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OCTOBER 1906. Vol. XXXI. No. 367. THE ANALYST. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. THE METHOD OF ANALYSIS OF MILK USED IN THE GOVERNMENT LABORATORY FOR SAMPLES REFERRED UNDER THE SALE OF FOOD AND DRUGS ACTS. BY H. DROOP RICHMOND F.I.C. and E. H. MILLER. (Read at the Meeting July 14 1906.) INTRODUCTION. IT is remarkable that so few investigations into the validity of this method have been made and published. It appears to have been used for more than thirty years, and was first described by Dr. James Bell the then Principal of the Somerset House Laboratory in Part 11. of his ‘‘ Analysis and Adulteration of Foods ” (see ANALYST, viii. 141). The process may be considered as consisting of two parts the maceration method of estimating fat and solids-not-fat and a correction for loss of solids by fermentative change.The maceration method has during the thirty years of w e undergone no essential modification and except in minor points of detail is used to-day as described by Bell. The correction to be made has however undergone a, radical change. As described by Bell the correction took the form of a time al1owance and this was severely criticised notably by Stokes (ANALYST xii. 226) and Allen (ANALYST xii. 231 I‘ Commercial Organic Analysis,” p. 203) and undoubtedly this correction was liable to grave errors. I t has now been superseded by a process oE correcting for loss by the estimation of some of the more important products of decomposition (alcohol volatile acids and ammonia) ; the method was published in a report to the Local Government Board (see Report of the Milk Standards Committee Blue-Book Cd.484 1901 p. 404) and again by Thorpe (Transactions of the Chemical Society 1905 p. 206). The latter paper contains in addition to experimental proof that alcohol volatile acids (acetic and butyric) and ammonia are actually formed in sour milk a further correction for butyric acid should the amount of this be appreciable. The only investigation made into the maceration method outside the Government Laboratory of which we are aware was carried out by Bevan and Hehner in conjunc-tion with one of us and the results are summarized in the Blue-Book cited above (pp. 391 and 392); the directions followed were those of Bell which are not very explicit and the method was not carried out in precisely the manner employed at the Government Laboratory.It appeared to us desirable considering the importance o 318 THE ANALYST, the method in the administration of the Sale of Food and Drugs Acts to investigate its accuracy and with the concurrence and partly even at the request of Dr. Thorpe, we commenced the present research. By the kindness of Dr. Thorpe one of us was enabled to receive personal instruction in the method from Mr. C. Simmonds and we believe that our procedure differs in no essential particular from that employed in the Government Laboratory We took up the investigation with more interest as we were aware that the method had been subjected to much criticism based for the most part on no direct experimental data and it appeared desirable to see how far the criticisms were valid.The research divided itself into two main heads : 1. The maceration method itself which again could be subdivided into-( a ) The estimation of fat ; and (b) The estimation of solids-not-fat ; and 2. The allowances for decomposition. This portion of the investigation may be considered as-(a) The alcohol correction ; (b) The volatile acid correction; (c) The ammonia correction including other corrections for proteid (d) Corrections not dealt with in the Government Laboratory. Our general conclusions are that although we have found several sources of error both in the method and in the corrections they are comparatively trivial and hardly affect the validity of the process. On the other hand we have been enabled by the analysis of the decomposed milk to make a satisfactory estimate of the composition of the original milk laore especially if the modifications of the method and the corrections we propose are employed.At the same time we must confess that the method requires more personal attention than could easily be devoted to it by public analysts and for this reason we conceive that adventitious error is more likely to occur. I. THE MACEEATION METHOD. Estimation of Fat in Fwsh MiZk.-It has been shown by Thorpe (Zoc. cit.) and by Hehner Bevan and Richmond (Zoc. cit. and 4 6 Dairy Chemistry," p. 94) that the results of estimation of fat by the maceration method agree with those obtained by other methods which are admitted to give substantially accurate results and we have therefore devoted but little time to this.We have however incidentally obtained a few results which confirm the accuracy and have been favoured by Mr. Simmonds with a few others obtained on samples of homogenized milk. change; and The results are : NO. Pat by Maceration Method. Fat by other Methods. 1. 3.92 3*93* 3-94" 3.95 2. 344,* 3.42* 3-46 3. 3-81," 3*84* 3-87 4. 3.88 3.91 3-92 5. 3-90 3-83 3-85 6. 3.86 3-86 3.9 THE ANALYST. 319 Samples 1 2 and 3 were homogenized milk and the results marked * axe the work of Mr. Simmonds. The only remark that it is necessary to make is that when the milk before extraction of the fat is neutralized using phenolphthalein as indicator the ethereal solution contains the whole of the phenolphthalein which is weighed with the fat, and from which it can be separated if desired by taking advantage of its insolubility in petroleum ether.As however the amount of phenolphthalein added need not exceed a milligramme no appreciable error is caused by neglecting this. Estimation of Fat in Sowr MiZ?c.-In the Blue-Book cited a number of comparisons of fat in fresh milk and in the milk after it has been allowed to become sour are given, and it is there shown that the fat in the sour milk varies from 0.06 per cent. more to 0.15 per cent. less than in the fresh milk and averages 0.05 per cent. less. Thorpe (Zoc cit.) reproduces most of the results and adds a few more which show substantially the same agreement. We have examined nineteen samples of milk by this method and though our limits are slightly wider than those given above find that the results on eighteen of the samples of sour milk are in very fair agreement with those obtained when fresh by Gottlieb’s method.I n one sample however, which is queried in the table of pesults the “ fat ” in the sour milk is more than 0-5 per cent high; in this case the milk had undergone a most unusual decomposi-tion and we were able to prove that the ether extract was by no means all fat. The ethereal solution was quite opalescent and when the ether was evaporated and the residue taken up with petroleum ether a considerable residue was left (the weight of this was added to the solids-not-fat) and the petroleum ether was also opalescent. After washing the petroleum ether solution with slightly alkaline water it became clear but on evaporating and drying the ‘( fat ” was turbid and on again taking up with petroleum ether a flocculent residue was left ; a second flocculent residue was obtained on evaporating the clear solution.Owing to an accident the fat after these treatments could not be weighed but there is no doubt that the figure given (641 per cent.) is too high. We shall refer to this sample again; and the results obtained on it indicate that amino acids resulting from the hydrolysis of the proteids were con-tained in the ethereal solution. We are of opinion that some of the difference between the results obtained on the fresh milk and those on the sour milk is due to the diEculty of completely redis-tributing the fat in the curdled milk. Examination of an apparently well-mixed sample of sour milk with a low-power lens shows the presence of quite large particles of cream and no amount of whisking with a wire brush appears to reduce the milk to the same homogeneous condition easily obtained with fresh milk.We have had one sample from which the label had been apparently soaked off in warm water and another substituted in which it was impossible to obtain concordant results for fat. Eight determinations by the maceration Gottlieb and Werner-Schmid methods, gave the following figures 4.18 4.05 4-03 4-51 3.67 3.73 4.76 2.78. Many samples also on mixing yield a portion of their fat in a churned condition, which adheres to the wire brush ; we have in these cases made a separate estima-tion of the churned fat: We have been quite unable to extract the fat with eight treatments with ether 320 THE ANALYST.as prescribed in the description of the method and have found twenty to thirty treatments necessary. We have also been unsuccessful in obtaining a residue from which we can obtain no more fat. We have usually stopped extracting when six to eight successive treatments yield only a mgm. or two of fat. This may be due to the fact that we have worked in aluminium basins instead of the platinum vessels used at the Government Laboratory and that this metal is too soft to permit of very efficient grinding. Estimation of Solids-not-fat in Fresh Mdk.-We have made a number of com-parisons of the solids-not-fat by the maceration method with those obtained by the Saciety of Public Analysts’ method and find that invariably the former are higher than the latter.Twelve samples gave the following results : Maceration Method. 9.14 9.58 9.68 8.37 9.33 9.11 S. P. A. Method. 8.97 9.34 9.40 8.24 9.07 S.8g Maceration Nethod. 8.54 7.96 9.28 9-04 8.91 9.05 S. P. A. Method. 8.28 7-85 9.10 8-74 8.83 8-90 The average difference was 0.20 per cent. One of us has suggested (Blue-Book Cd. 484 p. 274) that the difference was due to the presence of milk-sugar in the hydrated form but this suggestion was combated by Thorpe (idem.) and denied by Lewin (Zoc. cit. p. 350). We have therefore made a number of experiments on this point, (a) Weighed quantities of milk-sugar were dissolved in water and evaporated to a firm paste; on treatment with ether this became at once solid and was finely powdered.After drying to constant weight the quantity left corresponded neither to the weight of hydrated sugar nor of anhydrous sugar but to an intermediate weight. Hydrated Sugar taken. 1. 0.5120 2. 0.6630 Residue Calculated for obtained. Anhydrous Sugar. 0.4955 0.4884 0.6470 0,6298 ( b ) We repeated Schmoger’s experiment (cf. Veitch ANALYST xi. 141). The solids-not-fat were estimated in 10 grams (circa) of milk by the maceration method ; in another portion of the same milk of almost identical weight a weighed quantity of milk-sugar was dissolved and the solids-not-fat estimated in this ; the difference between the two weights corresponded neither to the milk-sugar added nor to the anhydrous sugar calculated therefrom.Hydrated Sugar added. 1. 0*5000 2. 0.4245 3. 0.4349 Residue obtained. 0.4775 0.4232 0.4301 Calculated for Anhydrous Sugar. 0.4750 0.4033 0.4132 A similar experiment in which the total solids by the Society of Public Analysts’ method in a sample of milk was subtracted from the total solids of the same quantit THE ANALYST. 321 of milk to which a known weight of milk-sugar was added yielded an amount that differed from the weight calculated for anhydrous sugar by less than a mgm. (c) As we have found that when hydrated milk-sugar is stirred with water (1 gram to 10 c.c.) it produces a fall of temperature of 0.55" while anhydrous milk-sugar gives a rise of temperature of at least equal extent we endeavoured to use this as a means of investigating the question.With ordinary milks the change of tern-perature was slight but the solids-not-fat of milk obtained by repeatedly extracting and finely grinding the total solids obtained by the Society of Public Analysts' method with ether tended to give about 0.1" higher temperature than the solids-not-fat obtained by the maceration method. When the temperature change was exaggerated by using the solids of the milk to which milk-sugar had been added there was a marked difference. Samples 2 and 3 of solids-not-fat of milk to which milk-sugar had been added obtained by the maceration method caused a fall of temperature of 0*3" while the solids-not-fat obtained by extracting the solids by the Society of Public Analysts' method of the milk to which milk-sugar had been added gave a rise of 0.3".We think therefore that there is no doubt that the solids-not-fat obtained by the maceration method contain a portion of the sugar as hydrated sugar but the amount of water of hydration which we estimate averages about 0.1 per cent. is not sufficient to explain the difference between the results. Another source of error in the maceration method is due to the presence of aldehydes in the ether. It is well known that ether contains aldehyde and that when this is removed the ether after a short interval again contains aldehyde. We have found that ether free from aldehyde will give a marked Schiff reaction if shaken for a few minutes in daylight. We also find that milk solids remove the aldehyde completely from ether and this appears to be due to a condensation of the - COH group with the free amino groups of the proteids.The solids-not-fat obtained by the maceration method are always more acid than the milk and the aldehyde figure is less the increase of acid and the decrease in the aldehyde figure being within the limits of experimental error identical. These figures afford data for the estimation of the increase of weight due to the condensation of the aldehyde and assuming that it is acetaldehyde the error is almost constantly 0.03 per cent. unless freshly-distilled aldehyde-free ether be used. The solids-not-fat by the maceration method also give a faint Liebermann reaction pointing to the condensation of glyoxylic acid, but this cannot be large as if it were the increase of acid would be larger than the decrease of the aldehyde figure.Even this addition does not explain the whole of the difference between the maceration and Society of Public Analysts' methods and the marked browning of the residue in the latter method suggests that the remainder of the difference is due to the results obtained by it being too low ; this conclusion is strengthened by the fact that evaporation over a large surface whereby browning of the residue is avoided, gives slightly higher results. In sour milks the error of the maceration method due to water of hydration will be reduced as the amount of milk-sugar is less than in fresh milk ; but on the other hand a portion of the milk-sugar may be converted into hexoses which will have the same effect on the weight as hydration 322 THE ANALYST.The exact details of the method we have employed are these About 10 grams of milk are weighed into a basin of aluminium about 3 inches in diameter and a little over 1 inch high with a flat bottom provided with a flat-ended glass stirrer. Two drops of a 0.5 per cent. solution of phenolphthalein are added and approxi-mately TG strontia solution run in till a faint pink colour appears. The contents are evaporated to a damp paste on the water-bath when the basin is transferred to a hot plate and the paste mixed with the stirrer ; at a certain point in the evaporation the paste comes away from the basin and by careful manipulation both basin and stirrer can be obtained practically clean.On further evaporation and stirring the paste begins to get into a condition in which it can be broken up and rubbed into pieces, and at this stage it is removed from the hot plate and about 20c.c. of ether are added On gentle rubbing with the stirrer the solids begin to go to pieces ; the stirrer and basin are now scraped with a knife or spatula to bring any small portions of solids adhering to the sides under the ether and the solids are gently rubbed to a powder. The ether is decanted through a weighed filter 9 em. in diameter and the solids again treated with ether. The solids at this stage are in a condition in which they can be ground up to a fine powder ; the ethereal solution is allowed to settle and the ether decanted through the filter ; without any further addition of ether the solids are now ground to a very fine powder.We prefer to do this with only a very little ether in the basin as it is then easy to see the larger portions which can be ground up one by one. A further addition of ether is made and the solids further ground ; the ether at this stage looks like whitewash and the solids take some minutes to subside sufficiently to allow of decantation. After about six or eight treatments in this manner the solids are allowed to air-dry the portions clinging to the stirrer and sides of the basin scraped down and 5 C.C. of alcohol and a few drops of water are added ; the solids are well mixed with the alcohol and the basin is placed on the hot plate and evaporated till the paste begins to go to pieces when the solids are again treated as before.A second treatment with alcohol and a further six to eight extractions with ether are given ; the filter gradually becomes partially blocked with the finely-divided solids but never to such an extent that filtration stops. The solids are air-dried and then dried in the water-oven to constant weight. We have not usually weighed the solids-not-fat in a weighing-bottle ; although they are hygroscopic we have satisfied ourselves that no appreciable error is due to this cause. The final weight is known from previous weighings to within a very small amount and consequently the time of weighing is very short and we have proved that not more than a few tenths of a iogm. of hygroscopic moisture are taken up during the weighing. The top of the filter where fat collects is cut off and cut into pieces and thoroughly washed with ether; the knife or spatula is wiped on some of the pieces cut off to remove any particles of solids and the filter containing the pieces cut off is dried in the water-oven to constant weight.The ether is distilled and the residue of fat weighed; the fat is extracted with petroleum ether and the small residue insoluble in this solvent subtracted from the weight ; this usually consists of phenolphthalein and its weight may be neglected without appreciable error, The ether employed by us has been methylafed ether (specific gravity 0.720) dried with calcium chloride THE ANALYST. 