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JULY, 1808. Vol. XXXIII,, No. 388. COMMERCIAL ANALYSIS OF FERROCYANIDES. BY HAROLD G. COLMAN, PH.D., M. Sc., F.I.C. (Read at the Meeting, May 6 , 1908.) UNTIL about twenty years ago the only soluble ferrocyanide produced on a com- mercial scale was the potassium salt, obtained by the old method of fusing potash with iron and organic nitrogenous matter ; and for the analysis of this salt the method originally proposed by De Haen (Annulen, 1854, 90, 160) was usually employed, namely, titration with standard potassium permanganate, whereby it is oxidised to ferricyanide. Since about 1890, however, owing to the demands for cyanide for the McArthur-Forrest gold-extraction process, other soluble ferrocyanides, especially those of sodium, and to a, smaller extent calcium, have been manufactured, a large proportion262 THE ANALYST.of these being obtained as by-products in the coal-gas industry from the hydrocyanic acid present in crude coal-gas. The use of permanganate for the determination of ferrocyanide in the crude products thus obtained is quite inadmissible, inasmuch as they contain other substances acted on by permanganate, especially sulphocyanide. A large number of different methods for the analysis of these products have been described, especially in the Journal fiir Gasbeleuchtzing ; but no general account of those mostly in use, and of their comparative value, seems to have been published in the journals dealing especially with analytical chemistry, so that a description of the methods more frequently employed, and of the precautions necessary in their use if accurate results are to be obtained, may be of value.TREATNENT OF THE PRODUCT BEFORE ANALYSIS. The crude products may consist solely of the soluble potassium, sodium or calcium salts, but more frequently they contain in addition insoluble ferrocyanides in the form of double ferrocyanides of iron with these metals or ammonium, the amount of which has to be included in the analytical results. In other cases, such as the spent oxide from gasworks, the whole of the ferrocyanide is present in an insoluble form, and these when present must be converted into soluble salts before analysis by treatment with caustic alkalies. For this purpose the sample is ground, thoroughly mixed, and a quantity of 30 to 40 grams placed in a mortar with an excess of caustic soda and about 100 C.C.of water, and allowed to stand for several hours, during which time it is frequently well triturated with the pestle, A few crystals of ferrous sulphate may also be added, whereby any cyanide, if present, is converted into ferrocyanide, and any ferricyanide reduced to ferrocyanide. Heat should not be employed, as the products mostly con- tain both ammonia and sulphides or free sulphur, the latter yielding sodium sulphide by the action of the caustic soda, and in hot solution the alkali sulphides, in presence of ammonia, effect a partial conversion of the ferrocyanide into sulphocyanide, thus tending to make the ferrocyanide results low. I n absence of ammonia, however, boiling sodium sulphide solution has but little action on ferrocyanide. The mixture, when decomposition is complete, is either filtered and iiiade up to 1,000 c.c., or it may be at once placed in a litre flask and made up to 1,000 C.C.plus a quantity of water equal to the volume of the insoluble matter present, which is then allowed to settle, and the clear solution taken for analysis. Many of the crude ferrocyanide samples, especially if obtained from coal-gas, contain, besides ferrocyanides, other complex iron-cy anogen compounds of much less value than the former, the presence of which interferes with all the usual methods of analysis. I t will, however, be most convenient to leave the consideration of these compounds and their removal until later, and to deal first with the analysis of the products when the only iron-cyanogen derivatives present are the ferrocyanides.The methods of analysis commonly employed may be divided into three classes, depending upon- 1. The direct estimation of the ferrocyanide present by titration with a suitable metallic salt (copper or zinc sulphate).THE ANALYST. 263 2. The estimation of the amount of iron present in the solution, and calculating 3. The estimation of the amount of hydrocyanic acid present. from it the amount of ferrocyanide. 1. TITRATION WITH METALLIC SALT SOLUTIONS. Of these methods, the first is probably most frequently employed, using copper sulphate as the standard solution, this having been originally suggested by Bohlig (Polytechlz. Notizblatt, 1861, 16, Sl), and modified and more completely worked out by Knublauch (Journd fiir Gasbeleuchtung, 1889, 33, 450).I t consists in titrating the ferrocyanide solution, acidified with sulphuric acid, with a standard solution of copper sulphate, which precipitates the ferrocyanic acid as an insoluble copper salt, the addition of copper solution being continued until a drop of the clear solution no longer gives a blue coloration with a solution of a ferric salt. The copper sulphate solution is previously standardised by means of pure potassium ferrocyanide. If the solution contains sulphide, this is removed before titration by shaking with lead carbonate, and filtering of the lead sulphide and the excess of lead carbonate. In place of copper sulphate, a solution of zinc sulphate is sometimes employed, the method being the converse of that for the estimation of zinc by means of potassium ferrocyanide.This method, when carried out under proper conditions, gives results of fair accuracy, but it is one in which these conditions must be somewhat rigidly adhered to, as otherwise figures may be obtained which are altogether incorrect. As the solution is acidified with excess of sulphuric acid, the liquid actually titrated consists of a solution of ferrocyanic acid and sulphuric wid, together with the sulphate of the metal originally in combination with the ferrocyanic acid. The reason for the variable results frequently obtained lies in the fact that the reaction does not proceed quantitatively in accordance with the equation h’,Fe(CN), + 2CuS0, = Cu,Fe(CN), + 2K2S04, but, instead, a much smaller quantity of copper is used t o effect complete precipita- tion.The precipitate consists, in fact, not of pure copper ferrocyanide, but of an insoluble colloidal double ferrocyanide of copper and the metal originally present as ferrocyanide, and the proportion of such metal and of the copper contained in the precipitate varies in accordance with the nature of the soluble sulphate present. The same is also true of the precipitates obtained with zinc sulphate. In order to obtain definite figures showing the extent to which the nature of the soluble sulphate affects the quantity of copper or zinc solutions used, solutions were prepared of copper sulphate, containing 10 grams CuS04,5H,0 per litre, and of an exactly equivalent solution of zinc sulphate, containing 11.51 grams ZnS0,,7H20 per litre, and also solutions of potassium, sodium, and calcium ferrocyanide, con- taining respectively 4 grams K4Fe(CN),,3H20, 4.584 grams Na4Fe(CN),,10H20, and 4.813 grams Ca2Fe(CN),,12H,0 per litre.These ferrocyanide solutions are exactly equivalent, each containing 2.044 grams ferrocyanic acid, H,Fe(CN),, per litre ; and if the reaction proceeded quantitatively in accordance with the equation given above,264 THE ANALYST. 50 C.C. of each of these solutions would require for complete precipitation 23.6 C.C. of either the copper or zinc solutions. The actual results obtained were as follows : CUSOA. %nSOp 50 C.C. K,Fe(CN) solution = 16.4 17.0 C.C. 50 ,, Na,Fe(CNO, solution = 18.0 17-30 ,, 50 ,, Ca,Fe(CN), 9 9 = 18.4 17.45 ,, From these figures it is manifest what a very important influence the nature of the soluble sulphate present exerts on the amount of copper used, potassium sulphate reducing this much more than sodium, which in turn reduces it rather less than calcium sulphate.The same influence is observable in the case of zinc sulphate, but it is much less marked than with copper. It follows, therefore, that if, for example, a copper sulphate solution were standardised with potassium ferrocyanide, and then used for titrating a solution of calcium ferrocyanide, the results obtained would be more than 10 per cent. too high. I t is, therefore, an essential condition of accuracy that the copper or zinc solution must be standardised with the same salt of ferrocyanic acid as is used for the titration.This is quite familiar to chemists who are regularly dealing with this method; but, so far as I can ascertain, the fact does not seem to have been published, and has, therefore, not become known generally, owing to which great discrepancies have sometimes occurred in the results obtained with the same sample by different analysts. A further fact, and one much less generally known, is that not only the nature of the sulphate present, but also its quantity, materially affects the amount of copper or zinc salt required. This is shown by the following tests, using in each case the same quantity of the solutions of potassium sodium and calcium ferrocyanide as before, with the addition of varying quantities of the sulphates of the metals : 50 C.C.K,Fe(CN), solution + 0.2 gram K,SO, 50 7 , 9 ) + 1.0 9 , 9 , 50 ? 9 ,, + 2.0 grams K,SO, 50 9 9 9 9 + 3.0 ,, 9 , 50 I , 9 , + 4.0 ,, 9 , 50 1 9 9 , + 5.0 ,, ,, 50 9 , #, + 10.0 ,) , I 50 9 , 2 , +1.0 ), 9 , 50 ,9 9 ) +5*0 grams NazSO, 50 I , 9 9 saturated with CaSO, 50 C.C. Na,Fe(CN), solution+ 0.16 gram Na,SO, 50 C.C. Ca,Fe(CN), solution + 0.15 gram CaSO, cuso,. = 15-85 = 15.5 = 15.1 == 14.9 = 14.75 = 14.6 = 14.0 = 17.65 = 17.3 = 16.7 = 18.2 -- 18.0 ZnSO,. 17.0 C.C. 16.9 ,, - - - 16.4 ,, 17.2 C.C. 17.1 ,, 16.8 ,, 17.35 C.C. 17.3 ,, - It will be seen that in this case also varying quantities of salt present have a very great influence on the quantity of copper required for precipitation of the ferro- cyanide, whilst the zinc reaction is also affected, though to a smaller extent, and that in both cases the potassium salt has a much greater effect than the sodium or calciumTHE ANALYST 265 salt.In order, therefore, to obtain correct results by either the copper or zinc methods, it is necessary to have always present approximately the same proportion of salts, both in standardising the solution and in carrying out the titration, as well as to have the same ferrocyanide salt in both cases. The ordinary practice is to standardise the copper or zinc solutions with pure potassium ferrocyanide, as this salt is the one most readily obtained pure, and is quite stable at the ordinary temperature. The solutions to be tested are then, before titration, converted into the potassium salt. If calcium ferrocyanide has to be analysed, and only small quantities of other calcium salts are present, this is readily done, without adding any material excess of potassium salt, by careful precipitation with potassium carbonate in the cold, and the filtrate may then be titrated, with correct results.To convert the sodium salt into potassium salt, however, this must first be converted (in accordance with Knublauch’s instructions) into Prussian blue by precipitation with ferric salt, the blue filtered off, and converted into potassium ferrocyanide by decomposition with caustic potash. An excess of the latter is necessary to effect complete decomposition of the Prussian blue, and this excess, after filtering and acidifying with sulphuric acid, is converted into potassium sulphate, which is therefore present in the liquid titrated in much greater proportion than in the pure potassium ferrocyanide used for standardising, and causes the results to come out low.To avoid this error, the copper or zinc solutions should in such cases be standardised with pure potassium ferrocyanide to which potassium sulphate has been added in proportion corresponding to that present in the liquid obtained from the decomposition of the Prussian blue precipitate by caustic potash. I find, however, that for practical purposes this tedious precipitation of Prussian blue is quite unnecessary, and by a, simple modification any of the soluble ferro- cyanide salts may be directly titrated without complete conversion into potassium salt. I t has already been pointed out that potassium salts have a much greater influence on the titration than the others, and it seemed likely that, if an excess of potassium sulphate solution were added to the solution before titration, the influence of any other sodium or calcium salts present would be negligible. Tests made on the lines of those described above have shown that such is the case, as will be seen from the following figures : cuso,.ZnSO,. 50 C.C. K4Fe(CN), solution +5*0 grams K,SO, = 14.6 16.4 C.C. ” } = 14.6 16.45 ,, 50 9 , 9 9 ” { 1::; grlm Na,SO, 50 ,, Ca,Fe(CN), ,, +5*0 g r m s K$O, = 14.65 16.45 ,, 50 ,, Na,Fe(CN), solution +5*0 ,, ,, = 14.6 16.4 ,, If, therefore, the ferrocyanide present in solution is not potassium ferrocyanide, there is no need to remove the other metals, provided that an excess of potassium sul- phate is added to the solution.I n practice I add to the solution to be tested 50 C.C. of a cold saturated solution of potassium sulphate (practically 10 per cent. solution), and also add a similar quantity of the potassium sulphate solution to the pure potass- ium ferrocyanide used in standardising the copper or zinc solutions, the weight of the latter taken being approximately equal to that which is present in the solution to266 THE ANALYST. be analysed. The analytical results given at the end of the paper were obtained in this manner, and it will be seen that these are in fair agreement with those found from determination of the amount of hydrocyanic acid. Variations within reasonable limits of the dilution and of the amount of free sulphuric acid present do not materially affect the results.The determination of the end-point of the reaction is one which requires some little practice, and should always be carried out in a good light. Various methods of ascertaining the end- point are adopted, such as filtering small portions of the liquid through Swedish filter-paper, and adding ferric solution to the filtrate, or placing a, drop of the liquid on a Schleicher and Schiill drop reaction filter-paper, followed by a, drop of ferric solution placed so as to come in contact with the clear wetted portion only of the first spot. Which method is preferred depends largely upon the taste of the operator, but both give good results provided only that the same time is allowed for the develop- ment of the blue colour, both in standardising and titrating.A slightly larger quantity of copper or zinc solution is used, both in standardising and analysis, if the filtering method is employed. 2. DETERMINATION OF THE IRON. The second method employed is that of determining the quantity of iron, and calculating therefrom the amount of ferrocyanide. This method was first proposed by Rose (Zeii. analyt. Chem., 1862, 1, 194), and further developed by Leybold and Moldenhauer (Journal fiir Gasbelezichtung, 1899, 33, 153), the ferrocyanide iron being converted into ordinary iron salts by evaporating the dry substance with con- centrated sulphuric acid. This procedure is not altogether a pleasant one, and a much more convenient method ie that of Dittrich and Hassel ( B e y ., 1903, 36, 1929), which obviates the necessity of evaporating the solution. This consists in slightly acidulating the solution with sulphuric acid (much acid should be avoided, as in that case the decomposition is often not quite complete), adding 2 to 3 grams of ammonium persulphate, and heating to the boiling-point for twenty to thirty minutes, whereby the whole of the iron is converted into ferric sulphate. Sometimes a slight blue colour persists, which may be removed by the addition of hydrochloric acid and more ammonium persulphate. The solution thus obtained should not be directly titrated with permanganate or bichromate, as products sometimes remain in the solution which affect those reagents, and cause the results to be too high. The solution is therefore precipitated with ammonia, the resulting ferric hydroxide being filtered off, and then either ignited and weighed, or redissolved in acid, and the iron estimated by permanganate or bichromate according to the usual methods.Tests made in the above manner with pure potassium and sodium ferrocyanides, using bichromate for estimation of the iron, gave excellent results. Found. Calculated. Pure potassium ferrocyanide, Pure sodium ferrocyanide, K4Fe(CN),,3H,O . . . ... 13.27 13-23 per cent. of Fe. Na,Fe(CN),,lOH,O ... 11-58 11-54 9 , #,THE ANALYST. 267 In testing by this method, the assumption is made that all iron contained in solution is present as ferrocyanide ; and as 56 parts of iron are equivalent to 422 parts of potassium ferrocyanide and 484 parts of sodium ferrocyanide, it will be seen that even small quantities of iron present in other forms would cause the results to be materially high. According to my own experience, whilst the method is reliable for the analysis of fairly pure crystals of the potassium or sodium salt, containing only small quantities of carbonate or sulphate, it' is not suitable for the analysis of crude products, as these, quite apart from the frequent presence of complex iron cyanogen derivatives other than ferrocyanides, almost invariably contain iron which is not combined with cyanogen at all.Thus, the ferrocyanide solutions obtained in gasworks, by washing the crude gas with a mixture of ferrous salt and alkali, always contain a soluble double sulphide of iron and the alkali used, which is very troublesome in working up the solution to finished crystals, owing to the separation at late stages of black sulphides of iron, which spoil the appearance of the crystals and necessitate recrystallisation.More- over, when the samples have to be treated with caustic alkali to decompose insoluble ferrocyanides, some iron frequently passes into solution, especially in the case of spent oxide, which contains much organic matter. In all such cases the dissolved iron is included in the analysis, and counted as an equivalent quantity of ferrocyanide, making the results too high. This is well seen in the analyses of samples by the different methods given at the end of this paper, in which the percentages calculated from the quantity of soluble iron present are invariably higher than those found by the other methods.The high result given by this method has been previously pointed out on several occasions. (See, for example, Knublauch, Journal fur Gas- beleuchtung, 1889, 33, 451 ; Bernheimer and Schiff, Chem. Zeitung, 1902, 26, 227 ; Luhrig, ibid., p. 1039.) 