摘要:

BUTTERS FROM VARIOUS COUNTRIES COMPARED. BY C. ESTCOURT, F.I.C. (Read at the Neeting, February 7, 1900.) DURING the last twelve months I have analysed a considerable number of samples of butter for the direct importers of such produce, representing shipments from Ireland, Denmark, Sweden, Germany, Canada, and Finland. I a m able to give the following results of the analyses of about 250 samples, the origin of each of which I ascertained and noted :114 THE ANALYST. Water in Buttey. Average of Water. Origin of Samples. Total Samples. Percentage Finnish ... ... 85 12.3 Danish ... ... 89 13.5 Irish ... ... 39 14.1 Swedish ... ... 14 13.T5 Canadian ... ... 10 13.2 German ... ... 8 13.5 Highest Percentage of Water. 18.0 18.0 20.0 17.8 19.4 14.8 Lowest Percentage of Water. 8.0 9.0 9.0 11.8 10.0 11.4 W a t e ~ .The percentages of water, as will be seen from the tables just given, vary con siderably in the produce of every country with the exception of Germany. I give in the foregoing tables the average, as well as the highest and lowest figures. On reviewing the results, I find in Irish butter that, of the thirty-nine samples examined, only four contained more than I8 per cent. of water, three contained more than 16 but less than 18 per cent., as many as twenty-three contained from 12 to 16 per cent., and the results obtained from nine samples gave figures falling below 12 per cent. I n the case of the Danish samples only nine contained more than 15 per cent. of water, while six contained less than 12 per cent. The produce from Finland showed that only three samples of the eighty-five analysed contained more than 15 per cent.of water, twenty-six contained between 13 and 15 per cent., and the remainder, fifty-six, were all under 13 per cent. The Finnish butter, therefore, must be deemed a most satisfactory article as regards the quantity of water. Of the Swedish samples, six showed water to the extent of 14 per cent. and above, the highest being 17.8 per cent. The Canadian samples gave results varying from 10 to 15 per cent. of water, with the exception of one sample which was found to contain as much as 19.2 per cent. The German produce gave results much more constant : six of the eight samples analysed contained from 12 to 14 per cent., and one 14.8 per cent. of water. The exceptional one contained 11-4 per cent.It will appear from the results obtained with the Irish butters that where care is exercised, as it is at the creameries, no great excess of water is found. Samples Examined for Preseruatives. Origin of Samples. Finnish Danish Irish Swedish Canadian German ... I . . ... ... ... ... Total Samples Examined. 74 85 37 13 10 8 Samples not containing Preservatives. 7 3 82 2 13 9 8 Samples containing Boric --L-. r- Average Highest in Grains, in Grains, per pound. per pound. 8.3 - 5.3 8.0 24.7 46.0 9.0 - - - Acid. - \ Lowest in Grains, per pound. - 4.0 5-0THE ANALYST. 115 Preservatives. As regards the examination of the samples for preservatives, it will be seen from the tabulated results that not a single sample of the German and Swedish imports was found to contain any.Of the ten Canadian butters, one contained boric acid, and that only to the extent of 9 grains per pound. Eighty-five specimens of Danish butter were examined, and in three samples only could any preservative be found, namely, boric acid, and the highest quantity contained in a sample was 8 grains per pound. Of the seventy-four samples from Finland, only one was found upon examination to contain boric acid, namely, 8.3 grains per pound. Therefore the percentage of the samples of Danish and Finnish butter containing preservative is very low and scarcely worthy of notice. The same cannot be said of the Irish production, of which all the samples were found to contain boric acid, varying in quantities from 5 to 46 grains per pound.Of the thirty-five samples in which preservative was found, eight contained apwards of 35 grains per pound of boric acid, including two containing above 40 grains. Nineteen showed results between 20 and 35 grains per pound, and seven samples contained quantities below 12 grains of boric acid. These results are rather surprising following upon those of the analyses of the produce of other countries, which rather tend to show that a preservative is not absolutely necessary. Figures obtained by the Reichert Process. Origin of Samples. Finnish ... ... Danish ... ... Irish ... ... Swedish ... ... Canadian ... German ... ... Total Samples. 85 90 39 14 10 8 Average Figure. 13.8 15.2 14-0 14.4 14.1 15.3 Highest Figure. 17.6 17.0 15.5 16-2 15.5 16.2 Lowest Figure, 11.9 12.5 12.8 13.7 13.0 13.5 Results obtained by the Reichert Process.Coming to the composition of the fats of these different butters, the results obtained by submitting them to the Reichert test are given below ; and a few notes I have made may be of some interest to the members of this Society. Taking the Finnish butters first, the fats of eighty-four samples were examined, and gave an average Reichert figure of 13.8; only eight gave Reichert figures of 16 and over ; whilst twenty-one samples showed results below 13, including two results of 11.9. These two samples I returned as adulterated, and they accordingly were sold as coufectionery butter. With regard to the Irish butters, only four gave Reichert numbers below 13, and116 THE ANALYST. seventeen samples were lower than 14; there was not much variation among the remainder of these thirty-nine samples, the figures of which ranged from 14 to 15.5.Of the Danish samples, ninety were analysed, and as many as twenty-two gave Reichert figures of 16 and above, including two of 17, showing a very large percentage having a high Reichert number. There were only three giving numbers of 13 and lower, the general figure for the remaining sixty-five samples being about 15. Denmark may be said to produce a butter of very good quality, and the Reichert figure of which is fairly constant. The butters of German and Swedish origin appear to be of even composition, as evidenced by the results obtained by the Reichert test. Of the Swedish, only one of the fourteen samples gave a figure so low as 13.7, the next lowest being 14.4, and this is the average figure for the whole of these samples. The results of the German butters were higher on the whole than the Swedish, though the lowest in this case was 13.5. Although the Canadian and Irish agree practically as regards the average Reichert figure, the former have a greater percentage of samples whose figures come as low as 13 to 13-5. Four out of the ten are below 13.5, while the remainder agree fairly with the Irish.

