摘要:

7P.H-E ANALYST. JANUARY, 1895. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS, THE usual Monthly Meeting of this Society was held on December 5th at the rooms of the Chemical Society, Burlington House. I n the absence of the President, Mr. Otto Hehner took the chair. The minutes of the last meeting were read and confirmed. H. S. Shorthouse, Pershore Road, Birmingham, was proposed for election as The following gentlemen were duly elected : as member, Raymond ROSS, Fort On the proposal of Mr. Allen, seconded by Mr. Smetham, Mr. B. Kitto and Mr. Richmond then read the following paper : member. Royal, Worcester ; as associates, C. A. Mitchell, M.A., and J. Lewin. Dr. F. L. Teed were appointed auditors. NOTE ON RECKNAGEL’S PHENOMENON. BY H. DROOP RICHMOND. RECKNAGEL first observed that the specific gravity of milk, when taken as soon as possible after milking, was lower than observations on the same milk at later periods.He attributed this to a swelling of the casein, though it should be more properly a contraction of the casein. Vieth (ANALYST, xiv., 69) made a series of experiments, and found a rise in twenty-four hours varying from 0.001 to 0.002, and averaging 0.0013, and confirmed Recknagel’s statement completely. Bourcart (BUZZ. Xoc. Chim. [3], i., 24) has also made the same observation. Pappel and I (Joz~rrz. Chem. Soc., lvii., 754) have observed in the milk of the gamoose an average rise of 0.0007 in twenty-four hours, and concluded that the rise was not so great in the milk of the gamoose as in that of the cow. The maximum rise observed in twenty-four hours was 0*0009, and the minimum 0.0003.I n one sample examined later than the others, I found a decrease in specific gravity, the figures being 1-0351 after two hours, and 1.0345 after twenty-four hours. The duplicate determinations with different pynometers only differed by 0.00002, and I do not think that experimental error was the cause of the difference. The American Association of Official Agricultural Analysts proposed to touch upon this subject for this year, but their report has not yet reached me. In private communications both Dr. Babcock and Dr. Farrington have informed me that they have either observed no rise or a very slight one.2 THE ANALYST. - ~- - __- - -. I t appeared to me desirable to further examine the question, and to see if the phenomenon were general, or, if not, under what circumstances it took place, and to determine to what change in the constituents it was due.The following reasons are possible : (i.) When fresh milk it drawn from the udder, minute air-bubbles form, and are (ii.) Milk-sugar in the udder may be formed as anhydrous sugar, and the rise (iii.) A change in the albumiuoid, analogous to that of fibrin, may occur; in this (iv.) The fat globules may contract very slowly as the milk cools, owing to their (r.) A chemical change, such as that between aldehyde and water (cf. Perkin, The reasons may be examined as follows : (i.) This reason is not very likely, as microscopic examination with a high power fails to show air-bubbles after about one hour after milking ; froth pro- duced by artificial means disappears in about one hour or less.(ii.) This is also most improbable, as milk-sugar solutions do not change in density during chemical change indicated by a rapid variation in specific rotation ; nor does the milk-sugar, estimated by the polariscope, differ when estimated soon after milking, and after the lapse of some hours, though a rise in the specific gravity is taking place. (3.) Salicylic acid has an .inhibitive action on many enzymes ; preliminary experiments have given indications of the rise being hindered by salicylic acid. (iv.) Is also improbable, as in this case milks rich in fat should show more rise than poor milks; experiment does not bear this out. (v.) Chemical change should follow Harcourt and Esson’s laws.Data are not sufficiently numerous to ascertain whether the rise in specific gravity does so, but there are indications that, though in fair agreement, the rise is not wholly in accordance with them. O’Sullivan and Tompson (Jouwz. C h e n ~ SOC., lvii., 865) have shown that an enzyme, invertase, also follows to a great extent Harcourt and Esson’s laws, and that therefore there is no sharp distinction between chemical and enzymic action. It seems probable, therefore, that Recknagel’s explanation that a change in the casein occurB is correct, and that this is due to an enzyme (possibly the enzyme which causes the change within the udder); it would appear from this that milk is still a living tissue after secretion. I t is probable, then, that fore-milk (i,e, milk that has remained ready formed for some time within the udder) mill show much less rise than the later portions (which are drawn away as secreted).Preliminary experi- ments have shown indications of this being the case. I have shown that for two successive years practically the same differences have occurred between the fat calculated and that estimated at different periods of the year (ANALYST, xix., 82); though I hesitated to place too much reliance suspended in the milk for a long period. may be due to a hydration. case it would probably be enzymic. being surrounded by a layer of badly conducting material. Jozmz.. Chem. Soc., li., p. 817), may take place.THE ANALYST, 3 on the apparent concordance, it is interesting to bear this in mind when studying the periodical variations of the Recknagel phenomenon.There is some evidence already that the rise in specific gravity takes place to a much greater extent in the autumn and winter than in the spring and summer, and that the year can be divided into periods corresponding to those indicated by the agreement of the calculated fat. Much systematic work will, however, be necessary to establish the views that I have indicated, I reserve quantitative details for a later communication, but I may say that while, in some cases, the rise has been as great as that found by Recknagel and Vieth, in others it has been absolutely nil. DISCUSSION. Mr. Alfred Smetham said that in a series of milk analyses which he had con- ducted in connection with some experiments in Cheshire cheese-making, there had occurred considerable differences between the percentages of fat as calculated from the specific gravities (which were taken at the farm where the cheese was being made) and the amounts arrived at from determinations made in his laboratory by the Adam’s process.These differences were so marked as to cause him to distrust the hydrometer with which, in the first instance, the specific gravities were taken; but the instrument, when tested, was found to be quite correct; and, moreover, the discrepancies still remained when a balance had been substituted for the hydrometer. A rise in the specific gravities of the samples seemed to have taken place during the time which elapsed between the measurements at the farm (which circumstances rendered it necessary to make within half an hour of milking) and the analyses made in the laboratory.After careful observation and consideration, he came to the conclusion that this must be due to the gas, as of the milk and the air bubbles mechanically carried into the milk during the operation of milking, which would disperse after some lapse of time. The experiments extended over several months of two successive yews, but were not continuous, taking place in the late summer and autumn only of each year. Dr. Sykes said he thought that enzymic action might possibly account for the phenomenon under consideration. I t was now a well-ascertained fact that the peptonization of proteids was a process of hydrolysis, and this would no doubt be accompanied by a rise in the specific gravity of the solution of the proteid, just as a solution of cane-sugar, owing to fixation of water by the sugar molecule, becomes specifically heavier under the action of the enzyme invertase. In the absence of the respective authors, Dr. Dyer read a paper entitled (‘ Note on Woody Fibre Determination,” by A. P. Aitken, D.Sc. ; also Note on a Sample of Red Water,” by W. F. Lowe; and the three following papers :

