摘要:

SEPTEMBER, 1915. Vol. XL., No. 474. THE ANALYST. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS. NOTE ON THE APPARENT SPECIFIC VOLUMES OF ALCOHOL IN AQUEOUS MIXTURES OF VARYING CONCENTRATION. BY HORACE T. BROWN, LL.D., F.R.S., F.I.C. DURING a recent inquiry into the scientific principles underlying the methods for determining the original gravity " of beer it became necessary to study the changes in volume which saccharine solutions undergo during alcoholic fermentation.In the course of this inquiry I had occasion to examine the progressive volume changes which accompany the dilution of alcohol by water in mixtures of comparatively low sp. gr. corresponding to concentrations of from about 7.0 per cent. of alcohol down- wards. The first dificulty experienced was in finding any alcohol tables of a, suffi- cient degree of accuracy for my purpose ; but through the courtesy of Sir Edward Thorpe I received from him an advance copy of the requisite portion of his new alcohol tables which have quite recently been published in extenso (see p.424). These data amply satisfied my requirements, and enabled me to calculate with a high degree of accuracy the variations in the apparent specific volume of alcohol in mixtures lying between the densities of 0.988 and 0.999 at 15.6"/15-6" C.The progressive changes of volume which occur during the dilution of a solution of a solid in water, or of a mixture such as that of alcohol and water, can be most conveniently studied by assuming that the resulting contraction or expansion, as the case may be, only affects one of the constituents.For instance, in the case of a solution of sugar we may agree to throw all the observed volume changes on the solute, and to consider the solvent as taking no part in them, but remaining constant in density throughout. Observations of the progressive influence of dilution thus resoIve themselves into a determination of the apparent specific volume of the solute a t varying but known concentrations.The only data required are (a) the concentration of the solutions before and after dilution-Le., the actual weight of the solute in unit volume in the two cases; and ( b ) the densities of the two solutions before and after dilution. The application of the foregoing principles to mixtures of alcohol and water will be better understood from a concrete example, using the grm.as the unit of weight and the cubic centimetre as the unit of volume.380 BROWN: NOTE ON THE APPARENT SPECIFIC VOLUMES OF A mixture of alcohol and water having a density of 0.880 at 15.6°/15*60 C. contains, according to the Thorpe Tables, 66.66 per cent, of absolute alcohol by weight, therefore the weight of alcohol in unit volume is 0.880 x .6666=0*5866 grm., and the weight of water in unit volume is 0.880 - 0.5866= 0,2934 grm.Since we have agreed to refer all the changes of volume to the alcohol, the apparent volume occupied by the alcohol is represented by 1 - 0.2934 = 0.7066 C.C. The apparent specific volume of the alcohol at sp. gr. 0.880-that is to say, the volume occupied by unit weight-is therefore represented by In the same manner it can be shown that the apparent specific voluine of The apparent specific volume of alcohol in all concentrations may be expressed alcohol at density 0.900 has diminished to 1.1913.by the following formula : l - ( D - W ) W ' ~ _ _ where D is the density of the mixture at 15-6°/15-60 C. and W the weight of alcohol in grm.in 1 C.C. The value of W is of course readily obtainable from the tables by multiplying the density by the percentage weight of alcohol, and dividing by 100. When applying these principles some time ago to alcoholic mixtures of low concentration, corresponding to densities of )0*988 to 0.999, I obtained some un- expected results to which I have called attention elsewhere (see J.Inst. of Brewing, 1914, 11, 712). They are given in the following table, which shows the variation of the specific volume of alcohol within the above limits of density of the mixtures : TABLE I. Specific Gravity of Mixture at 15*6"/15-6" C, 0*988 0.989 0.990 0.991 0.992 0,993 0.994 0.995 0.996 0-997 0.998 0.999 Apparent Specific Volume of Contained Almhol.1.1713 1.1732 1.1750 1.1770 1.1788 1-1807 1.1818 1.1834 1.1850 1.1862 1.1874 1.1890 It will be seen that within this range of densities the apparent specific voliirne of the contained alcohol steadily increases with the dilution. It follows from this that on progressive dilution within these limits the volume of the mixture must exceed the sum of the initial volumes of the constituents-that, in fact, under these conditions there is an expansion of volume instead of a contraction such as is observed when stronger spirits are diluted.ALCOHOL IN AQUEOUS MIXTURES OF VARYING CONCEXTRBTION 38 1 At the time when these sbservations were made I had not access to the f d Alcoholometric Tables of Sir Edward Thorpe, but their publication has now enabled me to carry the inquiry farther, and to ascertain the critical point at which dilution ceases to produce contraction and begins to give rise to expansion.In order to maintain the requisite calculations within reasonable bounda I commenced by a process of approximation, using in the first place somewhat wide intervals of density, and gradually reducing these intervals between successive degrees of alcoholic concentration as the position of the critical point was more nearly reached.Table 11. records the results between sp. gr. 0.850 and 0.990 at density intervals of 0.010. TABLE 11. Showing the First Approximation to the Critical Point for Diferemes of Speci;fic Gravity of 0.010. Specific Gravity at 15.6O/15-6O C. 0.8500 0.8600 0.8700 0:8800 0.8900 0-9000 0.9100 0.9200 0-9300 0.9400 0.9500 0.9600 0.9700 0.9800 0.9900 Apparent Specific Volume of Alcohol. 1.222 1.217 1.211 1.204 1.198 1491 ld8P 1.177 1.160 10153 1.147 1.146 1.156 1,175 1.~169 Differences of Specific Volumes.- 0.005 - 0.006 - 0.007 - 0.006 - 0.007 - 0.007 - 0.007 - 0.008 - 0.009 - 0.007 - 0.006 - 0.001 + 0*010 + 0.019 - Froin the above tableit will be seen that in this first approximation there is a, steady decrease in the specific volume of the contained alcohol until a density of 0.960 is reached.Between this point and sp. gr. 0.970 the specific volume decreases much less rapidly, and beyond sp. gr. 0-970 the specific volume begins to increase, and continues to do so as the density increases. The table on p. 382 gives the result of a still closer approximation to the critical point, being calculated for sp.gr. of dilute spirit lying between 0.9500 and 0.9980 and with progressive intervals of density of 0-002. This further approximation to hhe true critical point, where, on further dilution contraction ceases and expansion begins, shows that it must lie somewhere between the densities 0.9640 and 0.9680. In carrying out the inquiry still further it was necessary to take still smaller intervals of density above and below about sp.gr. 0.9660, and to calculate the values of the corresponding specific volumes beyond the third place of decimals. The intervals of density chosen were 0.0002, the limit of the Alcoholometric Table used382 BROWN: NOTE ON THE APPARENT SPECIFIC VOLUMES OF without interpolation, and the specific volumes of the contained alcohol were estimated to the fifth place of decimals.It was expected that this was attempting 8 degree of refinement which the Thorpe Table would scarcely sustain ; that it does continue to give consistent results under these circumstances is strong evidence of its high degree of accuracy. TABLE 111. Showing the Apparent Specafic Volzlmes of Alcohol in Aqueous Mixtures lying between 0*9500 and 0.9980, with Diferences of Density of 0.002.Bpecific Gravit at 15 '6'11 5.6" 8. 0.9500 0.9520 0.9540 0.9560 0.9580 0.9600 0.9620 0.9640 0.9660 0.9680 0.9700 0.9720 0 -9 740 0.9760 0.9780 0.9800 0.9820 0.9840 0-9860 0.9880 0 p9900 0.9920 0.9940 0.9960 0.9980 Apparent Specific Volume of Contained Alcohol. 1.153 1.151 1.150 1.149 1-148 1.147 1.146 1.145 1-1-45 1.145 1.146 1.147 1.149 1-151 1.153 1.156 1-160 1-164 1.167 1-171 1.175 1.179 1.182 1.185 1.188 Differences.- - 0.002 - 0.001 - 0*001 - 0.001 - 0.001 - 0~001 - 0*001 + 0.001 + 0.001 + 0.002 + 0.002 + 0.002 + 0.003 + 0.004 + 0.004 + 0.003 + 0-004 + 09004 + 0.004 + 0.003 + 0-003 + 0.003 0 0 The minimum specific volume of 1.14520 occurs at a point corresponding to a sp.gr. of 0.9652, but the values show some slight irregularity between 0-9648 and 0.9652. The critical point where progressive dilution begins to produce expansion instead of contraction must lie somewhere very near a sp. gr. of 0.9652. We may now ask what is the meaning of this critical point, and what is its physical significance? The first explanation to suggest itself is that it marks the completed formation of some definite hydrate of alcohol, during the formation of which continuous contraction takes place, and that the expansion which occurs on still further dilution is an expreasion of progressive dissociation of this hydrate.That this is, in the main, the true explanation of the phenomenon is rendered probable by the fact that at the critical point the percentage weight of alcohol in the mixture corresponds closely with a combination of 1 molecule of alcohol with 8 molecules of water.ALCOHOL IN AQUEOUS MIXTURES OE" VARYING CONCENTRATION 383 TABLE IV.Apparent Specific Volumes of Alcohol in Aqueous Nixtures between the Densities 0.9640 and 0-9666 for Diferences of Density of 0*0002. Specific Gravity a t 15'6"/15-6" C.0-9640 0,9642 0.9644 0.9646 0.9648 0-9650 0.9652 0.9654 0.9656 0.9658 0.9660 0.9662 0.9664 0-9666 Apparent Specific Volume of Contained Alcohol. 1.14545 1.14541 1.14536 1.14532 1.14524 1.14525 1.14520 1.14521 1 -1 45 23 1.14524 1.14526 1.1 45 2 7 1.14529 1.14531 Differences. - - 0.00004 - 0.00005 - 0.00004 + 0*00001 - 0.00005) + 0~00001 + 0~00002 + 0~00001 + 0~00002 + 0~00001 + 0~00002 + 0*00002 - 0*00008~ A hydrate having the composition C2H,O+8H,O would contain 24.21 per cent.of alcohol, whereas dilute alcohol of sp. gr. 0.9652 c.c., at the critical point, contains 24-83 per cent. of alcohol by weight, This explanation would also account for the slight irregularities in the specific volumes very near the critical point-irregularities which can scarcely be due to any faults in the table, unless we imagine a coincidence of a very remarkable kind.They are more likely due to a dynamic want of stability very near the critical point, when the slightest variation in temperature or pressure may cause very small oscillations of the critical point on either side of a mean position. Possibly, on further examination, which I hope the publication of this Note may suggest, it may be found that some other physical properties of mixtures of alcohol and water may be correlated with the one to which I have drawn attention. Many years ago Dupr6 and Page found that up to about 30 per cent. of alcohol the specific heat of spirit is higher than that of water, and that the highest specific heat observed, 104.362 (water= loo), lies somewhere in the neighbourhood of 20 per cent. by weight. This fact was subsequently confirmed by Schuller. Duprh and Page also found that the compressibility of mixtures of alcohol and water decreased with increasing concentration of alcohol up to a point between 20 to 30 per cent. of alcohol, and then increased again.

