1.0335 .. 1.0235 During the winter 1880-81 the milk not only arrived in a partially frozen state in London, but ice was also formed on some cold days during delivery to the customers. Supposing a small and ignorant dealer wheels about twelve gallons of milk on a frosty morning, serves nine or ten gallons out to his customers, and brings three or two gallons home in the form of ice, would it not be but natural, that he applies some heat in order to melt the ice, and on his next delivery serves the liquid obtained, which has quite the appearance of pure milk and to which-he positively knows- nothing has been added? He would in this case sell an article, which is certainly not of the nature and substance as demanded, and he might be made answerable for such an offence against the law; but he should not be convicted of adulteration, i.e., of dishonesty.Kozcmiss.-In addition to the analyses of mares’ milk koumiss, which I brought before the Society a few months ago, I wish to-day to give you the composition of koumiss made of cow’s milk and sold under the mark of ‘ I Full Koumiss.” The proteids were determined separately, viz. casein : precipitated by lactic acid ; albumen : coagulated by boiling the fXtrate; and lacto-protein and peptone : precipitated by tannic acid in the second filtrate. Sugar was not determined, but taken by difference carbonic acid was not taken in account. -- COMPOSITION OF Cow’s MILK KOUMISS. Ash sol. insol. Age Water Alcohol Solids Fat Caaein A’bu- p 2 s t i Lg% Sugar men Peptone 1 day 88*50 *17 11.33 1-65 2.06 -30 *32 -26 6.16 *16 ‘42 1 week 90.15 -92 8.93 1.48 2-00 -22 *56 -97 3-14 -22 -34 3 weeks 90.31 1-03 8-66 1.58 1-93 -21 -74 1.39 2-23 -83 -35 3months 90.36 1.12 8.52 1.57 1-70 -09 ~ 9 1 1-94 1-79 -25 -33 The composition of koumiss of different ages clearly shows the progress of lactic and alcoholic fermentation and of the accompanying process of peptonisation, the former by the decrease of sugar and the increase of lactic acid and akohol, the latter by the decrease of casein and albumen and the increase of compounds precipitable by tannin.Of further interest is the increase of the soluble and the decrease of the insoluble part of the ash, which in my opinion is due to two causes, viz. the increasing amount of lactic acid and the transformation of casein, with which the phosphates in milk are chemically combined.Compositio~h of Old Bzltter-fat.--There seems to exist some doubt, whether the in.- soluble fatty acids in butter-fat increaae or decrease in the course of time. Withoutso THE ANALYST. venturing to decide this question, I wish to bring aome particular cases under your notice. I have in my laboratory a case with glass front hanging on the wall, in which are placed cylindrical glasses containing the component parts of milk and illustrating the composition of milk and its products. Though the case is exposed to dispersed light only, the butter-fat, contained in the arnall glass cylinders of qin. internal dia- meter, gets bleached pretty soon and attains a tallowy appearance. On the 17th Maj-, 1884, the fat, which had been in the glasses more than one gear, was taken out and analysed.A portion which was entirely bleached gave on three determinations 83.54, 83.42, and 83.60 per cent. of insoluble fatty acids, while another portion which had retained a trace of the natural colour, contained 80.95, 84-02, and 83-72 per cent. The glasses were refilled on the 31st May, 1884, vith butter-fat showing on duplicate analyses 87-37 and 87.48 per cent. of insoluble fatty acids, and this same fat when taken out on the 28th May, 1885, yielded 85.07 and 85.12 per cent. There has been then a decided decrease in the percentage of insoluble fatty acids. At the time when I mas drawing up the remarks just communicated to you, my eye quite incidentally fell upon a very old sample of butter, and I thought it of no little interest to ascertain what changes might have taken place in this case.As to the his- tory of the butter I know only so much, that several samples of one and the same lot of butter had been taken, kept and observed for some time, in order to ascertain it6 keeping qualities under different conditions. The experiments were carried out before I had c o ~ e to this country, so that the sample I am speaking of is not less than six years old. I t is the only remaining one of the lot and was, I suppose, overlooked and forgotten; it mas kept all the time in a store room. The butter-about one-half pound-was coutained in a brown coloured glass jar and loosely corked by means of a bung. That butter under such conditions should keep good for six years, of course, no- body will expect, and this particular specimen certainly was no exception to the rule.I n its upper part it mas interspersed mith a fungous growth, while the lower part, in which by the naked eye no fungi could be observed, was of rather softer consistency than butter mould be at this time of the year. The smell was very rancid indeed, though not disagremble, resembling that of Roquefort cheese. Samples of the upper and lower portions were taken, melted, and the €at filtered ; a sample of the clarified fat from the lower portion was also washed mith a carbonate of soda solution and sub- sequently twice with water. The butter-fat of the upper part, though perfectly clear; was of B brown colour. On analysis the following results were obtained :- Butter-fat of lower portion 85.34 89.22 mean S9*28°/0 71 -L'PPer 7 ) 91.2G 90.61 ?, 90*94"/, I n this case, then, the insoluble fatty acids have very decidedly increased, more especially so in that part of the butter which was interspersed with fungi. The two instances are quite distinct from each other; in the one we have to deal vitft pure butter-fat, free of foreign matter, one year old, and bleached by the action of insoluble fatty acids. ? 1 7, ,, washed 89.60 88-93 ,, 89*33O/,THE ANALYST. 7 1 light ; whilst in the other the material under investigation is butter containing beaides a high percentage of €at, appreciable quant,ities of the other constituents of milk, kept for six years, protected, at least to Rome extent, against the action of light, but attacked by an extensive fungous growth. The results of the decomposition, which the two materials had undergone, certainly do not differ to a less extent than the accompanying circumstances. I should think it not only of great interest, but of the greatest value, if similar observations made by other analysts would be put on record.

