摘要:

THE ANALYST. JANUARY, 1591. ON THE COMPOSITION OF BUTTER. BY DR. I?. VIETH. Read at 1”eeting, December, 1890. WHEN speaking about the analysis of butter, we are, a t the present time, very much snclined to think exclusively of ascertaining whether the chief component part of butter, i.e. the fat, consists of the pure fat derived from cow’s milk. No doubt, the admixture of foreign fat to butter is a widely practised and very serious oirence, and the detection of sucb adulteration, with a view to put a stop to it, is a matter of the great& import- ance. But over this prominent question we must not forget that there are other ways in which the purchaser and consumer of butter may be wronged. The remarks which I have to offer have some reference to the latter, and do not touch the former question of adulteration with foreign fats.My observations, moreover, are not addressed to the public analyst in particular, but to the analytical chemist in general.2 TEE ANALYST. We all are well aware of the difficulties t,o fix standards or limits of purity for natural products, such, for instance, as milk ; but these difficulties also exist with regard to manufactured articles, those derived from milk, notably, cream- if the term “ manu- factured article ” is allowed to be used-and butter, forming striking examples. When milk or cream is subjected to continuous dashing, the fat globules coalesce in consequence, it is assumed, of the fat constituting the globules, passing from the liquid into the solid state. After churning has gone on for a time, conglomerates of fat make their appearance and grow larger by continued dashing.The fatty mass thus obtained and removed from the liquid in which it floats--the buttermilk-is raw butter. In order to make of the raw product the article of trade it is necessary to remove part of the buttermilk enclosed in the raw butter, which is done by kneading the latter. The further treatment which butter receives differs with the habits of the various producing countries and the tastes of the consumers for which the finished product is intended. Thue, while in some countries kneading alone is resorted to as a means for the removal of the excess of buttermilk, in others this removal is done more effectually by washing the butter with water or brine. Again, certain kinds of butter, more particularly those made from sweet cream and intended for immediate consumption, contain no salt, or very trifling quantities of it, whiIe others, those made from sour milk or cream and meant to be kept for some time without exception, have salt added, frequently in con- siderable quantities.Salt is added to butter, not only to meet the taste of certain classes of consumers, but also as a preserving agent. Judging from the experience of others, as well as from my own, I am inclined to believe that the habit of adding other preservatives, notably those containing boracic acid, to butter is becoming very general in certain places, One more extraneous matter frequently, perhaps one might say invariably, present in butter of commerce is some colouring agent.No doubt the colouring of butter origin- ally arose out of a desire to give to all butter, which under certain circumstances is nearly as white as tallow, that rich yellow colour which fresh grass-butter is known to present, B kind which has the renown of being of especially delicate flavour. Nowadays, however, no one, when putting colouring to the milk or cream before churning, thinks of making appear like grass-butter the white-looking product of the milk of his stall-fed corns. The reason why butter is coloured is simply this : the trade demands an article which from one end of the year to the other should be as uniform as possible in every respect, and uniformity of coiour is one of the first qualities expected. Butter-colouring is made exclusively of cake annatto, a harmless and clean preparation of the fruit of Bixa orellana, which has nothing to do with the nasty soft annatto preparation of by-gone times.The quantity of colouring used being extremoly small, and its nature perfectly innocuous, there can ecarcely be any reason to object to a practice which is nothing hut a concession to the trade. The great importance which the butter trade has attained may be gathered from the fact that last year’s import of butter into this country amounted to 1,927,469 cwts., worth .€10,243,728, whilst the export was not quite 25,000 cwts. I am not aware of the existence of any statistics which would allow to state what the home-production amounts to ; it must, however, be very considerable. 1 have mentioned that butter is frequently washed, in order to free it as much asTHE ANALYST.3 ~- possible from buttermilk; the complete removal of the latter, if intended, is certainly not achieved in practice. The kneading of the butter also does not rid it of all the buttermilk, or the water used for washing out the latter, as the case may be, and, in- deed, a product consisting entirely of butter-fat and containing no water would not be butter at all. On the other hand, the presence of an undue amount of butter-milk or water is not only highly undesirable, but may even be looked a t as a fraud. The question then arises in what proportion the various constituents should be present, and in the absence of any other guidance, I believe this question of standards and limits with regard to butter can only be satisfactorily decided by referring to the usual composition of butter as it appears in the market.The 267 analyses of butter samples which 1 have made in the course of the last few years might, perhaps, form a contribution to the solution of the question. The way in which I proceed in analysing butter is described in a few words :-Into a conical flask of about four ounces capacity 4 or 5 grams. of butter are introduced. The flask is put in a drying oven, the temperature of which is kept at 100' C., and the evaporation of the water facilitated by giving the melted butter a circular motion every half-hour. After the loss in weight has been ascertained, the Fat is completely washed out with ether, and the insoluble part dried and weighed.I n a watery extract of the We have then determined water, fat, solids- not-fat and sodium chloride contained in the latter and calculated from the chlorine. The difference between the quantities of solids-not-fat and sodium chloride is made up by the small amount of the non-fatty solids of milk retained 6, the butter, and may, for convenience sake, here be termed '' curd, etc " I n case the butter should contain extraneous admixtures other than salt-for instance preservatives, so far as they are not soluble in ether-these would, of course, swell the last-named item. Turning now to the results of my analyses, I do not propose to harrass you with all the figures relating to the 267 ~amples forming the basis of my observations, but will confine myself to giving maxima, minima, and averages for the various kinds of butters : - fatty solids the chlorine is titrated.Description of Butter. Eagliah, fresh and salt . . French, fresh French, salt . . Kid, salt . . Danish, salt . . Swedish, salt. , Number of Samples. k n 1L 108 5 40 17 25 Fat. 82 97-fJG.49 136.85 82'83-86.61 84.77 84.34 85.24 83.41 S2.89 82.30-86.25 8 2.00-8 9 -4 5 78.85-87.57 78.91-85.64 - Water. 7.85- 14:3g 11.54 11.63-15.57 13.76 11.1 5 - 4 3.59 12.05 8*39--15*33 12.24 9.58-1'7.25 13.42 11-$8-16*96 13.T6 Card, etc. ___- .- . A n 1 .r,Z - U A - l . i l J -5 9 -46 -2 $1 7 1.38 1.26 -1.85 1-60 -80-2 '8 2 1-17 -94-2.39 1-30 *77-2*01 1-32 Salt.4 THE ANALYST. Percentage of Water, 7- 8 8-- 9 9-10 10-11 11-12 12-13 13-14 14-15 15-16 16-17 17-18 With regard to the fat, I may say at once that I am of opinion that in a well- made butter it should not fall below 80 per cent.Among my samples there were three only in which the percentage of fat was below 80, viz., one sample of Danish butter with 78.05, and two samples of Swedish butter with 79.69 and ‘78,91 per cent. respec- tively. The extreme in the other direction was shown by a sample of English butter which contained 90.49 per cent. of fat. An undue percentage of this should be objected to, if not for others, certainly for this reason, that it reduces below its proper limit the percentage of fat, which latter after all is what we chiefly want to buy in butter. On the other hand the reduction of the water below a certain limit can be effected only by ‘ I over-working ” the butter, a process which very injuriously affects the appearance and taste, and thereby the commercial value of the product.Moreover, in the case of salt butter a certain amount of water is required to dissolve the salt which has been incorporated into the butter, and keep it in solution. We have nexh to consider the quantity of water. The results of my examinations were as follows :- Number of Samples. a 6 6 16 39 46 103 38 10 1 1 I I 267 Per cent. 100~0 +4 3 *2 2.2 6.0 14.6 17.2 38.6 14-2 3.8 -4 *4THE ANALYST. 