ISSN:0003-2654    

DOI:10.1039/AN9154000379

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

384 NORTHALL-LAURIE A NEW METHOD FOR THE A NEW METHOD FOR THE DETERMINATION OF TOLUENE IN COMMERCIAL TOLUOLS. BY D. NORTHALL-LAURIE F.I.C. (Published by permission of the Controller of H.M. Stationery Ofice.) Theoretical Consideratiom.-When a mixture of two chemically similar substances infinitely miscible such as benzene and toluene and which do not form a mixture of constant boiling-point are boiled the relation between the molecular composition of the vapour and the molecular composition of the mixture is constant and can be expressed by the equation where XI end X are the relative masses of the constituents in vapour W1 and W2 the relative masses of the constituents in the liquid and C a constant which is usually a ratio of the vapour pressures. AS the constituent of lower boiling-point boils off the percentage of the higher boiling-point conetituent rises and so does the boiling-point of the mixture the composition of the vapour changing in the same manner I t thus follows that if a mixture of benzene and toluene is distilled at a uniform rate in a flask without still-head condensation into an efficient condenser the composition of the first drop condensed will be equal to the composition of the vapour and as distillation proceeds, the percentage compoaition of the distillate will be in inverse ratio to that of the mixture distilling.If half the mixture is distilled in the above manner and assuming equal quantities of each constituent present in the mixture the benzene will be in excess in the fraction distilled and toluene in excess in the residue.Again if the relationship between the percentage composition of the constituents to the boiling-point is known the amount of each constituent in the fractions can be easily determined. Mixtures of benzene and toluene toluene and xylene of known composition by volume were prepared and their boiling-poilits noted. These were plotted against the percentages and a curve drawn from which the composition by volume for all boiling-points could be read off. Mixtures of the three homologues will behave under distillation oonditions in a similar manner but in this case the relationship between the percentages of the constituents in the fractions is more complicated. In this case two fractions must be collected. The benzene will then be in excess in the first fraction the toluene in the second and the xylene in the residue; there being a proportion of the three homologues in each fraction this proportion varying according to the percentage composition of the original liquid, As the three isomers of xylene occur in commercial xylene and as the percentage of each isomer varies in different samples slightly varying boiling-points will be obtained in practice.I find however owing to the boiling-points of the three isomers being so close-namely 143" 1 3 9 O and 138" C.-the error due to taking on DETERMINATION OF TOLUENE IN COMMERCIAL TOLUOLS 385 fixed boiling-point does not affect the results in any marked degree. A more complete separation of the mixture into its three constituents would be obtained by using an evaporator still-head and collecting the fractions up to 110-6" and 139" C.instead of in equal amounts. This is of course the procedure adopted in fractional distillation. I t is thus seen that plain distillation tends to separate the three constituents, fractional distillation giving a more complete separation. However any method of analysis depending on fractional distillation is tedious and likely to be unreliable unless conducted with great care. Consequently if sufficient separation of the constituents is obtained by plain distillation into three fractions so as to give first and last fractions of markedly different boiling-point a, method of determining toluene would be possible. After a considerable number of experiments I have devised a practical method depending upon the principles above cited.Method.-A known volume of the sample is distilled at a uniform rate from a distilling4 ask into an efficient condenser. As soon as one quarter of the volume has collected the receiver is changed and a further half distilled over. The distillation is then stopped. The boiling-points of the first fraction and the last-namely the residue in the flask-are then taken in an apparatus of special design. On reference to a table or graph prepared as a result of experiment with known mixtures the quantity of toIuene is read off. This method depending upon the collection of fractions always of the same quantity and noting the boiling-point has advantages over the alternative method of collecting fractions to a definite temperature and measuring them inasmuch as in cases where there is a predominating amount of one constituent the quantity of one or more of the fractions would be small and difficult to measure accurately.Boiling-Point Apparatus,-The boiling-point apparatus required for use in taking the boiling-point of the fractions is shown in the sketch on p. 386. This can be easily constructed from a distilling-flask. In the neck of the flask is placed a thin glass cylinder with a hole in the side corresponding to the outlet of the neck of the flask and sealed to its sides. This glass screen protects the bulb of the thermometer and insures a steady temperature preventing variations from draughts or other causes. Process.-Two hundred C.C. of the sample measured at tap-water temperature are placed in a distilling-flask of just sufficient capacity with the neck cut off close above the side tube The contents are distilled at the uniform rate of 7 C.C.per minute through an efficient condenser into a 50 C.C. measuring cylinder. When 50 C.C. have collected the cylinder is quickly changed without stopping the dis-tillation for a 100 c ~ . cylinder. As soon 8s 98.5 c . ~ . have come over the flame is extinguished and the contents of the flask allowed to cool. By the time that all drops from the condenser have ceased 100 C.C. will have been collected. Should the first 50 C.C. be turbid from the presence of water a pellet of calcium chloride is added and the cylinder well shaken and allowed to stand. The contents of the distilling-flask are cooled under the tap transferred to the special boiling-point apparatus and the boiling-point taken as follows : The apparatus is connected to a reffux condenser and boiled at such a spee 386 NORTHALL-LAURIE A NEW METHOD FOR THE that the condensed fluid runs back at the uniform rate of 1 drop per second.The thermometer should be divided into tenths of a degree and should be tested to ascertain if it is accurate between temperatures of 80’ to 140° C. When the temperature has become constant - which takes about ten minutes - the ther-mometer is read the necessary corrections for atmospheric pressure and length of exposed stem made and the figure noted. The apparatus is then disconnected emptied dried out and the liquid contents of the 50 C.C. oylinder-which by this time will be quite dry-added.The boiling-point is noted in a similar manner and on reference to the graph the vertical co-ordinate of which represents the boiling-points of the first fraction and the horizontal co-ordinate of which represents the boiling-point of the last fraction, the percentages of toluene and benzene present in the sample can be read off. The difference between the sum of these percentages and a hundred represents the xylene. Advantages of the Process.-There is no need to measure the fractions very accurately as slight variations in the amounts collected will not affect the value of the boiling-points determined. This obviates the necessity of cooling the fractions to one temperature which is a source of delay in hot weather. If the sample is at tap-water temperature the fractions will necessarily be at the same temperature thus eliminating any error due to expansion DETERMINATION OF TOLUENE IN COMMERCIAL TOLUOLS 387 The only part of the process requiring special care is in the taking of the boiling-point which would present no difficulties to a qualified man.A determination can easily be completed in from thirty to forty minutes. After the first distillation is finished the boiling-point of the fractions obtained can be taken whilst the second sample iB being distilled; and consequently the process takes no longer than the time required to distil 150 C.C. at the rate of 7 C.C. per minute. Accuracy.-It will be noted by inspection of the graph that the difference in the boiling-points is quite appreciable for 1 per cent.difference in the toluene present. There is no difficulty in determining the percentages with an accuracy of 0.1 per cent. Limitations of the Process.-The new method will give direct results for all possible combinations of toluene with benzene and xylene in gamples containing from 50 to 100 per cent. toluene the accuracy of the results being greater the higher the percentage of toluene present in the sample. The value of great accuracy in determinations of toluene in commercially pure samples is apparent it being important to be able to report upon the quality of small impurities in commercial (' pure toluene " now required for the manufacture of tri-nitro-toluene. For samples containing less than 50 per cent. toluene such as 5Os/9Os benzols it would be neces-sary to add a known quantity of pure toluene so as to bring the results on the graph, This is easily done by taking 100 C.C.of the sample and 100 C.C. of the toluene the error produced by doubling the result being more than offset by the greater accuracy of the determination. There is no limitation as to the percentage of benzene or xylene present so there is no need to add anything but toluene to the sample. Parafin.-Any paraffin present in the sample would appear in the analysis as toluene and the necessary correction must be made for this material. This can be done by the method suggested by Dr. Colman-namely to take in the case of very pure toluene the gravity of the sample; or in the case of toluenes of lower per-centage the specific gravity of the fractions distilled over between the temperatures of 107' and 115' C.using a Young 12 bulb head. Every unit in the third place in the specific gravity less than the specific gravity of pure toluene,-namely 0.870-will represent 0.66 per cent. of paraffin in the toluene found. Example.-The specific gravity of a sample was 0.868. This is two units less than 0-870 2 x 0.66 equals 1.3 per cent. paraftin. Therefore if the sample contains 60 per cent. toluene the paraffin present would be 0.78 per cent. Carbon Bi-sulphide.-This material does not occur in toluenes containing over 60 per cent. but is likely to occur in 50S/9Os benzols. I t is necessary to remove this material before the process can be employed. This is easily done by means of alcoholic potash the carbon bi-sulphide being removed as xanthate.The alcohol used must be either pure ethyl alcohol or industrial spirit. Ordinary methylated spirit contains paraffins. Further Note on taking the Boiling-Point.-As the whole process depends upon the acourate determination of the boiling-point care must be taken to always take readings under similar conditions. The apparatus used for this purpose should be This difference increases with the increasing percentage of toluene 388 NORTHALL-LAURIE A NEW METHOD FOR THE of the exact size specified. The flask should be supported 34" above the top of the Bunsen burner which burner must be screened from draughts by means of a cylinder of wire gauze. The flask should rest on a square of asbestos with a hole 14" in diameter.The stem of the thermometer must be screened from convection currents by means of a square of cardboard slipped over the cork. An auxiliary thermometer should be suspended within 3" of the thermometer, SO as to give the air temperature immediately surrounding its stem. The whole apparatus should be well protected from draughts. The rate of boiling must be so regulated that the drops falling back from the reflux condenser do so at the uniform rate of 1 drop per second. The most convenient way of regulating this rate is to employ a metronome. With these precautions it is quite easy to obtain rapid observations within one-tenth of a degree. Boiling- Po& Corrections.-It is of course necessary on account of the changes in atmospheric pressure to make corrections in the boiling-point.The relationship between the boiling-point of liquids to pressure is expressed by the equation AT= (760-p)(273 x t)C where AT is the difference between the observed boiling-point and the boiling-point at 760 mm. pressure t is the boiling-point of the liquid ; p is the atmospheric pressure reduced to 0" C. and C is a constant. The values of C are-For benzene . . . 0.000121 , toluene . . . 0~000?20 , xylene . . . 0*000115 Within the usual limits encountered the mean value of this constant can be employed and the following corrections which have been determined from the above equation will apply : Pressure. 770 769 768 767 766 765 764 763 762 761 760 Correction t o be made. - 0.45 - 0.4 - 0.35 - 0.3 - 0.25 - 0.2 - 0.2 - 0.15 - 0.1 - 0.05 0.0 Pressure.759 758 757 756 755 754 753 752 751 750 749 Correction t o be made. + 0-05 + 0.1 + 0-15 + 0.2 + 0.2 + 0.25 + 0.3 + 0.35 + 0.4 -t 0.45 + 0.5 Pressure. 748 747 746 745 744 743 742 741 740 739 738 Correction to be made. + 0.55 + 0-6 + 0.65 + 0.7 + 0.75 + 0.8 + 0-86 4- 0.9 + 0.9 + 0.95 + 1.0 Stem Correctio.ns.-As a portion of the stem of the thermometer has not been entirely surrounded by the vapour of the boiling liquid another correction is required DETERMINATION OF TOLUENE IN COMMERCIAL TOLUOLS 3 8 9 0.35 0.43 0.52 before the true boiling-point is obtained The corrections to be added have been calculated from the formula 0.000143 (T - t ) N when T is the observed boiling-point, t the temperature of the stem outside flask and N the length of the mercury column in degrees not heated by the vapour.The following table embodies the values obtained and should be used for the purpose of making the necessary corrections correction to the nearest 0.05" being taken : 0.40 0.50 0.60 T - t. N. 10 20 30 40 50 60 70 80 90 100 50'. 0.07 0.15 0.22 0.29 0.36 0.43 0.50 0.57 0-65 0.72 60". I 70" 80". ' 90'. 1 100'. 0.12 0.23 0.34 0.46 0.57 0.68 0*80 0.91 1.02 1.14 0.13 0.26 0.39 0.52 0.65 0.78 0.91 1.03 1.17 1.30 0.1 4 0.29 0-43 0-57 0.71 0.86 1.00 1.14 1.29 1 -43 l l o o . -___. 0.16 0-32 0.48 0.63 0.79 0.95 1 *10 1.27 1-42 1.57 Note on the GYapL-It will be noted that besides the black lines running in a sloping direction and gradually becoming more curved as the percentage of toluene becomes less there are horizontal red lines running across the graph. These repre-sent percentages of benzene and the graph therefore enables not only the per-centage of toluene to be determined but also the percentage of benzene. The sum of these percentages taken from 100 will give the percentage of xylene. Conclusion.-The method above described is quick is applicable to all commer-cial samples gives results with an accuracy of 0.1 per cent. and is especially valuable for determining the purity of "pure toluene." It is of course only applicable to commercial toluenes that have been washed free from phenols and unsaturated bodies

ISSN:0003-2654    

DOI:10.1039/AN9154000384

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

390 RECOVERY OF AMMONIUM MOLYBDATE THE RECOVERY OF AMMONIUM MOLYBDATE USED IN PHOSPHATE ESTIMATIONS. BY J. A. PRESCOTT B.Sc. THE extensive use made of ammonium molybdate in agricultural laboratories for the determination of phosphates and its present high price have led to attempts at recovering the molybdate from the residues obtained after the phosphate estimation has been carried out. Practically all the molybdenum salts have been extracted from the Australian ores in Germany and at the-outbreak of war the price of ammonium molybdate went up to 40s. per pound as against the normal price of 4s. 6d. Owing to the enormous excess of reagent required in proportion to the phosphate to be estimated this price would have become almost prohibitive if some method of recovery had not been devised.By the use of the method described below several hundred estimations of phosphate have been carried out at the Rothanisted Laboratories with molybdate which was in hand at the outbreak of war. The method is fairly simple and has the further advantage that it can be carried out quite satisfactorily by the ordinary skilled but untrained laboratory assistant,. The residues to be dealt with are usually of three kinds : 1. Acid liquors from which the yellow phospho-molybdate precipitate has been removed by filtration. This contains ammonium molybdate ammonium nitrate and a large excess of acid usually nitric or sulphuric acid in addition to calcium mag-nesium and other metals derived from the fertiliser or soil which has been analysed. 2. Alkaline or neutral liquors obtained by dissolving the yellow precipitate in ammonia and the subsequent precipitation with magnesium mixture or by dissolving the yellow precipitate in excess of standard alkali as in the Pemberton titration method which is that at present in use at Rothamsted (J.A. Prescott J.Agric. Sci., 1914 6 111 ; ANALYST 1914 39 329). 3. Ignited residues consisting chiefly of the oxides of molybdenum. Method of Recovery. The method is based on the fact that if ammonium molybdate is boiled with excess of acid molybdic acid is precipitated. All residues are thrown into a large evaporating basin of several litres capacity which is kept heated so as to concentra.te the liquors thrown in. Owing to the preponderance of acid residues there is no necessity to add any more acid.As the liquors are concentrated rnolybdic acid is precipitated and eventually a strongly acid syrupy liquid is obtained from which crystals of ammonium sulphate or ammonium nitrate separate on cooling. A certain proportion of phospho-molybdate separates out with the molybdic acid. The whole is filtered and the yellow molybdic acid washed with cold water and then dissolved in excess of ammonia ; to the arnmoniacal solution magnesium mixture is carefully added till no more phosphate precipitates and the solution is then filtered concen-trated to a small bulk keeping ammonia present in excess and allowed to crystallise THE COMPOSITION OF DUTCE CHEESE ETC. 39 1 The mother liquors are worked up for further quantities of ammonium molybdate, and if necessary the molybdate obtained is recrystallised. On some occasions it wag found that the molybdic acid gave a blue solution on the addition of ammonia due to the presence of lower oxides of molybdenum. This was due to the fact that once or twice the recovery liquors had been evaporated to dryness and the molybdic acid in consequence overheated. This would probably occur also with residues which consisted of the ignited yellow precipitate. The addition of hydrogen peroxide to the solution in these cases was found to oxidise the solution rapidly and a clean product was then readily obtained. ROTHAMSTED EXPERIMENTAL STATION, HARPENDEN