ISSN:0003-2654    

DOI:10.1039/AN8861100066

出版商:RSC    

年代:1886

数据来源: RSC

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THE ANALYST. 71 SUGGESTIONS FOR THE MORE READY EMPLOYMENT OF ADAMS’ METHOD O F DETERMINING FAT I N MILK. BY A. H. ALLEN AND W. CHATTAVAY. Read at the Xesting, loth February, 1886. TBE formal recommendation by the Milk Committee of this Society of the method of determining fat devised by Mr. Adams, has forced the process on the attention of all Analysts, including those who believe the method of fat extraction they have hitherto used to be fairly satisfactory. It being an admitted fact that most of the methods of determining fat hitherto employed are liable, under certain circumstances, to give results considerably below the truth, chemists are naturally inclined to look favourably on any process by which perfect; extraction of the fat from the milk-residue can be ensured. It must further be admitted that the conditions under which the fat is extracted in Adams’ method are such as afford a primd facie probability of thorough exhaustion of the residue.Further, from the analytical data published by the Committee since the date (December 9th, 1885) when they asked the Society to “show its confidence” by then and there accepting their recommendation to adopt Mr. Adams’ method as the official process, it appears extremely probable that the procedure in question is theoretically perfect. While preferring to reaerve a positive opinion on this point until we have had a longer and more rigid experience of the method, it appears to us that the process, as prescribed by the Milk Committee, is not sufficiently practical to render ita general adoption by the members of the Society probable, or even possible, having regard to the circumstances under which many of their analyses require to be made.The chief objections which have auggested themselves to us, and which were pointed out by one- of us to the meeting on December 9th, are :-(1) That, if the instructions of the Milk Committee be followed, two weighings aro necessarily made of each sample of milk, even though other data may subsequently show that the determination of fat is not requisite. (2.) That these weighings must be made very promptly, or the milk will have turned sour, and can no longer be fairly absorbed by the paper. (3.) That it is often practically impossible to make these weighings before the milk has commenced to change. To the first of these objections, Mr.Adams replies that, practically, the whole of the 5 C.C. measured into the beaker is soaked up by the paper coil, and hence the two weighings may be dispensed with. As for sour milk, Mr. Adam recommends the use72 THE ANALYST. of ammonia, which, he states, will restore the most curdled milk to the state of emulsion. The Committee, in the official process they recommend, make no reference to measuring, instead of weighing, the milk; and do not suggest the use of ammonia. Hence, the presumption is that they insist on the double weighing, and either object t o the use of ammonia on chemical grounds or have never realised the occasion €01- pre- scribing a process for analysing slightly sour milk. While reserving our opinion as to the accuracy and value of Adams' method of treating milk for the extraction of the fat, we have felt the absolute necessity of some simplification of the manipulation if the process is to be generally adopted ; and, 8 s the outcome of several experiments on the mechanical details of the process, we have devised the following plan of making the paper coils, which plan we venture to think an improvement of the original method :- We roll up with the paper a piece of string previously boiled with water containing a little sodium carbonate (in order to remove size, &c.), which serves to keep the con- centric folds of the coil from contact with each other.We also tie on to the lower end of the coil a piece of filter-paper about 3+ inches in diameter. This is made of thinner paper than the coil itself, and is pleated round the sides of the coil, somewhat