摘要:

THE ANALYST'. APRIL, 1897. A SPECIFIC GRAVITY PIPETTE. BY W. F. KEATING STOCK, F.I.C. (Read at the Meeting, January 13, 1897.) I HAVE lately found the little instrument described below of great use in cases where the gravity of small samples of castor-oil, glycerin, and other matters of high viscosity was required, It consists of a 10 C.C. pipette, with the bulb occupying a, central position on the stern. The bulb is of the usual elongated form, but instead of being86 THE ANALYST. cylindrical, it has a, flat side, which gives it a stable seat on the pan of a balance. It is six inches in length, and each end of the stem is closed by a ground glass cap, having a good long hold on the stem. The graduation mark is placed one inch below the upper orifice of the stem, and the cap on the lower end is ground so as to fit within 1 m.m.of the point. The point is of such a bore that glycerin passes freely at ordinary temperatures under slight pressure. To use the pipette a piece of suitable size indiarubber tubing is slipped over the open upper end, the liquid to be tested is brought to the required temperature, and the pipette is filled through the pointed end by sucking at the indiarubber tube; when the liquid has risen just above the mark the point is closed by a, finger, the indiarubber tube is removed, and the first finger of the right hand is placed over the orifice, the pipette being then held, as usual, between the thumb and second finger. The lower part of the stem is then freed from liquid by wiping with soft filter paper.The liquid is adjusted to the mark and the lower cap is put on. A little roll of filter paper is now used to remove any liquid adhering to the inner walls of the tube above the graduation mark, the upper cap is put in place, and the whole instrument is then wiped clean with a soft cloth, and is ready for weighing. It is not my wish to compare it with any other form of specific gravity apparatus. My own instru- ment was made by cutting down a 10 C.C. pipette and fitting it with caps, etc., in the laboratory. Messrs. Brady and Martin, of Northumberland Road, Newcastle on- Tyne, have askefi to be allowed to reproduce it in convenient sizes (probably 5, 10 and 25 c.c.), and they will probably have the pipette for sale shortly, under the name of '' Stock's Specific Gravity Pipette." DISCUSSION. I have found it easy to use, easy to clean, and accurate. Mr. RICHMOND desired to know how Mr. Stock ascertained that the liquid was of the proper temperature within the instrument. Mr. STOCK said he had not determined the difference between glycerin at 15.5" C. in a small beaker and the temperature of the liquid in the pipette when it had taken a few seconds to fill; he did not imagine that the difference would be very great.

ISSN:0003-2654    

DOI:10.1039/AN897220085b

出版商:RSC    

年代:1897

数据来源: RSC

摘要:

86 THE ANALYST. NOTE ON THE PRESENCE O F COPPER I N OYSTERS. BY W. I?. LOWE, A.R.S.M., F.I.C. (Read at the Meeting, December 2, 1896.) A SHORT time ago a few oysters were brought to me by a friend, who said he had reason to believe that they contained copper, as he had examined one or two and found copper in them. I n some of the oysters the presence of copper was apparent to the eye, as they were of a bluish-green colour, not all over, but in patches; and in one oyster the whole of the colour seemed to be concentrated in the large muscle used by the animal in opening and closing its shell. On examination I found this to be the case.THE ANALYST. 87 In some of them, however, which also contained a considerable quantity of copper, no bluish colour could be seen, the only difference being that the dark portions of the fish had a somewhat olive-green tint that would not be observed unless they were closely examined.The shells were free from colour, and no copper was found in them. The quantity of copper in a single oyster amounted to 40 milligrammes, or about They were obtained from the Mumbles, near Swansea, and had probably been 2c grain, so that but few of them were required to produce very unpleasant results. laid down in the neighbourhood of some refuse from the copper works. DISCUSSION. The PRESIEENT (Dr. Stevenson) remarked that it was easy, during the operation of incineration over a Bunsen flame, to introduce traces of copper from the burner! so that in cases of this kind it was undesirable to use brass burnersr Mr.BODMER said that certain French oysters of a green colour contained less copper than some others whose colour was much less pronounced, so that the colour did not appear to be due to copper at all. I t was a well-known fact, however, that oysters did, as a rule, contain copper. I n a recent case in which he had been engaged, connected with peas containing copper, it had been brought forward for the defence that a dozen oysters contained rather more than a grain of copper-a quantity somewhat in excess of that contained by 1 lb. of the peas in question. Mr. HARVEY said that, in his experience, copper was very widely disseminated in shell-fish; but he did not regard the green colour constantly observed in them as having any necessary connection with the presence of copper. He instanced the case of an arrangement of tanks for hatching salmon ova, in which the water was suspected of having dissolved copper from the taps, which, however, was found not to be the fact. However, he had always connected the delicate pink colour of the ova of salmon with the presence of a very minute quantity of copper. The PRESIDENT said that the oyster was not singular in containing copper. The human body, for instance, nearly always contained small quantities, especially the liver. I t might not necessarily be a natural constituent, but was probably derived from certain articles of food, or from cooking utensils.

ISSN:0003-2654    

DOI:10.1039/AN8972200086

出版商:RSC    

年代:1897

数据来源: RSC

摘要:

THE ANALYST. 87 THE STATEMENT OF ANALYTICAL RESULTS. BY J. 3'. LIVERSEEGE, F.I.C. (Read at the Meeting, December 2 , 1896.) THE question I wish to discuss is, not how far should analytical results be given in reports, but to ask what are the principles by which the number of significant figures given in a, result should be decided. The following analytical results have been reported in recent prosecutions under the Sale of Food and Drugs Act :- I. A whisky was 34-71' under proof. 11. Alcohol, 78.03 per cent in spirit of nitrous ether.88 THE ANALYST. 111. Peas containing 3-11 grains of sulphate of copper per pound. IV. Butter with 19-88 per cent of water present. V. Milk adulterated with 11.77 per cent. of added water. VI. Coffee adulterated with 68 per cent. of chicory. The first four are statements of fact, the others are expressions of opinion. If two distillations of alcohol often differ by 0.2 per cent., what is the use of giving a second decimal place? Is there any probability that the analysts of 111.and I V . would again obtain 3.11 grains or 19.88 per cent. as the result of other analyses? Ought a milk standard to be used to calculate the added water to 1 per 10,000? If these second decimal places have no meaning, is it wise to appear to claim such a high degree of accuracy ? It seems to me to be reasonable to expect that a secoiid decimal place should not appear on a certificate, unless it is probable that the jirst could be again obtained in another analysis, and that, unless the unit is certain, adulteration should only be certified to 5 or 10 per cent.: in VI., for instance, report 65 or 70 per cent. of chicory to be present. Suppose that in I. another analyst found 34.91" under proof, some magistrates would consider this a much more serious difference than if one analyst certified 34.7" and another 34.9" under proof. 1 also think that in V. the analyst would have felt rather foolish if, in answer to questions, he had admitted that there might be 15 or 20 per cent. of water added, instead of the 11-77 per cent. certified to be present. I n water analysis decimals appear very largely ; the following are single analyses (not averages) taken from standard works. Total solid matter, 108.88, 220.92, 320a72 ; nitrogen as nitrates, 6.499, 14.717, 19.858 ; ammonia, 1,366 ; organic nitrogen, ~141, -298, ,531 ; organic carbon, -142, 1.792, 2-662 ; total hardness, 116.9, 140.8.I t appears to me that in each case the last figure of the result is superfluous and should be omitted, the previous figure being increased by one if the last figure is 5 or more. If 250 C.C. of water were taken for the total solid matter recorded as 220.92, the residue would weigh 0.5523 gramme, and each milligramme error would affect the result by 0.4 ; one decimal place is therefore as much as should be put in any ordinary analysis. I n the determination of ammonia, an error of 0.5 in 5 C.C. of ammonium chloride solution is possible, or 10 per cent. I would suggest that to proceed by units from 1 to 25, and then by 5 up to 100, irrespectively of the decimal place, would be better than putting meaningless figures ; 1.366 would then become 1.4.When the amount of hardness present exceeds 50, the unit figure becomes very uncertain, and 116-9 may for practical purposes be written 117 or 120. Similarly, nitrogen as nitrates, 6.499," should be written 6.5 ; and my experience of organic carbon and nitrogen makes me think that the third decimal place cannot be depended on. I t is no doubt advisable to record the exact figures found in the laboratory notes, but in reports and printed matter these extra figures appear to me to be unadvisablc and misleading. A recent paper on lemon-juice stated that one fluid ounce contained 34,089 grains of citric acid ; the milk analyses giving such specific gravities as '' 1.03148 '' are well known, and the following quotations cannot easily be surpassed.'( Use a 0-0845691 per cent. solution of K4FeCy6, 3Aq." ( I The factors for a volumetric solution of iodine are :-Salicylic acid, 0-18132606 ; thymol, 0.2956772 ; and P-naphthol, 0*37843106." These superfluous decimals also appear in other chemical work.THE ANALYST. 89 I n text-books, the meaning of ‘‘ per cent.” is sometimes doubtful ; it may be by weight, or by volume, or grammes per 100 C.C. I n my own notes, I have for some years been in the habit of using (‘ % in cases where there can be no ambiguity of adulteration (‘ %,” for instance, and for per cent. by weight. Per cent. by wolzmne has been expressed by the sign (‘ vjv ” ( i e . , volume on volume), and grammes per 100 C.C. by ‘‘ w/v ” (Le., weight on volume).These signs show readily exactly what is meant. Alcohol S.G. 0.838, for instance, 84 %=88-7 v/v=70*4 W ~ V . DISCUSSION. The PRESIDENT (Dr. Stevenson) said he thought that, as a rule, insignificant decimal places were better dispensed with, but in some cases it was perhaps a matter of convenience to insert them. For instance, in water analyses, where some of the factors really required the use of three decimal places for their proper expression, it was more convenient to state the results all through to three decimal places than to jump about from two to three. In cases where the third place had no real significance it might be filled by a cipher for the sake of symmetry. MY. ALLEN said that he was in the unusual position of disagreeing with the President, for he thought that, if a fraction were cut short by omitting the concluding figure, the place of this figure ought not to be filled by a cipher, inasmuch as a definite value was thereby assigned to it which was not intended.If the figure was assumed to have no significance whatever, the place ought to be left blank. There was only one excuse for the use of these long decimals, and that was that the chemist gave the results he got. He put them forward, not as the strictly correct results, but as the actual results of his work, and if these results required a decimal fraction to express them, they should be stated accordingly. That was the only excuse, except in the case of gold and steel analyses. The third decimal place in a steel analysis had a distinct significance in the case of phosphorus and sulphur, and affected the second place, where any variation became of consequence.He was afraid the public sometimes looked upon analysts as quacks, more or less, because they reported to two or three places of decimals in cases in which it was exceedingly doubtful if they would get on repetition a result agreeing even to the first place of decimals. The Society itself occasionally offended in this respect, for, in the circulars recently issued to members respecting the form of milk certificates, and which waa made necessary by the decision in the case of Fortune 2,. Hanson, the sum of the results of a milk analysis was directed to be stated to two decimal places ! H e (Mr. Allen) felt very strongly that it was a mistake to pretend to express results with extreme accuracy unless such accuracy could be approached reasonably closely ; and he thought that, except in special cases like those he had mentioned, the sooner the practice was discarded the better.Mr. CASSAL thought there was a great deal to be said on both sides of the ques- tion. He agreed with EL good deal of what Mr. Allen had said, and to a, certain extent with the author of the paper, but it had to be remembered that public analysts were not their own masters in all matters of this sort. Mr. Allen had alluded to milk, and had caused some laughter by mentioning the fact that the statement of results to the second decimal place had been suggested in the Society’s circular ; but what was oneTHE ANALYST.of the effects of thecase of Fortune v. Hanson ? It was this : If public analysts wished to avoid being put to serious inconvenience, and wished to avoid following the practice which in his student days was known as “ cooking,” the percentage of added water would have to be stated to a decimal place in most cases. If the percentage of added water was stated to the nearest whole number, as used to be done, it would be neces- sary to alter the percentage of non-fatty solids, which had now to be given on the certificate, for it necessarily happened that in most cases the percentage of added water calculated from the non-fatty solids ran into a decimal. I t was not necessary, of course, to go to the second place of decimals. With regard to water analyses, he thought that absolutely unnecessary figures ought not to be stated at all, though in one place he had been for a long time practi- cally compelled, through no fault of his own, to state the result of certain water analyses in parts per 100 million (laughter).I t was done originally, he believed, because it was thought that those who had to consider the figures understood whole numbers, but did not quite appreciate decimals, and the result was that they were provided with parts per 100 million ” because they had then got something to catch hold of (laughter). The real way out of the difficulty was to apply cotnmon sense to the matter. I t was one which required to be dealt with according to the individual merits of every case in which it arose. Mr. BEVAN said that the case of Fortune v .Hanson had been to a large extent set aside by the decision in the case of Bridge o. Howard. In that decision it was clearly shown-at least the judge allowed it to be understood-to be quite unnecessary to state the quantity of added water to a decimal fraction, The percentage of solids- not-fat in the case of Bridge v . Howard was 7.95, and the added water, calculated to one decimal place, was 6.5. He (Mr. Bevan) had called it 6 per cent., and the juilge, having made the calculation for himself, said that as a matter of fact the percentage of added water had been under-stated, but took no exception to this, Mr. CASSAL said that his experience was that the accuracy of an analysis would be doubted by non-experts if, when the figures were asked for, the actual figures, including the decimals, were not given, He might say that on one occasion a magis- trate wanted him to leave out the decimal figures in tlie non-fatty solids reported in his certificate in order that the method of calculating the amount of added water might be made “ more clear.” The PRESIDENT said that Mr. Caesal’s experience appeared to be exceptional. He himself had been in the habit for twenty-five years of stating whole numbers only, without fractions, in the case of milk. I n regard to certain other things, such as coffee, he had taken still greater latitude, as he would not venture to distinguish between, say, 55 and 60 per cent. in the case of coffee adulterated with chicory, and he had found magistrates sufficiently reasonable to see the force of this. He was glad to think that the difference of opinion between Mr. Allen and hirn- self was, after ail, but a small one.

ISSN:0003-2654    

DOI:10.1039/AN8972200087

出版商:RSC    

年代:1897

数据来源: RSC

摘要:

THE ANALYST. 91 A M O D I F I E D S C H R I I D P R O C E S S . BY R. W. WOOSNAM. (Rend at the Meetiiy, Ja7zmary 13, 1897.) THE difference of a milligramme in the weight of butter-fat obtained by the usual processes from 5 C.C. of milk is often of much greater importance than would be supposed at first sight. Especially is this the case with separated milks, where a variation of 0.02 per cent. (the result of a difference of one milligramme in the weight) may sometimes even constitute the margin between a good and an only moderate separation. In butter-factories, where large quantities of milk are dealt with, this difference often represents a considerable item in pounds of butter. In order to ensure a more exact result, without at the same time unduly prolonging the process, I have devised the piece of apparatus as shown in the accompanying €gure. It is constructed in two parts, as follows : (A) A boiling-flask, with tap, the mouth ground to fit the top of B.(B) A graduated 100 C.C. burette, with small tap at the side, placed I n making a deterrniiiation, 25 C.C. of the milk are pipetted into the boiling flask A, and about 28 C.C. (roughly) of strong hydrochloric acid added. For this purpose, a 25 C.C. pipette, with stem sufliciently small to pass through the tap, is recommended. The flask is then placed in boiling water, and agitated frequently until the contents assume a pnZe brown colour. This will generally take place in about two minutes, and it is important that the action should not be allowed to preferably at about the 50 C.C. mark.proceed too far, or the sugar caramelized will be, to some extent, extracted by the aqueous ether at the next stage. The flask is now cooled thoroughly, and 50 C.C. of ether added. The tap with which the flask is fitted is then closed, and the whole shaken vigorously for some moments, after which it is fixed firmly into the top of the burette B, the ground-surfaces making a tight joint. When the ether layer has separated, the tap is turned on, to allow the liquids to flow gently into the burette. The measurement of the ether layer is next read off, and, after adjusting the levels of the liquids by manipulating the two taps of the burette, an aliquot part of the ether layer is drawn off from the side-tap into a suitable weighed vessel, the ether driven off, and the fat weighed in the usual manner. The results obtained have been very satisfactory. The advantages claimed are : That a larger quantity of milk may be worked upon ; that the tapped boiling-flask lends itself more perfectly for thoroughly shaking with the ether; that the reading of the ethereal layer is more exact ; that, when desired, more than one aliquot part of the fatty ether may be drawn off; and, lastly, that greater accuracy is obtained than by the old methods. The apparatus is made by Messrs. Miiller, of 148, High Holborn,