ISSN:0003-2654    

DOI:10.1039/AN9154000390

出版商:RSC    

年代:1915

数据来源: RSC

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THE COMPOSITION OF DUTCE CHEESE, ETC. 39 1 THE COMPOSITION OF DUTCH CHEESE, AND THE SYSTEM OF CONTROL FOR WHOLE-MILK DUTCH CHEESE. BY J. J. L. VAN RIJN, PH.D. (Read at the Meeting, June 2, 1915,) DUTCH cheese was originally made in North and South Holland. The cheese made in the province of North Holland, having the shape of a ball, is commonly known as Edam cheese, the name being derived from the town Edam, which formed the centre of the North Holland cheese district. The cheese made in the province of South Holland is of a flat shape, and is known as Gouda cheese, after the principal town and market for the South Holland cheese district.Both varieties of cheese were originally made of whole milk. Edam cheese, however, is now mostly made from the mixture of the evening milk, from which a little cream has been taken off by hand, and the whole morning milk.Genuine Gouda cheese, on the other hand, is still nearly exclusively made from whole milk. Both varieties as made in the provinces of North and South Holland are so-called (( farmers’ cheeses,” although the making of Edam cheese in large collecting centres or factories is rapidly spreading.Since the making of butter was transferred from the farms to large creameries, it was essential to find an outlet for the skimmed or separated milk, with the result that in the province of Friesland cheese is made from milk with different degrees of fat. The well-known shapes of the Edam and Gouda cheese varieties were chosen for making thege skimmed cheeses, with the unfortunate result that it was not possible to differentiate from the appearance between the original full-cream article and the ‘‘ half-meat ” or skimmed imitation.I do not consider the making of the partly skimmed article objectionable. On the contrary, it has met a ready demand for a sound and nutritive article of food at a low price. I do not agree with those who object to the sale of cheese not made from whole milk on the ground that it is392 VAN RIJN: THE COMPOSITION OF DUTCH CHEESE, difficult to digest.There is no evidence to that effect ; on the contrary, experiments made with skim cheese in suitable form have proved that the diminution of fat alone does not affect the digestibility of the cheese to an appreciable extent. Not all the fat should, however, be taken out, not so much for the nutritive value of the fat which is still left in the skim cheese, but for the fact that a cheese containing little or no fat has a different texture and soon dries out to a hard substance, which must be difficult to digest. It is for this reason that a skim cheese always contains, and should contain, more water to give it a soft texture, and it should be consumed while still young. Cheese in Holland made in the Gouda and Edam shape may, therefore, be any- thing between the full-cream article and a product containing only a few per cent.of but ter-fat. As it is all made in Holland, it is difficult to deny the right to any of these varieties to be sold under the name of Dutch cheese as long as the makers or the authorities in Holland do not give exact definitions as to what it should be.The indiscriminate use of the names Gouda, or Edam cheese may, however, be contested if the composition of the cheese is not that of the genuine article. From the fact that very little full-cream Dutch cheese is found in England it may be concluded that only a very small proportion of full-cream cheese is made in Holland.This, however, is not so, as the production of full-cream Gouda cheese amounts to about 40,000 tons per annum. The total production of cheese in Holland for the year 1913 amounted to 95,710 tons, out of which 32,318 tons, or one-third, were half-meat and skimmed cheese. It would be unjust, therefore, to take the composition of the skimmed article as a true representation of what Dutch cheeso should be.Only cheese made from whole milk should be sold as full-cream Dutch cheese, and no cheese should be passed by an analyst when sold under that description unless its chemical composition is in accordance with the results of the analysis of cheese, of which it can be proved that it was made of full-cream milk. Since control stations have been established at The Hague and at Utrecht for full- cream Dutch cheese, thousands of samples of cheese, of which all particulars about its making were known, have been analysed.Dr. H. van Gulik, director of the cheese control station at The Hague, has obtained interesting figures, which not only show the variations in the chemical composition of full-cream Gouda cheese, but also the relations between the fat contents of the milk and the fat contents of the cheese.I may point out that the amount of fat in the cheese is expressed by the propor- tion of fat in the dry matter. This method of stating the result of the chemical analysis has been generally accepted in all other European countries, with the exception of Great Britain, as well as in America. It would be desirable if the custom of expressing the composition of cheese, by giving the percentage of fat in the dry matter, were also generally adopted here.The following figures show the average fat contents of whole-milk Gouda cheese for seven subsequent years and the number of samples which in 1913 fell within certain limite :AND SYSTEM OF CONTROL FOR WHOLE-MILK DUTCH CHEESE 393 Average Fat Contents in the Dry Substance of Whole-Milk Gouda Cheese.1907. 1908. 1909. 1910. 1911. 1912. 1913. Per Cent. Per Cent. Per Cent. Per Cent. Per Cent. Per Cent. Per Cent. 48.5 48.8 48.9 49.1 50.6 49-7 50.3 Fat in Dry Matter of Whole-Milk Gouda Cheese during 1913. Percentage of fat ... ... 45-46 46-47 47-49 49-51 51-53 53-57 Number of samples ... 2 5 191 254 155 39 Percentage of samples ...0.3 0.8 29.5 39.3 24.0 6.0 I t is evident that whole-milk cheese with less than 46 per cent. of fat in the dry matter is found very rarely, and it may be mentioned that in 1911 only three samples were found with less than 45 per cent. of fat in the dry matter, and none in 1913. Experience has shown that every cheese-maker is capable of making cheese with at least 45 per cent.of fat on the dry matter if he works according to well-established rules. I t will be shown later that he is in this respect independent of the amount of fat in the whole milk. Although in the figures cited above the highest percentage of fat is given at 57 per cent. on the dry matter, I may mention that Dr. van Gulik found in 1911 that 26 out of 799 cheeses showed an amount of fat varying from 58 to 64 per cent.on the dry matter. I n Table I. some figures are given relating to the composition of cheese between July 1 and 15,1909, as well as of the milk of which it was made. I haveitsken these figures from another publication by Dr. H. van Gulik, and they show clearly, whilst there is no direct relation between the amount of fat in the milk and in the cheese, it is possible to guarantee a minimum of fat when the cheese is properly made from whole milk.Rich milk, however, does not necessarily mean a high percentage of fat in the cheese, even when carefully made and when little fat is lost in the whey. In taking, for instance, samples Nos. 1, 9, 12, and 31, with respectively 49.6, 49.5, 50.6, and 49.1 per cent.of fat, it will be found that they were made from whole milk, with respectively 2.51, 2.95, 3-03, and 4-18 per cent, of fat, whereas the amount of fat left in the whey varied only between 0.27 and 0.35 per cent. I t is clear from the table that the variation in the percentage of non-fatty solids does not account for the differences in the amount of fat in the oheese made from milk with varying amounts of fat.For various reasons Dr. van Gulik came to the conclusion that those cases where milk with a relatively low percentage of non- fatty solids gave a cheese with less fat than might be expected, were due to the fact that such milk did contain a relatively high percentage of casein, On the’other hand, where milk with high non-fatty solids gave a cheese with relatively a great amount of fat, the percentage of casein in the non-fatty solids must have been low.That the amount of non-fatty solids in milk is relatively a more oonstsnt factor394 VAN RIJN: THE COMPOSITION OF DUTCH CHEESE, than that of fat is shown in the table, where it can be seen that the ratio between fat and non-fatty solids diminishes when the percentage of fat in the milk rises.TABLE I. Composition of Full-Crenm Gouda Cheese, Milk and Whey. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Water in Cheese. 42.7 43.3 42-8 43.0 45.3 44.2 41.5 43.4 38.8 40.8 43.0 44.5 40.8 42.2 43.4 43.5 44-0 43-5 43.3 39.9 40.0 40.7 41-4 43-2 42-5 43.5 39.8 41.9 43 -1 42.2 45.0 41.7 Fat in Cheese. 28.4 25.1 26.1 26.2 25.4 27.5 27-5 27-3 30-3 29.0 25.2 28.1 29-2 28.9 27.8 29.1 27.5 25.2 25 *5 31.2 29.4 30.2 28.4 27.0 30-4 27.9 31.3 30.9 27.7 30.3 27.0 31.5 Fat in Dri Substanci of Cheese.49-6 44.3 45.9 46.0 46.4 49.3 47.2 48-2 49.5 48.9 44.2 50.6 49 *2 50.0 49.1 51.5 49.1 44 '5 45.0 51.9 49.0 50.9 48.5 47.5 52.9 49.4 52-0 53.2 48.7 52.5 49.1 54.1 Fat in Milk. -___ 2-51 2.58 2.68 2-69 2.74 2-80 2.89 2.90 2-95 3.00 3 *OO 3.03 3.08 3.12 3.13 3-14 3.17 3.21 3.25 3.28 3.35 3.45 3-46 3.54 3.62 3-65 3-65 3.80 3.88 4.06 4-18 4-22 Fat in Whey.0-27 0.38 0.20 0.63 0.20 0.3 1 0.43 0.35 0.35 0.34 0.45 0.28 0.47 0.30 0.33 0.28 0.44 0.84 0-40 0.36 0.51 0.60 0.43 0.50 0.49 0.65 0.38 0.40 0.43 0.32 0.35 0.86 Non-Fat tj Solids in Milk, 8.28 8.31 8.48 8.16 8.46 8-35 8.35 8.34 8-37 8.43 8-52 8.51 8.38 8-38 8.47 8-32 8.44 8-35 8-47 8.18 8.58 8-51 8-50 8-35 8.31 8-49 8-47 8.45 8.58 8-44 8.34 8-19 - Relation between Fat and Non-Fatty Solids in Milk. 1 : 3.30 1 : 3.22 1 : 3-17 1 : 3.02 1 : 3.08 1 : 2.98 1 : 2.94 1 : 2-88 1 : 2-84 1 : 2-81 1 : 2-84 1 : 2.78 1 : 2-72 1 : 2-69 1 : 2-70 1 : 2.65 1 : 2.66 1 : 2.60 1 : 2.61 1 : 2.50 1 : 2.56 1 : 2.47 1 : 2-65 1 : 2.36 1 : 2.30 1 : 2.33 1 : 2-32 1 : 2-22 1 : 2.16 1 : 2-08 1 : 1.99 1 : 1.94 As an interesting result of the investigations of Dr.van Gulik, I may also mention that the amount of fat in the milk was much higher after cold and rainy days, and that in such cases the amount of fat in the dry matter of the cheese made from such milk wag also higher. System of Control-It is impossible to recognise from the external appearance whether a cheese in Gouda, shape is made from whole milk or from milk of whichAND SYSTEM OF CONTROL FOR WHOLE-MILK DUTCH CHEESE 395 more or less cream has been removed.For this reason the Holland Agricultural Society first established a control station, in order to guarantee the genuineness of such cheese. The control station is an institution organised by private individuals under supervision of the Government, and an ofiticial mark has been established which for whole-milk cheese is stamped in blue ink on a transparent disc of casein.I n the open space under the arms a letter and figures are printed which enable the officials responsible for the control to trace the origin of each cheese. The cheese is guaranteed to have been made of whole milk, to contain not less than 45 per cent.of fat on the dry matter, and not more than the normal amount of moisture. I t should be pointed out that the figure 45 per cent. must not be considered as a standard as it is generally understood, but that it is only a limit for fat in whole-milk cheese under which the cheese may not be sold with the Government control mark, even when made from unskirnmed milk.If for some reason or other, due to a defect in the making, whole-milk cheese would have less than 45 per oent. of fat in the dry substance, it cannot be sold under the official guarantee. The control stations are established by associations of interested persons. Only such persons can be admitted to these control stations who are of good repute and who are not connected with the manufacturing of, or the trade in margarine (margarine as meant by the Butter Act) or other fats or oils which either in its pure state or mixed with other substances are edible or can be used for the adulteration of cheese.The cootrol ioo!udes the supervision of the process of manufaoturing, and is based upon the examination-(a) of the quantity and the composition of the milk used; ( b ) of the composition and the quantity of the cheese and the whey butter obtained therefrom ; and (c) of the quantity of fat left in the whey.The Netherlands Government has fixed rules to which the control stations for whole-milk cheese and their members must submit before they are allowed to use the Government mark ; it also prescribes the analytical methods to be used and sees that fiuch rules are strictly followed.Apart from the cheese control stations for whole-milk cheese at The Hague and at Utrecht, one has been established at Leeuwarden. The object of this station is to establish marks for the different grades of skimmed cheese made in the province of Friesland, in order to enable purchasers to recognise by such marks the approxi- mate fat contents of the cheese and also to control the.makers of cheeses of Cheddar and Cheshire types at the present time.The Association of Go-operative Creameries in Friesland, in which province Cheddar and Cheshire cheeses are made, has prohibited the making of such cheeses from milk with less than 18 per cent. of fat, and has compelled its members to mark all Cheddar and Cheshire cheeses made of whole milk with the words, “Full Cream,” “Dutch Produce,” and all Cheddar and Cheshire cheese made of milk of which even the slightest amount of fat has been taken off with the words “Half-Meat” and ‘‘ Dutch Produce.” Mr.de Kruyff, Director of the Friesian Control Station, has analysed several No Government guarantee mark is given for these varieties.396 VAN RIJN: THE COMPOSITION OF DUTCH CHEESE, samples of full-cream Cheddar and Cheshire cheeses which were made under his control, and the results are given in Table 11.It is clear that no fixed relation exists between the amount of fat in milk and in the cheese, although some of the cheeses with the greatest amount of fat are at the bottom of the tables, where also the highest figures for fat in milk are found.TABLE 11. Full Cream- Dutch Cheddar Cheese. Fat in Milk. 2 -75 2-80 2.85 2.90 2.95 3.0 3.0 3.05 3-05 3.10 3-10 3-15 3.20 3-20 3.25 3.25 3-30 3.40 Fat in Cheese. 30.2 31.8 30-4 31.3 31.6 31.5 28.9 32.2 31.1 31.9 30.5 33.5 32.0 32.9 34.3 33 -0 33.1 31.2 Pat in Dry Substance of Cheese. 49.9 52.7 51.2 52-6 50.1 52.8 49.7 53'1 51.8 52.0 49 -4 53.3 51.9 53.8 54.5 51.4 53.0 53.1 Dutch Cheshire Cheese.Fat in Milk. 2.60 2.65 2-75 * 2-85 2.90 3-05 3.10 3.26 3-30 3.45 3-50 3.55 3070 3 *80 Fat in Cheese. 25.9 27.1 26.3 25.0 28.2 27.2 2003 27.i 27-8 28.2 27.1 27.2 28.1 30.8 Fat in Dry Substance of Cheese. 48.6 49.5 47.9 48 J4 50.4 49 7 51.0 50.6 52.1 51.3 51.7 50.4 53.7 53-4 The figures show that the amount of fat in the dry substance of Cheddar and Cheshire cheese made of whole milk is always well over 45 per cent., even when the amount of fat in the milk was low.Th InJuence of skimming the Milk.--Mr. De Kruyff has analysed many cheeses in Gouda, and Edam shape, made from milk whioh was skimmed in different degrees so that the milk contained from 0.5 per cent. to 2 per cent.of fat. The results of these investigations show that the increase in the percentage of fat in skimmed miEk has a very marked effect on the increase of the amount of fat in the cheese. Cheese made from skimmed milk with 0.5 per cent. fat showed an average percentage of fat on the dry matter of the cheese of 12.45 per cent. When the fat in milk was increased to 0-65 per cent., the fat in the cheese rose to 15.8per cent.; fat in milk 0.90 per cent., fat in cheese 21.3 per cent.; fat in milk 1.0 per cent.,AND SYSTEM OF CONTROL FOR WHOLE-MILK DUTCH CHEESE 397 average fat in cheese 24.1 per cent.; fat in milk 1.20 per cent., fat in cheese an average of 28.6 per cent. ; fat in milk 1.40 per cent., fat in cheese 31.5 per cent. ; fat in milk 1.5 per cent., average fat in cheese 33.6 per cent. ; fat in milk 1.65 per cent., average fat in cheese 35.3 per cent.; fat in milk 1-8 per cent., fat in cheese 36 per cent.; fat in milk 2 per cent., fat in cheese 38.65 per cent. These figures show that an increase of 0.1 per cent. in the amount of fat in skimmed milk gives on an average an increase of 1.75 per cent. of fat on the dry substance of the cheese.This does not mean that it is possible to calculate exactly the amount of fat which will be found in the dry matter of the cheese when the percentage of fat in the skimmed milk is known. Just as we have seen with cheese made of whole milk, differences are found in the composition of cheese made from milk with the same amount of fat. These differences may even be very large when a great number of samples are analysed from different creameries.Mr. De Kruyff mentions in his report that the amount of fat on the dry substance of eighty different cheeses all made from skimmed milk containing 1.55 per cent. of fat, varied from 30.2 per cent. fo 34.4 per cent. The extreme figures were only found once, and only two samples were found containing more thau 37 per cent., or less than 31 per cent.of fat. The great majority was near the average of 33.6 per cent. Edam Cheese.-As already mentioned, Edam cheese in the province of North Holland is now mostly made of a mixture of partly hand-skimmed evening milk and whole morning milk. For this reason Edam cheese is not considered a whole-milk .cheese, but only a fat cheese.It is generally agreed that Edam cheese should not .contain less than 40 per cent. of fat on the dry substance. DISCUSSION. The PRESIDENT remarked that he understood the figure of 45 per cent. for fat on the dry substance to be a minimum limit, and that even full-cream cheese falling below that limit might not be sold under the Government mark. There was, however, a considerable margin between this and the highest figure-namely, 57 per cent.-which might afford some inducement to partial skimming of the milk.On the other hand, the verification, by analysis of the milk, cheese, and whey, of the title of .each cheese to be stamped with the Government mark, must involve an enormous amount of work. A striking point in connection with these figures was that, as Dr. van Rijn had mentioned, there was no sort of connection between the percentage .of fat in the dry cheese and the percentages of fat and non-fatty solids in the milk.Another noticeable point was the lowness of the non-fatty solids in the majority of the milk samples. Mr. F. J. LLOYD said that, although Dutch cows sometimes gave milk of excellent quality, it was generally characteristic of them to give milk that was poor in fat and in non-fatty solids.As a rule, however, this was compensated for by the large quantity of milk yielded. In deciding whether a given cheese was or was not made from whole milk, his custom was to determine the ratio of fat to casein. Milk .almost invariably contained more fat than casein. He should have liked to see the percentage of casein in Dr.vrtn Rijn’s samples, but he thought that where the fat was398 THE COMPOSITION OF DUTCH CHEESE, ETC. low the casein would be found to be low also. In the early part of the year, when the percentage of fat in the milk was usually low, the casein was as a rule under 3 per cent. ; but later on, when the percentage of fat increased, the increase -in casein was not correspondingly great, so that at that time of year there was a wide difference between the fat and the casein.Invariably in a whole-milk cheese the percentage of fat was greater than the percentage of casein. Dr. RIDEAL pointed out that in three of the thirty-two samples of cheese referred to, the fat in the dry substance was not up to the Dutch Government’s standard of 45 per cent.Dr. VAN RIJN, in reply, said that the Government system of control was very elaborate. A cheese was not. stamped with a Government mark merely because its dry matter contained 45 per cent. of fat, that figure being merely fixed as the limit below which the fat should not fall, even though the cheese might be made from unskimmed milk. In some cases, it would be noticed, the fat in the whey was rather high, and cases had occurred in which it was as much as 1 per cent.I n such a case the farmer could make a good deal of whey butter, and although the milk itself would not have been skimmed, the cheese could not be regarded as genuine. As Mr. Lloyd had explained, the milk of Dutch cows was sometimes low in fat, but this was really due to want of attention to the breeding of the cows. Those Gouda cheeses, under the control station at The Hague, were all made in a certain district round Gouda, where the farmers, although the best cheese-makers, were not the best breeders in the country. In other districts where care had been taken in recent years to improve the cattle, it was difficult to find a herd yielding milk with an average less than 3 per cent. of fat. The samples referred to in the tables were from different farms, but were all taken within a period of fourteen days, so that the differences between them had nothing to do with the time of year. They were, however, taken in 1907, when the control system was just started, and in the course of the investigations which were then undertaken with a view to ascertaining what the proper composition of the cheese should be. Since then the quality of the cheese had improved, and in 1913 no sample was found to fall below the 45 per cent. limit- Mr. Lloyd was quite correct in his remarks as to the importance of the ratio of fat to casein.

