摘要:

OCTOBER, 1915. Vol. XL., NO. 476. THE ANALYST. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS. THE ESTIMATION OF STARCH IN COCOA BY MEANS OF TAKA-DIASTASE. BY CECIL REVIS AND H. R. BURNETT. (Read at the Meeting, June 2, 1915.) THE estimation of starch in cocoa has been carried out hitherto either by direct acid conversion or by the use of diastase, or of diastase followed by acid conversion.Direct acid conversion carried out on the fat-free dry cocoa matter is the worst possible method, as there are present in cocoa large quantities of pentosans and other bodies leading to the production of reducing substances when boiled with acid. The magnitude of the error is easily seen from the results of such conversions published by Winton and others (“An.Rep. Conn. Agric. Exp. St.,” 1902, p. 270), who give 23-66 per cent. crude starch in nib and 12.59 per cent. in shell as mean figures; while from microscopical examination it is practically certain that shell does not actually contain any starch at all. Bolton and Revis (see “Fatty Foods,” p. 298) found 19 to 23 per cent. in nib and 9 to 10 per cent. in shell by the use of a modified form of Ewer’s method.Better results are obtained by the use of diastase followed by acid conversion, in which case Winton and others record 17 per cent. in nib and 4.47 per cent. in shell as mean figures; but Davis and Daish (J. Agric. Sci., 1913, 5, 437; ANALYST, 1913,38,504), in an investigation into the various methods of estimating carbohydrates in plant substances, have shown that there is a distinct loss of carbohydrate during the acid conversion which follows the diastase treatment, and that low results are obtained.These observers have also shown that the simple diastase method of O’Sullivan fails in the case of plant extracts when a clearing agent has to be employed after the starch conversion, owing to the mechanical removal of dextrin from solution by the precipitate formed during the clearing process.On account of these difficulties they experimented with taki-diastase as the starch converter, since, with this substance the dextrin stage is rapidly passed through, All of these methods lead to erroneous results, but for different reasons.430 REVIS AND BURNETT: THE ESTIMATION OF STARCH IN COCOA and there are then present only maltose and dextrose, which may be easily deter- mined by combined polarimetric and copper reduction methods, and there is no loss of carbohydrate in such a solution when a clearing agent is used.The proportions of maltose and dextrose vary with the time of action of the takh-diastase, but dextrin completely disappears after a few hours at blood-heat temperature.As the problem presented by cocoa is very similar to that of plant extracts, we hrve applied the use of taka-diastase to the determination of starch in cocoa with success. 4 few preliminary experiments showed that the conclusions of Davis and Daish as to the exactness of the method were fully justified, and we also found that other observers obtained identical results on the same sample.A clearing agent is necessary in the caSe of cocoa, and we have found that a, solution of acid mercuric nitrate, made up on the formula of Wiley for use in clearing milk, behaves admirably for this purpose. Five grms. of fat-free dry cocoa matter are weighed out into a beaker and thoroughly stirred with 50 C.C. of 10 per cent. alcohol (by volume) and filtered under pressure-for preference in a large Buchner funnel as the process is thereby considerably hastened.The cocoa is then washed with two. further quantities of 50 C.C. of 10 per cent. alcohol, and finally with 10 C.C. of 95 per cent. alcohol (by volume), taking care that at no stage the cocoa sucks dry, as it is then more difficult both to wash and to remove from the filter.This alcohol washing is very important, as otherwise great difficulties occur later on and erroneous results are obtained. The moist cocoa is then scraped and washed out of the funnel into a 250 C.C. flask with about 125 C.C. of boiling water, well mixed, and the flask placed in boiling water, with constant shaking, for fifteen minutes to gelatinise the starch. The contents of the flask are then cooled to 38' C., mixed with 0.05 grm.of takh-diastase, rubbed up with a little water, 2 C.C. of toluene added, and the flask, after shaking and stoppering, placed in an incubator at 38" C. for twenty-four to thirty-six hours, shaking at intervals. At the end of this period 10 C.C. of & NaOH are added to stop the action, the flask is cooled to 15' C., about 100 C.C.of water added, then 10 C.C. of acid mercuric nitrate solution run in on the surface, and finally water to the mark below the toluene. The contents of the flask are then mixed and filtered. To 100 C.C. of the filtrate (which should be perfectly colourless and bright), carefully measured into a flask, are added 0.5 grm. of sodium phosphate (Nat2HP0,.12H20), and, after this has dissolved, 10 C.C.of sodium hydroxide solution are run in, the Bolution being agitated as this is done. The contents of the flask are mixed and filtered, and, in the case of 5 grms. of cocoa matter, 50 C.C. are used for the gravinietric copper determination, the polarimetric readings being also made on this filtrate. The solution of sodium hydroxide used above must be so adjusted that 10 C.C.just neutralise 4 C.C. of acid mercuric nitrate solution, and should on no account be in excess, it being preferable to leave the solution slightly acid after the addition of the alkali. I n our case the solution contained 55 grms. of ground caustic soda (97 per cent. NsOH) per litre. We carefully determined that this treatment with acid mercuric nitrate caused no loss of starch conversion products.I n The proeess is as follows : We have examined a number of COCOBS, both nib and shell, by this method.BY MEANS OF TAKA-DIASTASE 431 all cases the partition into shell and nib was made by ourselves from the whole roasted bean i n order to be sure that the differentiation was a true one. Shell.-Four samples of shell were examined, using 10 grms.in each case, and only negligible reductions and polarimeter readings were obtained. The results are given in the table below. The copper oxide in each case was that obtained from the 50 C.C. of final solution used, and the polarimeter figures are the actual Venteke saccharimeter degrees obtained on polarising the filtrate after the acid mercuric nitrate and phosphate treatment.They have not been calculated to he original shell. Sample of Shell CuO Weighed. 1. Blend ... ... 0.038 grm. 2. Guayquil ... ... 0.031 ,, 3. Trinidad ... ... 0.022 ,, 4. Grenada ... ... 0.024 ,, Veiitzke Degrees. + 0.04 + 0.01 + 0.03 + 0.05 From these results it is evident that cocoa shell contains no true starch, and it is Nib.-Five samples were examined, after careful extraction of the fat, with the probable that this is the first time that it has been demonstrated analytically.following results : I’erucutage of Starch in Fat-Free Dry Nib. Cocoa. ... Accra (low grade cocoa) ... ... 12.8 Gunyquil ... ... ... ... ... 8.0 Trinidad ... ... ... . . . ... 14‘5 Grenada, ... ... ... ,. . ... 12.3 San Thomi! ... ... ... . . . . . . . 12.4 I n all the above cases estimations were made with 5 and 10 grrns. in order to eliminate the effect of the volume of the precipitate caused by the acid mercuric nitrate, but it is probable that, if an allowance of 3 C.C. be made for the volume of precipitate from 5 grms.of cocoa matter, that such allowance is within the error of experiment. We had hoped to find that the percentage of starch in cocoa would prove to be a, fairly constant quantity, and so provide a means of estimating ‘( cocoa matter ” in mixtures.The number of samples examined is not sufficient to allow of any very definite statement, but, with the exception of Guayquil, the percentage appears to be about 13 per cent., and probably in blends might be taken to approximate to this figure. It might be noted that the figure obtained by Winton and others, after deducting the figure for shell, is 12.5 per cent.(diastase and acid) and 11-1 per cent. (crude acid conversion), and by Bolton and Revis is 11.5 per cent. The acid mercuric nitrate solution is made as follows: Pure mercuric oxide (not mercury as recommended by Wiley) is dissolved in twice its weight of nitric acid (sp. gr. 1-42), and the resulting solution diluted to five times its volume with water.The powder keeps well in the dark, but should be tested before use to see if it has any reducing power or is optically active, i n which case a control must be run side by side with the experiment. Taka-diastase can be obtained from Messrs. Parke, Davis and Co.432 REVIS AND BURNETT: THE ESTIMATION OF STARCK IN COCOA In conclusion, we desire to express our thanks to Mr.A. W. Stokes and to Mr. T. Macara for obtaining reliable samples of cocoa bean for us. DISCUSSION. The PRESIDENT remarked that the method of acid hydrolysis was well known to give erroneous results in the case of substances like cocoa, the extent of the error depending on the nature of the cellulose and pentosans present. He could not quite agree with the authors, however, in passing censure on the ordinary diastase method, provided that it was properly carried out.A blank determination was, of course, necessary, and this must include hydrolysis with acid. Failing this, the results would obviously be too high, to an extent possibly as great as in the case of direct acid hydrolysis. Malt extract had the advantage of being eaeily obtainable any- where, whereas in some places there might be some little difficulty in obtaining tak&-diastase.Mr. J. L. BAKER said that he had seen the aubhor’s process carried out by Mr. Hulton, and had been impressed by its smoothness of working. He had tried the ordinary method (i.e., hydrolysis with acid and precipitation with phosphotungstic acid), but, as had been said, this was useless in the case of products like cocoa. He regarded the use of taki-diastase as a distinct step forward, and he must say that he should prefer it to malt extract.I t was quite readily obtainable in a dry condition, and its hydrolytic activity remained fairly constant even after several months’ keeping. He did not see any particular necessity for continuing the action for thirty-six hours.Davis and Daish had shown that, so long 8s the dextrin stage was passed, the relative proportions of dextrose and maltose were immaterial. Mr. REVIS, in reply, said that the use of ordinary diastase was quite satisfactory as long as the solution did not require clearing; but if any clearing agent was used, dextrin was liable to be carried down mechanically.Moreover, Davis and Daish had shown that, on hydrolysis of the results of the diastase conversion with acid, dextrose disappeared to an appreciable extent. Personally he had always thought that such loss of dextrose was small, but according to Davis and Daish it might be rather considerable. The PRESIDENT remarked that the solution might be made up to a known bulk and a portion filtered off. Mr. REVIS said that even then some clearing agent would have to be used, and some dextrin would thereby be thrown down which should g? into the filtrate. That was quite clear from the results obtained by Davis and Daish. Tak&-diastase was quite readily obtainable. One must be careful to see that it had no reducing or polarising power, as some samples had, in which case the necessary allowances had to be made. The time of standing was merely a question of convenience. At first they had thought that the conversion might perhaps not be complete after the shorter period, but they now thought that eighteen hours would probably be sufficient. I t would probably be simplest to allow twenty-four hours.