323 11. THE ALLOWANCES FOR DECOMPOSITION. The AZcohoZ Correction.-We have usually taken about 75 grams for the estima-tion of alcohol.The quantity is weighed into a 300-C.C. flask and half neutralized with soda solution ; about half the volume is distilled and collected in a small flask, and neutralized with soda using litmus-paper as indicator. From this 25 C.C. is distilled and the density taken at 60" F. by a Sprengel tube. From the density the percentage of alcohol is calculated by the formula given in the Blue-Book and from this the correction is calculated. We believe that the alcohol correction is very near the truth. The Volatile Acid Correction.-We have in every sample estimated the volatile acids by the method given in the Blue Book but do not think that the results by this method at all represent the amount of volatile acid except when the quantity is very small.The method is in our opinion subject to several errors and is liable to be quite 50 per cent. from the truth. I n the first place carbonic acid is always present, and is driven off on evaporating the half-neutralized milk to dryness and as this is partially estimated using phenolphthalein as indicator as acetic acid an error is thereby produced. The error is a double one as not only is a correction made for carbon dioxide lost during the production of acetic acid but the carbonic acid itaelf is retained by the strontia and is weighed with the solids. The sum of these two errors we estimate as about 0.05 per cent. Against this we find that the whole of the volatile acids are not driven off on evaporation to dryness and the error due to this cause will partly compensate the error due to carbonic acid.There is another source of error due to a possible volatility of lactic acid and to the conversion of a portion of this acid into a lactone. Against this there is the formation of amino acids by hydrolysis of the proteids which would have a feeble acidity to phenol-phthalein. We aIways find that fresh milk on half neutralization and evaporation gives a very slight increase of acidity; and in one sample of sour milk we found that there was an increase of acidity on evaporating the half-neutralized milk and this result was confirmed on repetition. Probably when the volatile acidity lies between 0.1 and 0.2 as in the majority of our samples the method gives approximately correct results; in other cases it is quite erroneoug.The following experiments will show this : 0.0162 gram acetic acid added to milk 0.0162 gram acetic acid + 0.07 gram lactic acid 0.0125 gram acetic acid + O.Oi14 gram lact'i" acid added to milk+ the solution saturated with carbonic acid (contained 0.0031 gram CO,) , 0,0192 ,, I n the presence of much volatile acid we have added to the milk from which the alcohol had been distilled a quantity of acid exactly equal to the soda used for half neutralizing and have distilled this down to a small bulk and then added water in successive quantities of about 25 c.c. and distilled this off till the distillate was practically neutral. Thorpe (Zoc. cit.) has given practically this method but apparently _ found 0.0084 gram. 9 2 9 7 1 7 7 J 9 9 ., 0.0092 ,, added to milk . . , 0.0165 ,, $ 9 . . . . . 324 THE ANALYST. has not added any acid ; as he directs that the volatile acids may be estimated in the distillate by any convenient method we employed that of Duclaux which appears to us not only to be capable of considerable accuracy but which enables us to estimate the relative proportions of even three acids in a mixture and to indicate if the modification we have devised be employed what the acids present are. We have found it essential to add sufficient acid to neutralize the soda added as in some cases the volatile acid exceeds half the total acidity. Our mode of working is this The mixed distillates neutralized to phenol-phthalein are made up to 250 c.c. and an aliquot portion taken for fractional distillation; to this is added a quantity of N sulphuric acid slightly greater than is necessary to neutralize the soda used.Eight successive fractions each about one-ninth of the total volume are distilled and separately titrated with & strontia; 25 C.C. of water is added to the residue and a further 25 C.C. distilled and titrated, and if desired this treatment may be repeated. From the last titration the total quantity of volatile acid is obtained by extrapolation of the results ; the total quantity is always slightly less than the total acidity of the first distillate due no doubt to the presence of a little lactic acid As much as possible of the first distillate is made up to a convenient bulk after adding a quantity of N sulphuric acid in slight excess of that required to neutralize the soda and exactly one-third is distilled ; this is made up to a convenient bulk and exactly one-third is again distilled.The last distillate is made up to 100 c.c. and eight fractions of about 11 C.C. each are distilled and separately titrated. The residue in the flask and condenser is washed out and titrated to obtain the total quantity. For the calculation of the results we have slightly modified the formulae given by one of us (ANALYST xx. 193) to : y = x2.1 for butyric acid ; y = ~ 1 ' 1 s for propionic acid ; and y = xj for acetic acid. y = quantity of acid left in retort ; total quantity = 1. x = volume of liquid left in retort ; total quantity = 1. For each fraction me calculate the proportion of each of the acids which would distil and calculate the ratios of butyric to acetic and butyric to propionic acid, which correspond to the proportion actually distilled The ratios from first and last fractions are liable to be slightly erroneous the first because a small amount of a very volatile acid as carbonic would appear in this fraction and the last because experimental error is greatly magnified ; but we usually find that the other six ratios are practically constant for either butyric and acetic acids or butyric and propionic acids.The distillation of the third of a third is undertaken in order to decide definitely the composition of the mixture. From the formuh above, the proportions which would distil when one-third of one-third is collected are : For butyric acid .. . . 0.3285 For propionic acid . . . 0.1445 For acetic acid . . . 0.06 THE ANALYST. 325 Distilled. I Distilled. ~ ~ - -Thus a mixture of butyric and propionic acids in equal proportions should yield approximately a 2 1 mixture in the distillate while a mixture of butyric and acetic in equal proportions would yield a 5 1 mixture. I t is even possible to deduce the relative proportions of a mixture of the three acids. I n the first we have concluded fhat the acids present were acetic and butyric ; in the second propionic and butyric; and in the third a mixture of the three. We give below the results of three experiments. -No. AC ACETIC AND BUTYRIC ACIDS. 0.48 1 ~ I Distillation of Original Distillate. ! ! 0.891 Distillation of 8 of &.-__-~ __ 1 Calculated for-0.206 --0.1215 I ' Calculated for- ~ Ratio. / I Ratio. ~ Volume 1 Distilled. _ - Acid Distilled. -0.190 0.343 0.490 0.619 0.726 o a 9 0.892 0-950 Butyric 1' Total. 1 I I -c__-0.108 0.141 ' 0.213 0.221 0-2275 I 0.406 0.335 I 0.403 1 0.5755 0.440 ' 0.515 ~ 0.708 0.559 ~ 0.6175 ~ 0.821 0-669 0.711 0.902 0.779 0.793 0.958 0.887 ~ ' 0.8705 0.9915 Butyric. 0.2225 0.397 0-566 0.701 0.8105 0.898 0.956 0.9905 -Acetic. Butyric Total. 0.78 0.78 0.77 0.785 0.79 0.795 0.805 0.805 -Acetic. -0.073 0.153 0.238 0.324 0.421 0.521 0.6345 0.780 0.077 0.148 0.2325 0,318 0,410 0.512 0.628 0.782 The quantity distilled in Q of & was 0.193.The figure calculated for a mixture of 0.495 molecules of butyric to 0.505 mole-The ratio of butyric acid in the second distillate should be 0.83. cules of acetic was 0.192. NO. 2.-PROPIONIC AND BUTYRIC ACIDS. Uistillatwn of Original Distillate. Distillation of ;5 of 6. -. _- - . Volume Distilled. -0.110 0.223 0-333 0.448 0.554 0.664 0.775 0.889 -~~ -Acid Distilled. Calcalated for- Calcdated for- Ratio. Butyric Total. 0-56 0.53 0.505 0.53 0.52 0-51 0.49 0.48 --Ratio. Butyric Total. Acid Distilled I Volume Distilled. 7-0.104 0.215 0.331 0.444 0.558 0*656 0.767 0.875 Butyric. Propionic, 0.1685 0.328 0.478 0.609 0.723 0.807 0.886 0,949 0.183 0-357 0.509 0.641 0.750 0.839 0.911 0.964 0.217 0.411 0.573 0.713 0-8165 0.899 0.9565 0.990 0.128 0.258 0.3 80 0.504 0.614 0.724 0.828 1 0.925 0.62 0.65 0.67 0.66 0.67 0.66 0.65 0.6 326 THE ANALYST+ Propionic.The quantity distilled in Q of Q was 0.242. The figure calculated for a mixture of 0.514 molecules of butyric to 0.486 mole-The ratio of butyric acid in the second distillate should be 0.70. cules of propionic was 0.239. Acetic. NO. &-ACETIC PPROPIONIC AND BUTYRIC ACIDS. Distillation of Original Distillate. I I Calculated for- Ratio. Volume Distilled. I Acid 1 Distilled. I--0.169 0.324 0.467 0.588 0.705 0.8105 0.897 0.950 Butyric B + Ac. ___~ Butj-ric + P-0.545 0.51 0.50 0.49 0.48 0.4 6 0.44 0.33 Butyric B + 2P TA.Rutyric. _____ 0.208 0.397 0-563 0-695 0.8105 0.89 7 0.955 0.99 1 Proprionic. ~ 0,1225 0.2475 0.372 0.487 0.607 0.721 0.825 0.930 Acetic. 0.071 0.148 0.231 0-314 0.410 0-514 0-627 0,7775 0.715 0.71 0.71 0.72 0.735 0.75 0.78 0.81 0.62 0.60 0.60 0.60 0.62 0.61 0.63 0.63 0.105 0.214 0.326 0.432 0.547 0.661 0.772 0.895 I t is seen that bhe ratios calculated on the supposition that the acids consist of acetic and butyric and propionic and butyric neither of them give constant figures, but when calculated for a mixture of 2 molecules propionic and 1 acetic the agree-ment is satisfactory. On this assumption the total quantity distilled in & of + should be 0.248 of the total.We actually found 0.251 and the ratio of propionic to acetic in the last distillate should be 5 to 1. Distillation of + of Q. __-Acid Distilled 0.190 0.360 0.521 0.652 0.761 0.850 0.921 0-969 Calculated for-~ Ratio. Volume Distilled. Hutyric K + Ac. Butyric n-t r. Bn tyric B+5P+A. Butyric. 0.210 0.4015 0 573 0.707 0.8165 09025 0.959 0.991 0.124 0.2505 0.380 0 *501 0.614 0-730 0.8335 0.929 0.106 0,217 0.333 0-445 0.554 0 667 0.781 0.894 0.85 0.835 0.84 0.83 0.86 0.86 0.88 0.90 0.77 0.725 0.73 0.73 0.725 0.695 0.70 0.64 0.072 0.1505 0.247 0.325 0-416 0.5225 0.637 0.776 0.79 0.75 0-76 0.765 0.765 0-76 0.76 0.74 The ratio of butyric acid in the second distillate should be 0.78.I t is noticed in every case that the ratio of butyric acid in the distillate of 8 of THE ANALYST. 327 is slightly less than that calculated and this is partly due to the fact that there is always a slight loss during the two distillations and as butyric acid is the most volatile of the compounds present the loss will be proportionately larger of this acid than of the others, We think that we may claim that the above figures show that a fairly accurate estimation of and a determination of the nature of the acids present is possible by Duclaux’s method as modified. We append a table showing the total volatile acids expressed as C.C. of N alkali per 100 grams of milk estimated by the method described in the Blue Book and Duclaux’s methods respectively in five samples which have been high in volatile acids : NO.7. 9. 11. 13. 15. Blue Book Method. 7-35 5.7 7.68 14.0 12.35 Duclaux’s Method. 12.6 12.2 21.6 20.7 9.75 Ratio. 1.71 1.71 1.59 1-54 1-68 As to the corrections to be made for volatile acids there is some doubt. When the amount has been small we have assumed them to be acetic acid alone and have applied the correction given in the Blue Book-Le. an addition of 25.5 parts for each 60 parts of acetic acid. This correction we prefer to that given by Thorpe-Le., 62 parts for each 60 parts of acetic acid-as the latter correction assumes that acetic acid was produced by oxidation and the oxygen was part of the original milk.For butyric acid Thorpe gives a correction of 92 parts for each 88 parts of butyric acid but this correction assumes that the weight of lactic acid from which it was supposedly formed was equal to the weight of the milk-sugar giving rise to it. This is the case if the milk-sugar is supposed to exist in the solids as hydrated sugar but we have shown that this is only partially the case and prefer to calculate the loss to anhydrous sugar and modify the correction to 87.5 parts for each 88 parts of butyric acid. We are however by no means satisfied that this correction is justified; it assumes that the butyric acid is derived from lactic acid. It is well known that the organisms producing lactic acid do not form more than about 1 per cent.of lactic acid as their action is inhibited by this amount of acid. In some of our samples the total acidity has been equal to nearly 3 per cent. of lactic acid and as the greater portion of this has been butyric acid it follows that it cannot have been derived from lactic acid. We assume that in every case of fermentation the milk-sugar is hydrolysed to glucose and galactose and we therefore take a hexose as our starting-point. To explain the formation of butyric and propionic acids we assume the following reaction to take place : 3C,H,,O = 2CH,CH2CH2COOH + 2CH,CH2COOH + 4C0 + H2 + 20H2 328 THE ANALYST, which gives a total loss of 94.5 for 88 parts of butyric and 74 parts of propionic acids. This is the proportion in which we have found these acids and we have therefore used this correction.For butyric and acetic acids there are so many equations which can be drawn out to explain their formation each of which gives a different correction that we have not attempted to do this but have used the corrections given above. That they are not quite correct is shown by the agreement of these samples not being quite 80 good as the others. The Ammonia Correction.-We are very doubtful as to the validity of this correction. Though during the hydrolysis of the proteid a portion of the carbon and hydrogen may be converted into volatile non-acid compounds we do not think that the whole of the nitrogen is converted into ammonia with total loss of the other constituents. We are also doubtful whether the colour produced by Nessler solution is all due to ammonia as it is sometimes so markedly different in tint from that produced by the standard solution of ammonium chloride.As the whole correction is usually small we have accepted it as we have found that there are changes in the proteids on evaporation of the milk which no doubt involve a slight loss. We have in many samples estimated the aldehyde figure (cf. Steinegger, ANALYST xxxi. 46 and ourselves ANALYST xxxi. 224) both in the sour milk and in the solution of the solids obtained by evaporating the half-neutralized milk. The table below gives our results : NO. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. These Aldehyde Figure in Fresh Milk. 19.4' 19.4' 19-4" 19.4' 19.4' 19.5' 19.4" 19.4' 19.4" 19.6' 19.4' 14.4' 19.4' 14.5' Aldehyde Figure in Sour Milk.24.0' 24*1° 24.1' 21.3' 27.6" 29.8" 87.5" 35.6" 32.0" 22.7' 26.7' 23.1' 32-9O 27.1' Aldehyde Figure after Evaporation. 17.5' 15.5" 16.9' 15.1' 16.3' 13 -9' 19.4' 14.9' 16.3" 16-7" 15.7' 10.9O 18.2" 11.8' FJ H,, Correction. 