ISSN:0003-2654    

DOI:10.1039/AN9154000391

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

FOOD AND DRUGS ANALYSIS 399 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOOD AND DRUGS ANALYSIS. Estimation of the Amino-Acids in Feeding-Stuffs by the Van Slyke Method. H. S. Grindley, W. E. Joseph, and M. E. Slater. (J: Awr. Chem. Sot., 1915, 37, 1778-1781.)-The following quantities of amino-acid nitrogen were found in various feeding-stuffs, the Van Slyke method (ANALYST, 1911, 36, 457) being used for the estimations; the results are expressed as percentages of the feeding-stuff: Cottonseed Meal.-As ammonia, 0.702 ; melanine, 0.522 ; arginine, 1.311 ; cystine, 0.043 ; histidine, 0.367 ; lysine, 0.321 ; amino-nitrogen in filtrate from bases, 2.876 ; non-amino-nitrogen, 0.365 ; total nitrogen, 6.507.Tankage.-As ammonia, 0,659 ; melanine, 0.440 ; arginine, 1.416 ; cystine, 0,128 ; histidine, 04951 lysine, 0.749 ; amino-nitrogen in filtrate from bases, 5.238 ; non-amino-nitrogen, 0.729 ; total nitrogen, 9.851.AZfava Hay.-As ammonia, 0.222 ; melanine, 0.415 ; arginine, 0.202 ; cystine, 0.019 ; histidine, 0.196 ; lysine, 0.108 ; amino-nitrogen in filtrate from bases, 1.157 ; non-amino-nitrogen, 0.267 ; total nitrogen, 2.573. w. P. 8.Estimation of Fat. H. Rosenthal and P. F. Trowbridge. (Amer. J. Pharm., 1915, 87, 309-315.)-While a simple extraction of the fat with ether in a Soxhlet extractor gave concordani; results in the estimation of fat in pork, the results were variable and unreliable in the case of blood and liver. To obviate the extraction of substances other than fat the following method is suggested : The sample is heated with occasional stirring for two hours on the water-bath with 30 C.C.of 20 per cent. sodium hydroxide solution. The warm saponified solution is transferred to a separating funnel, mixed with 35 C.C. of 20 per cent. hydrochloric acid (sp. gr. 1-l), and when cold shaken with ether. The ethereal extracts are united, and evaporated to dryness, and the residue dissolved in about 25 C.C. petroleum spirit (boiling-point 30' to 50' C.), treated with 15 C.C.of 95 per cent. alcohol, and titrated with zV alkaline solution, with phenolphthalein as indicator. I n converting the fatty acids into neutral fat the factor 1.045 is used. C. A. M. Composition of Extraeted Olive Oils Purified by Esterification. F. Can- zoneri. (AnnaZi Chirn. AppZic., 1915, 3, 344-349.)-0live oils which have been extracted with carbon disulphide are now neutralised and decolorised by a, patent process of esterification.The resulting products have a pleasant odour, and are completely saponifiable. They are soluble in alcohol, ether, and carbon disulphide, and rapidly oxidise to form viscous liquids. A sample prepared from an olive oil with an acidity of 22 per cent.(as oleic acid) had the following characters : Sp. gr. 09055 ; refractometer reading (Zeiss), 51.5 ; iodine value, 75.20; Maumenb test, 40' C.; and viscosity (Engler), 5.8. Another sample, prepared from an olive oil with 50 per cent. of free acid, had a sp. gr. of 0.901; iodine value, 73; and viscosity of 4.5. I t s approximate composition was as follows : Esters of fixed fatty400 ABSTRACTS OF CHEMICAL PAPERS acids (mainly oleic acid), 51; esters of volatile fatty acids, 2 ; glycerides, 37; free acids (as oleic acid), 5 ; hydroxystearic acid, 3 ; and stearolactone, 2 per cent.C. A. M. Constants of the Fatty Acids from Sulphonated Cod Oil. L. G. Radcliffe and C. W. Palmer. (J. SOC. Chem. Ind., 1915, 34, 643.)-The constants of the fatty acids prepared from a brown cod oil, and of those obtained after the oil had been sulphonated, are given below.The sulphonation was carried out by gradually adding 35 grms. of concentrated sulphuric acid to 100 grms. of the oil, the mixture being cooled externally so that the temperature did not rise above 25" C. After two hours' stirring, the darkened and thickened product was washed with cold saturated sodium sulphate solution until nearly all the free sulphuric acid had been removed, and the fatty acids were then separated : Fatty Acids from Fatty Acids from Original Oil.Sulphonated Oil. Solidifying-point (titre test) . . . 22.8' C. 25.7" C. Neutralisation value . . . ... 194 183 Mean molecular weight ... ... 289.4 308.6 Iodine value ... ...... 178 114.4 Yield of hexabromides ... ... 42 per cent. 11 per cent. w. P. s. Analysis of Guara and Guara Extract. T. Callan. (J. Sot. C k m . 1915, 34, 645-646.)-Guara is a newly-introduced tanning material consisting of the ground fruits of a variety of divi native to South and Central America, freed from seeds and woody husks. The most distinctive features in the microscopical appearance of the substance are the small brown plates showing a honeycomb structure and small brown plates furnished with needle-shaped hairs.A dilute aqueous infusion of guara, gkws a violet-blue coloration with iron alum, no precipitate with bromine water, no phloroglucinol reaction with a deal shaving, a yellow precipitate turning green with lime-water, a slight precipitate with formaldehyde and hydrochloric acid, a yellow coloration with sodium sulphite, an intense red coloration with very dilute ammoniacal potassium ferricyanide solution, and a deep orange-brown coloration with nitrous acid.Analyses of numerous samples show that guara contains: Moisture, 9.0 to 10.7 per cent. ; tannins, 43-5 to 48.4 per cent. ; non-tannins, 23.1 to 25.8 per cent.; insoluble substances, 19.0 to 22.0 per cent.Skins tanned with guara give a soft, well-filled leather, resembling a gambier tannage rather than a sumach or myrobalan tannage. A sample of solid guara extract examined contained : Moisture, 17.3 per cent. ; tannins, 41.7 per cent. ; non-tannins, 30.0 per cent. ; insoluble substances, 11.0 per cent. I n use the extract has proved to be inferior to the natural product.w. P. s. Group Method for the Detection of Gelatinising Agents, Pasty Material, and Thickeners used in Food Products. L. A. Congdon. (J. Ind. and Eng. Chem., 1915,7,606-607.)-Many thickening materials are used to cover up inferiority in food products. Albumen or white of egg is sometimes used to glaze coffee beans.FOOD AND DRUGS ANALYSIS 401 Agar-agar has been found in imitation lemon slices ; starch, agar-agar, and gelatins in imitation jelly ; dextrin in imitation cocoa tubes; ice-cream powders, used in ice cream and custards, employed to add bulk to the product and to give the material in which they are used a frothy appearance, may contain one or more of the following : Dextrin, gum acacia, gum tragacanth, gelatin, albumen, and starch.The following scheme has been set out, which will lead to the identification of any or all of these materials : Groups. Group I. .. Group 11. .., Group 111. . . . Group IV. . .. Group V. ... Group VI. , . . Group Reagents. Iodine solution ..( Millon’s or Stokes’s r e a g e n t ( a c i d nitrate of mercury) Zoncentrated solution of sodium borate Solution of sodium hydroxide Solution of mercuric chloride Schweitzer’s reagent (solution of cupra- ammonia) Reactions with Water-Soluble Solutions of the Gelatinising Agents, Pasty Materials and Thickeners. Blue coloration indicates starch.(Sometimes green apples made into jelly will give traces of starch.) Purple coloration indicates amylo-dextrin. Red coloration indicates erythro-dextrin.No coloration may suggest the presence of achro-dex trin. Mixture, after shaking substance in solution with reagent, is cloudy. Yellow preoipitate with picric acid solution indicates gelatin. Drop of this reagent : Gelatinous precipitate, soluble in excess of this reagent, indicates gum acacia. A slight white precipitate may indicate either agar-agar or gum tragacanth or both (test for tragacanth as in Group IV.).A white gelatinous preoipitate indicates either agar-agar or gum acacia or both. Gum acacia will give a gelatinous opaque white precipitate with basic lead acetate. Gum acacia may be further tested for as in Group 11. or Group IV., or by adding a solution of tannin, which produces a bluish- black coloration. A brownish yellow colour on heating indicates gum tragacanth.A white cloudy precipitate indicates gum acacia. A slight turbidity may indicate dextrin. A white precipitate may indicate albumen and gelatin. If a concentrated aqueous solution of the material to be tested is treated with this reagent and placed on a glass slide under a microscope, a delicate framework of cupric pectate is evident, showing a pectin of fruit or vegetable origin present.H. F. E. H.402 ABSTRACTS OF CHEMICAL PAPEES New Method for the Estimation of Hydrocyanic Acid and Benzaldehyde in Kirsch. J. Golse. (J. Pharm. Chim., 1915, 12, 44-56.)-The French official method for the estimation of hydrocyanic acid and benzaldehyde in cherry liqueurs leads to seriously inaccurate results, The two constituents are separated by dis- tilling the liqueur previously made slightly alkaline in order to fix the hydrocyanic acid.I t is proved, however, that sodium cyanide is only stable on distillation in presence of a large excess of sodium hydroxide, and it is necessary to add to 200 C.C. of kirsch at least 10 C.C. of caustic soda lye, sp. gr. 1-32 to 1-36, Further, the dis- tillation of the benzaldehyde is not complete with the collection of 125 c .~ . of distillate, and the precipitation of the hydrazone often fails in presence of the quantity of alcohol commonly found in kirsch distillates. In investigating this matter it was noted that, in the case of cherry-laurel water, an accurate separation could be obtained by employing the large excess of alkali above mentioned and collecting 175 C.C.of distillate, but in the case of kirsch the secondary effects of the, alkali, accompanied by violent frothing, make the method not readily practicable. An alternative method, based on the fixation of the benzaldehyde by phenylhydrazine and distillation of the hydrocyanic acid, was also successful with cherry-laurel water, but failed with kirsch on account of the existence of a portion of the acid in the form of non-volatile combination.Finally, the following procedure was adopted: 200 C.C. of kirsch are placed with 1 C.C. of caustic soda lye in a flask of 500 C.C. capacity carrying a dropping funnel extending below the surface of the liquid and a tube leading to a condenser, 1 metre long. Distiliation is carried out very slowly on account of frothing, and 175 C.C. of distillate are collected, The contents of the flask are cooled, and the point of the condenser is caused to dip into a gauged flask of 55 C.C.containing 5 C.C. of ammonia, ; 50 C.C. of sulphuric acid (1 : 10) is then slowly added through the dropping funnel, and distillation is continued until 50 C.C. of distillate have been collected separately. The 175 C.C.of distillate first obtained is treated with 5 C.C. of phenyl- hydrszine reagent (10 grms. of sodium acetate, 5 C.C. of glacial acetic acid, 100 C.C. of water, 1 C.C. of phenylhydrazine, and 1 C.C. of sodium bisulphite solution), and its volume made up to 200 C.C. This liquid is redistilled, the firat 75 C.C. of distillate, containing hydrocyanic acid, being added to the 50 C.C.previously collected, and a further quantity, ranging from 50 to 75 c.c., according to the alcohol-content of the kirsch, is distilled off. Without removing the condenser, a water-bath is then sub- stituted for the Bunsen burner, and the poiht of the condenser is closed with a rubber tube and clip to exclude the air. The contents of the flask are digested in the water-bath for two hours, until the precipitate of hydrazone has settled.After cooling, the hydrazone is collected on a filter, washed, and dissolved on the filter first with 10 C.C. of alcohol, then twice with 10 C.C. of ether. The solution is collected in a tared glass dish, evaporated, and the hydrazone dried in vacuo and weighed ; the weight x 2.7 gives the benzaldehyde per litre. The distillate con- taining the hydrocyanic acid is treated with 1 C.C.of 10 per cent. potassium iodide solution, and titrated with & silver nitrate, until a permanent opalescence is formed ; the number of C.C. used x 13.5 gives the mgrms. of hydrocyanic acid per litre. Analyses of authentic samples of kirsch showed from 17.6 to 35.8 mgrms. of hydro-FOOD AND DRUGS ANALYSIS 403 cyanic acid per litre and 29.7 to 37.3 mgrms.of benzaldehyde, while specimens, probably sophisticated, showed from 52.9 to 108 mgrms. of the latter per litre. J. F. E. Estimation of Lint in Cottonseed Meal. R. N. Braekett. ( J . I d . and Eng. Chem., 1915, 7, 611, 612.)-Alkali and acid of 1-25 per cent. strength as used for crude fibre estimations are practically without action on lint.A portion of cotton- seed was carefully freed from lint, the seeds were then cut open, and the interior of the seeds was completely separated from the hulls. Crude fibre was then prepared from both the hulls, and the seed interiors, and the material thus obtained was treated in 0.2 grm. portions side by side with the same weight of lint, on a boiling water bath with 25 C.C.of a solution of zinc chloride for three minutes, the time required to dissolve the lint. The zinc chloride solution was prepared by dissolving metallic zinc in concentrated hydrochloric acid, concentrating until the solution solidified on cooling, and then adding twice the weight of 40 per cent. hydrochloric acid. On treating the crude fibre and lint with the zinc solution, the contents of the beakers were stirred vigorously during the three minutes necessary to dissolve the lint, and filtered hot through weighed porcelain Gooch crucibles with asbestos mats; the residues in the case of the fibres were washed with 25 C.C.of the zinc solution, then with water, and finally with 95 per cent. alcohol. Test mixtures of known composition showed an error of about 0.5 per cent., calculated on the weight of lint present in the mixture.H. F, E. H. Volumetric Estimation of Sulphurous Acid in Wines. L. Ferr6. ( A m . Chim. anal., 1915, 20.)-A measured quantity (100 c.c.) of the wine is acidified with 2 C.C. of syrupy phosphoric acid, and gently boiled for thirty minutes in a flask con- nected with absorption vessels, one containing 40 C.C. of iodine solution (3.968 grms. per litre, 1 c.c.=O*OOl grm. of SO,), and the other 5 C.C. of sodium thiosulphate solution (7.740 grms. per litre, 1 C.C. =0.001 grm. SO,). The thiosulphate solution in the second vessel is then added to the iodine solution in the first vessel, and the mixture titrated with more of the thiosulphate solution. Combined sulphurous acid is estimated by adding to 100 C.C. of the wine the number of C.C. of iodine solution required to oxidise the total sulphurous acid, as found in the first estimation. Sufficient standard sodium arsenate solution to destroy all the iodine, if no free sulphurous acid were present, is then added, and the estimation continued as in the case of total sulphurous acid. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9154000399