5 Milk contains for every 100 parts of water about 10 parts of solids free of fat. The same relation between the two items must exist iqbuttermilk and also in butter, provided the latter was made from sweet or slightly sour milk or cream and freed from the excess of buttermilk by kneading.If the butter, as is the fashion in some countries, is rinsed with water when taken from the churn, the relation referred to will be some- what effected, and, still more it will be disturbed if the butter is thoroughly washed with water or brine. The influences mentioned will, I need hardly say, reduce the relative quantity of On the other hand, the relative quantity will be in- creased if butter is made from strongly acid material in which the casein had been not curd, etc.” coagulated in soft, and are retained by For every 100 but precipitated in hard masses, which partially become enclosed in the butter. parts of water, there were present, PARTS OF u CUED, ETC.,” I n English butter, min. 0, max. 13, average 5 ,, Kiel ,, ?, 8, 9 , 23, 9 , 10 9 , Danish 9 , ?, $7 ,, 14, 9 9 10 ), Swedish ,, ,, 7, 1, 16, 9 9 10 We may consider, then, the Kiel, Danish, and Swedish butters not, or very slightly washed-rinsed-and the English butters, in the majority of cases, very tho- roughly washed.As an instance of a butter made of strongly acid material, I may men- tion a sample of Kiel butter in which the relation between water and “ curd, etc.” was 100 to 23 ; this butter had a decidedly ‘( cheesy ” taste. The quantity of salt was very small in all the samples of fresh French butter, there being generally less than 01 per cent. present, proving that no salt had been in- corporated into the butter. The same was the case with a number of the samples 0 English butter, others of the same class containing a few tenths of a per cent.of salt, pointing to washing with brine. Far the majority of samples of salt butter contained from 1 to 2 per cent. salt, a small number between 2 and 3 per cent., and one sample of Danish butter just above 3 per cent. I may mention that when salt is added to raw butter, about half its quantity only is retained by the butter, while the other half is lost in the buttermilk which is worked out. I n conclusion, I will apologise for having entered rather much into practical de- tails which may perhaps be considered as in no way concerning the members of this SQ&Q; My excuse is? that I am of opinion that some knowledge of practical details ig very frequently highly desirable for the chemical expert. DISWSSION. Mr. ALLEN said they mere greatly indebted to Dr.Vieth for the valuable statistics he had laid before them. Hitherto the most extensive published series of determinations of salt and water in butter were those contained in the report of the Board of Inland Revenue, dated May 31st, 1876, describing the results of the analysis of 117 samples o t butter collected in various parts of the kingdom. In these samples Dr. James Bell found proportions of water ranging from 4.15 to 20.75 per cent., the mean of the wholo being 14.20 per cent. One of the above so-called ‘‘ genuine ” samples contained 15.08 per cent. of salt, the next highest quantities being 9.20, 8.56, 8.38, 8-28) and 7-71 per cent. I n one sample there was 4.02 per cent. of curd in addition to 19.12 per cent. of water.I n the same report Dr. Bell stated that ‘I the samples may be taken as fairly6 THE ANALYST. representing the various qualities of butter as made and brought to market by farmers both in England and Ireland. Every care was exercised by the Board’s local officers in procuring them, and there can be no question whatever aa to their being genuine.” From this conclusion it is evident that in Dr. Bell’s opinion no farmer purposely leaves excess of water in his butter, and if any dairy-maid, through laziness or incompetency, produce a butter containing an excessive proportion of water, the percentage of water thereafter allowable in butter is to be increased accordingly. This line of argument would be laughable if, as a matter of fact, it had not had the lamentable effect OE raising the legal allowable proportion of water to 21 per cent.He (Mr. Allen) had met with a still larger proportion of water in butter sent for analysis under the Sale of Food Act, and conviction had occurred on his certificate for 23 per cent. He should regard 16 per cent. as the maximum proportion of water in good, well-made butter. Any excess above this proportion became evident in the course of the analysis, and it was only in such cases that it became necessary to ascertain the amount exactly. Dr. Vieth had pointed out that a good deal of the salt added to butter was eliminated in the subsequent treatment. I n the North of England the public gave preference to butter containing considerably more salt than met the London taste. Mr. CASSAL said that an important question had been raised with regard to the definitions of composition which should be applied to articles of food, such as butter.I t led him to suggest that the Council should consider whether it would not be advisable for the Society to lay down such definitions as were required. It was easy to see the difficulty in which public analysts were placed, in the present state of the law, by such circumstances as the one which had been mentioned-that a dairymaid in Ireland should manufacture an abnormal butter, and thereby endeavour to create an exception to the definirions which had been adopted by public analysts. If the Somerset House chemists based their limits upon the results of analysis of abnormal samples of this kind, it would be greatly to the detriment of the public and of the public analyst; but he did not think that this was the case.The best definition which the promotors of the Mar- garine Act were apparently able to hit upon was, that “ ‘ butter ’ was to be the article usually known as ‘ butter.’ ” As a matter of fact, public analysts were acting upon defini- tions which they had themselves made, and which were based upon such work as that of Dr. Vieth, whose results were, as all would admit, of the greatest value and importance. It would be highly satisfactory if, a t the instance of the Society, both public analysts and private analysts throughout the country could be induced to adopt, uniformly and fairly, wide and sensible definitions as might commend themselves for acceptance after careful consideration.Mr. HEHNER wished t o remind Mr. Cassal that the Society of Public Analysts, within a year or two of the commencement of its existence, laid down a limit that butter should contain not less than 80 per cent. of butter fat, a figure that had been fully confirmed by subsequent results. Mr. ADAMS said that Dr. Vieth had given them some usefiil statistics, and, coming from him, they were all the more valuable to himself not being a public analyst, and therefore looking at the matter from a broad, commercial, and perfectly independent point of view. The speaker’s own view of the case was that it was quite as much the duty of the public analyst to keep the watering of butter within just limits as that of the reduction of spirits, whiskey, gin, etc., by unfair dilution. Mr. FABER said there had been cases in police courts where dealers had been con- victed of selling butter containing an undue amount of water. Dr. VrETH, in reply, said that with regard to limits being fixed for butter, he quite agreed that this was desirable, and, as he had said, he put his figures before them inTHE ANALYST. 7 - the hope they might be of some use in this respect. At the same time he must say that this was one of those points upon which they should feel their way very carefully. While of opinion that 80 per. cent. ought to be the lowest limit for.fat, he would not think it right that a butter containing 80 per cent. of fat should contain 20 per cent. of water, the water in this case would certainly be in excess. Two only of his aampleB contained above 16 per cent., and that he thought ought to be the highest limit. Mr. Allen had mentioned that he did not think it necessary to determine the quantity of water in every case, because the sample showed it at once, but that was very deceptive. Some butters look as if they contained no water at all, and still there wag a very appreciable quantity present. There might be as much as 25 per cent. of water present in a butter, and it was not at all certain that the butter would have a suepicious appearance. (Conclusion, of the Society’s Proceedings.)