ISSN:0003-2654    

DOI:10.1039/AN9154000429

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

EFFECT OF FEEDING ON THE COMPOSITION OF MILK AND BUTTER 433 THE EFFECT OF FEEDING ON THE COMPOSITION OF MILK AND BUTTER: LINSEED CAKE AND HEMPSEED CAKE. BY H. T. CRANFIELD AND MARGARET G. D. TAYLOR. DURING the present war many feeding-stuffs have been diverted to this country from the Continent-feeding-stuffs which previously have rarely been met with on English farms. One of these-hempeed cake-is now being offered for sale in this country in considerable quantities, and in the autumn of last year it was decided at the Midland Agricultural and Dairy College to compare the feeding value of this substance with linseed cake as regards milk production.Facilities being offered us, we decided to note the effects (if any) of these foods on the composition of milk'and butter. Hempseed cake is somewhat similar in appearance and general characteristics to linseed cake.Its only apparent drawback is its poor keeping quality, especially in the summer time. The two cakes used in this experiment gave the following analyses : Linseed Cake. Hempseed Cake. Moisture ... ... ... 13-85 11-47 Oil ... ... ... ... 8.98 7-87 Albuminoids ... ... ... 27.39 28.87 Soluble carbohydrates ...33.26 23.85 Fibre . . . . . . ... .., 10.42 21.07 Ash ... ... ... 6.10 6-87 100*00 100.00 Total food units . . . . . . ... 124.20 115.7 ... Experimental Details. Two sets of cows (crossbred shorthorns) were selected, four in each set. They were carefully chosen, so as to be as even as possible as regards their milk yields and periods of lactation. They had been out at grass, but a few days before the com- mencement of the experiment they were brought in to the sheds for the winter.- During the first few weeks of the experiment the milk yield increased considerably, this being probably due to the poor quality of the pasture during late autumn. Feeding. First Week.-All the eight cows received the following daily ration: Two Ib. mixed meal (bran and sharps), 14 lb.hay, 7 lb. straw chop, 56 lb. cabbages, 1 lb Egyptian cotton cake, 2 lb. linseed cake, 2 lb. hempseed cake. For the first four days Set A received a gradually diminishing quantity of hempseed cake and an increasing amount of linseed cake. Set B likewise were given a diminishing quantity of linseed cake and a corresponding increased amount of hempseed cake.The last three days of this week the cows were on the following rations ; Second Week-This week the cows passed through a transition period.434 CRANFIELD AND TAYLOR: THE EFFECT OF FEEDING Set A. 2 lb. mixed meal (bran and sharps). 7 ,, straw chop. 1 ,, Egyptian cotton cake. 4 ,, linseed cake. 14 ,, hay. 56 ,, cabbages. Set €3. 2 lb. mixed meal. 7 ,, straw chop. 1 ,, Egyptian cotton cake.4 ,, hempseed cake. 14 ,, hay. 56 ,, cabbages. Third and Fozcrth Weeks.-Rations were the same as above. Fifth Week.-Transition period. Set '4 gradually changed from 4 lb. linseed cake to 4 lb. hempseed cake, and Set B vice versa. Sixth and Seventh Weeks.-Set A received the normal basal ration, plus 4 lb. hempseed cake, while Set B received the basal ration, plus 4 lb.linseed cake. ,Eighth Week.-First three days were a transition period back to equal quantities of linseed cake and hempseed cake. The last four days the cows received the same ration as in the first week of the experiment. MILK. Proportionate samples were taken of successive night's and morning's milk from each set of cows, and the following determinations made : Fat by the Gerber method, Total solid's by evaporation.Proteins by aldehyde figure. Fat. During the whole experiment the percentage of fat varied from 3.3 to 4.5, and the following figures were obtained : Weekly Averages: Per Cent. 1st Week. 2nd Week. 3rd Week. 4th Week. 5th Week. 6th Week. 7th Week. 8th Week. Set A ... 4-14 4.22 3.94 3-81 3.62 3-63 3.59 3.66 Set B ... 4.10 4-23 3.96 3.83 3-65 3.72 3.72 3.92 Set A.Set B. Maximum percentage of fat . . . ... 4.45 4.50 Average percentage of fat ... ... 3.83 3-89 1 3.80 3.75 Minimum percentage of fat . . . ... 3.30 3.40 ( Linseed Cake. Hempseed Cake. Average percentage of fat from It will be seen from the above figures that the percentages of fat in the milk of both sets of cows followed each other irrespective of the change of cake, and therefore it does not appear that those two cukes exerted any influence on the percentage of fat.The difference of 0.05 per cent. in favour of linseed cake is too sinall to be considered. The percentage of fat decreased rather rapidly during the third, fourth, and fifth weeks. This was probably due to the fact that the quantity of milk increased very much during this period, and so exercised a diminishing efiect on the percentage of fat.Solids-no t-Fat. The two sets of cows gave figures which followed one another, but at a rather There is no apparent influence shown, wider interval than in the case of the fat. however, due to the change of cake.ON THE COMPOSITION OF MILK AND BUTTER 435 Weekly ,4 vcragcs : Per Cent. 1st Week.2nd Week. 3rd Week. 4th Week. 5th Week. 6th Week. 7th Week. Sth Week. Set A 8-62 8.80 8-70 8-84 8.95 8.89 8.86 9.05 Set B 8.56 8.67 8.61 8.66 8.75 8.72 8.71 8-76 &laximum percentage of solids-not-fat . . . 9.56 9.17 %himum percentage of solids-not -fat . . . 8.44 8.33 Average percentage of solids-not-fat ... 8.84 8.68 Set A. Set 13. Linseed Cake. Herripseed Cake. { 8-74 8.75 Average percentage of solids-not-fat from Proteins (from Aldehyde Figure).There appears to be some slight variation in the percentage of protein, following the change of cake (see Fig. l), but since the difference in the average percentage is only 0.05, and the method being only an approximate one, this variation is hardly worth consideration. Week19 Averages : Per Cent. Set A 3.38 3.42 3-35 3-42 3-56 3-33 342 3.53 Set B 3.35 3.30 3.35 3.35 3.50 3.39 3-49 3.51 Set A.Set H. Mavximum percentage of protein . . . ... 3.69 3-66 Minimum percentage of protein . . . ... 3.15 3.10 Average percentage of protein . . . 343 3.40 1st Week. 2nd Week. 3rd Week. 4th Week. 5th Week. 6th Week. 7th Wcek. 8th Week. Linsced Cake. Henipseed Cake. { 3.41 3.36 Average percentage of protein from B u TTER. On alternate days a portion of the night’s and morning’s milk from each set of cows was separated, and the cream ripened with a starter and churned in a glass experimental churn.The following determinations were made on the butter fat : Reichert-Meissl value. Kirschner value. Polenskk value. Ref ractom et er figure. Reic her t-Meiss I Va h e . Not the slightest variation due to the linseed and hempseed cake was noticed.A drop during the first ten days was succeeded by t~ substantial rise, which continued until the middle of the sixth week, when the figures began again to fall (see Fig. 2). One notices that the curves for this value are complementary to the curves for the percentage of fat. We draw from this the conclusion that the improved quality of the food (subsequent to the cows leaving the poor pasture) was responsible for the increased percentage of soluble volatile fatty acids as indicated by this value.436 CRANFIELD AND TAYLOR: THE EFFECT OF FEEDING Weekly Averages : Reichert-Mcissl Value.Set A 24.35 23-69 24-89 27-75 29-55 29.92 29-52 28.34 Bet B 24.14 23.04 24-36 26.15 28.56 28.86 28.75 27-61 Set A.Set B. Maximum Reichert-Meissl value . . . 30.58 29-37 Minimum Reichert-Meissl value . . . 93-10 22-76 Average Reichert-Meissl value 97-25 26.43 1st Week. 2nd M7eek. 3rd Week. 4th Week. 5th Week. 6th Week. 7th Week. 8th Week. Linseed Cake. Hempseed Cake. 27.49 Average Reichert-Meissl value for butter from 1 \ 27.56 Kirs c hner Va h e . The remarks made for the Reichert-Meissl value equally apply to the Kirschner value. Weekly Averages : Kirschner Value.Set A 20-32 20-05 20.81 92-56 23.75 23-78 23-31 22-32 Set B 20.30 19.75 20.65 21.30 22-51 22-96 22-41 21.44 Set A. Set B. Maximum Kirschner value . . . ... 24.40 22.98 Minimum Kirschner value . . . ... 19.33 19.12 Average Kirschner value . . . 22-11 2141 1st Week. 2nd Week. 3rd Week. 4th Week.5th Week. 6th Week. 7th Week. 8th Week. Liiiseed Cake. Hemyseed Cake. 22-26 Average Kirschner value for butter from { 22.18 Polenskd Value. The curves for this figure (see Fig. 2) follow approximately the path of .the Reichert-Meissl and Kirschner curves; but it will be noticed that during the fifth week (transition period) the lines intersect, and the results given by cows A show a rather lower set of figures in the sixth week than would have been the case if the curves had been strictly uniform.However, since the difference between the averages for the two cakes is very small (0.08 per cent.), we do not feel justified in making further comment. Weekly Averages : Polenskd Value. 1st Week. 2nd Week. 3rd Week. 4th Weak. 6th Week. 6th meek. 7th Week. 8th Week.Bet A 1-55 1-50 1-67 2.02 2-53 2-33 2-46 2-43 Set B 1.65 1.47 1-62 1.89 2.62 2.50 2.44 2-43 Maximum Polenskk value . . . ... 2.7 2.9 Minimum Polenskh value . . . ... 1.4 1.4 Set A. Set. B. Average Polenskh value ... 2-06 2.08 Liiiseed Cake. Hempseed Cake. { 2-16 2.08 Average Polenskb value for butter from Refractometer Figure. The readings were taken at 35' C. with a Zeiss butyro refraotometer.The two cakes do not appear to have influenoed the refractive index of the The result of leaving the pasture for a more nutritious ration is again butter-fat.ON THE COMPOSI'L'ION OF MlLK AND BUTTER 437 PER I CENl ~ -- -- TI FIG. 1.438 I ON THE COMPOSITION OF MILK AND BUTTER 3 c FIG. 2.CRANFIELD: ON THE VALUES FOR BUTTER 439 indicated by the rapid fall in this figure (see Fig.2). As one of us has previously noticed (ANALYST, 1911, 36, 446), the refractometer figure varies inversely with the Reichert-Meissl and Polenskc5 figures. Weekly Averages : Refradometer Figure. Set A 48-0 48.0 47-62 46-56 46.10 46.17 46.70 46.67 Set B 48.0 48-25 47-87 47.25 46-45 46.33 46-45 46-58 Set A. Set I3. Maximum refractometer figure . . . 48.5 48.75 Minimum refractometer figure .. . 46.0 46-0 1st Week. 2nd Week. 3rd Week. 4th Week. 5th Week. 6th Week. 7th Week. 8th Week. Average refractometer figure 46.98 47.15 Linseed Cake. Hempseed Cake. 46.70 Sverage refractometer figure for butter from { 46.74 Quality of the Butter. On one or two occasions it was noticed that the butter from the hempseed cake feeding was not quite so good as regards flavour and colour as the sample churned from the milk of the cows receiving linseed cake.In the majority of samples, however, there was very little difference, and we are of the opinion that cows receiving hempseed cake would produce a good quality butter. Cone lusions. 1. The composition and quality of milk and butter produced by feeding, hemp- seed cake is quite equal to that obtained by feeding linseed cake. 2. The effect of removing cows from poor pasture on to a well-balanced ration in stall is shown very strikingly by the data obtained from this experiment. It caused a large fall in the percentage of fat, a considerable rise in the Reichert- Meissl, Kirschner and Polenskc5 values, and a fall in the refractometer figure. In conclusion we desire to express our best thanks to Miss N.D.D., and Mr. J. Dunlop, B.Sc., for facilities and help in the churning of the samples. MIDLAND AGRICULTURAL AND DAIRY COLLEGE. * ? B * + € + * Marion Blunt, collection and