3. DETERMINATION OF THE HYDROCYANIC ACID. . This method, originally proposed by Rose and Finkener (Zeit. analyt. Chem., 1862, 1, 299), depends upon the fact that ferrocyanides are converted into mercuric cyanide by boiling with mercuric oxide, and has been further studied by Drehschmidt (Journal fur Gasbelez~chtz~ng, 1892, 36, 221), and especially by Feld (ibid., 1903,47,565), who has worked out an exceedingly convenient and accurate means of estimation of hydrocyanic acid present as complex iron-cyanogen compounds.This has beeh used with great success by Messrs. Forbes-Carpenter and Linder in their investigation of the composition of ammoniacal liquor (Forty-first Annual Report on Alkali Works, 1904, p. 29). The procedure may be shortly described as follows.: A quantity of the solution, prepared as described above, and containing the equivalent of 0.3 to 0.5 gram of potassium ferrocyanide, is diluted with water in a large flask, mixed with 10 C.C. N caustic soda, and heated to boiling; to this 15 C.C. of hot 3N magnesium chloride solution are added, and the boiling continued for five minutes, after which 100 C.C. of boiling & mercuric chloride are added. After boiling for a further ten minutes (not longer), the flask is connected to a condenser, 30 C.C.of 4N sulphuric acid added by268 THE ANALYST. means of a stoppered funnel, and distillation continued for twenty-five to thirty winutes, the end of the condenser dipping under the surface of 25 C.C. N caustic soda placed in the receiver. In this manner the whole of the hydrocyanic acid is obtained as a solution of sodium cyanide in the receiver, the contents of which are diluted t o about 400 C.C. A crystal of potassium iodide is added, and the liquid titrated with & silver nitrate until a permanent yellow precipitate of silver iodide makes its appearance. One C.C. of & silver solution equals 0.0054 gram HCX, and from this the amount of ferrocyanide is readily calculated. PRESENCE OF OTHER CYANOGEN COMPOUNDS IN THE CRUDE MATERIALS. So far, in dealing with the analytical methods, it has been assumed that ths cyanogen is all present in the form of ferrocyanide.This is, however, by no rneang always the case. Occasionally cyanide and ferricyanide are present in small quantity, but these are unimportant, a8 they are readily converted into ferrocyanide by the action of alkaline ferrous hydroxide, both by the analyst before analysis and by the manufacturer during the working up of the material, But in addition to these, many of the products, and especially those obtained from crude coal-gas, frequently contain appreciable quantities of carbonyl ferrocyanide. This salt has the composition represented by the formula Na,FeCO(CN),, and may be regarded as sodium ferrocyanide in which one molecule of NaCN is replaced by the radical CO.These salts were first discovered by J. A. Muller in spent oxide, and he ahowed later that they may be obtained by the action of carbonic oxide under pressure on hot ferro- cyanide solutions (Compt. Rend., 1887, 104, 994 ; Ann. Chim. Phys., 1889, (6) 17, 93 ; Compt. Rend., 1898, 126, 1421). Their presence in the products obtained from coal- gas is therefore readily accounted for, as the latter usually contains from 5 to 10 per cent. of carbonic oxide. In chemical properties these salts closely resemble the ferro- cyanides, but are readily distinguished from them by the colour of the ferric and copper salts; thus, they yield with ferric salts a deep purple-coloured precipitate or coloration in other respects closely resembling Prussian blue, whilst with copper salts they give an apple-green precipitate in place of the chocolate-coloured com- pound yielded by ferrocyanides.The soluble salts are much more soluble than the corresponding ferrocyanides, so that when present in the crude material they accumulate in the mother-liquors, and are of but little value to the ferrocyanide manufacturer. The actual quantity of carbonyl ferrocyanide in the crude products has varied in my experience from nil to, in exceptional cases, as much as 20 per cent. of the total cyanogen present, but usually the amount in gasworks products varies from 2 to 5 per cent. The presence of carbonyl ferrocyanide interferes with the analysis in all the methods described above, as it is precipitated along with the ferrocyanide by both zinc and copper solutions, whilst the iron in it is estimated along with the ferro- cyanide iron and the hydrooyanic acid from it by the Feld method.Naturally, the ferrocyanide manufacturers object to the inclusion of this comparatively valueless material in the analysis as ferrocyanide ; but, nevertheless, the removal of these compounds before analysis is frequently not carried out. For many years past I have employed a simple method of separating theseTHE ANALYST. 269 compounds which gives satisfactory results, and depends upon the fact that whereas ferrocyanides are quite insoluble in moderately dilute alcohol containing 25 per cent. of water, the carbonyl ferrocyanides are readily soluble. To the solution prepared in the manner previously described (which must be alkaline or neutral-not acid), four to five times its volume of methylated spirits is added, when the whole of the ferro- cyanide is precipitated, together with any sulphate, carbonate, or chloride present, whilst the carbonyl ferrocyanide, sulphocyanide, sulphide, and excess of caustic alkali remain in solution. Precipitation is complete in a very short time; but, if possible, it is best to allow the mixture to stand for several hours, as it then filters much more readily.After filtering off, the precipitate ie washed with a little methyl- ated spirit, and dried in the water-oven. If calcium ferrocyanide is being analysed, it is advisable to convert this into sodium or potassium ferrocyanide by addition of the corresponding carbonate before adding alcohol, as the dry calcium salt is not very stable at looo, and loss of cyanogen may occur in drying.The dried precipi- tate is then dissolved in water, and the solution analysed in the manner already described. The solution preoipitated with alcohol should not contain more than 10 per cent. of salts, end the proportion of carbonyl ferrocyanide present should not exceed 20 per cent. of the total cyanogen. This is never the case with ordinary samples, but it occurs with the mother-liquors obtained in working them up. In such case8 it is easier to determine the ferrocyanide by precipitation with lead acetate in slightly acid solution, the carbonyl ferrocyanide not being precipitated by lead salts. The lead ferrocyanide is then decomposed by boiling sodium carbonate solution, and the filtrate from the lead carbonate analysed.In the following table will be found the results of the analysis of six samples of crude ferrocyanide by each of the above methods, the first set giving the results obtained without removal of carbonyl ferrocyanides, and the second set the figures found after their elimination by treatment with alcohol. The nature of the samples was as follows : A. Crude sodium ferrocyanide cake from gasworks, containing insoluble ferro- cyanides, carbonyl ferrocyanide, and sulphocyanide. B. Ditto, second sample. C. Sample of crude sodium ferrocyanide, containing large quantities of iron D. Sample of crude calcium ferrocyanide from gasworks, containing carbonyl E. Sample of spent oxide, containing traces only of carbonyl ferrocyanide.F. Sample made up with known quantities of materials as follows, containing sulphides, but no carbonyl ferrocyanide or sulphocyanide. ferrocyanide and sulphocyanide, but no insoluble ferrocyanides. 15 per cent. of Na,Fe(CN),,lOH,O : Sodium ferrocyanide, Na,Fe(CN),,lOH,O ... 15 grams. Sodium carbonyl ferrocyanide, Na,FeCO(CN)i;iOH,O 3 ,, Iron alum ... ... ... ... . . I ... ... 25 ,, Sulphur ... ... ... ... ... ... ... 20 ,, Bog-iron ore ... ... ... ... 37 ,, ... ... 100 grams.870 THE ANALYST* The results obtained are given throughout in terms of crystallised sodium ferrocyanide, Na,Fe( CN),, 10H,O. ANALPSJS OF SAMPLES WITHOUT THE REMOVAL OF CARBONYL FERROCYANIDES. By CUSO, ... 69.8 74.5 45.7 94.2 6.2 17.2 By Fe ...71.6 77-5 49.2 95.5 8.0 18.9 By HCN ... 70.4 74.7 45.9 94.6 6.5 1 7 4 A. H. C. D. E. F. By ZnSO, ... 69.6 74.4 45.8 94.3 6.3 17.2 per cent. Na,Fe(CN),,lOH,O. ANALYSIS OF THE SAME SAMPLES AFTER REMOVAL OF CARBONYL FERROCYANIDES BY ALCOHOL. A. B. C. D. E. F. 68.3 73.9 48.9 93.5 7.0 16.0 per cent' Na4Fe(CN)6,10H!20* I By CUSO, ... 67.4 71.6 46.2 92.5 6.1 14.6 By ZnSO, ... 67.6 72.4 45.6 92.1 6.2 14.9 By Fe ... By HCN ... 67.2 72.4 45.9 92.8 6.3 15.2 A comparison of the results obtained before and after the removal of carbony1 ferrocyanide shows that the presence of the latter influences the different methods in varying degree, the iron method being more affected than the other three. This is what would be expected, as carbonyl ferrocyanic acid is tribasic, and ferro- cyanic acid tetrabasic, so that less metal proportionally would be required for the precipitation of the former.This acid also only contains five CN groups in the mole- cule instead of six CN as in ferrocyanic acid, and therefore in calculating the results from the amount of HCN found, only five-sixths of the amount of carbonyl ferro- cyanide is reckoned as ferrocyanide. On the other hand, in the carbonyl ferro- cyanide the proportion of Fe : CN is 1 : 5, and in ferrocyanide 1 : 6, so that in calculating the amount of ferrocyanide on the assumption that all iron is present in that form, 18 times the amount of carbonyl ferrocyanide present is reckoned as ferrocyanide. As will be seen also from the analysis of C, which is free from carbonyl ferro- cyanide, the results obtained before and after precipitation with alcohol agree within the experimental error.The same is true of the sample of spent oxide, E, which was found to contain practically no carbonyl ferrocyanide. Of the various methods, that giving the most accurate results is the determina- tion of the hydrocyanic acid, according to Feld's process. The Knublauch process, whether using copper or zinc solutions, when a r r i e d out with the precautions given above, yields results in very fair agreement with those obtained by the Feld method; but there is much greater variation between the results of duplicate determinations, which may differ by about 1 per cent. The iron method, however, invariably gives much higher results with crude products, whether carbonyl ferrocyanides are present or not, and I do not think this method should ever be employed, except in the case of comparatively pure crystals of potassium or sodium ferrocyanide containing only a small percentage of sulphate, carbonate, or similar salts.The Knublauch method, especially after a little practice, is one which is very readily carried out, and the results are of sufficient accuracy to make it a very valuable one for use in the control of the working of a ferrocyanide plant. As aTHE ANALYST. 271 method of analysis for determining the value of a product as between buyer and seller, where the analysis may have to be oarried out by an analyst not in constant practice with the method, it is much less suitable. For such' purposes, the Feld method, with the addition of the previous separation of the carbonyl ferrocyanides by means of alcohol, is, in my opinion, the most satisfactory.When once the necessary solutions, have been made up, the analysis is readily and quickly carried out, whilst the titration with decinormal silver nitrate gives a very sharp and easily recognised end-reaction, and is one with which nearly all analysts are quite familiar. DISCUSSION. Dr. R. LESSING said that it had long been known that in the copper precipitation test certain irregularities occurred, but as far as he was aware, the reason for these had never until now been cleared up, although the presence of indifferent salts was known to influence the reactions. Copper ferrocyanide, &R was well known, had a, great tendency to form colloid solutions, and, as the author had mentioned, the actual precipitate was a colloidal body. No definite relationship seemed to have been established for the double compound that was formed, but the copper ferro- cyanide was probably partly present in colloidal solution and partly precipitated as a, hydrogel.What the author really did was to add an electrolyte, and by adding the maximum amount of electrolyte required for the precipitation of the hydrogel from the hydrosol the end-reaction was obtained very rapidly, The fact that when zinc was used the differences were not quite so great seemed to support that assumption, for the tendency to form colloidal bodies was stronger with copper ferrocyanide than with the corresponding zinc salt. The estimation of the iron in the ferrocyanide complex was, as had been pointed out, a good method for pure salts, but with crude ferrocyanide products it was almost impossible to get the alkaline solutions free from iron, and whether ammonium persulphate was used for the decomposition of the iron cyanogen compounds, or strong sulphuric acid according to the method of Molden- hauser, the results were invariably too high.When, however, the ferrocyanide could be isolated pure, the method was a practicable one. The most accurate method was, of course, the distillation method, in which the hydrocyanic acid actually present was estimated. The author's figures showed the great importance that must be attached to the presence of carbonyl ferrocyanide, which at present, rightly or wrongly, was regarded as practically valueIess.At any rate, there was no market for it, and probably no use at present, and it was most important that it should not be reckoned as ferrocyanide. In dealing with mother-liquors containing ferro- cyanide, carbonyl ferrocyanide, and sulphocyanide, a useful little qualitative test was to put B somewhat long streak of the mother-liquor (possibly diluted) on a filter- paper, and close to it a similar line of ferric chloride solution, when the reaction could be observed in stages : first the formation of Prussian blue, then the formation of oarbonyl ferrocyanide (indicated by its purple colour), and finally the red of the ferric sulphocyanide. Dr. MONIER-WILLIARJS asked the best method which the author had found of determining accurately the proportion of carbonyl ferrocyanide.He (the speaker) was in the habit of precipitating the ferrocyanide with lead acetate, removing the272 THE ANALYST. excess of lead with sodium carbonate, and precipitating the carbonyl ferrocyanide as iron carbonyl ferrooyanide. The precipitate was difficult to wash properly, but the method appeared to give good results. Mr. CHAPMAN (Honorary Secretary) read a letter from the President in which reference was made to the question of the presence of carbonyl ferrocyanide in crude sodium ferrocyanide. The President pointed out that representations were frequently made to him by buyers, under contract, of crude ferrocyanide to the effect that he should exclude the carbonyl ferrocyanide from his analysis on the ground that that compound was of little or no value for the majority of purposes for which the crude ferrocyanide was used. He (the President), however, had not seen his way to fall in with this suggestion, but for many years had been in the habit of giving the total cyanogen, soluble and insoluble, and its equivalent of dry and hydrated ferrocyanide of sodium.It had always appeared to him that the question of excluding any particular cyanogen compound should be a matter for the contract or of special arrangement between the buyer and the seller. Dr. COLMAN agreed with Dr. Lessing’s suggestion as to the nature of the change which the addition of soluble salts brought about. He had only had time to deal with the question so far as analysis was concerned, and it undoubtedly called for a great deal more work-in the direction, for instance, of determining the proportions of potassium, sodium, and copper in these various precipitates ; and it had occurred to him that it would be interesting to titrate pure ferrocyanic acid with copper salts.As regards the determination of carbonyl ferrocyanide, he had found the Feld method to be the best, On precipitation with alcohol all the carbonyl ferrocyanide was obtained in the filtrate. On making alkaline, boiling off the alcohol, and treating the residue with magnesium chloride and mercuric chloride, the whole of the cyanide was given off, and the hydrocyanic acid was determined with silver nitrate. He had tried the method mentioned by Dr. Monier-Williams, but had given it up on account of the difficulty of filtering the ferric carbonyl ferrocyanide. For the preparation of fairly pure carbonyl ferrocyanides from the mother-liquors, which are rich in those salts, a quick method was to add an equal bulk of methylated spirit (which pre- cipitated most of the sulphates, carbonates, and all the ferrooyanides), filter, and then an equal bulk of ether. The solution divided into two layers, the bottom layer being a solution of carbonyl ferrocyanide in water, alcohol and ether, and the top layer a solution of sulphocyanide in ether. The point raised by the President was rather a legal than an analytical one. With a contract merely mentioning ( ( ferrocyanide ” he (the speaker) had always contended that it was improper to include carbonyl ferrocyanide, which, although 6 L ferrocyanide ” happened to be part of its name, was totally different from ferrocyanide, and was of very little commercial value. When about eleven years ago he had first had to deal with ferrocysnide products he had never heard of carbonyl ferrocyanide. On his attention being called by the buyers to the mysterious (‘ purple compound ” contained in the product, he looked into the matter and found that this had already been discovered and described by Muller. In the contracts with which he was then concerned, “ ferrocyanide ” was specified, and it seemed to him right to find out how much carbonyl ferrocyanide there was in the material, and credit the buyers accordingly, and it was for the purpose of this deter- mination that the alcohol method described in the paper was worked out,