ISSN:0003-2654    

DOI:10.1039/AN900250113b

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

116 THE ANALYST. NOTES ON SOUR MILK. BY H. DROOP RICHXOND, F.I.C., AND J. BRISTOWE P. HARRISON, A.I.C. (Rend at the Meeting, Febrzcary 7, 1900.) I. THE DETERMINATION OF THE SPECIFIC GRAVITY OF SOUR MILK. WEIBULL (Chem. Zeit., 1893, xvii. 1679) proposed, in order to determine the specific gravity of sour milk, the addition of a known volume of ammonia; the density of the mixture, corrected for the volume of ammonia added, of which the density is known, gives the density of the milk. It has been our practice to slightly modify this method; we add to each 100 C.C. of sour milk 5 C.C. of strong ammonia, and to the density of the mixture we apply a constant correction deduced from the change of density on adding 5 C.C. of strong ammonia to 100 C.C. of fresh milk; this correction has varied from 0.0065 to 0.0070 with different samples of strong ammonia. We can fully confirm Weibull’s statement that the density of sour milk can be accurately determined by this means, and have used the method extensively. De Koningh (ANALYST, xxiv.142) has substituted a soIution of caustic soda (specific gravity 1,030) for the strong ammonia; he finds that a, constant correction of 0.0008 must be added to the results, this being the mean figure by which the density is lowered on mixing 5 C.C. of soda solution with 100 C.C. of milk. He accounts for the lowering of density by the assumption that calcium phosphate is rendered insoluble; we neither entirely confirm his figure nor are we satisfied with his explanation; as we propose to show, the correction is not constant, but variesTHE ANALYST.117 with the “acidity” of the milk, and can be, we think, explained when the action of acids on alkalies is considered. In Table I. we give the densities of solutions of caustic Bodti, ammonia, and sulphuric and hydrochloric acids, and the salts resulting from their mutual action. The figures are obtained by interpolation from well-known tables, which we have taken from the C‘lzemiker Kalender, and are expressed in terms of 2, &, and :G solutions ; they are probably correct to the fourth place of decimals. TABLE I. Densities of Sol4ons of Bases, Acids, and Salts. Substance. NaOH ... NH, ”.. HC1 ... H,S04 ... NaCl ... NH,C1 ... Na,80, ... (NH4)@04 E 5’ 1-00920 0.99856 1.00372 1.00774 1.00846 1.00338 1.01266 1.00752 i% 1.00465 0.99928 1.00186 1.00387 1 *00423 1.00169 1-00639 .l-00376 x Authority -5r 1.00235 Lunge.0.99964 Carius. 1.00093 Lunge and Marchlewski. 1.00193 Lunge and Isler. 1.00212 Gerlach. 1.00085 Y , 1.00322 1*00188 scdlff. If a salt in solution had a density which was the sum of the densities of the acid and base of which it was composed, the density of a solution of a salt should be equal to the sum of the densities of corresponding strengths of its acid and base, less 1. This is not, however, the case, and the difference between the sum the densities of the acid and base (less I), and the density of the salt is given Table 11. : NaOH. NH,. --- - 7- -- HC1. H,SO,. HC1. H,SO,. N 5 ... - 0.00446 - 0.00428 + 0*00110 + 0.00122 - Is + 0*00055 + 0.00061 I ... - 0.00228 - 0.00213 -l< 2 0 ...- 0.00116 - 0*00106 + 0.00028 + 0.00031 its of in As the acidity of fresh milk is about &, and that of sour milk about $o to &, it is seen that the change of density on neutralization will go a long way towards explaining the change noticed by De Koningh. Thinking that it would not be quite correct to compare the acids such as sulphuric and hydrochloric, with milk, we have made a few experiments with weaker acids. We prepared a solution of caustic soda of density 1.032, which was 0.666 N., and determined the densities of various dilutions of this with water. There were : No. of C.C. diluted to 100 C.C. =x. Density found. Density calculated. 4.10 1.00138 1.00 13 8 7-96 1.00266 1.00265 11-81 1.00388 1 -00391 Formula : Density = 1 + 0.000339~ - 0~0000007~2. The determinations show that when 5 to 20 C.C.of this solution are added to 100 C.C. the density is about 0.0001 higher than that calculated proportionally.118 THE ANALYST. A soIution of citric acid, 1.0064 N., was prepared ; the densities of various dilutions were determined : No. of C.C. diluted to 100 C.C. =r. Density found. Density calculated. 2-39 1.00059 1.00064 4.80 1-00135 1*00130 7.47 1-00200 1.00201 Formula : Density = 1 + 0.0002688~. Solutions were now made up containing varying quantities of citric acid and a slight excess of soda solution : NO. of C.C. of Citric Acid in 100 C.C. No. of C.C. of Soda in 100 C.C. Density foluld. 2.41 4.04 1.00174 1~00200 4.82 8-48 1 -00361 1.00412 7.41 11.99 I *00524 1.00595 The calculated density was obtained by adding together the figures obtained by calculating the densities due to the citric acid and soda by the formula given above, and subtracting 1.Fifty C.C. of a solution of lactic acid diluted to 100 C.C. (making 0.0256N) had a density of 1-00060; 50 C.C. of this solution + 4.76 C.C. solution of caustic soda, diluted to 100 c.c., had a density of 1.00195. Calculated to a strength of FD, the differences are for citric acid 0.00105, 0.00104, and 0.00095, or a mean of 0*00100, and for lactic acid 0,00098, figures which are less than half that given by the stronger acids. As citric acid, in addition to being a weak acid, is a tribasic acid, we thought that the lower figure obtained might be partly due to the three hydrogen atoms not having the same value.I t was convenient to test this question in the first instance with oxalic acid on account of the ease with which normal and acid salts could be prepared. We made a quantity of each salt, the purity of which is shown by the following figures : The calculated density was 1.00220. Sormal Salt Na,C,O, Acid Salt NaHC,O;OH, h A f- . r- 7 Found Theory Found Theory Total C204 65.55, 65.48 65-67 67.58, 67.82 67.69 C20, (as acid) none none 33.61 33.85 Loss in water-bath none none 13.92 13.85 Further loss at 105" to 110" none none none none The following densities were determined : Oxalic acid 0.0406 N. ... ... ... ... ... 1.00082 ,, ,, 0.10 N. ... ... ... ... ... 1.00217 0.2597 N. ... ... ... . r . ... 1.00563 (iii.) *NaHC,04 0.20 N, ... ... ... ... ...1.00720 per 100 C.C. had been added = 0.0961 N. ... ... 1.00572 G.) { (ii.) ++P;i)&z~~d: 0.10 N. ... ... ... ... ... ... 1.00556 (iv.) Oxalic acid 0-10 N., to which 14.43 C.C. soda solution * These two solutions contained the same sniount of sodium.THE ANALYST. 119 From the above figures we calculate the following losses of density for ;k solutions : When the total acidity is neutralized from i., ii., and density of NaOH 0'00126 from i. and iv. , . . ... ... 0'00124 When the first hydrogen atom is neutralized from i., iii., and density of NaOH 0.00179 When the second hydrogen atom is neutralized from i., ii., and iii. ... ... 0*00053 froin i., iii., and i v . ... ... 0*00068 froin i., ii., iii., and iv. ... ... 0.00071 7 7 J > 7 2 I J 7 7 7 7 7 7 7 7 7 7 7 7 9 7 7 7 > 7 , J from ii., iii., and density of NaOH 0.00073 7 - I 7 7 , 7 7 7 , From the above results it appears that the first hydrogen atom in oxalic acid is the more powerful.It is seen from the above that although neutralization of an acid by soda always produces a loss of density, the figure varies not only with the acid, but also with the hydrogen atom neutralized in a polybasic acid. For this reason it is useless to apply any theoretical correction for milk, and we have made Borne experiments to see if we can find a value which may be used in milks. To milk of density 1.0319 increasing quantities of soda solution were added and the densities taken. Three C.C. of the solution rendered this milk exactly neutral to phenolphthalein. (iuantity added.Density. 1 C.C. to 100 C.C. 1.03175 2 1, 9 , 1-0316 3 $ 9 $ 7 1.0316 4 7 , ,, 1,0316 Five C.C. of soda solution was added to 100 C.C. of different milks, and the densities determined. 1.0339 1.0334 Original . .. 1,0325 1.0327 1.0319 1-0328 1.0338) 1.0309 1.0328 Alkaline . . . 1.0322 1.0321 1.0316 1.0324 1.0335) 1.0306 1.0325 The third milk in the above table was allowed to get sour; when the acidity was equal to 9 C.C. of the soda solution for 100 c.c., it still was liquid, and had ti density of 1.0319. On the addition of 5 C.C. soda solution the density fell to 1.0316, and to 1.0310 by the addition of 10 C.C. ; when 15.1 C.C. were required to neutralize it, the addition of 20 C.C. of soda dissolved the precipitated curd, and the density was 1.0298. In each case Weibull's method, applying the correction found for fresh milk, gave a density of 1.0320.The following additional experiments were performed : Origiiial Density of Milk. Acidity. Soda added. Density of Alkaline Milk. 1-0331 136" 21 C.C. 1.0300 1.0326 124" 19 C.C. 1.0302 Fresh milk has, according to our experience, an average acidity of 20', and we assumed that all the milks tested in a, fresh condition had this acidity.120 THE ANALYST. Tabulating the acidities and the lowering of density, we get : Original Density. 1.0319 9 , 1&25 1.0327 1,0319 1.0328 1.03385 1-0309 1.0328 1 -0319 1&26 1.0331 Acidity Neutralized. 6.7" 13.3" 20.0" 20.0" 20.0" 20.0" 20.0" 20.0" 20.0" 20.0" 33.3" 60.0" 101*0" 124.0" 136.0" Lowering of Density. 0.000 15 0*0003 0.0003 0.0003 0*0006 0.0003 0.0004 0.0004 0*0003 0.0003 0*0003 0*0009 0.0021 0.0024 0.0031 Calculated Original Density.1-0319 1.0319 1.0320 1.0326 1.0325 1,0320 1.0328 1.03385 1.0310 1.0329 1.0323 1.0321 1.0318 1.0327 1.0327 The figures calculated are obtained on the assumption that each degree of acidity causes a lowering of the density of 0.00002, and with this correction the results are fairly accurate. On referring to Table 11. we see that with strong acids the change of density on neutralizing with ammonia is very much smaller than with soda, and in the opposite direction, and our results with milk indicate that it may practically be neglected. This is due partly to the fact that dilution of strong ammonia produces a small change in density in the direction opposite to that due to neutralization, and partly to the fact that there may be a small loss in solids when milk becomes sour, and the small errors in the one case tend to neutralize the small errors in the other.With De Koningh's method the errors are larger, and tend in the same direction, and though an approximate correction depending on the acidity of the milk can be worked out, it appears preferable to use Weibull's method. 