出版商:RSC    

年代:1915

数据来源: RSC

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FOOD AND DRUGS ANALYSIS 403 BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. Methods of Baeterial Analysis of Air. G. L. A. Ruehle. (J. Agric. Research, 1915, 4, 343-366.)-The author has made a critical investigation of the methods employed for estimating the bacterial contamination of air. Methods based on two general principles have been employed : (1) passing a known volume of air through a filtering apparatus (aeroscope) and counting the colonies developed from the filtering medium by plate-cultivation ; (2) estimating the bacterial precipita- tion from the air on a known area iu a definite time.Most of the work404 ABSTRACTS OF’ CHEMICAL PAPERS recorded in the paper relates to the comparative efficiencies of various forms of aeroscope. Two types have been in general use hitherto; viz., the standard aero- scope recommended by the committee of the American Public Health Association, in which a filtering layer of sand is used, and Rettger’s aeroscope, in which the air is bubbled through a small quantity of physiological salt solution.The author has adopted a slightly modified form of the standard sand-filter aeroscope which avoids certain small drawbacks of the original.I t consists of a wide glass tube 70 mm. long and 15 mm. in diameter, fused to a narrow tube 40 mm. long and 6 mm. in diameter, by which it is attached to an aspirator. The upper end of the wide tube is closed by a cork through which passes a narrow tube of the same dimensions as the lower one, but bent at an angle of 45’ t o prevent the entrance of bacteria by gravitational precipitation.The lower portion of the wide tube is packed with a plug of cotton wool above which is a layer, 10 mm. thick, of sand which has passed through a 100-mesh sieve but been retained on a 160-mesh sieve. A measured volume of air is aspirated through the aeroscope at the rate of about 0-5 to 1-0 litre per minute; the sand is then shaken out into 10 C.C.of sterile water and aliquot portions of this suspension are cultivated on agar-agar plates. It was found that the standard form of aeroscope varied in its filtering efficiency from 50 to 100 per cent., with an average efficiency in two series of tests of 90 and 91.6 per cent. I t is believed that the chief cause of error in this pattern arises from the fact that it is so constructed that it must be sterilised by steam, which causes caking in the sand filter.The modified pattern described above can be sterilised by dry heat, and was found to retain nearly 100 per cent. of the bacteria with little chance of error. For field work it is more convenient in every way than the liquid type of aeroscope recommended by Rettger, although this latter may be made to yield excellent results if manipulated with sufficient care.The method of determining bacterial precipitation from air by means of exposed Petri dishes containing solid nutrient is obviously quite unreliable, since it affords a measure only of the number of infected dust particles falling on a given area, irrespective of the number of bacteria conveyed by them. The latter figure is more correctly estimated by exposing sterile water in sterile vessels for a given time and inoculating plates from these.J. F. B. Electrolytic Determination of BiologicaI Solution. E . Pantanelli. (Centralbl. fur Bakt., 1914, 42, 439-443; through Bull. Agric. Intell. and Plant Diseases, 1915, 6 , 663.)-In determining the part played by microbiological action in rendering the soil constituents available, Borne investigators have measured directly the electrolytic conductivity of water-saturated soil ; the author modified this method by estimating the conductivity of the percolating solutions of the soil.He used in his experiments different soil samples from the neighbourhoods of Tripoli and of Naples. Through these he allowed : (a) sterilised water, (b) sterilised water saturated either with chloroform, or 0.5 per cent.dextrose, or (c), water mixed with dextrose and chloroform to percolate three times. He found that the determination of the electrolytic conductivity was a good method of estimating the microbiological solubility of the soil particles, especially if the experiment was carried out com- paratively with and without the addition of chloroform and dextrose.ChloroformBACTERIOLOGICAL, PHYSIOLOGICAL, ETC. 405 increases, while dextrose decreases, but not always, the leaching out of the salts from the soil. The solubility of the soil usually varies with the number of micro- organisms it contains. Reaction for Indole : Detection of Cholera Bacilli. 0. Baudisch. (Xeitsch. physiol. Chem., 1915,94,132-135; through J.Soc. Chem. Ind., 1915,34,849.)-1~ testing for cholera bacilli a surface culture of the suspected organisms is made on agar, and after eight to sixteen hours a group of colonies is transferred with the supporting agar to a test-tube and heated to boiling with dilute potassium hydroxide solution containing a small quantity of nitromethane. After the solution has cooled some- what it is shaken with 1 C.C.of amyl alcohol, and again after addition of an excess of strong hydrochloric acid. The alcoholic layer, which separates best if the liquid is warmed nearly to boiling, is coloured red or pink if the colonies have produced the slightest trace of indole. The nitromethane, instead of being added with the alkali, may be mixed with the agar before the latter has set, a few drops sufficing for a large quantity of the medium. Papain : Its Commercial Preparation and Digestive Properties.D. S. Pratt. (Philippine J. Sci., 1915, 10, 1-33.)-Ceylon papain, prepared by drying the latex of the fruit, is dark brown to nearly black in colour, owing apparently to the presence of an oxydase ; lighter grades are grossly adulterated generally by the addition of boiled rice starch; occasionally the dark and light grades are blended in the same sample, Mexican papain, more carefully prepared, is lighter brown in colour, and the best West Indian products resemble dried bread-crumbs. For the valuation of the proteolytic activity, skimmed milk is the best substratum ; the author uses a 40 per cent.solution of sweetened condensed separated milk.The papain gum is not compIetely soluble in water : 0.75 grm. of powdered papain is digested with 150 C.C. of water at 40'C. for thirty minutes, and the solution filtered. For the standard test, 25 C.C. of milk solution and 23 C.C. of water are mixed with 2 C.C. of filtered papain solution, equivalent to 10 mgrms. of the dry sample, and the mixture is digested for thirty minutes st 40" C.At the end of that time, 20 C.C. of ice-water are added, and the flask is immediately cooled in an ice bath. The liquid is transferred to a beaker, and the undigested protein precipitated by slowly adding 0.5 C.C. of copper sulphate solution (60 grms. per litre), followed by 0.5 c.c, of glacial acetic acid with vigorous stirring.The contents of the beaker are placed in a 100 C.C. measuring cylinder; allowed to settle, and filtered through an ashless filter-paper 11 cm. in diameter, previously dried at 100" C. and tared. The curd is broken up with a rod, washed with water at 60" C., then dried at 100" C. and weighed. The protein digested is calculated by comparison with a blank experiment, and the pro- teolytic activity is expressed in terms of protein digested per unit weight of the sample on an average of six determinations; duplicate results should agree within about 2 per cent.The following results for activity numbers are recorded : (1) Com- mercial specimens, Ceylon, 0.1, 5.6, 9.6, 5.7, 22.0, 1.8 ; Mexico, 12.9 ; West Indies, 40.0. (2) Prepared in laboratory, Philippine fresh latex (calculated on dry substance) 45.8 ; ditto, sun-dried, 45.4; precipitated by alcohol, 72.2.With the weaker pre-406 ABSTRACTS OF CHEMICAL PAPER8 parations an increase in the quantity of papain employed increases the activity number ; but with stronger specimens an increase in the quantity produces a very marked decrease in the activity per unit weight. The digestion of milk protein with papain at 40” C.proceeds rapidly during the first ten minutes, and practically reaches its maximum within an hour under the conditions specified. The addition of hydro- chloric acid up to 0.06 per cent. has only a slight retarding influence on the digestion, but quantities from 0.06 to 0.13 per cent. very greatly reduce the activity of the enzyme, while a further increase up to 0.20 per cent.has practically no further effect. Sodium bicarbonate and sodium chloride in small proportions have no influence on the digestion. Hydrocyanic acid exerts a marked stimulating effect. Papain has a slight activity at 0” C., and at 70’ C. its action in presence of large amounts of the enzyme is not greatly weakened. J. F. B. Estimation of Pepsin. L.J. Geselschap. (Zeitsch. physioZ. Chem., 1915, 94, 193-226; through J . SOC. Chom. Ind., 1915, 34, 848.)-The author investigated various methods for the estimation of pepsin in gastric juice. Those of Volhard and Fuld and Levison were found least satisfactory. Sufficiently accurate results can be obtained by Mett’s method, which is based on the measurement of the decrease in length of threads of coagulated egg albumin enclosed in short lengths of glass tubing during twenty-four hours’ digestion, and also by Griitener’s method (Pfluger’s Arch., 144, 545), in which fibrin stained with carmine is digested for a short time, and the amount dissolved estimated from the colour of the liquid. The latter method is preferable where a rapid estimation is desired or where the peptic activity of the juice investigated is small.Pepsin preparations obtained from the mucous membrane of pigs’ stomachs by Pekelharing’s method (Zeitsch. physiol. Chem., 1896, 22, 233 ; 35, 8) can be used as a standard in these determinations, as they are very uniform in activity and can be kept for a long time without deteriorating. Estimation of the Acidity of Urine.J. Clarens. (Compt. rend., 1915, 160, 814-817.)-The alkaline or acid reaction of urine is governed by that of the blood, and the active elements involved may be expressed in terms of sodium carbonate on the one hand and monosodium dihydrogen phosphate on the other. The direct titration of such a system with standard sodium hydroxide in presence of phenol- phthalein may lead to quite erroneous results, which are influenced by the absorp- tion of carbon dioxide from the sir or by the expulsion of carbon dioxide through agitation when liberated by the mutual reaction of the components.A simple method for the estimation of the actual equilibrium of acid and basic constituents of the urine is described: A measured volume of urine is treated with a known quantity of Tc hydrochloric acid, boiled to expel the carbon dioxide, and then im- mediately cooled; the excess of mid is titrated with & sodium hydroxide in presence of pbenolphthalesn. The volume of standard acid is subtracted from the volume of alkali used. If the result is positive, the urine is acid; if negetive, it is alkaline.Thus sodium carbonate and bicarbonate are regarded as equivalent in the basic sense, and such a view is physiologically correct.In carrying out the estimation, the ebullition should not be prolonged so as to cause a loss of volatile acidsBACTERIOLOGICAL, PHYSIOLOGICAL, ETC, 407 hydrolysis of the urea. The titration should always be performed in the cold on account of the presence of ammonium salts. If the liquid become deeply coloured as the result of boiling, it should be diluted with recently boiled water before titration.J. F. B. Estimation of Indican in Urine. A. Jolles. (Zeitsch. physiol. Chm., 1915,94, 79-103 ; through J. Soc. Chem. Ind., 1915, 34, 851.)-Indoxyl condenses with thymol in presence of ferric chloride and hydrochloric acid to form a compound, C,,H,@$, probably 4-cymene-2-indolindolignone (Friedlander's nomenclature), which forms red crystals melting with decomposition at 218"-220° C., and yields an intensely violet monohydrochloride which is very readily hydroly sed.This reaction can be applied to the detection or estimation of indican in urine. Ten C.C. of the urine are mixed with 1 C.C. of a 5 per cent. solution of thymol in alcohol, and 10 C.C.of funling hydrochloric acid containing 5 grms. of ferric chloride per litre, and after fifteen minutes the mixture is extracted with 4 C.C. of chloroform, which is coloured violet if the urine contained as little as 0.0032 mgrm. of indican. For quantitative purposes, the urine is treated with one-tenth of its volume of basic lead acetate solution and filtered; 5 to 10 0.0. of the filtrate are mixed with the thymol and ferric chloride solutions in the same proportions as for the qualitative test, and after standing for two hours the liquid is extracted with portions of 5 C.C. of chloroform SO long as the extracts are coloured. The united extracts are washed once with water, whereupon the colour changes to reddish-brown owing to hydrolysis of the hydrochloride, once with very dilute alkali (a& to &), and once again with water. Any colouring matter in the first water washing is extracted by a few C.C. of chloro- form, which is then washed with alkali with the rest. The total extract is made up to 25 or 50 C.C. with chloroform and compared colorimetrically with a suitably diluted standard solution containing 0.01 grm. of the colouring matter (correspond- ing to 0.009 grm. of indican) in 100 C.C. of chloroform.

