摘要:

JUNE, 1915. Vol. XL., No. 471. THE ANALYST. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS. A JOINT meeting of the Society and of the Biochemical Society was held on Wednesday evening, May 5, in the Chemical Society’s Rooms, Burlington House. The chair was occupied by Mr. A. Chaston Chapman, F.I.C., President of the Society of Public Analysts and other Analytical Chemists.The minutes of the previous meetings of both Societies mere read and confirmed. Certificates of proposal for election to membership of the Society of Public Analysts and other Analytical Chemists in favour of Messrs. E. T. Brewis, F.I.C., P. J. Fryer, and W. McDonnell Mackey, F.I.C., were read for the second time ; and certificates in favour of Messrs. Arthur William Crossley, D.Sc.(Vict.), Ph.D. (Wurzburg), F.R.S., F.I.C., 46, Lindfield Gardens, Rampstead, N. W., Professor of Chemistry at King’s College (University of London) ; Daniel James Davies, B.Sc., 177, Le Marchant Road, St. Johns, Newfoundland, Government Analyst for New- foundland ; Martin Onslow Forster, D.Sc. (Lond.), Ph.D. (Wurzburg), F.R.S., F.I. C., 84, Cornwall Gardens, South Kensington, S.W.; Herbert Jackson, F.I. C., King’s College, Strand, W.C., Daniel1 Professor of Chemistry at King’s College (University of London) ; James Charles Philip, M.A. (Aberdeen), D.Sc. (Aberdeen), Ph.D. {Gottingen), 17, Fairfax Road, Bedford Park, W., Professor of Physical Chemistry at the Imperial College of Science and Technology; William Jackson Pope, MA. (Cantab.), D.Sc.(Manc.), LL.D. (St. Andrews), F.R.S., F.I.C., Holmsdale, Brook- land’s Avenue, Cambridge, Professor of Chemistry in the University of Cambridge ; Frederick Ion Richardson, B.A. (Cantab.), ‘ I Sunning Hill,” Cotham Road, Kew, Melbourne, Australia, assistant to the City Analyst, Melbourne ; and George Henry Warburton, 71, Priory Road, N. W,, analytical and consulting chemist,%vere read for the first time. Sir William Crookes, O.M., D.Sc., P.R.S., P.I.C., and Professor Raphael Meldola, D.Sc., LLB., F.R.S., F.I.C., were elected honorary members ; and Messrs. p.S. Arup, B.Sc., A.I.C., A.C.G.I., F. H. Carr, F.I.C., A. S. Dodd, B.Sc., F.I.C., and H. Heap, N.Sc., F.I.C., were elected members. A discussion took place on “Methods adopted in the Estimation of the Nitrogenous Constituents of Extracts derived from Albuminous Substances, such as Meat Extracts and Similar Products, with Special Reference to the Interpretation of the Results.”272 MACARA: NOTE ON THE ESTIMATION OF CARBONIC ACID The discussion was opened by the Chairman (Mr. A. Chaston Chapman), the other speakers being Professor F. Gowland Hopkins, F.R.S., Dr. E. P. Cathcart, Mr. A. R. Tankard, Mr. E. Hinks, Dr. P. Hartley, Ilr. Rideal, Professor Barger, Professor A. Harden, F.R.S., and Dr. G. S. Walpole.

ISSN:0003-2654    

DOI:10.1039/AN9154000271

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

272 MACARA: NOTE ON THE ESTIMATION OF CARBONIC ACID NOTE ON THE ESTIWIATION OF CARBONIC ACID IN SELF-RAISING FLOURS AND BAKING-POWDERS. BY T. MACARA, F.I.C. (Read a t the Meeting, March 30, 1915.) IN analysing self-raising flours and baking-powders it is customary to estimate the total and available carbonic acid. The former is the carbonic acid liberated from the mixture by the addition of an acid-e.g., hydrochloric acid-and the accurate estimation of its quantity is readily carried out by any of the customary methods.The available carbonic acid is generally assumed to be that liberated on adding water to the mixture, and to be entirely due to the decomposition of the sodium bicarbonate by the acid material present in the mixture. This definition takes no account of the carbonic acid liberated from the excess of sodium bicarbonate (almost invariably present in these mixtures) when heated to the baking temperature.The author considers the true available carbonic acid to be that which ie liberated under the actual conditions of baking. This would include the gas liberated by the acid material present, plus that liberated by any acid present in the flour, milk, or other ingredients used, together with that liberated by the action of heat on the excess of sodium bicarbonate.Obviously it is practically impossible to estimate carbonic acid liberated in all these ways, as we are dealing with three unknown factors-viz., the amount of acid present in the other ingredients, the time, and the temperature of the actual baking-which will affect the extent of the decomposition of the excess of sodium bicarbonate.Tempera- ture will probably be anything from under boiling-point to 150' C. or over. In order to determine how much carbonic acid was liberated from sodium bicarbonate by boiling, a number of experiments were made, and a summary of these is given in the following table : 1 grm. boiled for 6 minutes required 4 C.C.Time may vary from five minutes to as many hours. { - 0-044 grm. CO,. HCl 2 8.41 per cent. of total co,. = 0.0924 grm. CO,. =17-64 per cent. of total CO,. = 0.1122 grm. of GO,. =21.38 per cent. of total CO,. 1 9 9 9 , 10 ,, Y ? 8-4 Y , { 1 9 , 9 , 20 $ 9 Y 9 10.2 9 , ( On boiling for a further- 10 minutes required 2.0 C.C. 20 9 , 2 ) 1.8 Y , =0.0198 ,, =3*7 ,, 9 , Y9 HCl= 0-022 grrn.CO,= 4.20 per cent. of total GO,*IN SELF-RAISING FLOURS AND BAKING-POWDERS 273 I t will be seen from these figures that for the first ten minutes the liberation of carbonic acid is very rapid, and that for each succeeding ten minutes additional boiling about 4 per cent. carbonic acid is obtained. So long as the conditions of the experiment were the same (ie., size of flask, etc.), practically identical results were obtained.It is rather remarkable that, when boiled for thirty minutes, 25.58 per cent. of the total carbonic acid is obtained, and this corresponds with the following equation : 4NaHC0, = Na2C0,,2NaHCO, + H,O + CO,. That is, the bicarbonate rapidly decomposes to form the sesquicarbonate, thus liberating 25 per cent.of the total CO,. The author suggests that, for the valuation of baking-powders and similar preparations, the apparent ” available carbonic acid should be estimated, and he would define this as the amount of carbonic acid liberated on boiling with water only for thirty minutes-ie., the carbonic acid liberated by the action of the acid material, together with 25 per cent. of the carbonic acid present in the excess of bicarbonate. It is evident that the “apparent” available carbonic acid cannot be estimated directly by the Schrotter method, but the Knorr apparatus and method described in Leach might be adapted to the purpose.As the latter process is cumbersome and complicated, the author prefers to use the process described by himself (ANALYST, 1904, 29, 152), which requires no elaborate npparatus, and can be adapted for working with very large or quite small quantities of the sample.I n order to overcome the difficulty arising from frothing when such mixtures are boiled, the process has been slightly modified. For baking-poqders 2 to 5 grms. are used, and for self-raising flour 10 grms. In the case of the former, the process as originally described is usually quite sufficient, but it is generally easier to treat both mixtures alike.Four or five pieces of pumice are added, and the flask closed with the cork and fittings. Into the absorption flask B are placed 50 C.C. of a, saturated soIution of barium hydroxide, and 100 C.C. water (previously well boiled and cooled), and the seal of the safety funnel E is closed with a little barium hydroxide solution coloured with phenolphthale’in. One hundred C.C.of a,lcohol are run into A, and the mixture well shaken to break down any lumps. This is followed by 100 C.O. of water, and the The weighed quantity of the sample is transferred to a dry litre flask, A.274 MACAKA: CARBONIC ACID I N SELF-RAISING FLOURS, ETC. mixture again well shaken. Tho absorption flask should also be shaken if any carbonic acid appears to be passing into it.One hundred C.C. of liquid paraffin are added, and the flask and contents heated over an Argand burner, with frequent shaking until the contents boil briskly. The boiling is continued for fifteen minutes, and, without stopping the operation, about 400 to 500 C.C. of boiling water are care- fully added, and the ebullition continued for a further fifteen minutes.The absorp- tion flask should be kept well shaken during the earlier part of the process, when the gas is passing freely. Under these conditions no carbonic acid will be found in the seal of the safety funnel. A shallow basin of water is placed under the absorp- tion flask when it begins to get hot.At the end of the thirty minutes the flask B is disconnected, and the inlet tube closed, and the contents cooled in running water if necessary. A small funnel is then inserted in the inlet tube, and the excess of barium hydroxide neutralised by adding 20 per cent. hydrochloric acid in slight excess until liquid is slightly acid to phenolphthale'in); $ soda is then run in in sufficient quantity to make the contents just slightly alkaline, and the, flask is once more well shaken, to absorb any carbonic acid which may have been liberated, The stopper is then lifted, and the contents of the safety funnel washed in if necessary.The solution in the flask is carefully neutralised with or Tc hydrochloric acid. Methyl orange is added and the titration completed, taking care to wash down the inlet tube with a little of the acid.If the flask has been kept well shaken during the process of absorption, the barium carbonate can be titrated direct, but some- times a little scale may be formed which cannot be titrated in this way. In such cases it is only necessary to add 3 or 4 C.C. excess of acid, heat for a, few minutes, and titrate back.The same quantity can be used for the estimation of the non-available carbonic acid by adding acid to the residue in A and boiling into another absorption flask. For the total carbonic acid it is not necessary to use alcohol or oil, as on adding 20 to 25 C.C. of hydrochloric acid, and boiling, little frothing takes place. In other respects the process is the same, but the time of boiling is regulated by the time taken for the last appearance of carbonic acid in the absorption flask.It is better in a11 cases to continue boiling the flask, after nearly filling it with boiling water, for about three to five minutes. The following are some results obtained by this process in analysing commercial baking-powders and self-raising flour : BAKING-PO WDERS. I. 11. 111. IV. Apparent available CO, ... 7.52 16.2 11.8 12.8 Non-available CO, ... 2.33 3.2 1.0 0-5 Total ... ... 9.85 19.4 12.8' 13.3 Acid in mixture ... Tartaric Tartaric Cream of Cream of Acid. Acid. Tartar. Tartar and - Tartaric Acid,ESTIMATION OF SULPHIDE AND SULPHATE SULPHUR 275 SELF-RAISING FLOURS. I. 11. 111. IV Apparent available CO, ... 0.60 0.46 0.57 0.58 Total .., ... 0.68 0.49 0.59 0.60 Non-available CO, .", 0.08 0.03 0.02 0.02 - -