11. THE POINT AT WHICH MILK MAY BE CONSIDERED SOUR, AXD THE RATE OF There is considerable divergence of opinion as to the degree of acidity at which milk may be considered sour. Thus Stokes (ANALYST, xvi., 122) states that milk which has not yet reached an acidityof 0.3 per cent. lactic acid (33.37, but is near it, will coagulate on boiling; he records, however, the fact that.three samples did not coagulate when the acidity had reached 0.54 per cent. lactic acid (60"). He also gives figures which show that milk tastes sour at an average acidity of 0.396 per cent. lactic acid (44"). Thorner (Chem. Zeit., 1891, 1108) gives 23" as the acidity at which milk curdles on boiling, and gives the normal acidity of milk as 12" to 16". Rideal and Foulerton (Pz~bZic HeaZth, May, 1899) say that milk turns sour at an acidity of 0.5 per cent. lactic acid (55.6"), but Rideal (Lancet, January 27, 1900, 228) finds that milk curdles on boiling at 28" acidity, while with other samples slight coagulation was noticed at 25.6" and 21.6". We have made a series of experiments, and our figures confirm almost absolutely SOURING IN THE PRESENCE OR ABSENCE OF PRESERVATIVES.THE ANALYST.121 the figures of Stokes. the variations are fairly wide. milk curdles on boiling : On the average we find that milk tastes sour at 45", though The following experiments show the point at which 1. 11. 111. ... iv. V. vi . vii. ix. ... v111. ... ... ... ... ... ... Acidity. 33.3" 28.0" 52.0" 32.7" { 33;:;: 24.7" 37.5" 34.9" 32.5" Remarks. ... Faintly curdles on boiling. ... Curdles on warming. ... Curdles on boiling. ... Does not curdle on boiling. ... Faintly curdles on boiling. ... Curdles on boiling. Does not curdle on boiling. ... ... Curdles on boiling. ... Just curdles on boiling. ... Just curdles on boiling. The acidity at which milk curdles on boiling is about 33", and as we find that milk, when fresh, has an acidity of 20°, this corresponds to an increase of 13".We have tried to ascertain the amount of acid added to milk which will curdle it on boiling ; aqueous solutions of various acids were added little by little with constant shaking, till a faint coagulation on boiling was observed. Volume necessary expressed as & C.C. t o 100 C.C. The results were : Acid. Siilphuric ... ... ... ... ... 8.8 Hydrochloric ... ... ... ... ... 8.6 Oxalic ... ... ... ... ... . . . 29 and 28 Lactic ... ... *. . ... ... ... 9.7 We find that milk curdles at about 85", or an increase of 65", without boiling; this was the figure found at 17" to 35", and between these limits does not appear to vary appreciably; it is difficult to determine the point with accuracy.It is quite certain that the l1 acidity " of milk is not wholly due to lactic acid ; indeed, the (' acidity " of fresh milk is due to the niono- and di-basic phosphates, and not to free acid at all. Seeing that 9.7 C.C. TD lactic acid will curdle milk on boiling, while it requires a development OE about 13" " acidity," it is highly probable that another acid very much weaker than lactic is produced, and we venture to think that carbonic acid is responsible for a portion of the acidity of sour milk; we know that carbonic acid is produced, and we have found that when milk is sufficiently sour to develop gas about half the acidity, as indicated by phenolphthalein, is shown to litmus (to which both milk and carbonic acid are approximately neutral). We have based a hypothesis on the facts that different acids do not give the same result, that salts of polybasic acids are present in milk, that both casein and albumin have acidic functions, and that the coagulation of milk at temperatures between 17" and 35" does not appreciably vary with the temperature; it appears to us that curdling of milk is due to an amount of acid being present to set up an equilibrium between the acids and bases present, such that certain acids, e.g., casein and albumin, are liberated.At a boiling temperature we are inclined to think that the curdling is determined by the coagulation of the albumin, the equilibrium being destroyed by the removal of one acid (albumin) from solution, and fresh amounts of albumin, and finally perhaps casein, are liberated.122 THE ANALYST.When milk tastes sour, it would appear that the equilibrium is such that a sour-tasting free acid exists in solution ; while when milk curdles spontaneously the equilibrium is such that the insoluble acid casein is produced. We have mentioned this hypothesis to emphasize the fact that the point at which milk must be considered sour is a purely arbitrary one ; the three points we have mentioned are determined by the coagulation of albumin, the production of a sour-tasting acid, and the formation of insoluble casein respectively, and others could doubtless be found. We have made some experiments to determine the rate of souring of milks with and without preservatives. The preservatives used were a mixture of borax and boric acid, in the proportion of one part borax to three parts boric acid, from which sufficient water had been driven off to raise the percentage of B,O, to 56.3 per cent.(this is a mixture largely sold under fancy names), and a solution of formaldehyde. Our results are, with boric preservative (the figures represent degrees of acidity) : Temp. 17'5" C. Milk alone. 52 hours 69.9" 76 ,, 95.0" Temp. 24.5" C. 24 hours 32.6" 48 7 , 99.2" 22.5 hours 93.6" 46 I , 116.6" Temp. 34.5" C. The acidity of the milk when fresh was : Milk alone ... . . 1 ... ,, + 0.05 per cent. < . . ... 9, +0'10 J 9 ... ... With formaldehyde : Milk + 0.05 per Cent. 31-3" Milk + 0.10 per Cent. 35.3" 52.6" 67.3" 3 1 *3" 97.1" 35.0" 88.6" 71.3" 114.8" 45 *3" 108.2" 19.7" 25.3" 31.3" ... ... ... ... ... ... T ~ ~ ~ .17.50 c. Milk alone. Milk + 0.0023 per Cent. - 29.3" 99.2" Milk + 0.0047 per Cent. Milk + 0.0093 per Cent. 24 hours 48 9 9 72 $ 9 Temp. 27" C. 24 hours 22-9" 72.7" 93.6" 23.3" 33.3"" 22.0" 24.0" 58.7" 106.3" 118*0" 26.7" 115.3" 120.8" 23.3" 123.3" 81.30::: - 27.3" 56-7" 48 I 9 72 t 9 Temp. 3 3 C. 24 hours 83.3" 116.7" 158-3" 80-0" 141.6" 152.4" 28.0" 129.2" 139.2" 22.7" 52.0'" 132.0" 48 9 , 72 I , The acidity of the fresh milk was in all cases 20.7". In the samples marked with an asterisk we could only obtain a very slight All the samples with an acidity below We would draw attention to the fact that when a milk treated with formaldehyde formaldehyde rsaction with Hehner's tests. 30" gave a strong reaction, and the others a most indefinite one.THE ANALYST, 123 begins to develop acidity, the rate of souring is greater than that of untreated milk, and this is noticed also, to.a smaller extent, with boric preservative. By drawing a curve including the results at 17*5O, we get an expression of the rate of souring, and we find that the same curve with a different time factor applies without great error to the other temperatures, and to the results with boric preserva- tive ; a second slightly differing curve applies to the formaldehyde results. By means of these curves we have constructed tables of the time which milk takes to arrive at the three points of sourness "-i.e., an increase of 13", 25q and 65' acidity. These tables are, of course, only approximate, but we'do not think that the deviation exceeds 10 per certt.of the values stated. Table of the Time in, Hours taken by Milks to renclc 13" Additional Acidity. Boric Preservative. Formaldehyde. * 7- Temp.o F, M.Mb",. Milk + 0-05 Milk + 0.10 Milk + 0.0023 Milk + 0.0047 Milk + 0.0093 per Cent,. per Cent. per Cent. per Cent. per Cent. 60 42 71 93 51 85 119 70 29 36 46 34 49 78 80 19 22 31 25 34 56 90 13 15 23 15 26 44 100 7.5 10 20 9 23 37 Time in Hours to reach 25" Additional Acidity. Boric Preservative. Fcmaldehyde. h per Cent. per Cent. Temp. F. AliLta Milk -i 0.05 Milk + 0.10 60 50 84 110 70 34 43 54 80 22 26 36 90 15 18 27 100 9 12 23 7- Milk + 0.0023 per Cent. 60 40 29 18 11 - - \ Milk + 0.0047 Milk + 0.3093 per Cent. per Cent. 100 140 58 92 40 66 31 52 27 44 Time in Hours to reach 65' Additional Acidity. Boric Preservative. Formaldehyde./--- Milk Milk + 0.05 Milk + 0.10 Temp." F. alone. per Cent. per Cent. 60 75 126 I65 70 51 64 81 80 33 39 54 90 22 27 40 100 12.5 18 34 I-- Milk + 0.0023 per Cent. 84 56 41 25 15 -__/-- Milk + 0-0047 Milk f O*OO& per Cent. per Cent. 140 192 81 129 56 92 43 73 38 62 The only results we have been able to find which are comparable with ours are those of Rideal (loc. cit.). Applying the same methods to his results, we obtain practically the same figures as those given above."' We would draw attention to the fact that at high temperatures (say 80" hot summer weather) preservatives are comparatively useless unless added in relatively he has subtracted a constant amount for this throughout his series. * We assume that as Rideal does not notice the increased acidity when boric acid is added to milk,124 THE ANALYST.large quantities; the minimum quantities used by us, and also by Rideal, only increase the life of milk a few hours, and are equivalent only to a lowering of temperature of about 5" F. Unless milk can be made to keep at least twelve hours longer than without Preservatives, we do not think much is gained by their use, and to do this in summer we think that the minimum amounts are 0.09 per cent. boric preservative and 0.004 per cent. formaldehyde. We would also draw attention to the increased rate of souring as time goes on, when preservatives are added. This indicates a possible danger in using preserva- tives in milk, as it seems far from improbable that succeeding generations of micro- organisms become in the presence of preservatives more active and more virulent, and i€ the use of preservatives were universal, there is a probability that they would cease to act.The work of Effront on yeast grown in the presence of sodium fluoride shows that this view is not a mere hypothesis. DISCUSSION. The CHAIRMAN (Mr. ,411en) inquired whether there was any reason to suppose that milk contained carbonic acid or carbonates. If this were the case, the reliability of titrations with phenol-phthalein would be seriously affected. Mr. RICHMOND said that a portion of the acidity of sour milk was undoubtedly due to carbonic acid, and the question had been considered in connection with this paper. The figures, however, were not given as representing the acidity absolutely, but were only intended for comparative purposes. The question of carbonic acid would not affect the immediate object of the determinations, which was to ascertain the time required for the acidity to reach a certain point. If different samples contained different proportions of carbonic acid, there would, of course, be a distinct error; but these samples had been treated as nearly as possible under the same conditions, and the ratio of carbonic acid to other acids was probably not sufficiently divergent to affect the conclusions. Mr. CHAPMAN asked whether the experiments took place in the winter or summer months. The effect of a temperature of 80" F. in the summer and in the winter would probably not be the same. Mr. RICHMOND said that the experiments were conducted during the winter. If any difference occurred, it would be rather in the autumn months-September and October-when an increase in the rate of souring might be expected. He did not think there would be any increase in the summer.