ISSN:0003-2654    

DOI:10.1039/AN9154000403

出版商:RSC    

年代:1915

数据来源: RSC

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BACTERIOLOGICAL, PHYSIOLOGICAL, ETC, 407 ORGANIC ANALYSIS. Estimation of Carbon in Carborundum and the Like. S. A. Tucker and A. LOWJT. (J. Ind. and Eng. Chem., 1915, 7, 565-571.)-This method was devised for the analysis of 6tsilunduru,” which is shown to exist in two modifications, approximating to the composition Sic (a variety of carborundum) and Si,C,O, the title of the paper in which the method is described being “The Preparation, Properties, and Composition of Silundum.” The difficulty in estimating carbon in such materials lies in their resistance to decomposition by ordinary methods.After trying other methods with indifferent results, the authors found that litharge was an excellent flux for decomposing and partially oxidising the material, complete oxidation being effected by means of a stream of oxygen.The sample (0.2 to 0.25 grm.) is mixed with 5 grms. litharge, the carbon content of which has been determined in a, blank test under the same conditions as the analysis. The mixture is placed in a combustion-boat of vitrified clay, 120 rnm. long and 15 mm. wide. These boats, designed by C. M. Johnson408 ABSTRACTS OF CHEMICAL PAPERS and made by Eimer and Amend, New York, were the only ones found suitable, porcelain, nickel, iron and copper all being fused by the molten litharge.The boat is placed in a silica tube in an electric furnace, a current of dry oxygen, free from carbon dioxide, is passed through the tube and the temperature raised cautiously, switching off the current if the rate of evolution of gas tends to become too rapid.The temperature is kept at about 800" C. for forty-five minutes and then gradually raised to l,OOOo C., any carbon monoxide formed at this temperature being oxidised by passing over a heated coil of cuprio oxide, The gases are dried by means of sulphuric acid and the carbon dioxide is absorbed in a suitable apparatus containing potassium hydroxide, the authors preferring Vanier's apparatus.With large crystals of carborundum as test material, the method appears to be accurate to 1 per cent. on the carbon, assuming that the carborundum was pure silicon carbide. One of the forms of silundum gave results much nearer tbe theoretical (found C = 2949 ; required by Sic, 29.78). Duplicates agree well, for example 29.89, 29.95, 29.84.G. C. J. Estimation of Benzol in Gas. A. Krieger, (Chem. Engineer, 1915, 21, 252-253.)-By benzol in this connection is understood the sum of the benzene, &==5 to absorb more than toluene, xylenes, etc. Earlier methods are reviewed, and it is pointed out that, however satisfactory they may be in gas works, they are insufficiently exact for coke oven works. Even crude coke oven gas contains iess beneoi than ordinary illumi- nating gas, and washed gas sbould only contain about 7 per cent. of the amount present in the crude gas.The constant problem of the coke oven manager is to see that his washers, usually guaranteed to extract 90 per cent. of the benzol, are in fact working efficiently. None of the earlier methods are of service in such circumstances, and most of them require the presence of a skilled chemical manipulator.The method recommended is condensation by washing wibh a suitable oil, cooled to - 1 8 O C. A tar oil distilling between 240° and 260° C., or paraffin oil boiling between 200" and 300" C., is suitable. Such oil will absorb nearly one-tenth of its weight of beneol, but in practice should not be required 2 per cent.of its weight. A suitable washer is figured. The cylinder is 9" x 2", and is charged with 50 C.C. of oil. The outlet tube ( A ) is 6" x &"* is packed with glass beads (2 mm.), and has a hole in the bottom, and a ring of small holes for the inflow of gas. Two such washers are used in series, and gas is passed through them at the rate of 40 litres per hour. The duration of the test will depend on the concentration of benzol in the gas and other local conditions.In the author's practice, an eight hours' run is made, about 0-8 grm. benzol being absorbed by the first washer and 0-05 grm. by the second. With the speed of gas indicated and providing the oil in the first washer has not absorbed more than 1 grm of benzol, a third washer shows a0 The beads prevent mechanical losg of oil.ORGANIC ANALYSIS 409 increase in weight.The only other apparatus required is 8r meter and a balance sensitive to 0.01 grm. G. C. J. Detection of Cinnamic Acid. D. Schenk and H. Burmeister. (Pharm- Zeit., 1915, 60, 213-214; through J. Chem. Soc., 1915, 108, II., 382.)-The test recommended depends on the oxidation of the cinnamic acid to benzaldehyde, and the identification of this by its odour and by its reaction with phenol and sulphuric acid.The substance to be tested is acidified with phosphoric acid and extracted with ether ; the ethereal solution is then shaken with sodium carbonate solution, the aqueous layer is separated, extracted twice with ether (this is essential, particu- larly in the case of fruit juices, in order to remove small quantities of furfurah compounch), and very dilute potassium permanganate solution is added, drop by drop, until the pink colour is only just discharged.The solution is now extracted with ether, the ethereal solution is treated with 10 drops of an ethereal 5 per cent. phenol solution, allowed to evaporate at the ordinary temperature, and a, few drops of concentrated sulphuric acid are added to the residue.A yellow coloration is obtained, even when the quantity of benzaldehyde formed from the cinnamic acid is too small to be identified by its odour. The furfural compounds which may be present give, if not removed completely, a faint orange coloration, which cannot be mistaken for that yielded by benzaldehyde. Reagents for Use in Gas Analysis, I.Alkaline Pyrogallol. R. P- Anderson. (J. Ind. and Eng. Chem., 1915, 7, 587-596.)-The report of an elaborate investigation as to the best composition for this reagent, A solution of 15 grms- pyrogallol in 100 C.C. of potassium hydroxide solution of specific gravity 1.55 is recommended. Solutions containing more potassium hydroxide are less easy to prepare and less easy to manipulate, whilst solutions containing more pyrogallol tend to foam.I t is desirable to use solutions as concentrated as is convenient, not only because the life of such solutions is longer, but because several observers have called attention to the fact that solutions of pyrogallol of relatively low alkali content tend to react with oxygen with production of carbon monoxide.The solution recommended is free from this defect, so far as can be judged using Hempel's apparatus for technical analysis. When used at 20-24" C., a solution that has already absorbed 26 times its volume of oxygen will still absorb the whole of the oxygen from a sample containing 90 per cent. of that gas in two minutes, when shaken in a Hempel double pipette. If three minutes be allowed the specific absorption is some- what higher (30), whilst it is higher still (31) if the reagent is not required to absorb the oxygen from samples richer in that gas than air is.The author is unable to confirm Hempel's statement that potassium hydroxide purified by alcohol should not be used. As that statement was made as long ago as 1887, it is possible that differences in method of manufacture explain the discrepancy.Sodium hydroxide cannot be substituted for potassium hydroxide. Using a solution of sodium hydroxide as concentrated as was practicable, it was found that only 10 per cent. of the oxygen in a sample of gas was absorbed as the results of three minutes' shaking. 0. C. J.410 ABSTRACTS OF CHEMICAL PAPERS Volumetric Estimation of Nitro-Compounds.A. J. Berry and C. K. Colwell. (Chem. News, 1915, 112, 1-2.)-The method is the known one of reduction by means of a known amount of stannous chloride and titration of the excess of stannocs' chloride, the novelty consisting in the manner in which the excess of stannous chloride is estimated. For this purpose a standard solution of copper sulphate is employed, and, to determine the endpoint, advantage is taken of the fact that, in presence of much hydrobromic acid, a very small amount of a cupric salt imparts a pronounced orange-yellow colour to a, comparatively large volume of solution.The copper solution conveniently contains about 40 grms. copper per litre, and is made by dissolving a weighed amount of copper sulphate and about 100 grms.of potassium bromide in 1,000 C.C. of dilute (1 : 1) hydrochloric acid. The stannous chloride solution is made up roughly equivalent to the copper solution. A suitable quantity of an aqueous solution of the nitro-compound (only water soluble compounds are dealt with) is measured out, 25 C.C. of stannous chloride solution, 35 C.C. of a 50 per cent. solution of potassium bromide, and a considerable excess of hydroohloric acid, are added, and the mixture boiled for fifteen minutes in an atmosphere of carbon dioxide. The excess of stannous chloride is then titrated with the copper solution as described. The difference between the volume of copper solution required in this experiment and in one similar, except that water is sub- stituted for the solution of the nitro-compound, is the measure of the latter.In the author's test experiments, these differences were small (7 to 14 c.c.), and their results only accurate to +2 per cent. G. c. 3. Analysis of Chinese Wood-Oil Varnishes, E. E. Ware and C. L* Schu- mann. (J. Ind. and Eng. Chem., 1915,7,571-573.)-1n the study of the polymerisa- tion of China wood-oil in presence of rosin, it became necessary to devise a method for separating the various possible constituents of the final mixture.Twitchell's method, depending on formation of the ethyl esters of the fatty acids, and their sub- sequent separation from the rosin and from each other, gave a fair separation of the oils from the rosin, but the esters of the polymerised and unpolymerised oils did not show sufficiently pronounced differences upon which to base a method for their separation. The following method served well : The sodium soaps of the fatty acids of both the raw and heat-treated oils are insoluble in absolute alcohol, whilst sodium resinate is soluble.If proper precau- tions (not specified in the paper) be taken for the control of temperature and con- centration, the soaps of the fatty acids precipitate in a, suEciently granular form to permit of ready filtration and washing.The subsequently freed fatty acids may be dissolved in warm 80 per cent, alcohol, from which the comparatively insoluble elaeomergaric acid may be crystallised by cooling. These characteristic crystals of elseomargaric acid may be filtered and weighed, or the residue acids may be weighed and the elaeomargaric acid computed by difference.The oxyacid present may be separated from the residue by precipitation from petroleum ether. In this way it is possible to estimate total fatty acid, unpolymerised acid, oxyacid, polymerised acid, and unsaponifiable matter. G. C. J.ORGANIC ANALYSIS 411 Demulsification Values of Mineral Lubricating Oils for Use in Steam Turbines.(J. Xoc. Chem. Ind., 1915, 34, 697-701.)-The leakage of water into the oil system in steam turbines tends to form emulsions which cause. trouble in- the lubrication, especially when the water contains large proportions of salt derived from sea-water or shore-water. Electrolytic corrosion of the machinery may then occur. I t has been found in practice that two samples of lubricating oils.may differ but slightly in their chemical and physical properties, and yet one will be- suitable and the other useless as a turbine lubricant. I n order to test the suitability of oils for this purpose, the author determines the 6'demulsification value" in a, special apparatus. This consists of an agitator, driven at high definite speed (350 to 400 revolutions per minute) for a definite time (five minutes) by means of an' electric motor, in a mixture of 500 C.C.of the oil with 500 C.C. of water at 100" C. At the end of the given period the mixture is transferred to a graduated glass measure, and after a fixed period (twenty-four hours) the volume of the separated oil. is read off and calculated as a percentage of the oil originally present.Oils giving. demulsification values of 90 per cent. or over have been found to give no trouble due. to formation of emulsions under the practical conditions of use of a forced lubricating system on steam turbines. The addition of 1 per cent. of undistilled fuel oil to. a high-grade lubricating oil lowers the demulsification value, possibly owing to the. bitumen in the former.The following table gives the actual analysis of a mineral lubricating oil of high grade, and the imaginary results of an oil fuel and of a mixture. of the lubricating oil with 1 per cent. of the oil fuel : A. Philip. Sp. gr. at 60' F. ... ..I ... Flash-point . . . ... ... ... Viscosity at 70' F. (seconds) ... Free acidity to water (as oleic acid) Sulphur . . . .....I ... Iodine value.. . ... ... 0 . . Saponification value ... ... Bitumen ... ... .*. ... Paraffin wax.. . ... ... ... Demulsification value . . . ... 1. High-class Special Mineral Lubricating Oil. 0.8870 403" F. 675 nil. 0.109 per cent. 16.2 0.28 nil. nil, 96 per cent. 2. Imaginary Oil Fuel, all Besults being Extreme Values. 3. Calculated Values for Mixture 1 per Cent. of 2 with 99 per Cent.of 1. 0-9685 180' F. 2586 0.5 per cent. 3.98 per cent. 100.0 6.0 38.0 27.5 nil. 0.8779 400.7O F. 694.1 0.005 per cent. 0.147 per cent.. 17.03 0.33 0.38 0.275 nil. I n cases where contamination of an oil with minute quantities of fuel oil has been suspected, the demulsification test has been found to aff'ord the only clear proof of difference between the oil as accepted and as delivered.The addition of paraffin wax has not been found to decrease the dernulsification value, and in some cases may- even increase that value. C. A. M.412 ABSTRACTS OF CHEMICAL PAPERS Specification of Vuleanised Rubber Gum by Volume and its Estima- tion by a New Solution Method. F. Gottsch. (J. Ind. and Eng. Chem. 1915, 7, 582-586.)-1t is said that the physical properties of a rubber compound and its quality are more properly related to the percentage by volume of vulcanised rubber gum present than to the percentage by weight, that the large majority of rubber goods are sold by bulk and used by bulk rather than by weight, and that this volume conception is necessary to an understanding of rubber mixings.The author would therefore introduce this conception into specifications and into analytical reports to show whether goods comply with the specification.The specific gravity of vulcanised rubber is so nearly unity that it suffices to multiply the percentage of vulcanised rubber-gum found by analysis by the specific gravity of the sample. Whether the percentage of vulcanised rubber be specified by weight or by volume, the specification must include methods of analysis or a reference to known methods.The author describes the methods in use in the City of New York Department of Water Supply, Gas, and Electricity. Vulcanised rubber-gum by weight is defined as the difference between 100 and fhe sum of the free sulphur, organic acetone extract, mineral fillers and corrected foreign matter.” In the estimation of mineral fillers many solvents for rubber were tried, and the best found to be salol.Many of the fillers used (“fume pigments”) are in such an extremely fine state of division that without a coagulant it is extremely difficult to filter them off. Such a coagulant is found in a solution of soluble cotton in amyl acetate. One grm. of the sample is extracted with acetone for four hours, dried in a steam oven and transferred to a 100 C.C.becker. The thimble is burnt and the ash added to the contents of the becker. Melted salol (about 50 grms.) is next added and the mixture heated to 120’ to 150” C. until the rubber is dissolved. About 2 C.C. of a 1 per cent. solution of soluble cotton in amyl acetate are added, the mixture cooled and coagulated by stirring in 75 C.C.or more redistilled turpentine. After allowing the flock to settle, the supernatant liquid is decanted through an alundum crucible. The insoluble matter is washed by decantation and on the filter with turpentine, finally using a, little acetone to dissolve the soluble cotton. The crucible is dried at 105” to 110’ C. All filtrates and washings are evaporated, the residue ignited and weighed, and the weight of mineral matter thus recovered added to that in the crucible.The usual methods for the estimation of free sulphur are criticised and a new one proposed. I t is an application to this purpose of a well-known method for the estimation of total sulphur, the organic matter in the acetone extract being destroyed by fusion with sodium peroxide and potassium carbonate, the sulphur then being estimated as barium sulphate with the precautions usual when such an estimation follows a, peroxide fusion.G . C. J. Analysis of Tanning Materials. TI Callan. (J. SOC. Chem. 17d., 1915, 34, 646-647.)-1n the course of a number of analyses of various tanning materials, it was found that the non-tannin filtrates obtained in Bennett’s method (ANALYST, 1915, 132), using standard American hide powder, showed in many cases distinctINORGANIC ANALYSIS 413 traces of tannin, even after shaking for twenty minutes with hide powder, when tested by concentrating 6 C.C. of the detannised solution to 3 C.C. and applying Stiasny’s test (addition of 1 C.C. of saturated sodium chloride solution, 2 drops of 1 per cent. metaphosphoric acid solution, and 2 drops of 5 per cent. gelatin-5 per cent. sodium chloride solution). Tannin could not, however, be detected in the solution by means of the official test (addition, drop by drop, of a 1 per cent. gelatin -10 per cent. sodium chloride solution). I t would appear that the alterations proposed by Bennett, designed to reduce absorptions of non-tannins, have been carried too far, and although in all probability the gain in accuracy, owing to reduced absorption of non-tannins, is more than the error introduced by the non- absorption of traces of tannin, the presence of this latter error will prove a strong objection to the method. w. I?. s.