ISSN:0003-2654    

DOI:10.1039/AN8952000001

出版商:RSC    

年代:1895

数据来源: RSC

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THE ANALYST. 3 THE ANALYSIS OF SODIUM PEROXIDE. SHORTLY after sodium peroxide became an article of commerce, I had occasion to make a full analysis of a sample of it, which led to some observations of interest. As I am not aware that a really accuratg, rapid method for the assay of this article has been published, I venture to bring the results of iny experiments before the Society. BY L. ARCHBUTT, m.c.4 TEE ANALYST. ~- -- -~ . - - - -. - _- - __ __ - . __ . ._ - - . The sample of the peroxide which I examined was taken from a full 14-lb. canister fresh from the inakers' works. A portion of it was transferred to a stoppered tube, and all the weighings were made by taking some from the tube, which was im- mediately re-stoppered and the loss of weight ascertained. 1 Oxygen obtained in Weight taken c.c., reduced to oa and Oxygen obtained in gramrnes. 7so mm. (dry). 1 in grammes. Estimation of Soda (Na,O). About 0.8 gramme was accurately weighed, dissolved pose the peroxide, cooled, tinted with methyl orange, sulphuric acid. A few drops more of the acid were evaporated to dryness in a tared platinum dish, and ignition. From the weight obtained there was deducted Oxygen obtained per cent., assuming half came from the KMnO,. in water, boiled to decomd and titrated with normal then added, the solution the residue weighed after the weight of the alumina and iron oxide found by another experiment, and the difference was calculated to Na,O. Two experiments gave : Na,@ by titration, 78.60 and 78.65. Mean ... ... 78-63 Na,@ weighed as Na,SO,, 78.72 and 78.69.Nean ... 78-70 General Mean ... ... ... 78.66 Estimation of Alzi?niiza and Iron Oxide. About 2 grammes were taken, dissolved in water, acidified with hydrochloric acid, and precipitated by ammonia in slight excess : Per Cent. Weight of ignited ppt. ... ... 0.49 Estimation of Oxygen existing as Peroxide. First Method tried.-From 0.2 to 0.25 gramme of the sample was weighed into a small dry tube closed at one end, which was then placed in the flask attached to a Lunge nitrometer. The flask contained a small volume of potassium permanganate solution acidified with sulphuric acid, and after the whole had acquired the tem- perature of the room, the inercury was levelled, and then the peroxide and the permanganate solution were brought into contact.0.1974 0.2434 0.2457 0.2447 _I__ __ 29.78 37.28 38.56 38.47 ~- - _ _ 0.0426 0.0533 0.0551 0.0550 ~ ~ 10.79 10.95 11.22 11.24 Evidently the decomposition was only partially effected in accordance with the equation : 5Na,02 + 2KMn0, + 8H2S0,= 5Na,SO, + K,SO, + 2MnS0, + 8H,O + 50,. Second Method tried.-About 0.1 gramme was dissolved in cold water previously mixed with some dilute sulphuric acid, and the solution was titrated with decinormal permanganate. Three experiments gave 18.4, 18.3, and 17.8 per cent. of oxygen.THE ANALYST. 5 There was a slight loss of oxygen at the moment of contact between the peroxide and the acidified water. A larger quantity, 1*0019 grammes, was dissolved in acidified water, diluted to 1 litre, and 100 C.C. titrated. Two experiments gave only 17.45 per cent.of oxygen. Thi.;r.d Method tried.--An attempt to decompose the peroxide in the nitrometer with water alone was not successful, decoinposition being much too slow and incom- plete. But a trace of cobalt nitrate previously added to the water was found to be all that was required to effect rapid aud complete decomposition. The peroxide was weighed into the small tube, and into the flask were placed about 5 C.C. of water and one small drop of cobalt nitrate solution. Three experiments were made, and gave the following results : Oxygen obtained in 1 Weight taken c.c., reduced to oo and 1 Oxygen obtained I Oxygen obtained in grammes. , 760 mm. (dry). in grammes. i per cent. 0.2499 0.2472 , 0.2537 I ___.. __ 32.40 31.91 32.94 - . - - - .- 0.0463 0.0456 0-0471 . 18.54 18-46 18-57 The mean of these results-via,, 18-52 per cent.-was accepted. They show that decomposition by water in the nitrometer flask in the presence of a milligramme or two of cobalt sesquioxide is the most accurate, as well as the simplest, method for the assay of sodium peroxide. I t would be more accurate to add precipitated cobalt sesquioxide than cobalt nitrate, as obviously a trace of oxygen is used up in oxidizing the cobaltous oxide. My result may, therefore, be a trifle too low ; but, taking it as practically correct, the composition of the sample works out as follows : Constituents found. Per cent, Na,O ... ... ... 78.66 A1,0, and Fe,O, ... ... 0.49 0 ... ... ... ... 18.52 Calculated composition. Per cent, Na,O, ... ... .., 90.41 NaOH ... . . . . . . . 8.73 A120, and Fe,O, ... ... 0.49 - 99.63 This analysis does not take into account a very little carbonate, a trace of chloride, a minute trace of sulphate, and a few particles of unoxidized sodium which the sample contained. No other impurity was detected. DISCUSSION. Dr. Duprb said that the analysis of sodium peroxide was a very unsatisfactory All the processes he had tried were almost impossible to He had not, however, tried the cobalt process, but operation to perform. conduct without loss of oxygen. thought it would be a sensible improvement.

ISSN:0003-2654    

DOI:10.1039/AN8952000003

出版商:RSC    

年代:1895

数据来源: RSC

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6 THE AN BLY ST. NOTE ON GLADDING’S PROCESS FOR THE DETERMINATION O F RESIN IN SOAP. BY L. ARCHBUTT, F.I.C. LEWHOWITSCH’S destructive criticism of all the methods which have been proposed for the determination of resin in soaps* leaves Gladding’s process in this position : that, in the absence of a really reliable process, it will continue to be used on account of its simplicity, especially in cases where the soap has been made from a known fat. I wish to direct attention to a source of error which is one cause of erroneous rasults. I n his original paper, ‘‘ On the Quantitative Separation of Resin from Fats,”? Gladding directs that 0.5 gramme of the mixed fatty and resin acids is to be dissolved in 20 C.C. of 95 per cent. alcohol. The solution, mixed with one drop of phenol- phthalein, is to be treated with a saturated alcoholic solution of caustic potash, added drop by drop until the deep-red colour characteristic of alkalinity is obtained, after which (‘ one or two additional drops of the potash solution are added, and the flask is placed ou the water-oven and kept at the temperature of boiliug alcohol for ten minutes to ensure the saponification of the last traces of fat.” I n the analysis of soap, “one grnmme of the soap in thin shavings is dissolved in the alcohol, and treated in every way as above. Particular care is paid to the saponification, as above directed, in order to make certain that no trace of unsaponified fat is left.” I n my laboratory the above directions have always been carried out, but I have long been sceptical as to the value of the last part of the process, by which the absence of unsaponified fat is supposed to be ensured.On not a few occasions the resin acids extracted from soaps have been more or less soft, instead of hard and brittle. But my observations have not gone beyond this, until a few days ago, when two eQmples of palm soap were being tested side by side ; from one the resin obtained was quite hard and brittle, and from the other soft. As the soft resin was several units per cent. higher than the hard resin, and the question under investigation related to the relative amounts of resin in the two soaps, it became necessary to make further experiments. So 10 grammes of the soap yielding the soft resin were dissolved in alcohol, and boiled down in a basin with 1 C.C.of a 50 per cent. caustic soda solution. The soap, thus thoroughly freed from unsaponified oil, was dissolved in hot water, the solution well boiled, and decomposed with dilute sulphuric acid. A suitable quantity of the washed and dried fatty and resin acids was weighed, dissolved in alcohol, neutralized with potash, and the resin acids separated as usual. They mere now quite hard and brittle. The results numerically were as follow : Resin Acids. First experiment . . . ... . . . 25.18 per cent, soft. Second ,, ... ... ... 21.07 ,, hard and brittle. The crude fatty and resin acids obtained from a soap in the ordinary course of analysis would contain the unsaponified oil, and would be no better to work upon than the soap itself. The soap must, therefore, either be boiled with a sufficient * SOC.of Chem Iitil., 1893, pp. 503-508. t Chem. News, v d . xlv., p. 160.THE ANALYST. 7 excess of alkali to saponify undecomposed fat, or else the aqueous solution of the soap must be shaken with ether to remove unsaponified oil, and the acids liberated from the purified soap solution used for the resin estimation. The latter method would be preferable, as it would remove any cholesterol or other unsaponifiable matter as well as the unsaponified oil. DISCUSSION. Mr. Allen said that he had found it a great improvement to precede Gladding's process by a preliminary treatment of the soda soaps of the fatty and resin acids with ether-alcohol, as directed by Barfoed. This left the greater part of the fatty acids insoluble, and it became much easier to effect a separation of the resin acids from the residual fatty acids by Gladding's silver process.But of late he, Mr. Allen, had rather preferred Twitchell's process to Gladding's, even with the preliminary Barfoed treatment. This method consisted in passing hydrochloric acid gas through a solution of the fatty and resin acids in absolute alcohol, whereby the former sugered conver- sion into compound ethers or esters, while the resin acids were unaffected. On diluting the product with water, and adding petroleum spirit, the resin acids and esters were readily separated from the aqueous liquid containing the hydrochloric acid, and the amount of the resin acids ascertained approximately by titrating the washed layer with standard alkali.The results so obtained could be checked by separating the lower layer, acidulating it, and weighing the liberated resin acids. There was no doubt that the exact determination of resin in soap, etc., was a very difficult problem, which could not be regarded as completely solved, and any approach to greater simplicity or accuracy would be welcomed by those accustomed to make such determinations. Mr. Smetham said his experience of Gladding's method coincided with that of Mr. Allen. Where a large number of determinations had to be made, and something was known about the constituents of the soaps, the easiest and best plan was to compare the specific gravities of the resin and fatty acids with the specific gravities of standards made up of known quantities o€ resin and fatty acids from various sources, the specific gravities being taken at 100" C. I n this way the percentages of resin and fatty acids could be determined with sufficient accuracy for manufacturing and commercial purposes. If the sources of the fatty acids were not known, deter- minations of the saponification equivalent and of the iodine absorption would, as a rule, give sufficient information to enable such cases to be dealt with.