ISSN:0003-2654    

DOI:10.1039/AN9002500116

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

THE ANALYST. 125 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. ORGANIC ANALYSIS. J. Wauters. Bull. dc Z'Ass. beZge, 1899, xiii., 404-416.)-From the results of his experiments on the detection of these oils in butter, lard and other oils, the author has arrived at the following conclusions : Halphen's reagent is preferable to Becchi's reagent for the detection of cotton- seed oil. I t does not produce any coloration with other oils or fats, and is capable of detecting 0.25 per cent. of cotton-seed oil in mixtures. The reaction, which is also given by old oils, gains in sensibility by decolorizing the fat by. heating it at about 50" C. with animal charcoal. Butter, both naturally and artificially coloured, and margarine are completely decolorized in this way. The fatty acids do not give the coloration after being dried at 100" C., but with the undried acids the reaction is obtained with even greater intensity than with the fat itself.Butters prepared from the milk of cows partially fed on cotton-seed cake give the reaction, but the intensity of the colour does not appear to exceed that produced by a fat containing 1 per cent. of the oil. On the other hand, feeding the cow with cotton-seed cake does not appear to have any influence on the chemical or physical constants of the butter. Decolorization by means of animal charcoal does not remove from sesame oil the active principle which gives the coloration in the Baudouin test. I t removes foreign colouring matters, however, and notably turmeric. By applying the test to the decolorized fat it is possible to detect as little as 0.25 per cent.of semme oil in butter or margarine. C. A. M The Detection of Cotton-seed and Sesame Oils in Fats. Notes on the Constitution of Train Oils. H. Bull. (Chem. Zcit., 1899, xxiii., 996.)-By suitable treatment with alkalies dissolved in absolute alcohoI, the fatty acids in train oils can be divided into four groups : (a) those whose potassium salts crystallize out of alcohol, ( b ) those whose sodium salts are crystallizable, (c) those whose sodium salts are very soluble in ether, and (d) a small residue. From 1 kilo. of Baltic cod oil the fractions were as follows : Weight in Grammes. Acid Number. Iodine Number. A ... ... ... 334 194.2 67.5 B ... ... ... 375 190 135.6 c ... ... ... 120 167 322-4 D ... ...... 69 169 347 A contains practically all the saturated acids and some belonging to the oleic series ; B contains acids of the oleic and linolic series ; C consists chiefly of acids of the126 THE ANALYST. formul% C,H,,-,02 and CnH2n-1002 (C,,H,,O, and ? C23H3602). For the latter an iodine value of 369 and an acid value of 165.2 were found, which agree satisfactorily with theory. An imperfect separation of the fatty acids of the original oil can also be attained by distilling them at 200" C. in a sharp current of steam heated to the same temperature, recovering the distillates by fractional condensation in a set of receivers maintained at 180°, 160°, 140", 120°, and 100". The same process may also be applied to the acids previously separated by crystallization ; fraction A above gave the following results : Temperature of Receiver.Weight of Fraction. Acid Number. Iodine Number. 160" 83.3 182 102.6 140" 95.5 200 62.4 120" 115.7 209 40 100" 14.2 212 33 Saturated acids were present in all fractions : stearic acid only in the first ; stearic acid with a little palmitic in the second; palmitic almost alone of the saturated acids in the third ; in the last palmitic and its lower homologues. The ordinary processes for separating fatty acids which depend on the use of lead are not suited for the investigation of train oils. I n all the samples examined, except torsk," erucic acid, C,,H,,O,, was met with, and also a new acid, C,,H3,02, melting about 20" - both of which (especially the former) yield lead salts slightly soluble in ether.I n liver oil a new acid of the oleic series containing 21 atoms of carbon was found, which melted at 24*5", and had the acid value 171.6 (theory, 172.8); this gave a lead salt very soluble in ether, and was therefore no mere mixture of the two former. I n herring oil two unsaturated liquid acids with melting- points below - 20" were discovered, which gave the annexed analytical results : Formula. Acid VaIue. Iodine Value. F. H. L. Estimation of Unsaturated Fatty Acids in Train Oils. H. Bull. (Clzenz. Zeit., 1899, xxiii., 1043.)-This process depends, as already mentioned (cj. pre- ceding abstract), on the solubility in ether of the sodium salts of the unsaturated acids of train oil. Seven grammes of the oil are weighed into a 200 C.C. flask, mixed with 25 C.C.of sodium ethylate (23 grammes of metal dissolved in 1 litre of absolute alcohol), and boiled on the water-bath for half an hour under an inverted condenser, shaking at intervals. The flask is closed and set aside for two hours; the soaps are thoroughly broken up with a rod, and 144.2 C.C. of ether free from alcohol and water (which has stood at least twenty-four hours over a large quantity of calcium chloride) is introduced, After agitating several times at intervals of half an hour, the mass is thrown on a dry 150 millimetre filter, the funnel of which is covered with a plate moistened with glycerin, and is connected by a rubber cork * A fish allied to the cod.THE ANALYST. 127 to the flask, a piece of string being inserted between paper and funnel to permit circulation of air.One hundred C.C. of the filtrate (equivalent to 4 grammes of oil) are removed and extracted three times with 20 C.C. of water, a little free alkali being added each time in presence of phenolphthalein to prevent dissociation of the soaps. Any emulsion is broken down by means of a trace of alcohol or a few drops of alcoholic potash. The fatty acids are then liberated from the soaps, and the unsaponifiable matter extracted. A very long table is appended giving the various constants of different varieties of train oil. Excepting the Japanese kinds, torsk oils, especially if pale, show a high proportion (12 to 21 per cent.) of unsaturated acids belonging to the series CnH2n- *O,. The whale oils of the Northern Seas contain much less (4 to 9 per cent.); the antarctic “ right ” whale oil gives 19-5 per cent.Sardine oils contain 14 to 26 per cent. A turbid Japanese sample, however, gave only 5.75 per cent. The figures yielded by American porpoise-jaw oil show that an almost saturated acid of low molecular weight in it has a soluble sodium salt. Treated similarly, linseed, olive and rape oil give 2.37, 1.32, and 1.35 per cent. of soluble sodium salts respec- tively. F. H. L. Estimation of Sugar in Transparent Soaps. F. &eyer. (Oesten.. Chenz. Zed., 1900, iii., 25.)-The expression “glycerin soap” is used in trade to designate all transparent soaps, whether they contain glycerin or not. Materials intended for exportation to hot climates are nearly always prepared with cane-sugar, instead of glycerin, as the former enables them to bear high temperatures without sweating ; and the proportion of sugar usually lies between 10 and 15 per cent.16.28 grammes (a quarter of the normal weight per 250 C.C. for the soleil-ventzke-scheibler polarimeter) are dissolved on the water-bath in 50 or 100 C.C. of water, and a small excess (about 40 c.c.) of 10 per cent. barium chloride solution is added. The mixture is brought into a graduated flask, and diluted to 260 c.c., allowing 10 C.C. for the volume of the precipitated soap. The filtrate is tested with Fehling’s solution for reducing sugars, polarized in the S-V-S instrument as it is, and polarized again after inversion with acid. F. H. L. - - - The Determination of Tannin aud Gallic Acid. F. Jean. (Rev. de Chim.Ind., 1900, xi., 35-38.)