ISSN:0003-2654    

DOI:10.1039/AN891160001c

出版商:RSC    

年代:1891

数据来源: RSC

摘要:

THE ANALYST. 7 A METHOD FOR THE ESTIMATION OF ALBUMEN IN URINE. BY T. C. VAN NuYS AND R. E. LYONS. (Concluded .) Urine 11. (1). 10 C.C. normal filtered urine, 10 C.C. water. (a), 5 C.C. of the diluted urine required 35.0 C.C. + normal KOH. (6). 5 C.C. of the diluted urine required 34.95 C.C. 5 normal KOH, average 34.975 c.c., corresponding to 1.6828 gram. nitrogen in 100 C.C. of the undiluted urine. (2). 10 c.c, filtered urine, 5 C.C. albumen solution, 5 C.C. Almh’s solution mixed well in a small flask and filtered. (a). 5 C.C. of the filtrate required 34.9 C.C. + normal KOH. (b). 5 C.C. of the filtrate required 35.0 C.C. Q normal KOH, average 34.95 c.c., cor- responding to 1.6856 gram. nitrogen in 100 C.C. undiluted urine ; and by deducting the weight of the nitrogen of bodies not albuminous in the solution, 0.0014, there remains 1.6842 gram.nitrogen in 100 C.C. of the undiluted urine. By the resultsobtained there was found 0.0014 gram. more nitrogen in 100 C.C. of the undiluted urine after the separation of the albumen than there was in the same volume of undiluted urine before the addition of albumen. THIRD ALBUMEN SOLUTION. Estimation oJ Albumen. (1). 10 C.C. albumen solution, 10 C.C. water. (a). 5 C.C. of the diluted solution required 44.4 C.C. +- normal KOH. (b). 5 C.C. of the diluted solution required 44.35 C.C. Q normal EOH, average (2). 10 C.C. undiluted albumen solution, 10 C.C. Almh’s solution, mixed well and The filtrate was free of nitrogen. 0.63 gram. nitrogen corresponds to 4.0131 grams. albumen in 100 C.C. of the 44.375 c.c., corresponding to 0.63 gram.nitrogen in 100 C.C. of the undiluted solution. filtered. solution. Urine. (1). 10 C.C. filtered normal urine, 10 C.C. water. (a). 5 C.C. of the diluted urine, 38.7 C.C. 4 normal KOH. (b). 5 C.C. of the diluted urine, 38.8 C.C. + normal KOH.8 THE ANALYST. (c). 5 C.C. of the diluted urine, 38.75 C.C. normal KOH, average 38.15 c.c., cor- (2). 10 C.C. normal filtered urine, 5 C.C. albumen solution, 5 C.C. Almh’s solution, (a). 5 C.C. of the filtrate required 38% C.C. Q normal KOR. (b). 5 C.C. of the filtrate required 38% C.C. & normal KOH, corresponding to 1.2544 gram. nitrogen in 100 C.C. of the undiluted urine, or 0.0056 gram, nitrogen less than in 100 C.C. of the urine before the separation of albumen. FOURTH ALBUMEN SOLUTION. Estimation of A Zbihmen.responding to 1.26 gram. nitrogen in 100 C.C. of the undiluted urine. mixed well and filtered. (1). 10 c,c. albumen solution, 10 C.C. water. (a). 5 C.C. of the solution required 48.9 C.C. 5 normal KOH. (b). 5 C.C. of the solution required 49.0 C.C. (2). 10 C.C. albumen solution, 10 C.C. Almh’s solution, mixed well and filtered. The filtrate was free of nitrogen. normal KOH, average 48.95 c,c. cor- responding t o 0-0588 gram, nitrogen in 100 C.C. of the undiluted solution. 0.0588 gram. nitrogen corresponds to 0.3745 gram. albumen in 100 C.C. of the undiluted solution. (1). 5 C.C. normal filtered urine, 25 C.C. water. (a). 5 C.C. of the diluted urine required 47.65 C.C. + normal KOH. (b). 5 C.C. of the diluted urine required 47.7 C.C.$ normal KOH, average 47.675 (2). 5 C.C. urine, 20 C.C. albumen solution, 5 C.C. Almbn’s solution, mixed and filtered. (a). 5 C.C. of the filtrate required 47.7 C.C. 5 normal KOH. (b). 5 c.c, of the filtrate required 47.7 C.C. p normal KOH, corresponding to 0,7728. gram. nitrogen in 100 C.C. of the undiluted urine, therefore 0.0084 gram. of nitrogen legs than in 100 C.C. of the urine before the separation of albumen. FIFTH ALBUMEN SOLUTION. Estimation of Albu.mea. Urine. C.C. corresponding to 0.7812 gram. nitrogen in 100 C.C. of the undiluted urine. (1). 10 C.C. albumen solution, 10 C.C. water. (a). 5 c.c, of the solution required 49.55 C.C. + normal KOH. (b). 5 C.C. of the solution required 49.6 C.C. + normal KOH, average 49.57 c.c., (2). 10 C.C. albumen solution, 5 C.C.AlmOn’s solution, 5 C.C. water, mixed and filtered. The filtrate was free of nitrogen. corresponding to 0.04816 gram, nitrogen in 100 C.C. of the undiluted solution. 0*04816 gram. nitrogen corresponds to 0.3067 Urine, gram. albumen in 100 C.C. of the undiluted solution. (1). 10 C.C. normal filtered urine, 10 C.C. water. (a). 5 C.C. of the diluted urine required 32.5 C.C. (6). 5 c.c, of the diluted urine required 32.45 C.C. + normal KOH, average 32.47 (2). 15 C.C. urine, 9 C.C. albumen solution, 6 C.C. Almbn’s solution, mixed and filtered. (a). 5 C.C. of the filtrate required 32.5 C.C. 5 normal KOH. (b). 5 C.C. of the fitrate required 32.5 C.C. 4 normal KOH, corresponding to 1.96 normal KOH. c.c., corresponding t o 1.9633 gram. nitrogen in 100 C.C.of the undiluted urine.THE ANALYST. 9 gram, nitrogen in 100 C.C. undiluted urine, Therefore fhere was found 0.0033 gram. nitrogen less in 100 C.C. of the urine after the addition and removal of the albumen, SIXTH ALBUMEN SOLUTION. Estimation of Albumen. 1.9633 - 1.96 == OP0033. (1). 10 c,c, albumen solution, 10 C.C. water. (a). 6 C.C. of the diluted solution required 48.0 C.C. 3 normal KOH. (b). 5 C.C. of the diluted solution required 48.05 C.C. 3 normal KOH, average 481025 c.c,, corresponding to 04212 gram, nitrogen in 100 C.C. of the undiluted solution. (2). 10 C.C. albumen solution, 10 C.C. Almdn’s solution, mixed aud filtered. The filtrate was free of nitrogen. 0.2212 gram. nitrogen corresponds t o 1.4090 gram, albumen in 100 C.C. of the solution, 012212 x 6137 z 1.4090.Urine 1; (1). 20 C.C. normal filtered urine, 20 C.C. water. (a). 5 C.C. of the diluted urine required 38.1 C.C. 6 normal KOH. (a). 5 C.C. of the diluted urine required 38.05 C.C. + normal KOH, average 38.07 (2). 20 C.G. urine, 10 C.C. albumen solution, 10 C.C. AlmBn’s solution, mixed and filtered. (a). 5 cc. of the filtrate required 38.1 C.C. + normal KOH. (a>, 5 C.C. of the filtrate required 38.15 C.C. +. normal KOH, average 38.125 c.c., corresponding to 1.33 gram. nitrogen in 100 C.C. of the undiluted urine. Therefore there was found 0,0061 gram. nitrogen less in 100 c,c. of the urine after the additiou and removal of the albumen, 1.3361 - 1.33 = 0*0061, Urine 11. c.c,, corresponding to 1.3361 gram. nitrogen in 100 C.C. of the undiluted urine.