ISSN:0003-2654    

DOI:10.1039/AN9154000433

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

CRANFIELD: ON THE VALUES FOR BUTTER 439 ON THE RELATION BETWEEN THE REICHERT-MEISSL, KIRSCHNER AND POLENSKB VALUES FOR BUTTER. BY H. T. CRANFIELD. MUCH work has been carried out on the relation between the Reichert-Meissl and Polenske values for butter, and Polenskb’s original limits are now generally accepted. Many workers, however, have noticed that samples of genuine butter are often met with which do not give figures within these limits, and in fact would, in view of Polenskb’s table, point to adulteration with coconut oil up to 4 or 5 per cent.; con- versely butters often give values which would allow of considerable adulteration with coconut oil before PolenskB’s limits were exceeded.440 THE RELATION BETWEEN THE REICHERT-MEISSL Bolton, Richmond, and Revis (ANALYST, 1312, 37, 183), suggested that the rela- tion between the Kirschner and Polenskk values might be more sensitive than the rela tion between the Reichert-Meissl and Polenskk values now accepted.With the object of throwing more light on this question, I give the figures obtained for these three values, from all the samples of butter examined recently in my laboratory in connection with the Linseed Cake and Hempseed Cake experi- ments (see previous paper). The rations given were quite normal, therefore these samples can be taken as representing genuine average butter.The samples are arranged in ascending order of the Kirschner value. TABLE I. Kirschner Value. 19.12 19.33 19.65 19.85 19-88 20.14 20.17 20.19 20.22 20-24 20-26 20.27 20.37 20.45 20.63 20.65 20.70 20-73 20.82 20.92 20.93 21.02 21.05 21.12 21.12 21-63 21465 21 -72 21.77 21.88 22.00 Polenskh Value.1.4 1.4 1-4 1.7::: 1.4 1-5 1.4 1.6 1.6 1.5 1.6 1.5 1.5 1.7 1.7 1.7 1.6 1.9 2.2" 1.8 I -6 1.85 1.9 14 1.7 2.4 2.0 1.7 2.4 2-7 2.4 Rciclieit-Meissl Value. 22.76 23.10 23.37 24.20 22 88 23.65 23.87 23-98 24-20 94-31 23-49 23.54 24-20 24.75 23 98 24-09 24-42 24-64 27.17 25.85 24.97 25.52 25-73 25.19 25.41 27.50 27-61 26-18 28.38 28-16 27.94 Kirschner Value.22-05 22.19 22.23 22.24 22-37 28-40 2247 22 50 2353 22.53 22 64 22-65 22.66 22 *79 22.87 22 -95 22.96 23.98 23.00 23.11 23.25 23.27 23.38 23.46 23.51 23.59 23.63 23.68 23.97 24-20 24-40 Poleliskt Val I1 e . 2.2 2.3 2-0 2.5 1 . g ::: 2.8 2-5 2-6 2.7 2-7 2.6 2.5 2-2 2.3 2 -8 1.8* 2.5 2.9 2.5 2.6 2.3 2.4 2-55 2.2 2.5 2.2 2-4 2 3 2.6 2.7 2.6 From these figures the following relation can be drawn : Average of Limits of Polenslie Value.Polenskh Value. Kirschner Value. 19-20 1-46 1'4-1.7 20-21 I -65 1.4-2.2 21-22 2.05 1 07-2 * 7 22-23 2.43 1 -8-2 *9 23-24 2.41 2 *2-2.6 Reicher t-Meissl Value. 28.27 28.16 27.50 28.49 27.39 29.37 28.05 29.15 2 3-38 28.16 29.04 29-15 28-27 99-04 29 04 27.28 28.71 29-26 28.93 30.14 29.04 28.71 28.93 28.49 29.70 29.26 29-92 29.81 29.70 30.14 29.92KIRSCHNER AND POLENSKE VALUES FOR BUTTER 441 I t will be noticed that the average values agree very well with the relation given by Bolton, Richmond, and Revis (ANALYST, Zoc.cit.). There are several samples, however, giving Polenskt5 values much higher and lower than the average (Table I., *), and it appears to be a matter of difficulty to fix limits for the Polenskt5 value which would be narrower than those adopted by Polenskd in relation to the Reichert-Meissl value. I t seems to me that there may possibly be some definite relation, within certain limits, between all three values.I find that the figures representing the soluble volatile fatty acids other than butyric acid (Lo,, the difference between the Reichert- Meissl and Kirschner values) follow approximately the Polenskt5 values.Therefore the ratio X should be fairly constant. I have worked out this ratio for all the samples given in Table I., and the results are as follows : RM-K P. TABLE 11. Polcnskd Value. 1.4 1-4 1.4 1.4 1.4 1-5 1.5 1.6 1.5 1.6 1.6 1.6 1-6 1.6 1.7 1.7 1.7 1.7 1.7 1.7 1.8 1.8 1.8 1.85 1.9 1-9 1.9 2.0 2.0 2.2 2.2 R.M.-K. 3.64 3.77 3.72 3.00 3.70 3-51 4.07 3-27 3.83 3.79 3.98 3.23 3.72 4.04 4.35 4-30 3.35 3.44 4.29 446 4.93 4-07 4.33 4-50 3.91 4.68 5.02 5-96 5.27 6-35 6.22 R. M .-K. P. 2.60 2.69 2.66 2-14 2.64 2.34 2.71 2-18 2 -55 2.37 2.49 2.02 2.32 2.52 2.56 2.53 1-97 2-02 2.52 2-68 2-74 2.26 2-41. 2-43 2.06 2-46 2.64 2.98 2.63 2 089 2.83 - _.-__ Polenskb Value.2.2 2.2 2.2 2 3 2.3 2-3 2.3 2.4 2-4 2.4 2.4 2-4 2.5 2.5 2-5 2-5 2-5 2.5 2-55 2.6 2.6 2.6 2.6 2-6 2.7 2.7 2.7 2.7 2.8 2.8 2-9 R.M. -K. 5.61 5-03 5-67 5.97 6.25 5.79 6.13 5-87 6-61 5.94 5.44 6.29 6.25 5-58 6.50 5 75 5.93 6.19 5.55 6.65 6.40 7.03 5.73 5-52 6.28 5.85 5.63 5.94 6.97 6.17 6.28 R.M.-K. P. 2.55 2.29 2.58 2.60 2-72 2-52 2 67 2-44 2.75 2-47 2-27 2.62 2.50 2-23 2.60 2.30 2-37 2.48 2.18 2.56 2.46 2.70 2.20 2.12 2.33 2.17 2-09 2 *20 2.49 2.20 2.17 -- It will be seen that the figure varies from 1.97 to 2.98 on this ratio, but the majority of the samples lie between 2.2 and 2.8. What would be the effect of adding442 ABSTRACTS OF CHEMICAL PAPERS small quantities of margarine or coconuf oil to butter is a matter of conjecture at present, but I hope in the future to investigate this point. I put forward this suggestion of a relationship quite tentatively, with the hope that other workers will apply it to their butter figures and offer their criticisms. MIDLAND AGRICULTURAL AND DAIRY COLLEGE. + B e * @ *