-This is an iodometric method based upon the fact that iodine combines with tannin or gallic acid to form compounds which do not give a blue coloration with starch. The iodine is dissolved in a solution of potassium iodide, and standardized on 0.1 per cent. solutions of tannin and gallic acid dried at 100” C. I n each case 20 C.C. of the 0.1 per cent. solution are mixed with 5 C.C. of a concentrated solution of sodium bicarbonate, and the iodine run in drop by drop with continual. circular agitation until a drop of the liquid gives a blue coloration when applied to paper covered with powdered starch. The iodine solution is then strengthened or diluted according to the results of the titration until 10 to 10-5 C.C. are equivalent to 10 C.C.of the tannin solution. Gallic acid requires about 3 C.C. more of the iodine solution than tannin.128 THE ANALYST. A blank determination is made to obtain the correction (usually about 0.4 c.c.) for the sodium bicarbonate. I n extracting the tannin substances from wood, leaves, etc., about 1 gramme of the sample is finely powdered, and heated for about thirty minutes with 15 C.C. of water at 50" C. The extract, is decanted, the residue boiled for ten minutes with a fresh portion of water, and the aqueous solution again decanted, this treatment being repeated until the total extracts amount to nearly 100 c.c., to which volume it is finally made up when cold. In the case of liquid extracts B solution is prepared containing 0.5 per cent. of the sample. Ten C.C.of the solution are titrated with the standard iodine solution in the manner described above, the titration being repeated until the amount corresponding with 10 C.C. of the iodine solution is found. From the result the total amount of astringent matter is calculated. This is prepared by triturating 2 grammes of dried egg albumin with sufficient glycerin (28-30" RB.) to form a thin paste, leaving this for thirty minutes, and then making up to a Iitre with tepid water. It is preserved by the addition of a few fragments of camphor and by closing the flask with cotton wool impregnated with formaldehyde. In the analysis 50 C.C. of the astringent solution are mixed with 15 C.C. of the albumin solution and 20 grammes of powdered sodium chloride, and the liquid made up to 100 C.C.with water, well shaken and filtered, the first portions being rejected. A quantity of the filtrate, double that required in the first titration, is rendered acid by the addition of one drop of acetic acid and boiled to coagulate the excess of albumin. The filtrate and washings from this precipitate are cooled, mixed with 5 C.C. of sodium bicarbonate, and titrated with the standard iodine solution, a correction (usually about 0.7 c.c.) being made for the albumin from the result of a blank titration. The amount of gallic acid is calculated from the iodine consumed, and the tannin is obtained from the difference in the results of the two titrations. When the tannin material contains amylaceous substances soluble in water, the extraction should be made with alcohol, I n the case of liquid extracts the absence of sulphites should be ascertained. For the separation of the tannin a solution of albumin is employed. C.A. M. - ~ ~ ~ Detection of Nicotine. J. Schindelmeiser. (Pharm. C. H., 1899, sl., 703 ; through Chem. Zeit. Rep., 1899, 361.)-If unresinified nicotine is mixed with a drop of 30 per cent. formaldehyde, and a drop of strong sulphuric acid is added, an intense rose-red colour is produced, which becomes dark red in the presence of 0.005,or 0.01 gramme of the alkaloid. Concentrated formic acid may equally replace the formalin. F. H. L. The Determination of Phosphorus in Organic Compounds. C. Marie. (BUZZ. SOC. Chim., 1900, xxiii., 44, 45.)-One gramme of the substance is dissolved in 15 to 20 C.C. of concentrated nitric acid, the liquid gently heated, and finely divided potassium permanganate added in successive small portions until the colour of the solution remains pink for some minutes after the last addition.I n the case of com-THE ANALYST. 129 pounds of the fatty acid series the destruction of the organic matter is very rapid; but with aromatic compounds it is more tedious, and it is necessary to add the per- manganate in very small portions at a time, and to wait until the reaction is completed before adding the next portion. A 10 per cent. solution of an alkali nitrite is added drop by drop to the oxidized liquid when cold until it becomes quite clear. It is then boiled for some time to expel the nitrous gases and to concentrate the solution, and the phosphoric acid precipitated in the usual manner with molybdate solution, care being taken to wash the precipitate completely free from manganese.The author has tested this method on a large number of compounds, including some which, like Baeyer's ammonium calcium aceto-diphosphite, are extremely difficult to oxidize, even with fuming nitric acid in a sealed tube at 200" C., and has obtained results absolutely identical with those yielded by the ordinary method. By the use of this method the analysis of glycero-phosphates may be greatly simplified. C. A. M. A Simple Method of Estimating Mercury in Urine. Schumacher and W. 2. Jung. (Zeit. anal. Chem., 1900, xxxix., 12-17.)-A litre of the urine under examination is mixed with 15 to 20 grammes of potassium chlorate and about 100 C.C.of concentrated hydrochloric acid, and heated in a 2-litre flask on the water-bath until chlorine commences to be evolved. The flask is then allowed to stand for twelve hours. After expelling the excess of chlorine by gentle heating, the mercury is precipitated by the addition of 100 C.C. of a clear solution of stannous chloride, and the liquid filtered through purified asbestos. The precipitate, which contains a little organic matter, is washed by means of water and potassium hydroxide solution into a 300 C.C. flask, and gently heated so as to dissolve the organic matter ; the solution is again treated with potassium chlorate and hydrochloric acid. After filtration, the solution, while still warm, is treated with 10 to 20 C.C. of a concentrated solution of stannous chloride, and filtered through a Soxhlet-tube con- taining a layer of asbestos, and above it asbestos impregnated with metallic gold, which retains the mercury.The asbestos is washed with dilute hydrochloric acid and water, then with alcohol and with ether, and the tube dried to constant weight in a current of dry air. The mercury is then expelled from the asbestos by heating the tube strongly and conductinga current of air through it until the weight again becomes constant. The difference between the two weights gives the amount of mercury. The gold asbestos is prepared by dissolving pure gold in aqua regia, and evaporating the solution until nearly the whole of the free acid has been expelled. Fine threads of purified asbestos are soaked in this solution, and, after the liquid has drained off, heated in a porcelain crucible in a current of hydrogen for about fifteen minutes, when the reduction will be complete. Finally, the asbestos is washed with dilute hydrochloric acid and hot water, and dried. I n illustration of the accuracy of the method, the authors quote the following analyses among others : To a litre of pathological urine, which, according to the mean results of numerous analyses, contained 20 decimilligrammes of mercury, 30, 40.5,130 THE ANALYST. and 67 decimilligrammes were added, and the amounts respectively found were 60, 55, and 77.5 decimilligrammes. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9002500125