(1). 20 C.C. normal filtered urine, 20 C.C. water. (a). 5 C.C. of the diluted urine required 40.45 C.C. Q normal KOH. (a). 5 C.C. of the diluted urine required 40.4 C.C. + normal KOH, average 40425 (2), 20 C.C. urine, 10 c.c* albumen solution, 10 C.C. Almh’s solution, mixed and filtered. (a), 5 C.C. of the filtrate required 40.4 C.C. + normal KOH. (a), 5 C.C. of the filtrate required 40.5 C.C. 6 normal KOH, average 40.45 c.c., cor- responding to 1.0696 gram. nitrogen in 100 C.C. of the undiluted urine. Therefore there was found 0*0028 gram. nitrogen less in 100 C.C. of the undiluted urine after the addition and removal of the albumen, 1.0724 - 1.0696 = 0.0028. c.c., corresponding to 1.0724 gram. nitrogen in 100 C.C. of the undiluted urine. Albumen Solution.I I1 I1 111 IV V VI VI SUMMARY OF RESULTS. Variation in quantity of Nitrogen in grams. in 100 C.G. of the Undiluted Urine Grams. Albumen. Total grams. before introduction of of the SoIution. of the Urine. the Urine. its removal. 0.9096 15904 1 to 2 + 0*0007 1.4268 1.4196 1 to 2 + 0.0042 1.4268 1.6828 1 t o 2 + 0.0014 4.0131 1.2600 1 to 2 -0.0056 in 100 C.C. Nitrogen in 100 C.C. Dilution of Albumen and after 0.3745 0.781 2 1 to 6 -0.0084 0.3607 1.9633 1 to 2 -0.003 3 1-4090 1.3360 1 to 2 -0.0061 1.4090 1.0724 1 t o 3 -0.002810 THE ANALYST. I n case the urine is diluted to a greater degree than 1 to 2, the limit of error in the estimated quantity of nitrogen increases as the quantity of nitrogen decreases by the dilution. This is understood from the fact that with 5 C.C.urine, 0.1 C.C. of the Q normal KOH corresponds to 0.0056 gram. nitrogen in 100 C.C. of the urine ; and if the urine be diluted from 1 to 2 or 1 to 4, 0.1 C.C. + normal KOH corresponds to 0.012 and 0.0224 gram. nitrogen respectively. To determine if uric acid or other nitrogenous compound in normal, acid, or neutral urine, separates by contact with tannic acid, as in AlmBn’s solution, in different periods of time, the following estimations were made :- NORMAL URINE I. Estimation of ATitrogen. (1). 10 C.C. of filtered urine, 10 C.C. water. (a). 5 C.C. of the diluted urine required 47.25 C.C. + normal KOH. (6). 5 C.C. of the diluted urine required 47.3 C.C. Q normal KOH, average 47.275 (2). 10 C.C. filtered urine, 10 C.C. Almh’s solution, mixed well in a small flask, let (a).5 C.C. of the filtrate required 47*3 C.C. + normal KOH. (6). 5 C.C. of the filtrate required 47.25 C.C. + normal KOH, average 47.275 c.c., (3). 10 C.C. filtered urine, 10 C.C. Almbn’s solution, mixed well in a small flask, let (a). 5 C.C. of the filtrate required 47.2 C.C. + normal KOH. (6). 5 C.C. of the filtrate required 47.2 C.C. & normal KOH, corresponding to (4). 10 C.C. filtered urine, 10 C.C. AlmBn’s solution, mixed well in a flask, let stand c.c , corresponding to 0.3052 gram. nitrogen in 100 C.C. of the undiluted urine. stand 15 minutes and filtered. corresponding to 0*3053 gram. nitrogen in 100 C.C. of the undiluted urine. stand 45 minutes and filtered. 0.3136 gram. nitrogen in 100 C.C. of the undiluted urine. 60 minutes and filtered.(a). 5 C.C. of the filtrate required 47-25 C.C. + normal KOH. (b). 5 C.C. of the filtrate required 47-3 C.C. 6 normal KOH, average 47.275 c.c., corresponding to 0.3052 gram. nitrogen in 100 C.C. oE the undiluted urine. From the results of these estimations it seems that no nitrogen compound was separated from the urine by contact with the tannic acid solution, even when the time was extended to one hour, but the urine in this case contained a minimum quantity of nitrogen, and it may be inferred that the urine contained a minimum quantity of uric acid. NORMAL URINE IT. Estimation of Nitrogen. Urine was highly coloured, acid in reaction, sp. gr. 1.031 (I). 10 C.C. filtered urine, 10 C.C. water. (a). 5 C.C. of the diluted urine required 31.95 C.C. 6 normal KOH.(b). 5 C.C. of the diluted urine required 31.9 C.C. Q normal KOH, average 31.925 (2). 10 c.c; urine, 10 C.C. AlmBn’s solution, mixed well in a flask, let stand 20 ex., corresponding to 2.0244 grams. nitrogen in 100 C.C. of the undiluted urine. minutes and filtered.THE ANALYST. 11 (a). 5 C.C. of the filtrate required 31.8 C.C. + normal KOH, corresponding to 2.0384 (3). 10 C.C. urine, 10 C.C. Almh’s solution, mixed well in a flask, let stand 45 (a). 5 C.C. of the filtrate required 32.0 C.C. normal KOH, corresponding to 2.016 (4). 10 C.C. urine, 10 C.C. Almen’s solution, mixed well in a flask, let stand 60 (a). 5 C.C. of the filtrate required 32.1 C.C. g normal KOH. (6). 5 C.C. of the filtrate required 32.1 C.C. $ normal KOH, corresponding t o 2-0048 grams. nitrogen in 100 C.C.of the undiluted urine. The increased quantity of nitrogen found in the urine after having stood with the tannic acid 30 minutes was due either to absorption of ammonia from the air of the laboratory or to an error in the titrations, probably from the latter, as but one estima- tion was made. By contact with tannic acid 45 and 60 minutes, the losses of nitrogen were 0*0084 and 0.0196 gram. respectively. As 0.075 C.C. of the normal KOH corresponds to 0.0084 gram. nitrogen when the dilution is 1 to 3, there is no evidence that any nitrogen compound, uric acid, was separated by the contact, but that there was a loss of nitrogen by the urine remaining in contact with tannic acid 60 minutes is probable. In order to subject urine containing an abnormal quantity of uric acid, pure urate of potassium was dissolved in normal urine, neutral in reaction; solution having taken place, the urine was filtered and the uric acid in the filtrate estimated.The quantity of uric acid in 100 C.C. urine was 0.3575 gram,, corresponding to about 6 grams. uric acid eliminated in 24 hours. Estimation of Nitrogen. (1). 10 C.C. of the filtered urine containing the potassium urate, 10 C.C. water. (a). 