ISSN:0003-2654    

DOI:10.1039/AN908330261b

出版商:RSC    

年代:1908

数据来源: RSC

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THE ANALYST, a73 A NEW METHOD FOR MILK-TESTING. BY W. M. DOHERTY, F.I.C. (Read at the Meeting, May 6, 1908.) IT has previously been observed that there is a relationship between proteid matter and ash, and it has long been known that the amount of ash a, milk contains is a valuable guide to genuineness or otherwise. Vieth has recorded, and he is confirmed by Richmond, that the ash bears a certain proportion both to the proteid and milk- sugar. The indications thus given, however, are generally not so near the truth as those given by the determination of the solids-not-fat. This is probably due to the general want of accuracy in the determination of the ash, apart from any other con- sideration, since loss of chlorides or inclusion of unconsumed carbon vitiates results in either direction.NO. 1 2 3 4 5 6 7 8 9 10 11 ::: 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 P205 per 100 C.C. 0-2165 0.2201 0.2201 0,2201 0.2165 0.2165 0,2201 0.2230 0.2230 0.2219 0.1942 0.2201 0.2201 0.2201 0.2201 0,2201 0.2201 0,2201 0.2201 0.2201 0.2201 0.2201 0.2165 0.2231 0,2130 0.2230 0,2230 0-2231 0.2231 0.2231 Total Solids. 13.0 13.1 12.5 13.7 12.7 13.4 13.2 13-2 13.3 13.8 11.2 12.0 14.4 14.4 15.5 14.3 14.4 15-4 13.0 14.1 14.2 14.2 12.6 12.7 14.3 14-0 15-0 14.0 14.5 14.6 Fat. 4-0 3.8 3.7 4.2 4.0 4.1 4.1 3.9 4.1 4.2 2.3 3-0 4.8 4.5 5.35 4.7 5.7 3-85 5-1 5.1 5.1 3.7 3.8 4.9 5-3 5.5 5.3 4.8 4.95 4.8 Solids-not-Fat. 9.0 9.3 8.8 9-5 8.7 9.3 9.1 9.3 9.2 9.6 8.9 9.0 9.6 9.9 10.15 9-5 9-7 9.7 9.15 9.0 9.1 9.1 8.9 8.9 9.4 8.7 9.5 8.7 9.7 9.65 * Abnormal milk, cow just calved.274 THE ANALYST.This difficulty is fully appreciated by those who have to deal simultaneously and expeditiously with large numbers of samples. I was led, therefore, to seek some constituent in the ash which could be easily and accurately determined, and I found that phosphoric acid would suit my purpose. The table on p. 273 gives the amount of this body stated in terms of P,O, per 100 C.C. of milk, side by side with the total solids, fat, and solids-not-fat respectively. The significant point of this table is the almost uniform constancy in the yield of phosphoric acid, which does not proportionately follow the amount of solids-not-fat. This is not what might have been expected from the observations of Vieth, since phos- phoric acid might reasonably be regarded as more constant in the ash than in the milk as a whole. Objection may be made to this method that, owing to the small proportion of phosphoric acid occurring in milk, it would not be safe, even if the amount of this acid was a constant, to rely on any determination, since the slightest experimental variation would mean a great error when interpreted as added water. Now the determination of phosphoric acid may be made with such accuracy by experienced workers that this objection is not valid.The ordinary magnesia mixture method is sufficiently exact, and, provided the phosphoric acid in milk proves to be as generally constant as in the samples tested by me, it is capable of giving results nearer the truth than the determination of the solids-not-fat, the great quantitative difference not withstanding.There are interesting volumetric processes for the determination of P,O, which, being applicable to milk analysis, might here be mentioned, that described by John Castell Evans in his Experimental Chemistry ” being apparently a good one. He titrates the acetic acid solution of an alkaline phosphate with alum, using Brazilin as an indicator. The process of Sigismund Littman (Chemical News, 1900, 80, 178), slightly modified by Messrs. Hirt and Steel (Proceedings of Chemistry Industry of Victoria, 1905, p. 14), is undoubtedly good. I t depends upon the addition of sodium citrate to the phosphate solution, which has been rendered neutral to methyl orange, and titrating to the neutral point of phenolph- thalein, each C.C. of TD caustic soda requjred being equal to 0.0071 gram of P,O,.There is also a process by Emmerling noticed in ‘‘ Fresenius Quantitative Analysis,” vol. ii., and another containing the same idea has been worked out by Dr. T. Cooksey (Proceedings of Royal Society of New South TVales, 41, 163). This process depends upon the precipitation of the phosphoric acid as a tricalcic salt in the presence of excess of calcium chloride, thus : Iron and alumina do not interfere. 2H,NaPO, + 3CaC1, = Ca,(PO,),+ 4HC1+ 2NaC1. The amount of caustic soda which is equivalent to the amount of hydrochloric acid indicated by the above equation is a, direct measure of the phosphoric acid. Beginning from the milk-ash properly incinerated, the P,O, may be estimated in ten minutes or even less. The ash of the milk is dissolved in a minimum quantity of dilute hydrochloric acid, treated with an excess of calcium chloride (about 5 C.C.of normal solution), boiled to expel any carbon dioxide, and carefully brought exactly to the yellow stage of the methyl-orange indicator with caustic soda free from GO,.THE ANALYST, 275 Phenolphthalein is then added, and the solution titrated with i\ caustic soda, each C.C. of such solution used between the two points of neutrality being equal to 0,00355 gram of P,O, !half that of Littman’s method). caustic alkali; from this the quantity of milk to be used in each test was calculated, and it amounted to 16.7 C.C. Taking this quantity, if the milk be genuine at least 10 C ~ C . of +’! alkali should be required, Thus, every tenth of a C.C.of & alkali r s e d is equal to 1 per cent. of milk, and as it is easy with some experience to read to less than a, tenth, the objection before noticed of want of accuracy, on account of the relatively small quantity of phosphoric acid in milk, is not tenable. The extreme difference noted amounts to 5 per cent,, while with the same lot of samples the difference shown in the range of the amount of solids-not-fat amounted to no less than 14 per cent. I n no case, using the phosphoric acid method, did actual watering escape detection. Two samples which yielded 8-52 and 8-41 per cent, of solids-not-fat revealed, by my method, watering to the extent of 5 and 10 per cent. respectively, and four samples declared to be watered by the solids-not-fat number showed by the phosphoric acid number watering to a greater degree, thus : Added IYater by Solids-not-Fat Method.Ten C.C. of milk by this prbcess required as a minimum 6 C.C. of Added Water by Pliosphoric Acid Xethod. Per Cent. Per Cent. 24.0 ... ... ... ... ... 33.0 8.0 ... ... ... ... ... 20.0 8.0 ... ... ... ... 13.5 1.5 ... ... ... ... ... 6.7 From what has been here said it would appear that the phosphoric acid method is capable of indicating results nearer the truth than those obtained by the deter- mination of the solids-not-fat. It is not proposed, however, to supersede‘ the old process just yet. Before such a revolutionary change can be endorsed, large numbers of milk samples will have to be analysed to confirm the results stated above.The method at present in use can at least be supplemented by an estimation of the phosphoric acid, which now, I have no doubt, will prove valuable in special cases. PUBLIC HEALTH DEPARTNEXT, SYDSEY, N. S.W. DISCUSSION. Mr. RICHMOND said that the average percentage of phosphoric acid found by the author was rather less than that which he (Mr. Richmond) had found-namely, 0.23. He thought that when the author examined a larger number of samples he would find the variations to be much greater than those stated in the paper. [NOTE BY H. D. RIcmfosD.-sincc taking part in the discussion of the paper (which was read in abstract) I have had an opportunity of perusing it, and noting tlie method used for the estimation of phosphoric acid. Though I have had no actual experience of the method, I have found that in titrating phosphoric acid with solutions of the alkaline earths- (i.) The end-points are not very distinct. (ii.) The results do not correspond esactly with molecular ratios. jiii.) The amount of hosphoric acid calculated from the difference between methyl orange and phenolphthakin is always low, and varies with conditions of dilution, rate of addition of the solution, and sliuhtly with temperature. For these reasons I doubt the relictbihy of the method, and consider the excellent agreement of results shown as adventitious.]

ISSN:0003-2654    

DOI:10.1039/AN9083300273

出版商:RSC    

年代:1908

数据来源: RSC

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276 THE ANALYST. MAFURA TALLOW AND MAFURA OIL. BY W. R. DANIEL AND J, McCRAE. MAFURA tallow, obtained from the seeds of Trichilia emeticu, was first described by De Negri and Fabris (cj. Lewkowitsch, (' Oils, Fats, and Waxes," third edition, p. 715); this vegetable fat was also examined at the Imperial Institute (cf. vol. i., p. 26) in 1903. I n the National Standard Dispensatory the tallow is referred to as having the melting-point 42', and is stated to be obtained by boiling the seeds of Trichilia emetica, Vahl. Through the kindness of Dr. G. A. Turner, Medical Officer to the Witwatersrand Native Labour Association, we have been enabled to examine specimens of oil and fat prepared by natives in Portuguese East Africa from the seeds of Trichilia enzetica. The fruit of this tree (which is known amongst the native tribes as Umkuhlu, Mkhuklu, Marba, Marwa-Maawa, Gnanda, Mafoureira, Mafura, or Mafurrera) is about three-quarters of an inch long, and contains three loculi, in each of which there is from one to three bright red seeds with a large black spot.The sample examined at the Imperial Institute is described as consisting of d d small brown nuts covered with a thin shell, which is easily detached by rubbing." I t is a fact that on drying the seeds they assume the appearance described, but the change of colour from bright red to brown takes place comparatively slowly under ordinary circumstances. I n his report to the Witwatersrand Native Labour Association in 1907, Dr. Turner odls attention to the fact that two fatty products are obtained by the natives from the seed : 1.After boiling, a clear yellow oil can be skimmed off, which is used for cooking purposes, and is held in much esteem. 2. After crushing the seeds an oil is extracted, which remains solid at a fairly high temperature; it is poisonous, and is used by the natives for greasing their skin. Samples of each of these have been examined, and will be referred to as mafura, oil and mafura tallow. Mafura Oil.-The oil is clear and fluid at the ordinary temperature, but con- geals when maintained for some hours at a temperature of about 5" C. I t possesses a slightly yellowish colour, and when solid is almost white. On examination the oil gave the following constants : Specific gravity-l5"/15" C. ... ... ... ... 3Oo/15O C. ... ...... ... 40"/15" C. ... ... ... ... Zeiss butyro-refractometer reading-at 20" C. ... ... 9 9 30' C. ... ... $ 9 ,, 40" C. ... ... Acidity, expressed as oleic acid ... ... ... ... Saponification value ... ... ... ... ... ... Iodine value ... ... ... ... ... ... ... Saponification value of the acetylated oil ... ... about Acetyl value (corrected for volatile acidity) ... ... Reichert-Wollny number ... ... ... ... ... > 9 29 9 9 9 9 ,, 0.931 0.920 0.913 65.6" 60.1O 54.6' 8-9 % 202 -5 66 235 36-5 2-0THE ANALYST. 277 Unsaponifisble matter ... . . . ... ... . . . 0-8 % Halphen's test ... ... ... ... ... negative Specific gravity-92'/15' C. ... ... ... ... ... 0.854 Solidifying-point ... ... ... ... ... ... 44.2' Zeiss butyro-refractometer reading-at 50' C. ...... 37.2" Neutralisation value , . . ... ... ... ... ... 201 Saponification value ... ... ... ... ... ... 206 Iodine value ... ... ... ... ... ... ... 68 The oil is optically inactive. The mixed insoluble fatty acids obtained from the oil gave the following constants : Mafwa Tallow.-The sample was of a yellowish colour, and on examination gave the following constants : Specific gravity-30'/15' C. ... ... ... ... 4Oo/15O C. ... ... ... ... Melting-point.. . ... ... ... ... ... ... Zeiss butyro-refractometer reading-at 40" C. ... ... Acidity, expressed as oleic acid ... ... ... ... Saponification value.. . ... ... ... ... ... Saponification value of the acetylated oil.. . ... ... Acetyl value . , . ... ... ... ... ... ... Reichert-Wollny number ... ... ... ... ...Unsaponifiable matter ... ... ... ... ... ... 9 , Iodine value ... ... ... ... ... ... ... 0.909 0,902 29 5-38" 47.3' 14.7 % 201 43 *5 218 16 1.3 1.2 % The mixed fatty acids from the tallow gave the following constants : Specific gra~ity-92~/15" C. ... ... . I . ... 0.843" Solidifying-point ... ... ... ... ... ... 52.1' Zeiss butyro-refractometer reading-at 57" C. ... ... 26.3" Neutralisation value.. . ... ... ... ... ... 204 Saponification value ... *.. ... ... ... ... 205 Iodine value ... ... ... ... ... ... ... 46 The supposed toxic property of the tallow has not been verified. The value of the tallow for the manufacture of soap and candles has been pointed out in the Bulletin of the Imperial Institute. The following are the constants which have hitherto been recorded for Mafurlt tallow : I. De Negri and Fabris, prepared in laboratory ; 11. De Negri and Fabris, com- mercial sample ; 111. Imperial Institute, from entire nuts ; IV. Imperial Institute, from kernels only ; Ia. Mixed fatty acids from I. ; IIa. Mixed fatty acids from 11. Sample. Melting- Point. Solidifying- Point. Acid Valuc. I. ... 11. ... 111. ... IV. ... Ia. ... IIa. ... 35-41' C. 35.5-42' C. 37' c. 40" c. 51-54' C. 52-55' C. 33-25' C. 37-30' C. 20-25' C. 25-30' C. 47-44O c. 48-44' C. Saponification Value. 200.08 220.96 - - - - Iodine Value. 44.85 46.14 55.8 47.8 46.92 48.19 THE GOVERNMENT LABORATORIES, JOHANNESBUBG.