ISSN:0003-2654    

DOI:10.1039/AN9154000272

出版商:RSC    

年代:1915

数据来源: RSC

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ESTIMATION OF SULPHIDE AND SULPHATE SULPHUR 275 THE ESTIMATION OF SULPHIDE AND SULPHATE SULPHUR, AND THE ACTION OF SOLVENTS ON VULCANISED RUBBER. BY HENRY P. STEVENS, M.A., PH.D., F.I.C. (Read at the Meeting, M a d 30, 1915.) PART ESTIMATION OF SULPHIDE SULPHUR. MANY technical rubber articles contain metallic sulphides and sulphates the presence of which complicates the estimation of the ‘‘ combined ” sulphur or ‘( coefficient of vulcanisation.” I n the ordinary analytical process the free sulphur and that present a8 substitute are extracted with acetone and alcoholic potash respectively.In the absence of sulphides and sulphates an estimation of sulphur in the residue gives the percentage in combination with the rubber. In the presence of sulphides and sulphates the usual process consists in heating a portion of the residue with high- boiling solvents to destroy the rubber and render it soluble.The sulphur is then estimated in the washed mineral residue. The sulphur is also estimated in another portion of the extracted rubber, and the sulphur combined with the rubber estimated by difference. The method is tedious and unsatisfactory. It has two disadvantages. I n the first place, many vulcanised rubbers are difficult to decompoRe ; they appear to carbonise and cake when heated even at carefully regulated temperatures.Con- sequently the residue, after washing with benzene, contains undissolved organic matter which protects the mineral sulphides . from deoomposition by acid. The heating process can be repeated, but if the first operation is not successful, reheating is usually without effect.Secondly, the method assumes that the vulcanised rubber does not react with basic substances, such as litharge or magnesia, present in the mixings during heating, with the formation of metallic sulphides, although vulcanising temperatures are employed. The method to be described is applicable to those sulphides which are decom- posed by heating with acids.I t is therefore suitable for the estimation of the sulphides of zinc and lead, whether as original constituents of the mixing or formed during vulcanisation. I t thus embraces one of the commonest types of rubber- mixings--namely, that in which litharge is a constituent. In the ordinary way the metallic sulphides present in either vulcanised or unvulcanised rubbers are so pro- tected by the rubber surrounding the mineral particles that the surface only is attacked by prolonged boiling with strong acids, such as hydrochloric acid solution.276 STEVENS : ESTIMATION OF SULPHIDE AND SULPHATE SCTLPHUR, I find, however, that if the vulcanised rubber be first swollen in a suitable solvent in which the aqueous acid is to some extent soluble, the metallic sulphides.such as those of zinc and lead, are easily and completely decomposed. Various solvents have been tried, of which ordinary methylated ether has been found the most suit- able, no doubt partly because vulcanised rubber swells rapidly in this solvent, and because it is miscible to a considerable extent with aqueous hydrochloric acid.Nevertheless, if preferred, benzene or one of the chlorinated hydrocarbons, such as dichlorethylene, etc., can be employed. The hydrogen sulphide liberated is estimated, and from it the percentage of sulphide sulphur can be calculated. The usual method for the estimation of hydrogen sulphide, such as oxidation to sulphuric acid, I have not found satisfactory. By precipitation as zinc sulphide in an excess of a solution of zinc acetate better results were obtained, but I prefer to use a solution of lead acetate.The absorption is very complete, barely a trace of lead sulphide being precipitated in the second wash-bottle. The freshly precipitated and washed sulphide is decomposed by shaking with iodine solution. The apparatus employed is simple, and consists of a Kipp’s apparatus for the production of carbonic acid, connected to a Voigt’s flask of 250 C.C.capacity, The latter consists of a stoppered flask with outlet tube connected to the ground-in stopper. The inlet tube is fused into the side of the flask, nearly reaching to the bottom. In this flask the rubber is decomposed, and the liborated hydrogen sulphide passes directly into two 100 C.C.stoppered absorption bottles containing a solution of lead acetate. Any suitable apparatus, such as a, Corleis flask (“Indiarubber Laboratory Practice,” Caspari, p. 151), can be used in the place of the Voigt’s flask above referred to, but the latter is much simpler, cheaper, and quite as serviceable. The apparatus is worked as follows: Ten to twenty C.C.pure concentrated hydrochloric acid are poured into the Voigt’s flask and covered with a layer of ether, 20 to 30 C.C. being required.* The air is then swept out of the apparatus by means of a current of GO,. This should be &one before joining up the absorptiou flasks, so as to avoid a heavy precipitation of lead carbonate. The stopper is then removed from the flask for a couple of seconds while a weighed quantity of the rubber under examination is dropped in.The quantity taken may be 0.1 grm. to 1 grm., according to the proportion of sulphides the rubber is likely to contain. The absorption flasks are now joined up, and a little more carbonic acid passed through to drive out any traces of air. The whole is then allowed to stand, with occasional shaking, fifteen to thirty minutes for ordinary soft, rubbers, or longer in the case of hardened or very fully cured specimens.During this period the rubber swells and is gradually decom- posed by the acid, with the evolution of hydrogen sulphide. The ether, with the hydrogen sulphide, ie now driven over by gently heating the flask, and the decom- position completed by boiling for a few minutes.Rubbers compounded with litharge or containing sulphides of lead turn white, and heating should not be commenced until all black specks or patches have dis- appeared. After heating, a gentle current of carbonic acid is passed to wash out * If the rubber teiids t o sink in the concentrated aqueous hydrochloric acid, it should first be swollen in ether alone, as when immersed in the acid the swelling action of the ether is relatively slow ; or the specimen may bc wrapped in filter-paper, to keep it afloat in the ether.AND THE ACTION OF SOLVENTS ON VULCANISED RUBBER 277 any remaining traces of hydrogen sulphide from the flask, while the whole is allowed to cool.The contents of the absorption vessels are acidifiea with acetic acid to decompose any carbonate present, and the lead sulphide filtered off cold and well washed on the filter-paper till free from lead salts.I t is transferred while still wet fo ib stoppered flask, and allowed to stand;with occasional shaking,in contact with n, known volume of standard iodine solution. The excess of iodine is then titrated back with thiosulphste, or any other suitable method may be employed for the estimation of the lead sulphide formed.It is preferable to take a portion of the acetone-extracted specimen for this estimation, as it swells faster in the ether, but a portion of the original rubber may be used. As examples, the following may be quoted : 1. Zinc sulphide mixing, suitably vulcanised, of the followiug composition : Rubber (Para), 33 per cent.; sulphur, 10 per cent. ; zinc sulphide, 57 per cect. 0.1 grm. of rubber yielded lead sulphide, which required 11.6 C.C. of & iodine Sulphide sulphur found 18.6 per cent. ; theory, 18-8 per cent. 2. Lead sulphide mixing, vulcanised of the composition : solution. Rubber, 100 parts ; sulphur, 5 parts ; lead sulphide, 7 parts. One grm. of rubber yielded sulphide which required 5-1 C.C.of & iodine Sulphide sulphur found 0.82 per cent. ; theory, 0.84 per cent. Zinc and lead sulphides are only occasionally added as such in the manufacture of rubber goods. It much more frequently happens that they are formed during vnlcanisation by reaction between the sulphur present and the corresponding oxides. This is particularly the case with lead sulphide, as litharge is a very common ingredient of rubber goods, acting as an accelerator and toughening the rubber.It is in the analyses of such'vulcanised rubber goods that the above process is of particular value. The following figures, to which I shall have occasion to refer in a subsequent paper (J. SOC. Chem. Ind.), give duplicate results for a series of rubbers compounded with sulphur and litharge : Series I.First determination ... 0-61 0.70 1-15 1.22 1.28 1-47 1.60 1.70 1.50 Second ,, ... 0.61 0.75 1.19 1.28 1.34 1.44 1-63 1-76 1.44 Mean ... ... ... 0.61 0.73 1.17 1.25 1.31 1-46 1.62 1.73 1.47 solution. Sulphide Sulphur per Cent. 2. 3. 4 . 5 . 6. 7. 8 . 9 . 1 0 . Series II. Sulphide Snlphur per Cent. 2 . 3 . 4 . 5 . 6 . 7 . 8 . 9 . 