5 C.C. of the diluted urine required 32.2 C.C. & normal KOH. (b). 5 C.C. OF the diluted urine required 32.2 C.C. & normal ROB, corresponding to (2). 10 C.C. filtered urine, 10 C.C. Almen’s solution, mixed well in a small flask, let (a). 5 C.C. of the filtrate required 32.4 C.C. (6). 5 C.C. of the filtrate required 32.45 C.C.+ normal KOH, average 32.425 c.c., corresponding to 1.9684 gram. nitrogen in 100 e.c. of the undiluted urine. The results of the estimations indicate the separation of 0.0117 gram. nitrogen in 100 C.C. of the urine by contact with the tannic acid. Albumen was next estimated by this method, and also in the same urine by the gravi- metric method. grams. nitrogen in 100 C.C. of the undiluted urine. minutes and filtered. grams. nitrogen i n 100 C.C. of the undiluted urine. minutes and filtered. 1.9801 gram. nitrogen in 100 C.C. of the undiluted urine. stand 20 minutes and filtered. normal KOH. ALBUMINOUS URINE I. (1). 30 C.C. filtered urine, 10 C.C. water. (a). 5 C.C. of the diluted urine required 40.3 C.C. i- normal KOH. (b). 5 C.C. of the diluted urine required 40.35 C.C.normal KOH.12 THE ANALYST. (c). 5 C.C. of the diluted urine required 40.25 C.C. corresponding to Q.72426 gram. nitrogen in 100 C.C. undiluted urine. (2). 30 C.C. filtered urine, 10 C.C. Almkn’s solution, mixed well and filtered. (a). 5 C.C. of the filtrate required 41-1 C.C. Q normal KOH. (b). 5 C.C. of the filtrate required 41.2 C.C. 6 normal KOH. ( c ) . 5 C.C. of the filtrate required 41.15 C.C. 3 normal KOH, average 41-15 c.c., cor- responding t o 0.6608 gram. nitrogen in 100 C.C. of the undiluted urine. The difference in the quantities of nitrogen estimated in 1 and 2 is 0.06346 gram., corresponding to 0.40424 gram. albumen in 100 C.C. urine. The Gravimetric Xethod. hence the difference in the results of both methods is 0.0357 gram.albumen in 100 C.C. ALBUMINOUS URINE 11. normal KOH, average 40.3 C.C. The average of three estimations of albumen in 100 C.C. of the urine was 0.4399 gram., (1). 10 C.C. filtered urine, 10 C.C. water. (a). 5 C.C. of the diluted urine required 40.9 C.C. 3 normal KOH. (6). 5 C.C. of the diluted urine required 40.9 C.C. normal KOH, corresponding to 1.0192 gram. nitrogen in 100 C.C. of the undiluted urine. (2). 10 C.C. filtered urine, 10 C.C. Almen’s solution, mixed well in a flask and filtered. (a). 5 C.C. of the filtrate required 40.95 C.C. 6 normal KOH. (6) 5 C.C. of the filtrate required 41.0 C.C. normal KOH, average 40.97 c.c., cor- responding to 1.01136 gram. nitrogen in 100 C.C. of the undiluted urine. The difference in the quantities of nitrogen in 100 C.C.of the urine before and after the separation of albumen is 0.00784 gram., corresponding to 0.04994 gram. albumen in 100 C.C. of urine. The Gravimetric Method. The average of two estimations of albumen in 100 C.C. of the urine was 0.0506 gram., hence the difference in the results of both methods is 0.0006 gram. ALBUMINOUS URINE 111. (1). 30 C.C. of the filtrated urine, 20 C.C. water. (a). 5 C.C. of the diluted urino required 34.35 C.C. 6 normal KOH. (b), 5 C.C. of the diluted urine required 34.3 C.C. + normal KOH, average 34.33 c.c., (2). 30 C.C. filtered urine, 20 C.C. Almh’s solution, mixed and filtered. (a). 5 C.C. of the filtrate required 35.7 C.C. + normal KOH. (a). 5 C.C. of the filtrate required 35.8 C.C. ncjrmal KOH, average 35-75 c.c., cor- responding to 1.33 gram, nitrogen in 100 C.C.of the undiluted urine. The difference in the quantities of nitrogen in 100 C.C. before and after the separation of albumen is 0.1334 gram,, corresponding to 0.8497 gram. albumen in 100 C.C. of the urine. The Gravimetric Nethod. The average of three estimations of albumen by the gravimetric method was 0.8557 gram. albumen in 100 C.C. of the urine, hence the difference in results obtained by both methods is 0.006 gram. albumen In 100 C.C. of the urine. ALBUMINOUS URINE IV, (1 j. 20 C.C. of the filtered urine, 10 C.C. water. corresponding to 1.4634 gram. nitrogen in 100 C.C. of the undiluted urine.THE ANALYST. 13 ~- ~~~ ~~ (a). 5 C.C. of the diluted urine required 35.75 C.C. 4 normal KOH. (a). 5 C.C. of the diluted urine required 35-85 C.C.4 normal KOH, average 35*8 c.c., corresponding to 1.1928 gram. nitrogen in 100 C.C. of the undiluted urine. (2). 20 C.C. filtered urine, 10 C.C. Almh’s solution, mixed and filtered. (a). 5 C.C. of the filtrate required 36.1 C.C. + normal KOH. (6). 5 C.C. of the filtrate required 36.1 C.C. normal KOH, corresponding to 1.1676 gram. nitrogen in 100 C.C. of the undiluted urine. The difference in the quantities of nitrogen found before and after the removal of the albumen is 0.0252 gram., correspond- ing to 0*1605 gram, albumen in 100 C.C. of the urine. The Gravimetric Method. The average of two estimations of albumen by the gravimetric method was 0.1551 gram. albumen in 100 c.c, of the urine, hence the difference in results obbained by the two methods is 0.0054 gram.in 100 C.C. urine. ALBUMINOUS URINE V. (1). 20 C.C. filtered urine, 10 C.C. water. (a). 5 C.C. of the diluted urine required 36.00 C.C. 6 normal KOH. (a). 5 C.C. of the diluted urine required 36.15 C.C. Q normal KOH, average 36.1 c.c., (2). 20 C.C. filtered urine, 3 C.C. of Almhn’s solution, 7 C.C. water, mixed and filtered. (9). 5 C.C. of the filtrate required 38.2 C.C. $ normal KOH, corresponding to 0.9912 gram. nitrogen in 100 C.C. of the undiluted urine. The difference in the quantities of nitrogen found before and after the removal of the albumen is 0.1764 gram. corres- ponding to 1.1236 gram. albumen in 100 C.C. of the undiluted urine. The Gravimetric Method. The average of two estimations of albumen by the gravimetric method was 1.1292 gram.albumen in 100 C.C. of the urine ; the difference, therefore, in the results obtained by the two methods is 0.0056 gram. albumen in 100 C.C. urine. ALBUMINOUS URINE VI. corresponding to 1.1676 gram. nitrogen in 100 C.C. of the undiluted urine. (1). 20 C.C. filtered urine, 10 C.C. water. (a). 5 C.C. of the diluted urine required 40.85 C.C. (b). 