0.01 0.02 --0.02 0.06 0.01 0.09 0.07 0.01 0.02 0.03 0.12 0.10 Eigures show that in all the samples of sour milk hydrolysis has taken place with the formation of amino acids but that on evaporating these amino acids condense either to form di-keto-piperazine derivatives or polypeptids ; the hydrolysis would cause an increase in weight but the condensation a loss and as the figure is always lower after evaporation than in the fresh milk this indicates that a slight additive correction should be made.I t is noticed that when there is much ammonia developed there is also a high aldehyde figure THE ANALYST. 329 We have examined one sample (No. 5) which is not included in the above list, which gave an aldehyde figure after evaporation of over 300O; on evaporation it smelt like glue and became a plastic mass. This is the sample referred to as yielding too high an ether extract. The distillate which should have contained only alcohol was found to be strongly alkaline with ammonia or an amine and the acidity was higher than it could have been had all the milk-sugar originally present been converted into lactic acid.The solids-not-fat were higher in the sour milk than in the fresh milk, and the system of corrections adopted at the Government Laboratory entirely failed to give correct results. This sample had undergone a most unusual form of decom-position but as it was not originally a normal milk we do not consider that it invalidates the system. As the unusual decomposition which was not realized till the sample had been used up prevented an accurate analysis being made we cannot speak very definitely but there are distinct indications that the further corrections which we propose would have given good results even with this sample. Corrections not dealt with in the Government Laboratory.-These corrections are three in number; the first is for the lactic acid produced. The usual equation for this is-which indicates that 342 parts of milk-sugar produce 360 parts of lactic acid.We have therefore subtracted 5 per cent. of the lactic acid from the weight of the solids-not-fat. We calculate the total acidity less the volatile acidity plus 0-2 per cent. (to represent the acidity of the milk when fresh) as lactic acid. The second correction is for the aldehyde taken up from the ether used. We find that the solids-not-fat which should of course be neutral are always acid after extraction with ether and the aldehyde figure has gone down. That this is due to condensation of aldehyde is shown by the substantial agreement of the increase of acidity with the decrease in the aldehyde figure. As the aldehyde figure is affected by the combined error of four titrations the agreement is good.C,,H,,O, + OH = 4CH,CHOHCOOH, No. 6. 8. 10. 12. 14. 16. 17. 18. 19. Increase of Acidity. 7 * 4 O 10.5' '7.6" 8-2" 4.3" 9.9" 8.2" 5.6" 5.6" 5.8" Decrease of Aldehyde Figure. 7*4O 9*1° 9.8" 6-7" 5.1" 10.0" 8.0" 5.5" 4.7" 5.5" All figures are expressed as C.C. of TG alkali per 100 grams. Assuming that the following equation takes place : NH,H coo R \ + CH,CHO = R :{:!. cH3 + OH,, it is seen that each 1" will correspond to an increase of 0-0026 per cent. of weight, When the sour milk contains a large amount of butyric acid the increase o 330 THE ANALYST. acidity does not agree with the decrease of the aldehyde figure. I n these samples an odour of butyric acid is noticed on extracting and drying and the solids-not-fat are either neutral or alkaline.I n thiscase we calculate what the increase of acidity should be from the aldehyde figure and take the difference between this figure and the figure actually found to represent loss of butyric acid by multiplying each degree by 0.0088. I n cases where the aldehyde figure of the evaporated milk is higher than 20" we should make a correction to be subtracted from the solids-not-fat for the weight of water taken up on hydrolysis. The equation of this change is : R - GO - NH - R1+ OH = R - COOH + NHZR', and each degree of aldehyde figure above 20" would represent a gain of 0.0018 per cent. of water. The abnormal sample previously referred to is the only one we have examined which would be subjected to this correction.~ i s c u s s i o ~ of Results.-In the table on p. 331 we give the analytical figures for nineteen samples of milk which were examined when fresh by the Society of Public Analysts' method and when sour by the method used in the Government Laboratory. Taking the whole of the samples it is seen that the fat estimated by the macera-tion method in the sour milk varies from 0.10 above to 0.18 below the fat estimated by the Society of Public Analysts' method in the fresh milk and averages 0.03 per cent. less. The solids-not-fat of the whole of the samples vary when corrected by the methods used in the Government Laboratory from 0.28 above the solids-not-fat in the fresh milk determined by the Society of Public Analysts' method to 0.27 per cent.below ; while if the corrections that we propose are used in addition the variation is from 0.32 above to 0.20 below ; the differences average +0*08 per cent. and +0.06 per cent. respectively. For milks that have undergone the normal decomposition-b. in which chiefly lactic acid is produced-the figures are : Maximum. Minimum. Average. Government Laboratory . . . . 0.28 - 0.11 + 0.14 R. and M. . . . . 0.17 - 0.19 + 0.07 Even when there is a marked alcoholic fermentation or a strong butyric fermen-tation the agreement is still fair and does not exceed the limit laid down by Thorpe (0.3 per cent.) (Zoc. cit.) as being sufficiently satisfactory. We have included two samples which contained about 25 per cent. of added water and here the agreement is satisfactory.These samples were made up by mixing known weights of the milk immediately preceding them in the table and of water and the amount of water calculated from the analysis of the sour milk after correction corresponded to within a few tenths of 1 per cent with that actually added. As showing what different fermentations milk may undergo we may mention that Nos. 8 and 9 and Nos. 10 and 13 were each taken from the same bulk of milk, though at slightly different times yet the character of the decomposition varied widely. It is of interest to mention that in the two samples in which butyric fermenta-tion had taken place and which give results for solids-not-fat on correction rathe THE ANALYST. 331 I 332 THE ANALYST. higher than the original the ratio of butyric to acetic acid was 1 1 while in those which are low the ratio was 3 1.This may be a coincidence and it is evident that many more samples must be examined before the proper corrections can be established. We have also examined some solutions of milk-sugar to which a small quantity of sour milk was added to supply the organisms necessary for fermentative change. The milk-sugar solution used contained 4.77 per cent. total solids calculated from the amounts of milk-sugar and milk taken and calculating the sugar as anhydrous sugar and 4-74 per cent. by evaporation to dryness and drying to constant weight. The following are the analytical figures : Volatile Acid Total Acidity Correction. Correction. as Lactic Acid. Alcohol Age. Total Solids.12 days . 4.56 0.35 0.03 0.20 37 days . 4.84 0.20 0.03 0.20 70 days . 4.70 0-15 0.04 0.29 85 days . 4.17 0.78 0.09 0-51 It is evident that the samples had undergone but little change; the volatile acid, which was found to be almost wholly carbonic acid accounted for about half the total acidity. It is seen that even making a minus correction for the carbonic acid the results are still too high and these experiments afford further proof that in the maceration method a portion of the milk-sugar is weighed as hydrated sugar. In conclusion we think we may claim to have shown that-1. The maceration method for fresh milks gives results slightly too high for solids-not-fat and about to the same extent that the Society of Public Analysts' method is low. 2. By the method used in the Government laboratory a satisfactory determina-tion of the composition of the orginal milk can be made the results except in cases of high butyric fermentation and other abnormal decompositions not being more than 0-2 per cent.from the truth. 3. The method for the estimation of volatile acids used at the Government Laboratory is not a good one and requires modification if any appreciable amount of these acids be present. 4. Certain small additional corrections may be made with advantage, Considering that in the course of an examination of nineteen samples of milk we have found at least two forms of decomposition (a proteolytic and a butyric-propionic fermentation) which require special corrections it is evident that many more experiments should be made before the analysis of sour milk can be considered t o be on a satisfactory basis.We would emphasize the fact that our comparatively large proportion of samples showing the butyric fermentation is partly due to a selection of these samples in preference to others and partly to the special precautions taken to prevent the bottles from bursting. With the normal conditions under which reference samples are kept, we doubt whether more than one of -the five would have survived to reach the Government Laboratory THE ANALYST 333 Firially we would express our thanks to Dr. Thorpe and Mr. Simmonds of the Government Laboratory for the kind way in which they have assisted us in this investigation. DISCUSSION. The PRESIDENT (Mr. Bevan) in inviting discussion said that his own experience was that the fat determinations made in the Government Laboratory in samples of sour milk were generally lower than those obtained by the public analyst on the fresh milk.Mr. Richmond some seven or eight years ago had considered the maceration process to be unsatisfactory in the case of sour milk but had now apparently changed his view. I n ‘‘ Commercial Organic Analysis,” Mr. Allen had said in referring to the Government method ‘‘ Some points strongly invite criticism, but the method must be welcomed as an ingenious attempt to effect a satisfactory solution of a very difficult problem.” And it seemed now to be generally agreed that the method was an ingenious and fairly satisfactory one. MR. F. J. LLOYD said that he had done a good deal of work on the examination of sour milk and should be interested to see what light these improved methods would throw on the changes which took place in such samples.Those changes it might be mentioned were never constant. He had found that in genuine milk changes occurred which depended entirely on the nature of t6e bacteria present ; and when a sample was adulterated with water other changes were brought about by the organisms peculiar to water. E e had studied the action of various micro-organisms on sterilized milk and had found that while it was fairly easy to obtain accurate results with samples which had only been acted on by the lactic acid bacillus it was very difficult when gas-producing organisms (such as BaciZZz~s coZi cowmunis) were present in large quantities to obtain all the products of the decomposition and calculate the composition of the original milk.In the majority of cases he had found that the loss was proportional to the amount of acid produced being almost always half the total acidity calculated as lactic acid. The supposition that what took place in the conversion of milk-sugar into lactic acid was merely an addition of the elements of water to the milk-sugar and a splitting up into exactly four parts of acid was incorrect. As a matter of fact only about 60 per cent. of the milk-sugar was actually converted into lactic acid other compounds being formed from the remainder. Mr. FAIRLEY said that he could endorse what Mr. Lloyd had said as to the varying effects produced in milk by different bacteria.Possibly some of the abnormal results stated in the paper might be thus explained. Mr. RICHMOND said that it was quite true that his opinions had changed as to the extent to which the fat could be obtained from eour milk by the maceration process. During the past few years he had learned a good deal more about the process and had come to the conclusion that formerly he had not applied it in the best way. I t was iiiiportant to dry the milk to the right extent and to grind it thoroughly. He quite agreed with Mr. Lloyd as to the difficulty caused by gas-producing organisms. Nevertheless he thought that even in that case by determining a sufficient number They had found about a day and a half’s hard grinding necessary 334 THE ANALYST, of compounds the composition of the original milk might be fairly accurately deduced.From the figures they had given it would be seen that their experience was quite at variance with Rlr. Lloyd’s as to the total loss being equal to half the quantity of lactic acid. He thought that merely to correct for lactic acid would by no means be sufficient. With regard to the conversion of milk-sugar into lactic acid it was of course the case that even in stimples that had undergone what they had called normal decomposition small quantities of volatile acids and alcohol were always produced and therefore the very simple formula referred to would not strictly speaking represent what took place. Nevertheless for purposes of correction when each of the other substances was duly taken into account it did not involve a serious error to apply the correction in the simplest way by assuming that the residue of the lactic acid was derived from milk-sugar according to the formula.Dr. VOELCKER suggested that if the authors of this paper and also Mr. Lloyd, continued their observations it would be advantageous to pay attention more particularly not to normal samples which gave the public analyst no difficulty, but to samples which were mixed or believed to be mixed with smaller or larger quantities of water. Mr. ESTCOURT said that according to the experiment at the Government Laboratory the loss of solids-not-fat which occurred on keeping a milk was mainly due to the formation of alcohol. Indeed the alcohol formed was said to represent seven-tenths of the total loss by keeping.The figures given by the authors of the paper do not bear out this theory. How does Mr. Richmond account for this? Mr. RICHMOND said that the statement that the alcohol correction amounted to seven-tenths of the total correction was to be found in the Appendix to the Report of the Departmental Committee. They did not endorse it; it was not generally correct. Mr. LLOYD remarked that he had never found anything like 2 per cent. of acid, and only once over 18 per cent. even in samples that had been kept for months. The PRESIDENT said that in some samples which he had analysed some years ago he had found 13 per cent. of total acidity including GO,. Mr. RICHMOND said that in one of their samples as would be seen the total acidity was 22 per cent. and in two others it was even a little more. That of course was the total acidity from all sources calculated as lactic acid. The quantity of volatile acids in those three cases was considerable and there was very little actual lactic acid. If all the acidity were due to lactic acid he quite agreed with Mr. Lloyd that it would not be likely to reach 18 per cent. It was only when some unusual form of decomposition had occurred in the course of which large quantities of other acids were produced that these high acidities were found. NOTE BY DR. THoRPE.-Mr. Droop Richmond has courteously afforded me the opportunity of perusing the foregoing paper and of appending any comments that it might seem desirable to make. Anything like detailed criticism however would here be out of place; and beyond congratulating the authors upon having dealt in an instructive way with an interesting matter I think I need only remark that the principal matter on which Messrs. Richmond and Miller’s procedure differs fro THE ANALYST. 335 that of the Government Laboratory is the method of dealing with the volatile acids. In actual practice however we find the cases extremely rare in which the volatile acids exceed 0.2 per cent. so that the extended process described in the paper would scarcely ever be applied. On the whole it appears that although there are certain points open to discus-sion the conclusion of Messrs. Richmond and Miller is that in general a substantially accurate determination of the original solids of the milk can be made by the method in use at the Government Laboratory. That in certain cases a somewhat closer approximation can be obtained by elaborated processes is no doubt true and the authors are to be congratulated upon their careful investigation of the question