ISSN:0003-2654    

DOI:10.1039/AN8952000006

出版商:RSC    

年代:1895

数据来源: RSC

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THE ANALYST. 7 THE COMPOSITION OF MILK, AND THE CONDITIONS AFFECTING IT, AS SHOWN BY BELL’S ANALYSES. BY J. F. LIVERSEEGE, F.I.C. DR. BELL’S analyses of milk, dated August 15, 1893, have several times been quoted in police-court proceedings, and it seemed worth while to examine them in detail, t o ascertain how far they can be quoted in opposition to this society’s standard, particularly as the report accompanying them is so meagre.8 THE ANALYST. I Solids per Cent. (Bell). I Sp. Gr. __________- -- - - -___ Averages. Not-Fat. ~ Fat. 1 Total. ---- PI__---_____ 273 Cows ... ... ... 1-z 8.908 i 3.991 i 12.899 55 Dairies ... ... ... 1031.9 8.96 i 4.00 I 12-96 The average composition is shown by the following table : Calculated. ___ - S.-n.-F. Fat. 8.86 4-03 8.80 4.16 __- - I 12.90 1 8.8 *..I - Dr. Vieth ... ... Tot.al Solids. 4.1 Under 11.5 % 11.5 to 11.99 12.0 ,) 12.49 12.5 ,, 12.99 13 ,, 13.99 14 ,, 14.99 15 and over i 6 ,, 11 21 ,, 38 25 ,, 45 1 $ 1 2 55 100 - -- 55 DAIRIES. 71 ,, 26 28 ,, 10 33 Y , 95 I , 273 100 -_ -- = 0 % 7 11 35 42 5 0 100 -- Fat. Under 2.75 % 2.76 to 2.99 3.0 ,, 3.19 3.2 ,, 5.49 3.5 ,, 3.99 4 ,, 4.99 5 and over Bell. 0 Milks = 0 % 2 Bell. 1 Calculated. Solids-not-Fat. Under 8 % 8.0 to 8.29 8.3 ,) 8-49 8.5 ,, 8-69 8.7 ,, 8.99 9.0 ,) 9.49 9.5 and over ’ 3 Milks = 1 % 10 9 , 4 260 ,, 95 Calculated. 7 Milks = 3 % 17 $ 9 7 40 ,, 15 209 ,, 75THE ANALYST. 9 Solids-not -Fat. 8.92 9-15 9-30 9.22 8.87 9.68 8.65 9-22 9.01 8.86 8.908 It will be seen that no dairy gave less than 11.5 per cent. of total solids, the lowest being 11.68 per cent.and 11.80 per cent., while the lowest single cows were 10.33 per cent., 11-19 per cent., 11921 per cent., and 11.35 per cent., the other three being more than 11.4 per cent. Among the dairies, the only one below 3 per cent. of fat is 2.89 per cent., which when calculated, gives 2.99 per cent. The two lowest single cows give 2-43 per cent., and calculate to 2.6 per cent. and 2.67 per cent. The seven milks with total solids under 11-5 per cent. have all less than 3 per cent. of iat. Two of the dairy milks give solids-not-fat under 8.5 per cent., viz., 8.4 per cent. and 8.48 per cent. ; but four of the calculated figures are below the standard, viz., 8.28 per cent., 8.33 per cent., 8.35 per cent., and 8.42 per cent. The two lowest single cows are 7.52 per cent.and 7.79 per cent., and the two lowest calculated are 7-52 per cent, and 7.66 per cent. I n all, 74 milks from single COWS are below the Society’s limits-10 being low in fat only, 61 in solids-not-fat only, and 3 in both; but in 37 cases there is a com- pensation in the other constituents, so that the total solids are 12 per cent. or over, while 26 more are within 0.2 per cent of the standard, leaving only 11 milks, or 4 per cent., that are much below the standard. an increase of what is called butter-fat of perhaps 0.2 per cent.” over the Bell process, but it is worth while noting that sometimes the calculated fat exceeds the figures given by 0-4 per cent. ; in other cases the calculated fat is lower-in one case as much as 0.26 per cent.As in each milk, the age, food, hour of milking, and time from calving are given, as well as the breed of the cows, and the quantity of milk yielded, I tried to find if, from these analyses, any general conclusion as to the effect of these factors on the quantity of the milk could be arrived at. It might be thought that these things do not concern the members of the Society, but as the public analyst may any time be cross-examined as to the effect of food, etc., I do not think any apology is needed. The following table gives the average composition and quantity of milk yielded by the cows of the various breeds, but it should be noticed that the number of samples in some cases is too small to be of much use. The milk from the North Devon cows is highest in solids-not-fa,t and lowest in fat, The Dutch cows give lowest total solids and solids-not-fat, while the Jersey milks are highest both in total solids and in fat.The cross-breeds give the greatest, and the Kerries the least yield of milk : I t has been stated that the coil process gives _ - Breed. Sussex ... Welsh ... Jersey ... Kerry ... North Devon Dutch ... Ayrshire ... Cross-breeds Shorthorns ... General Average Guernsey ... __. __ ____-- ... ... ... ... -.. ... ... ... ... ... - ... - Number of cows. 2 2 4 6 5 6 13 15 17 203 273 ~- .. ~ __ Fat. 3.39 4.40 5.16 5 *43 4.67 3.43 3.75 4.24 3.99 3.92 3 9 9 F - - ~~~ __ .~ Total Solids. ~~ ~- 12.31 13-55 1446 14.65 13.54 13.11 12.40 13.46 13.00 12-78 12.899 ___-_ Average Yield. Quarts. 7.5 4.2 4-1 3.7 2.7 3.8 5-3 4.6 5.6 5.3 __._ __ ~____10 THE ANALYST.Hours between milking : As there was such a difference i n the various breeds, it was deemed advisable to eliminate this factor and investigate the shorthorns only. I t is well known that morning milk is poorer than evening, and it has been suggested that this is due to the difference of time elapsing between milking. To test this, the facts with regard to each cow were copied on a strip of cardboard, and the strips sorted. For solids- not-fat they were divided into three classes-under 8.5 per cent., 8.5 per cent. to 9 per cent., and 9 per cent. and over-and each class subdivided into first meal and second meal, and the numbers in each class counted and calculated to percentages. Thus, 23 per cent. of the milks under 8.5 were first meal, and 77 per cent. second meal.The fats were similarly classified, and then both were arranged with regard to hours from last milking. Figures on the same horizontal line may be compared, but vertically each class adds up to 100 : 28 i 11 1 Solids-not-Fat. 60 , 4-4 36 , 5.1 , - /TJnder 8.5. First meal ... 1 23 Second meal ... j 77 - _- 3.5 to 8.99 29 71 29 41 16 14 9.0 & over 29 71 30 37 16 17 / This table shows that while 55 per cent. of the milks low in fat were first meal, only 5 per cent, of those rich in fat belong to this meal. Also that, while 11 per cent. of poor milk were 8 to 9 hours between milking, 60 per cent. of the milks high in fat were in this class, showing that the longer the time between milking, the larger will be the proportion of milks low in fat, a conclusion which is supported by the other figures.If, however, the solids-not-fat be examined, it will be seen that time makes practically no difference, but a longer interval has a slight tendency to decrease the proportion of poor milks. This shows that for the study of the effect of food on the amount of fat, etc., it is necessary to select either first or second meal cows, or the differences due to the meal would mask the smaller variations ; the second-meal class, being the larger (147 cows), was selected, but all shorthorns were taken for the solids-not-fat : * Number of cows small.11 Age 2 to 44 years 5 9 9 6 9 ' Yield 1 to 3J quarts 4 9 , 5 ?, 6 ? ? 7 9 ' 8 ? ' 10 9 , ' 1 to 6 weeks Time 7 ,, 12 ,, from ;+ ,, 6months 1 9 9 9 , I 10 months h- ovei Calving Percentage of cows fed on Hay ...... ... Mangolds or Swedes ... Brewers' or distillers' grains ... ... ... Linseed or cotton-seed cake ... ... ... Chaff or straw ... ... Meals (oat, pea, barley, etc.) ... ... ... Grass ... ... ... THE ANALYST. ~ _ _ ~ ~ __ Solids-not-Fat. Under 8.5. 11" 62 16 11 25 45 17 13 18 37 27 lo* 8" -- 20 22 21 25 25 18 15 3.5 to 8.99. 34 36 24 6 23 27 37 13 28 36 23 8 5 48 47 43 45 49 53 56 PO & over -- 32 46 22 0 28 31 27 14 30 16 30 16 8 -- 32 31 36 30 26 29 29 Jnder 3.5. 31 54 11" 4+ -- -- 19 39 23 19 15" 38 31 8* 8+ 17 16 14 16 17 19 19 33 39 19 9 22 41 30 7 28 33 28 6 5* ~- 55 55 50 62 64 62 56 .I_--_. *5 & over. 24 65 11 0 37 30 30 3 27 25 18 27 33c -- 28 29 36 22 19 19 25 With regard to age, it may be noted that cows five and six years old give a large proportion of the milks, and that no milks high in fat or solids-not-fat occur in milk from cows over eight years old.When the quantity of milk is under one gallon, the proportion of milks high in fat is increased, and when two gallons and over is yielded at a milking, there is a small proportion of rich milks. The milks given by cows for periods of less than seven weeks after calving have a small proportion poor both in fat and solids-not-fat, and those seven to nine months after calving are of a better quality, particularly in fat. With regard to the effects of food, the problem is very complicated, as the majority of cows are fed on from three to six different kinds. The figures given are the percentage of rich, medium, and poor milks yielded by cows fed on each food considered by itself-thus, out of 100 cows fed on hay, 20 gave milk that was low, 48 medium milk, and 32 milk high in solids-not-fat.Some of the cows were fed on grass only, and with regard to part of them it is remarked that the grass was very scarce. The very small variations appear to show that food by itself has not much effect on the composition of the milk if the cows are fairly fed, as these are sup- posed to be. The large proportion of good milks from cows fed on grains is notable. * Number of cows small.12 THE ANALYST. The one respect in which the information given about these milks is deficient, is that no date is stated, and as the time of the year exercises a marked effect on the composition of the milk, one feels that, as this could not be allowed for, the influence of season may have introduced some errors into the above results. To summarize what has been said, these analyses show (1) That, with four very slight exceptions, all the mixed milks are up to the Society’s standard. (2) That only 4 per cent. of the milks from the single cows would show signs of much adulteration, as judged by the Society’s standard, if allowance is made for excess of the other constituents. (3) That analyses by the Bell method may give from 0.40 less to 0.26 per cent. more than the calculated figures, (4) That the longer the time between milking, the lower will be the fat in milk. (5) That, with the exception of breed, the other conditions have much less effect on the proportion of poor milks.