1 0 . First determination ...0.52 0.67 - - 1-12 1-41 1.70 1.89 1.76 Second ,, ... 0.54 0.70 0.86 1-00 1.15 1-44 1.68 1-83 1.71 Mean ... . . . ... 0.53 0.69 - - 1.13 1-43 1.70 1.86 1-74278 STEVENS : ESTIMATION OF SULPHIDE AND SULPHATE SULPHUR, PART II.-ESTIMATION OF SULPHATE SULPHUR. The reaction between the litharge and sulphur is usually expressed by the following equation : That is to say, for every three parts of sulphide sulphur there is also formed one part of sulphate sulphur.The lead sulphate will be retained in the Voigt’s flask at the end of the reaction partly dissolved in the hydrochloric acid. A number of experi- ments were made by repeatedly extracting the residual rubber with hydrochloric acid, and uniting the extracts and original hydrochloric acid solution.The sulphate was then estimated as barium sulphate. In no instance has the theoretical proportion of sulphate been obtained. Generally the amount of sulphate sulphur did not exceed one-quarter to one-fifth that of the sulphide sulphur present. Although the equation given above represents tbe reaction which takes place between litharge and sulphur in an inert medium, the reaction may be modified in the presence of the caoutchouc hydro- carbon SO that the latter is partially oxidised, with the formation of a larger propor- tion of lead sulphide and a smaller proportion of lead sulphate.This would explain the deficiency in the sulphate formed as shown in the numerous estimations cited. To study the matter as closely as possible, specimens of vulcanised rubber were subjected to repeated extractions with a mixture of hydrochloric acid and ether.When rubber is swollen under these conditions, a small part of the vulcanised rubber passes into solution with the sulphur, with which it is associated or in combination. Figures are given for repeated extractions carried out on two vulcanised rubber mix- ings. At each operation the percentage of vulcanised rubber dissolved in the ether was estimated, as also its sulphur content and the amount of sulphates in the aqueous hydrochloric acid solution.After extraction every few days extending over a period of forty to fifty days, the rubber was allowed to stand with the ether and hydrochloric acid for several months, when the experiments were brought to a conclusion by deter- mining the percentage extract, sulphur as sulphate as above, and also the sulphur content of the residual rubber. The following figures were obtained : 4Pb0 + 2S, = 3PbS + PbSO, Repeated Estraction of Vulcanised Rubber with Ether and Aqueous Hydrochloric Acid.-Table I.Formula of mixture : Rubber . . . ... 89.0 per cent. Sulphur . . . i.. 5.5 ,, Litharge . . . ... 5.5 ,, Vulcanised in steam between cloth.The specimen was first extracted with acetone. Number of extractions ... 1 2 3 4 5 6 7 8 9 Periodof extraction: days 2 3 5 5 7 7 7 14 3months. Etherealextractper cent. 6.9 1.8 4.4 3.8 5.0 3.2 5.0 7.6 23.8 61.5 Sulphur in acid ethereal extract per cent. ... lost 0.03 0.06 0.06 0.08 0.06 0.06 0.15 0.38 0.88 Sulphur in aqueous hydro- chloric acid extract per cent.... ... ... 0.10 trace nil trace trace nil nil nil nil 0.10 Totals.AND THE ACTION OF SOLVENTS ON VULCANISED RUBBER 27‘3 The residual rubber left after extractions (38.5 per cent.) gave 0.80 per cent. combined sulphur, which, together with 0.88 per cent. present in the extracts, gives 1.68 per cent. sulphur in combination with the rubber, and a coefficient of vulcanisa- eion of 1.87.All percentages are calculated on the weight of original vulcanised rubber taken. The figures giving the total extracts, etc., are not of great value, as there is a cumulative error of seven to nine separate determinations. The results are of interest as illustrating the gradual solution of the rubber, together with its proportion of sulphur of vulcanisation.If, after estimation of the sulphide and sulphate sulphur in the manner described, the residual rubber be oxidised, the sulphur in combination with the rubber may be estimated. I n this manner the whole of the.sulphur in a vulcanised compound containing lead or zinc sulphides may be accounted for as follows : 1. The free sulphur by oxidation of the acetone extract. 2. The sulphide sulphur by decomposition with ether and hydrochloric acid, and 3.The sulphate sulphur present in the hydrochloric acid solution. 4. The sulphur combined with rubber by oxidation of the residue. I n illustration, the following analyses of vulcanised litharge mixings may be estimating the hydrogen sulphide evolved. quoted : 1. Free sulphur . . . 2. . Sulphide sulphur 3. Sulphate sulphur 4.Combined sulphur Total ... ... Percentage added PART III.-EXTRACTION Table II. 1. 2. 3. ... ... 1.21 0.48 0.04 ... ... 0.69 1 -00 1.86 ... ... 0.10 0.13 0.34 ... ... 2.11 2.33 0.67 ..- ... 4.11 2-94 2 *91 ... ... 4-20 3-97 3.11 - - OF VULCANISED RUBBER WITH SOLVENTS. I t is generally held that fully vulcauised rubber is not soluble in common solvents, although these have a marked swelling effect.The tables above show that i n the presence of an acid, such as hydrochloric acid, the vulcanised rubber is gradually dissolved even in the cold, and in these cases the rubber dissolved contains about 1.5 per cent. of sulphur. This applies not only to mixings containing litharge, but also to rubber vulcanised with sulphur only, as well as with sulphur and other mineral ingredients.The rubber cannot be recovered physically unchanged from the solution, and the product tends to be ‘ 6 tacky” and viscous. Tables 111. and IV. give the figures obtained in a series of extractions with ether and hydrochloric acid carried out in the same manner as in Table I,, but with a, rubber vulcanised with 4-75 and 7 per cent. of sulphur respectively.280 ESTIMATION OF SULPHIDE AND SULPHATE SULPHUR Table III.Rubber . . . . . 100 parts-95*25 per cent. Sulphur . . . ... 5 parts- 4.75 ,, Formula of mixture : The specimen was first extracted with acetone. No. of extractions ... 1 2 3 4 5 6 7 8 9 Periodofextraction: days 2 3 5 5 7 7 7 14 3months. Totals. Extract per cent. ... 10.3 4.5 6.2 7.1 12.0 12.2 11.1 14.3 18.6 96.3 S in extract per cent.... 0-13 nil 0-07 0.09 0.16 0.12 0.21 0.24 0.36 1-38 The residual rubber left after extractions (3.7 per cent.) gave 0-10 per cent. combined sulphur, which, together with 1.38 pe; cent. present in the extracts, gives 1-48 per cent. sulphur in combination with the rubber, and a coefficient of vulcanisa- tion of 1-55. Table IV. Rubber , . . . . . 93 per cent. Formula of mixture : Sulphur .. . ... 7 ,, The specimen was first extracted with acetone. Number of extractions 1 2 3 4 5 6 7 8 9 10 Periodofextraction: days 2 2 3 6 6 5 7 7 7 14 Totals. Extract per cent. ... 1.20 lost 2.5 6.5 2.5 6.5 6.5 6.8 4-7 16.2 64.2 S in extract per cent. 0.14 lost nil 0.11 0.6 0.11 0-12 0.12 0.7 0.4 1.14 These figures ehow a progressive solvent action, although the flasks were not heated and were kept in a dark.cupboard.A similar effect can be obtained with a mixture of benzene and strong aqueous hydrochloric acid. A sample of rubber vulcanised with sulphur only was extracted with acetone and then treated in the cold for varying periode with fresh quantities of this mixture, with the following results : Per Cent. Bnlphnr Original RnLber.Extract. Per Cent. Sulphur E ~ ~ ~ $ ~ ~ s f . Per Cent. Extract. calculated on calculated on 1 24-25 0.42 1.72 2 37-40 0.80 2.14 3 23.45 0.52 2.23 4 13.80 0.30 2 *18 Total 98-90 2.04 Mean 2.07 -- - Four treatments over a period of a few weeks sufficed to dissolve practically the whole of the rubber. It is noteworthy that the first extract is poorer in sulphur than the later ones.These latter give the same figure of 2.2 per cent., which does not vary appreciably from the average of 2.07 per cent. The solvent action after the first extraction is not selective, and may be taken as an indication that the vulcanised rubber, regarded as a chemical compound, is practically homogeneous.VERSFELD : BROMINE METHOD OF ESTIMATING PHENOL 281 Chlorhydrocarbons act similarly to the mixture of solvents and hydrochloric acid. Dichlorethylene causes the rubber to swell quickly, and on standing for a lengthened period, the rubber partially dissolves. This solvent action may be due to the presence of acid decomposition products in the chlorhydrocarbon.* As a whole, however, the action of the chlorhydrocarbons does not appear to be more rapid than that of a mixture of benzene and acids. Further experiments are in progress to determine the best solvent or combination of solvents for treating the vulcanised rubber. If it is found possible to dissolve the rubber fairly rapidly, a new method of analysis will be opened up for soft rubbers, as the mineral matters will then be separable from the rubber hydrocarbons. Some preliminary experiments with soft rubbers containing a single mineral ingredient have given satisfactory results.