after themanner in mhich a dispenser folds the paper cap over the cork of a bottle of medicine. This device provides the coil with a bottom, and enables us to deliver 5 C.C. of milk as fast as it will run from the measuring pipette on to the upper end of the coil, which should, meanwhile, be suspended from a suitable support. In this manner the necessity of weighing of the milk absorbed by the coil is wholly avoided.As the novelty attaching to our mode of operating really lies in the construction of the paper coil, it is desirable to describe the method of making it in more detail. The strip of paper we employ is of the same dimensions and quality as that used by Mr. Adams ; but each concentric ring of paper in the coil is kept equi-distant from the next by means of a piece of string, which is threaded down either side of the ..I..paper, about half-an-inch from the ..".. .... I edge, as shown in the accompany- ing sketch (Pig. 1). It will be i seen that there is a loop, formed by knotting the doubled string, which loop protrudes from the centre of the coil when finished, and is useful for hanging it up while being charged with milk, and during the subsequent process of drying. A small glass rod (or other suitable article) is used to roll the paper upon, the rolling being commenced at the loop-end of the strip. When the coil has been rolled as far as the last holes in the paper (B.B.), the two ends of the string are tied in a knot as close to the paper as possible.A hole is then made through the centre of the paper, immediately under the knot, and of sufficient size to allow the knot to go through. The winding of the remaining three inches of the paper is then completed, and a pleated cap of filtering paper placed over the bottom of the coil. A hole is made through this cap at the side, just where the knot occurs. The ends of the string are F I G 1 .THE ANALYST. 73 threaded through this hole, and the cap and coil are then secured by merely tying the two ends of the string round the cap. The finished coil has a diameter of Q inch, and can then be extracted with ether, in the usual way, to remove traces of resin, &c. The advantages we claim for the coils made in the foregoing manner, specimens of which we produce, are as follows :- The concentric folds of paper being kept separate by the string, the full extent; of surface is exposed, and the process of drying is correspondingly facilitated.The cap of filter-paper at the bottom, aided by the obstruc- tion produced by the string, renders it possible to pour the milk at once on to the open end of the coil while it is suspended by the loop of string. No loss by filtration of the milk through the cap has ever occurred to us. This fact enables us to dis- pense with the two weighings which militate so powerfully against the general adoption of the original mode of operation. With the modified coil, 5 C.C. of the milk can be taken up in a pipette, and at once run on to the suspended coil. The density having been previously observe‘i, the weight employed is, of course, accurately known. Although in general, and when operating on fresh milk, we consider the use of a definite measure of the sample has marked advantages, the use of a known weight of milk is equally simple. The amount to be taken can be weighed in a tared tube or small beaker, poured on to the coil, and the vessel rinsed out with a few drops of water, which in their turn are added to the coil. The last plan is equally available for BOW milk, a weighed quantity of which may be at once poured on the centre of the coil-the modified plan having a marked advantage in this respect over the coil as originally constructed. If it be considered desirable to employ ammonia, its addition to the weighed quantity of milk, before pouring on to the coil, presents no difficulty. A number of coila being charged with milk, they can be conveniently hung on rows of pins in a vertical Stone’s box, or similar receptacle, and can be kept there for an indefinite period. CONCLUSION OF THE SOCIETY’S PROCEEDINGS. F I G 2 .