ISSN:0003-2654    

DOI:10.1039/AN8972200091

出版商:RSC    

年代:1897

数据来源: RSC

摘要:

92 THE ANALYST. THE DISTILLATION O F FORMALDEHYDE FROM AQUEOUS SOLUTIONS. BY NORMAN LEONAHD, B.Sc., HARRY M. SMITH, BND H. DROOP RICHMOND. (Read at the Meeting, Febrzia7.y 3,1897.) IN a paper (ANALYST, xxii., 5 ) two of us (L. and S.) have given the results of distillation of aqueous solutions of formaldehyde, expressed as grammes of formal- dehyde distilled in given fractions. I n the ANALYST (xx., 193) one of us ( R ) has shown that when dilute solutions of the fatty acids of the acetic series are distilled, the quantity of acid found in the distillate is expressed by the formula provided that condensation in the retort does not take place, y =percentage of total acid in distillate. x: =volume of distillate expressed as percentage. I t was further shown that a is the rate of distillation-ie., the ratio of the per- centage of acid in the vapour ( i e .) parts of acid per 100 of vapour) to the percentage of acid in the solution in the retort (,i.e., parts of acid per 100 of solution). We have examined the results yielded by the distillation of formaldehyde, and find that the quantity of formaldehyde distilled is expressed by the formula The annexed table gives the results found compared with those calculated by the formula ; it is seen that the agreement is very close : Vol. of Frac- tion Distilled. 0- 20 20- 40 40- 60 60- 80 80 - 100 Found Calc. *0024 -00240 a0021 -00204 -0017 *00164 *0011 -00117 *0005 -00055 Formaldehyde in Fraction. Found Calc. *0023 -00234 -0018 -00199 -0017 *00160 -0012 -00114 -0006 -00053 Total . . , I *0078 *00780 I -0076 -00760 Found Calc. -0026 -00237 -0020 -00201 1 -0031 -00334 a0077 ~00770 Found Calc. -199 -208 -180 -177 -139 -142 -105 -1015 -053 -0475 *676 -676 We may again point out that the volatility of a substance in dilute aqueous solution is entirely independent of the properties of the substance in a pure state, and is solely dependent on its solubility in water. The following table of rates of distilla- tion and properties will show this : Name. Rate of Distillation. Properties in Pure State. Formaldehyde ... 1.65 ... Gas, b.-p.,-H" Formic acid ... -4 ... Liquid, ,) 100" Acetic acid ... -667 ... ,, ,, 118" Propionic acid ... 1-111 ... 9 7 ), 137" Butyric acid ... 2.0 ... 2 ) ,, 162.5"

ISSN:0003-2654    

DOI:10.1039/AN8972200092

出版商:RSC    

年代:1897

数据来源: RSC

摘要:

THE ANALYST. 93 THE COMPOSITION O F MILK AND MILK PRODUCTS. BY H. DROOP RICHMOND. (Read at the Meetiny, Marclz 3, 1897.) OF the 32,362 samples examined in the laboratory of the Aylesbury Dairy Company during 1896, 25,723 consisted of milk. The average composition of 11,633 samples taken from the railway churns on arrival at the dep6ts of the company is given iu Table I. TABLE I.-AVERAGE COMPOSITION OF MILK INWARDS. Month. ~ January ... February ... March ... May . . . . . . June . . . . . . July . . . . . . September . . , October ... November ... December ... Average ... April ... August ... Morning Milk. /- Specific Gravity. 1.0327 1.0327 1 *0327 1,0327 1.0328 1.0323 1 *031 ti 1.0315 1.0321 1-0328 1.0329 1.0327 1-0325 Total solids- Solids. not-Fat 12-76 3-71 9-05 12-65 3-61 9.02 12.63 3-61 9.02 12.58 3.56 9.02 12.42 5.40 9'02 12.31 3-42 8.89 12-24 3.50 8.74 12.40 3.65 8.75 12.61 3.71 8-90 12.83 3.75 9.08 12.89 3.78 9-11 12-87 3.80 9.07 12.60 3-63 8.97 - ~ - - Evening Wilk.Average. , /- \ Specific: Total Solids- Specific Total Solids- iravity. Bolids. Fat' not-Fat. Gravity, Solids. Fat. not-Fat. 1.0321 13.16 4.10 9-06 1.0325 12-96 3.91 9.05 1.0324 13.02 4-00 9.0'2 1.0325 12-82 3.80 9-02 1.0523 12'96 3.95 9-01 1.0325 12.81 3.79 9.02 1.0325 12.93 3.90 9.03 1,0326 12.77 3 - 7 & 9.03 1'0323 12-78 3-79 8.97 1.0326 12-61 3.61 9'00 1.0318 12-55 3-72 8.83 1.0320 12'43 3 57 8-66 1.031'2 12.50 3.80 8.70 1.0314 12.37 3-65 8-72 1.0313 12.69 3.96 8.73 1.0314 12.55 3-81 8.74 1.0318 13.07 4.15 8.92 1.0319 12-84 3.93 8'91 1.0324 13.23 4-17 9.06 1-0326 13.03 3.96 9-07 1.0325 13-27 4-17 9-10 1'0327 13.08 3 97 9-11 1.0324 1324 4'17 9.07 1-0326 13.01i 3-99 9-07 1.0321 12.95 3.99 8-96 1.032.3 12.78 3.81 8 97 __ ---- ~ -__--- ~ --___ ---- __ ___ The fat in all these samples has been estimated by a centrifugal process of the Leffmann-Beam type, various centrifugal machines having been used ; the solids-not- fat and total solids have been in the bulk of the analyses calculated by the formula given in a previous report (ANALYST, xix.65, cf. also xx. 57). In 100 test experiments the difference between the results calculated and those found has not exceeded 0.15 per cent. The following analyses are of abnormal milks : I. 11. Specific gravity.. . 1.0292 1-0303 Total solids ... ... ... ... 11.57 ... 12-42 Fat ...... ... ... ... 3.51 ... 4-00 Milk- sugar ... ... ... ... 3-41 ... 3-71 Proteids ... ... .., .. 1 ... 3.84 ... 3.89 Ash ... ... ... ... ... 0.81 ... 0.82 Solids-not-fat ... ... ... ... 8.06 ... 8.42 ... ... ... ... A further sample (not authenticated) was received from the same source as No. I., and was sour when analysed. The results were : Total solids ... ... ... 11-17 Fat ... ... ... ... 3-65 Ash ... ... ... ... 0.71 Solids-not-fat ... ... ... 7.52 Proteids ... ... ... ... 3-36 containing nitrogen -52894 THE ANALYST. I would draw attention to the fact that the best method of analysing sour milks is to estimate fat by Werner-Schmid method, total nitrogen by Kjeldahl method, and ash; these three data, taking 3.0, 50, and -70 as limits respectively, are, in my opinion, sufficient to show whether the sample be genuine or adulterated.No reliance can be placed on an estimation of the solids-not-fat in a sour milk, because it is in itself unreliable; differences of over 1 per cent. were found in the total solids of a sour milk, between estimations in one case drying till the loss was less than 1 milligramme in one hour, and in the other till the loss was less than 3 milligrammes in three hours. It has long been known that milk received on Mondays is poorer than that received on other days of the week. The following table gives the average percentage of fat found on each day of the week; it is deduced from a series of 5,414 analyses, and is chosen, not because it represents the average composition of milk, but because the results are comparable from day to day.Day. Percentage of Fat. Sunday ... ... ... ... 3-74 Monday ... I . . ... ... 3-70 Tuesday ... ... ... ... 3.78 Wednesday ... ... ... 3.75 Thursday ... ... ... .... 3.75 Friday ... ... ... .,. 3.75 Saturday ... ... ... ... 3.73 Average of week ... 3.74 The average composition of clotted cream was : Maximum. Minimum, Average. Total solids ... ... 75.18 56.42 67.64 Eat ... ... ... 68.23 46.66 59.16 Ash ... ... ... 0.90 0.52 0.68 Solids-not-fat ... ... 11.31 6.40 8.48 The following percentages of water in butter have been found during the year : Description. Maximum. Minimum, Average. English fresh butter ... 15-18 12.40 13.82 9 , salt 7 , .,. 17.92 10.46 13.94 French fresh ,, ... 15.94 11-76 14.40 9 9 salt 7 ) ...14.35 9-35 12-21 The samples of English butter were all examined shortly after churning; it is seen that there is practically the same percentage of water in fresh and salt butter. The sample containing 17.92 per cent. of water was a very small quantity, churned for a special purpose, and was not worked to the same extent as usual. Two other samples of salt butter contained just 16 per cent. of water, and the evidence obtained this year goes to show that the limit of 16 per cent. which has been proposed for water in butter is a reasonable one. A series of determinations of the refractive index of butters prepared in the laboratory was carried out. The following readings were obtained with Zaiss' butyro- refractometer at 35" C. : Maximum. Minimum. Average. 48.5 45-2 46.5THE ANALYST. I n connection with this, it is interesting t o record a, few other figures : Fat of colostrum of women ... 55.4 52.8 ,, human milk . .. ... 55.4 48 a 2 Olive-oil . . . ... ... 56.8 56*6* Cotton-seed-oil ... ... 61.8 61*4* ... ... 41.2 Palm-kernel-oil ... ... ... ... 52.0 Margarine . . . Maximum. Minimum. 95