ISSN:0003-2654    

DOI:10.1039/AN9154000275

出版商:RSC    

年代:1915

数据来源: RSC

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VERSFELD : BROMINE METHOD OF ESTIMATING PHENOL 281 BROMINE METHOD OF ESTIMATING PHENOL. BY W. VERSFELD, B.A., DSc, (Read at the Meeting, March 30, 1915.) IT is frequently necessary in this laboratory to estimate the exact strength of solutions containing phenol. The solutions are used as control standards in con- nection with the standardisation of disinfectants, and their strength has usually been determined by means of bromine.The method hitherto employed is a modification of that devised by Koppe- schaar (Zeitsch. anal. Chem., 1876, 15,233), and consists in the action of an excess of bromine on phenol, liberation of iodine from potassium iodide by the unused bromine, and titration of the iodine by standard thiosulphate solution, using starch as indi- cator. The bromine may be used either in the form of bromine water, or may be generated in the solution of phenol by the action of hydrochloric acid on a hypo- bromjte solution or a mixture of bromide and bromate.The hypobromite solution is obtained by saturating sodium or potassium hydroxide with bromine, and boiling off the excess of the latter. This solution, on standing, and particularly when free bromine is present, changes into a mixture of bromide and bromate.Some chemists have aimed at obtaining a solution of bromine sufficiently stable to obviate the necessity of frequent standardising. The only solution which will fulfil this requirement is one made by dissolving potassium bromide and bromate. Redman and Rhodes (J. I d . and Eng. Chem., 1912, 4, 655; ANALYST, 1912, 37, 515) state that hypobromite solution used by them weakened JJ per cent.every day for the first few days after it was made, whereas the bromide-bromate solution was practically permanent, duplicate determinations at intervals of three months giving strengths of 0.09493 N and 0.09495 N respectively. * Owing to the solvent action on the rubber, it is obvious that the chlorhydrocarbons are not suitable for extracting vulcanised rubber as snggested hy Gowing-Scopes (ANALYST, 1914, 39, 19).282 VERSPELD : BROMINE METHOD OF ESTIMATING PHENOL The following method has been used for some time in this laboratory : Two hundred to 250 C.C.NaOH are saturated with bromine water, the excess of bromine expelled by boiling, the solution cooled, made up to a litre, and 100 C.C.used for each 1 C.C. of 5 per cent. phenol or its equivalent. The phenol solution is placed in a glass-stoppered bottle, 100 C.C. of the hypobromite solution and 5 C.C. strong hydrochloric acid added. The contents of the bottle are shaken, and allowed to stand fifteen minutes, 12 C.C. of a 10 per cent, solution of potassium iodide added, again shaken, and stood for five minutes.The solution is diluted to about 500 c.c., and titrated with approximately & thiosulphate, using filtered starch as indicator. A control experiment is treated in the same way. , in which 2.4376~ The percentage of phenol may be calculated from the expression ____ Y GC is the amount of bromine absorbed by 1 C.C. of phenol solution, and y the number of C.C.of & thiosulphate. A solution of phenol was prepared, slightly stronger than 5 per cent., when tested by the above method, and found to be 5.08 per cent. in strength. This was diluted so as to be exactly 5 per cent., and 1 C.C. wag used for each of the estimations described below : 1. One hundred C.C. of bromine water (approximately &) were used; 1 C.C. of the thiosulphate was equivalent to 0.001509 grm.phenol : I ’ Phenol per Gent.. C.C. Thiosulphate used 1 C.C. Thiosnlphate used 1 for Phenol. j for Coiitrol. 20-9 20.8 20.6 I 53.9 54.0 53.9 I . -. . . . - ._ - 33.0 33.2 33.3 4.98 5.01 5.02 I 1 2. A day later the same bromine water was used, but 100 C.C. were then found Two hundred C.C. were used, and an average 3. A potassium bromide solution of bromine gave 4.97, and three days later 4.Successful titrations were also obtained when hypobromite was used, 5 and The same phenol solution, after standing a week longer, gave the following (a) With the same solution of bromine in potassium bromide (approximately &j (b) With the same hypobromite solution as used before (approximately &), These results indicate that- (1) Some change slowly takes place in the phenol solution, involving the forma- insufficient, owing to loss of strength.content of 4.99 per cent. of phenol found. 5 per cent. of phenol. 5-1 per cent. of phenol being found. results : which was previously used, 5-18 per cent. of phenol was found. 5-27 per cent. of phenol was found. tion of compounds having a higher t ( bromine value ” than phenol.VERSFELD : BROMINE METHOD OF ESTIMATING PHENOL 383 (2) Bromine water containing potassium bromide is fairly permanent, as is indicated by the small decrease in the amount of thiosulphate used for the controls. (3) There is v3ry little to choose between the two methods employed, provided proper precautions are observed.The employment of a mixture of potassium bromide and potassium bromate was not tried.It should be pointed out that the estimations were made during cold weather. I t is quite possible that in warm weather the solubility of bromine in water would be affected to such an extent as to render the method less reliable. The addition of potassium bromide, which renders the bromine solution fairly permanent, makes a very considerable difference to the reliability of the method, which certainly has the advantage of being quicker than the other.The variation of results in any particular series of estimations is due mostly to the difficulty of measuring out the small volume (1 c.c.) of phenol solution used. Previous dilation to a known bulk seems advisable. Another possible source of error is the escape of bromine when the flask is opened to introduce the potassium iodide solution.I n view of the results obtained above, it would appear that either method is suitable; but if one method is to be adopted to suit all conditions, hypobromite solution should be employed. The conditions would then be as follows : This quantityis placed in a glass-stoppered flask of 500 to 1,000 C.C. capacity, and diluted with about 50 C.C.water. Five C.C. of strong hydrochloric acid and 100 C.C. of hypo- bromite solution (prepared by saturating 100 C.C. : NaOH with bromine water, boiling till quite colourless, and diluting to 1 litre) are added, the flask shaken well, and allowed to stand for fifteen minutes. The stopper is raised sufficiently to pour in about 20 C.C. potassium iodide solution (10 per cent.), the flask again shaken, stood for five minutes, diluted to 300 or 400 C.C. with water, and titrated with & sodium thiosulphate, using filtered starch as an indicator. A control is carried out in the same way. The difference in C.C. between control and test multiplied by 0*156746 =percentage of phenol, if 1 C.C. was used. The thiosulphate is standardised by adding 20 C.C. K,Cr,07 to a mixture of 10 C.C. XI (10 per cent.) and 5 C.C. strong HCI, and titrating the iodine liberated. For each test a solution containing about 0.05 grm. phenol is used. GOVEKNYENT CHEMICAL LABORATORY, CAPE TOWK.

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DOI:10.1039/AN9154000281

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年代:1915

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284 ABSTRACTS OF CHEMICAL PAPERS ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOOD AND DRUGS ANALYSIS. Characteristics of Ghee. K. H. Vakil. (J. SOC. Chem. I d . , 1915, 34, 320.) -Fresh samples of ghee, mainly from buffalo’s milk, gave the following analytical results : 1. Bombay, A ... 2. ,, B ... 3. ,, c ... 4. ,, D ... 5. Porbunder, A ... 6. ,, B ... 7. Surat, A ... 8. B ... 9. BJiser, A ...10. ,, B ... Average ... Bu tyro - Refrac tometer at 40” C. 44.0 44.2 44.3 45.0 44.8 43.5 44.0 45.0 - - 44.35 Saponification Value. 232 -2 229.8 226.1 231.0 230.0 215.0 227.2 231.0 224.0 220.0 226.9 - Reichert-Meissl Value. . . - -- 23.98 23.43 21.87 23.10 23-76 20.46 25-30 24-63 22.1 1 21.78 - . __ - -. Acid Value. - 1.67 2-24 1-98 1-67 1-68 2.37 1.71 1.49 3.63 2.89 .93.05 1 2.14 C. A. M. In two papers (ANALYST, 1910, 35, 343; 1911, 36, 392), Bolton and Revis have drawn attention to the fact that true ghee usually gives high Reichert-Meissl figures (in the neighbourhood of 30), and that the low figures constantly obtained are usually due to adulteration.-ED. Estimation of Certain Opium Alkaloids by Decomposition of their Nethoxyl Groups. (Zeitsch.anal. Chem., 1914, 53, 673-678.)-Zeisel’s method for the estimation of methoxyl groups (ANALYST, 1886, 11, 119; 1898, 23, 297; 1904, 29, 9) may be applied to the estimation of codeine, thebaine, papaverine, narcotine, and narceine. The quantities of silver iodide yielded by 1 grm. of the respective alkaloids are-Codeine, 0-774 grm. ; thebaine, 1-90 grm. ; narcotine, 2.266 grms.; narceine, 2.110 grms. ; papaverine, 3.187 grms. Narcotine and narceine each contain, apparently, four methoxyl groups, and not three. J. Gsell and B. Marschalko. w. P. s. Oleoresin of Sand Pine. A. W. Schorger. (J. Ind. and Eng. Clzem., 1915, 7, 321-322.)--The sand pine (Pinus clausa) occurs practically nowhere but in Florida, U.S.A. The analysis of the oleoresin was as follows : Volatile oil, 18.9 ; rosin (low- grade), 72.3; trash, 2.7; and water, 6.1 per cent.The volatile oil, on fractionalBACTERIOLOGICAL, PHYSIOLOGICAL, ETC. 285 distillation, was found to come over in two portions-60 per cent. between 1 6 1 O and 165" C., and 35 per cent. between 1 6 5 O and 167" C. The total volatile oil had approximately the following composition : I-a-pinene, 10 per cent.; I-camphene, 10 per cent. ; Z-/3-pinene, 75 per cent.; losses by polymerisation, etc., 5 per cent. The rosin " had an acid number of 172.5, and a saponification number of 178.7. I t yielded 4 per-cent. of resene soluble in petroleum ether, while the remainder consists mainly of abietic acid. H. F. E. H. Melting and Solidifying Point of Thymol. R. Meldrum. (Chem. News; 1915, 111, 193-195.)-The melting-point of thymol is stated by many authorities to be 44' C., and by others 50" C. It was found that the solidifying-point of thymol varies between 48.2" and 49.2' C., the variation being due to the size of bore of the test- tube employed, and also to absorption of moisture by the thymol. The higher figure is to be accepted, as it approaches more nearly the melting-point, which varies from 49" to 50' C., according to the method by which it is determined. H. F. E. H.