ISSN:0003-2654    

DOI:10.1039/AN8861100071

出版商:RSC    

年代:1886

数据来源: RSC

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THE ANALYST. 73 NOTE ON THE ESTIMATION OF PAT IN MILK. By WILLIAM THOMSON, F.I.C. 1 have been engaged lately in making some analyses of milk, using Adams’ process, and one or two different modifications of it for the estimation of the fat, and I, have arrived at the following modification, which I have found to give very concordant results, and results which agree with those obtained by the method adopted by Mr. Adams, and by the modification which was suggested to me by Mr. Allen, of Sheffield, and which consists of partially enclosing an Adams’ coil in a bottom casing of flter paper, and running 5 C.C. of the milk on to the top of the coil. By this means, or by the original method of Mr. Adams, it may be obsemed, only about one half of the blotting paper is moistened with the milk.74 THE ANALYST.I have found that a strip of ordinary filter paper, 21 inches long, by 24- inches broad, will conipletely absorb the 5 C . C . of milk. I have applied the method in the following manner : - Two small pieces of ordinary stirring rod are taken, the one rather longer than the other. These are fixed together by stretching a section of india rubber tubing over each end of the rods. The two rods are separated fron each other by the fingers, and the end of the atrip of filter paper placed between them. T h e longer rod may be conveniently held by an iron clamp on a retort stand. 5 C.C. of the milk are taken in a pipette, having :a long stem under the bulb, and whilst the left hand holds the free end of the strip of paper, thus giving it an almost horizontal position, Q small portion of the milk is allowed to run from the pipette which is held in the right hand, with the finger closing the top, so as t o make a line of milk across the strip of paper within about an inch of the fixed end.More milk is then allowed to flow on to the centre of the strip, and is then spread equally all over the surface with the stem of the pipette, mhich is held almost horizontally at right angles to the strip. By this means the milk may be transferred entirely to the strip of paper, about an inch or an inch and a half at the end being left unmoistened, upon which the stem of the pipette is wiped dry. The strip of paper thus moistened with 5 c.c. of milk, may now be taken between the hands, and dried in 2 or 3 minutes over an ordinary Bunsen’s burner.The flame may be allowed to play directly on to the paper, which is moved Backwards and forwards over it ; but perhaps the most rapid manner of dealing with a number of samples of milk is to suspend the strips of paper from wire hooks, fixed in a rod of wood, mhich could then bo placed in front of an ordinary stclve or fire for a few minutes until the papers are quite dry. The strips of paper thus treated are then coiled on a stirring rod, the rod withdrawn, and the coil without any further manipula- tion placed in a Soxhlet’s tube for extracting the fat, Blotting paper treated in this manner gives practically the same result as filter paper, after the quantity of matter contained in the blotting paper itself, has been deducted from the total ether extract.If, however, blotting paper is used in this manner, only one half the length of strip recommended by Mr. Adams is necessary, but it hag two disadvantages over filter paper. The first is, that the blotting paper breaks on being coiled with the dried milk upon it, and the second is, that it is necessary to take into consideration the matter removed from it by ether. I n the modification which I suggest, the filter paper coils up easily, without any chance of breakage, and as it contains practically no matter soluble in ether, it is not necessary to make any deduction from the ether extract obtained, and as the milk is distributed equally over a larger surface than when blotting paper is used, the ether would doubtless more rapidly remove the fat €rom it.On washing a piece of paper 12 times with ether in a Soxhlet’s tube, I have obtained from a &rip of paper weighing 1-803 grm., *0006 grm. of extract, whereaa aTRE ANALYST. 75 coil of blotting paper such a8 Mr. Adams recommends and weighing 6.133 grms. gave an extract of -0149 p. It will be men therefore that the amount of extract in filter paper would fairly come within the region of experimental error, even in delicate working. following figures were obtained by taking 5 C.C. in each case which were Weight of extract obtained. by :- Adams’ coil (Allen’s modification) .. -221 6 gramme. (By my own modificationj .. .. *2126 ,, (By the modified method above described) . , -2067 ,, Strip half the leng+h used in ( n ) . . .. Strip of filter paper if we deduct the extract obtained from blotting paper in (a) experiment, viz :- 00149 gram.we obtain a fat extract of -2067 gram. On deducting one half that extract in ( 6 ) experiment (as one half of the paper was employed), we obtain a fat extract of . .. .. .. .. .. .. *2052 ,, On deducting the extract obtained from filter paper, viz., 4006 gram. (which may practically be neglected), we obtain a fat extract of . . .. . * * * .. -2061 ,, These figures shew that the results obtained from each are practically the same, and that the modification of Adams’ process wbich I have suggested, may, I believe, be performed with the least amount of trouble or care. 1 may mention further that I think it is unnecessary to wash these coils more than about half a dozen times, in a Soxhlet tube. The following results were obtained from one sample of milk, using Allen’s modification of Adams’ coil. After 4 washings the ether extract amounted to 4.52 per cent. on the milk. ?) 8 ’ J ,? 9 , 4.59 ? ? ?, ?’ 12 ,, ? ) ? 9 4.61 1 , 7 1 1 have to thank my assistant, Mr. W. L. Gadd, F.C.S., for the careful manner in which he has carried out these and the other experiments required in devising this modification.