ISSN:0003-2654    

DOI:10.1039/AN8952000007

出版商:RSC    

年代:1895

数据来源: RSC

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12 THE ANALYST. ON ROASTED CHICORY. BY E. G. CLAYTON. (Read at the Z e e t i n g , Octobey 29, 1894.) THE amount of sugar present in roasted chicory is very variously stated ; and in most cases, apparently, only the sugar before inversion has been estimated. The following figures, compiled from Allen’s ‘( Commercial Organic Analysis ” and other sources, represent the quantities of sugar mentioned by different observers ; and some other numbers are quoted in the table for comparison : TABLE I. Sugar before in- version (Glucose). Krauth* .. ... ... ... aassall{ ... ... Campbell I 2. :::I Konigt . . . ... ... Graham, Sten= ( :; ” * ... house, and 26.12 23.76 22.39 12.2 10.4 15-87 11.98 15.96 17.98 9.86 Sugar after inversion expressed a, Sucrose ?). 1 Proteids. Sugar. - j 6-38 - 6.64 43.57 - I - - Water.16.28 16.96 4.30 14.5 12-8 12.16 - Mineral Matter. 7 -16 8 *44 10.36 4.3 6.8 6.12 - - I - , - * Krauth’s figures (except for moisture) originally referred to the substance dried at loo”, but for the The number obtained by Kiinig, given in column 1, is merely stated to be “sugar,” and almost Above table they have been re-calculated. certainly refers to glucose only.THE ANALYST. 13 - _ _ _ _ - _ _ _ ~ I__. p__p_..- Had the proportions of sugar after inversion been also determined, it is probable that very considerable numbers would have replaced the blanks in columns 2 and 3 ; and in the light of some results about to be summarized, certain of the figures in column 1 are so high as to suggest the possibility that some of the samples contained added sugar.This is further indicated by the low proteids (column 4). Specimens of whole chicory root and (for comparison) dandelion root were carefully roasted and ground in the writer’s laboratory, and extracted with boiling water. The solutions were decolorized by treatment with lead acetate, filtered after the addition of sodium carbonate, and titrated, before and after inversion, with Fehling’s solution. A sample of commercially-roasted and ground chicory, purchased as pure, was similarly treated, with the exception that hot alcohol was in this case used, in place of water, for the extraction. The proportions of mineral matter were determined in the two laboratory samples, and are here stated, together with the other results : TABLE 11. ‘ Matter reducing Fehling’s solution before inversion Glucose).(expressed as - - __ ~- Chicory root Matter reducing 1 Matter reducing Fehling’s solution,Pehling’s solution after inversion (expressed as Glucose). Sucrose). I -___ __- Total (i.e., the gurea in columns and 3), expressed as Glucose 4 Sucrose. (roasted in laboratory) . . . Dandelion root (roasted in 19.28 25-07 27.69 1 5.66 , 14.34 13.62 I I I ____ ~ dineral matter. -I 5-18 4.05 - Sample 1 (coarse grains or nibs) ... Sample 2 (pow- der) ... ... Sample 3 (coarse grains or nibs) ... Sample 4 (pow- der) ... ... ~ _ _ _ _ _ It will be seen that the numbers for sugar before inversion (column 1) are considerably lower than the corresponding figures in the analyses previously cited. Some samples of roasted chicory, undoubtedly containing added saccharine matter, lately came into the writer’s hands, and yielded the following results on partial analysis : TABLE 111.Matter reduc ing Fehling’: solution befort inversion (ex pressed as Glucose). _- 16.66 12.00 13.53 9.24 I Matter reduc- ng Fehling’s iolution after nversion (ex- pressed as Glucose). Matter reduc ing Fehling’ solution afte inversion (ex pressed as Sucrose). 46.50 44.17 I 62.50 1 59.37 I 33.75 1 32.06 I !otal (i.e.3 th gurzs in cols and 3), ex. pressed as Glucose + Sucrose. 60.83 71.87 45.59 31-67 Pro teid s - - 8.19 9.31 Water. Mineral I matter. 1.71 6.2514 THE ANALYST. I Sample 3 (Grains). igar, expressed as Glucose. /- I t is obvious that these samples contained large proportions of foreign saccharine matter, if the number in Table II., representing the amount of sugar expressed as sucrose in the laboratory-roasted chicory root, be provisionally taken as a basis of calculation, The unusually small percentage of water found in the fourth sample is noteworthy ; and it will be observed also that, in spite of the presence of considerable amounts of sugar, the quantities of proteids in samples 3 and 4 are larger than the proportions quoted in Table I.-already alluded to as being markedly low. The intensity of the colour of the infusions led to some experiments as to the most suitable methods of extraction and decolorization ; a series of estimations of glucose and invert sugar being made, after various means of removing the colour had been employed.An opportunity, of which the writer gladly avails himself, here arises of acknowledging the very careful assistance in these sugar determinations willingly rendered him by Mr.Sidney B. Wright. The results obtained are collated in Table IV. TABLE IV. Sample 2 (Powder). Sample 1 (Grains). Sample 4 (Powder). ~- __ gar, expressed as Glucose. ugar, expressed as Glucose. - ugar, expressed as Glucose. - Infusion decolorized bY Before inver- siqn. 3efore I After nver- I inver- sion. sion. After inver- sion. After inver- sion. After inver- sion. Before inver- sion. 12.00 12.50 3efore nver - sion . - 13-53 Lead acetate only 16.66 15.79 46.50 44-21 9.24 23.61 Lead acetate only Lead acetate, fol- lowed by filtra- t i o n through animal charcoal Milk of lime only Lead acetate and milk of lime to- Lead acetate and milk of lime, followed by fil- tration through animal charcoal gether .. . ... j 15.00 1 43.07 7.14 47.40 I 0 14.28 - i - 0 I 18.75 From the above results of duplicate determinations in samples 1 and 2, it is clear that the difference, caused by using alcohol in place of water for the extraction of the sugar, is inconsiderable. As for the several processes used to decolorize the solutions, the results in the first of the four main columns of the table (all of which results were yielded by the same sample, No. 1, and are in this respect strictly comparable), show that filtration through animal charcoal, though removing someTHE ANALYST. 15 colouring matter which lead acetate had failed to precipitate, effected this at the expense of a small but perceptible reduction in the percentages of sugar.Milk of lime, alone, yielded a pale-tinted solution, but removed nearly one-half of the ‘( sugar before inversion.” The addition of lead acetate, followed immediately by milk of lime, resulted in a nearly colourless solution ; but practically all the glucose, and more than two-thirds of the ‘ I sugar after inversion,” had vanished. Confirmation of these results appeared in the numbers yielded by simples 3 and 4 (columns 3 and 4): after the use of lead acetate and milk of lime, followed by filtration through animal charcoal, far lower results were obtained than when lead acetate only had been employed. I n short, the use of milk of lime, alone or in conjunction with lead acetate, is quite inadmissible, as, perhaps, might have been anticipated; and the process of extraction with hot water, followed by simple decolorization with lead acetate, appears most suitable in the case of chicory.Filtration through animal charcoal may, in addition, be necessary in many instances, and the influence on the final results will not be very serious. A D D E N D U M . Since the above was written I have read the evidence on chicory given before the Food Products Committee, and I venture to quote a portion of it here. After Mr. Bannister’s remark, that “ there is a greater extractive got from chicory now than there used to be ten or fifteen years ago,” questions 866 and 867. followed : L L 866. I s that agreed among chemists, or is it owing to your improved methods of analysis ?-It is on account of the difference of growth, I believe, and not to im- proved methods of analysis.867. That the quality of chicory has improved ?-It contains more extractive matter, and is richer iiz szignr.” Italics are mine.] explanation of the greater richness in sugar and extractive matter be found, not in any difference of growth,” but in a frequent practice of such extraneous addition as that described in the above paper ? If roasted chicory be referre d to (and this is presumably the case), may not the APPARATUS FOR PRESERVING AND DELIVERING STANDARD SOLUTIONS. BY J. C. CHORLEY. (Read at the Neetilag, Nocember 7 , 1894,) THIS apparatus will be found useful for preserving and de- livering known volumes of such solutions as alcoholic potash, which are liable to contamination by exposure to air. The wash-bottle inserted in the large store-bottle is filled with a solution of caustic potash, and so also are the bulbs con- nected with the top of the pipette. By means of the two- way cock, this can be filled to overflowing, and a known quantity of the solution can be delivered by running off to a mark on the narrow part of the pipette.

ISSN:0003-2654    

DOI:10.1039/AN8952000012

出版商:RSC    

年代:1895

数据来源: RSC

摘要:

16 THE ANALYST. CONSTANT-LEVEL APPARATUS. BY J. C. CHORLEY. (Read at the Meeting, November 7, 1894.) THIS apparatus was designed for use in distillations where it is advisable to maintain a constant level of liquid in the distillation- flask. The small bulb at the end of the long thin tube floats on the surface of the liquid. Its upper end, which is ground, fits into the thickened part of the larger tube, and prevents the water contained in the large bulb from flowing into the flask. When, however, the level of the liquid falls, the upper end of the long thin tube drops away, and releases a small quantity of water. In this way the level is automatically maintained. The Composition of Honey-dew and the Influence of a Summer rich in Honey-dew on the Condition of Honey. (Zeit. fiir Anal.*CChemie, 1894, pp. 397-408).-Honey-dew obtained from maple leaves by solution in cold water, and subsequently decolorized by animal charcoal, had the following percentage composition : Dr. Ed. von Raumer. Dry substance ... ... ... ... ... Water ... ... ... ... ... ... ... Sugar in 100 C.C. dry substance direct ... ... inverted ... ... ... ?, 9 , 9 ) ,, inverted Dextrin after fermentation with yeast ... ... ? ? 9 , 9 , Polarization 10 grammes dry substance direct Ash ... Nitrogenous matter calculated as albumen I n the ash { !$f . * ' ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... I. 75.12 24.88 16.70 28.5 23.2" 21.4" 39.4 3.02 3-17 19.5 16-2 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. 11.84.08 15.92 17.70 28.60 22.90" 20.80" 2.86 - The sugar was estimated by the Soxhlet-Allihn method, and the quantity compared with that obtained by fermenting the honey with yeast, and calculating the amount of sugar from the yield of alcohol. This gave 10.7 per cent. more sugar than could be obtained by direct estimation. The author's explanation is that there is an inter- mediate product between sugar and dextrin which is capable of fermentation, but which does not readily reduce Fehling's solution. The method was also used as a check on the estimation of sugar in honey. From experiments with honey produced in 1893-a year noticeably rich in honey-dew-the following conclusions are arrived at : 1. All species of honey contain dextrin fermentable with difficulty.Some, in particular those derived from conifers, contain considerable quantities of unferment- able dextrin. Omitting the abnormal case of conifer honey, this large quantity canTHE ANALYST. 1 7 only be explained on the supposition that the honey has been mixed by the bees with honey-dew. An increase in the normal amount of mineral constituents and nitro- genous matter may also point to the same conclusion. 2. Direct dialysis of the honey by Hanle's method* is not advisable, since even after 40 to 50 hours sugar is left on the membrane ; and on the other hand dextrin has passed through. The difficulty is obviated by dialysing the fermentation products instead of the fresh honey. 3. The dextrins of honey-dew probably undergo some change in the honey-bag of the bee, so that their power of dialysis is increased.C. A. M. Zinc-bearing Spring Waters. W. F. Hillebrand. (Bulletin U.S. Geological Survey, No. 113. Report of Chemacal Work in 1891-92 ma! 1892-93).-Analyses are given of two spring waters from Missouri, both containing zinc sulphate as a natural constituent. The other 132.4 of Zn and 63.1 of Ca. A peculiarity in the waters was that, although some of the Ca existed as carbonate, this being shown by the excess of bases over C1 and SO,, yet all the CO, wasiexpelled by simply boiling the water. The amount of GO, obtained was 120.5 per million in the first water, and 110.0 per million in the second, and no more could be obtained by acidifying the waters. The explanation is that the CaCO, at a temperature near the boiling-point of the water reacts with the ZnSO,, forming CaSO,, zinc hydrate or a very basic sulphate, and CO,.A determination of the residue, by simply evaporating the water to dryness would therefore involve a serious error. One contained 120.5 parts of Zn and 61.1 of Ca per million. C. A. M. On the Estimation of Phosphoric Acid by titration of the Molybdic Pre- cipitate, B. W. Kilgore. (Jour. srner. Chem. Xoc., 1894, p ~ . 765-772.) - A summary of different processes is given. The author obtained good results in general by Pemberton's (ANALYST xix., p. 135) method, though high ones were not uncommon. The variations were found to be due to deposition of niolybdic acid from the molyb- date solution. By precipitation at a temperature of from 55" to 60" instead of at loo", and by the use of the official molybdate solution of the Association of Official Agricultural Chemists instead of the more dilute solution used by Pemberton, this error may be avoided. The results tabulated agree well with those obtained by gravimetric determination. The official molybdate solution is prepared by dissolving 100 grammes of molybdic acid in 417 C.C.of ammonia (sp. gr. 0.96) and pouring this into 1250 C.C. of HNO, (sp. gr. 1.20). C. A. M. A Comparison of Methods for the Determination of Starch, W. E. Stone. (Jour, Amer. Chem. Xoc., 1894, xvi., No. 11, pp. 726-733.) - A comparative examination of different methods of starch analysis proves that, while the ordinary methods give excellent results with pure starch, the results obtained with substances * Xeit.j%r Anal. Client., 33-99.18 THE ANALYST. ~ containing other carbohydrates are discordant. gums acting towards some reagents precisely like starch. This is due to the pentosans or The table gives the results obtained by the following five methods. 1. Xachsse’s Method.-From 3 to 5 gramines of the material are heated in the water-bath for three hours with 200 C.C. of water and 20 C.C. of concentrated HC1. The glucose formed is estimated by Fehling’s solution. According to Marker, this method gives too low results, owing to destruction of glucose by the long heating with the acid. 2. Guichads Method.-Three gramnies of the material are heated in the watez- bath for one hour with 100 C.C. 10 per cent. nitric acid, made up to 200 C.C. and polarized.3. Three grammes of the material are heated in the water-bath with 100 C.C. of saturated solution of oxalic acid for an hour, in order to bring the starch into solution. The liquid is cooled, made up to 200 C.C. with 10 per cent. nitric acid, and heated in the water-bath for another hour. 4. Baudry’s Method-A normal weight, 5.376, is adopted for the Laurent polari- meter. This weight, or some multiple of it, is placed in a 200 C.C. flask, with 100 C.C. of water, 0.4 to 0.5 of salicylic acid added, and heated in the water-bath for half an hour. The contents of the flask are made up to within 20 C.C. of the mark with hot water, rapidly cooled, a few drops of ammonia added to clarify, filled up to the mark, filtered, and polarized in a 400 inm. tube. The readings are calculated to glucose.The solution is then polarized. 5 . A~both’s Nethod.-See ANALYST, vol. xii., p. 138. _ _ _ _ ~. Materials. I 1. Potato starch ... ... I 85.75 1 85.5 I 85.75 85-47 2. Dried potato ... ... 3. Wheat flour ... ...I 4. Corn meal ... ... ... 5. Wheat bran ... ... I 6. Hay ... ... ... . ..I 8. Cotton-seed meal . . . 9. Mixture of starch, sugar, and dextrin ... 1 I I I I 7. Wheat rniddlings ... ... _____ _-- 70.92 77.69 73-24, 65.86 3.48 30.00 4-15 9.58 69.79 70.65 66.81 40.25 19.10 63-09 * - 21.00 1 68.53 ‘ 65-29 70.55 38.68 ~ 19.10 ‘ 60.24 I -* 24.08 - ~ _ - - -- Yrecipi ta- tion by Ba(OH),. 85.58 64.25 59-76 62-11 70.77 66-47 60.44 54.65 33.99 -____ The potato-starch, but for moisture and cellulose, was ‘‘ pure.” The following experiment proves that the pentosans behave like starch.Each mode gave credit for the entire amount of real starch present. Xylan, free from other carbohydrate, was obtained from wheat straw. One gramme was heated for thirty minutes with 50 C.C. of water and 4 C.C. of strong HCI. The neutralized solution was made up to 100 C.C. Of this, 6.7 C.C. were required to reduce 10 C.C. of Fehling’s solution, a quantity equivalent to 67.16 per cent, of starch. The other methods gave similar results, with the exception of the salicylic acid method, which was found not to be applicable. * These solutions were hvo-rotary.THE ANALYST. 