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DOI:10.1039/AN9154000284

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年代:1915

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BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. 285 BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. Estimation of Total Nitrogen in Urine, especially in the Presence of Sugar. E. Justin-Mueller. (J. Pharnz. Chim., 1915,11,171-174.)-Ten C.C. of the urine are heated with 5 C.C. of 30 per cent. potassium oxalate solution in a 250 C.C. flask, and a quantity of sulphuric acid added corresponding to the amount of sugar present, and calculated by the formula 5+ps where 5 represents the normal quantity of aoid, and nS the quantity of sugar in grms.per litre of urine. Hydrogen peroxide is then slowly added until effervescence stops, the flame then lowered, and the remainder of the hydrogen peroxide required to oxidise the sugar is introduced. The total quantity is calculated by the formula -- = C.C. .I2 vol.hydrogen peroxide, where rtS represents the sugar in grms. per litre. All difficulties due to frothing are thus obviated. 10 ’ nS 2 The ammonia is distilled in the usual way. C. A. M. Organic Phosphoric Acid of Wheat. G. Clarke. (J. Chem. Soc., 1915, 107, 360.)-A white amorphous substance, approximating to the composition cor- responding to the formula C,,H2,O4,P,,Ca7Mg, was separated from wheat, the yield being 0.14 per dent.on the air-dried grain. The substance resembles, both in chemical and physical properties, but is not identical with phytin prepared by the author from mustard (J. Chem. SOL, 1914, 105, 535). I t is a mixture of at least two sub- stances, differing slightly in their solubility in boiling dilute acetic acid. G. C. J.Experiments with Abderhalden’s Method for the Early Recognition of Pregnancy. A. Campus. (Clin. Vet. Rass. di Pol. Sun. e di Igiene, 1914, 20, 847-867; through Zonthly Bull. Agric. Intell. and Plant Diseases, 1915, 6, 103.)- The author draws the following conclusions from his experiments : (1) The reaction gives positive results in 100 per cent. of cases if the animals are pregnant,286 ABSTRACTS OF CHEMICAL PAPERS while the results are negative with diseased or normal non-pregnant subjects.(2) A positive result may be obtained as early as fourteen days after fertilisation, and is independent of the stage of pregnancy. (3) The effects of the proteolytic enzymes engendered as a result of pregnancy are not confined to any specific kind of placenta. The work was carried out on seventy-two animals, comprising cows, mares, ewes, sows, goats, and rabbits.The proteolytic enzyme was not found to lose its activity if the sterile serum is kept for as long as a month at a low tempera- ture. (Cf. ANALYST, 1914, 39, 177, and ANALYST, 1915, 156.) H. F. E. H. Atmosphere of the Soil : Its Composition and the Causes of Variation. E. J. Russell and A.Appleyard. (J. Agric. Sci., 1915, 7, 1-48.)-The free air present in the soil to a depth of six inches is very similar in composition to atmospheric air ; but it differs in two respects : (1) It contains more carbonic acid and correspondingly less oxygen, the average in 100 volumes being 0.25 volume carbonic acid and 20.6 of oxygen against 0.03 volume carbonic acid and 20.96 oxygen in atmospheric air ; (2) it shows greater fluctuations in composition.Usually the sum of carbonic acid and oxygen is only slightly less than in atmospheric air ; but at periods when nitrates rapidly increase there is a perceptible falling-off of oxygen, and a still greater one in water-logged soils. Besides this free air there is another atmosphere dissolved in the water and colloids of the soils.This consists mainly of carbonic acid and nitrogen, and has practically no oxygen. The fluctua- tions in composition of the free soil air are mainly due to fluctuations in the rate of biochemical change in the soil, the curves being similar to those showing the amount of nitrate and the bacterial counts as far as they were taken. The rate of biochemical activity attains a maximum value in late spring and again in autumn, and minimum vdlues in summer and winter.In autumn the bacteria increase first, then the carbonic acid rises, and finally the nitrate increases. From November to May the curves closely follow those for the soil temperature, which appears to be the dominating factor ; from May to November they follow the rainfall and, to a less extent, the soil moisture curves.The distinct difference between rainfall and soil moisture indicates that rainfall does something more than add water to the soil. It is shown that the dissolved oxygen brought in is probably a factor of considerable importance in renewing the dissolved soil atmosphere and facilitating biochemical change. Grass land usually contains more carbonic acid and less oxygen than arable land, but the difference cannot be attributed to the crop owing to the large differences in soil composition and conditions.The precise effect of any crop is difficult to ascertain, but as the soil differences are eliminated, so the differences in composition of the soil air become less and less. No evidence could be obtained that the growing crop markedly increases the amount of carbonic acid in the soil air, and if it gives rise to any great evolution of carbonic acid in the soil, it apparently exercises a corresponding depressing effect in the activities of soil bacteria. Weather conditions, such as barometric pressure, wind velocity, variations in temperature from the mean, small rainfall, etc., appear to exercise but little effect on the soil atmosphere. H. F. E. H.