5 C.C. of the diluted urine required 40.75 C.C. 5 normal KOH, average 40.8 c.c., (2). 20 C.C. filtered urine, 4 C.C. Almdn’s solution, 6 C.C. waterj mixed and filtered. (a). 5 C.C. of the filtrate required 42.9 C.C. & normal KOH. (6). 5 C.C. of the iiltrate required 42.9 C.C. normal KOH. corresponding to 0,7728 gram. nitrogen in 100 C.C. of the undiluted urine. normal KOH, corresponding to 0*5964 gram. nitrogen in 100 C.C.of the undiluted urine ; the difference, therefore, in the quan- tities of nitrogen found before and after the removal of the albumen is 0.1764 gram., corresponding to 1.1236 gram. albumen in 100 c,c. of the undiluted urine. The Gruvimetric Method. The average of two estimations of albumen by tho gravimetric method was 1.1279 gram. albumen in 100 C.C. of the urine; hence the difference in the result obtained by the two methods is 0.0043 gram. albumen in 100 C.C. of the urine. ALBUMINOUS URINE VII. (1). 20 C.C. filtered urine, 10 c,c. water.14 THE ANALYST. (a). 5 C.C. of the diluted urine required 40.4 C.C. + normal KOH, oorresponding to (2). 20 C.C. fiitered urine, 5 C.C. Almh’s solution, 5 C.C. water, mixed and filtered. (a). 5 C.C. of the filtrate required 41.5 C.C.6 normal KOR, corresponding t o 0.714 gram. nitrogen in 100 C.C. of the undiluted urine. The difference in the quantities of nitrogen found before and after removsl of the albumen ia 0.0924 gram., corresponding to 0.5885 gram, albumen in 100 C.C. of the undiluted urine. The Qravimetric Method, 0.8064 gram. nitrogen in 100 C.C. of the undiluted urine. The average of two estimations of albumen by the gravirnetric method wag Oq5953 The difference in the result8 obtained by the gram. albumen in 100 C.C. of the urine. two methods is 0*0068 gram. albumen in 100 C.C. of the urine. Albominons Urioe. I. 111. IV. V, Ir. vr. mr. SUHXARY OF RESULTS. Per Cent. of Albumen Per Cent. of Albumen by New Method. by Gravimetric Method. 0-4042 0.4399 0-0499 0.0506 0-8497 0-8557 0.1605 0*1551, 1,1236 1.1292 1.1236 1.1279 0.5885 0.5953 Difference in HesuM8.0.0357 0.0006 0 -006 0.0054 0-0056 0-0043 04068 By the resulta of estimations of albumen made by the two methods, the average 8rrUr is Oa0092 per csn&, %ha maximum being 0-0357 per 06Lzt., the minimum 0,0006 per cent. The average error in 35 estimations of albumen made by DiUner,” employing the method of EBbach and the gravimetric method, is 0.054 per cent,, the quantity of albumen in the urine being from 0.05 to 2.13 per cent. fa 73 per cent. of 8 great number of estimations of albumen in urine made by 0. Hamrnstrstea,t employing Brandberg‘s method and the gravimetric method, the average error is nearly 0.06 per cent. ; however, in many cases, the error reached In estimating albumen in urine by the new method a, great exem8 of tan& acid should not be employed in separating the albumen, as it i s oxidised very slowly by euIphumc acid.For ordinary quantitieg of albumen in urine equal volumes of Almh’s solution sad urine are sufficient, for small quantities one volume of Almen’s solution and two volumea of urine, and in case the albumen ie two per cent. the urine should be diluted with water from one to two volumes before making the estimations. To aeparab the albumen, 10 C.C. of the filtered urine is introducsd With 10 c.c. Almdn’s solution into a 50 C.C. flask, and sfter mixing well, the fluid is filtered through a dry filter-paper into a dry beaker, 5 a c . of the filtrste i i subjected to the action of 10 C.C. concentrated sulphurk acid, 811 in the original method of Kjddahl.Whether the dilution of the urine is I to 2 or I to 3, the albuminous 0.2 permnt. * Esbaohs Albuminimeter. Upsala Ekaref6r. Fiirhand. 21,1886. f Upsala Ukarefiirening Forbandlingctr 18, 139.THE ANALYST. 15 ~~ urine is diluted to the same degree, and 5 C.C. is employed in Kjeldahl's method. To absorb the ammonia, 10 C.C. normal sulphuric acid is employed, In calculating the quantity of *albumen in urine from the results of the estimations, instead of sub- tracting the weight of nitrogen of 100 C.C. of the urine proper from the weight of the total quantity of nitrogen in 100 C.C. containing albumen, and multiplying the difference by 6.37 for the quantity of albumen, the process may be shortened in the following way: Subtract the number of C.C.normal KOH employed in the two titrations, and multiply the difference by 0*0028, and the product of which by 40. The h a 1 product is the quantity of nitrogen in 100 c.c of the undiluted urine, which, multiplied 6.37, gives the per cent. of albumen If the urine is diluted from 1 to 3 volumes in both cases, the weight of nitrogen is multiplied by 60, to obtain the quantity of nitrogen in 100 C.C. of the undiluted urine. Serum-albumen and serum-globulin, the bodies estimated by the gravimetric method, are not exactly of the same chemical cmatitution, and hence the employment of the factor 6.37 would not lead to correct results in all cases. The per cent. of nitrogen in serum-globulin, according to Hammarsten, is 15-85, while the per cent. of nitrogen in serum-albumen is 15.7. The factor with which to multiply the weight of nitrogen to obtain the weight of serum-globulin is 6.31 instead of 6-37. Ad a rule, however, serum- globulin accompanies serum-albumen in the urine in small quantities, so that the number 6.37 may be employed with cgmparative safety. On the other hand, for exact patho- logical investigations, the weight of nitrogen of albuminous bodies excreted by the kidneys affords a more certain datum than the quantity of albumen. This is apparent when the fact is taken into consideration, that the per cent. of albumen in the urine, as determined by any of the methods now employed, does not represent a deiioite weight of nitrogen. The new method has the additional advantage of determining the total quantity OF nitrogen of the normal nitrogenous constituents of the urine, which, taken into account with the weight of nitrogen of albuminous bodies, is doubtless of importance to the pathologist .-Chemica I Laboratory, Indiana University, Bloomington.