ISSN:0003-2654    

DOI:10.1039/AN8861100073

出版商:RSC    

年代:1886

数据来源: RSC

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TRE ANALYST. 75 THE AMOUNT OP STARCH IN GROUND GINGER. BY E. W. T. JONES, F.I.C. I THINK the following analysis may be interesting to Public Analysts. It was made with a view of accurately determining the amount of starch in a sample of commercial ground ginger of about average quality, and proved genuine by careful microscopical examination. Of course, the quantity of starch may vary a little in different samples, but to no great extent in those of ordinary quality. I made this estimation, because I could not find the amount of starch in ginger stated anywhere, except in Hassall’s book where an old analyaia dated 1817, by Bucholz gives 19.76 per cent. Thia from rough experiments I knew to be quite wrong, but76 THE ANALYST. not considered so by an analyst brought against me in one of my cases, for although I had stated in answer to inquiry that ground ginger contained from 50 to 60 per cent.starch, he, in his evidence, said it contained only about 20 per cent. The magistrate and solicitors naturally seemed astonished at this discrepancy between us, and it may have been serious for the case, had I not insisted that the amount of starch natural to ginger had really no bearing on the question at issue, viz., the presence of a foreign body. For the estimation of the starch, I employed the very excellent method of Mr* O'Sullivan, F.R.S., based on the action of diastase, and the estimation of the resulting dextrin and maltose (see J. Chem. Soc., 1884.) Five grammes of the ground ginger mere purified by extraction. (i) Ether, after just moistening with alcohol.(C) AZcohoZ (sp. gr. 0.90) at 35*--38OC. (iii) Water at 35" to 38OC. Each of these solutions I evaporated, and after drying at 100aC., weighed the residues, calling them respectively, the Zdherid, AZcohoZic, and A p ~ o z c s Extract, The ginger thus purified after gelatinizing the starch I submitted to the action of 0.03 grm. of active diastase under the proper conditions, carefully proving the complete transformation of the starch, and that none was left in the residue--this residue after washing and drying at 100°C., gave me crude fibre, which after burning and deducting ash, I put in the analysis as Fik8. The moisture and ash were, of course, done in another portion of the ginger. The solution of the starch products brought to 100 C.C.at 15.5%. had a sp. gr. 1011.4, and dividing all over 1000 by 3.95, gives 2-886 grammes of solid matter in the 100 C.C. 5.0395 grms. of this solution gave 0.1775 grm. of CuO, and this multiplied by 0.7256 gives 0.1288 grm. maltose for the quantity taken, or 2.585 grms. for the 100 C.C. The optical activity with a 200 m.m. tube, and a Soleil-Ventzke-Scheibler Polaris- cope, was a deviation of +23.0 divisions. With such an instrument for the 200 m.m. tube, I gramme of maltose in 100 C.C. gives a deviation of 8.02 divisions, and 1 grm. of dextrin 11.56 divisions ; hence, 2.585 grm. of maltose found by the copper test would account for 20.74 divisions of deviation, leaving 2.27 divisions for the dextrin ; this divided by 11.56 gives 0.196 grm. of dextrine in the 100 c.c.-we now have Maltose , , .... .. . . 2.585 grms. Dextrin . . .. - a r * . . 0.196 ?, Diastase . . .. .. e . . . 0.030 ,, making 2.811 against 2-886 grms. inferred from the sp. gr. a loss of 0-075 grms. or 1.5 per cent. on the ginger taken. 2.585 grms. maltose equals 2450 grms. starch. 0.196 ,, dextrin ,, 0.196 ,, making a totalof 2.646 or 52.92 per cent. on the ginger.THE ANALYST. 77 With this explanation of my procedure, I think the analysis will be intelligible. As the fibro from the above method appeared large, I treated another 3 grammes of the ginger by the usual 5 per cent. acid and soda method for cellulose or ‘‘ indiges- tible ’’ fibre, which gave 2-66 per cent. ANALYSIS. Moisture i.e. loss on drying at IOOQC Alcoholic ,, 3.38 ,, Aqueous ,, 3.66 ,, &arch 52.92 ,, *Fibre 19.12 ,, Matter not accounted for in the starcth produuts ,) 10*10 per cent. Etherial Extract 3-58 ,, tMineral Matter (Ash) 480 ,, 1 *50 99.06 *By ordinary 5 per cent. acid and soda method 2-66 per cent. +Contained silicious matter and sand 0.35 per cent. (cellulose or ‘‘ indigestible fibre ”)