ISSN:0003-2654    

DOI:10.1039/AN9154000439

出版商:RSC    

年代:1915

数据来源: RSC

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442 ABSTRACTS OF CHEMICAL PAPERS ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOOD AND DRUGS ANALYSIS. Apparent Effect of Acetic Acid upon the Constants of Butter-Fat. C. Bahlman. (J. I n d . and Eug. Chem., 1915, 7, 680-68l.)-A convenient method for the estimation of fat in ice-cream consists in weighing 9 grms. of the melted sRmple into a Babcock milk-bottle, adding 20 C.C. of glacial acetic acid, and then 10 C.C.of sulphuric aoid, and proceeding as in the ordinary estimation of fat in milk. The presence of the acetic acid prevents the charring action of the sulphuric acid on the sugar. The reading of the fat column in the neck of the bottle, multiplied by 2, gives the percentage quantity of fat in the sample. Attempts to prove that the separated fat consisted of butter-fat, by removing the fatty layer and subjecting it to analysis, were unsuccessful.The refractometer values obtained were always much lower than those shown by butter-fat, whilst the Koettstorfer and Reichert- Meissl values were too high. This was due to the presence of acetic acid in the fat. The acid may be expelled by heating the fat at 95OC. for one hour, and normal analytical results are then obtained if the fat consists of butter-fat.When the fat is separated from dairy products by decomposition with sulphuric or hydrochloric acid, no appreciable quantity of acid is retained in the fatty layer. w. P. s. Estimation of Ash in White Bread. J. W. Filippo and W. Adriani. (Chem. Weakblnd, 1915,12,570-576.)-0wing to the volatility of the sodium chloride, the amount of ash in bread as estimated by ignition is inaccurate.The sodium chloride will be about 0.5 per cent. too low, and the ash free from sodium chloride about 0-2 per cent. too high. The most accurate method is to estimate the sulphated ash, and to deduct therefrom the amount of sodium sulphate corresponding to the sodium chloride, the latter being estimated by ignition with calcium oxide and titration by Volhard's method.Finally, a, deduction of 0.09 per cent. is made for the ash of the yeast, and the result is multiplied by the empirical factor $, to obtain the percentage of ash in the dry flour. C. A. M. Test for Cocaine. L. A. Ryan. (J. Amer. Chent. SOC., 1915, 37, 1960.)- M. Goeldner (Zeitsch. anal. Chem., 1901, 40, 820) states that a delicate test for cocaine consists in the formation of a cornflower-blue colour when a trace of thisFOOD AND DRUGS ANALYSIS 443 substance is added to 0.01 grm.of pure resorcinol in the presence of 6 or 7 drops of pure concentrated sulphuric acid. The author fails to confirm this, and finds that if chemically pure sulphuric acid is used, no such colour is developed; but that if the acid is slightly contami- nated with nitrous or nitric acid, the blue colour is formed.So delicate, in fact, is this test that 0*0000001 grm. of nitrogen as potassium nitrate, when evaporated to ,dryness and the residue moistened with chemically pure sulphuric acid, yields a blue coloration on the addition of a trace of solid resorciuol. This reaction would be valuable in detecting traces of nitrate or nitrite in the course of waher analysis.H. F. E. H. Official .Method for Determining Crude Fibre as Applied to Cottonseed Meal. (J. Izcl. and Eng. Chew., 1915, 7, 676-679.)-The dry fat- free residue from 2 grms. of material is boiled for half an hour with 200 C.C. of 1.25 per cent. sulphuric acid, the volume being kept constant by using round-bottomed flasks filled with cold water supported on the top of the beakers.At the end of this time the solution is not filtered, but 200 C.C. of boiling 3.25 per cent. sodium hydroxide are added, and the boiling continued for thirty minutes. I t has been found by experiment that by use of this strength of sodium hydroxide a solution of 1.25 to 1-27 per cent. sodium hydroxide is available for the second boiling, the advantage of this being that one filtration only is eventually necessary.The residual fibre is filtered with the aid of suction on a Buchner filter, and washed with boiling water, followed by a 1.25 per cent. solution of hydrochloric acid until the washings are acid. This treatment is followed by hot water washings continued until free from chlorides, and finally the filter is washed several times with alcohol. The residue on the paper is then transferred with the aid of a small amount of 80 per cent.alcohol to a prepared Gooch crucible, packed with a pad of asbestos about 1 mm. thick, previously heated to redness. The whole is then dried at 105O t o 110’ C . , cooled and weighed, the ash being subsequently deducted. The filter-paper recommended is the No.575 (hard) Schleicher and Schull. It is found that loss of crude fibre may occur when linen is used a8 a filter, while asbestos may lose weight, and thus cause the results to be too low. Schleicher and Schull paper No. 597, when torn into large pieces, dissolves to the extent of about 3.5 per cent. during thirty minutes’ boiling in 1.25 per cent. sodium hydroxide; while this class of paper, if ground so as to pass a 40-mesh sieve, dissolves to the extent of 2-8 per cent.When this filter-paper is boiled in both acid and alcohol, the loss in the case of the larger pieces is 11.5 per cent., and with the powdered paper it rises to 31.5 per cent. A paper of this character is thus quite unsuitable for the separation of the fibre. S.K. Francis. H. F. E. H. Analysis of Pulvis Rhei Cornpositus (Gregory’s Powder). G. D. Elsdon. (Pharm. J., 1915, 95, lOO-lOl.)-According to the British Pharmacopoeia of 1914, Gregory’s powder consists of light magnesia, 66 ; powdered rhubarb root, 22 ; and ground ginger, 12 parbs ; this differs slightly from the formula prescribed in the 1898444 ABSTRACTS OF CHEMICAL PAPERS edition (magnesia, 6 ; rhubarb, 2 ; ginger, l), but the difference is not sufficient t o invalidate the results given below, which were obtained by analysis of the 189% powder.Moisture is estimated by drying the sample at 100' C. ; the loss in weight (not due entirely to moisture) usually varies from 2 to 5 per cent. The ash of the sample consists of magnesium oxide, together with the ash of the rhubarb and ginger ; the calculated ash, allowing 10 per cent.for rhubarb and 5 per cent. for ginger, is 67.5 per cent. Fifteen commercial samples examined gave from 57.1 to 72.5 per cent. The alkalinity of the ash, expressed as MgO, is usually about 4.5 per cent. less than the percentage of ash. Carbon dioxide may be estimated by rinsing 0.5 grm. of the powder into a nitrometer over mercury, adding 5 C.C.of hydrochloric. acid, and reading off the volume of the liberated carbon dioxide; this volume i s corrected for temperature, pressure, and sohbility. The author finds that the solubility varies with the amount of magnesium oxide which has been dissolved, and gives the following table showing the correction to be applied : Grm.of MgO dissolved in 10 c c. of HCl. 0.00 0.15 0.25 0.35 0.50 C.C. of C 0 2 dissolved at 65 F. 7.5 6.3 6.1 5.6 5.1 Gregory's powder should not contain more than 3 per cent. of carbon dioxide, and the presence of more than 5 per cent. must be considered as constitutiug adulteration. The combined amounts of rhubarb and ginger can be obtained approximately from a consideration of the quantities of ash and magnesium oxide in the sample.Confirmation may be obtained as follows: The quantity of water- soluble constituents is estimated by treating 1.2 grms. of the powder with 60 C.C. of cold water for twelve hours, then filtering the mixture, evaporating 50 C.C. of the filtrate, and drying the residue to constant weight. Another portion of 1 grrn. of the powder is treated with 70 C.C.of acetic acid for thirteen hours, the insoluble portion then collected on a filter, washed once with water, and dried. The weight of the insoluble matter, added to the weight of the aqueous extract, after adding 10 per cent. of the total weight for the average moisture in ginger and rhubarb (this figure is very constant), gives the amount of ginger and rhubarb in the sample.This depends on the fact that dilute acetic acid extracts nearly the same amount from rhubarb and ginger as does water, but dissolves the magnesium oxide in addition. The relative amounts of rhubarb and ginger may be found in the following manner: The amount of aqueous extract having been estimated, the alcoholic extract is obtained in a similar way, using industrial methylated spirit of 64 over- proof for the extraction.From the percentage extracts of the sample, the percentage extracts of the combined rhubarb and ginger mixture contained therein may be calculated. Thirty samples of ginger examined by the author gave an average of 13.3 per cent. of aqueous extract, 5.8 per cent. of alcohol extract, the quantities being remarkably constant.The amount of extracts obtained from specimens of rhubarb varied more widely, fifteen samples giving from 30.0 to 44.0 per cent. of aqueous extract,FOOD AND DRUGS ANALYSIS 445 and from 28.8 to 36-4 per cent. of alcohol extract; the average quantities may be taken as being 38.0 and 33.0 per cent., respectively. Taking 38 and 13 as tho percentage aqueous extracts of rhubarb and ginger, and 33 and 6 as the percentage alcohol extracts, respectively, and knowing the aqueous and alcohol extracts of the sample, the composition of the sample may be calculated from either of these figures ; the figures for the alcohol extracts, however, give the more accurate results.w. P. s. Detection of Hydrogen Peroxide in Milk. J. T. Darlington. (J. I d and Eng. Chem., 1915, 7, 676.)-Paraphenylene diamine or benzidine will detect 0.00075 per cent. of hydrogen peroxide in milk, the former being perhaps the more delicate reagent. Titanic acid, vanadic acid, or starch and potassium iodide, will not detect less than 0.003 per cent.After eighteen hours standing at room temperature, hydrogen peroxide can no longer be detected, although it may have been added in large quantity to milk.G. C . J. Estimation of Phenacetin and Salol in Admixture. W. 0. Emery, G. C. Spencer, and C. C. LeFebvre. ( J . Ind. and Eng. Chem., 1915, 7, 681-684.)- Two methods are described. In the first, the phenacetin is converted tetnporarily into phenetidine sulphate by digestion with sulphuric acid, the sulphate is treated with chloroform to remove the salol, then reconverted into phenacetin, and the latter isolated and weighed; the salol is estimated by difference.The second method consists in converting the 551101, by treatment with sodium hydroxide, into sodium salicylate and phenolate, separating the phenacetin by extraction with chloroform, and estimating the salol by titration with bromine. First Method.-If the phenacetin and salol are mixed with other substanct-s in pill or tablet form, a portion of the sample is extracted with chloroform, the chloro- form extract evaporated below 60' C., and the residue weighed.This residue is then treated with 10 C.C. of dilute sulphuric acid (1 : lo), and the mixture heated on a boiling water-bath until the volume of the liquid is reduced to 5 C.C. ; 10 C.C.of water are then added, the liquid evaporated to 5 c.c., and the addition of water and the evaporation again repeated. The residual solution is rinsed into a separa- ting funnel with 20 C.C. of water, and extracted with three successive quantities (15 c.c., 10 c.c., and 5 c.c.) of chloroform; as they are separated, the chloroform extracts are washed with 5 C.C. of water in a second separating funnel.The aqueous solution, to which the wash water is added, is treated with sodium hydrogen carbo- nate in small portions at a tjme until an excess of the latter remains at the bottom of the funnel. Twenty-five C.C. of chloroform are now added, followed by 5 drops of acetic anhydride for every 0.1 grm. of phenscetin known or believed to be present. The mixture is shaken for a short time, the chloroform layer then drawn off into a, separating funnel, washed with 5 C.C.of water, and distilled until about 20 C.C. of chloroform have been collected. This distilled chloroform is used for extracting the mixture a second time, and a third extraction is made in a similar way. The total chloroform extract obtained is evaporated on a water-bath, the residue evapo-446 ABSTRACTS OF CHEMICAL PAPERS rated several times with the addition of small quantities of chloroform, then dried over calcium oxide to remove the last traces of acetic anhydride, and weighed.Second Method-A weighed portion of the mixture, containing not more than 0.1 grm. of salol, is heated on a water-bath for five minutes with 10 C.C. of 2.5 per cent.sodium hydroxide solution; the solution is then cooled rapidly, transferred to a separating funnel, and extracted with three successive quantities of chloroform, using 20 C.C. each time. The chloroform extract is washed with 5 C.C. of water, filtered, evaporated, and the residue of phenacetin weighed, The alkaline aqueous solution is now transferred to a stoppered bottle, diluted with water to about 200 c.c., and a n excess (about 45 c.c.) of potassium bromide-brornate solution and 10 C.C. of con- centrated hydrochloric acid added. The mixture is shaken for one minute, and then at intervals for thirty minutes ; at the end of this time, 10 C.C. of 15 per cent. potassium iodide solution are added, the mixture is shaken for fifteen minutes, and titrated with 7 thiosulphate solution. Twelve atoms of bromine are required for each molecule of salol; therefore each C.C. of bromide-bromate solution corre- sponds with 0*002548 grm. of salol. Results of numerous experiments are recorded, showing that the two methods are trustworthy; in most cases the quantities of phenacetin and salol recovered varied from 99 to 100 per cent. of the amounts present, respectively . w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9154000442