ISSN:0003-2654    

DOI:10.1039/AN9063100317

出版商:RSC    

年代:1906

数据来源: RSC

摘要:

THE ANALYST. Chita - Chosi - Hakodatk - 335 0.9347 1.32 0.66 195.76 180.7 1.4808 35.4 0.9318 8-22 4.13 196.16 180.57 1.4802 36.2 0.9316 5.15 2-59 194.81 187.27 1.4807 35.8 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. C. D. Holley. (Journ.. Amer. Chem. SOL, 1906, xxviii. , 993-997.)-The amount of sulphite recovered from meat by distillation with phosphoric acid is found to be approximately one-fourth that originally present. Of forty-three samples of pork-sausage and Hamburg steak examined, thirty contained sulphite, the quantity actually recovered varying from 0.023 to 0.361 per cent. sodium sulphite. The amount of sulphite in fried meat is almost as great as in the uncooked state. Dried prunes, peaches, and apricots yielded considerable quantities of free or combined sulphurous acid, one sample of prunes containing as much as 0.226 per > Sodium Sulphite in Food, cent, calculated as sodium sulphite.w. 13. s. A New Unsaturated Fatty Acid in Japanese Sardine Oil. M. Tsujimota (Journ. C'oZZ. Engiizeering, University of Tokio, 1906, iv., 1-9.)-It is stated that the Japanese sardine oil of commerce is liable to contain more or less of other fish oils, but the author has analysed three specimens which were undoubtedly derived from CZzLpanodoTz melaizostictu. They were greenish-brown to reddish-brown in colour, had a fishy odour and taste, and on standing at low temperature yielded large deposits of '' stearin." Apparently they were free from any considerable amount of unsaponi- fiable matter. The following analytical values were obtained : I I I I I I I336 THE ANALYST, The mixed fatty acids of the three oils on treatment in ethereal solution with an excess of bromine yielded 47.09, 44.24, and 44.88 per cent.respectively of white insoluble products, which turned black at 200" C. and decomposed before their melting-point was reached. They were found to contain from 69-95 to 70.16 per cent. of bromine, and the other results of an elementary analysis also showed that they were octobromides with the formula CI8Ha8Br8Oa, evidently derived from an un- saturated acid, C,,H,,O,, belonging to the series C,,H,,,-,O,. The author terms this new acid chpanodonic acid, and calculates that it forms from 13-34 to 14.20 per cent. of the mixed fatty acids from Japanese sardine oil. By reducing it with zinc dust and alcoholic hydrochloric acid he isolated about 25.7 per cent. of the theoretical quantity of the free fatty acid, which was a yellow liquid with a fishy odour, which became oxidized on exposure to the air, and formed a dry varnish in a few days. I t had an iodine value of 344.42, as compared with the theoretical value 367.73, Since no hexabromide insoluble in ether was found, the conclusion is arrived at that the presence of jecoric acid in Japanese sardine oil is doubtful. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9063100335

出版商:RSC    

年代:1906

数据来源: RSC

摘要:

336 THE ANALYST, ORGANIC ANALYSIS. Rose-Herzfeld and Sulphuric Acid Methods for Determination of Higher Alcohols. V. H. Veley. (Joz~rn. Sot. Chm. Ind. 1906 xxv. pp. 398-401.)-From a full examination of the two methods working with several of the higher alcohols, the Quthor concludes that by adopting all necessary precautions as to determination of specific gravity of the spirit calibration of the apparatus keeping the chloroform sheltered from the light etc. the R6se-Herzfeld method is sufficiently accurate for all commercial and legal purposes. The removal of aldehydes from the distillate from brandy or other spirit by heating for one hour with caustic soda under a reflu THE ANALYST. 337 condenser is considered more satisfactory than the sulphuric acid process and subse-quent destruction of the aldehydes by means of m-phenylene-diamine or preferably aniline phosphate.The line of demarcation between the chloroform and aqueous layer is more distinct if after shaking the chloroform is allowed to drop very slowly from the upper to the lower bulb and Griinheit's observation is confirmed that after the manipulation has been completed the chloroform slowly contracts sometimes requiring an hour before a constant level is reached. Though less accurate the su1phuri.c acid process gives valuable information. The risk of loss of higher alcohol before it is attacked by the sulphuric acid during the heating of the mixture in equal volumes of the sulphuric acid and alcohol solution may be obviated by using glass-stoppered bottles of about 50 C.C.capacity the stoppers of which are tightly tied down during the heating operation. A bath of saturated NH,C1 is suitable for this purpose a constant temperature of 109' to 110" C. being thereby readily maintained. The colour produced varies considerably with the temperature a difference of 2' or 3" causing a marked difference in the tint. It is better to cleanse the bottles prior to use with sulphuric acid only not using nitric acid also as the latter is SL source of danger. From the author's experience it seems probable that no reaction would take place if the higher alcohols and acid were both pure and the containing vessel quite clean. Unification of Reduction Methods of Sugar Analysis. L. S. Munson and P. H. Walker. (Journ. Amer. Chewz. Soc. 1906 xxviii.pp. 663-686.)-The use of one standard set of solutions is proposed for all reducing sugar determinations the precipitated cuprous oxide being weighed. The solutions recommended are one containing 34-639 grams of crystallized CuSO, which must not contain more than a trace of iron per 500 c.c. and the other containing 173 grams of Rochelle salt and 50 grams of sodium hydroxide per 500 C.C. For a determination 25 C.C. of each solution are placed in a 400 C.C. beaker and 50 C.C. of reducing sugar solution added or if less sugar solution is used the volume is made up to 100 C.C. with water. The beaker is covered with a watch-glass and heated on asbestos gauze over a Bunsen the flame being so regulated that boiling begins in four minutes. Boiling is continued for exactly two minutes and the cuprous oxide at once filtered without dilution on an asbestos felt in a Gooch crucible using suction the cuprous oxide being thoroughly washed with water at about 60" C.then with 10 C.C. of alcohol and finally with 10 C.C. of ether the ciucible transferred to a water-oven at 100' C. for thirty minutes cooled and weighed. The asbestos is best prepared by first digesting with 1 3 HC1 for two or three days, then washing free from acid and digesting for a similar period with soda solution, after which it is treated for a few hours with hot alkaline copper tartrate of the strength employed in the analyses. It is then washed free from alkali digested for several hours with HNO, and after a final washing is ready for use. The same felts may be used repeatedly the cuprous oxide being dissolved off each time with HNO,.A blank experiment should be made each day to determine the correction necessary for the slight spontaneous precipitation of cuprous oxide which takes place when copper tartrate is boiled and also for the slight loss of asbestos by solution in the alkaline liquid. The copper-reducing powers of 6-glucose invert sugar and two W. H. S 338 THE ANALYST. mixtures of invert sugar and sucrose have been determined and tables are given showing the equivalents for these of all quantities of cuprous oxide between 10 and 490 mgms. The results are summarized in the following formule where y=mgms. of cuprous oxide and x = mgms. of reducing sugar For &glucose y=0*5614+ 2.3484% - 0.001209~2; for invert sugar y = - 0,2460 + 2.27473 - 0.001077~~ ; for invert sugar and sucrose 0.400 gram total y = 6,3886 + 2.2279~ - 0*0009703x2 ; and for invert sugar and sucrose 2.000 grams total y = 20.6600 + 2.202133 - O-O00903Ox? W.H. S. The Determination of Sugar in Urines containing little Glucose. J. Blaise. (Ann. de Chinz. Ann. 1906 vol. 11 pp. 285-287.)-Most urines poor in glucose give when boiled with Fehling’s solution a yellowish-green precipitate which remains in suspension and prevents the exact observation of the end-point of the reaction. The simplest method of obviating this is to add a known quantity of glucose in the following manner 10 C.C. of the copper solution and 10 C.C. of the alkaline solution (corresponding to 0.05 gram of glucose) are mixed with 2 C.C.of a solution containing 0.01 gram of glucose and boiled. The copper oxide is immediately precipitated and the operation is then continued in the usual way with the urine to be examined. C. A. M. The Determination of Nitrosophenol. L. Lemaire. (Bull. SOC. Chim. Nord France 1906 64; through Arm. dc Chtim. anal. 1906 vol. ll. pp. 262 263.)-The method is based on the fact observed by Spitzer that on gently heating a solution of phenylhydrazine with a solution of a nitroso compound in glacial acetic acid nitrogen is liberated in accordance with the following equation : R.NO + C,H,N.NH = R.N + C,H + H20 + N,. Commercial nitrosophenol is a brown substance usually moist and containing variable amounts of impurities derived from the reagents used in its manufacture.In making an analysis 2.5 grams of the well-mixed sample are incorporated little by little with glacial acetic acid and the whole made up to 100 C.C. with the same acid. The apparatus used by the author is a 200 C.C. flask closed with a stopper in which are three openings. Through one of these passes a tube for the introduction of a current of carbon dioxide ; the second receives a bromine bulb the opening of which communicates by means of a T-tube with a carbon dioxide supply-tube whilst the third is connected with a condenser. A tap is placed between the T-tube and the flask so that the carbon dioxide can be passed directly into the flask or by way of the bromine bulb. The condenser is connected with a Duprk’s apparatus containing a solution of potassium hydroxide (1 2).Twenty C.C. of the solution of nitroso-phenol (= 0.5 gram) and 20 C.C. of glacial acetic acid are placed in the flask and the air expelled first from the flask and then from the bromine bulb by means of the carbon dioxide. The refrigerator is then connected with the collecting vessel and the expulsion completed by means of a slow current of the gas. A solution of 2 C.C. of phenylhydrasine in 40 C.C. of acetic acid is now introduced into the bromine bulb, the flask gently heated and the evolved nitrogen collected measured with the usual corrections for temperature etc. and calculated into NO. The percentage o THE ANALYST- 339 nitrosophenol NO.C,H,.OH in 0.5 gram of the substance can be obtained by means of the formula z = 1.449 x V" ( b - W) where V" represents the volume of nitrogen at 0" C.b represents the atmospheric pressure and w the tension of water vapour plus the tension of benzene vapour in mgms. of mercury at the temperature t. C. A. &I. Direet Estimation of Nitroglyeerine in Cordite etc. 0. Silberrad, H. A. PhiIlips and H. J. Merriman. (Journ. Xoc. Chem. Ind. 1906 XXV. 628-630.)-The method is based on the reduction of the saponification products of nitroglycerine FIG. 1. to ammonia with zinc iron and caustic soda. A weighed quantity of the ground cordite sufficient to yield about 2 grams of nitroglycerine is placed in a thimble in the Soxhlet retractor A which is fitted up as shown in Fig. 1. Eighty C.C. of absolut THE ANALYST. 340 ether is poured into the flask and extraction carried out in the usual way.When extraction is complete the thimble containing the residual nitrocellulose is washed with a little fresh ether and removed from the extractor. The absorption flasks C, containing 10 C.C. of & acid are now affixed and about 50 C.C. of a solution prepared by dissolving 5 grams of sodium in 100 0.0. of absolute alcohol run into the flask little by little through the side tube D. Reaction rapidly takes place and is com-pleted by warming on the water-bath for about six hours after which the ether is distilled up into the Soxhlet and run off by means of the tap the residue dissolved FIG. 2. in water and made up to 250 c.c. the aqueous Soxhlet and ether washings being also added to the solution. Fifty C.C. of this solution are then transferred to the flask F (Fig.2) 50 grams of a mixture of powdered zinc (2 parts) and reduced iron (1 part) added together with 50 C.C. of 40 per cent. sodium hydroxide solution and the ammonia distilled off in a slow current of air and collected in about 75 C.C. TG acid in the absorption flask H the excess of acid being titrated back. Each C.C. of & acid corresponds to 0.00757 gram of nitroglycerine. W. H. S. The Determination of Proteids by Means of Acetone. F. Bordas and Tout-plain. (Comptes Rendus 1906 cxlii. l345,1346.)-Proteids such as albumin casein, fibrin and gelatin are insoluble in acetone whether pure or diluted with a suitable quantity of water. Diastases and peptones are also precipitated by acetone which is thus a good reagent for the separation of fats from proteids.When the precipitation is made in the cold from proteid solution which should be neutral or nearly so th THE ANALYST. 341 liquid separated from the precipitate by means of centrifugal force will contain only a trace of nitrogen. I n the case of cheese 2 grams are ground up with 5 to 10 C.C. of water and 30 to 35 C.C. of acetone added little by little withcontinual stirring. The insoluble proteids are collected washed with dilute and finally with pure acetone, dried weighed ignited and the amount of ash deducted. Milk is analysed by treating 10 C.C. with 20 C.C. of acetone shaking the mixture to effect complete precipitation, separating the precipitate in a centrifugal machine and treating it as above described. For butter 10 grams are extracted with pure acetone and the residue treated with aqueous acetone which leaves the pure casein.On the Execution of the Comparative Analyses with '' gewachsene " (porous) Alu-mina. Wislicenus. (Ledermarkt Collegium 1906, 77 8 7 ; through Chem. Ztg. 1906 xxx. Rep., 167.)-The comparative analysis with '' porous alumina " (v. ANALYST 1904 xxix. 377) had to be delayed until a uniform material could be made on the large scale which has now been done by E. Merck. In the meanwhile it has been shown that the absorption of the tannin by the alumina, increases with increasing dilution of the solution, reaching a maximum at a concentration of 0.1 per cent. of tannin and decreasing again below this limit. The analysis is carried out in the apparatus shown in the figure.The Allihn tube F shortened to 7 ems. is charged with 2 grams of freshly ignited alumina and placed in the beaker B which contains the tanning solution diluted to twice its original volume. The vessel G serves to receive the first 10 C.C. of the filtrate which are not always quite clear; the tube S automatically interrupts the filtration when 110 C.C. have passed over which should require from one to three hours ; 100 C.C. of the filtrate are then evaporated and C. A. M. I dried for the determination of the '* non-tanning " materials. A. G. L. The Detection and Determination of Syringin. J. Vintilesco. (Journ. Pharm. Chim. 1906 xxiv. 145-154.)