ISSN:0003-2654    

DOI:10.1039/AN8861100075

出版商:RSC    

年代:1886

数据来源: RSC

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THE ANALYST. 77 NONTHLY RECORD OF ANALYTICAL RESEARCHES INTO FOOD. DETECTION AND ESTIMATION OF FUSEL OIL.-B. R6se, Phmm G'efitrde, 1886. 9.- When chloroform is shaken with diluted gpirit, its volume is sensibly increased. The rate of increase depends OR temperature, dilution of the spirit, and proportion of chloroform, but these being always alike the results are then very constant. Chloroform has also the property of rapidly removing amylic alcohol from its solution in diluted spirit. On the other hand, the presence of amylic alcohol in chloroform increases its power to dissolve ethylic alcohol. When, therefore, chloroform is shaken with diluted ethylic alcohol containing rtmylic alcohol, there will be a very notable increase in volume, and on these principles the author has based the following process.The apparatus required is simply a tube, provided with a stopper hoIding about 180 c.c., having the lower part drawn out and graduated. The narrow graduated portion should hold about 50 c.c., and be graduated in &"- C.C. In using the apparatus, 20 C.C. of chloroform are introduced into the bottom part of the tube by means of a Iong-necked funnel, so that none shall collect on the upper aides of the tube. The spirit to be tested is either diluted with water or strengthened by suitable means until it contains exactly 50 per cent. by volume of real alcchol (sp. gr. *9346 at 60OF.) and 100 C.C. of this prepared spirit is carefully run on to the top of the chloroform. The stopper is greased with vaselim, put in tightly, and the whole tube immersed for half an hour in water a t 59.g°F.(15OC.). The tube is then violently shaken and replaced in the water for the chloroform to settle (which process is aided by occasional tapping), and after an hour the volume of the bottom layer is read off. If the spirit be pure this volume will now be 37.1 c.c., but, if it contain one per cant. by volume of amylic alcohol, tho bottom layer will measure 39.1 c.c., thus giving an increase of one C.C. for each half per cent. by volume of amylic alcohol preeent in the sample. When this process is applied to78 THE ANALYST. the ordinary ram spirits of commerce, the results are below the truth because their 6‘ fuse1 ” contains other substances besides amylic alcohol, notably, propylic and isobutylic alcohols, which have less tendency to pass into chloroform, A.M. &i. ESTIMATION OF GLYCERINE IN WINE. - I;. Medieus. - Repert. der Anal. Chern., 1886.-l.-The process given in this paper is really practically that proposed by the Berlin Committee, and has, therefore, little novelty. 100 C.C. of the wine are concen- trated at a gentle heat till only 10 C.C. are left. Two grains of sand and 3 C.C. of milk of lime (2 equivalents lime and 5 equivalents water) are now added, and the mass nearly evaporated to dryness. This is then extracted by 4 successive treatments with boiling alcohol of 96 per cent., and from the resulting solution 150 C.C. of the alcohol is recovered by distillation. The remaining fluid is evaporated to a syrupy consistence, and the syrup treated with 10 C.C. of absolnte alcohol and transferred t o a stoppered bottle with 15 C.C. of ether. After standing till quite clear, the liquid is poured into a light- tarred and stoppered weighing-bottle ; and, the ether-alcohol having been driven off by heat, the bottle and contents are kept for one hour in the water-oven, then clbsed with the stopper, cooled and weighed. I t is doubtful whether the glycerine so weighed is absolutely pure ; but the procws, as tested by the author, appears, at all events, to give constant results. A. M. M.