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

130 THE ANALYST. I N O R G A N I C A N A L Y S I S . The Analysis of Tungsten Compounds. F. Ibbotson and H. Brearley. (ChemicaZ Nezos, vol. lxxx., pp. 293, 294.)-On adding strong nitric acid, drop by drop, to a boiling solution of lead tungstate until the colour begins to turn yellow, then running in a few C.C. of the acid, and boiling a short time, aprecipitate of tungstic acid is obtained corresponding in weight with the known quantity present. As, how- ever, from 2 to 3 milligrammes of tungstic acid are found in the filtrate, the accuracy of the method depends on small compensatory errors. The colour change not being developed in presence of ammonium salts, the latter must be previously eliminated with caustic alkali. Again, the acid lead tungstate thrown down by lead acetate from fainbly (acetic) acid solutions can be dissolved in warm concentrated hydrochloric acid, and tungstic acid completely precipitated therefrom by the addition of water.No interference in this precipitation is exercised by barium, strontium, calcium, magnesium, zinc, cadmium, manganese, nickel or cobalt. In the case of arsenic, a few grammes of ammonium nitrate are added before precipitating the tungsten ; any lead arsenate thrown down is redissolved in the hydrochloric acid, and may be disregarded, as may be also the precipitate formed with tungstates by mercury. Uranium forms insoluble tungstates, which can be dissolved in a slight excess of sodium carbonate, and the clear solution should be heated to near the boiling-point and then poured into 6 or 7 C.C. of hot acetic acid, with an excess of lead acetate, the whole being well shaken. After just boiling the mixture the precipitate is washed by decantation, etc., and will then be free from uranium.To remove it the mixture is rendered faintly alkaline and then slightly acidified with acetic acid, the bulky precipitate furnished by lead acetate being washed thoroughly by decantation, ignited, and treated with hydrochloric acid as though it were pure lead tungstate. Small quantities of aluminium can be similarly dealt with. Tin and silicoiz prevent the accurate precipitation of tungsten by this method, the former producing compounds insoluble in hydrochloric acid, whilst the silico- tungsten compounds are imperfectly thrown down by lead salts. They may, how- ever, be precipitated by mercurous nitrate, from a neutral solution, the silica being Iron comes down with the lead tungstate precipitate.removed by hydrofluoric acid after igniting the residue. c. s. A New Method of Separating the Gadolinite Earths, and of Obtaining Pure Yttria. (Berichte, 1900, xxxiii., 42-49.)-This is based on the fact that the normal chromates of the rare earths are considerably more insoluble than the corresponding sulphates. On precipitating a dilute neutral solu- tion of the salts of the cerite or gadolinite earths with potassium chromate, the precipitates, when crystalline, have a composition corresponding to the general W. Muthmann and R. Bohm.THE ANALYST. 131 formula R,(CrO,), + mH,O. The amount of water varies with the temperature and the metal, but most of these chromates crystallize with 8 molecules.The authors have found that the most rapid method of fractionally precipitating these rare earths is to treat their readily soluble dichromates with potassium chromate. For the separation of the commercial yttria material into its six or more components they have proved that the following precautions are necessary : 1. The solutions of the rare earth salts and of potassium chromate must both be very dilute. 2. The liquid must be kept boiling throughout the precipitation. 3. The resulting precipitates must be kept in a fine state of division, and brought into intimate contact with the liquid. In carrying out these conditions they heat the liquid to be precipitated in a, large retort nearly to the boiling-point, and then conduct a current of steam into it, the neck of the flask being slanted upwards to avoid loss by spurting.Besides the steam tube a second tube provided with a tap passes through the tubulure of the retort, and is connected by means of a siphon arrangement with the potassium chromate solution which is contained in a graduated flask. As each drop falls from the tube the resulting precipitate is distributed throughout the rapidly-boiling liquid. After the precipitation of each fraction the liquid is evaporated to its original volume, so that the conditions are the same throughout. The following experiment is described to illustrate the method : The mixture of earths used was bought as 6 ‘ Yttrium oxydat. pur.,” but in reality was found by spectrum analysis to contain oxides of most of the other rare earths.Forty grammes of this were triturated with about 90 grammes of chromium trioxide, and the mixture treated with a litre of water. The resulting solution of the dichromates was treated with potassium chromate until a turbidity resulted, and was then transferred to the retort and precipitated into six fractions as described above. Fraction I. precipitated in two hours by 250 C.C. of 10 per cent. potassium chromate solution yielded only 1.1 gramme of oxides owing to the solution still containing polychromates. The oxides contained about 25 per cent. of erbian earths. Fructioiz II(a). obtained in the same manner yielded 13.6 grammes of the oxides, of which about 20 per cent. were erbian earths.The spectrum showed that there was a considerable increase in the proportion of gado- linium as compared with the original substance. Fraction II(b). was deposited on evaporating the mother liquid to the original volume. I t yielded 6.04 grammes of oxides containing about the same amount of erbian earths as Fraction II(a). F?*actioiz III. was precipitated with 300 C.C. of 5 per cent. potassium chromate solution and yielded 7.04 grammes of oxides, of which about 10 per cent. consisted of erbian earths. Fractiorz IV., obtained in the same manner as III,, yielded 5-35 grammes of oxides containing only about 5 per cent. of erbian earths. On concentrating the liquid the chromate of a lighter earth was deposited. The oxide (2.065 grammes) was almost pure white, and showed only traces of erbium.132 THE ANALYST. F r a c t i o n V .consisted of chromate of yttrium and yielded nearly pure yttria F r a c t i o n VI. gave 1.5 grammes of oxide, which was also practically pure yttria. The residual solution, from which nothing more could be precipitated by potas- sium chromate, yielded on treatment with sodium hydroxide a slimy precipitate consisting of magnesia, calcium hydroxide, silica, and traces of yttria. (4.2 grammes). C. A. 11. Estimation of Calcium Carbonate in Soil. Immendorffs Process for the Determination of Total Calcium. H. Schutte. (Zeit. angezo. Chem., 1899,854.)- The process already described by Stutzer and Hartleb (ANALYST, xxiv., 275) for esti- mating the proportion of calcium and magnesium carbonates, as distinguished from ferrous carbonate, in soil, yields perfectly accurate results when it is carried out on the pure carbonates of the alkaline earths ; but when it is applied to natural soils, especially such as are poor in chalk, it leads to quite erroneous conclusions.I n the first place, zeolites are present in larger or smaller quantities in most soils, and silicates of this nature react with the ammonium chloride, liberating ammonia, which neutralizes part of the standard acid placed in the receiver of the apparatus. The influence of such easily decomposed silicates is shown by the fact that if a soil giving only a slightly higher proportion of ‘‘ carbonates ” by distillation than by direct estimation of the carbon dioxide is repeatedly extracted with water saturated with carbon dioxide so as to dissolve and remove part of the true calcium carbonate, and is then again tested by the two processes, the difference between the yields is con- siderably increased.Secondly, Stutzer and Hartleb have stated that ferrous car- bonate can be wholly decomposed by boiling the earth with water alone before the distillation is begun; this is quite true of fresh artificially precipitated ferrous carbonate, but the natural substance is far more stable, and, indeed, it can neither be broken up entirely in the manner indicated, nor correctly estimated by the authors’ method. Moreover, the process does not give even concordant results when it is conducted according to the directions already specified; it is necessary to distil the liquid almost to dryness to ensure complete decomposition of the carbonates, or to use a larger excess of ammonium chloride; it is perhaps better to start with 25 C.C.of a 25 per cent. solution of chloride and 200 C.C. of water, distilling until only 25 C.C. of liquid are left in the retort, i.e., till the residual liquid has again a con- centration of 25 per cent. Nevertheless, in the case of soils rich in alkaline earth carbonates, but free from ferrous carbonate, the method should prove of some value, for the errors are then relatively insignificant ; but when the carbonates form but a small percentage of the total material it is no longer of service. For instance, a sample of marl containing 36-97 per cent. of carbon dioxide or 84-02 per cent. of calcium carbonate by gravi- metric analysis gave 37.56 per cent.or 85.36 per cent. respectively on distillation ; whereas a mud with 0-05 per cent. of carbon dioxide or 0.11 per cent. of calcium carbonate gravimetrically, was represented to contain 0.16 per cent. or 0.36 per cent. respectively by the Stutzer and Hartleb process.TEE ANALYST. 133 To assume that the question whether a soil would be improved by the addition of chalk can be answered simply by noting the proportion of calcium carbonate already in it is not universally correct ; earths rich in humus occasionally contain no calcium carbonate, yet they are not improved by introducing chalk. I n many cases, therefore, it is desirable to estimate the total calcium, which is best done by Immendorff's process. The sample is extracted with hot hydrochloric acid, a, portion of the solution is rendered just alkaline with ammonia, warmed and clarified by the cautious addition of more acid, then brought to the boil.A large excess of a strong solution of ammonium oxalate is next introduced, and after boiling some time the whole is made alkaline with ammonia, and faintly acid with acetic acid. The calcium oxalate can then be titrated, but it is preferably (if the soil contains much iron) ignited and weighed, Manganese in the precipitate is thus shown by the dark colour, and can be removed by a second precipitation, or by the use of bromine as usual. If the operation is properly conducted, iron and aluminium never contaminate the calcium oxalate. Passon's method for the estimation of calcium (Zeit. mzgezc.Chem., 1898, 776) is more troublesome to use, and does not give more accurate figures than that just outlined. F. H. L. Separation of Chlorine and Iodine. L. Vanino and 0. Hauser. (Bpichte, 1900, xxxii., 3615-3617.)-This method is based on the behaviour of these halogens towards an alkaline solution of formaldehyde, the chloride being rapidly reduced to metallic silver whilst the iodide is not attacked. The solution containing the mixed salts is precipitated with silver nitrate and the precipitate washed as far as possible by decantation, the washings being passed through a filter. It is then treated in the beaker with 25 C.C. of a solution of 50 grammes of potassium carbonate in 100 C.C. of water and 5 C.C. of a 42 per cent. solution of formaldehyde, and allowed to stand until carbon dioxide ceases to be evolved.Initial heating to 30" or 40" C. accelerates the reaction, which is usually complete in about thirty minutes. Any particles of chloride on the filter are also reduced to silver by repeated washing from a jet with the reagent previously heated to 40" C. The precipitate in the beaker is washed with hot water, as far as possible by decantation, and after being treated with hot dilute nitric acid the liquid is repeatedly filtered through the same paper as used before, until the filtrate is perfectly clear. The silver iodide left upon the filter is washed, dried, ignited in a porcelain crucible and weighed. The silver in the filtrate is precipitated with hydrochloric acid, and from the weight of silver chloride obtained the amount of the chlorine originally present can be calculated.The results obtained in test experiments are given in tabular form, and show a, close agreement with the theoretical quantities. This method cannot be used for the separation of bromine from chlorine or from134 THE ANALYST. iodine, since silver varying conditions, bromide is more or less reduced by the author’s reagent under though not completely reduced like silver chloride. C. A. M. A New Reaction for the Detection and Estimation of Nitrous Acid. H. Erdmann. (Berichte, 1900, xxxiii., 210-215.)