ISSN:0003-2654    

DOI:10.1039/AN9083300276

出版商:RSC    

年代:1908

数据来源: RSC

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378 THE ANALYST. ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. The Detection of Citric Acid in Wines, etc. G. Favrel. ( A m . de Chim. A I ~ . Appl., 1908, 13,177-179.)--The method is based upon the fact that concentrated sulphuric acid containing sulphuric anhydride decomposes citric acid into acetone- dicarboxylic acid and formic acid as in the equation- CO,H.CH,.C.CH,.CO,H = HCOZH + CO,H.CHZ.CO.CH,.CO,H. /\ OH CO,H The former acid is an active reducing agent, and is also characterised by giving a red-violet coloration with a solution of ferric chloride, I n applying the test, the residue from the solution, which should contain at least 5 mgms. of citric acid, is treatedTHE ANALYST. 279 with 3 C.C. of concentrated sulphuric acid (specific gravity 1.84) previously heated to 100" C.The contents of the tube are kept for two minutes at 80" to 90" C., then cooled, and, after being diluted with three times the volume of water, shaken with 10 C.C. of ether. On evaporating the ethereal extract, characteristic needle-shaped crystals of acetone-dicarboxylic acid are often obtained. The residue, whether crystalline or not, is dissolved in 3 C.C. of water, and the solution tested with 1 C.C. of an extremely dilute solution of ferric chloride. If the original solution contained salicylic acid, the latter must be removed beforehand by acidifying the liquid with hydrochloric acid and repeatedly extracting it with ether. The acetone-dicarboxylic acid also reduces hot ammoniacal silver nitrate solution and palladium chloride, and precipitates mercurous sulphate from a sulphuric acid solution of mercuric sulphate.In testing a wine for oitrio acid, 100 C.C. are evaporated to dryness and the residue treated with 7 C.C. of boiling water, followed by 35 C.C. of 95 per cent. alcohol, and left for thirty minutes. The liquid is then filtered, and the filtrate treated with a solution of 0.4 gram of calcium acetate in 5 C.C. of water. The impure calciuin citrate is separated, dried on a porous tile, and tested for citric acid as above described. I n this way 0-1 gram of citric acid per litre of wine may be detected with certainty. C. A. M. Freezing-Point of Cow's Milk and the Estimation of Added Water. W. R e Gm Atkins. (C'hem. News, 1908, 97, 241.)-The author shows, from a theoretical consideration of the relations between the osmotic pressures of the blood of an animal and of the milk which it secretes, that an upper limit to the osmotic pressure of milk corresponding with the (constant) osmotic pressure of the blood may be reasonably expected-that is, the freezing-point of the milk will never fall below that of the blood in a healthy animal.The author's experiments confirm this anticipation, and analyses of 100 samples of milk have shown that, while cow's blood freezes at -0.62" C., the freezing-point of the milk is constantly slightly higher, averaging -0.55 C., with extreme variations from the mean of -t.0*06". The apparatus used was the Raoult form with Beckmann's thermometer, employing a freezing mixture at -5" to -6" C. All measurements were made on a rising temperature, the liquid being first frozen and the temperature then allowed to rise to the true freezing-point after super-cooling.Since the fat of milk is not in actual solution, it has no influence on the freezing-point, which may therefore be used as a means for detecting and estimating added water in milk. Milk deprived of a portion of its "fat," but suffering no dilution with water, will have a high specific gravity and a normal freezing-point ; while milk containing added water will have a high freezing-point, approximating to that of water itself (0" C.). Taking -0-52" C. as the limit of freezing-point for unwatered milk, the percentage of added water may be deduced thus : 0.52 - freezing-point of sample freezing-point of sample.A. R. T. The Proportion of Soluble Silicic Acid" in Cacao Husks. H. Matthes (Zeits. ofentl. Chem., 1908, 14, 166-169.) - The estimation of and 0. Rohdich.280 THE ANALYST, the amount of silicic acid soluble in water was recommended by Zipperer (Die Chokoladenfabrikation, 1901, p. %9) and by Matthes and Miiller (Zed. Untersuch. Nahr. Genussm., 1906, 12, 94) as a means of detecting an addition of cacao husks to cocoa powders. The authors have therefore tested the value of the method upon twenty different kinds of cacao beans, and found the amount of silicic acid soluble in water to range from 0.02 to 0.88 per cent. Hence they conclude that the propor- tion of soluble silicic acid varies too widely to allow of any exact deduction as to the proportion of husks present being drawn from its estimation in a given sample of powdered cocoa, C.A. M. Detection and Estimation of Rice Husk in Feeding Stuffs. F. Schroder. (Arb. Kuiserl. Gesundheitsamte, 1908, 28, 213-224.)-Whilst rice husks are readily detected in feeding stuffs by the aid of the microscope, the mere detection of a piece or two of the husk is not of much importance, especially in the case of foods con- taining rice meal, as the introduction of a trace of husk may be quite accidental and unavoidable. The detection must therefore be accompanied by an estimation of the quantity present before a food can be said to be adulterated with rice husks. The amount may be ascertained from estimations of the ash and silica yielded by the sample. The following percentages of ash are yielded by different brans : Wheat, 5-50 ; rye, 8-22 ; oat, 8.31 ; barley, 5.63 ; rice meal (for cattle), 5.23 ; and rice husks, 17.40.The quantity of silica present in the ashes of these brans is as follows, the figures representing percentages calculated on the ash : Wheat, 0.89 ; rye, 1.99 ; oat, 70.74 ; barley, 48.73 ; rice meal, 16.93 ; and rice husks, 89.71. W. P. s. The Occurrence of Cyanogenetic Glucosides in Feeding Stuffs. T. A. Henry and S. M. J. Auld. (Jounz. SOC. Chenz. I d , 1908, 27, 428-433.)-The occur- rence of a cyanogenetic glucoside, accompanied by an enzyme which would decompose it on contact with water, has been found by Dunstan and one or both of the authors in Lotus arabicus, common sorghum, the beans of Phaseolus lunatus, linseed, and cassava (Phil.Trans. Eoy. SOC., 1901, 194, 515; 1902, 199, 399; PTOC. Roy. SOC., 1903, 72, 285; 1905, 78, 145). Of these, only Phaseolus lunatus and linseed are of importance as sources of feeding stuffs. The glucoside in linseed-termed linanzariiz by Jorissen and Hairs-was found by Dunstan and the authors to be identical with phaseolunatin (the a-dextrose ester of acetone cyanohydrin) previously isolated by them from the beans of Phaseolus lunatus. The proportion of hydrocyanic acid obtainable from linseed and young flax plants was found to vary from nil (in one case) to 0.17 per cent., whilst two samples of linseed cake yielded 0.032 and 0445 per cent. respectively. The method of estimation was based on a partial separation of the glucoside and its decomposition by boiling with mineral acid.The material was ground as rapidly as possible, and a weighed quantity extracted in a Soxhlet’s extractor with hot alcohol. The alcoholic extract was evaporated on the water-bath, and the residue treated with a mixture of 50 C.C. of water with 10 C.C. of 10 per cent. hydrochloric or sulphuric acid, and distilled (with the addition of more water if required) until hydrocyanic acid was no longer found in the dis- tillate, The amount of the acid wag estimated by a modification of the method ofTHE ANALYST. 281 Fordos and Gelis, the solution being rendered faintly alkaline with sodium bicarbonate, and titrated with standard iodine solution until a faint yellow colour showed that the whole of the hydrocyanic acid had been converted into cyanogen iodide.The presence of an enzyme was detected by mixing the freshly ground product with water containing a little chloroform or toluene (as an antiseptic), and subsequently testing for free hydrocyanic acid. No enzyme was detected in either of the two samples of linseed cake, and the authors attribute this and the non-toxic effect of the linseed cake now sold to the destruction of the enzyme by the heat used in the hot expression of the oil from the seed. With regard to the amount of hydrocyanic acid in the beans of Phaseolus Zzmatus, the authors’ observations confirm those of previous observers as to the greater proportion present in the dark-coloured Java or Nauritius beans than in the light-coloured beans from Burniah. But even white Rangoon beans may contain a considerable amount, as mas found by Tatlock and Thomson (ANALYST, 1906, 31, 249) and by Lange (ANALYST, 1907, 32, 255).In the authors’ experience, it was not until 1907 that white Rangoon beans yielding notable amounts of hydrocyanic acid were met with in commerce. Beans of other species of Phaseolus examined yielded no hydrocyanic acid, with the exception of two samples of edible Hungarian ” beans, stated to be varieties of P. v.zLZgnris, which yielded 0.003 per cent. Experiments with different portions of fresh cassava plants from ‘Trinidad proved that no free hydrocyanic acid was present, but that all obtainable was in the form of a, cyanogenetic glucoside (cf. ANALYST, 1907, 32, 385). Samples of Para rubber seed yielded about 0-048 per cent.of hydrocyanic acid, also present in the form of a glucoside. This is of imp?rtance from the fact that the seeds are likely to become a commercial product as a source of oil. The press-cake derived from them would contain 0.09 per cent. of hydrocyanic acid, or rather more than ordinary linseed cake. I n the authors’ opinion it is unsafe to assume that feeding stuffs containing cyanogenetic glucosides, and in which the enzyme has been destroyed by heat, may not be partially decomposed by enzymes in the intestine, or that the material will not be used in conjunction with another product containing a gluco- sidolytic enzyme. C. A. 11. The “Ethyl Ester Value” of Fats : a New Constant for the Detection of Cocoanut Oil. J. Hanu6 and L. Stekl. (Zeit.Untersuch. Nahr. Genussnz., 1908, 15, 577-587.)-The authors have . further investigated the method described previously by one of them (ANALYST, 1907, 32, SS), and find that the quantity of alkali required for the saponification of the esters in the aqueous portion of the distillate is criterion of the presence or absence of cocoanut oil in the sample under examination. The amount of alkali, expressed in C.C. of solution, is termed the “ethyl ester value” of the fat. In the case of butter, this value lies between 7 and 14 ; for cocoanut oil it is upwards of 40; whilst for all other commonly occurring fats it is less than 3. The process is particularly useful for detecting the presence of cocoanut oil in lard and cacao butter, but, owing to the variations of the value in the case of pure butters, a less quantity than 15 per cent. of cocoanut oil cannot be detected with certainty in butter. w. P. s.282 THE ANALYST. The Quantity of Formic Acid occurring in Honey. K. Farnsteiner. (Zeit. UntewLclt. Nalzr. Geitussm,, 1908, 15, 598-604.)-1t is shown that only from 0*0011 to 0.0024 per cent. of free formic acid occurs naturally in honey, whilst about 0.02 per cent. is present in a combined state. The total acidity of honey is due t o some other acid or acids, of which mslic acid is probably the chief. I t is suggested that the acidity of honey should be expressed in terms of malic acid instead of formic acid, giving at the same time the quantity of alkali required to neutralise 100 grams of the sample. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN908330278b

出版商:RSC    

年代:1908

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282 THE ANALYST. BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. A Method for the Estimation of Indole in Faeces. W. von Moraczewski. ( Z e z t . ~ i h y s i o l . Glum., 1908, 55, 42 ; through Chem. Zeit. Rep., 1908, 32, 262.)- A quantity of the faxes is diluted with 700 C.C. of water and distilled until 500 C.C. of distillate have been collected. The distillate is well mixed, and 150 C.C. are acidified with 10 drops of concentrated sulphuric acid, and shaken after the addition of 1 gram of kieselguhr. The mixture is filtered, and 100 C.C. of the clear filtrate are treated with 10 drops of a 0.2 per cent. solution of sodium nitrite. The red coloration produced reaches a masirnuin at the end of two hours, and is then compared with that given by a known quantity of indole. The comparison solution may con- veniently contain 0.0002 per cent.of indole. w. P. s. On the Behaviour of Lecithin Emulsions with Metallic Salts and Certain Non-Electrolytes. J. H. Long and F: Gephart. (Jozmz. Arne?.. CJiem. SOC., 1908, 30, 895-902.)-The results of the experiments recorded show that dilute solutions of lecithin are precipitated by a large number of salt solutions and acids. I t seems that the precipitating power is in some way related to the degree of dissociation of the various compounds ; for, whilst the ordinary mineral acids and tartaric acid are very active, acetic acid is weak, and boric acid quite inert. The mercuric sa1t.s tested were all weak in their action, and the activity decreased from the chloride through the acetate to the cyanide, which is practically without action.I t was found that, whilst ether and similar solvents scarcely extract any of the lecithin from its pure aqueous emulsion, the lecithin is taken up readily by the solvents after the addition of salts to the emulsions. This action is related to the precipitating power of the salts; mercuric cyanide and boric acid are inert in this respect. Certain non-electrolytes (glycerol, dextrose, sucrose, urea, and egg albumin) do not appreciably precipitate lecithin from its emulsions, and their presence does not aid the solution by ether. Lecithin emulsion is dissolved completely by an aqueous solution of bile salts, and in considerable proportion. The combination formed seema to be remarkably stable, and is not readily decomposed in such a manner as to give up the lecithin to the usual solvents.w. P. s. Observations on the Stability of Lecithin. J. H. Long. (Jounz. Amer. Cheiu. Soc., 1908, 30, 881-895.)-As the result of an investigation regarding the stability of lecithiiis from various sources, it was found that emulsions of egg andTHE ANALYST. 283 brain lecithin are comparatively stable with respect to temperature. Increase of temperature, or long-continued heating of the emulsions, does not appear to increase the dissociation as measured by the acidity or conducting power. The action of light on the emuleions is very slight. Lecithin emulsions have a marked acid reaction. On precipitating the emulsions with an excess of pure acetone, the residues left, on again being emulsified with water, are neutral.Precipitation of lecithin from its ether solution by means of acetone seems to furnish a product which becomes acid when treated with water. The acetone precipitation from water SO effects some decomposition, as shown by the ratio of nitrogen to phosphorus, the original ratio being 1 : 1.97, whilst that aftor acetone treatment was 1 : 2.48. The electrical conductivity of the emulsions suggests the presence of acid or basic groups, but, after purification by acetone, the conductivity is so much reduced as to indicate that this phenomenon is not due to lecithin itself, but to decomposition products. Emulsions of both egg and brain lecithin are readily precipitated by weak salt solutions. No apparent relation exists between the precipitating power and the valency of the metallic or acid ions of the salts.The extraction of lecithin from emulsions is aided by the addition of salts. w. P. s. Detection of Bile Pigments in Urine, W. Macadie. (Pharnz. J O ~ L T ~ . , 1908, 80,686.)-The test depends on the oxidation of bilirubin by an oxidising agent, and the production of a series of colours. About 10 C.C. of ordinary icteric urine, previously shaken up to include any sediment of urates, and made slightly acid if necessary by acetic acid, may be taken for the test. A sufficient quantity of a saturated solution of calcium chloride is added to precipitate the bulk of the urates. The mixture is treated in a centrifuge for two minutes, the liquid is decanted off from the sediment, and the latter is rinsed with a little water. The precipitate of urates contains practically all the bile pigments in the urine. To the sediment in the centrifuge-tube there are then added 5 to 6 C.C. of a mixture of 1 part of hydrochloric acid, specific gravity 1.16, and 3 parts of rectified spirit. The mixture is stirred to dissolve the urates, and 5 to 6 drops of nitric acid (specific gravity 1.42) are allowed to trickle down the side of the tube and collect in the tapering point. The liquid rapidly assumes a series of colours extending from the tapering bottom of the tube towards the surface of the liquid, in the following order: a yellow layer at the bottom, then wine-red, then blue, then bluish-green, and above that a green layer. When only traces of bile are present, the pigment from a pint of the urine may be concentrated in a small urate precipitate; the test is therefore delicate as well as rapid. Urobilin, blood-pigments, etc., do not interfere, and the influence of indican is entirely eliminated. J. F. B.