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年代:1915

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ORGANIC ANALYSIS 287 ORGANIC ANALYSIS. Use of 4-4-Diphenylsemicarbazide in the Detection of Carbonyl Derivatives. B. Toschi and A. Angiolani. (Gazz. Chim. Ital., 1915, 45, 205- 213.)-Stable crystals of 4-4-diphenylsemicarbazide, (CGH&N .CO.NH.NH,, are readily obtained by mixing an alcoholic solution of commercial diphenyl-urea chloride with hydrazine hydrate in equimolecular proportions. I t reacts with carbonyl derivatives readily, and forms diphenylsemicarbazones, which are much less soluble than the corresponding semicarbazones.The diphenylsemicarbazones of aliphatic compounds are obtained by adding their aqueous or dilute alcoholic solution to an aqueous solution of the free base or its hydrochloride. The aromatic diphenyl- semicarbazones are readily hydrolysed by boiling with dilute acids.They dissolve in concentrated sulphuric acid, with characteristic coloration. Among the diphenyl- semicarbazones prepared were those of the following compounds : Acetone (m.-pt. 119" C.) ; acetaldehyde (153" C.) ; dextrose (164"-166" C.) ; cinnamic aldehyde (164"-166" 0.) ; salicylic' aldehyde (209" C.) ; vanillin (180"-181" C.) ; citronella1 (109"-110" C.); and camphor (154"-155" C.).C. A. M. Estimation of Cane Sugar by Double Polarisation, employing a New Method of Clarification. N. Deerr. (Intern. Sugar J., 1915,17,179-182; through J. SOC. Chem. Ind., 1915, 34, 503.)-To eliminate the error caused by the direct reading being takeh in an alkaline solution (due to basic lead acetate) and the inver- sion reading in a strongly acid medium (due to hydrochloric acid), the author takes the two readings in solutions having the same composition so far as non-sugars are concerned.Clarification of both solutions is effected by adding successively baryta and a mixture of aluminium sulphate and sulphuric acid, the small amount of sulphuric acid remaining in solution after the separation of the aluminium hydroxide and barium sulphate being insufficient to induce appreciable hydrolysis while taking the direct reading, but being sufficient to invert all the sucrose present a t a high temperature. The solutions required are-(a) A 0.52 N solution of baryta; (b) a solution of 165 grms.of crystallised aluminium sulphate and 135 C.C. of sulphuric acid per litre ; the titre of (b) is adjusted so that 25 C.C.of (a) are equivalent to 15 C.C. of (b). For the direct reading, 50 C.C. of the material under examination (containing 3.25 grms. in the case of cane molasses) are mixed with 25 C.C. of (a) and next with 15 C.C. of (b), the volume being completed to 100 c.c., and about 0.1 grm. of sodium hydrosulphite added. After filtering, the solution is polarised, the reading being increased by 0.7 per cent.to compensate for the volume of precipitate formed, or the volume may be completed to 100.7 c.c., instead of 100 C.C. For the inversion reading, 50 C.C. of the same solution of the material used for the direct reading are treated in a 100 C.C. flask with 15 C.C. of (b), and inversion effected at 95" to 97" C. during twenty minutes. After cooling, 25 C.C.of (a) are added, the volume made up to 100 c.c., the liquid filtered, and the saccharimeter reading ascertained, while from the direct and inversion readings is calculated the percentage of sucrose from the usual formula, a special constant, however, being used. Advantages of the proposed process, in addition to both readings being made under identical conditions, are that the influence288 ABSTRACTS OF CHEMICAL PAPERS of the lead salts is eliminated, and that the filtrate may be used for the determina- tion of the reducing sugars.On the other hand, in comparison with the ordinary procedure, its disadvantages are that the decolorisation is less intense (though reasonably efficient), and that the time required is somewhat greater. Constitution of the Glycerophosphoric Acid of Lecithin.0. Bailly. (Comptes rend., 1915, 160, 395-398.)-The alkaline hydrolysis of egg lecithin yielded 23-25 per cent. of calcium glycerophosphate with the composition of the calcium salt of a mono ester of glycerophosphoric acid, P0,Ca.C3H,(OH),. The solubility of this salt (2.88 per cent. at 1 2 . 5 O C.) was intermediate between that of the calcium salt prepared from crystalline sodium glycerophosphate (1-78 per cent.) and that of the calcium salt prepared from the uncrystallisable residue left in the preparation of the crystalline salt.The former was identified as calcium 8-glycerophosphate, while the latter consisted largely of calcium a-glycerophosphate. The crystalline sodium salt prepared from the lecithin calcium glycerophosphate yielded, when oxidised, only traces of phosphoric dioxyamtone (characteristic of the B-compound), while the mother liquor yielded this oxidation derivative in abundance (characteristic of the a-compound). Egg lecithin, therefore, consists of a mixture of at least two isomeric compounds with the following constitutional formulae, in which R represents a fatty acid radicle : OH C2H4<N (CH& 0 I I CH.0 HO-P=O I I CH2.O HO-P=O i I CH. - OB CH2- OZZ Lecithin a./\ CH2.0R CELOB Lecithin @. c. A. M. Method of Distinguishing between the Mono Esters of Glycero- phosphoric Acid. L. Grimbert and 0. Bailly. (J. Pharm. Chim., 1915, 11, 153-157.)-0n oxidising a-monoglycerophosphoric acid (0.25 grm.) by heating it with 10 C.C. of 0.25 per cent.bromine water, it yields a substance of the general formula, R.CO.CH,OH. This can be distinguished by the reactions of Denigds (Comptes rend., 1909, 148, 172, 282) from the product of the oxidation of the P-acid. Thus it gives a blood-red coloration with phloroglucinol and sulphuric acid, which the other does not ; while the @-derivative reduces Nessler’s and Fehling’s solutions in the cold, By these tests it was proved that the crystalline sodium glycerophosphate prepared by Poulenc’s process (Fr.Pat. 373112,1906) consists of the salt of p-mono- glycerophosphoric acid, the secondary alcoholic grouping of which is not trans- formed by oxidation into a ketonio grouping. C. A. M.ORGANIC ANALYSIS 289 Use of Hydrochloric Acid in the Estimation of Certain Forms of Organic Nitrogen.W. A. Drushel and M. M. Brandegee. (Amer. J. Sci., 1915, 39, 398-404; through J. SOC. Chem. Ind., 1915, 34, 514.)