ISSN:0003-2654    

DOI:10.1039/AN8861100077

出版商:RSC    

年代:1886

数据来源: RSC

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78 THE ANALYST. MONTHLY RECORD O F GFENERAL RESEARGEE8 I N ANALYTICAL CHEMISTBY. THE ANALYSIS OF ASPHALT. S. Bein. Repert der Anal. Chem., 1886, 3.-The author criticises Mr. Kingzett's process originally published in THE ANALYST (vol. viii., p. 4). Owing to the rapid oxidation of oil of turpentine, the author states that it always leaves, even when freshly distilled, a resinous residue on evaporation, and thus when used to extract bitumen, the results may be too high by 6 per cent. Acting on freshly distilled turpentine by evaporating in a platinum dish the author obtained- 5 C.C. ................ *225 10 C.C. ................ *310 15 C.C. ................ -334 25 C . C . ................ '986 35 C.C. ................ 1.124 45 C.C. ................ 1.212 50 C.C. ................ 2,043 After keeping for two days, 60 C.C.gave 3.401 per cent. of resin. The author, after trying other aolventa, is therefore of opinion that the direct estimation of bitumen ia an impossibility, and he adopts one of the following indirect processes :- The remainder is ignited until the bitumen has entirely burned away, and some ammonium carbonate having been added, it is again heated gently and weighed, when the loss is taken as repre- senting bitumen. (2) The sample (about 1 gram.) is dried at 212' and loss = moisture. The dry residue is repeatedly exhausted vith oil of turpentine, and the insoluble portion is collected on EL small tared .filter, and washed with turpentine. After draining, the turpentine is in turn removed by percolating with a little absolute alcohol or ether, and the filter and contents dried at 212O and weighed. This weight, deducted from that of the dried asphalt started with, gives the bitumen, and the insoluble portion on the filter is simply mineral matter, which can be examined as usual if desired.Turpentine taken. Per cent. resin left. (1) The sample is dried at 212' and loss = moisture. 1,. DE I<.THE ANALYST. 79 ESTIMATION OF SMALL QUANTITIES OF SODIUM CHLORIDE IN PRESENCE OF LARGE AMOUNTS OF POTASSIUM CBLORIDE.-BY G. Laube. Repert. der Anal. Chem., 1866, No. 10. The method usually followed for the estimation of sodium chloride in Stass- furt salt and other minerals rich in potassium chloride, is very apt to lead to oonsider- able differences between analysts. In 1882, I?.Rijttger and H. Precht published a method based upon the relative solubility of potassium and sodium chlorides in strong alcohol of 90 per cent. by weight, and so designed as to admit, according to their contention, of the solution of the whole of the sodium chloride, with only a little of the potassium chloride, before separating the latter by platinic chloride in the usual mannor. The author, however, finds that the complete extraction of the sodium chloride by the direct trituration of 20 grams. of the sample withralcohol to be impos- sible, and the results so obtained are always too lorn. In proof of this he made experiments with a mixture containing 95*5vgrams. pare KC1, and *5 gram. pure NaCl, using, in one case, as much as 200 C.C. of alcohol for 10 grams.of the mixture, and in another case employing 300 C.C. for 20 grams. In the first case he got back *456 per cent., and in the latter only -417 per cent. NaC1. When the more usually employed modification of the process was used, viz., placing 20 grams. in a flask graduated at 110 c.c., filling up with alcohol, then adding -5 C.C. of 10 per cent. solution of potassium carbonate to remove any magnesia, and lastly, after shaking and standing, taking an aliquot part of the alcoholic liquid for analysis-the results were still worse. Using the same test mixiure, there waa only from -346 to *359 of NaCl recovered. In order to meet these difficulties, the author found it to be necessary that the sample should first be dissolved in a little water, and then this solution should be mixed with alcohol of a stronger nature according t o the amount of water first used.Thus the precipitate is really pure potassium chloride, and the whole of the sodium chloride remains in solution. The author’s modification of the process with this end in view is as follows :-lo grams. of the pulverised substance are introduced into a flask graduated at 105 C.C. and dissolved by the aid of 18 to 20 C.C. of warm water. To this alcohol of 94 to 99 per cent. is added gradually until the flask is three parts full. Two drops of solution of potassium carbonate (1.5) are then added, and the whole having been thoroughly cooled, is made up to the mark with more alcohol. After standing till the precipitate is perfectly settled, 35 to 50 C.C. are taken off by means of a pipette and evaporated to dryness in a platinum dish. This residue having been weighed, is then submitted to the usual estimation of potassium with platinic chloride. The following are some of the author’s results, working on the same mixture of the two clilorides containing *5 per cent. r e d NaC1:- Xxp. No. 1 gave -480 per cent. NaC1. ? ? 2 7 7 *492 I ) ? ? ? ? 3 ? ? ,481 7 , ?, ?? 4 7, -516 7, ? I

ISSN:0003-2654    

DOI:10.1039/AN8861100078

出版商:RSC    

年代:1886

数据来源: RSC

摘要:

THE ANALYST. 79 C0RREXPON.DENC-E. {The Editor is not in any way responsible for opinions expressed by his Correspondents,] To the Edztov of THE ANALYST. MR. W. JOHNSTONE ON MILK ANALYSIS. SIR.-I am exceedingly sorry to have been the means of causing so much wrath and lamentation in Birmingham and Billiter Square. However, I can thoroughly understand your correspondents taking up the cudgels on behalf of that most unfortunate Milk Commttee, more especially as they seem to be thoroughly aware of their shortcomings. Why my critics should have poured out their vials of wrath upon me, I am a t a loss to comprehend, as my paper was written weeks, nay months, before the Milk Committee gave in their report, and wap in no way intended as a criticism on theh work. They also find fault with me for publishing no comparative results ; that I give no intelligible experi- ments as to solids-not-fat, or as to fat estimations.For those I refer them to TEE AXALYBT, vol. x.,60 THE ANALYST. 84, but in the meantime what results have the Milk Committee published after two years’ work? Got one figure. The process and apparatus I had the honour to describe before the Society some time ago, is a process which I maintain leaves nothing to be desired, and is simplicity itself; in fact, so simple and so aoourate that not one single member of the Committee have attempted to attack it, except upon theoretical grounds, a procedure so irrational, 80 thoroughly unprofessional, that it is monstrous for scientifio men to adopt such a line of attack, when a little practical work would have settled the ques- tion.Dr. B. Hill states he has found no benefit from the use of acetic acid. It is unfortunate he did not go a little further, and inform ns if he has found any harm from its use. My reasons for refusing the Milk Committee’s process me based solely upon practical grounds, and not upon any personal animosity, so I am exceedingly sorry that my critics should have fill.5d their letters with acrimonious assertions, as I can assure them that their whispered rumours must be the results of an imaginative organ, as I am heartily glad that I had not a finger in such a warm pie, the crust of which appears to have been composed of rampant petty jealousies. I deoline to follow my oritics in detail, as they have aompletely failed in their saroastic verbosity to discount my prooess, however I thoroughly agree with Dr.B. Hill when be states “that Mr. Johnstone is the inventor of a process, in fact the onZy process, for the correct analysis of milk.” It is far from my intention to make myself appear antagonistic to the Committee, or to have my name in any way connected with their hybrid process, a8 I am perfectly satisfied with my own, and the Com- mittee are oertainly welcome to theirs. In conclusion, I cannot but express my opinion that the work of my critics, whioh began with florid assurance, has unfortunately degenerated into ludicrous absurdity, and ia without a parallel in the annals of a scientific investigation. Faithfully yours, WILLIAX JOHNSTONE. THE ESTIMATION OF GLYCERINE IN FATS.To the Editor of THE ANALYBT. SrR,-Since the appearanoe of ‘the last number of the ANALYST, containing my paper on the determination of glycerine produced by the saponification of oils, Mr. William Fox has called my attention to a point which requires explanation. In the note in question, I laid stress on the fact that the weighing of the calcium oxalate precipitate gave inaccurate results, in consequence of the unavoid- able contamination of the precipitate by more or less sulphates, silioa, and other impurities, and I mentioned the employment of the well-known proceso of titrating the precipitate of oaloium oxalate by a standard solution of potassiuu permanganate, as recommended by Benedikt andzeigmondy, as having effectually solved the difficulty. Mr. Fox informs me that he had been in the habit of employing this method of treating the ealoium oxalate precipitate before the appearance of Benedikt and Zsigmondy’s paper, but that he had not felt oalled on to state that to me when I drew his attention to the improve- ment they had made on the method which I understood him to be using up t o that time. Of course such credit as is due to the improvement of the prooess, originally described by Mr. Fox, must be given to those who f i s t made the improved method public, but it, is only just to Messrs. Fox and Wanklyn that it should be known that they had previously employed the same plan, as otherwiw their adoption of themethod in their note published in the Chemical News in January last, would have required explanation. I am, sir, yours truly, ALFRED H. ALLEN. Sheffield, March 18th, 1886.

ISSN:0003-2654    

DOI:10.1039/AN8861100079

出版商:RSC    

年代:1886

数据来源: RSC

摘要:

60 THE ANALYST. NOTICES TO CORRESPONDENTS. Ur. Newton (U3.A.)-A specimen coil for Adams’ method as modified by Allen has been posted t o your address. H. M. Wiley, (U.S.A.)-Your letter received at very moment of going to press, and will be referred to Xr. H. for reply.-Subject long sinoe thrashed out and given up over here, as butter varies greatly in this respect by age and temperature especially in summer. See proceedings of Society of Public Analysts, vol. I. 1876, pp. 188-6. ALL Communications to be addressed to 325, Kennington Road, London, S.E. BOOKS, &c., RECEIVED. REPORT on Quality of Milk as produced in Massachusetts; A Short Manual of Chemistry, by Drs. Dupr6 and Hoke ; Workshop Receipts for Manufacturers, &c., by 0. (3. W. Lock ; The Pocket Phitrmacopceia for 1835, by Armand Semple ; American Analyst ; American Chemical Review ; Amerioan Druggist ; American Grocer ; American Journal of Pharmacy ; Brewer’s Guardian ; British and Colonial Druggist ; Canadian Pharmaceutical Journal ; Chemist and Druggist ; Country Brewer’s Gazette ; Illustrated Science Monthly ; Independent Journal ; Invention ; Journal of the Society of Chemical Industry ; Le I’douvement Hygienique ; Medical Press ; Medical Record ; The Miller ; Monthly Magazine of Pharmacy and Chemistry ; Pharmaceutical Journal ; Pharmaceutical Record ; The Polyclinic ; Popular Science News ; Reportorium der Analgtisohen Chemie ; San Fran- cisco NewsLetter ; Science ; Scientific American; Society of Arts Journal; Hospital Gazette.

ISSN:0003-2654    

DOI:10.1039/AN8861100080

出版商:RSC    

年代:1886

数据来源: RSC