ISSN:0003-2654    

DOI:10.1039/AN8972200093

出版商:RSC    

年代:1897

数据来源: RSC

摘要:

THE ANALYST, 95 THE DETECTION OF MIXTURES OF DILUTED CONDENSED OR STERILIZED MILK WITH FRESH MILK. BY H. DROOP R~CHMOND SND L. K. BOSELEY. (Read at the Aleetiizg, March 3, 1897.) THERE are three methods which may be employed for the detection of mixtures of diluted condensed or sterilized milk with fresh milk. The first of these, which was pointed out by Faber (ANALYST, xiv. 141), depends upon the state in which the albumin exists. I t is probable that it is in combination with a base, as on heating milk no coagulation of albumin takes place, but on acidify- ing, or saturating with magnesium sulphate, the albumin separates with the casein. The albumin appears to be changed from a soluble to a colloidal form. Secondly, as we have before pointed out (ANALYST, xviii. 174), if milk has been heated €or some length of time, the rotary power of the milk-sugar undergoes a serious reduction, the cupric reducing power not changing to any appreciable extent.Thirdly, we propose to describe a method that may be of some use in conjunction with the foregoing. I t is based upon the fact that the cream rises with extreme slow- ness-in three hours practically no cream is observed on the surface of sterilized or diluted condensed milk, and in six hours the layer is only about one-tenth of that given by new milk. If sterilized milk be allowed to stand for twenty-four hours, or more, the bulk of the cream will rise to the surface, but the quantity will be less than that yielded by new milk. The cream will, however, contain a distinctly larger per- centage of fat, about 40 per cent., as against less than 30 per cent.in the cream yielded by new milk. The following figures will illustrate this fact : STEBILIZED MILK ALLOWED TO STAND FOR S I X HOURS. Per cent. of Per cent. No. F a t in Milk. Cream Risen. 1. 4.30 1.3 2. 3-80 0.7 3. 4-25 1.8 4. 4.10 1.9 5. 5.35 2.8 Diluted condensed. 6. 3.62 0.3 Per cent. Cream for 1 Per cent. Fat Per cent. Fat per cent. Fab. in Cream. in Skim Milk. -30 23.3 4-05 -18 22.3 3.67 -42 20.6 3.95 -46 24-7 3-70 -52 31.4 4 -60 -08 - - * With sodium light.96 THE ANALYST. STERILIZED MILK ALLOWED TO STAND FOR TWENTY-FOUR HOURS Per cent. N O . Fat in Milk. 1. 4 -30 2. 3.80 3. 4-25 4. 4.10 5. 5 -35 6. 3-62 Per cent. Cream. '7.0 6.0 8.8 8.7 11.1 0.8 Per cent. Per cent. F a t in Skim Milk.F a t in Cream. 46.8 1.10 41.8 1-37 39.0 *90 41-0 *58 41.4 *85 - 3 *48 N E W &fILIi Per cent. of No, Fat in Milk. 1. 4.05 2. 4-20 3. 3.90 4. 3.70 5. 4.45 ALLOWED TO STAXD FOR SIX HOURS. Per cent. Per cent. Cream f g r 1 Per cent. Fat Per cent. F a t Cream. per cent. Fat. in Cream. in Skim Milk 9.2 2.27 174 2-70 11.2 2.66 16-5 2.65 9.8 2.51 15.9 2.60 9.8 2-69 18.0 2.15 13.5 3.03 16.8 2.30 The samples numbered from 1 to 5 were yielded by the same cows in each case. Condensed unsweetened milk, which has been diluted to the original volume with water, has all the analytical characteristics of sterilized milk, and there appears to be at present no method of distinguishing between them. To distinguish new milk, on the one hand, from inilk which has been sterilized on the other, the following methods may be employed : (i.) Place 100 C.C.of milk in a graduated cylinder, and allow it to stand for six hours at 60" F. (15.5" C.) ; note the percentage of cream. If less than 2.5 per cent. of cream for each 1 per cent. of fat in the milk has risen to the surface, the milk may be considered suspicious; if the quantity of cream falls markedly below 2 per cent. for each 1 per cent. of fat, it is highly probable that sterilized milk is present. (ii.) Estimate the albumin by the method of Hoppe-Seyler, or, better, those of Sebelein or Duclaux. If less than -35 per cent. is found, sterilized milk may be con- sidered to be present. (iii.) Estimate the milk-sugar by the polariscope, and also gravimetrically in duplicate; if the difference between the two estiniations be more than -2 per cent., it will be corroborative evidence of the presence of sterilized milk.I t is doubtful whether a proportion of sterilized milk much below 30 per cent. could be detected when mixed with new milk, The proportion of sterilized milk may be deduced from the percentage of soluble albumin by the following formula : Percentage of sterilized miIk == This is based on the supposition that new milk contains 1.4 per cent, of albumin, The following is the formula for deducing the percentage of sterilized milk from 0.4-Percentage of soluble albumin 0.4 while in sterilized milk the albumin is removed. the cream rising test : 2.5 - 2.2 Percentage of Sterilized milk = __ .T E E ANALYST. 97 The estimation of albumin is the most reliable test.There are many causes which influence the rising of cream, such as the temperature to which the milk has been warmed or cooled, the size of the fat globules, which varies with the stage of lactation, and the acidity of the milk, and quantitative deductions may be occasionally misleading. It must be remembered, however, that no sharp distinction can be drawn between milk which has been raised to a temperature over 70" C. for a short period, and which naturally is not sterilized in the true sense of the term, and milk which has been heated for a sufficient length of time to destroy all microbial life. For this reason a milk should not be reported as sterilized solely on the result of a very low percentage of albumin if neither the (' creamorneter " nor the milk-sugar tests give corroborative indications.It is probable that the milk in this case has been merely scalded. The following figures by C. H. Stewart (Brit. Med. Joum., 1896, 626) show the percentage of albumin found in milk raised to various temperatures : Time of Heating. 10 min. at 60" C. 30 7 , 10 ,, &" c. 30 7 , 30 9 , 10 ,) Go c. 10 ,, ibo c. Soluble Albumin in Fresh Milk. ~423 -435 *395 -395 -422 -421 -380 *38 -375 *375 Soluble Albumin in Heated Milk. ,418 -427 -362 .333 -269 ,253 *07 *05 none none The following analyses will show to what extent the method can be depended upon : Percentage Sterilized. No. Fat. 1. 3.86 2. 4-10 3. 3-90 4. 3.70 5. 4.10 6. 4-00 7. 3.75 Per cent. Cream. 7.2 9.6 7.5 4.3 7.4 7.5 7.9 Cream Fat. 1.87 2-34 1 *92 1.16 1.81 1 -88 2.11 Milk- Milk- -30 4.85 4.65 -34 4.79 4.68 029 4.79 4.64 016 4.75 4-57 -26 - - -27 - - -35 - - Albumin. Sugar. Sugar Pol. Actual. Gal. Cream. Cal. Albumin. 33 29 25 Genuine 28 26 27 56 61 60 30 31 35 30 28 32 Genuine. The analyses marked 2 to 7 were made upon mixtures the composition of which was unknown to the operator, those marked 2 to 4 being the work of one of us (R.), those marked 5 to 7 of the other (B.). The results arrived at by analysis are given in the columns marked '' calculated," and the agreement between the two methods and with the actual composition is extremely satisfactory.