-The following method is proposed for the estimation of nitrogen in aliphatic nitriles, cyanogen-substituted esters, amides, and imides : 0.1 to 0-3 grm. of the substance is heated with 3 C.C. of hydrochloric acid of sp. gr. about 1.2 for two hours at about 200' C.in a sealed tube. A considerable pressure of carbon dioxide is developed in some ca8es. The product is rinsed out into a basin, evaporated to dryness, further heated for fifteen minutes on a water-bath, and afterwards for five minutes in an oven at about 110' C. By this means all free hydrochloric acid is eliminated without any appreciable loss of ammonium chloride, and the latter is then determined by titration with silver nitrate solution in presence of potassium chromate.The presence of acetic acid or its homologues does not affect the action of the chromate indicator; but if stronger acids, such as succinic acid, are present, it is advisable to add a very small quantity of sodium acetate-preferably before the addition of the indicator.Tested on acetonitrile, propionitrile, propionamide, succinimide, and the ethyl esters of a-cyano-acetic, -propionic and -butyric acids and n-dipropylcyanoacetic acid, the method gave exact results, except with cyanoacetic acid, which was probably not pure. Accurate results were also obtained with glycine, but only after heating for three to four hours at about 200' C.Qualitative Separation and Identification of Some Oxymethylanthra- quinones. E. M. Bailey. (Amer. J. of Pharm., 1915, 87, 145-154.)-0xy- methylanthraquinones are more or less characteristic constituents of the common cathartic drugs--e.g., senna, rhubarb, aloes, buckthorn, etc.-the principal re- presentatives being dioxymethyl and trioxymethyl derivatives, in the form of chrysophanic acid and ernodin respectively.The pink alkaline solution of chryso- phanic acid is decolourised by zinc dust and the colour returns by reoxidation on exposure to air or by treatment' with a few drops of hydrogen peroxide. This distinguishes it from phenolphthalein. To obtain the mixed colour principles from the drugs, 25 C.C. of the fluid extract are evaporated, taken up with 25 C.C.of water, and treated with excess of normal lead acetate. The lead precipitate is collected on a filter and digested for one hour with 10 per cent. sulphnric acid in the boiling water-bath. The liquid is filtered hot and the fiItrate extracted with hot benzene. I n the case of powdered drugs, 3 grms. of the sample are boiled with alcoholic potassium hydroxide for an hour, the alcohol is evaporated, the residue diluted with 50 C.C.of water, acidified, and extracted with hot benzene. The benzene solution is shaken out first with 25 C.C. portions of 5 per cent. ammonium carbonate solution until the washings are colourless. This removes unidentified anthraquinone derivatives. I t is next shaken similarly with 5 per cent. sodium carbonate until the washings come away pink.This removes the emodin fraction. Lastly, it is shaken with 5 per cent. sodium hydroxide, which takes out the chrysophauic acid. The three alkaline extracts are separately acidified and shakon out with ether, and the ethereal residues examined as to crystalline form and melting-point. The most important test is the colour reaction. The residue from ether is moistened with 4 to 5 drops of concen-290 ABSTRACTS OF CHEMICAL PAPERS trated sulphuric acid, then with 1 to 2 drops of strong nitric acid, and finally diluted with 1 C.C.of water. The emodin residue extracted by sodium carbonate from buck- thorn, rhubarb, and senna, shows with sulphuric acid alone a pink coloration, turn- ing yellow with nitric acid, and giving a pink solution when diluted. The similar fraction extracted from aloes shows with sulphuric acid red, then becomes brownish, turning yellow, with nitric acid, and giving a yellow solution on dilution.Chrysophanic acid (sodium hydroxide fraction) from all sources shows orange-red with sulphuric acid, yellow with nitric acid, and a yellow solution and precipitate on dilution. The unidentified oxymethylauthraquinones extracted from the benzene solution by ammonium carbonate show with sulphuric acid purple or violet, with nitric acid yellow, and a yellow solution on dilution.J. F. B. Tests for distinguishing Parchment Paper from Pergamyn Paper. G. Annoni and G. Rodano. (L’InrE. Chim., 1915, 2, 129; through J. SOC. Chem. Ind., 1915, 34, 487.)-True parchment paper, prepared by the action of sulphuric acid on rag paper, is resistant to boiling water and to a boiling 2 per cent.aolution of potassium carbonate, whereas the imitation pergamyn papers, prepared by mecbanical treatment of wood-pulp, are much less resistant to water and are immediately disintegrated by a boiling 2 per cent. solution of potassium carbonate. On treatment with a drop of ziuc chloride-iodine solution, a violet .stain is produced on both kinds of paper, though more slowly on the pergamyn; but on subsequent treatment with water the violet changes to an intense blue-due to hydrocellulose- in the case of parohment paper, whilst only a faint violet coloration is left on pergamyn paper.Pergamyq papers invariably contain resin, whilst this is absent from parchment papers ; hence the production of a reddish-violet coloration on applying Morawski’s reaction-treatment with acetic anhydride and sulphuric acid in succession-is a proof that the sample is a pergainyn paper.Colour Reaction for Salicylic Acid. P. A. W. Self. (PharTn. J., 1915, 94, 521.)-The usual colour tests for salicylic acid, although extremely delicate, are none of them perfectly characteristic; the author has found, however, that by combining Robert’s test with Mandelin’s, a series of colour-changes is obtained which is quite distinctive for salicylic acid and salicylates. The reagent is made by mixing equal volumes of 40 per cent.formaldehyde solution an2 concentrated sulphuric acid and cooling the mixture; a portion of the substance to be tested is moistened in a porcelain dish with this mixture; a littlo ammonium vanadate is added and stirred up.If salicylic acid is present, a Prussian blue colour appears immediately, rapidly changing to greenish-blue, and finally to green. If no sub- stance capable of yielding a colour reaction is present, the colour given by the reagents alone is yellowish-red or orange, changing after two or three minutes to greenish-yellow, and finally to green.The quantities of reagents should bo adjusted according to the amount of substanca to be tested; for a small trace, not more than sufficient liquid to moisten it should be taken, and only a fraution of a mgrm. of the vanadate. With about 1 mgrm. of salicylic acid, 2 drops of the formaldehyde and sulphuric aoid mixture and 2 or 3 mgrms. of ammonium vanadate are suitable.INORGANIC ANALYSIS 291 A very distinct colour is afforded by 0.02 mgrm. of salicyIic acid. A large number of substances, mostly of phenolic constitution, have been tested; many of these give colorations first on moistening with the acid reagent and again on the addition of the vanadate. The only substance giving the same blue coloration as salicylic acid is salicylic aldehyde, but this is differentiated by the formation of a yellow coloration when moistened with the formaldehyde-sulphuric acid mixture before the vsnadate is added. In testing solutions, the liquid is acidified, shaken out with a volatile solvent, and the extract evaporated with the addition of a trace of alkali. Methyl salicylate reacts as a salt of salicylic acid. J. F. €3.