19 ~ The author, therefore, concludes that no method based on the foregoing principles is suitable for accurate work on grains or forage material. He suggests the use of some method by which the starch may be brought into solution without other carbohydrates, e.g., by means of diastase or malt infusion. The weighed material, after being made into a paste with boiling water, is cooled to 65", a small quantity of malt infusion added, and the temperature maintained at from 60" to 65" for half an hour.After the starch reaction has disappeared, the solution is filtered, the residue well washed, and the filtrate, after warming with a few C.C. of acid and then neutralizing, is made up to definite volume and titrated. The preliminary ex- periments cited indicate that the pentosans and siniilar bodies are not affected by diastase. C. A. M. ~- A Method for Determining Calcium Oxide in Quicklime. W. E. Stone and F. C. Scheuch.(Jozu. Anter. Clzenz. Xoc., 1894, xvi., No. 11, pp. 721-725.)- Since the value of quicklime depends on the quantity of CaO present, a method for determining this is proposed, which is based on the fact that the alkaline earths form definite compounds with sucrose. With CaO at least three are known, containing respectively one, two, and three molecules of CaO to one of sucrose, the two first being formed by dissolving CaO in the cold in a sucrose solution, while the third is precipitated on warming the solution. The preliminary experiments cited confirm Lamy's* observation that the solu- bility of CaO in sucrose solution varies inversely as the temperature, and prove that not less than 150 C.C. of a 10 per cent. sucrose solution are required to dissolve the CaO in one gramme of quicklime.Other ordinary constituents of quicklime, such as iron, alumina, magnesia, silica, and calcium carbonate are either quite insoluble in the sucrose solution, or soluble only to an inappreciable extent. One grainme of magnesia, after being shaken with 150 C.C. of sucrose solution, showed only 0.001 gramme of MgO in the clear filtrate. The following is the method adopted: One gramme of the finely-powdered substance is shaken for twenty minutes with 150 C.C. of 10 per cent. sucrose solution, the liquid filtered, and the clear solution titrated with standard HCl, half an hour being sufficient for the whole operation. Test samples of quicklime, containing very little CaCO,, were analysed by this method, and the results compared with those obtained in the usual way by precipitation as calcium oxalate.Per cent. CnO by grsvimetric method. ~ ___- - 93-00 92.28 93.10 95.90 87.70 92.30 Sample. 1. 2. 3. 4. 5. 6. _- -. Variation of volumetric method. - I - ~~ -0.88 -0.38 -0.95 -0.89 -0.40 -0.60 Quicklime taken. Grammes. 1.020 1.090 1.006 1,108 1.023 1.232 Of lo per cent. sucrost solution taken. - Per cent. CaO by titration method. __- __ 92-12 91-90 92-15 95.01 87-30 91-70 _ _ _ _ - ~ - - 150 150 150 150 150 150 The small quantity of CaCO, present would account for the discrepancy between the gravimetric and the sucrose methods. C. A. If. * La .sucrerie iiitligene et coloxiale, 11-19.20 THE ANALYST. Method for obtaining Pure White Magnesium Pyrophosphate in the Citrate Method. (Zezt. fiir afzgewafzd.Chem., 1894, Heft 22, pp. 678, 679.) I n the estimation of phosphoric acid by the citrate method, it is often almost im- possible to obtain the precipitate perfectly white even after long-continued ignition. This may be remedied by the addition of ammonium sulphate (5 grammes) before precipitating with the magnesia mixture. When heated for five minutes over a strong flame, the precipitate becomes perfectly white. Any precipitate of calcium sulphate formed by adding the ammonium sulphate may be ignored, since CaSO, is readily soluble in ammonium citrate. Dr. Hugo Neubauer. C. A. M. A New Method of Estimating Milk-fat. Dr. P. Fernandez-Krug and Dr. W. Hampe. (Zed. fiir angezuand. Chemie, 1894, Heft 22, pp. 683-687.)-1n this process a measured volume of the milk is mixed with a finely-divided mineral sub- stance, and the water removed by adding another finely-powdered niaterial which combines with it without affecting the milk-fat.The dried mass is shaken out with ether, and the dissolved fat estimated by evaporation of a definite portion of the solution. The following are the details of the actual estimation : About 7.5 grammes of washed and dried kaolin are introduced into a nickel basin holding about 200 c.c., and made into a creamy paste with 5 C.C. of the milk. This is then well mixed with about 5 grammes of finely-powdered anhydrous sodium sulphate, which combines with the water in the milk. A fine state of division is necessary to prevent a crystal- lization of the sulphate with the water, which would cause a loss of milk-fat.The dried mass is placed in a flask holding about 100 C.C. and closed with a well-fitting stopper, and 25 C.C. of ether added. After shaking for five minutes and cooling to the temperature of the air, 5 C.C. of the clear liquid are removed by means of it pipette, the point of which is covered with cotton-wool to prevent particles entering, and the dissolved fat estimated by evaporation in a weighed flask. From this the percentage on the whole can be calculated. The results obtained by this method agree well with those obtained by the older method, in which sand is mixed with the milk and the fat subsequently extracted with ether. Results in grammes per litre : Full Milk. Pull Milk. Watered Milk. Skim Milk. Skim Milk. Old Method ... 34.6 36.0 21-2 2.7 3-2 New Method ...34.6 36.0 21.2 2.9 3.3 When anzllysing butter-milk or sour milk it is necessary to have them as homogeneous fluids. To effect this, a litre of the butter-milk or sour milk is warmed to about 45", shaken for five minutes with 10 grammes of NaHCO,, and allowed to cool to the temperature of the room. The authors promise their results as soon as they have proved that, besides fat, no other constituents of the neutralized milk dissolve in ether. The contribution concludes with a, description of an apparatus by means of which,THE ANALYST. 21 from the weight of the fat, its percentage in the milk can be immediately read off. I t is on the principle of the steel-yard with a running weight, the mass of which is calculated for the specific gravity of the milk and other conditions.C. A. M. On the Estimation of Nitrogen in Nitro-cellulose. Duschan Stanojewitsch. (2eit.fiir ungezonnd. Chemie, 1894, Heft 22, pp. 676-678.)-Lunge's method of estimation by measurement of the gas liberated by the action of H2S04 and mercury on the substance is open to the objection that the action of the air in the flask on the nitric oxide causes an error. To avoid this, the author has devised an apparatus which combines the methods of Schloesing and Lunge. The weighed substance is introduced, together with 50 or 60 grammes of mercury, into the decomposition flask, which is connected with a modified nitrometer filled with a 25 per cent. solution of soda. After the air in the flask has been displaced by a current of CO,, 10 to 15 C.C.of H,SO, areintroduced, and the flask shaken until all the gas is liberated. To completely drive it over into the nitrometer, the flask is warined while a current of CO, is passed in. For measurement it is advisable to in- troduce the gas into a measuring cylinder filled with water, which can be done by means of a delivery tube with a stop-cock at the top of the nitrometer. The apparatus is especially suitable for the estimation of nitro-glycerine in dynamite. Minute pieces of the sample are digested in the flask with H,SO, and mercury. The decomposition is rapid, and the presence of carbonates does not influence the result. In the case of gelatinized nitro-cellulose it is necessary to warm the mixture over a water-bath, but the mercury and nitro-cellulose should not be warmed before the in- troduction of the H2S0,, since the reaction is then so violent that an explosion may occur.C. A. M. A New Method of Estimating Glucose by Alkaline Copper Solution. MM. Allein and Gaud. (Jow. Phurnz. et Chim., 1894, xxx., pp. 305-307.)