ISSN:0003-2654    

DOI:10.1039/AN8911600007

出版商:RSC    

年代:1891

数据来源: RSC

摘要:

THE ANALYST. 15 STUDY OF A METHOD FOR THE QUANTITATIVE DETERMINATION OF BY F. G. WIECHMANN, PH.D.* PART I. THE quantitative determination of sucrose, invert-sugar and dextrose, or levulose, when these substances occur together, presents a problem of considerable interest and im- portance. Winter? suggested a method of separating sucrose from dextrose and levulose, and dextrose from levulose. It consists in adding ammoniacal acetate of lead,: made im- mediately before use, to the solution of the sugars, until there is no further precipitation. The precipitate, which is ordinarily of a dazzling white colour, is digested with a great amount of water, and then filtered. Decompose this compound SUCROSE, INVERT-SUGAR AND DEXTROSE, OR LEVULOSE. The filtrate contains the sucrose as a lead compound.* School of Mines Quarterly. t Zeieitschijt des Vereines f i i i B.iiben~~~cker-ind1Lstr.ie, 1888, vol. xxxviii., page 182. Add ammonia to acetate of lead as long as the precipitate just continues to disappear.16 THE ANALYST. by carbonic acid gas, and filter off the carbonate of lead. This solution then contains the sucrose. Wash the residue thoroughly with water, then suspend it in water and saturate with carbonic acid gas. The filtrate contains the dextrose. The precipitate consists of carbonate of lead and of a compound of lead with levulose. Wash well with water, then suspend the precipitate in water and pass in sulphuretted hydrogen. The precipitated sulphide of lead is filtered out, washed thoroughly, and the filtrate, to which the washings have been added, is concentrated on a water-bath, and the levulose in it determined.This method aims at the actual separation of the sucrose, the dextrose and the levulose, and thus, of course, permits of the separate determination of each constituent, But even if this method were perfectly satisfactory and reliable, which the writer, from his experiments, is strongly inclined to question, even then it would hardly prove a desirable method for an analytical determination on account of the time required for its execution. Other attempts to determine levulose and dextrose when in combination, have been attempted. As, however, fluctuations of temperature affect to a marked degree polariscopic determinations of invert-sugar solutions (invert-sugar, levulose), it seemed to the writer that a method which should bo entirely independent of optical analyses, and be based wholly on data obtained by gravimetric methods, would be the most desirable.Tollens, in his Kurxes Handbuch der lirohlenhydrate, 1888, contains the following :- ‘6 If levulose is mixed with dextrose, or with any other glycose less sensitive to acids, the sum of the glycoses may be determined with Fehling’s solution. Then the levulose may be destroyed by hydrochloric acid, according to Sieben’s directione, and, after neutralising by sodic hydrate, the remaining dextrose may be determined, and the difference calculated as levulose.” If a reliable process could be based on this suggestion, it would prove a simple and rapid method for the estimation of the sugars named, when occurring together.I n the following pages there will be described a course of analyses, and the methods of calculation deemed necessary to attain the desired result. The estimations to be made consist of the following :- 1. Total sucrose. 2. Total reducing sugars. 3. Dextrose, after destruction of the levulose by Sieben’s method. For the tables expressing the relation between the copper precipitated and the sucrose, the invert-sugar, the dextrose and levulose respectively, reference must be made to the memoirs cited. The Fehling solution, used in all of the following determinations, has consisted of: Sulphate of copper, crystallised, 34,639 grammes in 500 C.C. of water, Rochelle salts, crystallised, 173.000 grammes in 400 C.C. of water. Sodic hydrate, crystallised, 50*000 grammes in 100 c.c, of water.This gives a filtrate and a residue. These are, however, based either entirely or partially on optical analyses.THE ANALYST. 17 I. DETERMINATION OF TOTAL SUCROSE.* Weigh out 13.024 grammes of sample. Dissolve with about 75 C.C. of water in a 100 C.C. flask.? Add 5 C.C. of hydrochloric acid containing 38 per cent. HCYl (specific gravity, 1.188). Heat in two or three minutes on a water-bath up to between 67’ and 70° C. Then keep at this temperature (as close to 6 9 O C. as possible) for five minutes, with constant agitation. Remove 50 C.C. by a pipette, place in a litre flask, and fill up to 1000 C.C. Of this solution take 25 C.C. (cor- responding to 0,1628 gramme of sample), neutralise the free acid present by 25 C.C.of a solution of sodium carbonate, prepared by dissolving 1-7 grammes of crystallised sodium arbonate in 1000 C.C. of water. Then add 50 C.C. of Fehling’s solution, heat to boiling as directed in determination of total reducing sugars, and boil for three minutes. Cool quickly and make up to 100 C.C. IT. TOTAL REDUCING SUGARS.: Weigh out 26.048 grammes. Place into a 100 C.C. flask, clarify with basic acetate of lead, make up to 100 c.c., filter and polarise. Take an aliquot part of the filtrate, add sodium sulphate to remove any lead present, make up to a definite volume, and filter. It is best to arrange the dilution so that the 50 C.C. of this filtrate, which are to be used for the determination of the total reducing sugar, will precipitate between 200 and 300 mgrs, of copper. To 50 C.C.of the sugar solution prepared as above, add 50 C.C. Fehling’s solution (25 C.C. copper sulphate and 25 C.C. of Rochelle salt-soda solution). Over the wire gauze above the flame lay a sheet of asbestos, provided with a circular opening of about 6.5 cm. diameter ; on this place the flask, and arrange the burner in such a manner that about four minutes are consumed in heating the solution to the boiling-point. From the time that the solution starts t o boil--the moment when bubbles arise not only from the centre but also from the sides of the vessel-continue to boil for exactly two minutes, with a small flame. Then remove the flask from the flame immediately, and add 100 C.C. cold distilled water from which the air has previously been removed by boiling.§ Then filter through an asbestos filter, wash and reduce to metallic copper, This operation is carried out in the following manner : Clean thoroughly a small straight calcium chloride tube, or any other tube of similar pattern.Introduce asbestos fibres I/ so as to fill about half of the bulb. Draw air through while drying, cool and weigh. Connect with aspirator, filter the precipitated Cu,O, wash with hot water, then, having changed the receiving flask, wash twice with absolute alcohol and twice with ether. Having removed the greater part of the ether by an air-current, connect the upper part of the filter tube by means or” a cork and some glass tubing with a hydrogen apparatus, and heat with a small flame, whose tip is about 5 cm.below the * Qerman Government Method. See Die Dextsche Zuckevindustrie, 1885. Besondere Beieage zu, t Do not add any basic acetate of lead for clarifying purposes, as this will introduce a source of $ School of Mines Qua.rterly, vol. ix , No. 1, 1888. 5 The water is added to prevent subsequent precipitation of cuprous oxide, 11 The asbestos must first be prepared by washing successively with a solution of caustic soda (not too concentrated), boiling water, nitric acid, and again with boiling water. When filled into the glass tube, the asbestos is made to rest on a perforated platinum cone, No. 27. error, and yield results too low.18 THE ANALYST. bulb containing the Ca,O. two or three minutes. through and the tube is then weighed, copper by washing with dilute nitric acid.The reduction in the current of hydrogen gas is finished in After the asbestos-tube has been cooled in the current of hydrogen, air is drawn After an analysis is completed, the asbestos is readily freed from the adhering 111. DEXTROSE BY ALLIHN’S METHOD.* Take 30 C.C. copper sulphate solution, 30 C.C. Rochelle salt-soda solution,? 60 C.C. water. Then add 25 C.C. of the solution to be tested, which must, however, not contain more than 1 per cent. of the active substance, and boil for two minutes. IV. LEVULOSE BY LEHMANN’S METHOD.: Heat to boiling. Then proceed as before, filtering, reducing the cuproua oxide, etc. Take 25 C.C. copper sulphate solution, 25 C.C. Rochelle salt-soda solution,$ 50 C.C. Then add 25 C.C. levulose solution, which must not contain Boil for fifteen minutes, and proceed as water.Heat to boiling. more than 1 per cent. of the active substance. previously directed. SIEEEN’S METHOD FOR DESTRUCTION OF LEVULOSE. II Take 100 C.C. of a solution made to contain 2 5 grammes of the dry substanc e (invert-sugar, or invert-sugar and levulose), place in a flask, add 60 C.C. six times norma J strength HCI, and heat in a boiling water-bath for three hours. Cool immediately r, neutralise with six times normal strength NaOH solution, make up to 250 C.C. an( 1 filter. The calculation of the results obtained by these methods here described is effectec 1 as follows :- Of the filtrate use 25 C.C. to determine dextrose according to Allihn. C‘cclculation. Step 1 is always the same, and merely establishes whether the dextrose and tho levulose are present in the propprtion of 1 : 1, or, whether either is in excess.Step 2 determines the amount of this excess, be it of dextrose or of levulose. The calculation consists of two steps. The values analytically determined are : No. 1 = Cu reduced by total sucrose + total reducing sugars. No. 2 = Cu reduced by total reducing sugars, No. 3 = Cu reduced by dextrose (after Sieben’s treatment). STEP 1.-No. 1 is Cu reduced by inverted sucrose + total reducing sugars. No. 2 No. 1 minus No. 2 is Cu reduced by inverted sucrose. Report the corresponding value The difference between No. 1 and No. 2, divided by 2, represents the Cu is Cu reduced by total reducing sugars. as sucrose. reduced by the dextrose of the inverted sucrose. Call this value x.~ ~~~~ * E. Wein, Tab& Zlen zur Quantitativem Bestimnicng dt r Zuckmarten, 1888. t 173 grammes Rochelle salts and 125 grammes pQtassic hydrate are dissolved in water and made $ E. Wein, TabelZen zwr Quantitativen Bestimazmg der Xuckerarten, 1888, § Prepared by dissolving 316 grnmmes Rochelle salts and 250 grammes sodic hydrate in water 11 ZeitsclujSt des j>wi?tesfiir RiiBen.:itckel.-iii(Iitsfrif, vol. xxsiv. p. 869. up to 500 C.C. and making up t o 1 litre.THE ANALYST. 19 No. 3 is Cu reduced by total dextrose (after Sieben's treatment), No. 3 less x is Cu reduced by the dextrose of the total reducing sugars. y If 2y -- No. 2 invert-sugar only is present. If 2y *No. 2 free dextrose is present. If 3y P No. 2 free levulose is present.STEP 11.-When 2y >No. 2. No. 2 is Cu reduced by total reducing sugars. from the total reducing sugars. No. 2 minus y = Cn reduced by the levulose of the total reducing sugars. this value p . p 2 = 2p = Cu reduced by invert-sugar. No. 2 is Cu reduced by total reducing sugars. No. 2 minus 2p = Cu reduced by free dextrose. STEP IT. When 2y >No. 2. No. 2 is Cu reduced by the total reducing sugars, No. 2 minus 29 = Cu reduced by the free levdose. 111 these calculations no attention has been paid to the fact that the reducing- power of invert-sugar, dextrose and levulose is not identical. The reducing-power of dextrose being considered as 100, that of invert-sugar is 96, and that of lovuloss is 94." For very accurate work: the necessary corrections for these variations must be made. I n order to test the applicability of the method here described for determining invert-sugar, dextrose and levulose, the following experiments were carried out : Four series of experiments were made, embracing, respectively, mixtures of : x is Cu reduced Call this Cu reduced by invert-sugar + free dextrose, if any be present. by the dextrose of the inverted sucrose. value y. Compare this value, 2y, with No. 2. 2 = 2y. If so, report as invert-sugar. Free dextrose is present. y = Cu reduced by the dextrose Call Report as invert-sugar. 2p = Cu reduced by invert-sugar. Free levulose is present. 2y = Cu reduced by invert- sugar. Report as invert-sugar. I. Invert-sugar and dextrose. 11. Invert-sugar and levulose. 111. Sucrose, invert-sugar and dextrose. IV. Sucrose, invert-sugar and levulose. Of course, from the very nature of the test, the sucrose becomes inverted, and SO really Series 111. and IV., as well as I. and II., are only mixtures of invert-sugar and dextrose, or of invert-sugar and levulose ; but the proportions between the invert-sugar and the diextrose, or the levuiose, respectiveiy in Series 111. and IT., have been 80 arranged as to approximately correspond to the composition of certain raw sugars. (To be c0ntinued.j