ISSN:0003-2654    

DOI:10.1039/AN9083300282

出版商:RSC    

年代:1908

数据来源: RSC

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THE ANALYST. 283 ORGANIC ANALYSIS. A New Catalysing Agent for Use in the Carrasco-Plancher Method of Elementary Analysis. 0. Carrase0 and E. Belloni. (Jounz. Pharm. Chime, 1908, 27, 469-473.)-The use of copper oxide as an oxidising agent in the electrical method of combustion (ANALYST, 1907, 32, 238; 1908, 146) has the drawback that the carbon mixed with it is sometimes difficult to burn completely owing to the want284 THE ANALYST. of permeability of the mixture, whilst lead chromate attacks the glass of the combus- tion-tube. The authors therefore recommend in place of either a finely divided platin- ised unglazed porcelain. This is prepared by crushing the porcelain in a mortar, and passing the powder through two sieves, the first with 80 and the second with 400 meshes to the square centimetre.The residue upon the second sieve is washed with water, then with aqua regiu, and again with water, and calcined in a platinum crucible. Fifty grams of the product are mixed with a solution of 1 gram of platinum chloride in 20 C.C. of water acidified with hydrochloric acid, the mixture evaporated to dryness in a platinum basin on the water-bath, and the residue treated with an excem of a concentrated solution of ammonium chloride. After standing for six hours the excess of liquid is decanted, the residue dried on the water-bath and ignited, and the treat- ment with platinum chloride repeated. The resulting product is so active that, when mixed in a porcelaiu crucible with a substance such as tartaric acid or lampblack, complete combustion of the organic substance may be effected by heating the crucible over a Bunsen flame.C. A. If.. A New Constant of Cellulose (Absorption of Sodium Hydroxide). W. Vieweg. (Zcit. angew. Clzem., 1908, 21, 865-867.)-When cotton cellulose is immeraed in excess of soIutions of sodium hydroxide of various concentrations, part of the alkali is withdrawn from the solution in the form of a loose combination with the oellulose. The proportion of sodium hydroxide thus taken up increases with the concentration of the alkali until a concentration of 16 per cent of sodium hydroxide is reached. This concentration represents a maximum limit at which the proportion of cellulose to sodium hydroxide absorbed is in the constant molecular ratio repre- sented by the formula Cl,H,,Olo : NaOH, and the cotton is said to be ‘( mercerised.” The cellulose which is recovered from the loose combination with sodium hydroxide by washing with water is permanently changed as regards many of its properties.One of the properties which is thus modified is the affinity of the recovered cellulose for sodium hydroxide when it is again immersed in a solution of the alkali. This affinity is increased, and the increase is greater the higher the concentration of the alkali used in the first immersion, up to 16 per cent. Thus, by estimating the quantity of sodium hydroxide withdrawn by the cellulose from a dilute solution under standard conditions, the ‘( degree of mercerisation ”-ie., the concentration of the alkali with which the cellulose had originally been treated-may be determined.The conditions adopted by the author for this test are as follows : 200 C.C. of a 2 per cent. solution of sodium hydroxide, previously standardised, are placed in a stoppered bottle of about 500 C.C. capacity; 3 grams of dry cotton are then introduced, and the bottle is shaken continuously for half an hour. The concentration of the sodium hydroxide solution is then again determined by withdrawing 50 C.C. for titration. The quantity of sodium hydroxide absorbed by the cellulose is then calculated from the difference in concentration before and after the experiment. Cotton cellulose previously treated with a 4 per cent. solution of sodium hydroxide absorbs 1.0 per cent. under these conditions, whilst cotton previously (‘ mercorised ” with a solution containing 16 per cent.or more of sodium hydroxide absorbs 2.8 per cent. in the test. Intermediate numbers are obtained for cotton which has been treated with solutions of the alkali of intermediate concentrations. J. F. B.THE ANALYST. 285 Estimation of the Degree of Mercerisation of Cotton Yarns. E D Knecht. (Journ. SOC. Dyers and CoZoz.w., 1908, 24, 68; Chem. Zeit. Rep., 1908, 32, 272.)- When mercerised cotton is dyed in the same bath, consisting of a substantive dye- stuff (preferably benzopurpurin 4 B), as ordinary cotton, the mercerised fibre absorbs a larger proportion of the dyestuff according to the strength of the sodium hydroxide solution with which it was mercerised. The quantity of dyestuff absorbed may be estimated by means of titanous chloride according to the author’s process (ANALYST, 1907, 32, 426).The method of estimating the I ‘ degree of mercerisation ” of any cotton yarn is carried out in the following manner : A weighed quantity of the mercerised yarn and an equal quantity of unmercerised yarn, of approximately the same quality, are dyed together in a bath composed of 3 per cent. of benzopurpurin 4 B, 5 per cent. of sodium carbonate, 10 per cent. of salt, calculated on the weight of the yarn and dissolved in twenty times its weight of water. The proportion of dyestuff taken up by each sample is then estimated. If the blank has absorbed 1-77 per cent. of benzopurpurin, the strength of the lye used for mercerising the sample under examination may be read off directly from the following table, but if the unmercerised yarn has absorbed more or less of the dyestuff, the result found for the mercerised sample must be corrected in proportion before making use of the table. TABLE SHOWING THE PERCENTAGE OF BENZOPURPURIN ABSORBED I ~ Y COTTON YARN MERCERISED BY LYES OF DIFFERENT SPECIFIC GRAVITIES, Specific Gravity of Caustic Lye. Percentage of Benzo- purpurin in Fibre.Specific Gravity of Caustic Lyc. ll Percentage of Benzo- purpnrin in Fibre. 1.050 1.100 1.125 1.150 1.175 1.200 1.77 1-88 2.39 2.57 2.95 3.02 1.225 1.250 1-275 1-300 1.325 1.350 3.15 3.27 3-38 3-50 3.60 3.66 J. F. B. Qualitative Test for Mercerised Cotton. E. Knecht. (Jozmz. SOC. Dyers and CoZour., 1908, 24, 67; Chem. Zeit. Ikp., 1908, 32, 272.)-In the author’s process for the estimation of benzopurpurin on dyed cotton, mercerised cotton behaves differently from unmercerised.I n the latter case the hydrochloric acid turns the colour immediately blue, whereas in the case of mercerised cotton, if a large excess of acid be avoided, it turns it reddish-violet. If, then, titanous chloride be added until the colour is nearly destroyed, ordinary cotton appears blue and mercerised cotton red. The difference is distinctly apparent if the cotton has been mercerised with lyes of specific gravity of 1-15 and over, without tension, or with lyes of specific gravity of 1.175 and over, with tension. Cotton mercerised with nitric acid of 1415 specific gravity shows the same reaction as cotton mercerised with sodium286 THE ANALYST, hydroxide, solution (5 grams per litre) of titanous chloride, but the results are not so sharp.A strong solution of stannous chloride may be used instead of a weak J. F. B. The Permanganate Equivalent of Indigotin. 0. Miller and J, Smirnoff. (Ber. deut. Chem. Ges., 1908, 41, 1363-1367.)-The authors have re-determined the quantitative relations between carefully purified indigotin and permanganate. The indigo was purified by digestion with hot glacial acetic acid containing 3 per cent. of hydrochloric acid, the residue was washed with hot acetic acid and then with water. These operations were repeated until no further impurities could be extracted ; in the case of natural indigo the substance was extracted six times. The indigotin was then crystallised from its solution in boiling aniline; in order to obtain the best results not more than 6 grams of indigotin should be dissolved in 1 litre of aniling, and the solution should be filtered.Samples of natural and synthetic indigo were thus purified. The oxidation was carried out by Miller’s method (Journ. d. Buss. Phys. Chem. Ges., 1892, 24, 275): The solution was prepared by digesting 0.5 gram of indigotin with 10 grams of sulphuric monohydrate in a water- bath for an hour and diluting to 1 litre. The permanganate solution contained 0-5 gram per litre. For the titration, the indigo should be st a concentra- tion of 1 in 180,000 to 100,000--i.e., about 50 C.C. of the indigo solution diluted with 600 C.C. of water. All the water used for preparing the solutions and for diluting should be distilled from a mixture of chromic and sulphuric acids.The results showed that 100 parts of pure indigotin required 42-14 to 42.25 parts of permanganate, mean = 42020 parts. Indigotin, whether prepared from natural or synthetic indigo, is a body of constant composition, corresponding closely with the formula determined by Dumas, C,,H,,N,O,. The permanganate equivalent found by the authors is practically identical with that given by Mohr, who found 42-16. The oxidation coefficient of indigotin by permanganate in presence of sul- phuric acid does not coincide with the theoretical equation, but is 12.6 per cent. below the theoretical value, 48.27. It corresponds to the ratio C,,H,,N,O, : Ol.7h. The authors remark that during the sulphonation of the purified indigotin they did not observe any production of sulphur dioxide nor the absorption of oxygen from the air by the product of the reaction, (Cf.Bloxam, Orchardson and Wood, ANALYST, 1907, 32, 99 ; and Bergtheil and Briggs, ibid., 1907, 32, 177.) J. F. B. A Method of Analysing Shellac. P. C. McIlhiney. (Journ. Amer. Chem. Soc., 1908, 30, 867-872.)-The followiog method is proposed for the estimation of rosin in shellac, and consists in dissolving the sample in glacial acetic acid or in absolute alcohol, adding a large quantity of petroleum spirit, and then diluting the mixture with water ; the petroleum spirit separates, carrying with it in solution all the rosin and the wax of the shellac. Two grams of the sample are dissolved, by the aid of a gentle heat, in 20 C.C. of glacial acetic acid or the same volume of absolute alcohol ; after cooling, from 100 to 300 C.C.of petroleum spirit are added slowly in order to prevent the formation of a liquid precipitate, which happena if the spirit be added suddenly. To the solution are now added, drop by drop, 100 C.C. of water, theTHE ANALYST. 287 liquid being agitated during the addition. The water ‘( unites with ” the acetic acid or alcohol, and the petroleum spirit separates together with whatever is soluble in it ; this includes the rosin and the wax. The shellac is also precipitatod, but as it is insoluble in the petroleum spirit, it remains as a precipitate suspended in the dilute acetic acid or alcohol. The two layers are now separated, the petroleum spirit layer is washed once or twice with water and filtered through a dry paper into a weighed flask, from which the spirit is evaporated, leaving a residue of rosin and wax, which is weighed. The residue is dissolved in hot alcohol, an excess of potassium hydroxide is added, and then a sufficient quantity of petroleum spirit.The mixture is next shaken with water in a separating funnel, the aqueous layer is drawn off and extracted again with petroleum spirit, whilst the latter is washed with water. The petroleum spirit is evaporated and the residue of wax weighed. The dilute alcohol solution containing the rosin is boiled to remove the alcohol, then acidified to pre- cipitate the rosin, and this is collected and weighed. By treating pure shellac according to this process, a small amount (about 1 per cent.) of material soluble in petroleum spirit is sometimes obtained.Its odour and low iodine value indicate that it is some resinous constituent of shellac; it is quite different from rosin. As shellac varnishes may contain, besides true shellac, not only rosin, but other gums and resins soluble in alcohol, the author has treated a number of these bodies by the process with the following results : Two samples of Manilla yielded 41.2 and 43.3 per cent. of matter soluble in petroleum spirit; two samples of Kauri, 37.9 and 27.0 per cent. ; two samples of Sandarac, 34-9 and 36.2 per cent. ; and one sample of Dammar, 89-9 per cent. w. P. s. Volumetric Estimation of Thiosulphonates. A. Gutmann. (Zcit. aual. Chcnt., 1908, 47, 294-303.)-The method described previously (ANALYST, 1907, 32, 372) for the estimation of thiosulphates may be applied to thiosulphonates. The reaction proceeds according to the equation : R.SO,S.M+ KCN = IZ.SO,M+ KCNS, in which IZ represents a monovalent organic radical and Ad a monovalent metal.The process is carried out as described for thiosulphates, but, after the titration of the excess of cyanide, TG silver nitrate solution is added in excess, together with a considerable quantity of nitric acid, and the mixture is filtered. An excess of zinc nitrate solution is added to the filtrate, and the solution is placed aside for some time in order that the sulphine compounds present may be converted into insoluble zinc salts. The excem of silver nitrate is then titrated with thiocyanate solution ; the zinc sulphinate need not be removed, as it does not interfere with the titration.One molecule of silver nitrate corresponds with 1 molecule of thiosulphonate. w. P. s. The Optical Activity of Spirits of Turpentine. C. H. Herty. (Jozmt. A m r . Chem. SOC., 1908, 30, 863-867.)-The results are given of a number of deter- minations of the rotatory power of specimens of spirits of turpentine distilled in the288 THE ANALYST. laboratory from oleoresins obtained from selected trees. The trees were growing on a Florida turpentine farm, were of various ages, and comprised two species-namely, Piizus palzistris (Long Leaf Pine) and P. heterophylln (Cuban or Slash Pine). Whilst the rotation of the turpentine from one and the same tree remained fairly constant throughout the year, wide variations were obtained in the rotation of turpentines from different trees of the same species. For instance, turpentines from P. hetero- phylla exhibited rotations (in 100 mm. tube at 20" C.) varying from +O" 15' to - 29" 26'; in the case of P. palwstris the readings ranged from + 1" 23' to + 18" 18'. The turpentine from one tree gave, during the year, readings of from -0" 15' t o -5" 45'. No explanation can be offered for these wide variations, as the trees were grown quite close to each other, and had, therefore, the same general conditions of climate, light, and soil. w. P, s.