-To avoid errors introduced by the base keeping the copper in solution, the authors recommend the substitution of ammonia for the fixed alkalies. To cause ammonia to act on glucose it must be kept in a sealed tube with it at 100" for thirty or forty hours', and even then only a small quantity of the glucose is destroyed, 5 to 6 per cent. of formic acid being produced; whereas glucose, treated in a similar way with the fixed alkalies, yields up to 60 per cent. of lactic acid. The solution is prepared by dissolving 8.7916 grammes of electrolytic copper in 93 grammes of H,S04, diluting with an equal quantity of water and making up to a litre with concentrated ammonia solution.10 C.C. of this is equivalent to 0.05 gramme of glucose. I n the estimation, 10 C.C. of the copper solution are measured into a flask and 10 C.C. of ammonia solution added. The flask is furnished with a cork with three holes, so that the extremity of the burette containing the sugar solution can be inserted and a current of hydrogen introduced. It is placed on a water-bath maintained at a tem- perature of from 90" to 95" while the hydrogen is passed in. When the temperature Being free from organic impurities, the solution keeps well,22 THE ANA4LYST. of the interior of the flask is at 80°, the sugar solution is introduced drop by drop from the burette until the copper solution is decolorized.Cuprous oxide is formed, but is dissolved to a colourless liquid at the moment of formation by the ammonia, so that it; is easy to judge when the blue colour is about to disappear. Excellent results are said to be obtained by the process, the only disadvantage of which is the neces- sity of manipulating at from 80" to 85" in order not to drive off the ammonia. C. A. M. On the Estimation of Boron. Henri Hoissan. (Bzdl. SOC. Chin%. de Paris. 1894, 18-19, pp. 955-958.)-The process is a modification of Gooch's lnethod, by which the estimation is made more rapid and loss by volatilization avoided. The weighed boron compound, which must be in the form of boric acid or a borate, is placed in a, distilling tube, the neck of which is closed by a stoppered funnel ground into it.One C.C. of HNO, is introduced, and the contents of the flask distilled to dryness by means of a water-bath. The distillate, condensed by the usual spiral worm, falls into a flask containing an excess of ammonia and connected with bulb tubes also containing ammonia, The residue in the flask is distilled with successive portions (10 c.c.) of pure methyl alcohol, being taken to dryness each time, until the alcohol distils over free from boric acid, as shown by the flame test. The ammoniacal distillate is emptied into a platinum basin, in which is a known quantity of calcium hydrate, previously weighed in the anhydrous state. On evaporation over a water- bath at about 70", borate of calcium is left, and the increase of weight gives the quantity of boric anhydride from which the boron in the sample can be calculated.The calcium oxide is prepared by calcining pure calcium nitrate. A large excess is necessary : for 0.5 grammes boric acid, about 8 or 10 grammes. The method gave the following results when used to estimate boric anhydride prepared from a pure boric acid : I. 99-73 The author has used the sulphste of boron and in 11. 111. IV. 99-67 99%2 99.6 per cent. process for the estimation of boron in the phosphate and metallic borates and borides. C. A. M. Toxicological detection and estimation of Arsenic. Ernest Barillot. (Bull. de In SOC. Chim. de Pn~is, 1894, Tomes xi. andxii., pp. 958,959.)-Marsh's process is modified so that the arsenic deposited in the tube may be weighed.The generating flask is connected with a tube of green glass heated in three sections by burners. The substance to be analysed, after the animal matter has been destroyed by one of the ordinary processes, is treated with fuming nitric acid and potassium nitrate, the nitrous acids being afterwards removed by heating with excess of sulphuric acid. The solution is concentrated down to about 200 c.c., and after being proved to be free from nitric and nitrous acids, is introduced gradually into the generating flask, where the gas is liberated in the usual manner. The sections in which the rings of arsenic are deposited are detached and weighed, washed with funling HNO,, dried and again weighed, the difference giving the amount of arsenic.C. A. M.THE ANALYST. 23 Separation of Copper from Cadmium, Zinc and Nickel. P. N. Rikowa. (Chem. Zeit., 1894, xviii., 1739.)-The author utilizes the reaction given by a soluble iodide and phenylhydrazine with a copper salt (see preceding abstract) to separate copper from cadmium, zinc and nickel. The solution containing the metals is acidulated with sulphuric acid, treated with phenylhydrazine (the hydrochloride may be used, as the presence of a chloride is of no significance in this use of the reaction) and precipitatgd with potassium iodide, added drop by drop, to avoid an excess, in which the precipitate is somewhat soluble. Provided enough phenylhydrazine be present, a small excess of potassium iodide is not detrimental.The copper is com- pletely separated, and the remaining metals are retained in solution, The remaining stages of the determination may be performed by the ordinary methods. Salts of mercury and iron must be absent, as they yield precipitates with phenylhydrazine. B. B. The Purification of Saltpetre from Perchlorate. V. Panaotovie. (Chew?,. Zeit., 1894, xviii., 1567.)-The author confirms the statements of previous observers that commercial saltpetre is usually contaminated with perchlorate (vide THE ANALYST, xix. 22). Out of 180 casks from a well-known Hamburg firm, 122 contained more than 0.25 per cent. of perchlorate, and only 7 were perfectly free therefrom. Although saltpetre containing perchlorate must have been used for years in powder manufacture, yet it does not necessarily follow that the presence of this impurity is a matter of indifference.Explosions that have received no satisfactory explanation insy have been due to it, the more so as pure potassium perchlorate, when sub- stituted for potassium chlorate in the manufacture of signal-lights, has proved unstable, spontaneous ignition taking place after four months' storage. These facts are sufficient to render it desirable to remove perchlorate from saltpetre intended for the manufacture of explosives. An attempt to effect this by fusing the salt until the perchlorate had been decomposed proved a failure, as much nitrite was formed, together with some free alkali, the removal of which products was dificult and costly. The purification was eventually achieved by dissolving the saltpetre in hot filtered spring-water (free from chlorine) to a strength of 48" B, adding a little size to favour the separation of insoluble impurities, decanting and allowing the solution to cool to 25" C, stirring to promote the separation of small crystals. The mother liquor (28" B) was poured off, and the crystals washed five or six times with pure water. The mother liquor was concentrated, and the separated crystals re-treated. From the final mother liquor crystals of potassium perchlorate were isolated and identified. B. B. Preservation of Starch Soluticn. H. Krdl. (Pham. C. H., m94, xv., 606; through Chem. 2eit.)-The author recommends that the starch solution used in carrying out Hiibl's iodine absorption process be prevented from decomposing by the addition of chloroform. A small quantity of chloroform is added, and the mixture well shaken. The product can be kept for months without suffering change. B. B.24 THE ANALYST Detection of Nitrites in presence of Iron Sa,lts. H. Krhl. (Pharm. C. H., 1894, xv., 619.)-The detection of nitrites by means of an iodide and starch solution --e.g., in drinking-waters-fails in the presence of ferric salts, as the latter also liberate iodine. The acid necessarily added is a source of error, even when acetic acid is used, as iodine is slowly liberated in the absence of nitrites, These draw- backs can be avoided by the use of oxalic acid, in the presence of which ferric salts are stated to liberate no iodine. B. B.