ISSN:0003-2654    

DOI:10.1039/AN9154000407

出版商:RSC    

年代:1915

数据来源: RSC

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INORGANIC ANALYSIS 413 INORGANIC ANALYSIS. New Method of Estimating Bromine and Chlorine in Organic Com- pounds. P. W. Robertson. (J. Chem. SOC., 1915, 187, 902-907.)-The method depends on the fact that organic substances containing chlorine or bromine give these elements up entirely in a volatile form when treated with a mixture of chromic acid and sulphuric acid. In the case of bromo-compounds, bromine itself and a small quantity of hydrogen bromide are liberated, and may be absorbed in alkaline hydrogen peroxide, which converts the whoIe of the bromine into alkali bromide, After acidifying the solntion with.nitric acid, the bromide is titrated according to Volhard’s method. When chloro-compounds are treated in the same way, the volatile products contain chlorine, hydrogen chloride, and chromyl chloride.These may be similarly absorbed in alkaline hydrogen peroxide, and, after the reduction of the chromate, the chloride in the solution is titrated. The method is carried out as follows: A quantity of the substance is weighed into B flask provided with a ground-in stopper carrying an inlet tube and an outlet tube, the latter being con- nected with two absorption vessels containing a mixture of hydrogen peroxide and sodium hydroxide solution.About 5 grrns. of chromic acid are added to the flask and 25 C.C. of sulphuric acid are introduced through the inlet tube. A slow current of air is then aspirated through the apparatus. In most cases the decomposition begins a t once, and should be checked by external cooling if it tends to become violent, After the initial reaction has subsided the contents of the flask are heated for about forty-five minutes while air is drawn continuously through the apparatus.The contents of the absorption vessels are then rinsed into a flask. In the case of a bromo-compound, the solution is acidified with nitric acid, an excess of silver nitrate solution is added, and the excess titrated, in the presence of the silver bromide, with thiocysnate solution in the usual way.If chlorine is being estimated, the solution is heated nearly to boiling and neutralised with nitric acid. In the presence of the hydrogen peroxide, the chromate is reduced to a chromic salt which at the dilution of the experiment is practically colourless. Excess of TG silver nitrate solution is now added, the solution is filtered from the silver chloride (which reacts with thiocyanate), and the excess of silver estimated in the filtrate.The414 ABSTRACTS OF CHEMICAL PAPERS silver nitrate and thiocyanate solution should be standardised against pure potas- sium bromide under exactly the same conditions as those of the experiment. Certain compounds, such as the bromo-benzenes, etc., give low results, owing t o the volatilisation of the unchanged substance from the sulphuric acid mixture, but accurate results may be obtained in these cases if a small tubs containing platinised asbestos is placed between the reaction flask and the absorption vessels, and the volatile matter burnt in a current of oxygen.The method yields trustworthy results ; it is not, however, applicable to the estimation of iodine, since a large quantity of the latter is converted into iodic acid.The reaction may be used as a qualitative test for bromine and chlorine in organic compounds. A small portion of the substance is heated in a test-tube with, chromic acid and sulphuric acid, and the evolved gases are absorbed in dilute alkali solution.10, the case of chloro-compounds, the alkali solution is coloured yellow owing to the formation of a chromate, and this distinguishes chlorine from bromine. Bromine is detected by the addition of nitric acid and silver nitrate. W. P. S. Deteetion of Cobalt by Means of a-Nitroso-P-Naphthol. F. W. Atack, (J. SOC. Chem. Ind., 1915, 34, 641-643.)--The use of a-nitroso-@naphthol (,@-naphtha- quinone-a-oxime) in alcohol or acetic acid solution as a reagent for cobalt was first suggested by Ilinski and Knorre (Ber., 1885,18,699), but the reagent is unstable and, in certain circumstances, is unreliable.The author finds that the sodium salt of the oxime is much more stable in solution, and provides a very sensitive reagent for cobalt. The soiution recommended €or use is prepared by boiling 0.1 pa.of a-nitroso- P-naphthol with 20 C.C. of water, to which has bean added 1 C.C. of dilute sodium hydroxide solution, filtering the mixture, and diluting the filtrate to 200 C.C. In carrying out the test, 1 C.C. of ammonium chloride solution and 1 G.C. of the reagent are added to the neutral or slightly alkaline solution under examination; a n orange or claret coloration, or a red precipitate, is formed if cobalt is present.The coloration and precipitate are not affected when the mixture is acidified with dilute sulphuric. acid, The test will detect the presence of 1 part of cobalt in 1 millioti parts of water. Even smaller quantities of cobalt may brt detected by using a reagent of one-fifth the concentration mentioned above and comparing the test with a ‘‘ blank.” The colora- tions obtained with salts of nickel, iron, etc., are all destroyed on acidifying the mixture with sulphuric acid, and it is immaterial whether the cobalt is preseut in t h e solution as nitrate or other salt.The test is not affected by the presence of manganese or zinc, but large quantities of nickel interfere with the coloration pro- duced by cobalt ; in such cases the concentration of the nickel should be reduced previously by precipitation with an alcoholic solution of dimethylglyoxime (ANALYST, 1905, 30, 378) or a-benzyldioxime (ibid., 1913, 38, 316).As the presence of either of these reagents in excess gives rise to a cobalt salt which will not react with the nitrosonaphthol, it is essential to separate the nickel only partially.Further, the w. P. s. test is not affected by the presence of citric and tartaric acid. Reduetion of Copper Oxide in Alcohol Vapour. A, Wedderburn. (J. Ind. and Elzg. Chem., 1915, 7: 610-611.)--Cuprous oxide is collected on a porcelainINORGANIC ANALYSIS 415 Gooch crucible or on an alundum fitering crucible, washed with hot water followed by alcohol, the whole being then heated to redness for a sufficient time to burn off any accompanying organic matter.The crucible is allowed to cool until the redness begins to disappear, and is then immersed in an atmosphere of alcohol vapour in the following manner: A tripod support is placed a t the bottom of a 400 C.C. metal beaker. Strong alcohol is poured into the beaker sufficient to cover the bottom to the depth of about 1 cm., and the beaker is then covered with a watch glass.The alcohol is heated to boiling, and the hot crucible is then immersed in the beaker and allowed to rest on the tripod support. The alcohol is allowed to continue to boil for a moment, and then the flame is extinguished. I n about three or four minutes complete reduction will have taken place ; the final cooling of the crucible may then take place in a, desiccator.H. F. E. H. Purification of Commereial Hydrochloric Acid. A. Coignard. (Ann. Chim. anal., 1915, 20, 145-146.)-The method of Duflos is recommended as the most suitable for general purposes. The crude acid is diluted to sp. gr. 1.135, and a pinch of manganese dioxide or potassium chlorate added to oxidise any sulphurous acid.I t is then left for twenty-four hours at 30" C. in contact with fine strips of copper. At the end of this time these are cleaned and again placed in the acid for twenty- four hours. This removes all arsenic, and reduces ferric chloride to ferrous chloride. The acid is now decanted and distilled in the presence of a few fragments of copper.Any antimony will be left in the retort. C. A. M. Volumetric Estimation of Lead, F. D. Miles. (J. Chern. SOC., 1915, 107, 988-1004.)-The method depends on separation of the lead as sulphate, decomposition of the sulphate by means of hydrogen sulphide, and titration of the liberated sulphuric acid. Tin and antimony: if present, must be first separated by taking advantage of the solubility of their sulphides, as lead cannot be separated from these metals by precipitation as sulphate.In absence of these metals, and of barium, iron, and bismuth, the analysis is conducted as follows : The ore (preferably so much as contains about 0-4 grm. of lead) is treated with boiling, slightly diluted (2 : 1) hydrochloric acid, adding nitric acid towards the end if pyrites is present.The solution is evaporated with 3 to 5 c,c. sulphuric acid until fumes arise, the residue is taken up with 50 C.C. water, the mixture boiled, allowed to cool, and filtered through a 7 cm. filter, which is then washed with 5 per cent. sulphuric acid, and four times with 50 per cent. alcohol. Paper and precipitate are then transferred to a 300 C.C. conical flask, and covered with about 40 C.C.(or 10 C.C. per decigram of lead) of a saturated solution of hydrogen sulphide. The upper part of the flask is flamed to expand the gaseous contents, and the mouth is then closed with a rubber stopper. The contents of the flask are shaken vigorously, and heated over the flame until as hot as the hand can comfortably bear (50" C.). This tempera- ture is maintained for at least twenty minutes by occasional reheating, shaking vigorously each time.The contents of the flask are then cooled under the tap, and the stopper removed. Unless there is a marked odour of hydrogen sulphide, the experiment should be repeated, using more. The flask should not be left overnight,416 ABSTRACTS O F CHEMICAL PAPERS or mercaptan may be formed, and low results obtained.The liquid is rapidly filtered free from lead sulphide on a pulp filter, which is wasbed twice with water. The filtrate is boiled for two minutes to remove hydrogen sulphide, cooled, and titrated with & or When the lead sulphate is mixed with much other finely divided insoluble matter-for example, calcium sulphate-washing with alcohol is tedious, and may be omitted.I n such cases the filter and its contents are shaken with water to disinte- grate the filter, and the mixture neutralised with sodium hydroxide. The treat- ment with hydrogen sulphide is then proceeded with as described, but a small oorrection must be made, probably because the sulphuric acid adhering to the filter is not completely extracted during the preliminary neutralisation, but a, trace then left unneutralised passes into solution during the subsequent operations.Unless a correction be made, the results will be too high, In the author’s experiments, with approximately 0.4 grin. lead present, the error of the uncorrected results was almost constant, and amounted to 1.5 mgrm. In presence of iron, precipitates of lead sulphate are invariably contaminated with iron, the colour of the precipitate being no guide to the amount of iron carried down.With ores containing much iron, therefore, the following modification is recommended : After evaporating with sulphuric acid, diluting, and cooling, the supernatant liquid is decanted off through a filter, the precipitate washed by decan- tation with 5 per cent.sulphuric acid, and redissolved by heating with 15 C.C. hydrochloric acid and 10 C.C. water. Sulphuric acid (5 c.c.) is added, and the mixture once more evaporated, the resulting lead suiphate being substantially free from iron. Barium even in small proportion interferes, owing to the fact that barium sulphate crystallises around the lead sulphate and protects it from the action of hydrogen sulphide.If not present in greater amount than 25 per cent. (on the lead), its interference may be obviated as follows: The evaporation with sulphuric acid is continued to dryness, the residue is taken up in 10 C.C. of water, the lead sulphate dissolved by heating nearly to boiling for ten minutes with 10 C.C. of 30 per cent. sodium hydroxide, and reprecipitated, after cooling, by addition of 50 C.C.of dilute (1 : 5 ) sulphuric acid. Bismuth even in small amount (5 per cent. on the lead) leads to lead being over- estimated by about 1 per cent. If 10 C.C. of sulphuric acid, instead of 5 c.c., be used in the evaporation to counteract the tendency to the formation of basic salts, the error is no greater even with nearly as much bismuth as lead present, but it cannot be wholly eliminated by any known means.The method is more accurate than Alexander’s original molybdate method, and quicker than Low’s modification of it (Technical Methods of Ore Analysis, 1911, 149). A single analysis can be completed in two hours, and the maximum error should not exceed 0.2 per cent. on the lead. sodium hydroxide (1 C.C. - = 0.01035 grm.lead). G. C. J. Colorimetric Estimation of Phosphoric Aeid. E. Riegler. (BUZZ. Acad. Sci. Roumanie, 1914, 2, 272-275; through J . Chem. Soc., 1915, 108, II., 368-369.) -A colorimetric method is described depending on the blue coloration producedINORGANIC ANALYSIS 417 when ammonium phosphomolybdate is reduced by warming with a solution of hydrazine sulphate; the intensity of the colour is proportional to the amount of phosphoric acid present. A comparison solution is prepared by dissolving 0.505 grm.of crystallised disodium phosphate in 100 C.C. of water. One C.C. of this solution is placed in a graduated centrifuge tube, 1 C.C. of nitric acid (sp. gr. 1,125) and a quantity of 30 per cent. ammonium nitrate added to fill the tube to the tenth mark, then the tube is heated and 2 C.C.of 3 per cent. ammonium molybdate solution is added, thoroughly mixed, and the solution centrifuged for two minutes. The clear solution is poured off, and the precipitate shaken with 30 per cent. ammonium nitrate solution, and again centrifuged for two minutes, and the clear solution poured ofl. The precipitate is then washed into a 100 C.C. flask by means of a 2 per cent.solution of hydrazine sulphate (20 c.c.), and the solution warmed. The flask is then cooled, and filled to the mark with distilled water; 1 C.C. of this solution is equivalent to 0.00001 grm. P,O,. The solution to be analysed is treated in the same manner, and the two solutions are compared in a colorimeter. Colorimetric Estimation of Phosphorus in Soil Extracts. C.E. Miller and F. A. Gangler. (J. Ind. and Eng. Chem., 1915, 7, 619.)-The colorimetric method of Veitch (J. Amer. Chem. SOC., 1903, 25, 169), as perfected by Schreiner and BrOwn (ibid., 1904, 26, 1463), is shown to give identical results in duplicate deter- minations when conducted with the precautions shown to be necessary by Veitch. The use of measured quantities of molybdate reagent and of nitric acid is essential, too high a concentration of the latter almost bleaching a soIution with a pronounced colour.For filtering the solution after removal of silica, an ash-free paper must be used, neglect of this precaution involving possibility of error of the order of 100 per cent. The soil is rubbed with five times its weight of water for three minutes, and after forty minutes the suspension is filtered through a Chamberland filter.Of the fYtrate, 50 C.C. is freed from silica, and the phosphoric acid estimated colorimetrically. I t is not claimed that the method is accurate to more than 10 per cent. on the small amounts of phosphorus to be estimated. Where these are very small duplicate results may stand in the ratio of 4 : 5.G. C. J. Factor to be Used for the Calculation of the Phosphoric Acid in Neumann’s Method. S. L. Jodidi. (J. Amer. Chem. SOL, 1915, 37, 1708-1710.) -In Neumann’s method, which consists in precipitating the phosphoric acid as ammonium phosphomolybdate, boiling the yellow precipitate with an excess of $ sodium hydroxide solution to expel the ammonia, and titrating the excess of the alkali added, each C.O.of sodium hydroxide solution should be equivalent to 0.554 mgrm. of phosphorus, this factor being calculated on the assumption that the precipitate has the composition 12MoO,.(NH4),P0,.2HNO,. As the result, however, of estimations of phosphoric acid in pure phosphates, the author finds that this factor is too low, and that it should be 0.57. w. P. s.Estimation of Uranium and Phosphorus. H. D. Newton and J. L. (J. Amer. Chem. SOC., 1915,37,1711-1715.)-1n the method proposed the Hughes.418 ABSTRACTS OF CHEMICAL PAPERS uranyl salt in sulphuric acid solution is reduced by titanous sulphate, the excess of the latter oxidised with bismuth trioxide, the excess of bismuth removed by filtra- tion, and the solution then titrated with permanganate solution.The method may be applied to the estimation of phosphorus as phosphates after the phosphoric acid has been precipitated as ammonium uranyl phosphate. The method as applied to the estimation of phosphorus is as follows : The phosphate solution is treated with 10 grms. of ammonium acetate and 5 C.C. of glacial acetic acid, the mixture diluted to 150 c.c., heated nearly to boiling, and an excess of uranyl nitrate solution is added slowly with constant stirring, The mixture is kept hot for thirty minutes, then cooled, the precipitate collected on a filter, and washed with 2 per cent.ammonium acetate solution. The precipitate is then dissolved in 16 per cent. sulphuric acid, the solution treated with titanous sulphate solution, bismuth trioxide is added in excess, the mixture filtered, and the filtrate titrated with standardised FG perman- ganate solution, w.P. s. Estimation of Polythionic Acids by Potassium Iodate. G. S. Jamieson. (Chem. News, 1915, 112, 2-3.)-A suitable volume (according to its strength) of thiosulphate or tetrathionate is mixed in a stoppered bottle with so much slightly diluted hydrochloric acid that the mixture contains from 15 to 20 per cent.of hydrogen chloride. In the case of thiosulphate, the diluted hydrochloric acid should be cooled, and not so strong that on mixing with the thiosulphate solution the temperature rises above 18" C. A small quantity (6 c.c.) of chloroform is added, and then standard potassium iodate solution from a, burette, at first rapidly, until the iodine liberated reaches a maximum and then nearly disappears.The mixture is now shaken thoroughly and the titration continued, the end-point being denoted by the disappearance of the violet colour from the chloroform. 2KI03= Na,S,03, and 7KI03= 2Na,S,O,. The author uses solutions of potassium iodate containing 5 to 10 grms. per litre. In pure solutions of thiosulphate or tetrathionate the extreme error of the method corresponds to t0-3 C.O.of the standard solution. No greater error is found when dithionates are simultaneously present, since they react with iodate very slowly. G. C. J. Estimation of Silicon in Iron, Ferrosilioon, ete. R. Namias. (L'I?zd. Chim. Min. e. Met., 1915,2,281-284 ; through J. SOC. Chem. Ind., 1915,34, 836.)-In the case of ferrosilicon, etc., containing 10 per cent.or more Si, 0.2 grm. of the finely powdered sample is fused with 3 grms. of sodium peroxide and 5 grms. of potassium carbonate, the mass is dissolved in water, treated with hydrochloric acid, evaporated to dryness in a porcelain crucible, and heated on an asbestos board directly over a flame for some time to decompose the ferric chloride.In this way the silica is obtained in a pulverulent condition, and can be readily washed free from iron and alkali salts. I t is transferred to a filter, washed alternately with boiling water and hydrochloric acid, then dried and weighed. I n the case of iron and steel, the best results are obtained by dissolving in hydrochloric acid and evaporating to dryness without the addition of an oxidising agent ; most of the silicion separates in the elementary form, but is converted into silica during the subsequent calcination.I n the case of whiteINORGANIC ANALYSIS 419 cast iron with a, high content of combined carbon, the silica, is frequently contami- nated with iron (present as iron silicate) which cannot be removed by washing; the silica must then be purified by fusion with alkali. In the rapid estimation of graphitic carbon in grey cast iron by treatment with hydrochloric acid, weighing the residue, which is regarded as a mixture of silica and carbon, and then oxidising the carbon by ignition, appreciable errors may arise, since the greater part of the silicon separates in the elementary form, and is weighed as such in the first weighing; errors due to this cause may be avoided by adding excem of potassium chlorate to the hydrochloric acid solution.Estimation of Sulphates in Water by Benzidine Hydrochloride. F. W. Bruckmiller. ( J , Ind. and Eng. Chew., 1915, 7,600-602.)-The method is reported on favourably. I t is shown that about 25 per cent. more benzidine must be present than is required to combine with all the sulphuric acid; with an excess of only 15 per cent., the results are seriously in error.To 250 C.C. of the water (less if the SO, content is greater than 250';: parts per million), 10 C.C. of a, 1 per cent. solution of hydroxylamine hydrochloride are added if ferric iron is present, and then 20 C.C. of benzidine hydrochloride solution (8 grms. benzidine per litre). The mixture is stirred, allowed to settle, filtered rapidly by means of suction, and the precipitate washed with 25 C.C. of water. Rapid filtration is best accomplished by filtering on a disc of filter-paper, placed in a Gooch crucible, and protected by a Witt plate. The precipitate is returned t~ the beaker, water is added, the mixture heated to boiling and titrated with & sodium hydroxide, using pleliolph- thalefn as indicator. Compared with results obtained on natural waters by a particular modification of the barium chloride method, the results of the benzidine method appear to be accurate within k 7 parts per million. No figures obtained from solutions of known sulphate content are given, except some on solutions of pure sodium sulphate, all of which are exact. G. C. J* * In the paper i t is stated that 20 C.C. of the benzidine reagent suflice for 250 C.C. of water, with 500 parts SO4 per million, but this is less than the theoretical amount ; whereas for water with only 250 parts per million it provides the margin of 25 per cent. recommended by the author.-Abstractor.