ISSN:0003-2654    

DOI:10.1039/AN9083300283

出版商:RSC    

年代:1908

数据来源: RSC

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288 THE ANALYST. INORGANIC ANALYSIS. Volumetric Estimation of Antimony. A. Kolb and R. Formhals. ( h i t s . hzorg. Chem, 1908, 58, 202-208.)-The antimony is first converted into the antimonic condition. For this purpose the metal may be dissolved in aqua regia, or in hydro- chloric acid containing bromine, the liquid evaporated to a small bulk, and potassium hydroxide added uutil an excem of 4 grams per 100 C.C. is present. The liquid is then heated with hydrogen peroxide, and the excess of the latter decomposed by boiling. Or else the sulphide, obtained as usual in the course of analysis, is dissolved in a small excess of potaasium hydroxide, and the diluted liquid heated with hydrogen peroxide. The cooled liquid is then made strongly alkaline with potassium hydroxide, and again treated with hydrogen peroxide.I n either case the alkaline liquid is made acid with sufficient hydrochloric acid to leave an excess of 20 C.C. of acid (specific gravity 1,125) per 100 c.c., and 1 or 1-5 grams of potassium iodide are added. After ten minutes the liberated iodine is titrated as usual. The operation is preferably carried out in a flask filled with carbon dioxide. The results obtained are accurate. A. G. L. The Estimation of Carbon in Steel, Ferro-Alloys, and Plumbago by Means of an Electric Combustion Furnace. C. M. Johnson. ( J o u m . A??w. Clicm. Soc., 1908, 30, 773-779.)-The author estimates carbon in steel, etc., by direct combustion in oxygen in a porcelain or, preferably, silica tube, heated by an outer silica, tube wound with Hoskins resistance wire, through which an electric current at 220 volts is passed, a 32-ohm resistance being placed in series with the wire.The outer tube is packed, by means of magnesia, into a wide steel tube. The combustion is carried out at a temperature of 940' to 960' C., 2 to 5 grams of drillings which have passed a 20- but remained on a 60-mesh sieve being used. The drillings are placed in a compact heap on a layer of sand in a clay or porcelain boat. Oxidation is complete in three to six minutes, after which oxygen is passed for another ten minutes. A4cid fumes are retained by a jar containing granulated zinc placed between the combustion tube and the drying tube preceding the absorption apparatus. In burning ferro-alloys the drillings should be mixed with 4 grams of redTHE ANALYST.289 lead. The test results quoted am excellent, but the exact temperature must be rigidly maintained. The apparatus may be obtained from the Scientific Materials Co., Pittsburg, U.S.A. A. G. L. The Micrography of Cement. E. Stern. (Ber. deut. Chem. Ges., 1908, 41, 1742-1745.)-The petrographic method for the examination of thin sections of Portland cement clinker has been studied by Le Chatelier and by Tornebohm, the latter of whom classified the constituents under the names of ‘( alith,” ‘‘ belith,” ‘( celith,” and ( ( felith.” Of these, alith is by far the most important, and is readily distinguished by its four- and six-sided contours and its optical properties. Celith is a brown, doubly-refractive mass filling up the spaces between the particles of alith ; belith and felith are of rare occurrence.The author has now introduced the micro- graphic method of examination by reflected light, as used for testing alloys, for the purpose of examining set cements. The normal structure of hardened cement consists of two kinds of constituents-A, primary, and B, secondary. Constituent A is practically the unaltered cement grain, whilst the B constituents represent the products of setting and hardening. The micrographic picture may be measured by the plafimeter, and the relative proportions of A and B thus estimated. The structure remains practically unaltered during setting and hardening, although the very prolonged action of water gradually increases the proportion of B at the expense of A. By etching the cement surface the A constituent may be further resolved, and the resistant grains of the hardened cement are then seen to consist mainly of alith.Suitable etching reagents are alcoholic hydrochloric acid, alcoholic iodine solution, and 25 per cent. hydrofluoric acid. The method shows a very distinct difference in the normal structure of ferruginous cements and ordinary Portland cements ; by etching with hydrofluoric acid the particles of slag in the former may be recognised by brilliant interference colours and their proportion approximately estimated. Sea water modifies the appearance of the structure of sections of cement in a different manner from fresh water. A 1 to 2 per cent. solution of magnesium sulphate has an action similar to that of sea water.When the hardened cement is subjected to high temperatures, the structure becomes less distinct the higher the temperature, and the B constituents lose their water of combination and shrink together. With regard to the processes of setting and hardening, micrography shows that the setting process probably consists in the formation around each particle of cement of a relatively very narrow zone of hydration products. With this the formstion of structure constituents is apparently at an end, and all further changes (hardening) which take place inside the B constituents cannot be followed micrographically, because B appears to be a uniform substance by reflected light. The micrographic study of synthetic products will facilitate research on the physical (temperature) and chemical (composition) conditions necessary for the production of cement.J. F. B. The Volumetric Estimation of Chlorates. E. Knecht. (Journ. SOC. Clzem. Id., 1908, 27, 434-435.)-The method described is the same in principle as that of Lunge, the main difference being that the reduction is effected by means of titanous chloride in the cold, instead of boiling ferrous sulphate solution : GTiCI, + KC10, + GHCl = GTiCl, + KC1 + 3H,O.290 THE ANALYST. Fifty-c.c. of the standardised titanous chloride solution (1 C.C. = 0.0015 gram of iron) (ANALYST, 1907,32,426) are run into 5 C.C. of strong hydrochloric acid contained in a flask through which is passed a current of carbon dioxide. Ten C.C. of the chlorate solution (1 gram in 500 c.c.) are next introduced, and, after at least three minutes standing, some potassium thiocyanate solution is added, and the excess of titanous chloride titrated with a standard solution of iron ammonium sulphate (6 atoms of iron = 1 molecule of chlorate).I n estimating chlorate in bleaching powder, the '' available " (hypochlorite) chlorine is first found in the usual way, and the total chlorine from chlorate and hypochlorite then estimated by titrating with titanous chloride another portion of the solution, the difference between the two results corresponding to the amount of chlorate. C. A. M. The Separation of Clay in the Estimation of Humus. C. A. Mooers and H. H. Hampton. (Journ. Anzer. Cham. SOC., 1908, 30, 805-807.)-The authors have compared, on a number of Tennessee soils, the different methods which have been proposed to eliminate the error caused in the American official method for humus by the presence of clay.They find that filtration of the ammoniacal extract through a, Pasteur-Chamberland filter causes unsatisfactory and low results, due to the retention of humus by the filter. Subtraction of 10 or 14 per cent. from the values found gave better results, but the exact factor is uncertain, and duplicates do not always agree. The best results were obtained by evaporating the extract to dryness on a water-bath so as to coagulate the clay, and extracting the residue with 4 per cent. ammonia. Two evaporations and extractions were generally necessary to obtain a clear filtrate. A. G. L. A Volumetric Method for the Estimation of Copper.G. S. Jamieson, L. H. Levy, and H. L. Wells. (Jozim. Anze~. Chenz. SOC., 1908, 30, 760-764.)-The authors have successfully applied the potassium iodate method of Andrews (ANALYST, 1903, 28, 306) to the estimation of cuprous thiocyanate. The washed precipitate, together with the asbestos or filter-paper on which it was filtered, is placed in a bottle, 5 C.C. of chloroform, 20 C.C. of water, and 30 C.C. of hydrochloric acid are added, and a standard solution of potassium iodate, containing 11.784 grams of the salt per litre, is run in with constant shaking, until the colour first formed in the chloroform disappears. The reaction proceeds according to the equation : 4CuSCN + 7KI0, + 14HC1= 4CuS0, + 7KCl+ 7ICl+ 4HCN + 5H,O. One C.C. of the standard solution corresponds to 0.0020 gram of copper.The chloroform may be used a second time. To apply the method to ores, the sample is dissolved in nitric acid or aqua wgia, and boiled down with sulphuric acid until fumes of ihe latter are given off. The residue is diluted and filtered, after the addition of 1 or 2 drops of hydrochloric acid if silver is present, The small quantities of lead and antimony left in solution do not interfere with the subsequent precipitation of the copper by means of sulphur dioxide and ammonium thiocyanate. A complete estimation can be made in one hour. A. G. L.THE ANALYST. 291 Estimation of Iron in Ferrum Redacturn. G. Frepichs. (Archiv. Pharm., 1908, 246, 190-205.)--For the estimation of iron in ferrzm reclactuin, the methods in which mercuric chloride and iodine are employed (cf.ANALYST, 1905, 30, 338 ; 1906, 31, 23) were found to be quite untrustworthy, estimations carried out side by side yielding widely different results. The copper sulphate method of the British Pharmacopocia yielded results which were, on the whole, satisfactory, although a little higher than was deduced from estimations of the total iron, magnetic oxide of iron, insoluble matter, etc. The quantity of copper sulphate prescribed, however, is only sufficient for samples containing not more than 90 per cent. of metallic iron, and it is suggested that the quantity be increased to 1.5 gram! so that the iron may be estimated in samples containing upwards of 90 per cent. of iron. w. P. s. The Accuracy of the Colorimetric Estimation of Lead.H. W. Woudstra. (Zeit. Anorg. Cliem., 1908, 21, 168-175.)-Traces of lead in potable waters can be estimated colorirnetrically as sulphide by the following method, with a maximum error of less than 20 per ccnt. : To 5 litres of the water are added 10 grams of barium chloride (to effect a rapid coagulation of the precipitated lead sulphide), 3 grams of finely divided asbestos, and 500 C.C. of a solution containing 8 grams of sodium sulphide and 50 C.C. of fuming hydrochloric acid. After well shaking or stirring, the liquid is filtered. The asbestos is then extracted for five minutes with 2 C.C. of fuming hydro- chloric acid, and the solution filtered. The filtrate is evaporated to dryness, the residue is taken up in 1 or 2 C.C. of hydrochloric acid, the solution diluted to 125 c.c., and precipitated by hydrogen sulphide.After standing overnight, the precipitate is filtered off, washed, dissolved in hydrochloric acid, and the solution evaporated to dryness. The residue is taken up in water, an aqueous solution of hydrogen sulphide and a little potassium hydroxide are added, and the colour produced is compared with that given by a standard solution of lead, to which equal quantities of reagents are added. A. G. L. The Limitations of the Copper-zinc Couple Method in Estimating Nitrates. J. E. Purvis and R. M. Courtauld. (Proc. Cambridge Phil. Soc., 1908, 14, 441-446.)-The results are given of an investigation of the copper-zinc couple method for estimating nitrates, the object being to ascertain to what extent, if any, the presence of albuminous matters in the solution under examination affected the accuracy of the method.The estimations were carried out on solutions containing known amounts of nitrate, albumin, blood-serum, and peptono, and also on sewage free from nitrate. I t was found that the couple produced ammonia during the disintegration of the albuminous matters when nitrates were not present. The effect of the couple when acting in solutions containing both albuminous matter and nitrates was variable. In some cases the ammonia produced was more than would be formed by the reduction of the nitrates alone, and in others it was less. I n the latter case, however, nitrites were present in the solutions at the end of the experi- ments, indicating that complete reduction of the nitrates had not been effected.On the whole, it would appear that in waters heavily charged with organic. &rogenousTHE ANALYST. matters and in sewage the copper-zinc couple produces more ammonia than cor- responds with the quantity of nitrates present, and, although the amount of ammonia formed from the organic matters is small, some doubts are thrown on the accuracy of the method under these conditions. w. P. s. The Ammonia-Soluble Phosphoric Acid of the Soil. G. S. Fraps. (Amer. Chem. Journ., 1908, 39, 579-586.)-The author has studied the nature of the phosphoric acid which is dissolved by ammonia from the soil after treatment with hydrochloric acid to remove the lime. By some workers this phosphoric acid is assumed to be in organic combination with the humus, and to be of considerable importance.The author has found that mineral phosphates give up phosphoric acid to ammonia, under the conditions adopted for this determination. Moreover, the mineral phosphates which are dissolved by the ammonia are principally the phosphates of iron and aluminium, and are probably of low agricultural value. Absorbed phosphoric acid left after treatment of the soil with acids is also partly soluble in ammonia. A portion of the so-called humus phosphoric mid must there- fore be of inorganic origin; and an increase of ammonia-soluble phosphoric acid during the decay of organic matter in the soil is not evidence that there is a gain of organic phosphoric acid. I n some Minnesota soils which were investigated, about one-ninth of the ammonia-soluble phosphoric acid was found to be associated with the clay, one-third with the organic matter, and five-ninths remained in solution.The phosphoric acid associated with the organic matter does not diffuse and its amount does not increase when the organic matter is precipitated in the presence of phosphoric acid, nor does it decrease when the organic matter is dissolved, precipitated with lime, the lime removed, the precipitate dissolved in ammonia and reprecipitated. The author is of opinion that this phosphoric acid is in organic combination. The phosphoric acid associated with the clay is probably not in solution; that remaining in the filtrate is probably for the most part of inorganic origin, derived from the iron and aluminium phosphates.The organic phosphoric acid is present in much smaller quantity than has been believed to be the case, and therefore is of less agricultural significance. J. F. B. The Estimation of Phosphorus in Phosphor Tin. W. Gemmell and S. L. Archbutt. (Journ. SOC. Chem. I d . , 1908, 27, 427-428.) - The following rapid method is based upon the fact that the phosphorus in phosphor tin is quanti- tatively converted by hydrochloric acid into phosphorus hydride, which may be absorbed and converted into phosphoric acid by mems of bromine water. From 2 to 5 grams of the sample are placed in a 500-C.C. flask fitted with a delivery-tube and a thistle funnel with a two-way tap, so that gas or liquid may be introduced as desired. The delivery-tube is connected with three Drechsel absorption vessels, the two first containing about 0.25 inch of bromine, covered with about 1 inch of bromine water, and the third bromine water only.After removal of the air from the apparatus by means of a current of carbon dioxide, 50 to 100 C.C. of concen- trated hydrochloric acid are introduced, and the flask gently heated. After the action has apparently ceased, the contents of the flask are gently boiled, and aTHE ANALYST. 293 current of carbon dioxide then pasRed through the apparatus for five minutes. The contents of the absorption vessels are now washed into a beaker, the bromine expelled by boiling, and the phosphorus precipitated from the concentrated solution by means of magnesia mixture. Any arsenic present is simultaneously precipitated, and may, if required, be subsequently estimated in the magnesium pyrophosphate by dissolving the latter in hydrochloric acid, reducing the solution, and precipitating the arsenic with hydrogen sulphide.No tin is carried over into the absorption vessels, while only a slight trace of phosphorus is ever left' in the evolution flask. The results of the test experiments described are either in agreement with or slightly higher than those given by older methods. C. A. M. Di-thiocyano-selenious Acid, and its Use in the Estimation of Selenium. W. N. Iwanow. (Clzern. Zeit., 1908, 32, 468.)-A new compound of thiocyanic and sclenious acids, having the formula S(HCNS).H,SeO,, is obtained as a white crystalline precipitate on mixing solutions of selenious acid, ammonium thiocyanate, and hydrochloric acid.The compound is readily decomposed with separation of selenium, and may be utilised for the estimation of this element, as follows : To a solution containing 0.1 to 0.4 gram of selenium in 600 C.C. of water, 25 C.C. of a solution of ammonium thiocyanate (1 : 5 ) , and then 150 C.C. of hydrochloric acid (25 per cent.), are added. The whole is heated on the water-bath for twelve hours, and then allowed to stand overnight. The separated selenium is filtered off on a weighed filter, washed with hot water, dried at 105' C., and weighed. As it always contains sulphur, the precipitate is dissolved in aqua regia, and the sulphur estimated as barium sulphate. The results obtained in this way are concordant, and agree fairly well with those obtained by means of the sulphur dioxide method.On mixing solutions of tellurous acid, ammonium thiocyanate and hydrochloric acid, a brownish-yellow amorphous precipitate, consisting of tellurium and sulphur only, is obtained. A. G. L. The Comparative Oxidising Power of Sodium Peroxide, and its Use in Qualitative Analysis. D. F. Calhane. (Jozcrlz. Amer. Chenz. SOC., 1908, 30, 770- 773.)-The author shows that sodium peroxide readily oxidises chromic salts to chromates in the wet way, even when large amounts of iron and aluminium are present, Sodium peroxide generally gives more reliable results than bromine water and caustic soda, or pota.ssium chlorate and nitric acid; but with dilutions of only 0*00008 gram of chromium per C.C. of solution, the chromium is oxidised to per- chromate, which yields a precipitate with lead acetate in acetic acid solution only on standing and warming. The fusion test with sodium carbonate and potassium nitrate on platinum foil is as delicate as the wet sodium peroxide method. A. G. L. Estimation of Thorium in Monazite Sand. V, Borelli. (Chem. Zeit., 1908, 32, 509.)-A rapid method for the separation of thorium is described, the principal feature being the oxidation of the oxalate precipitate with permanganate in nitric mid solution. The sand is first heated for some hours with sulphuric acid containing294 THE ANALYST. hydrofluoric acid, and the mass is then dissolved in water acidified with hydrochloric acid. The earths are precipitated from the solution by means of oxalic acid, and the precipitate is oxidised with permanganate and nitric acid. The solution is then neutralised with ammonia, hydrogen peroxide is added, and the precipitated thorium peroxide is collected on a filter. The precipitate is dissolved in nitric acid, once more precipitated by the addition of hydrogen peroxide, collected on a Blter, washed, and ignited. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9083300288