ISSN:0003-2654    

DOI:10.1039/AN8972200095

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年代:1897

数据来源: RSC

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98 THE ANALYST. THE ESTIMATION OF MILK-SUGAR I N MILK. BY H. DROOP RICHMOND AND L. KIDGELL BOSELEP. WE have been in the habit of estimating the milk-sugar in milk by the method described by Vieth (ANALYST, xiii. 63); this is a slight modification of that worked out by Wiley (Amer. Chem. Jour., vi., 289), and the novelty in it consisted of the making of corrections for volume of fat, etc. Vieth’s method of calculation is founded on the following assumptions : (a) That the volume of proteids in 100 C.C. is 3.0 C.C. ; (6) that the volume of fat in 100 C.C. is the percentage of fat divided by -93. This last assumption is not strictly correct, the volume of fat being the per- centage of fat multiplied by the specific gravity of the milk and divided by -93, but the error is very small.It is usually sufficient to multiply thg percentage of fat by 1.11 to obtain the volume in 100 C.C. of milk. m7iley and Ewell have recently published (ANALYST, xxi., 182) a method for the estimation of milk-sugar in milk by double dilution and polarization; they make up 65-82 grammes of milk to 100 C.C. and 200 C.C. respectively, precipitate with acid mercuric nitrate and polarize the filtrates. If a equal the reading from the 100 C.C. solution, and b the reading from the and the volume of the precipitate ab 200c.c. solution, the correct reading will be I00 (a - 2b) -__I_ a - b. A series of thirteen experiments to prove the correctness of the method is given, and the volume of the precipitate is calculated in each case; from the series it is concluded that (‘ this correction is less in quantity than the combined volume of the fat and albuminoids.” It appears, however, on recalculation of their figure#, that the volume of the precipitate is wrongly calculated, the formula having been apparently used instead of the correct one given in their paper, and reproduced above. In the table opposite Wiley and Ewell’s figures are reproduced, the volumes of the precipitate being calculated by the correct formula ; the volume of the precipitate is also calculated by Vieth’s method.It is seen that, though the average of the two methods agrees well, there is a, fairly wide divergence between individual results. A comparison of the polarimetric figures of Nos. 1 and 9 will demonstrate that this divergence is chiefly due to the large experimental error of Wiley and Ewell’s method.In these two it happens that the polarization in the 100 c.c flask is the same, while the polarization in the 200 C.C. flask differs only by -07, which is within the limits of reading; this difference of polarization makes 1-5 C.C. difference in the volume of proteids. It also makes a difference of *07 per cent. in the percentage of milk-sugar, while, had Vieth’s method been used, a diEerence of .07” would make a diff’erence of less than -02 per cent, To obtain the accuracy recorded, Wiley and Ewell found it necessary to use a very 100 (a - 2b) bTHE ANALYST. 99 Percent. Fat. 1. - 2. - 3. - 4. - 5. 2.9 6. 4.8 7. 3.1 8. 4.0 9. 1.4 10. 5.5 11. 4.4 12. 2.0 13. 17.6 Polarization in 200 C.C. Flask. 9.37 9.59 9.36 9.60 10.15 10-31 9 49 10.01 9.44 11.05 9.57 9.75 8.72 Mean ...Polarization in 100 C.C. Flask. 19.26 20433 19.20 20.25 20.84 21.21 19.41 20.45 19.26 22.68 19.47 19.93 19.13 Calculated Volume of Precipitate. 1: :;)5.4 4'9\5.1 10*0/ 5.1 5.4 4.3 4.1 3.9 5.0 3.3 4.2 16.2 5.7 Vieth's Method Differ- ence. Volume of Precipitate. 5*0* 5.0 ::: 4.0 5.3 4.1 4.7 2.9 5.8 5.0 3.3 1 4 4 - 1.1 - 0.1 - 0.2 + 0.6 - 1.0 + 0.8 + 1.7 - 0.9 - 1.8 5.5 delicate polariscope with tubes 400 n1.m. long ; with a less delicate polariscope and shorter tubes, the experimental error would be correspondingly magnified. We can only conclude that this method is practically useless, on account of the large experimental error, the waste of time, and large amount of sample required. The only objection toVieth's method is that it is necessary to make a calculation for each sample, which, when several determinations are made at once, is apt to become tedious.To dispense with the calculation, we propose to add to each 100 C.C. of inilk : ( a ) Three C.C. of acid mercuric nitrate to compensate for the volume of the proteids. ( b ) (Fat + 1.11) C.C. to compensate for the volume of the fat. (c) One-tenth of the degrees of specific gravity. (d) A sufficient volume to reduce scale readings to percentages of milk-sugar. With the instrument we use [the Mitscherlich half-shadow polariscope, described by Vieth (ANALYST, xi. 141)], d is 10.0 C.C. to 100 c.c of milk; it may be calculated for other instruments by the formula (jg.31OKo - 100) x X where K = factor neces- sary to convert angular degrees into scale readings, I = length of tube used, and 5' = specific gravity of the milk (which may be taken as 1.032 without appreciable error).If the fat was 3.7, and the specific gravity was 1.0325, then 3 + 4.1 + 3.25 + 10 = 20.35 C.C. must be added to 100 C.C. of milk, or 10.17 C.C. to 50 C.C. We have noticed the fact pointed out by Wiley and Ewell, that the stronger mercuric nitrate solution prescribed by Wiley is liable to discolour the proteids, but we cannot agree with them that it is the xantho-protein reaction ; it is more properly described as Millon's reaction. We find it advantageous, however, to use their weaker solution, and add 15 C.C. of this to 100 C.C. of milk, making up the bulk with water. * These figures art: volumes of sand actually added.100 THE ANALYST.A few test analyses are appended to show that accurate results can be obtained by dilution to obtain direct readings. Direct Dilute Milk Sugar. Volume of Precipitate. Obs. Sp. Gr. Fat. Dilution. R, 1.0305 4.50 121.0 B. R. I.d$40 ;*'60 ldb.4 B. B. 9 , 9 9 9 7 R. i-dboo C ~ O idi.1 Average ... ... Polarimstric Reading. 4.93 4.17 4-95 4-21 5.85 4.93 5.88 4.89 4.82 4.06 4.80 4.08 5.205 4-39 Veith, Wiley and Veith. Wiley and 4.15 3.94 8.0 2.9 Ewell. Ewell." 4.16 3.79 4.92 5.07 4.95 5.48 4.05 4-21 4.04 3.73 4.38 4.37 8.0 -.9 7.0 9.7 7.0 16.0 8.1 11.6 8.1 -4 7.7 6.6 We have also experimented with the action of various preservatives added to milk in the proportion of 1 gramme per 100 C.C. (except in the case of formalin where 2 C.C.were accidentally added) ; the samples were allowed to stand a week in an incubator at 25". Polarization. Original milk . . . ... ... ... 5-63" 1 C.C. Chloroform per 100 C.C. ... ... 5.61" 1 gr. Borax per 100 C.C. ... ... ... 5.50" 2 C.C. Formalin per 100 C.C. ... . . . 5.62" (corrected for dilution). 1 gr. Salicylic acid per 100 C.C. . . . ... 5.61" With the exception of borax, it is seen that all the preservatives prevented any 1 gr. Mercuric chloride per 100 C.C. . .. 5.59" change. DISCUSSION. The PRESIDENT (Dr. Dyer) said that among the many valuable papers in the old volunies of THE ANALYST a very prominent place must be given to those which emanated from the laboratory of the Aylesbury Dairy Company in the days of their old friend Dr. Vieth, and it was very pleasurable year by year to find Mr. Richmond carrying on this work, and bringing before the Society the results of his very large experience.One little point which he noticed in the first paper was the high proportion of ash in two of the abnormal samples of milk. His own experience, and probably that of many others, showed that, when milk gave an abnormally low percentage of total solids, the ash was usually high, at once pointing out the abnormality of the samples, so that they were not easily confused with watered samples. He was much interested in Mr. Richmond's remarks with regard to the nitrogen in decomposed samples, because he had lately heard from another member of the Society (Mr. Smetham, of Liverpool) that that gentleman had been making a some- what extensive series of experiments on the value of the nitrogen factor in dealing with decomposed milks.He had not seen all Mr. Smetham's figures, but as far as * We have, by calculating from our own figures, exaggerated the errors of Wiley and Ewell's method ; roughly speaking, we have about doubled the experimental error.THE ANALYST. 