ISSN:0003-2654    

DOI:10.1039/AN8911600015

出版商:RSC    

年代:1891

数据来源: RSC

摘要:

THE ANALYST. 19 NEW BOOKS. CHEMICAL ARITHMETIC, PART I. A COLLECTION OF TABLES, MATHEMATICAL, CHEMICAL, B Y w. DITTMAR, LL D., THIS work is intended to ultimately consist of two parts, the first of which contains all the tables and constants, while the second is to be an exposition of their application to the solution of all arithmetical problems connected with chemietry. The first volume is * Soxhlet, JoumaE f i i y Pracktische Chenzie, vol. xxi., pp. 289 and 290. AND PHYSICAL, FOR THE USE OF CHEMISTS AND OTHERS. F.R.S. GLASGOW : W. HODGE AND Co., 26 BOTHWELL STREET. --20 THE ANALYST. now bAfore us, and it may be a t once admitted that Dr. Dittmar has produced an exceed- ingly useful and complete book, and that his claim to have provided the general analyst with a set of tables and constants sufficient for all his ordiaary routine work, without going further, is entirely borne out.We think that, few analysts will fail to keep this book upon their laboratory shelf. ELECTO-CHEMICAL ANALYSIS. BY EDGAR F. SMITH, PROFESSOR OF ANALYTICAL CHEMISTRY 1~ THE UNIVERSITY OF PENNSYLVANIA. PEILADELPAIA : P. BLAKESTON, SON AND Co., 1013, WALLNUT STREET. THIS little work includes within 11 6 pages a cmcise account of the application of electro- lysis to chemical analysis. Commencmg with an explanation of constants, batteries, and the general theory and practics of electrolysis, i t takes up in succession (1) the estimation of metals, (2) the separation of metals, and (3) oxidation by the electric current. Any chemist wanting to see a t a glance all that has been done in this ever-advancing branch of analysis up to date, will find the book easy t o read, well expressed, and students will obtain by its perusal a good stock of general ideas on the subject.MICRO WRGANISXS, INCLUDING AN ACCOUNT O F RECENT EXPERIMENTS ON THE DESTRUCTION OF MICROBES IN CERTAIN bmx"ous DISEASES. BY A. B. GRIFFITHS, Ph.D., F.R.S.E., E.C.S. LONDON : BAILLIERE, TINDALL AND Cox, 20, KING WILLIAM STREET, STRAND, ALTHOUGH, of course, a large portion of this book of 350 pages is specially written for medical men, yet there are parts intensely interesting to the public analyst, who is con- tinually brought into contact with sanitary matters in assisting his medical officer with experimental help. The methods of bacteriological research are simply, yet cletlrly, laid out, and the illustrations of the microscopic appearances are drawn as they really appear, without the fantastic magnifications and exaggerations to which microscopists are so prone in published pictures, and which the unhappy reader, who does not possess a S25- apochromatic objective, generally fails t o realise in practice.To medical men the book should simply be invaluable, being right up t:, date, and yet n9t so ponderous but that it can be easily digested in spare momente. UNTERSUCHUNGEN AUS DER PRAXIS DER GAHRUNGSINDUSTRIE. BY DR. EMIL C. HANSEN, A SECOND and considerably enlarged edition of this notable work has just appeared. It is written for the practical brewer, and c~nsequently treats the subject chiefly on its technical side, only so much theoretical matter being introduced as is necessary to render the subject intelligible.The process by which the small sample of yeast, grown in the laboratory from one single yeast cell, is increased into a quantity sufficient to carry out fermentation on a commercial scale, is minutely described, as is also the apparatus required for the process. By means of an apparatus of this kind, which by no means demands an immoderate outlay, the brewer is enabled to secure for himself a constant supply of identically the same yeast, an advantage to him almost inestimable. We note the con- tinued extension of Dr. Hansen's process, which is now more or less ased in every portion of the civilised globe, and has met with the most unqualified approval of many of thh leading authorities on brewing matters both in this country and abroad. CARLSBERG, MUNICH, OLDENBOURCH. CORRESPONDENCE. [The Fditm i8 not in any way responsibh for opinions expressed by ltis cmrespnde?&.] To the Editor of tJLe ANALYST. DEAR SIR,-With reference to the \modified Feleitmann test, using aluminium instead of zinc, attributed to J3ofessor Johnson in the ANALTBT of this month, you will find an account of the same modification in the ChenticaE News of April 18th, 1873, as published therein by myself. Yours obediently, J. W. GATEHOUSE. 36, Brcad Street, Bath, December 4tb, 1890.

ISSN:0003-2654    

DOI:10.1039/AN8911600019

出版商:RSC    

年代:1891

数据来源: RSC