-1n the author’s opinion the methods used for the detection of nitrites in water leave much to be desired. He states that in his experience well and surface water in which the nitrites correspond in quantity to a I n exceptional cases the bacterial production of nitrites in natural water may reach a concentration corresponding to a ilm X solution.When the amount of nitrite nitrogen does not amount to 1 centigramme in a cubic metre of water, he considers that it may be ignored, but that when it amounts to from I centigramme to I gramme per cubic metre an, at least, approximate estimation is necessary in order to form a correct judgment of the character of the water. If the nitrous acid in the water can be quantitatively converted into a coloured azo compound, it should be possible t o make a colorimetric estimation. Metaphenylene- diamine, and similar substances, however, cannot be used for this purpose, since the brown colorations obtained are not sufficiently characteristic ; and, on the other hand, they also give somewhat similar colorations with oxidizing agents.After numerous experiments, the author has finally fixed upon 1-8-amido- naphthol 4-6-disulphonic acid as the most suitable substance. This is prepared from 1 -3-5-naph thalene- sulphonic acid (Re2-k Izte, xxxi i. , 3 186) by nitration, reduction, and heating with sodium hydroxide. It has the property of combining in acid solu- tion with diazo compounds to form mono-azo colouring matters which are readily soluble and have a characteristic tint. I n using the reagent, 50 C.C. of the water are treated with 5 C.C. of a hydrochloric acid solution of sulphanilic acid (2 grammes of sodium sulphanilate per litre), and after about ten minutes about 0.5 gramme of l-amido-8-naphthol-4-6-disulphonic acid in the solid state is introduced.I n the presence of nitrous acid a brilliant Bordeaux red colour is produced, and reaches its maximum intensity in about an hour. For a quantitative estimation, the colour is compared after that lapse of time with that given by standard solutions under the same conditions. The solutions used are N, and should be freshly prepared in order to avoid bacterial alteration. As a proof of the superiority of this test over bacteriological methods, the author cites a case in which a well-water, which had given rise to an epidemic of anthrax, gave a pronounced nitrite reaction after a year, although the bacteria had long dis- appeared. He points out that it is seldom possible to actually isolate anaerobic pathogenic bacteria on account of their short life.As regards other tests for nitrites, that of Griess with a-naphthylamine (Berichte, xii., 427) is said to be not sufficiently sharp or characteristic for water analysis, and to be unsuitable for a colorimetric estimation. Still less satisfactory is Risgler’s reagent, naphthionic acid (ANALYST, xxii., 305), N solution contain large numbers of bacteria. N, iv+aGc N andTHE ANALYST. 135 since, as is the case with many other readily diazotized bodies, its fluorescence interferes with the comparison. The author’s reagent is stated not to fluoresce under the conditions given above. With oxidizing agents, such as ferric chloride, it gives a yellow coloration, which cannot possibly be confused with the red colour obtained with nitrites.The author has made arrangements with J. F. Schwarzlose Sohne (Berlin, S.W., Markgrafenstr. 29) to forward specimens of his new reagent gratis on application. C. A. M. The Estimation of Sulphydric, Sulphurous, and Thiosulphuric Acids. W. Feld. (Chew,. News, Ixxxi. , 40.)-The methods recommended by the author are applicable to the salts of the alkalies and of the alkaline earths. For suiphides the sample is boiled with a concentrated solution of magnesium chloride in an atmosphere of carbonic acid, when (assuming barium sulphide) the following reaction takes place : B a s + MgCl, + CO, + H20 = BaCl, + MgCO, + H2S. The sulphuretted hydrogen evolved is absorbed in a solution of iodine, which is after- wards titrated.For sulphites the same procedure is adopted, but substituting hydrochloric acid for magnesium chloride. Thiosdphate is first converted into tetrathionate by titration with iodine. The solution is then subjected to the action of aluminium and dilute hydrochloric acid in an atmosphere of carbonic acid, when the following reaction takes place : Na,S,O, + 20HC1+ 6A1= 2NaC1+ 3A12C1, + 6H,O + 4H,S. This method is also applicable for the determination of thiosulphate in the presence of sulphite which becomes oxidized to sulphate. For the determination of sulphite in the presence of thiosulphate, the latter is first decomposed by the addition of mercuric chloride, thus : The process recommended for sulphites is then applied. In the case of mixtures of sulphide, sulphite, and thiosulphate, the sulphide is first determined by the magnesium chloride method, after which the thiosulphate is decomposed by mercuric chloride, and the sulphite determined by boiling with hydro- chloric acid.The thiosulphate is determined in a fresh portion by titration with iodine and treatment with aluminium and dilute hydrochloric acid. Na,S20, + HgCI, + H,O = Na2S0, + HgS + 2HC1. H. H. B. S. Determination of Nitrogen in Fertilizers containing Nitrates. F. P. Veitch. (JozLrn. Amer. Chent. SOC., vol. xxi., p. 1094.)-The author modifies Field’s variation of the Gunning method, in which potassium sulphide alone is used in place of potassium sulphate and sodium thiosulphate (ANALYST, xxii., 166), by adding to the nitrate in the digestion flask 35 to 40 C.C.of sulphuric acid, containing 34 gramroes of salicylic acid per litre, the whole being allowed to stand in the cold until the nitrate is dissolved, whereupon 6 or 7 grammes of powdered potassium sulphide is136 added, and gentle heat is the full flame till clear. Valuation of Alkali THE ANALYST. applied for a quarter of an hour, followed by heating over c. s. Persulphates and of Hydrogen Peroxide. B. Grutzner. (Arch. Pharm., 1899, ccxxxvii., 705 ; through Chem. Zed. Rep., 1900, 21.)-About 0.3 gramme of an alkali-metal persulphate is gradually warmed to the boiling-point with 50 C.C. of decinormal arsenious acid and a few C.C. of potassium hydroxide solution, and kept hot for a short time. When cold, the liquid is faintly acidified with sulphuric acid, a large excess of sodium bicarbonate is added, and the whole is titrated with iodine and starch.One C.C. of decinormal arsenic is equal to 0.0119 gramme of sodium persulphate. Hydrogen peroxide can be similarly treated, 1 C.C. of acid being equivalent to 0.0017 gramme of H,O,. F. H. L. Valuation of Clays for Brick Manufacture. W. Cronquist. (Oesterr. Zeits. Berg. u. Huttenw., 1899, xlvii., 522, nach Teknisk Tidsskrift; through Ghem. Zeit. Rep., 1899, 322.)-A mere chemical analysis of a clay is not sufficient alone to indicate its value to the brick-manufacturer ; the proportion of silica in an air-dried aluminium silicate may range between 37 and 45 per cent., but a determination of this ingredient is practically useless. The amount of sand in Swedish clays varies from 47 to 72 per cent., but all are employed for making bricks ; this sand, however, should be investi- gated for foreign matter, since the presence of mica, for instance, weakens the bricks.The air-dried sample is boiled with 1.12 hydrochloric acid till the residue is white; it is then filtered off and treated in a silver crucible with sodium carbonate solution to dissolve gelatinous silica, and the final insoluble sand is washed, ignited, and weighed. The author suggests two physical tests. A thoroughly representative sample is kneaded with water, and pressed into a wooden mould to yield EL plate 20 x 4 x 1 centimetres in size, on which a line exactly 150 millimetres long is drawn. After drying, the line is observed to find the distortion and contraction ; a shrinkage of 8 per cent.indicates a well-binding clay. To ascertain the strength of the material, a crucible 45 millimetres high and 2.5 millimetres thick in the walls is constructed with suitable moulds; this is dried for four or six days in the air, then for two days at 100" C. I t is next placed in an oven with similar crucibles made from standard clays, and burnt as usual. Finally it is broken in a specially-designed apparatus by means of lead shot;. F. H. L. A New Method of Titrating Potassium Iodide. E. Vincent. (Jou~n. Pharm. Chim., 1899, x., 481-483.)-This is based upon the well-known fact that iodic acid acts upon the iodide in accordance with the equation : One gramme of the iodide under examination is dissolved in a litre of water, and 100 C.C. of the solution mixed with the same quantity of a solution of iodic acid (2 grarnmes per litre).Five to ten C.C. of a standardized solution of thiosulphate, containing 2-48 grammes of thiosulphate in 100 C.C. and potassium bicarbonate in the pro- 6HI0, + 5KI = 5KI0, + 31, + 3I3,O.THE ANALYST. 137 portion of 2 grammes per litre, are measured into a beaker, and the mixed solutions of iodide and iodic acid run in from a burette drop by drop until the liquid asmrnes a faint yellow tint. Five-sixths of the iodine found are derived from the iodide originally present. The potassium bicarbonate is added to the thiosulphate with the object of preventing the oxidation of the latter by the excess of iodic acid. The following results were obtained by this method and by the more compli- cated method of FaliBres, in which the iodine is liberated by ferric chloride : Faliires' Method. Iodic Acid Nethod.Per Cent. Per Cent. I. ... ... ... 96 95-87 rr. ... ... ... 97.2 97 111. ... ... ... 94.5 94-4 I t is essential that the thiosulphate solution should be titrated with the iodine solution, and not vice versd. C. A. M. On the Use of Iceland Spar as a Standard in Volumetric Analysis- 0. Masson. (Clwcmical News, vol. Ixxxi., pp. 73-'75.)-Compact fragments weighing about 1 to 3 gramrnes each should be broken from a crystal of the spar, then freed from powder by rinsing with dilute acid, washed with distilled water, dried at over 100" C., and stored in a stoppered bottle. For use, about 2.5 to 3-5 grammes are weighed in an 80 to 100 C.C. beaker, the total weight alone being required, and exactly 20 C.C. of approximately normal hydro- chloric acid are run in from a burette, the beaker being covered and precautions taken to prevent loss by spurting. After three to four hours the evolution of gas will have ceased, and the contents of the beaker are kept at about boiling temperature for an hour, to drive off dissolved carbon dioxide and complete the reaction. The clear solution is then decanted, and the residual lumps of spar are well washed, dried at about 110" C., cooled and weighed. The loss in weight gives the amount of spar dissolved by, and exactly equivalent to, the 20 C.C. of hydrochloric acid taken; and also furnishes direct the '' factor" of the acid, since, the molecular weight of calcium carbonate being 100, 20 C.C. of strictly normal acid dissolve exactly 1 gramme. The author discusses several possible sources of error, but regards them all as negligible. c. s.