101 the results had gone some time ago, Mr. Smetham had found that the nitrogen remained remarkably constant. I t might be converted into different nitrogenous compounds, but it stayed in the milk, and did not seem to be lost in the form of free nitrogen. He thought that Mr. Smetham would have some results shortly to bring before the Society on this subject’. With regard to sterilized milk, he did not know whether it was suggested by Mr.Richmond that the presence of sterilized milk in ordinary milk was a thing to be deprecated, or regarded as an adulteration. Sterilized milk was generally con- sidered to be a valuable article. I t would probably be more interesting to the public to be able to detect the presence of unsterilized milk in milk that was sup- posed to be sterilized, but to this one would take a shorter cut by making a bacteriological examination. Mr. ALLEN observed that the multitude of figures which had been placed upon the blackboard, and which, after all, only represented a fraction of the results actually obtained, was a sufficient indication of the vast amount of work the authors of these papers had got through; and as a Society, they were very much indebted to Mr.Richmond and Mr. Boseley for laying before them these results, which had now become a very welcome annual institution, the absence of which would be greatly missed. It was interesting to learn that Dr. Vieth’s method for the determination of milk-sugar was able to hold its own with more recent modifications of the process. He had a high opinion of Wiley and Ewell’s method; but if the use of a specially delicate polarimeter wag essential, it militated greatly against the employment of the method in practice. Dr. EDMUNDS raised the question whether sterilized milk, and, in fact, all sterilized foods, did not lose some of their vitalizing properties, especially for young children. Dr. RIDEAL said that he was about to make a similar remark to that made by Dr.Edmunds. He usually lived in the country, but for the last two or three months he had resided in town. It was hardly a chemical matter, but in the country they were in the habit of keeping the milk overnight for the cream to rise. On coming up to London, however, the milk was supplied by a dairy company, and it was found that the cream of this London milk would not rise on standing, which seemed to point to the fact that the mixed milk had not the property of rising as pointed out in the paper. He thought that a consumer buying milk should reasonably expect it, to throw the normal amount of cream on standing. He did not think that either Sterilized milk or humanized sterilized milk had the same value as unsterilized milk, which was probably due to the fact that the ferments present had lost their activity.He had been trying humanized milk from the same firm for st week or two, with results that were not satisfactory, but which were improved by the addition of a small quantity of unsterilized cow’s milk, which probably supplied the missing ferment, if such were necessary, without materially altering the composition. With regard to sour milks, he thought that the points referred to by Mr. Richmond ought to be made widely known, as they indicated an easy method of102 THE ANALYST. ascertaining with certainty the composition of sour-milk samples. If a Lister-Babcock machine was used for determining the fat, a Kjeldahl determination could possibly be made on a fair average sample taken from the comparatively large quantity in the machine.Mr. HEHNER said that the remarks of Dr. Edmunds and Dr. Rideal, which raised some doubt as to the food value of sterilized milk, had a serious aspect in view of sanitary considerations. If there were not any very strong evidence that by sterilization some material damage was done to milk, such statements might do un- intentional harm, There was no chemical or physiological evidence whatever, as far as he was aware, that milk did contain any ferment necessary to digestion. Mr. Richmond had omitted to mention the fact that calcium citrate was deposited from milk on boiling. I n condensed unsweetened milks, a notable sediment of citrate existed ; and this deposition might perhaps be another means of distinguishing boiled from raw milk. The change in the rate at which the cream rose was a very interesting fact.Whatever the explanation might be, it seemed to him that the viscosity of the milk had become altered. He had thought of using the viscosity of the milk as a rapid means of dairy analysis ; but Mr. Richmond’s results seemed to show that this. would not be possible, except, perhaps, in the case of milks which it was certain had not been boiled. There were, other things being equal, two factors influencing the viscosity of milk-namely, the amount and size of the fat globules, and the amount of solids-not-fat. If the specific gravity and the viscosity, as measured by the rapidity of the flow through a narrow orifice, were determined, which could be done in a minute or two, some useful data might probably be obtained.Mr. C. G. MOOR, with reference to the question of the adulteration of ordinary milk with unsweetened condensed milk, remarked that there was only one brand of unsweetened condensed milk sold in London to any extent, which was of Italian manufacture, and contained much less fat than it should if rnade from whole milk, and it contained a large addition of borax or boric acid. Mr. BEVAN remarked that Mr. Richmond had mentioned only three abnormal samples, and desired to know whether they were the only ones he had met with during the year. He was interested in the President’s remarks as to the ash, which showed the very great importance of always determining this, and being guided by it in forming an opinion. With regard to the nitrate test, he had been under the impression that Mr.Richmond had some time ago made experiments in this connec- tion, and had found that nitrates might find their way through the medium of food into the milk in a perfectly normal manner. Mr. RICHMOND said that the detection of diluted condensed milk in ordinary milk had been considered of such irnportanco by the British Dairy Farmers’ Association, that some years ago that Association had offered a gold medal for the publication of a method. Within the time during which the offer held good no method was discovered, but Mr. Faber had since brought out an excellent, and perhaps the best, method, He (Mr. Richmond) and his colleague had also studied the subject, and they thought it might still have sufficient importance to be worthy of consideration.Some years ago he (Mr. Richmond) had read a paper on the discrimination between abnormal and adulterated milks, in which he pointed out that a high ash was charac-THE ANALYST. 103 teristic of abnormal milks, and it afforded him much gratification that this was con- firmed, as it had been, by the President and by Mr. Bevan. He might say that these three abnormal samples were the only ones that had come under his notice during the year. The question raised by Dr. Edmunds of the physiological effect which sterili- zation had upon milk was one of extreme importance, and one upon which it was hard to get reliable evidence. The opinions held and positive evidence adduced by medical men on this question were often absolutely contradictory; it was not one, however, which fell within the province of analysts.With regard to Dr. Rideal’s remarks on the difference between country and London milk in the matter of the rising of the cream, it certainly was a widely-known fact that milk taken warm from the cow, and set immediately, gave more cream than if it were cooled down to a sufficiently low temperature t o keep it for some hours, and not only was the quantity of cream larger, but the cream itself was much thicker. There had been one ferment described as present in milk, namely, the galactozymose of Bkchamp, but this observer was the only person who had met with it, and his observations had not yet received confirmation. They had purposely omitted any mention of calcium citrate. They had thought of making some remarks on this subject, but on considering the matter, and making ex- periments in connection with the estimation of citrates, they found that it was not an easy thing to do, and were unable to get any results of real value, so they thought it best not to fill the paper with points that could only be just touched upon. With regard to the viscosity of milk, he did not think that this factor was likely to be of much use for analytical purposes, as it involved caiculations of an extremely com- plicated character. The viscosity of milk was due to, first, the internal friction of the molecules of the aqueous portion, and, second, to the friction between the fat globules and tho serum, andvery small variations of conditions might and did affect the ratio of the separate effects of friction. The PRESIDENT said that the Society’s thanks were due to Mr. Richmond and Mr. Boseley for these papers. Even if there did not appear to be any immediate practical object in detecting the presence of sterilized milk, the results obtained were none the less interesting and valuable. The Society was a technical, but not altogether a utilitarian, Society, and always valued facts. Besides, even though the practical application of such facts might not be immediately apparent, there was always the possibility that they might ultimately prove useful.