出版商:RSC    

年代:1915

数据来源: RSC

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446 ABSTRACTS OF CHEMICAL PAPERS BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. Culture Media employed for the Bacteriological Examination of Water. 11. : Lactose-Peptone Media. E. M. Chamot and H. W. RedAeld. ( J . Amer. Chem. SOC., 1915, 37, 1949-1958.)-1n the fermentation of lactose by bacteria in water contaminated by sewage, human faeces, the faxes of domestic animals, and pure strains of the B.coZi group, the total volume of gas formed increases to a, final maximum with the concentration of the peptone, meat, liver, or meat extract, employed. The composition of the gas formed is dependent upon the concentration of the nitrogen-containing substance employed. The addition of from 0-5 per cent. to I per cent. of potassium chloride to lactose-peptone media appears to stimulate fermentation and assure more uniform results.Similar beneficial effects are obtainable with sodium chloride, but of not so marked a character. Nothing is to be gained by employing a lactose concentration of over 1 per cent. Neutral media appear to yield slightly greater gas volumes than media, slightly acid to phenolphthalein ; but media, having a reaction of approximately + 1 per cent. ferment considerably more rapidly, and yield diagnostic results in several hours’ shorter time.The gas ratios of the 23. coli group are dependent upon the concentra- tion of the peptone or other similar nitrogenous material in the media. The addition of meat infusion to peptone media is of advantage when low concentrations of peptone are employed, but yields media whose reactions rapidly change.A very sensitive peptone culture medium yielding uniform results and large gas volumes consists of peptone 3 to 4 per cent., lactose 0.8 per cent., potasRium chloride 0.6 per cent. ; reaction + 1 per cent. Such media show little change on keeping. H. F. E. H.BACTERIOLOGICAL, PHY STOLOGICAL, ETC. 447 Detection of Hydrocyanic Acid. P. Lavialle and L.Varenne. ( J . Phamm. Chim., 1915, 12, 74-81.)-The solution containing hydrocyanic acid or alkali cyanides is treated with a slight excess of cold ammonium hydrosulphide gently boiIed for about five minutes, and then evaporated to about 1 C.C. on the water- bath. The residue is taken up with 9 C.C. of water, 10 drops of hydrochloric acid .added, and the liquid shaken with three successive portions (20 c.c., 10 c.c., and 10 c.c.) of ether.The united ethereal extracts are evaporated at the ordinary temperature, and the residue (from which all odour of ether must have dis- appeared) is immediately tested and stirred with ferric chloride solution (French offhinal solution diluted with 9 parts of water). The blood-red coloration of iron thiocyanate will be obtained with solutions which originally contained only 0*00005 grm.of hydrocyanic acid, so that the test is about twenty times as sensitive as the Prussian blue reaction. The iron thiocyanate can be distinguished from irori meconate by being decolorised by 10 per cent. gold chloride solution (cf. Lander and Walden, ANALYST, p. 1911, 36, 266). C. A. M. Toxicity of Various Wood Preservatives.R. M. Fleming and C. J. Humphrey. (J. Ind. and E y . Chem., 1915, 7, 652-658.)-A small sterilised measured quantity of the preparation to be investigated is mixed with a convenient volume of a sterile medium made from lean beef, malt extract, and agar. The mixture is then poured into a Petri dish, and, after cooling, the plates are inoculated in the centre with a preparation of mycelium, 6 mm.square, from cultures of Foms unnosus two to three weeks old. The plates are then incubated at 25' C. for six weeks, and the growth of the culture is measured. The toxicity not only varies with the medium into which the preservative is introduced, but also with the organism, and in general it is found that yeast and moulds are less sensitive to toxic substances than wood-destroying fungi.Fomes annosus was selected because of its very destructive effect upon coniferous wood, particularly in mines ; because of its wide distribution ; and since it grows well on the agar medium employed. The age of the growth employed for the inoculation makes a considerable difference in the activity of its growth on a toxic medium, the advantage always being with the younger culture.Another factor influencing the growth of the organism on the plate is the previous environment of the organism ; for if this has been taken from a toxic medium the subsequent growth of the organism is considerably strengthened, acclimati8ation having rendered the mycelium capable of a more vigorous growth. The results of a large number of experiments are tabulated, for which the original paper must be consulted.Of the wood distillates, the beech-wood creosote proved highly toxic, being two to three times as effective as average coal-tar creosote. Other wood distillates proved to be only one-half to one-third as toxic as coal-tar creosote. The more highly toxic constituents of coal-tar creosote would appear to have their boiling-points between 215" and 305" C., while, of the two water-gas-tar distillates experimented with, the distillate of lowest sp.gr. (0.995) was somewhat less toxic than coal-tar creosote, while that of high sp. gr. (1.042) fell comparatively low in the scale.448 ABSTRACTS OF CHEMICAL PAPERS Zinc sulphate compares very favourably with zinc chloride, and also with coal- tar creosote. When drawing comparisons between zinc chloride and the Bruening and Marmetschke solution (zinc chloride and aluminium sulphate), it should be remembered that zinc chloride cannot be tested satisfactorily by mixing with ordinary nutrient agar, on account of its tendency to combine with the medium. The three petroleum oils tested showed but slight or no toxic qualities, in that generally 40 per cent. cultures nearly equalled, and sometimes even excelled, the growth on the control cultures. H. F. E. H.