ISSN:0003-2654    

DOI:10.1039/AN8952000016

出版商:RSC    

年代:1895

数据来源: RSC

摘要:

24 THE ANALYST REVIEW. THE SALE OF FOOD AND DRUGS ACTS. BELL and SCRIVENER. Second edition. (Shaw and Sons, Fetter Lane, E.C. Price 4s. 6d.) The appearance of a second edition of this book affords additionallevidence of the increased interest taken in the working of the Food Acts. The chemical reviewer would be guilty of a presumptuous act were he to venture upon a criticism of the purely legal portions of a book written by two learned barristers, but as far as we can see, the authors have recorded, in a very systematic manner, the most important of the numerous decisions given in courts of law touching the Sale of Food apd Drugs Acts. Perhaps we might have been apared a good many of the decisions of the lower courts, which, as every analyst knows, are puzzling and contradictory. But the authors have attempted to do more than write a legal guide, for, apparently without any chemical qualification, they have ventured to enter into the discussion of matters purely chemical, with results such as might have been anticipated.I n commenting upon Section 6, truly described as ‘( a most important section, and the entire working of the Sale of Food and Drugs Act very nearly depends upon it,” the authors discuss the composition of the more important articles of food, We are sorry to find that the remarks unde;. this head are neither characterized by the absence of bias nor by the presence of modern knowledge. They often appear to be a faint echo of the information contained in a well-known little handbook on ‘( The Chemistry of Foods ” published *eleven years ago.Thus, the remarks as to the variability of the cornposition of butter-fat are obviously not based upon analyses of commercial butters made from the mixed milk of a number of cows. I n connection with the adulteration of butter, “ the more common offence” is, nowadays, not the sale of a factitious article, but rather the sale of mixtures of butter and margarine. The remark that “ it is a common practice to mix a certain proportion of starch with yeast as a preservative ” appears uncalled for, unless the book were written for defence advocates only. As to milk, the book takes us back to those bygone times in which the notorious lecture was delivered at the Health Exhibition, the Manchester milk case occurred, and the old Wanklyn process was in use, with limits fixed at 9 per cent. and 2.5 per cent. respectively. The chemical part of the little work affords another proof of the good sense contained in the old adage, where the cobbler is advised to strictly confine his attention to his last. 0. H.

ISSN:0003-2654    

DOI:10.1039/AN8952000024

出版商:RSC    

年代:1895

数据来源: RSC