ISSN:0003-2654    

DOI:10.1039/AN8972200098

出版商:RSC    

年代:1897

数据来源: RSC

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104 THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS FOOD AND DRUGS ANALYSIS. Distinction between Raw and Boiled Milk. I. Carcano. ( G o n z . di Ij'am. di Trieste, 1896, i., 275 ; through Chenz. Zeit. Rep, 1897, 46.)-The sample is warmed gently with a few drops of fairly fresh oil of turpentine and an alcoholic solution of guaiacum added. The appearance of the well-known blue colour shows that the milk has not been boiled, and vice versd. E. H, L. The Detection of Horseflesh in Sausages, etc. H. Bremer. (Forsch. Bey., 1897, iv., 1-8.)-The various methods which serve for the detection of horseflesh are based either on the glycogen reaction or on an examination of the fat (see ANALYST abstracts, xix., 24 ; xx., 95 and 252 ; and xxi., 231). The author gives a summary of the work of others in this direction, and then describes his process, which consists in an examination of the intra-muscular fat.The meat preparation, from which all visible fat has been removed, is minced in a sausage-machine, and heated for about an hour on the water-bath with water. The fat rising to the surface is poured away with the water, and the flesh, after having been washed several times with hot water, is dried at 100" C. for twelve hours, and extracted for several hours with a petroleum spirit of low boiling-point. Part of the intra-muscular fat thus obtained is taken for the determination of the iodine number, refractive index, and Reichert-Meissl number, The remainder is saponified, the excess of alkali neutralized with acetic acid, and the alcohol evaporated on the water bath.The soap is dissolved in hot water, a hot solution of zinc acetate (1 part to 2 parts of fat) added, and the zinc soap washed with hot water and alcohol, pressed between filter-paper, and extracted with about ten times its volume of water-free ether for fifteen to thirty minutes under a reflux condenser. After cooling, the solution is filtered into a weighed flask, the ether evaporated, and the iodine number of the residue determined. Every precaution must be taken to prevent access of air during filtration and drying. The subjoined table gives the results obtained by this method : I. 11. 111. IV. v. VI. vn. VIII. Iodine No. of Intra- Iodine KO. of Liquid muscular Fat. Patty Acids. Horseflesh sausage without bacon . . .... 75.8 108.1 Horseflesh sausage with about 6 per cent. of bacon ... ... I . . ... ... 74.0 104.1 Horseflesh cervelat sausage with about 22 per cent. of bacon, well smoked ... 53.7 92.4 Horseflesh cervelat sausage with about 25 Ordinary sausage with some bacon ... 57.6 94.2 Thuringian cervelat sausage with about 65 Mixture of I. and V. in equal parts ... 66.4 103.1 per cent. of bacon . e , ... ... 74.1 102.1 per cent. of pig's fat ... ... .." 64.3 95.8 Mixture of IV. and VI. in equal parts ... 65.2 99.5THE ANALYST. 105 It is stated that whenever horseflesh is present the petroleum spirit extract has a red to reddish-brown colour, and that even the liquid fatty acids have a more or less reddish-yellow shade. On the other hand, bull’s flesh gives a similar colour, so that too much reliance must not be placed on this fact, except as a confirmatory test, When, however, this is found to be the case, when at the same time glycogen is detected, and when the iodine number of the intra-muscular fat exceeds 65, and that of the liquid fatty acids is considerably over 95, there can be but little doubt as to the presence of horseflesh.C. A. M. Detection of Caramel in Wines-Possible Confusion with the Coal-tar Colours. A. J. Da Cruz Magalhaes. (Comptes rendus, cxxiii., No. 21 ; through Chem. News.)-The author found that a caramelized Portuguese liqueur wine responded to the general reactions of coal-tar colours : dyeing mordanted wool in presence of potassium sulphate ; forming in presence of lead subacetate an orange-yellow liquid, which yielded up its colouring matter to amyl alcohol, a similar reaction occurring with ammonia in excess, and turning orange-yellow when agitated with yellow mercury oxide.Identical results were obtained with another wine colored with pure caramel from ordinary sugar, as well as in the case of solutions of pure caramel. Caramels from pure dextrose (1) and saccharose (2) were also tested, with the following results : Treated with lead basic acetate and amyl alcohol : (1) No coloration ; (2) deep orange- y ellow. Supersaturated with ammonia and taken up with amyl alcohol : (1) Greenish- yellow ; (2) very deep orange-yellow coloration. Ether : (1) No coloration ; (2) orange yellow. Mordanted wool : (1) Dyed yellow ; (2) orange yellow. No alteration of the original colour of the solutions was produced by Caze- neuve’s test. c. s. Quantitative Examination of Crude Woody Fibre. Lebbin. (Arch. Hyg., 1897, xxviii., 212 ; through Chenz. Zeit. Rep., 1897, 45.)-This process depends on the fact that ammoniacal hydrogen peroxide dissolves starch and vegetable albumins, but leaves pure cellulose practically untouched. 3 to 5 grammes of the meal or bran are very finely powdered and boiled for half an hour in a large beaker with 100 C.C. of water; 50 C.C. of 20 per cent. hydrogen peroxide are next added, and the boiling continued for twenty minutes, while 15 C.C. of 5 per cent. ammonia are gradually dropped in. The whole is boiled for it further twenty minutes, thrown on a tared filter, and the insoluble matter washed with hot water, dried and weighed. From the residue the weight of ash must be deducted, and also 6-25 times the amount of nitrogen it contains, if there be much present. The process gives uniform results, and the solutions filter well. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN8972200104

出版商:RSC    

年代:1897

数据来源: RSC

摘要:

106 THE ANALYST. ORGANIC ANALYSIS. Test for Formaldehyde. I;. Kentmann. (Pharm. Gen. A m . , 1896, viii., 356 ; through Chenz. Zeit. Rep., 1896, 313.)-If the suspected liquid is floated on an equal volume of a solution of 0.1 gramme of morphine hydrochloride in 1 C.C. of strong sulphuric acid, a red violet colour is produced within a few minutes, provided the formalin exceeds one part per 6,000. F. H. L. Estimation of Furfuraldehyde by Means of Phloroglucinol. 1. C. Councler (Clzem. Zeit., 1897, xxi., 2) ; 2. C. Krauch (Zoc. cit., p. 29).-This is primarily a discussion on the suitability or otherwise of Merck's preparation, (' Phloroglucin. puriss. pro anal. (m,p., 210" C)," for the purpose indicated. On the authority of Kruger and Tollens, Krauch has stated in the last edition of his book, '' Die Prufuag der Chemischen Reagentien auf Reinheit," that it is sufficiently pure to be so employed ; but Councler holds that it varies greatly in composition, and often contains enough diresorcinol to vitiate the results.He therefore considers it necessary always to uw a preparation freed from this impurity by Skraup's method. The remainder of Councler's paper is also largely polemical, and deals with the modifications of his process, which have been suggested by Kriiger and Tollens (Zeits. nngezu. Chenz., 1896, 40), He maintains that it is preferable to wash the precipitate till free from chlorine, and then to dry it to constant weight, rather than to wash with 150 C.C. of water, and to dry at 100" for three or four hours only; and that it is better to add the phloroglucinol in the solid form, in order to keep the volume of liquid afi small as possible.He also discusses at some length the question of pre- cipitating the whole of the furfural distillate, or only an aliquot portion thereof, and decides that, in the majority of cases, the latter procedure suEces. F. H. L. Gravimetric Estimation of Sugar. G. Ambuhl. (Chem. Zeit., 1897, xxi., 137.)-The author recommends that the cuprous oxide produced in the Fehling- Allihn process should be dried for one hour at 98.5" C., and weighed as such, instead of being reduced to the metallic state. He presents an elaborate table, showing the results of the method when applied to forty-six samples of wine, honey, and diabetic urine. I n the case of wines, the figures are practically identical with those obtained by weighing the metal, being usually a trifle higher (maximum, +0.09; average, +0034 per cent.).With honey, the excess averages 0.23 per cent. on amounts of sugar varying from 57 to 69 per cent. ; and with urine containing 4.25 to 6-16 per cent. of sugar, the mean difference between the two processes is 0.10 per cent., but in this instance the suboxide was manifestly contaminated with organic substances, which suffer decomposition on ignition, F. H. L. A spontaneously Inverting Can e-sugar Solution. A. Lam. (Chem. -&it., 1897, xxi., 56.)-The author has recently examined a sample of English crude sugar which was suspected of adulteration, Immediately after solution it gave in Laurent'sTHE ANALYST, 107 polarimeter a, value of + 91.0, but in twenty-four hours this fell to 80 5, continuing to alter till after ten days its opticity was + 12.5, and after thirty days - 24.5 (at which point it remained constant).l'itrated with Fehling's solution after standing twenty- four hours, the sample appeared to contain 17 per cent. of reducing sugars (calculated as glucose) ; but on inverting it according to Clerget's method, the figure ( - 33.8 at 16.5" C.), taken in conjunction with the positive rotation of 91, showed that it actually contained 92 per cent. of true cane-sugar. Further investigation proved that the anomalous behaviour of the material was due to a rod-shaped micro-organism possessing the property of inverting faintly acid and saline solutions of sugar, but without influence on such as are neutral, alkaline, or free from salt.F. H. L. The Detection and Extraction of Citric and Malic Acids by Mcans of Quinine and Cinchonine. L. Lindet. (Bull. s'oc. chh., 1896, 11GO-1163.)- Citric and inalic acids iiiay be easily distinguished by the difference in solubility in methyl alcohol of their quinine and cinchonine compounds, and on this difference the author has based a process for extracting them from vegetable juices. Cold methyl alcohol (95 per cent.) dissolves only 0.3 per cent. of acid citrate of quinine and 3.3 per cent. of the neutral citrate, while the corresponding malates are soluble to the extent of about 8 per cent. The presence of malic acid interferes with the precipitation of the acid citrate of quinine, and when, in a mixture of the two acids, the quantity of malic acid is 25 per cent.of the quantity of citric acid, not more than 99 per cent. of the theoretical acid citrate of quinine is obtained. When the proportion of malic acid is increased to 50, 100, and 200 per cent., the quantities obtrtined respectively are 97, 94, and 83 per cent. Under the same conditions the acid oxalate of quinine (solubility 9.2 per cent.) and the neutral oxalate (solubility 8.2 per cent,) remain in solution, but t h a e also increme the solubility of the quinine citrate. Cinchonine dissolved in methyl alcohol precipitates inalic acid where quinine precipitates citric acid. The solubility of the acid malate of cinchouine is 2.5 per cent., but the other salts of cinchonine are so soluble that the precipitation can be considered as characteristic of malic acid.Tlie acid tartrate of cinchonine dissolves to the extent of 26 per cent., whilst the acid citrate, the acid oxalate, and the acid succinate only crystallize when their solution is evaporated to a syrupy consistency. The presence of tartaric, citric, oxalic, or succinic acids considerably increases the solubility of cinchonine malate in methyl alcohol. I n applying these reactions to the extraction of the acids from vegetable juices, the latter must be evaporated in vacuo, and the residue taken up in methyl alcohol (as concentrated as possible). Tartaric acid, if present, should be removed by adding alcohol and ether and precipitating with potash. The excess of potash is eliminated by precipitating all the acids with subacetate of lead, and afterwards liberating them by sulphuretted hydrogen.This is the method to be adopted when the juice contains much sugar or foreign matter. Tannin must also be removed by absorption with animal matter, such as catgut. The concentrated acids are dissolved in methyl aIcohol, and to a definite quantity108 THE ANALYST. of the solution, containing about 2.5 per cent. of acid, quinine as a powder is added little by little, until after shaking for some time a crystalline precipitate is produced. The quantity of quinine added must not exceed 160 to 170 per cent. of the quantity of supposed citric acid, or the more soluble neutral citrate of quinine will be produced. When the proportion of quinine has been established, the main solution is treated with the calculated amount.After standing for twenty-four hours, the liquid is filtered, and the operation repeated on the mother liquor. When no precipitate is obtained-that is, when citric acid is absent-rnalic acid is tested for and extracted in the same way, the maximum amount of cinchonine to be added being 140 to 150 per cent. of the supposed quantity of malic acid. Where the two acids are present together, cinchonine is added to the liquid after precipitation with quinine, since an excess of the latter does not interfere with the precipitation of cinchonine malate. The acids are easily recovered from the alkaloidal salts by adding ammonia to their aqueous solution, filtering from the alkaloids, precipitating the acids with sub- acetate of lead, and decomposing the precipitate with sulphuretted hydrogen ; or the acid may be removed by barium hydrate, the precipitate, after drying, being washed with alcohol, and finally decomposed with sulphuric acid.I n this way the author has extracted the citric acid from the juice of lemons, gooseberries, strawberries, raspberries, and tomatoes, and the malic acid from that of cherries and grapes. C. A. M. The Iodine Number of Cocoa-Butter. D. Holde. (Zeits. anal. Chem., 1897, xxxvi., 163, 164.)-In an abstract of the work of De Negri and Fabris, ‘( Gli OK,” which was published by the author in the Zeits. anal. Chem., xxxiii., 570, the higher limit for the iodine number of cocoa-butter was given as 51. This high value led Strohl to examine specimens of all the different varieties of the fat (ANALYST, xxi., 231), and the highest figure he could obtain was 41.7.Then Filsinger published a note (ANALYST, xxii., 46), in which he suggested that Strohl’s higher limit (41.7) might have been due to the presence of free fatty acids, since in his work with Henking in 1889 he had not found a higher value than 37.5. With regard to this opinion, the author points out that Strohl obtained an iodine number of 39.8 to 40.4 with specimens of fresh cocoa-butter, and that, as he himself has found in the case of fluid fats, and as Spiith (ANALYST, xxii., 46) showed in the case of lard, an increase of acidity is accompanied hy a decrease in the iodine number. These various communi- cations have led the author to refer to the original paper of Hiibl, from whom De Negri and Fabris took their figures for cocoa-butter, and he now finds that those chemists wrongly transcribed the value 51, which in Hiibl’s paper is 34.C. A. M. Estimation of Rosin in Fats and Soaps. J. Landin. (Clzenz. Zeit., 1897, xxi., 25.)-In the hands of the present author, Twitchell’s process is perfectly satisfactory ; but he prefers to use petroleum spirit instead of ether as the solvent for the resin acids, and also to determine them gravimetrically, owing to the uncertaintyTHE ANALYST. 109 about their true molecular weight. As regards Cornettie's process (ANALYST, xxi., 260), sodium resinate is not really soluble in saturated sodium chloride. If an alkaline solution of rosin containing 2 per cent. of colophony is treated gradually with this liquid, the first precipitate disappears, until an equal volume of salt solution has been added, but further additions again increase the amount of insoluble matter.The method is, therefore, not reliable. F. H. L. Valuation of Glue by Viscosimetry. J. Fels. (Chent. Zed, 1897, xxi., 56 and70.)--None of the methods hitherto proposed for testing glue can be deemed trustworthy ; and even Stelling's (ANALYST, xxi., 239) is inexact. An exception must perhap8 be made in favour of Lipowitz's plan of judging the material according to the consistency of the jelly it yields on treatment with a definite amount of water ; but, still, this only gives comparative results. The present investigator holds that by determining the viscosity of a glue solution in Engler's apparatus the actual adhesive power of the substance can be gauged, and, moreover, the figures obtained may be expressed in an absolute form.The process has been in use for a year, and has proved quite satisfactory. The sample is rubbed to powder, and the moisture estimated by drying it at 100" for two hours: 100 grammes are soaked in about 400 C.C. of cold water for twenty-four hours, melted on the water-bath, and the amount of liquid so adjusted that the solution contains 15 per cent. of dry glue. It is then tested in the viscosi- meter at 30" C., the time taken for an equal volume (500 c.c.) of water to run out being considered as unity. Treated in this way, five samples gave the figures : 1.36, 1-60' 1.65, 1-91, and 2.21; and it was found that the values expressed the same differences in quality as were deduced from an examination of the corresponding jellies according to Lipowitz's method. F. H. L. Mineral Constituents of the Water-Melon. G . F. Pagne. (JOZLY. An~ei.. Chein. Xoc., 1896, xviii., 1061-1063.)-Two medium-sized water-melons cut up and mixed together were found to contain just 9 per cent. of pure ash calculated as free from carbonic acid. The composition of the ash was : Sulphur trioxide ... ... I .. ... ... Calcium oxide ... ... ... ... ... Magnesium oxide ... ... ... ... ... Potassium oxide ... ... ... ... ... Sodium oxide ... ... ... ... ... Silicon dioxide ... ... ... ... ... Phosphorus pentoxide ... ... ... ... Chlorine ... ... ... ... ... Iron sesquioxide ... ... ... ... ... ... Per cent. 4-41 5.54 6.74 61.18 4.31 2.15 10.25 4.94 0.48 100.00 C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN8972200106

出版商:RSC    

年代:1897

数据来源: RSC