ISSN:0003-2654    

DOI:10.1039/AN9154000446

出版商:RSC    

年代:1915

数据来源: RSC

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448 ABSTRACTS OF CHEMICAL PAPERS ORGANIC ANALYSIS. Note on I d e n t i f y i n g Amino-H-Acids. (J. Ind. and Eng. Chem., 1915, 7, 674-675.)-E€-acid is 1,8-amino-napthol-3,6-disulfo acid. There are no published methods of identifying the 2-amino-H-acid, the 7- amino- H-acid, and the 2,7-diamino-H-acid. Ability to detect and differentiate these acids is frequently necessary for industrial purposes in obtaining light on the mode of making and the composition of certain coal-tar dyes.The 2-amino-H-acid was made from H-acid by coupling it in hydrochloric solution with diazotised p-nitraniline (1 mol.), reducing and separating the acid product from the p-phenylene diamine ; the 2,7-diamino-H-acid was made from the foregoing product and a further molecule of diazotised p-nitraniline, coupling in alkaline (carbonate) solution and treating the product a8 outlined below ; 7-aminO- H-acid was made from the coupling product of H-acid and diazotised p-nitraniline (1 mol.), coupled in alkaline (carbonate) solution. This product was reduced and separated as outlined below.B. C. Hesse. The reducing and separating methods mere as follows : One grm. of each of these products was mixed with 10 C.C.water, heated to 60" C., and added to 1 grm. zinc dust suspended in 5 C.C. water, shaken thoroughly, and 5 C.C. of a 36' Be. sodium bisulphite solution added. The whole was shaken thoroughly, then gradually raised to boiling, and maintained at boiling-point until further colour-change failed to take place. It was then filtered rapidly, cooled, and 6 C.C.hydrochloric acid (sp. gr. 1.16) were added to the cooled filtrate. The whole was next cooled in a freezing mixture to 0' C. or below, and maintained at that temperature until no more solid separated (this may take from half an hour to two or three hours), filtered upon paper through a Gooch crucible, and drained thoroughly. The material was washed carefully with small amounts of saturated salt solution; then with as little 95 per cent.ethyl alcohol as possible (3 to 4 c.c.), and finally with 1 or 2 C.C. of ether. The solid was then removed from the filter- paper and dried on a watch-glass at 90° C. The solid so obtained is the amina-H- acid of the coupling product used. The three identification tests used were as follows : 1. A fraction of a mgrm.of the free acid is boiled with a few drops of 40 per cent. caustic soda solution, diluted with 1 C.C. water, and the colour produced noted. I t was found that boiling of the diluted solution wits at times necessary.ORGANIC ANALYSlS 449 2. A fraction of a mgrm. of the free acid is placed in 2 or 3 drops of concentrated H,SO, (sp. gr. 1-84), and warmed until it begins to turn violet ; 1 or 2 drops of 0.5 per cent.sodium nitrite solution are added, and the whole cooled, and then diluted with 0 5 C.C. water. If a brown opalescenco or turbidity appears at this point, the solution has been heated to too high a temperature. The solution is next made alkaline, first with caustic soda in slight excess, and then with saturated carbonate of soda solution, and the colour-changes noted.3. A fraction of a mgrm. of the free acid is dissolved in 1 drop of saturated carbonate of soda solution, heat being used if necessary. One drop of concentrated hydrochloric acid is added, and the solution diluted with water to 0.5 c.c., is heated f o boiling, and cooled. A drop of this is placed on white filter-paper, and a drop or two of hydrogen peroxide solution added.When the colour development has reached its maximum, a drop of 40 per cent. caustic soda solution is added. The colour-changes are then noted. The behaviour of these acids is tabulated as follows : Test. 2-Acid. 7-Acid. 2,7- Acid. I. ... Yellow or brown. Green. Violet going to blue. 11. ... Blue-red. Blue-red. Yellow or brown. 111. H,02 Brown or yellow.Violet to red. Blue. NaOH. ... Red. White or cream- Red to violet. coloured. By suitably combining these tests, it is possible to detect all three of these acids in mixtures of any combination. With care 200 mgrms. of H-acid dye are sufficient to carry out this separation and all three of these tests. The colours produced by Test 111. are unstable and can be photographed--e.g., on a Lumidre plate-and the colours so preserved for reference.H. P. E. H. Separation and Determination of Peptones by their Solubility in Methyl and Ethyl Alcohols. E. Valhuta. (Bull. Acad. Ronzha, 1914-15, 3, 290-300; through J. Chem. SOC., 1915, 108, i. 602-603.)-The peptones resulting from the partial hydrolysis of a number of different proteins obtained from various sources, using Fischer's method, were separated into four fractions, varying i n their solubilities in methyl alcohol.The protein material was added in small quantities to 70 per cent. sulphuric acid at 0" C. with constant stirring, and kept at this temperature for two hours. The mixture was kept for three days at the ordinary temperature with frequent stirring, and then poured into 20 litres of distilled water at 0" C., and the sulpburic acid was just completely precipitated with barium hydroxide.The barium sulphate was filtered off, and the filtrate evaporated to dryness at 36" to 40" C. under reduced pressure (15 mm,). The peptone residue vvas divided into four fractions as follows : The peptone was extracted with hot methyl alcohol and filtered, the insol- uble portion being fraction I.The filtrate on standing for twenty-four hours gave a deposit, fraction II., which was filtered off. The filtrate on dilution with an equal volume of ethyl alcohol gave a further deposit, fraction III., and the filtrate from this on evaporation in a vacuum at 35' to 40° C. left a residue, fraction IV. These four450 ABSTRACTS OF CHEMICAL PAPERS fractions, of which all but the first were invariably easily soluble in water, were tested in aqueous solution by the biuret reaction, Millon's reagent, for cystine, for tryptophane, and for precipitation with the usual protein precipitants.I n addition the ash content was determined and the optical rotation measured. This method was applied to the gluten of wheat, the protein of beef, the protein of fish, the albumin of eggs, the casein of milk, and keratin.The results obtained show that. the peptones bear the mark of their origin. Thus, from proteins rich in cystine or tyrosine, peptones were obtahed also rich in these substances and vice versa. Hydrochloric Acid-Ether Mixture as a Reagent for Rubber Analysis. D. F. Twiss. (India Rubber J., 1915, 50, 199 ; through J.SOC. Chem. Ind., 1915,34, 914.)-The author has employed a mixture of equal volumes of concentrated hydro- chloric acid and ether for the purpose of removing mineral accelerators (PbO, etc.} from partially cured mixings containing high proportions of these substances and free sulphur, in order to be able to estimate with accuracy the originally combined sulphur. If such rnixings be extracted direct with acetone, further combination of the sulphur may occur during the extraction. Two samples, each of 1 to 2 grms.of the rubber, are treated with the mixture of acid and ether until the reagent has completely penetrated the mass. The rubber mass is removed, or the ether is distilled off', and the mass washed in running water and dried, after which it is extracted with acetone.The total sulphur is then estimated in one extracted sarnple and the mineral sulphur (sulphates) in the other. The difference is sulphur in organic combination, which, in the absence of substitute, means sulphur of vulcanisation (c$ Stevens, J. SOC. Chem. Ind., 1915, 34, 724). This takes about a day. Study of Some Recent Methods for Estimation of Total Sulphur in.Rubber. J. B. Tuttle and A. Isaacs. (J. Ind. aizd Eizg. Chcm., 1915, 7, 658-663.). -This paper is published by permission of the Director of the U.S. Bureau of Standards, and describes experiments directed to assess the value of several recent methods in respect of securing greater accuracy or saving time, by comparison. with the method of Waters and Tuttle, which has been in use by the Bureau for four years.This method (J. Ind. and Eng. Chem., 1911, 3, 734) is carried out as follows : The rubber (0.5 grm.) is placed in a large (100 c.c.) porcelain crucible, covered with 20 to 25 C.C. nitric acid saturated with bromine, and allowed t o stand an hour in the covered crucible. The crucible is then gently heated for an hour, the cover removed and rinsed, and the contents evaporated to dryness.About 5 grms. of a mixture in equal proportions of potassium nitrate and sodium carbonate and 3 to 4 C.C. of water are added, the mixture digested for a few seconds on the water-bath, and then spread half-way up the side of the crucible to facilitate drying. When dry, the mixture is fused over a spirit-lamp until all organic matter has been destroyed, and the melt is quite soft.The crucible and contents are cooled, placed in a large beaker, covered with distilled water, and heated on the water-bath for 3 to 4 hours. The solution is filtered and the insoluble matter washed well. To the combined filtrate and wash- ings, amounting to about 500 c.c., 7 or 8 C.C. of hydrochloric acid are added, theINORGANIC ANALYSIS 451 beaker covered, and the mixture heated almost to boiling.If the directions have been followed exactly, the solution will be slightly acid, but it should be tested with Congo red paper and a few drops more acid added if necessary. About 10 C.C. of 10 per cent. barium chloride are added, and the precipitated barium sulphate is filtered off next day, washed, and ignited in such a manner that the paper does not inflame.None of the othsr methods investigated gives results as accurate as those obtained by that above described. The methods of Spence and Young (J. I n d . and Eng. Chem., 1912,4,413) and Deussen (Zeitsch. angew. Chem., 1913,24,494), which depend on direct solution by nitric acid, give low results. The direct fusion methods of Alexander(Gummi Zeit., 1904, 18, 729 ; Allen’s Commercial Organic Analysis, 1911,4, 140), of the Joint Rubber Insulation Committee (J.Ind. a d Eng. Chem., 1914, 5, 78), and of Kaye and Sharp ( I n d i a Rubber J., 1913, 44, 1189), are satisfactory only when the free sulphur content is relatively low. As they are satisfactory in these circumstances, it is suggested that they might perhaps be applied to any class of rubber, after removal of the free sulphur by extraction with acetone. In such cases they would not estimate total sulphur directly, but only that insoluble in acetone, but as the free sulphur is usually estimated in vulcanised goods, the total sulphur would be found without any additional work.The suggestion was not followed up, as none of these methods is appreciably simpler or quicker than that of Waters and Tuttle.The method of Frank and Marckwald (Gummi Zeit., 1903, 17, 71) requires solution and fusion like the method of Waters and Tuttle, but it appears to be untrustworthy when much free sulphur is present. Although not covered by its title, the paper includes criticism of the attempt of some authors to estimate sulphur other than that present as sulphate in the mixing. Spence and Young, Alexander, and Kaye and Sharp, filter from an acid solution, basing their separation on the incorrect assumption that the lead .sulphate originally present will remain insoluble, while that formed from litharge will be dis- solved completely. Deussen filters from an alkaline carbonate solution, overlooking the fact that lead sulphate will react with sodium carbonate, with the formation of soluble sodium sulphate (cf. Gaunt [ANALYST, 1915, 91, Schidrowitx [ibid., 1915, 223.3, and Stevens [ibid., 1915, 2751). G. C. J.