ISSN:0003-2654    

DOI:10.1039/AN9154000413

出版商:RSC    

年代:1915

数据来源: RSC

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INORGANIC ANALYSIS 419 APPARATUS, ETC. Apparatus for Continuous Extraction of a Liquid by Another and Heavier Liquid. J. Greenwald. (J. Ind. and Eng. Chent., 1915, 7, 621.)-The apparatus figured is constructed of glass. In use, some of the heavy liquid is poured into A. The liquid to be extracted is then added until the heavy solvent is forced up the tube C almost to its opening into B. The apparatus is then connected, in the usual manner, to a flask containing more of the solvent and to a condenser.Chloroform will extract all the caffeine from a 2-5 per cent. aqueous solution in three hours. G. C . J.420 ABSTRACI'S OF CHEMICAL PAPERS New Form of Pyknometer for Liquids. P. B. Davis and L. S. Pratt. ( J . Amer. Chem. SOC., 1915, 37, 1199-1200.)l -An improved form of Sprengel pykno- e F meter consists of a single closed tube of thin glass of the desired capacity, into the top of which are fused two capillary tubes.One of these, which is attached centrally, is bent a little above its point of emergence to an angle of 60°, and drawn out slightly at the end. This capillary is continued axially in- side the reservoir in the form of a tapered thin glass tube reaching alaost to the bottom, and having a bore at the lower end approximately equal to the capillary bore.The other capillary, attached slightly towards the side of the reservoir, is bent at a right angle, its bore in the vertical portion being swelled out into a small bulb sufficient to accommodate the expansion of the liquid over a rise in temperature of 10" C.A mark is etched on this capillary just below the taper of the bulb. The apparatus has the" appearance of a tubular wash-bottle. I n OJ adjusting the instrument when filled, a rubber tube is attached to the right-angled capillary, and the liquid blown gently out of the other until its level corresponds with the mark. The point is wiped with filter-paper, and, on removing the pressure, the liquid falls back in the inclined capillary, thereby reducing the danger of evaporation or accidental loss after adjustment.The advantages of this form of pyknometer are minimum weight, minimum length and projection of capillary arms, ease of cleaning and drying. J. F. B. Synthermal Regulator. A Device for Automatically Main- taining an Adiabatic Condition in Calorimetry.T. W. Richards and G. D. Osgood. ( J . Amer. Che.m. SOC., 1915, 37, 1718-1720.)- A differential hydrogen thermometer with a sensitive mercury contact is shown in the illustration. This apparatus, with the help of a relay, enables a stronger current to operate a heating or cooling mechanism for causing the temperature of one bath to follow that of another within 0.03O C. Two copper or silver cylinders, H, are cemented to a narrow glass U-tube, U ; suitable taps, A , 23, and C, are provided, so that the apparatus may be filled with hydrogen, and the platinumREPORT 421 wire E, containing 8 per cent. of iridium, is sealed into one of the bulbs of the U-tube so as to make contact with the mercury at the widening of the U-tube. The apparatus is extremely sensitive, and will make and break contact within O.Ol0 c. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9154000419

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

REPORT 421 REPORT. Royal Commission on Sewage Disposal. Ninth Report. Vol. 1, Report. Vol. 2, Evidence and Appendices. February 11, 1915. [Cd. 7,819 and 7,820.1 Part I. of the Report treats of the disposal of liquid wastes from manufacturing processes when unmixed with domestic sewage, and deals with the wastes mainly from the point of view of finding some standard to which they might conform after treatment.I t is divided into three sections, the first of which deals with wastes which pollute the stream into which they are turned owing to the suspended matter which they contain. These wastes arise from mining and quarrying operations. Coal, when brought up from the pit, is mixed with shale, clay, etc., and these matters are removed from the small coal by washing.The waste water may contain over 5 per cent. of solids in suspension, which by efficient settlement in tanks may be reduced to as little as 4 parts per 100,000, which figure is recommended as a standard, the settled water being fit to use over again. The (( tailing ” water from the crushing of tin, lead, and zinc ores contains over 2. per cent. of suspended solids, Experiments showed that the solids could be reduced by settlement to 6 parts per 100,000, with an effluent practically free from lead or arsenic, although there might.be, on occasion, zinc and copper in solution. Effluents from clay-settling pits and stone-quarry washers also might be reduced to the standard of 6 parts per 100,0001 for suspended solids. The second section deals with wastes which are polluting by reason of the dissolved impurities they contain 8s well as the suspended impurities. They com- prise effluents from the cotton, woollen, and paper industries. Soluble salts of a, poisonous nature may be present, also acids and alkalis, and colloid suspended niatter such as wool and vegetable fibres, grease, gum, and starch.Some of these wastes are particularly objectionable in a stream. At the same time, much of the suspended matter is very difficult to remove, and the Commission admits that efficient means of purification are not practicable nor available.For wastes from the dyeing and printing of cotton goods, precipitation with lime or alumina, followed by settlement or filtration, will usually reduce the suspended solids to 4 to 6 parts per 100,000; although there would still be much matter in solution which would absorb oxygen.In cotton bleaching, the kier liquors obtained in boil- ing the cloth to extract size and gum before bleaching are especially polluting, and the Commission made experiments on their biological purification. It was found if the caustic alkali was neutralised with carbon dioxide and the liquid either filtered through a matured sewage filter or digested with sewage sludge and then filtered, that much organic matter was removed and a more fully oxidised effluent produced.422 REPORT I t is recommended that the kier liquor should be kept separate from the rest of the waste and turned into the sewers.The wastes from the dyeing and scouring of wool are less polluting than those from cotton.They contain up to 500 parts per 100,000 of suspended solids, which can be removed very completely by means of precipitation with lime and alumina, followed by streaming filtration, and in some cases by settlement alone. The effluent should not contain more than 4 parts per 100,000 of solids in suspension. The wastes from paper mills are usually very dilute, but contain a good deal of organic matter in solution.Treatment in settling tanks, followed by percolating filters, has been tried, but the purification effected was much less than with sewage; therefore the Commission do not recommend any standard except for solids in suspension-namely, 4 parts per 100,000 for wood pulp mills and 6 parts for other mills. The third section includes wastes which are polluting mainly from the dissolved solids which they contain, and for which in some cases practicable methods of purification are not yet available.These wastes are very varied in origin, but may be dividied into two classes-those containing putrescible organic matter, and those containing injurious chemicals. The first class being polluting liquids in the same way that sewage is polluting, additional treatment to simple clarification should be required.Of these, wool scouring liquor, where it occurs alone, is one of the most polluting. I t consists of a soapy solution containing about 1 per cent. of fat in suspension and 0-3 per cent. of potash in solution. Some recovery of fat and potash has been made, birt tha processes have been considered too expensive.The usual method of treatment in use is to acidify the waste, run off the acid liquid into a sewer or stream, and press the fat in a hot press. Many laboratory experiments were made by the Commission upon the direct precipitation of the waste, and it was found that ferric chloride was the best precipitant, removing about 99 per cent. of the fat. A series of large scale experiments was then made at a mill accompanied by recovery of the fat, and the cost was worked out i n detail.'The Commission were satisfied that the process could be worked at a profit, but the 6rm at whose mill the experiment was made did not accept this conclusion. The Commission found that the liquid after precipitation was amenable to filtration through matured clinker, becoming non-putrescent.They recommend, therefore, &hat the standard for this waste should be a dissolved oxygen absorption not exceed- ing 4 parts per 100,000 in five days, in addition to a limit of 4 parts of solids in .suspension. It is pointed out that these effluents and the sludges may contain anthrax spores, and are therefore a possible danger to animals grazing on land to which they may be applied.Brewery waste contains spent yeast and hops in suspension, and much dissolved carbonaceous matter, which undergoes acid fermentation with subsequent putrefaction. It can be treated readily along with sewage unless it is in excessive amount, and it can be treated by biological methods when it is to be turned into a stream alone.Observations were made on treatment in a septic tank and percolating filters, and in triple contact beds, and in each case it was possible to produce a good effluent. The acid liquid is very polluting, and still contains much fat.REPORT 423 When applied to land, the development of acidity requires to be prevented by the addition of lime. The standard recommended is 4 parts suspended solids and 4 parts dissolved oxygen absorption in five days.The same standard is fixed for steep water from maltings, which can be treated in the same way. The treatment of distillery waste was described in the Sixth Report, and the standard now fixed is 3 parts suspended solids and 2 parts dissolved oxygen absorption. Fellmongers’ wadte and tanners’ waste are exceedingly polluting liquids, containing large amounts of nitrogenous organic matter, and having an offensive smell.Labora- tory experiments proved that the wastes were amenable to biological filtration, and it is recommended that this should always be done before turning the waste into a stream. The sludge produced is liable to contain arsenic and anthrax spores. I n sewered areas the waste may be turned into the sewer.The same standard as for brewery waste is fixed also for dairy waste, including creameries, cheese and condensed milk stations, and butter factories. These wastes contain 0.1 to 0.2 per cent. organic nitrogen, and have an acidity of 0.2 to 0.5 per cent. The waste, mixed with sewage, is readily purified by biological filtration, and i t has been treated on land, I n towns it may be received into the sewers without treatmont other than the removal of most of the grease.Margarine waste is similar, and the grease should always be removed before turning into a sewer. The second class of these wastes do not undergo putrefaction ; indeed they fre- quently delay its occurrence in the stream, and they are poisonous to fish and plants.The waste from the distillation of shale oil consists of acid and alkali wash waters and spent gas liquor. I t is treated by settlement and filtration through heaps of spent shale. The effluent is a good one, although it may contain nearly 1 part per 100,000 of zinc. The standard suggested is 4 parts suspended solids and 4 parts dissolved oxygen absorption in five days. Metal waste from galvanising and tin-plate works is an acid solution of sulphate or chloride of iron.I t should not be turned into a stream, but should be evaporated. The dilute washings, however, may be neutralised with lime or sodium carbonate, and, after settling the suspended solids to 6 parts per 100,000, may be turned into a stream. Many experiments were made on the purification of spent gas liquor, but the Commission are unable to recommend any method of treatment, except possibly percolation through spoil heaps at collieries ; and the only alternative is evaporation.A partial purification process has been successful, in which the liquor is diluted with previously treated liquor, and passed through biological percolating filters ; about 80 per cent. purification is produced, but the method is considered expensive.When the waste is produced in a town it may be admitted to the sewers, provided it does not exceed 2 per cent. of the volume of the sewage, as it has been proved that in this amount it does not interfere with tank and filter treatment. Another waste for which the Commission are unable to suggest any treatment is the sulphite cellulose liquor of the paper industry, and it is stated that this liquid should not be discharged into a stream.The standard fixed for both wastes is the same as for brewery waste.424 REPORT Finally, the Commissioners state that, although their labours are concluded, there is still need for investigation and research, and they again press for the formation of a Central Authority, which would not only control methods of treat- ment, but originate new and improved ones.Part 11. of the Report deals shortly with the disposal of liquid and solid domeshic refuse in rural areas. Where the water-supply is adequate, water carriage is the most satisfactory system, but where the supply is. inadequate, dry closets are open to little objection. The use of dry earth in these closets is of gre& importance, and the contents should be frequently removed by means of pails.Domestic waste water may be conveyed to a cesspool or distributed over a garden, and ample garden space should be provided. The Appendices to the Report contain full details of the Commissioners’ experiments on the. purification of brewery waste, wool-scouring waste, and cloth scouring and dyeing waste.There are also two reports comparing the manurial value of natural and de-greased sewage sludge. I t was found that the removal of grease did not increase the manurial value, and in some cases decreased it. Final Report, February 11, 1915 [Cd. 7,82I].-This is a general summary of previous reports, and no new conclusions nor recommerJdations are contained in it. The Commissioners recall that their inquiry has extended over sixteen years, and that nine reports have been issued, four dealing mainly with the purification of domestic sewage discharging into streams, two with the discharge of sewage into tidal waters, and three with the discharge of trade wastes. The Commissioners record that two of their recommendations have been adopted. Shell-fish ownera agreed to close sewage polluted layings, and, consequently, oysters are far safer articles of diet now than formerly. A plant was erected €or the purificstiori of distillery waste according to the Commissioners’ directions, and has proved itself capable of producing an effluent at a reasonable cost which is not injurious to fish. Other similar plants are being erected. J. H. J.

ISSN:0003-2654    

DOI:10.1039/AN9154000421

出版商:RSC    

年代:1915

数据来源: RSC