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

294 THE ANALYST. APPARATUS, ETC. Simple Burner for Flame and Spectrum Reactions. W. Thorner. (Zeits. angew. Chent., 1908, 21, 673-677.)--The part of an ordinary Bunsen burner containing the air-holes is surrounded by a wide cylindrical drum of brass, A , provided with a ehort side-tube, I?, to which is connected a wide glass tube, C, bent downwards and just passing through the stopper of a small flask, I<. The stopper also carries a second short, straight glass tube, D. On lighting the burner, air is sucked through the flask into the air-holes, so that fumes and spray from the flask are carried into the flame. Spray is readily formed by adding a piece of zinc and a little acid to the substance in the flask, or by electrolysing the liquid in the latter. By providing the side tube of the drum with holes which can be wholly or partly closed by an ordinary regulator, the quantity of air sucked through the flask may be regulated. For very small quantities of liquids, a wide glass tube bent into the form of a U nt the end may be used instead of the above arrangement,.The ordinary brass burner may also be replaced by one of porcelain, or may be provided with a porcelain or aluminium extension, in order to give a cleaner flame. Various modifications of the apparatus can be obtained from C. Gerhardt, Marquarts Lager chem. Utensilien, of Bonn. A. G. L. Apparatus for the Determination of the Coefficient of Expansion of Oils and Other Liquids boiling above 100" C. W. Thorner. (Zeit. Chenz. 1908, 3, 165; through Chew. Zeit. Rep., 1908, 32, 259.)-The apparatus consists of a 100 C.C.flask with a long narrow neck graduated into c.c.'s, the 100 C.C. mark being close to the upper end of the flask. The flask is hung in the neck of a small still and heated to 100' C. by means of steam. At this temperature it is filled with the oil under examination to the 100 C.C. mark, and is then allowed to cool toTHE ANALYST. 295 the normal temperature, the contraction being noted. of different fats appear to be nearly identical. The coefficients of expansion A. G. L. Constant Pressure Gas-Governor. J. E. S. Jones. ( J o z w . Soc. Chem. I d , 1908, 27, 305.)-The apparatus, which can be made of ordinary laboratory utensils, is very useful for use with air-ovens when the gas-pressure varies and the tempera- ture is required to be kept constant.I n the illustration, A is a 200 C.C. beaker, inverted inside a bell-jar, B, which is fitted with a two-hole bung. E is a small piece of a thin test-tube cemented on the top of the beaker with gutta cement. The connections are made as shown, H , I , and G being glass tubes, and F rubber. The whole of the arrangement, C, is shown on a larger scale at the right of the diagram ; it is fixed independently of the bell-jar by the clamp, D, and consists of two concentric glass tubes, the outer one being provided with a side-piece. They c CAE areconnected by a piece of rubber, P, which enables the inner one hetlting the gas to be adjusted to any height. The bottom of the cup, T (or E), is filled with a small quantity of mercury. The action of the apparatus is as follows : The outer tube, 12, forms a gas-tight seal into the mercury, whilst the inner tube only just touches the mercury, and allows the gas to pass out at 7'.When the whole is empty of gas, the water-levels in A and B will be the same; but as soon as the gas is turned on with a greater pressure than required, the cup, E, will be at its lowest point, and allow the gas to push up A with full pressure. The mercury immediately closes the gas supply, and the beaker, A, falls again until more gas is allowed to enter. This action goes on successively and smoothly, and any pressure may be obtained by using more w. P, s. or less mercury in the cup. An Electrical Distillation Apparatus. E. H. Sargent and Co. (Electyo- chcnz. and: Jlctarl. Incl., 1908, 6, 169-170 ; Chem. ,%it.Bep., 1908, 32, 281.)-The apparatus con- sists of a flat circular retort the form of which enables a large heating surface to come in contact with a shallow layer of water. The condensing- tube is situated in a trough, which forms a ring around the circumference of the still, and which is fed by a continuous stream of water. The apparatus is easily cleaned, and will produce 1 gallon of distilled water per hour. J. $'. B.296 THE ANALYST. A New Form of a Refllling Burette. G. Miiller. (Chem. Z ~ i t . , 1908, 32, 532.)-The graduated cylinder, a, of the burette is provided with the ordinary tap, e, or pinchcock, whilst at the top it terminates in a large two-way stopcock. The smaller opening communicates with the reservoir, b, containing the standard solution, while the larger one communicates simul- taneously with the side-tube, c, so that the air from the burette displaced by the liquid can pass into the reservoir. A small opening in the upper stopcock, not shown in the figure, allows air to enter the burette when the lower tap is opened.C. A. M. The Use of the Gooch Crucible in Electrolytic Analysis. F. A. Gooch and F. B. Beyer. (Zeit. nnorg. Chenz., 1908, 58, 65-72.)-The authors use a Gooch crucible as the cathode in those cases in which the deposit is not very adherent. If a platinum crucible is used, it is connected with its cap by means of a rubber band, and with a glass prolongation (made from a piece of wide tubing) by a second rubber band; this glass prolongation serves to increase considerably the capacity of the crucible.The crucible is packed as usual with asbestos, on which are placed some pieces of platinum foil, which should touch the sides of the crucible, and which serve to increase the cathode surface. Connection with the lead is made by a platinum triangle pressed against the crucible by a rubber band. The glass prolongation is nearly closed by a funnel, which serves to prevent loss by spirting. A bent platinum wire passing through the funnel functions as an anode, When the electrolysis is finished, the cap is removed, the liquid is sucked out of the crucible, and the latter washed by the help of the pump, preferably without interrupting the current. An alternative procedure, adapted to very loose deposits, consists in continuously filtering the liquid during the electrolysis itself, the filtrate being from time to time returned to the crucible. This method may also be used with st porcelain Gooch crucible.In this case, a perforated platinum disc is first placed on the bottom of the crucible, then the layer of asbestos, and finally a second perforated platinum disc. Connection between the electric lead and the discs is made by a little chain of platinum wire, which can be folded up and placed inside the crucible during weighing. By using the Gooch crucible as the cathode, 0.5 gram of copper was completely deposited from copper sulphate solutions in thirty minutes, using a current of 2 amperes at 6 volts for the first five minutes, and 4 amp&res at 10 volts for the remaining twenty-five minutes.Nitrogen Estimations by the Dumas Method. H. Leemann. (Chent. Zeit., 1908, 32, 496.)-The author describes a simple arrangement for controlling the x A. G. L.THE ANALYST. 297 current of carbon dioxide used for clearing out the tubes in nitrogen estimations by the Dumas method. The carbon dioxide is generated in a separate tube by heating sodium bicarbonate. In the tube connecting the carbon dioxide generator with the combustion-tube is placed a three-way tap, the side branch of which leads into a bottle containing a mercury seal. Before the combustion the carbon dioxide is allowed to pass straight through the tap into the combustion-tube. When the air has been driven out, the tap is turned through an angle of go", and the carbon dioxide passes away through the mercury seal whilst the combustion is taFing place.Finally the tap is returned to the straight position, and the carbon dioxide sweeps out the residual nitrogen from the combustion-tube. J. F. B. A New Form of Pyknometer. W. R. BousAeId. (Trans. Chem. SOC., 1908, 93, 679.)-This instrument consists of two tubes, A and By connected, as shown in the figure, by a short tube C and by a handle D, by which the pyknometer can be suspended at a suitable height in a thermo- stat. The tubes A and B are conical at their upper ends, and are joined by the tubes E and F, of capillary bore, to the conical cups G and H, which can be closed by stoppers K and L. The pykno- meter is filled by replacing the stoppers by suitably bent tubes, one of which dips into the liquid to be examined, while the other is attached to a filter-pump or other exhauster.The cups are left partially filled with the liquid until the temperature is adjusted, when, by means of pieces of filter-paper screwed t o a point, the excess of liquid is removed from the cups until it stands at a mark, on each of the tubes E and F, made just at the constric- tion at the base of the cups. The cups are finally wiped with a suitable swab and the stoppers inserted before removing the in- strument from the thermostat. This pyknometer acts as a delicate thermometer when the level of the liquid has been adjusted, since, if left for a short time longer in the thermostat, the observation of the level will indicate whether the proper temperature has been reached.Any air-bubbles in the liquid may be removed by shaking or inverting the pyknometer, and can be expelled by sucking some of the liquid into the cup on one side or the other. Two instru- ments used by the author had capacities of 250 C.C. and 350 c.c., and gave results accurate to within +I in the fifth place of decimals. A. R. T. Apparatus for Sublimation. W. G. Llewellyn. (Chem. News, 1908, 97, 198.)-The apparatus consists of an open tube about 5+ inches long, fitting closely inside a 6-inch test-tube. The open tube is conveniently made from a large test- tube by cutting off the closed end. The substance to be sublimed is heated in the outer tube, the sublimate being deposited on the inner tube, from which it can readily be removed in a pure state. A loose plug of glass-wool at the open end of the apparatus prevents the escape of vapours. A. R. T.998 THE ANALYST, Receiver for Use in Vacuum Distillations, G. Kolbe. (Chem. Zeit., 1908, 32, 487.)-In the receiver shown in the illustration, the central rod passing through the upper part of the apparatus is ground at its lower end so as to form a, tight joint. When another flask is fitted on to the cork at the lower end of the apparatus, the air may be ex- hausted from it by means of a pump attached to the nozzle of the tap, before the central rod is raised to allow the collected distillate to flow into the flask. The exit for the air consists of a small opening in the side of the tube leading to the air- pump. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9083300294