ISSN:0003-2654    

DOI:10.1039/AN9154000448

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

INORGANIC ANALYSIS 451 INORGANIC ANALYSIS. Estimation of Traces of Carbon Monoxide in Air. A. Gautier. (Bull. SOC. Chim., 1915, 17, 256-260.)-1n view of a recent paper by Graham and Winmill (ANALYST, 1914, 39,445) on the estimation of carbon monoxide, the author mentions that he used the iodine pentoxide method for the purpose in the year 1890, and that the reaction had been described by Ditte (BUZZ.SOC. Chim. 1870, 13, [ii.], 318). The author found that the reaction between carbon monoxide and iodine pentoxide commences at 35" C., and is rapid and complete at 75' C.; further, ethylene, acetylene, and the vrtpours of benzene and alcohol, w.hen present in air to the extent of 1 part per 1,000 of air, are oxidised partially by iodine pentoxide, and at the same time interfere with the oxidation of the carbon monoxide.When the gases men-452 ABSTRACTS OF CHEMICAL PAPERS tioned are present in qusntity not exceeding 1 ptrt per 100,000 parts of air, they do not affect the oxidation of the carbon monoxide, nor are they thernselves oxidised to any appreciable ex tent . w. P. s. Standardised Coloured Fluids. H. V. Arny and C. H. Ring. (J. Franklin Inst., 1915, 180, 200-213; through J.SOC. Chem. Ind., 1915, 34, 925.)-To produce solutions of definite tint and colour intensity which can be easily prepared and are more readily accessible than the Lovibond tintometer glasses, the authors suggest Tc solutions of simple metallic salts in acid and ammoniacal solvents respectively. (The cmcentration & in all cases refers to the metal present.) The standard red solution is prepared by dissolving 13.5 grms.of roseo-cobaltic chloride (CoCI,,SN H40 H) in sufficient 2.8 per cent. ammonia solution to make 1 litre. The yellc~zu solution is prepared by dissolving 2.1 grms. of ammonium bichromate in 50 C.C. of 1 per cmt. hydrochloric acid, then adding 50 C.C. of 2.8 per cent. ammonia, solution, and diluting with water to 1 litre. The standard blue solution is made by dissolving 12.486 grms.of copper sulphate crystals in 200 C.C. of water, adding 100 C.C. ol 2.8 per cent. amnionia solution, and diluting with water to 1 litre. Other similar series of blue, yellow, and green solutions are made by dissolving cobalt, iron, and copper salts in dilute hydrochloric acid. Pink tints are obtained from a potassium permanganate solution.I t is stated that practically every tint of colour manifested in fluids can be duplicated by the proper blending of eight standard fluids. In use, the various fluids are mixed in such proportions that the total volume employed is exactly 12 C.C. The volume of any solution in the mixture is always a whole number of C.C. If fractions are required, the standard solutions are diluted to one-fifth of their strength.I t is seldom that more than three solutions are required to match a tint. Although most of the solutions are permanent in colour when blended, it is prefer- able to blend when required. The colour of the separate solutions is stable for more than a year. Estimation of Ferrous Iron in Silicates by Titration with Dichromate.0. L. Barnebey. (J. Anzer. Chem. SOC., 1915, 37,1829-1835.)-Ferrous iron cannot be titrated accurately with dichromate in a hydrofluoric acid solution. Moreover, ferrous iron in fluoride solution oxidises so rapidly that a slow titration, such as accompanies the use of an outside indicator, may introduce a considerable error. If, however, the mineral be dissolved in hydrofluoric and sulphuric (or hydrochloric) acid, with due precaution against oxidation of ferrous fluoride, and excess of boric acid then added so as to convert all fluoride into fluoborate (cf.ANALYST, 1915, 334), the tendency to oxidation by the air is entirely overcome, and the resulting solution can be titrated as exactly with dichromate as if fluorine compounds were absent.Attention is recalled to the fact that the sharpness of the end-point in a titration of ferrous salt with dichromate is seriously interfered wit,h by high concentrations of hydrogen chloride. The author uses a 0.05 per cent. solution of potassium ferri- cyanide as an outside indicator. With this indicator, one drop withdrawn from 200 c . ~ . of a solution, as regards hydrogen chloride, and containing 0.1 C.C.of & ferrousINORGANIC ANALYSIS 453 solution, gives a distinct reaction within a minute. With ten times as high a con- centration of hydrogen chloride, about ten times as high a concentration of ferrous salt is required to give an equally quick development of colour. The absolute error due to this cause is much less when comparatively large quantities of ferrous iron are being titrated, and in such cases the percentage error becomes negligibly small.On the other hand, with small quantities of ferrous iron the error is as stated above -so large relatively that the results are quite worthless. Fortunately the observation that large quantities could be estimated exactly suggested a means of estimating smaller ones with equal accuracy.I t is found that in presence of sufficient ferric chloride (5 C.C. or more of an approximately FG solution in 200 C.C. of the ferrous solution to be titrated) even small quantities of iron can be estimated in presence of $ hydrochloric acid with no greater error than is the ca.se when the acid concen- tration is kept quite low-namely, such an error as corresponds to 0.05 C.C.of & dichromate. G. C. J. Estimation of Lead as Sulphite. G. S. Jamieson. (Amer. J . Sci., 1915, 40,157-160; through J. SOC. Chem. Ind., 1915, 34, 925.)-Lead can be pre- cipitated quantitatively from slightly acid solutions by adding an excess of sodium or ammonium bisulphite or of sulphurous acid, provided that excessive acidity be avoided by addition of ammonia.As an example, 22 C.C. of a solution of lead acetate containing 7.832 grms. P b and 10 grms. of free acetic acid per litre were diluted to about 100 c.c., and treated with an excess of 2 per cent. sodium bisulphite solution, the mixture being well stirred, and allowed to settle for not more than an hour. The precipitate was collected in a Gooch crucible and washed with cold water, without allowing the whole of the liquid to drain until the final washing.After drying at 150" C, the lead sulphite weighed 0.239 grrn., corresponding to 0.1733 grm. P b ; error, - 0.0001 grm. The lead was also precipitated with sulphurous acid containing 36.8 grms. SO, per litre. The addition of sodium acetate is recommended in this case, and a large excess of sulphurous acid must be avoided.The method was successfully applied to mixtures of lead with copper and zinc; it is inapplic- able in presence of the alkaline-earth metals, or of metals which are reduced by sulphites. Separation of Manganese as Manganous Sulphide from Alkali and Alkaline-Earth Metals. V. M. Fischer. (J. Russ. Phys. Chenz. SOC., 1914, 46, 1519-1526 ; through J. Chem. Soc., 1915, 108, ii., 487-489.) - The separation of manganese as sulphide by precipitation with an alkali sulphide in presence of ammonia and ammonium chloride is attended with difficulty, the precipitate being usually the rose-coloured, amorphous form, troublesome to filter and wash, and readily oxidisable in the air.The author, having determined the conditions under which the green sulphide may invariably be obtained in the cold, gives the following method for separating manganese as sulphide from solutions containing metals of the alkalis and alkaline earths.To 100 to 200 C.C. of the liquid are added 5 to 15 grms. of ammonium chloride and 50 to 60 C.C. of ammonia solution (sp. gr. at454 A BSTRACTY OF CHEMICAL PAPERS 16' C. 0,895) ; the solution should remain perfectly clear.From a dropping funnel with an orifice 0-75 mm. in diameter 50 to 100 C.C. of ammonium hydrogen sulphide solution freshly prepared from 2.5 per cent. ammonia solution are slowly added, the addition occupying ten to fifteen miniites, and the vessel being meanwhile constantly and vigorously shaken. Conversion of the flesh-coloured manganese sulphide into the green variety proceeds during the addition of the precipitant, and, when it is not irninediately completed, the Erlenmeyer flask should be corked ; the change occupies from a quarter to one and a, half hours, according to the proportion of ammonium chloride present and the rapidity of the precipitation.When all the precipitate is green, the liquid is diluted to 500 to 700 C.C.with cold, recently boiled water, and filtered. The precipitate is washed with dilute ammonium hydrogen sulphide solution containing a, little ammonium chloride, and is subsequently either heated with sulphur in a current of hydrogen and weighed as gulphide, or dissolved in dilute hydrochloric acid and converted into phosphate. This method yields very accurate results, and, as it is not affected by the presence of ammonium acetate, it is applicable after the removal of the iron by the acetate method.When sufficient ammonia is present, and the precipitation is effected slowly, it becomes unnecessary to convert the rose-coloured into the green sulphide, since the former is then obtained in a dense form, which can be readily filtered and washed, and does not undergo oxidation.I n this cme the following quantities should be used : 150 to 200 C.C. of solution, 5 to 10 grnm of ammonium chloride, 50 to 75 C.C. of ammonia solution, and 75 to 100 C.C. of the cold ammonium hydrogen sulphide solution. After diluting with 500 to 1,000 C.C. of cold, boiled water, the precipitate usually settles rapidly, leaving the supernatant liquid clear ; filtration, etc., may then be carried out imme- diately.If, however, the liquid remains turbid, the precipitate is allowed to change into the green form before filtration. Either procedure gives excellent results, which are not affected by the presence in the solution of hydroxylarnine hydrochloride (ZOC. cit.). Method for Controlling or Estimating the Quantity of Nickel Deposited during Nickel Plating.M. Pontio. (Comptes rend., 1915, 161, 175-177.)-The spot-test described depends on the action of a, mixture of mineral acids and hydrogen peroxide on the nickel-plated object. The reagent used is prepared by mixing 10 C.C. of nitric acid (sp. gr. 1.332), 20 c.cI of hydrochloric acid (sp. gr. 1*18), 20 C.C. of hydrogen peroxide (12 vol.), and 50 C.C. of water.The plated object to be tested is dipped for a few seconds in concentrated sulphuric acid, next washed with water, dried with a clean linen cioth, and a drop of the reagent is applied to the surface. After two minutes' contact 1 drop of ammonia is added, and, after the lapse of another minute, the drop is poured from the metal on to a porcelain slab. If it exhibits a blue coloration, the quantity of nickel deposited on the surface, in the case of a copper base, is less than 1 mgrm. per sq.cin. Iron previously coated with copper, and then nickel-plated, will give a brown coloration with the test if the nickel coating is less than 4 mgrrns. per sq. cm. I n cases of doubt, the blue copper coloration may be confirmed by the ferrocyanitle test. w. P. s,APPARATUS, ETC.455 Estimation of Sulphates in Soils. P. E. Brown and E. H. Kellogg. (J. 1w-L and Eng. Chem., 1915, 7, 686-687.)-Attempts to extract sulphates from soil by means of hydrochloric acid lead to inaccurate results, which may be high or low. Gemerally with low concentrations of acid the results are low, probably because of the interference of ferric oxide and organic matter (cf. Van Bemmelen, Landzl:. Vers. Sta., 37, 284). With 2 per cent. of acid the sulphates may be under-estimated by as much as 70 per cent. On the other hand, with 10 per cent. of acid they may be over-estimated by a8 much as 50 per cent., unless means be adopted to separate silica before proceeding to the precipitation of sulphate as barium sulphate. If this source of error be eliminated, the results will be as low as when weaker acid is used for the extraction. It is found that water is an excellent solvent. I t is recom- mended to shake the soil with twice its weight of water for six to eight hours. A shorter period may suffice with some soils, but not if much calcium sulphate is present. Hydrated calcium sulphate, when added to soils in proportions much greater than those commonly obtaining, is completely extracted in eight hours. G. C. J.

ISSN:0003-2654    

DOI:10.1039/AN9154000451

出版商:RSC    

年代:1915

数据来源: RSC

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APPARATUS, ETC. 455 APPARATUS, ETC. Pipette for Calibrating Burettes, and Discussion of Principles under- lying the Calibration and Use of such Pipettes. C. W. Foulk. ( J . Ind. and Eng. Chm., 1915, 7, 689-693.)--The essential novelty consists in making the two-way stopcock the zero point of the instrument instead of having a mark on the lower stem of the pipette. The pipette itself is calibrated by weighing the quantity of water delivered by it under the same conditions as those obtaining during use.The pipette illustrated is of approxi- mately 5 C.C. capaciby, and is intended for use in cali- brating 50 C.C. burettes. The outlet orifice is constricted to small dimensions, and then filed until the pipette in a vertical position discharges itself in fifteen to sixty seconds (the specification of the Bureau of Standards for 5 C.C.pipettes). ‘The orifices of the burettes to be standardised are similarly adjusted until they comply with the speci- fication of the Bureau, which requires a burette of 50 cm. scale lengtli (about that of a 50 C.C. burette) to discharge in one and a half to three minutes. C being full, the cork is inserted, and then the tip of a filled burette.No air is thus trapped. Water is allowed to rise in F to the mark B and the water-level in the burette is adjusted to zero. The water in F is run off through the stopcock. Nine or ten pipettefuls are next run off from the burette, according as a tenth would take tho level of the water i i i the burette below the male or not. Only the final reading is needed to calibrate the pipette, but readings should be taken after each pipetteful is withdrawn, to 8456 ABSTRACTS OF CHEMICAL PAPERS make the time allowed for drainage equal to that allowed when using the pipette.Moreover, if the burette is an uncalibrated one, as it may be, this provides one set, of numbers towards the construction of a calibration curve. Suppose the reading after the ninth withdrawal 45.2 c.c., the burette is refilled to the zero mark, the pipette disconnected, and the contents of the burette down to the 45.2 C.C.mark discharged into a tared flask. From the weight of this water and its tempera- ture, its volume is calculated, and the capacity of the pipette in use is clearly one- ninth of this. The use of the pipette need not be described.I t is not worth while to expend time in trying to make it of exactly 5 C.C. capacity, but it is convenient to have it closely approximate this. G. C. J. Paraffined Apparatus for Volumetric Analyses. G. Povarnin. (J. Rim. Phgs. Chem. Soc., 1914, 46,1898-1905 ; through J. Chem. SOG., 1915,108, ii., 477-478.) -The author recommends that the measuring vessels, bottles for stock solutions, etc., used in volumetric analysis, be coated internally with a thin layer of paraffin wax.Perfectly white, crystalline paraffin wax, m.-pt. 55" C., should be employed, and, befora use, should be freed from any mechanical admixtures by fusion and decantation, or by filtration through a hot filter. The use of solutions of the wax in commercial amyl acetate, ether, or chloroform does not give good results. The ordinary dilute solutions employed in volumetric analysis are without action on the wax, and wet it very slightly indeed; this slight wetting seems to be continued by the inclusion of water by minute crystals of the paraffin wax. The general advan- tages of paraffined apparatus are that the necessity of keeping the interior of measuring vessels free from fatty matter is avoided, and that water-vapour from standard solutions does not condense on the upper parts of the vessels.Paraffined pipettes deliver completely and rapidly, and in general need not be washed out during use. Solutions of alkali hydroxide do not change in titre when stored in paraffined bottles. With iodine solutions or alcoholic alkali solutions, paraffined vessels cannot be employed.The filling of burettes is best effected from the bottom, fiince with the ordinary constant-level burettes filled from the top air-bubbles remain attached to the wttlls; this difficulty is, however, avoided by bending the delivery- tube so as to deliver the liquid against the side of the burette, and by filling the latter slowly. The correction 'for the volume occupied by the wax coating is about 0.0033 C.C.per 1 C.C. The height of the liquid, which is read at once, without waiting for the solution to drain from the walls of the burette, is determined, not by means of the meniscus, but at the line of contact of the liquid with the wax ; an accuracy of 0.01 C.C. is easily attainable, but, owing to the slight wetting of the coating, this may be diminished to about 0.02 C.C.The size of a drop is rendered far more constant by the layer of wax. It is advantageous to coat the upper two-thirds of the inner surface of the Erlenmeyer flasks used for titration. Measuring cylinders, when treated in this way, deliver their contents quantitatively. Measuring flasks should be coated over a space on each side of the mark, or, if they are to be used as pipettes, over the whole of the inner surface. Owing to the increased ease and speed with which waxed burettes and pipettes are manipulated, their use is of particular advantage in technical laboratories where large numbers of analyses are carried out.