-Both the gIucoside prepared by the author from the plant and the commercial product after recrystallization from water had the characteristics given by Koerner.They contained 4-16 per cent. of water of crystallization melted at 190' to 192" C. and gave an intense violet-red coloration with concentrated sulphuric acid. The anhydrous syringin was found to have an optical rotation of aD = - 17O and on hydrolysis to yield d-glucose and an insoluble substance syringinin-Cl7H2.40 + = 2 0 = %Hl*O* + CBH1206 342 THE ANALYST. The author’s method of determining it in extracts of the leaves etc. of the lilac or privet is based upon its hydrolysis by means of emulsin the insoluble syringinin sub-sequently carrying down the small quantities of the enzyme left in the solution. Experiments with the pure anhydrous glucoside showed that 48,387 per cent. of glucose were formed by the action of the emulsin.Hence the quantity of the glucoside in a liquid not containing any other glucoside (which was the case with lilac and privet) could be calculated by means of Bourquelot’s formula, 1oog = 2Bm + 1059’ where q represents the amount of glucose set free in 100 C.C. of liquid and cor-responding to a return of 1” to the right in the optical rotation (L = 200 mm.) ; g the amount of glucose furnished by 1 molecule of the glucoside ; R the rotatory power of the glucoside ; and m its molecular weight (= 372). Thus a return of lo to the right in a solution of syringin acted upon by emulsin corresponds to the formation of 0-570 gram of glucose in 100 C.C. of the liquid-ie. to 1.178 gram of the glucoside. For the extraction of the syringin in quantity the author made use of the fact that hot ethyl acetate saturated with water will remove all glucosidal substances without extracting any appreciable quantity of sugars.One kilogm. of the finely-divided leaves etc. was thrown into 3 litres of boiling water containing calcium carbonate in suspension and the boiling continued for a few minutes to destroy any enzymes. The mass was then crushed in a machine and once more boiled in the hot water for a, few moments. The liquid was then cooled filtered and distilled under reduced pressure until a soft paste remained. This was extracted with the hot ethyl acetate and water and the extract on cooling left a deposit of syringin which could be obtained pure by a single recrystallization from water. Extracts of the fresh plant behaved differently to solutions of pure syringin on treatment with emulsin.I n the latter case it was necessary to add from time to time fresh quantities of the enzyme in order to effect the complete hydrolysis of 1.22 gram of syringin in 100 C.C. of water ; but this was not necessary in most instances with the extracts even when they contained a much larger amount of the glucoside (e.g., 3 grams in 100 C.C. in the liquid from lilac leaves and 3.6 grams from Japanese privet). The solubility of pure syringin is about 1.4 grams in 100 C.C. of water and as the above-named 3 and 3-6 grams were soluble in the extracts from the plants it shows that the solubility was increased by the presence of other extractives. The emulsin can only be added to the extracts from the plants after inversion of the cane sugar by the action of invertin and a determination of the cane sugar can thus be made simultaneously.C. A. M, The Amount of Sulphur in Commercial Petroleum Oils. R. Kissling. (Chem. Rev. Fett- u. Harz-Id 1906 xiii. 157 158.)-It was asserted by Grafe that commercial petroleum oils were approximately free from sulphur and in any case hardly ever contained more than 0.02 per cent. This is not confirmed however by the independent analyses of Engler and the author who have found that a proportion of 0.05 per cent. of sulphur is by no means exceptional in commercial petroleum lamp oils and that samples containing less than Griife’s maximum of 0.02 per cent THE ANALYST. 343 are of rare occurrence. The following are typical results Kaiser oil 0.01 ; astral oil, 0.02 ; ordinary Pennsylvanian petroleum 0.027 to 0.029 ; Russian (Baku) 0.027 to 0.029 ; Galician 0.039 to 0-061 ; American (Ohio) 0.039 to 0.05 ; and German (Alsace) 0-05 to 0.068 per cent.of sulphur. C. A. &I. The Examination of Turpentine Oils Utz. (Chenz. Rev. Fett- ZL. HaTx-Ind., 1906 xiii. 161-163.)-A determination of the bromine value was advocated by Vaubel (ANALYST xxxi. 200) as a means of judging of the purity of turpentine oil. From 1 to 2 grams of the sample were dissolved in chloroform the solution mixed with 100 C.C. of water 5 grams of potassium bromide and 10 C.C. of hydrochloric acid, and titrated with a standard solution of potassium bromate. The absorption of bromine was regarded as complete after thirty minutes and the absorbed bromine was calculated a8 having combined with the pinene to form a tetrabromide any further decomposition of this being neglected : C,,H,,+4Br= C,,H,,Br,, according to which 100 grams of pinene absorb 254 grams of bromine.In general, commercial turpentine oils were found to have a bromine value of 220 to 230 corresponding to 86.6 to 90.5 per cent. of pinene whilst the limits were 204 and 240. I n the author's experiments with this method the following values were obtained : Turpentine oils 222.2 to 241.2 ; pine oils 196.8 to 1974 ; double rectified pine oil, 197.4 ; pinoline (3) 3'7.68 to 90.48 ; rosin oils 65.22 to 78.24 ; dark rosin oil 113.70. Turpentine substitutes Ultra-turpentine oil 11.22 ; terpentane 9.6 ; hallol 107-0. From these results the author concludes that the variation in genuine oils is so great that the method cannot be relied upon as a test for the purity of turpentine oil, although it may be found of value in determining whether or no a given substitute contains pinene.Indian Turpentine Oil.-A sample obtained from Pinus long~olia (Roxb.) gave the following results Specific gravity 0,8734 ; optical rotation + 3' 13' ; solubility in 90 per cent. alcohol 1 in 7 or 8 ; and refraction at 15' C. 1.4788. C. A. M. The Characteristics of Owala Oil. K. Wedemeyer. (Chem. Rev. Fett- U , €€am-Ind. 1906 xiii. 210 211.)-The seeds known as '' Owala," are obtained from Peiztaclethra macrophylla a tree belonging to the Nimoseq and growing on the West Coast of Africa. The brilliant chestnut brown shells are flat and oval in shape.One kgm. of the fruit yielded on the average from 8 to 20 grams of seeds 20.6 per cent. of which was shells and 79.4 per cent. kernels. The entire fruit yielded 30.4 per cent. of oil on extraction with ether and contained 29.39 per cent. of proteids whilst from the kernel alone 41.6 per cent. of oil mas extracted and the residual pulp contained 48.25 per cent. of proteids. The extracted oil had a slight yellow colour and was fluid at the ordinary temperature though giving a slight deposit. I t had a pleasant taste with an after bitterness and an aromatic odour. When refined it gave a fine oil which would be suitable for food purposes. The following analytical results were obtained Specific gravity at 25" C. = 0.9119 ; refractometerireading (Zeiss) at 40" C.= 59.2" ; Hehner value 95.6 ; Reichert-Meissl value 0.6 ; saponification value 186.0 ; iodine value 9993 ; acid value 9.0 ; acety 344 THE ANALYST. value 37.1 ; unsaponifiable matter 0.54 per cent. ; melting-point of fatty acids, 53.9" C.; and solidification-point of fatty acids 52.1. The oil itself gave a white flocculent deposit when cooled to 18" to 19" C. and at 4O C. became a butter-like mass. C. A. M. The Occurrenee of Clupanodonic Acid in Herring and Whale Oils. M. Tsujimoto. (Journ. CoZZ. Engineering University of Tokio 1906 iv. ll-l4.)-Two samples of herring oil from CZupeapdasi and one of whale oil from Rhachianectes gluuca have been examined by the author. The fatty acids from the herring oils yielded 21-7 and 12.68 per cent.and those from the whale oil 27.8 per cent. of white bromides insoluble in ether and turning black before melting. All three contained from 69.23 to 70.12 per cent. of bromine (C,,H,,Br,O requires 69.84 per cent. of bromine) and the amount of carbon and hydrogen also agreed with the composition of clupanodonic octobromide. Hence the author concludes that clupanodonic acid is an important constituent of these oils though the amount (3.82 to 8.39 per cent. of the mixed fatty acids) is much less then in the case of Japanese sardine oil. No evidence could be obtained from an examination of the bromine cornpounds of the two highly unsaturated fatty acids C,,H,,O and C,,H,,02 found by Bull (Chem. Zeit. 1899 996) to be present in herring oil. C. A. M.The Detection of InOSite in Urine and other Fluids. G. Meilliere. (Tribune Mkdicale; through Ann. de Chim AnaZ. 1906 vol. 11 pp. 294 295.)-The following method is recommended as giving better results than any of those ordinarily used 25 C.C. of the urine are acidified with 2.5 C.C. of glacial acetic acid and treated with about 2.5 C.C. of a saturated solution of barium nitrate and the same quantity of a solution of lead nitrate (1 5) fol~owed by 3 to 8 C.C. of a 10 per cent. solution of silver nitrate. The precipitated silver chloride is separated with the aid of centrifugal force and the clarified liquid treated with ammonium hydroxide until a persistent turbidity appears then rendered distinctly alkaline with 12 drops of ammonium hydroxide and heated gently with 3 C.C.of lead subacetate solution (strength not given). The resulting precipitate which will contain the whole of the inosite is separated by centrifugal force triturated in 25 C.C. of water containing 5 drops of ammonium carbonate solution and again separated in the centrifugal machine. It is next suspended in 25 C.C. of water and treated with hydrogen sulphide the liquid evaporated to about 2 c.c. and after the addition of 20 C.C. of alcohol and 15 C.C. of ether allowed to stand for some time after which it is whirled. Subsequently the deposit is washed with 2 or 3 C.C. of water which is separated in the same way to remove the uric acid and the inosite can thus be obtained in a crystalline state. Obviously if the urine contained albumin the latter must be removed before testing for inosite whilst any sugar must be separated by means of fermentation.Inosite can be identified by treating it with nitric acid which converts it into an acid the cadmium and strontium salts of which have characteristic colours. Another test is to evaporate the inosite with a small quantity (10 drops) of acid mercuric nitrate a red d o u r being obtained as soon as the residue is dry. The reagent is prepared by mixing 10 grams of yellow mercuric oxide and 20 C.C. of nitri THE ANALYST. 345 acid with sufficient water to make up 200 C.C. The red coloration should not disappear on the addition of glacial acetic acid and on then adding 3 C.C. of water and 5 drops of a 20 per cent. solution of strontium acetate and warming the liquid should change to a dichroic rose tint recalling that of eosin solutions.According to the author inosite is a frequent constituent of urines especially of those that give an abnormal reduction when heated with Fehling’s solution with a green precipitate and apparently no deposit of cuprous oxide. C. A. M. Extraction of Fat from Fzeces and the Occurrence of Lecithin. J. H. Long. (Journ. Anzer. Chem. SOC. 1906 xxviii. pp. 704-706.)-The fat in faeces is found to be more completely extracted by spreading 10 to 15 grams of the sample (after moistening with very dilute HCl to decompose any soaps) over a strip of paper, rolling up the paper drying and extracting in a Soxhlet apparatus for two days with anhydrous ether than by drying grinding with sand and extracting from a paper shell in a Soxhlet for the same period. The amount of phosphates determined in the extract after evaporation of the ether amounted in three samples to 1.35 0.84 and 1.26 per cent. P,O respectively on the dry faeces which calculated as lecithin would correspond to a daily excretion of lecithin of 3 to 5-5 grams. No evidence could be obtained of any pathological condition in the man furnishing the material examined, and two further samples of faeces of the same individual tested some weeks later yielded 0.294 and 0.298 per cent. P,O respectively corresponding to an excretion of about 1 gram of lecithin daily. W. H. S