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

998 THE ANALYST. DEPUTATION TO THE BOARD OF AGRICULTURE. THE question of endeavouring to secure better fixity of tenure for professional chemists appointed under the Sale of Food and Drugs Acts and the Fertilisers and Feeding Stuffs Act has long engaged the attention of the councils of this Society and of the Institute of Chemistry, and representations on the subject have from time to time been addressed to the Local Government Board and to the Board of Agriculture and Fisheries. Lord Carrington, the President of the latter Board, kindly consented to receive a joint deputation from the Society of Public Analysts and other Analytical Chemists and the Institute of Chemistry on May 14 last, but was prevented from receiving it personally, as he was required to be in attendance on H.R.H.the Prince of Wales on the occasion of the opening of the Franco-British Exhibition. However, as a number of representative chemists had travelled to London for the purpose, it was arranged that Sir Thomas Elliott, K.C.B., the Secretary of the Board, should receive the deputation, and the interview took place at the oEces of the Board on the date mentioned. Mr. E. G. Haygarth Brown, one of the superintending inspectors of the Board, was also present. The deputation consisted of Sir William Ramsay, K.C.B., Vice-president of the Institute of Chemistry; Mr. R. R. Tatlock, President of the Society of Public Analysts and other Analytical Chemists ; Mr. Edward Bevan ; Colonel Charles E. Cassal; Dr. Bernard Dyer ; Mr. Thomas Fairley ; Dr. John A. Voelcker ; and the Registrar of the Institute of Chemistry.Sir THOMAS ELLIOTT, in welcoming the deputation, said that Lord Carrington had asked him to express his regret that he was prevented from meeting them. The Board were much indebted to agricultural analysts for the part they had taken in the administration of the Fertilisers and Feeding Stuffs Act, and sympathised with them in their difficulties. He would be glad to learn what the deputation desired to lay before him.THE ANALYST. 299 Sir WILLIAAI RAMSAY said that professional chemiets warmly appreciated the courtesy which they had always received from the Board. In the interests of the public, it was essential that chemists entrusted with the administration of the Act should be well trained and qualified in every respect. Dismissals for no valid reason cast a slur on highly competent men, and made the appointments less attractive, SO that, unless something could be done to provide greater security for their tenure of office, the appointments would in all probability devolve on less experienced men.He then read the following memorandum, and commented, in passing, on the various points raised in i t : “ Under the Fertilisers and Feeding Stuffs Act, 1906, it is directed [Section 2 (2)] that every County Council shall, and that the Council of any County Borough may, appoint an official agricultural analyst, and may also appoint a deputy agricultural analyst; and that [Section 2 (4)] the appointment of these officers shall be subject to the approval of the Board of Agricultwe and Fisheries. “Thus the assent of the Board is required to the appointment of an agri- cultural analyst, but there is no clause rendering the assent of the Board necessary to his dismissal by the local authority, and no clause in any way relating to the duration or termination of his appointment.“ I n the Sale of Food and Drugs Act, 1875, there is a section (Section 10) dealing with the appointment of Public Analysts-officers discharging under that Act duties similar to those which agricultural analysts discharge under the Ferti- h e r s and Feeding Stuffs Act. That section, while empowering local authorities to appoint Public Analysts, and directing that such appointments shall be subject to the approval of the Local Government Board, deals at the same time with the question of their removal by the local authority, indicating that such removals, as well as appointments, shall be at all times subject to the approval of the Local Government Board.So far as it relates to rernovale, the section was presumably intended for the protection of the Public Analyst against arbitrary or capricious dismissal, or against attempts to alter unfairly the conditions of his appointment ; and it has been found on many occasions to work salutarily in this direction, although, unfortunately, some local authorities have virtually ‘ contracted thern- selves out ’ of the Act by making year-to-year appointments, whereby they can, if they so desire, evade the necessity of seeking the consent of the Local Government Board to the dismissal of an analyst by merely refraining from renewing his annual appointment-a proceeding which, although it seems to be contrary to the spirit of the Act, is apparently not contrary to its letter. ‘‘ Unfortunately, apart from this, the full effect of the protection offered to the Public Analyst by the Act of 18‘75 fails to be realised by reason of advantage being taken of the permission to appoint more Public Analysts than one, and to transfer the work and emoluments to a new one, without dismissiug the one previously appointed.“The object of directing attention to the provisions of the Sale of Food and Drugs Act is to point out that, in principle and in obvious intention, the Sale of Food and Drugs Act (to which the Fertilisers and Feeding Stuffs Act is analogous, and on which t o a large extent it is based) does, unlike the Fertilisers and Feeding300 THE ANALYST.Stuffs Act, acknowledge that the assent of the central Government Department charged with the supervision of the working of the Act shall be necessary to the removal or dismissal of a Public Analyst as well as to his appointment by the local authority. Thus, while the Local Government Board-though with some limita- tions, which appear to have been unintentional-has certain powers which it can exercise for the protection of the Public Analyst, whose position was evidently meant to be safeguarded, the Board of Agriculture and Fisheries, on the other hand, appears to have no power under the Fertilisers and Feeding Stuffs Act to extend similar protection, in case of need, to the agricultural analyst.The appointment of that officer must receive the approval of the Board, but his removal may be effected by the local authority without even reference to the Board, whose power in the case of an unjust or undesirable removal is confined merely to moral suasion, which may or may not be heeded by the local authority; and so the Board is unable to prevent an act of injustice on the part of a local authority towards an officer who to all intents and purposes (except for the channel through which he receives his remuneration and for his liability to summary dismissal) is an officer of the Board itself. He is paid by the local authority, but the Act imposes upon him the duty of reporting the results of his analysis directly to the Board of Agriculture and Fisheries, and he is subject to the direction of the Board with regard to many details in the execution of his duty-even as to the technical processes to be used in his analytical work. “ The Councils of the Society of Public Analysts and other Analytical Chemists and of the Institute of Chemistry wish to suggest to the Board that steps should be taken, by means of the introduction of a short Bill into Parliament, to place the agricultural analyst in a position at least as satisfactory as that in which the Sale of Food and Drugs Act sought to place the Public Analyst-namely, to put him under the protection of the Board, and, at the same time, to render the protection effective by avoiding loopholes for evasion, such as have been discovered in the older Act.“That there is real need of such protection has been shown by recent cases which have been prominently before the Board, and have given rise to correspondence between the Board and the local authorities, the Board having made a strong effort to dissuade the local authorities from making changes in the appointments except on substantial grounds, but being without power to veto the dismissals against which expostulation was made. In one such case the analyst was removed from his position as agricultural analyst for a county by the simple and summary process of not renewing his annual appointment, which he had held ever since the original Act of 1893 came into operation. I n this case, without any intimation whatever of an intention to remove him, the announcement was made that he had not been reappointed, and that another analyst had been appointed in his place.‘‘ I t appears to the Society of Public Analysts and other Analytical Chemists and to the Institute of Chemistry that, apart from the point of view of the analyst him- self, there are other reasons for urging that such insecurity of tenure of office is unde- sirable. Official agricultural analysts, as well as Public Analysts, are placed in a position of trust in connection with Acts of Parliament, the breach of which is regarded as a criminal offence. Their certificates may at any time result in a criminal prosecution, or,THE ANALYST. 301 in the case of the Fertilisers and Feeding Stuffs Act, may be used for the enforcement or adjustment of civil rights involving money claims, which may be heavy ; and, even when no legal proceedings may be involved, questions of commercial credit or discredit arise which may seriously affect the reputation of individuals.It is one of the great principles of English jurisprudence that judges and magistrates shall be appointed permanently, being liable to removal only by a mode of procedure involving a petition to the Crown, the object of such fixity of tenure being to place them in such a position that they are removed from even the suspicion of temptation, to be influenced in any decision by the possible effect that might thereby accrue to the stability of their official position. While it is not suggested that the office of analyst shouldhave attached to it quite such rigid permanence as this, yet it is urged that an analyst, who at any moment may have to report adversely on goods sold by persons who may be in a position to excite undue sympathy on the part of some county councillor, should not be in a position which subjects him to the chance of finding himself removed from his appointment by the simple process of non-renewal of an annual appointment. I t is not suggested that any local authority in the kingdom would consciously dismiss an analyst for doing his duty, but there are various ways in which committees may be unconsciously influenced to substitute one analyst for another without suspecting how or why the suggestions for change may have been originated.Cases are known-not under the Fertilisers and Feeding Stuffs Act, but under the analogous Sale of Food and Drugs Act-in which it has been the duty of the Public Analyst to issue certificates which have resulted in the prosecution of members, not only of the local authority appointing him, but even of the very committee to whom it was his duty to report the results of his analyses. “If the appointments of analysts under these Acts were by law constituted permanent appointments, subject only to determination by consent of the Board of Agriculture and Fisheries in the one case, or of the Local Government Board in the other, the position of the analyst would sometimes be rendered less difficult, and the independence of his position as regards unfair interference with his appointment would tend to operate in the direction of increased security for the public, or that section of it whom he exists to protect.‘(Even fixity of tenure of office, however, subject only to the pleasure of the Board of Agriculture, and not merely to that of the local authority, would not go far enough to secure the advantage which would accrue to the analyst, and, we believe, also to the public, from the permanence of his position, without regard to a further point in the terms of his appointment. Some analysts have been driven to resign, not actually by threatened dismissal, but by resolutions reducing their remuneration- or, which comes to the same thing, by resolutions requiring them to do an unreason- ably increased amount of work without additional remuneration. I t is in no spirit of trade unionism that analysts deplore the tendency on the part of both County and Borough Councils to attempt to cut down the remuneration of their professional officers.This, no doubt in many cases, arises from the utter inability of the members of such councils to understand anything whatever of the nature of the work involved in the actual process of making analyses, or of the time that it occupies, or302 THE ANALYST. of the out-of-pocket expenses that it involves. Too many of the people on whom falls the duty of appointing analytical officers confuse the nature of their work with that of the druggist who makes up a doctor’s prescription, and think that some such remuneration as suffices in such a case should suffice for an analyst. For this probably the English ambiguity of the word ‘chemist’ is partly responsible.In Germany there is no such confusion, the analyst being a ‘ chemiker,’ and the druggist an ‘apotheker.’ But in this country it is to be feared that the ignorance of the‘public sometimes tends to depreciate the value of the professional services of the analyst. “For these reasons it is submitted that the terms of the appointment of the agricultural analyst, as well as the appointment itself, and the termination of the appointment, ought to be subject to the approval of the Board of Agriculture and Fisheries. ‘ ( I t is suggested that the Board should introduce into Parliament a short Bill amending Section 1 (4) of the Fertilisers and Feeding Stuffs Act, 1906, which already provides that the appointment of an agricultural analyst should be subject to the approval of the Board of Agriculture and Fisheries.The amendment should provide : “ ( a ) that not onIy the appointment, but also the terms of the appointment (including the terms of remuneration), of an agricultural analyst shaI1 be subject to the approval of the Board; ( ( and further that : ‘‘ ( b ) notwithstanding any terms relating to the duration of his appointment under which any agricultural analyst may have been heretofore or shall be hereafter appointed, his tenure of office shall not terminate or be deter- minable without the approval of the Board.” Sir William Ramsay, in conclusion, suggested that, as the analysts were practically officers of the Board, the latter should endeavour to make the terms of the appointments suitable in every way, otherwise the best qualified chemists would decline to be candidates for such positions.Mr. R. R. TATLOCK said that he desired to endorse all that Sir William Ramsay had said. He alluded to the hardship imposed on an analyst who had conducted his work without fault or hitch of any kind, through his being subject to summary dismissal from his appointment without any valid cause, at the caprice of a local authority, or perhaps through some misrepresentation, and without any opportunity of being heard on his own behalf. The analysts, therefore, looked to the Board for some redress. Mr. BEVAN also endorsed the views which had been submitted. He asked whether the Board had the power to introduce a regulation under Section 4 of the Act requiring the sanction of the Board to dismissals. Dr.VOELCKER said that the appointments were offered originally to men who had acquired a certain standing in their profession, and their removal from such positions created a false impression in the public mind. If such removals were continued, the appointments would prove equally unsatisfactory to the reputations of those who succeeded to them in the future. The uncertainty as to their position made it necessary for them to appeal for some provision whereby all dismissals should be subject to the consent of the Board. They could not expect, of course, to hold303 THE ANALYST. the appointments indefinitely ; but under present conditions analysts could be removed at a moment’s notice and without any justifiable explanation.The Board had helped them in many ways in the past, and he hoped that something might be done to bring them into closer touch with the Board. Dr. DYER endorsed what had been said by the previous speakers. Colonel CASSAL said he wished to emphasise the point that t,he analysts were practically officers of the Board, to whom they have to report, and by whom their duties are directly controlled. He hoped, therefore, that analysts would receive the support of the Board against capricious action by local authorities. Severe training and experience were necessary for the proper conduct of their work, and he hoped the Board would encourage the appointment of the best type of chemist, or the result would be detrimental to public interests. There were numerous examples of unjusti- fiable dismissal both of Agricultural and Public Analysts, and these should be provided against, particularly as local authorities too often consisted of men who had no sympathy with the work of their chemical officers, and who, in some instances, acted from ulterior motives. Sir THOMAS ELLIOTT, in reply, said that the Board recognised the weight of the arguments which had been submitted.From the passing of the first Act, the Board had realised the importance, in the interests of agriculturalists, of securing the services of good analysts, and he thought that in this respect they were in a s favourable a position as any country in the world. The Board realised, also, the advantages of continuity in the service of such officers. The analysts had to be trained, and they had to maintain expensive laboratories and to keep their knowledge up-to-date for the benefit of the public, If they only held office for a year or so, their experience was wasted ; but by continuous service they became every year more eficient, and a t the same time better acquainted with local conditions, He agreed with Sir William Ramsay that in quasi-judicial appointments there should be stability ; it gave the holders more confidence, and they should not be subject to removal at mere caprice.He recognised the force of the case which had been presented. At the same time, he would remind the deputation that in the minutes of evidence given before the Departmental Committee only one analyst had spoken on the matter under discussion, and that analyst had expressed the opinion that the Act need not provide. for requiring the sanction of the Board to dismissals, and that the analyst should look after himself.However, besides the chemists and the Board, there was a third party to be considered-namely, the local authority. The deputation were, perhaps uncon- sciously, raising a question of great difficulty as to the division of powers and duties between central and local authorities. Even if more power were given to the Board in this matter, it might still be difficult to exercise it. They had experience of a case where the Board and the local authority held different views as to an appointment of an unqualified man, and for years no analyst was appointed. He would endeavour to obtain an opinion on the matter from the County Councils Association, the Municipal Corporations Association, and also from the Local Government Board. There was, perhaps, a biag in favour of power being given to local rather than to central authorities. If cases of unjustifiable dismissal occurred, the Board would communicate with the local authorities and do what they could to304 THE ANALYST. cause the matter to be fully considered. In the case of the action of one County Council, the Board had learned that, in dismissing their analyst, some df the members of the Council had no idea, that this was being done. He believed in making auch matters public, and hoped no further cases of the kind would arise. There was little chance of introducing an amending Act to one passed so recently as 1906, and the Board could not claim to make a regulation under Section 4, as Mr. Bevan had suggested ; but they recognised fully the force of the case which had been represented to them, and would see what could be done to further it. Sir WILLIAM RAMSAY having expressed the thanks of the deputation to Sir Thomas Elliott for receiving them, and for his kindness in taking so much interest in the matter, the representatives withdrew. @ @ + B e + + € +

ISSN:0003-2654    

DOI:10.1039/AN9083300298

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

304 THE ANALYST. REVIEW. CHEMICAL REAGENTS, THEIR PURITY AND TESTS. By E. MERCK. Translated by HENRY SCHENCK, A.B. 250 pp. Price 6s. net. London: Archibald Con- stable and Co., Ltd. This is a translation of Dr. Krauch’s work, which first appeared in 1888 under the title ‘‘ Die Priifung der Chemischen Reagentien auf Reinheit.” That the book supplied a want is evidenced by the fact that revised and enlarged editions appeared in 1891 and 1896, whilst in 1905 a further edition was published after a revision by Mr. E. Merck. The work deals with the reagents in ordinary use, an alphabetical arrangement being followed. Under the head of each substance are given its formula, molecular weight, and salient physical properties, and then follow tests for purity, when directions are given for the detection of impurities commonly occurring in the substances dealt with. References to the literature dealing with the tests are given in footnotes. Of these rather a large proportion are to papere which have appeared in German journals. At the end of the book are tables of atomic weights, constants for volumetric analysis, and an index. J. T. H. @ + 3 * * % PARIS MUNICIPAL LABORATORY. DURING the month of May, 1908, 2,013 samples were analysed in the Municipal Laboratory. Of these, 499 were samples of milk, of which 132 (=26*5 per cent.) were found to have been adulterated. Of 481 samples of wine examined, 77 (= 16 per cent.) were found to have been sophisticated. B % + B + 3 + 3

ISSN:0003-2654    

DOI:10.1039/AN9083300304

出版商:RSC    

年代:1908

数据来源: RSC