ISSN:0003-2654    

DOI:10.1039/AN9154000455

出版商:RSC    

年代:1915

数据来源: RSC

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REPORTS 457 REPORTS. Metropolitan Water Board. Eighth Annual Report of the Director of Water Examination. A. C. Houston. April, 1914. (Published by the Board, price 2s. 6d.)-The most notable event during the year was the recurrence of algal trouble in the Staines reservoirs, due on this occasion to the growth of Asterionella, which rendered the water almost unfilterable. The remedy used was to treat the water with copper sulphate and to dilute it largely with raw river water.I n addition to the usual oxygen absorption test for three hours at 80” F., corresponding tests for four hours were made over a considerable period ; the results of the latter were 5 per cent. higher. In the case of unsatisfactory waters there was found to be a striking parallelism between the results of a five minutes’ oxygen absorption test and the usual three hours’ test. Taking 0.1 part per 100,000 as the basis for objecting to the quality of a water on the three hours’ test, the correspond- ing figure for the five minutes’ test was found to be 0,038.This test serves as an index to the probable quality of the water, and, when unsatisfactory, enables a communication to be made to the district concerned on the same day as the collection of the sample.The bacterial count on bile-salt agar, which the author considers to be the most reliable count for indicating undesirable organisms, had been confined previously to the raw river water, but was extended during the year to the filtered waters. The number of bacteria found in these latter samples on this medium averaged less than 1 per C.C.The result of the test is most reliable in winter ; occasionally in summer higher results are obtained, but the colonies are not of a typical appearance, and there may be a growth of bacteria in the water which are not necessarily of intestinal origin. I n returning the average number of bacteria in the raw river water, it has been customary to include all the results in the average, but at times of high flood counts of 25,000 have been obtained, and it is considered that if these high results were excluded, a more accurate average figure would be obtained.Also, as there is no reason why the intakes should not be closed at these times of high flood, the exclusive average figure would more truly reflect the quality of the water abstracted.Full tables with details of the chemical and bacteriological results for the raw and filtered waters throughout the year are given. It is considered that the means now adopted for the purification of the supply are such as to render the water reasonably, if not absolutely, safe for drinking purposes. J. H. J , Metropolitan Water Board. Eleventh Report on Research Work.A. C. Houston. (Published by the Board, price 2s. 6d.)-Two subjects are treated in this Report, the first being the author’s excess lime method of purifi- cation. This has been put into operation on a practical scale, and to Aberdeeu belongs the credit of being the first in this country to show that the laboratory ex- periments could be applied to the supply of 165,000 people, and applied success- fully.The water-supply is derived from the very soft water of the River Dee, and no attempt was made to remove the excess of lime before consumption of the water.4 58 REPORTS The amount of lime added was 3 parts per 100,000, and the water after treatment contained 2.17 parts of free lime i n solution and 0.45 part of carbonate of lime in suspension.B. coli were usually present in as little as 1 C.C. of the water when untreated, and were practically always absent from 100 C.C. during treatment. As a result of this temporary treatment, the Corporation has decided to adopt a permanent scheme based on this principle. The process has been applied to a hard river water at Sunbury-on-Tharnee-, and a detailed account of this experiment is given.About 168,000 gallons were treated daily with quicklime, at the rate of 2,000 pounds per 1,000,000 gallone, and three days’ contact in two settling tanks was allowed. The caustic alkalinity of the water after settlement was 6.86 parts per 100,000, and to neutralise this, stored river water was added in a third tank in the proportion of 4 : 1, and about three hours’ contact allowed.The water wai3 then passed through an ordinar sand filter. The resulting water on chemical analysis compared favourably with the ordinary supply to the Metropolis, and also B. coli mere never present. The author has no hesitation in expressing the opinion that river water, no matter how impure, can be brought to a condition of absolute safety bacteriologically, and of great relative purity chemically, by means of the excess lime treatment.The second subject dealt with in the Rgport was suggested by the ‘‘ world-wide war now raging,” which increases the risk oE epidemic water-borne disease ; and the author has made a further study of water organisms liable to bs mistaken for the true cholera vibrio. Peptone water cultures were made with 10 to 50 C.C.of London water, and the growth subcultured on agar. Likely colonies were inoculated into peptone water, and after twenty-four hours’ growth these cultures were tested for the cholera-red reaction. Out of 1,583 colonies, 80 gave the reaction, and kherefore required further study. Gelatine shake cultures were made, and 13 gave no gas, aud so were provisionally accepbed. These were then tested for liquefaction, and 5 ghve positive results. These were then grown in peptone water for forty-eight hours, and all failed to give the cholera-red reaction a second time; they were, therefore, not the true cholera vibrio. At the end of the Report is given an index to the author’s first ten Research Reports published during the last twelve years. The index refers in great detail to all the points treated in the Reports, and will be of great use to ofher workers who wish to consult them. J. H. J. + + + + + No complaints were received. Y

ISSN:0003-2654    

DOI:10.1039/AN9154000457

出版商:RSC    

年代:1915

数据来源: RSC

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4 58 REPORTS REVIEWS. THE ANALYSIS OF DYESTUFFS AXW THEIE IDENTIFICATION IN DYED AND COLOU~ED MATERIALS, LAKE-PIGMEKTS, FOODSTUFFS, ETC. By ARTHUK G. GREEN, M.Sc., F.R.S., F.I.C. London: Charles Griffin and Co., Ltd. Price 8s. 6d. net. The appearance of this book is to be especially welcomed now that a determined effort is being made to place the manufacture of dyes in this country upon a firm basis, and Professor Green is to be congratulated on his lucid presentation of the masterly series of investigations which he has carried out during the past twentyREVIEWS 459 years.The valuable analytical tables, however, by no means exhaust the scope of this book. A short introductory chapter explains in simple language the general chemical characteristics of dyes, and succeeding chapters are concerned with a clear account of the classification of dyes both from the chemical and the dyeing point of view.Then follow the author’s schemes for the analysis of dyes in substance, and their identification on animal and vegetable fibres as well as in foods. I n a special chapter the analysis of indigo, both in substance and on the fibre, is discussed, and in another the analysis of pigments and lakes is dealt with.The last chapter-on the determination of the constitution of azo dyes-is concerned with the isolation and characterisation of the cleavage products of azo dyes obtained by the processes of reduction and nitration, and is particularly interesting. I n spite of the rapid increase i n the number of dyes that have been put on the market, Professor Green’s book is not one that will soon be out of date, for his analytical schemes are elastic, and allow of new dyes being rapidly classified, so that the groups to which they may belong are soon ascertainable.The book is well printed, and is singularly free from errors; the only one that was noticed was the phrase, (( To affect this transference ” (p.63), where “ affect ” should obviously be ( ( effect.” The style is straightforward and clear, and the unfortunate tendency that one notices in some chemical books of using a Germanic phraseology is here absent. One might perhaps suggest (p. 99) that the sentence, “These are formaldehyde condensation products of primary nitroamines,” would be better rendered, (( These are products of the condensation of formaldehyde with primary nitroamines.” There is no doubt that the analyst, as well as the manufacturer and the user of dyestuffs, will find it necessary to have Professor Green’s monograph on his shelves.J. C. CAIN. AIR, WATER, AND FOOD. Fnoar A SANlTARY STANDPOINT. By A. G. WOODMAN and J. F. NORTON, Massachusetts Institute of Technologi. Fourth Edition.Revised and Rewritten. 1914. John Wiley and Sons. London : Chapman and Hall. Since the last edition of this book was published in 1909 one of the original authors-Mrs. Ellen Richards-has died, and the entire volume has been largely rewritten, more particdarly the sections on air, water, and milk. Originally written from a ‘( missionary ” standpoint, its employment for college and technical school teaching has necessitated considerable modification in the character of part of the general discussion, and it is probable that the book has gained in consequence.For all detailed discussions and analytical methods the reader is referred to such writers as Wiley, Allen, and Leach, the present work being intended ‘( for the student who needs to study, as part of general education, only typical substances, and such methods as can be carried out within the limits of laboratory exercises in a college curriculum.” The standpoint of the authom cannot be better expressed than in their own words, which run as follows : c c The day is not far distant when a city will be held as responsible for the purity of the air in its schoolhouses, the cleanliness of the water in its reservoirs, and the reliability of the food sold in its markets as it is now Price 8s.6d. net.460 REVIEWS for the conditions of its streets and bridges. Nor will the years be many before educational institutions will be held as responsible for the condition of the bodies as of the minds of the pupils committed to their care ; when a Chair of Sanitary Science will be considered as important as a Chair of Greek or Mathematics; when the competency of the food purveyor will have as much weight with intelligent patrons as the scholarly reputation of any member of the faculty.” A most praiseworthy attempt has been made in the work under review to bring about these admittedly desirable results, and in the short space available for the task a valuable sketch has been attempted of methods employed in the examination of air, water, beverages, and food products, while their adulteration and sophistication also receive useful attention.On the whole, a wise discrimination has been displayed in the choice of the analytical methods described ; and the student who has worked through ‘even some of them, will, if he derives no other advantage, at least be well on the way towards realising the complexity of the problems which face the modern food chemist when confronted with the genuine article or with the products of the ingenuity of the professional sophisticator and mis-brander.” A curious error has crept into the section on beer, in which it is stated that “ the extract of beer cannot be accurately determined by evaporation and drying at 100” C., because of the dehydration of the maltose ’’ ; while serious exception must be taken to the “ simple analytical scheme due to Sherman ” (‘‘ Methods of Organic Analysis,” second edition, p.341) for the analysis of malted cereals, described on p. 189.) On p. 6, a printer’s error’ has resulted in attributing to corn a carbohydrate maxzmum of 52 per cent. and a minimum of 72-7 per cent. Useful appendices of tabulated matter, a very full bibliography, and an index, complete this stimulating and very readable volume. HENRY F. EVERARD HULTON.

ISSN:0003-2654    

DOI:10.1039/AN9154000458

出版商:RSC    

年代:1915

数据来源: RSC