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DOI:10.1039/AN906310336b

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年代:1906

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THE ANALYST. 345 INORGANIC ANALYSIS. On the Analysis of the Metals of the Platinum Group. N. A. Orlow. Chem. Ztg., 1906, xxx., 714.)-Platinum, iridium, ruthenium, and rhodium, act catalytically on hydrogen peroxide ; osmium, on the other hand, is dissolved by hydrogen peroxide solutions, as is also osmium hydroxide, 0 s (OH),, which is oxidized to the tetroxide. Histological preparations blackened by osmic acid are decolourized by hydrogen peroxide, the osmium going into solution. The reaction may be used to separate osmium from the other platinum metals. Palladium chloride, PdCl,, acts on silver iodide with formation of the black insoluble palladium iodide. The chlorides of the other platinum metals do not show this reaction, which may be used to separate palladium from the other metals.The palladium may be recovered from the precipitate by treatment with potassium iodide or thiocyanate, or else by igniting it and treating the residue with aqua regia. A. G. L. Apparatus for the Determination of Arsenie. A. Kleine. (Chem. ztg., 1906, XXX., 585.)-The apparatus consists of it flask for the determination of arsenic by distillation. The flask has an upwardly-inclined side exit-tube, bent down sharply near its end, and ground into the funnel-shaped top of tt vertical spiral condenser ; the joint is made absolutely tight by keeping a little water in the funnel, The flask itself has a funnel-shaped top, with a central tube reaching to the bottom of the flask,346 THE ANALYST. which is closed during the distillation by means of a ground-in glass rod, this joint also being made quite tight by keeping some liquid in the funnel, The apparatus is made by Strohlein and Go., of Dusseldorf.A. G. L. A New Method of Separating Antimony and Tin. A. Czerwek. (Zeit. anal. Chem., 1906, xlv., 505-512.)-The method is based upon the formation of a double compound of stannic acid and phosphoric acid which is insoluble in water and nitric acid, but is partially soluble in dilute hydrochloric acid. I n order, therefore, to separate tin from antimony by converting the former into this compound it is essential that the nitric acid solution shall be completely free from chlorine ions. I n analysing an alloy, 0.5 gram of the sample is treated at 40° to 50" C. with a solution consisting of 15 C.C. of nitric acid (specific gravity 1*42), 15 C.C.of water, and about 6 grams of tartaric acid, and allowed to stand in a warm place, or at the ordinary temperature, for two or three hours, when the metals will have completely dissolved. The solution is now rapidly heated to incipient boiling and treated with 5 to 30 drops (according to the amount of tin) of a 45 per cent, solution of phosphoric acid (specific gravity 1*3), being meanwhile continually shaken. I t is next diluted with about 300 C.C. of boiling water and the precipitate allowed to subside on the water-bath, which will take about fifteen minutes, The clear supernatant liquid is decanted through a filter, the precipitate washed with hot water containing ammonium nitrate, and while still moist dissolved in warm ammonium sulphide ; the tin is then reprecipitated from the coZd and diluted solution by the addition of sulphuric acid.The beaker is left on the water-bath for some time, and the greenish-grey precipitate separated and washed as before. Finally it is dried, oxidized in a weighed crucible with nitric acid (specific gravity 1-42), dried on the water-bath, ignited, and weighed as tin dioxide. The filtrate from the tin is neutralized with ammonia heated with a sufficient quantity of ammonium sulphide, and acidified with acetic acid. The precipitate of antimony sulphide is left to settle on the water-bath and filtered off while still hot. It is then washed with water containing ammonium nitrate, and dissolved jn ammonium sulphide, the solution evaporated to dryness on the water-bath, and the residue oxidized in the usual way with fuming nitric acid, and weighed as antimony tetroxide.The accuracy of the method is shown by test analyses of alloys containing known quantities of antimony and tin. I n the case of alloys containing other metals in addition the tin is precipitated as described above, and the filtrate neutralized and treated with sodium or ammonium sulphide solution, which precipitates the other metals, whilst the antimony is separated from the new filtrate by means of acetic acid. Electrolytic precipitation from an ammonium sulphide solution has been found a suitable method of throwing down antimony and tin prior to their separation from each other. C. A. &I. A Modification of Schlagdenhaufen's Reaetion for Magnesium.J. Bellier. (Ann. de Chim. And., 1906, vol. 11, pp. 283-285.)-The following method of appIying the colour reaction of magnesium salts with alkali hypoioditesTHE ANALYST. 347 is capable of detecting 1 part in 20,000: About 10 C.C. of the solution of the magnesium salt are mixed with 1 C.C. of a 1 per cent. solution of potassium iodide saturated with iodine, and the mixture shaken with 15 drops of & sodium hydroxide solution. I n the presence of 0.1 gram of magnesium the liquid becomes reddish-brown, and then gives a flocculent deposit of the same colour. With 0.05 gram there is only a brownish to yellowish-red coloration. Ammoniacal salts prevent the reaction altogether, as do also acids and alkalies, whilst calcium salts in large quantity render it less sensitive.The reaction cannot be used for the gravi- metric determination of magnesium, owing to the solubility of the precipitate in water. C. A. M. Iodometric Determination of Vanadic Acid. P. Hett and A. Gilbert. (Zeit. ofentl. Chem., 1906, xii., 265, 266.)-Although other chemists have found that the reaction between vanadic acid and potassium iodide in acid solution is untrust- worthy, the authors state that they have obtained good results by the method. The vanadate salt or ore is fused with sodium hydroxide, the melt dissolved in water, filtered, and the filtrate diluted to a known volume. A portion of the solution is then acidified with either hydrochloric or sulphuric acid, potassium iodide is added, and the liberated iodine titrated as usual. The reaction proceeds according to the equation, V,O, + 2HI = V,O, + H,O + 21.w. P. s. A Qualitative Test for Phosphorus. Mauricheau-Beaupre. (Comptes Rendas, 1906, cxlii., 1206, 1207.)-This is based on the fact that glass heated to red- ness and brought in contact with the vapours of phosphoric acid is rendered opaque. Hydrogen or acetylene burning in a Bunsen burner gives the best flame for the purpose, but either gas must be freed from any hydrogen phosphide by passing it through sulphuric and chromic acids. The test is so sensitive' that acetylene con- taining only 1 part in 10,000 of hydrogen phosphide makes the glass opaque. In applying the test, a piece of glass tubing, 5 t o 10 mm. in diameter, is supported on a platinum wire at the top of the oxidation zone of the flame.I n the case of metals, such as iron, in which the phosphorus is liberated by the action of an acid, the impure hydrogen is conducted into the air-holes of the Bunsen burner, or it can be burnt directly from a metallic jet. Organic compounds are burnt in the upper part of the blue zone of the flame, the glass tube being heated to redness above. The reaction does not take more than one to two minutes, whilst even ten minutes' heating is insufficient to devitrify the glass in the absence of phosphorus. Glass heated in a, pure flame loses in weight, whilst if phosphorus was present it gains in weight (e.g., 0.001 gram on 6.94 grams). I n one experiment the part of the tube rendered opaque was found to contain 0.718 per cent. of phosphorus, none being present in the unattacked glass.Hydrofluoric acid vapour when present in the gas in only small quantities does not attack glass at red heat, whilst compounds of arsenic, or antimony, or boric acid, do not give any deposits that could be confused with the phosphorus deposit. C. A. M.348 THE ANALYST. Determination of the Sodium Phosphates. C. C. Ahlum. (Journ. Amer. Chem. Xoc., 1906, xxviii., 533-537.)-Disodium hydrogen phosphate and trisodium phosphate are both alkaline to methyl orange, and may be titrated with hydrochloric acid, the reactions being : HCl + Na,HPO, = NaH,P04 + NaCl ; 2HC1+ Na,PO, = NaH,PO, + 2NaC1. Two methods are given for the separate estimation of the two salts in a mixture containing both, the first based on the conversion of Na,PO, into Na,HPO, with formation of Na,CO,, when CO, is passed through its aqueous solution, according to the equation GO, + 2Na,PO,+ H,O = 2Na,HPO, + Na,CO, ; and the second depending on the fact that, when a solution containing Na,HPO, and Na,PO, is acidified, and then neutralized with Na,CO,, adding an excess of the latter, the resulting solution contains Na2RP0, and Na,CO,.In both cases the total alkalinity of the original mixture is titrated with I n the first method, 2 grams of the mixed salts are dissolved in water, and CO, passed through the solution until reaction is complete (about ten to fifteen minutes). The solution is then evaporated to dryness, and the Na,CO, in the residue estimated in the Schrotter apparatus, the amount of CO, evolved multiplied by 7.4545 giving the amount of trisodium phosphate present.The number of C.C. & acid, equivalent to the trisodium phosphate, is readily calculated from the above equation, and this, deducted from the number of C.C. used in the titration of the original, gives the number required by the disodium hydrogen phosphate, and this, multiplied by 0.0142, gives its amount. For the alternative method, 1 gram is dissolved in 50 C.C. water containing a drop of methyl orange. A slight excess of HC1 is added, and the solution boiled for ten minutes, after which an excem of Na,CO, is added, and the solution concen- trated as far as possible by boiling, transferred to a tared platinum dish, evaporated on a steam-bath, dried, and weighed. The mass is then pulverized with a porcelain pestle, halved, and the CO, determined in one half by the Schrotter apparatus, the other half being titrated with HC1.The difference between the number of C.C. acid used in the titration of the original mixture and that used in the latter titration, minus the number of C.C. equivalent to the Na,CO, found by the Schrotter apparatus, represents the loss in alkalinity due to the conversion of the Na,PO, into Na,HPO,, and this, multiplied by 2 ~ 0 . 0 0 8 2 , gives the amount of Na,PO,, the difference between the number of C.C. of acid equivalent to the Na,PO, and that required by the original, multiplied by 0-0142, giving the amount of Na,HPO,. HC1 before treatment. W. H. S. Methods for the Determination of Carbonic Acid. W. Holtschmidt. (Chew%. Ztg., 1906, XXX., 621.)-The author uses acid potassium tartrate to decompose the carbonate, the evolved carbon dioxide being either weighed after absorption by soda-lime, or titrated after absorption by caustic alkali.The acid potassium tartrate acts on carbonates only at the boiling temperature, and hence vigorous and continued boiling is necessary to insure complete decomposition. In order to obviate theTHE ANALYST, 349 difficulties caused by the large amount of condensed water obtained, the author has devised special and complicated forms of apparatus, by the use of which very good results are obtained. A. G. L. Difficulties in the Determination of Carbon Monoxide in Gaseous Mixtures. A. Gautier and Clausmann. (BUZZ. SOC. Chim., 1906, XXXV., 513-519.) -In analysing a mixture of nitrogen or air with carbon monoxide, or of nitrogen and various combustible gases with carbon monoxide, it is not possible to recover the whole of the latter gas, either by explosion in the presence of oxygen, or by washing with cuprous chloride solution.Thus after two successive washings as much as 1 per cent. of carbon monoxide may be left in the residual gas, whilst from 0.3 to 0.5 per cent. may remain after explosion of the mixed gases in the eudiometer. If, how- ever, the gases left after the explosion or aft;er the washing (diluted with air or not according to circumstances) be made to circulate through a tube containing iodic anhydride heated to 70" C., the last traces of carbon monoxide are oxidized and an exact determination can be made. I n the ordinary method the small amount of carbon dioxide which may be found in the eudiometer after explosion of the gases left from the washings with potassium hydroxide, bromine, and cuprous chloride, might lead one t o infer the presence of saturated gases, such as methane, in the original mixture, whereas it might really be due to the oxidation of the carbon monoxide that had not been removed by the cuprous chloride. The apparent volume of the residual nitrogen is increased by the uncombined carbon monoxide and that formed from the pyrogallol, but is reduced by the slight oxidation of the nitrogen itself during the explosion in the eudiometer. C.A. M. Determination of Hydrogen Peroxide. W. E. Matthewson and J. W. Colvin. (Amer. Chem. Jozmz., 1906, vol. 36, pp.117-123.)-Hydrogen peroxide may be estimated by diluting with water until the solution is approximately q, and adding this solution from a burette to about 2 grams of ferrous ammonium sulphate dis- solved in a little water, together with a few grams of ammonium sulphate and some phosphoric acid, a solution of titanium, which gives a deep yellow colour with the slightest excess of H20,, being used as indicator. The titanium solution is prepared by fusing the dioxide with about ten times its weight of KHSO,, dissolving the fused mass in cold dilute H,SO,, and filtering. An attempt to determine sodium nitrite by titrating with a standard solution of H202 gave slightly too high results, and for accurate results the titre of the peroxide solution should be fixed with a known amount of nitrite. W. H. S. The Use of Sodium Hydrosulphite in Gas Analysis. H. Franzen. (Berichte, 1906, xxxix., 2069-2071.)-A solution of sodium hydrosulphite is recom- mended as an absorbent for oxygen in gas analysis. The absorption of the gas takes place in accordance with the equation-- Na,S,O,+ H,O + 0 = 2NaHSO,, according to which 64 C.C. of oxygen enter into combination with 1 gram of the salt. A suitable solution for gas analysis is obtained by mixing a solution of sodium hydro-350 THE ANALYST. sulphite (50 grams in 250 c.c.) with 40 C.C. of a solution of 500 grams of sodium hydroxide in 700 C.C. of water. One C.C. of this solution will absorb 10.7 C.C. of oxygen, the absorption being as rapid at low as at higher temperatures, The reagent, which is cheaper than pyrogallol, can be used in the anaIysis of mixtures of gases containing carbon monoxide and dioxide. C. A. M.