ISSN:0003-2654    

DOI:10.1039/AN9002500130

出版商:RSC    

年代:1900

数据来源: RSC

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THE ANALYST. 137 APPARATUS. R. Scholl. (Chem. Zeit., 1900, xxiv., 15.)-This consists of a rubber cap or plate with a central hole or short flexible sleeve to admit the pestle-stem, and a flange to fit air-tight round the upper edge of the mortar. The flange is made of considerable width, so that the cover is raised somewhat above the top of the mortar, thus leaving more space for the movements of the pestle. The cover is equally useful in grinding hygroscopic materials, or such as are brittle or possess an unpleasant odour. A Mortar Cover for Use in Grinding Hygroscopic Substances. F. H. L.138 TEE ANALYST. A Simple Bunsen Burner. F. Allihn. (Chem. Zeit., 1899, xxiii., 996.)-In this apparatus the usual injector gas- jet attached to the base and the radial air-holes surrounding it are done away with, so as to gain simplicity and cheapness in construction.The burner consists essentially of a plain T-piece, open at all three ends. At the spot where the horizontal (gas inlet) tube joins the vertical, the wall of the latter is drilled centrally with a small hole pointing upwards towards the end where combustion takes place; and this hole being the substitute for the ordinary jet, the bore of the vertical pipe is clear throughout, so that if liquids, etc., are spilt over the burner no choking can ensue. The bottom of the upright is provided with a male thread, which screws into a cast-iron base; and the air thus enters from under- neath the stand. This latter should manifestly be cast with a milled or fluted bearing edge, or on a level table the supply of air might be insufficient. The burner can be used equally well without the base, being supported by any convenient clamp. The apparatus is patented, and may be obtained from Warmbrunn, Quilitz and Co., Berlic. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN9002500137

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

138 TEE ANALYST. R E V I E W S . LEXIKON DEB KOHLENSTOFF-VERBINDUNGEN. By M. M. RICHTER. London : Williams and Norgate. Pp. 2482. (Published in thirty-nine parts, at 1s. 10d. each.) This work is the second edition of the “ Tabellen der Kohlenstoff-Verbindungen nach deren empirischen Zusammensetzung geordnet ,” which appeared in 1883. I t contains a register of about 67,000 compounds. Taking into account the fact that organic chemistry is a highly systematized branch of the science, the indexing of compounds by their empirical formulae appears at first sight a retrograde step. However, that the expedient has gone far towards meeting the demands for a, scheme of registering organic compounds is plain from the fact that the Executive of the German Chemical Society now publishes an index based on this system in addition to the ordinary annual index to the well- known “ Berichte.” A few considerations will, indeed, show that, judged on its merits, the system is the best yet proposed in many respects.Thus, even if chemists had universally agreed upon the best nomenclature for organic com- pounds, which is by no means the case, it must be admitted that the names denoting the constitution of chemical compounds are not in themselves well adapted to indexing purposes. They are extremely long, besides which opinions are constantly altering with regard to the constitution to be assigned to a given com- pound : moreover, there are the so-called tautomeric compounds to which definite constitutions cannot be assigned (Cf. Jacobsen and Stelzner, Bey., 1898, 31, 3368).The best established property of a compound, and at the same time the one least liable to alterations, is therefore its composition which finds expression in its empirical formula.THE ANALYST. 139 In the system under consideration the compounds are arranged in an ascending series depending on the number of carbon atoms they contain ; the elements other than carbon follow in an order which may be denoted the alphabet of the system, thus -H, 0, N, C1, Br, I, F, S, P. The remaining elements come after these in the alpha- betical order of their symbols. The work includes an index of names which gives the corresponding empirical formulz. The (‘ Lexikon ” forms a collective index to Beilstein’s well-known ‘( Handbuch der Organischen Chemie,” the third edition of which has just been completed, and as such, references are given to the latter for all the compounds-about 57,000-therein dealt with.As, however, the ‘‘ Lexikon ” is of later date than the last edition of Beilstein, about 8,000 more compounds are referred to in the former than in the latter. In the case of very well-known com- pounds, besides giving the reference to Beilsteia, the words ‘ I literature abundant ” are added, whilst in other cases references are to be found to the principal papers dealing with the compounds in question. I t is a very common occurrence in researches in organic chemistry that in the case of certain compounds nothing beyond the composition, i.e., the empirical formula, is determined. Under no other system of indexing but Richter’s can these substances be registered, and consequently hitherto their record has been as good as lost.A. R. L. SQUIRE’S COMPANION TO THE BRITISH PHBRMACOP~IA. Seventeenth Edition. London : J. and A. Churchill. This work, which has attained a large circulation amongst pharmacists, is not so well known to analysts as it should be. Although the number of examinations of drugs and their preparations made under the Food and Drugs Acts is at present small and inadequate, there is every sign that it will be increased in the near future. This being so, it behoves analysts to make a, fuller study of drugs than many of them have had occasion to do in the past, and there is no work more suited to their requirements than the one under consideration. Although this work is primarily designed for pharmacists, it contains much information of value to analysts. Thus, the normal amounts of ash are given in the case of a large number of substances ; comments on official processes, with suggestions or amendments of a practical nature, are included.To cite two instances, we may take the remarks on the analysis of pepsin and the examination of malt extracts. The table in the beginning of the book dealing with the materia medica of the Pharmacopeia is of high merit, and probably the most accurate published. A prolonged study of the work serves to increase one’s appreciation of the infinite care expended on the collection and presentation of the vast array of facts that have been accumulated. On examining the information given below the official tests in each monograph, we find either abstracts or references to almost every recent research of importance, so that the analyst may feel confident of getting assistance in the case of nearly every drug that may come into his hands.Smong the many valuable pieces of information, only two have been found that seem questionable-namely, the statements that Price 12s. 6d. The writer has noticed but one misprint in the book OE 850 pages.140 THE ANALYST. ‘‘ nutmegs yield about 5 per cent. of ash ”; and, secondly (although this is not a state- ment of the author’s), that the difference in the petroleum spirit extracts of true and false pareira is so marked as is indicated by the difference between the figures 8 and 0.3 per cent. Analysts will find the latest edition of this work a valuable acquisition.C. G. 31. BAYLEY’S CHEMISTS’ POCKET-BOOK. Seventh Edition. London : E. and F. N. Spon Price 5s. The author states that this seventh edition of his well-known Pocket-Book has been rearranged and to a Iarge extent rewritten. The book contains various numerical tables for rapid calculations, which are useful to all technical workers, whether chemists or not. The more strictly chemical part includes tables of the principal properties of the elements, various analytical factors, and tables of weights and measures, with means for translating one kind into another. We would suggest the addition of a selection of the heats of combination most frequently needed in practical calculations. Tables of specific gravity of solutions and of sundry salts are given, and are certainly acceptable, as are also records of the melting and boiling points and solubility of a number of substances, and the tables of the behaviour of salts with different indicators. Altogether, there is a great mass of matter clearly arranged and readily accessible. The fact that the book has been long before a critical public and has been received with favour implies that the data contained in it are sub- stantially accurate. Its use may save many a search in bulkier tomes. B. B.

ISSN:0003-2654    

DOI:10.1039/AN9002500138

出版商:RSC    

年代:1900

数据来源: RSC

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140 THE ANALYST. MILK STANDARDS. The following letter has been received from Dr. Thorpe by Mr. P. A. E. Richards, Public Analyst for St. Martin’s-in-the-Fields : Government Laboratory, Clement’s Passage, London. Kovember 2, 1899. DEAR MR. RICHARDS, I n the early days of the working of the Food and Drugs Act, when it was necessary to have regard to the character of much of the milk supplied, which, although genuine, was, as regards its fat, of no very high quality, the “ standard ” was fixed at 2.5 per cent. of fat. By the operation of the Food and Drugs Act, and the weeding out of certain classes of cows, there has been a gradual improvement in the general character of the milk-supply of the country, as was shown by the investigation undertaken by Dr. Bell shortly bcfore his resignation, and published as a Local Government Board paper.As a result of this inquiry, I raised the standard of fat in 1894 to 2.75 per cent. The causes above alluded to have continued to operate, as shown by the evidence taken by the Committee which more recently reported on the working of the Food and Drugs Act. In consequence of this, and in view of the fact that under Section 4 of the new Act, which comes into force on January 1, 1900, apresumption. of non-genuineness may be raised by the analyst should the amount of fat fall below a certain figure, whereas the onus of proof of the genuineness will fall upon the seller, I have felt justified in raising the limit to 3 per cent., and, as you may have noticed, this number has been given in recent certificates. This limit is, however, not to be held to anticipate or prejudge in any way the regulations as to standards which the Board of Agriculture may issue under the section of the Act referred to. Yours very truly, (Signed) T. E. THORPE.

ISSN:0003-2654    

DOI:10.1039/AN9002500140

出版商:RSC    

年代:1900

数据来源: RSC