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DOI:10.1039/AN9063100345

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年代:1906

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350 THE ANALYST, APPARATUS. Improved Beckmann Apparatus for Molecular Weight Determinations. J. McC. Sanders. (Proc. Chew. Xoc., 1906, xxii., 165.)-The difficulty of equalizing the overcooling for parallel observations with the solvent and solution, and in the \ c n q U A 11 U i addition of ice crystals for inducing congelation, in the ordinary Beckniann apparatus is overcome by the use of a modified form of inner tube. A narrow, almost capillary tube (A) is fused into the bottom of the solution tube, and attached to a thin rubber tube and small rubber bulb (B). The con- tained tube is placed in an outer jacket the’wall of which is in contact with the side tube A. The liquid in A is first completely expelled by compressing B, and the rubber tube pinched while B is removed, allowed to fill itself with air, and replaced, when on releasing the rubber tube a small amount of solvent rises in A, which, in operation, being nearer to the source of cold, freezes first, and at the moment desired a mass of crystals can be projected into the main body of the solvent by a sharp compression of the bulb B.C is a pneumatic stirrer, an adaptation of the photographic ‘‘ shutter release,” the piston and cylinder being of aluminium or glass, ground to fit perfectly, and the agitator E being made by flattening and twisting a piece of platinum wire, which is, then coiled into a spiral form, and the other end of the wire attached to the piston. The spring is of hard-drawn aluminium or platino-iridium wire, A small vertica tube (D) passing through a third hole in the rubber stopper replaces the ordinary side tube of the Beckmann apparatus, and serves for the introduction of the substance.The apparatus can be adapted from a small Soxhlet extraction tube by cutting off theTHE ANALYST. 351 upper and lower parts and the wide side tube, and bending the narrow siphon into the form of A. W. H. S. A Simple Form of Rotating Electrode for Eleetro-chemical Analysis. (Chem. News, 1906, vol. 93, p. 283.)-In the apparatus shown F. Mollwo Perkin. in the figure, the vessel in which the elec- trolysis is carried out consists of a tap-funnel, which allows of easy washing of the cathode without interrupting the current. The elec- trodes are made of platinum alloyed with 20 per cent. of iridium, which forms a very rigid alloy.They are of wire 1 mm. in diameter; the anode consists of a few wide turns, whilst the cathode has a, large number of turns, and a total surface of 23 square cms. The electrodes may preferably be sand- blasted. A nickel wire may also be used as cathode and will last for a large number of determina- tions, being but little attacked by the nitric acid used in removing the deposited zinc, copper, etc. I n six copper analyses made with this apparatus the error ranged from 0 to 1.3 mgms., on from 0.05 to 0.13 gram of copper. The author mentions that Johnson, Matthey and Co. now supply iridium of 99 per cent. purity ; the metal is as hard a8 steel, unattacked by boiling aqua regia and by molten lead. It cannot be drawn into wire, but may be rolled into sheets whilst hot.A. G. L. A New Burner for Spectroscopic Work. E. H. Riesenfeld and H. E. Wohlers. Fig. 1, consists in electrolysing the solution to be examined in the interior of a, Tech burner, the fine spray produced by the gas bubbles at the electrodes being carried up into the flame by the current of air sucked in by the gas. The burner is made in two parts, an upper one B fitting on a support C ; the support also carries the vessel A, which holds 2 c.c, of the liquid to be tested, and into which dip the platinum-iridium wire electrodes. The current should have a strength of 0-2 to 1 ampisre at 8 to 16 volts. For metals such as copper or thallium, which are easily deposited, a current reverser should be inserted in the circuit, and the current reversed every minute, Fig.2 shows a convenient arrangement of the whole, B being the current reverser; the lamp used as resistance (Chem. Ztg., 1906, xxx., 704.)-The principle of the burner, shown in FIG. 1.352 THE ANALYST. is conveniently utilized to illu- minate the scale of the spectro- scope. The 2 C.C. of liquid used suffice to give an intense and steady spectrum for two hours, at the end of which time the vessel will re- quire filling up with water. The spectrum disappears as soon as the current is interrupted, the current of gas cleaning the burner at once. The burner may also be used as a convenient source of monochro- matic light. The apparatus may be obtained from Franz Hugers- hoff, of Leipsic. FIG. 2. A. G. L. @ a + @ @ @ THE SALE OF FOOD AND DRUGS ACTS: SOME DEFECTS AND SUGGESTED REMEDIES. AN intelligent and moderately written article. on the above Acts has recently appeared in the pages of our contemporary, the PharrnaceuticaZ Journal of August 25, 1906, from the pen of Richard A. Robinson, junior, barrister-at-law, and assistant editor of that paper. Most of the points contended for have long been recognised by all thoughtful public analysts; indeed, so far is this the case, it is owing to this recognition that the joint committee of this Society and the Pharmaceutical was appointed to cope with cases of difficulty in drug adulterations. At the same time it should be remembered that the public analyst is not always to blame for ill-advised prosecutions ; he is not the prosecutor, but is bound to analyse and report upon any sample sent him by his Authority, and, though he may give his opinion that a prose- cution in a certain case would be unadvisable, this opinion may or may not be acted upon by the body under which he serves. . s , * @ 4 3 + W. J. S.

ISSN:0003-2654    

DOI:10.1039/AN9063100350

出版商:RSC    

年代:1906

数据来源: RSC

摘要:

352 THE ANALYST. REVIEW. THE ANALYSIS AND VALUATION OF OXIDE OF IRON AND LIME FOR THE PURPOSES OF GAS PURIFICATION. By H. LEICESTER GREVILLE, F.I.C., etc. (Published by Walter King. Price 2s. 6d.) This pamphlet contains a record of the processes used for the valuation of some of the raw materials used in a gas-works, and the spent products and residuals derived therefrom. As chemist to the Commercial Gas Company, the author had exceptional opportunities of putting to the test the processes of examination which have been suggested from time to time, and in this pamphlet describes those that he adopted, a8 well as those of his own suggestion. The pamphlet contains very few mistakes, and indicates that a more compre- hensive work, free from debatable opinions, from the pen of this author, would be of considerable service to his colleagues. W. J. D.

ISSN:0003-2654    

DOI:10.1039/AN9063100352

出版商:RSC    

年代:1906

数据来源: RSC