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DOI:10.1039/AN9154000287

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年代:1915

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INORGANIC ANALYSIS 291 INORGANIC ANALYSIS. Separation and Estimation of Aluminium in Presence of Iron by the Action of Acetyl Chloride in Acetone. H. D. Minnig. (Amer. J. Sci., 39, 197 ; through Chern. News, 1915, 111, 172-173.) - The sparing solubility of certain chlorides--e.g., barium chloride and aluminium chloride in a saturated solution of hydrochloric acid in presence of ether or acetone-forms the basis of methods of separation by precipitation of the chlorides. For the separation of aluminium chloride from ferric chloride, acetyl chloride serves as the source of hydrochlorio acid, and the reagent consists of a mixture of four parts of acetone to one part of acetyl chloride.The solution containing ferric and aluminium chloride is evaporated on the water-bath to the smallest possible volume ; the concentrated solution is cooled, and the acetone-acetyl chloride mixture is added drop by drop while stirring, 15 to 20 C.C.being required. The precipitate is collected in a perforated crucible, washed with the precipitating mixture, dried at some distance above a Bunsen flame for ten to fifteen minutes, and then converted into the oxide by ignition. With small quantities of aluminium chloride (about 0.02 grm.of aluminium oxide) the results are perfectly satisfactory, but the subsequent estimation of the iron in the filtrate is affected by the presence of phosphoric acid introduced as an im- purity in tho commercial acetyl chloride. With larger quantities of aluminium (0.05 to 0.18 grm. of the oxide), the precipitated aluminium chloride also tends to contaia phosphate, owing to the larger quantity of precipitating agent required.Pure acetyl chloride may be prepared by passing a rapid stream of hydrogen chloride through a mixture of glacial acetic acid and phosphorus pentoxide, or, preferably, through acetic anhydride at 100' C., which has been purified by distillation over sodium acetate.J. F. B. Estimation of Carbon Dioxide in Minerals. L. H. Borgestrom. (Zeitsch. anal. Chenz., 1914, 53, 685-687.)-1n the estimation of oarbon dioxide in minerals, such as scapolite, the addition of a small quantity of hydrofluoric acid to the hydro- chloric acid used for the decomposition of the carbonates accelerates the rate at which the mineral is dissolved, and causes the whole of the carbon dioxide to be evolved in a comparatively short time (about fifteen minutes).The results obtrtingd are higher and more concordant than when hydrochloric acid ie used alone. The292 ABSTRACTS OF CHEMTCAL PAPERS hydrofluoric acid attacks the flask to some extent, but the same flask may be used for a considerable number of estimations. w. P. s. Estimation of Carbon and Phosphorus in Cerium and Cerium Alloys. H.Arnold. (Zeitsch. and. Chem., 1914, 53, 678-682.)-The total quantity of carbon is estimated by oxidation with a mixture of chromic acid and sulphuric acid. An explosion is, however, liable to occur when cerium is brought into contact with the oxidising mixture unless the following procedure is adopted : Five grms. of the metal are placed in the evolution flask and 60 C.C.of a 20 per cent. copper sulphate solution are added. The metal is disintegrated gradually and coated with copper. The small quantity of hydrocarbon gases liberated at this stage is burnt to carbon dioxide by passing it over heated platinised asbestos. After about one hour 30 C.C. of chromic acid solution (720 grms. of chromic acid in 700 C.C.of water) are added, followed by the gradual addition of a mixture of 100 C.C. of sulphuric acid and 235 C.C. of water. The whole mixture is then boiled for two to three hours, and the process carried out as in the estimation of carbon in iron or steel. Free carbon is estimated by dissolving 10 grms. of the metal in 100 C.C. of 30 per cent. copper chloride solution, adding 100 C.C.of ferric chloride solution (125 grms. of ferric chloride dissolved in 150 C.C. of water and 100 C.C. of hydrochloric acid), and collecting the insoluble residue containing the carbon on an asbestos filter. The filter and its contents are washed and the carbon then estimated by oxidation with chromic acid and sulphuric acid. The phosphorus is estimated by dissolving 10 grms.of the metal in nitric acid, neutralising the solution, and precipitating the rare earths as oxaIates. The filtrate from the latter is evaporated, the excess of oxalic acid decomposed by heating with nitric acid, and the phosphoric acid precipitated with molybdic acid reagent. Four samples of cerium examiued con- tained-total carbon, 0.058 to 0.150 per cent. ; free carbon, 0-037 to 0.074 per cent.; carbide, 0.031 to 0.076 per cent.; phosphorus, a trace to 0.059 per cent. w. P. s. Sensitive Reaction of Chromates. P. N. van Eck. (Chem. WeekbZud, 1915, 12, 6-8.)-Sohtions of chromates give an intense blue coloration with a-naphthylamine in the presence of a little tartaric, citric, or oxalic acid. Tbe reagent is prepared by grinding 0.5 grm. of a-naphthylamine with 50 grms.of tartaric acid in a mortar and dissolving the mixture in 100 C.C. of water. I t will detect 0.001 mgrm. of chromium in the form of chromate. I t may also be used for the colorimetric estimation of chromium, the standard soIution used for the comparison consisting of potassium chromate (0.373 grm.tper litre ; 1 C.C. = 0-1 mgrm. of chromium). Chromic oxide may be fused with sodium carbonate and potassium chlorate, and the coloration obtained in the test matched with that of a solution of chromate prepared in the same way from pure chromic oxide.C. A. M. Volumetric Estimation of Cobalt in the Presence of Nickel. A. Metzl. (Zeitsch. anal. Chem., 1914, 53, 537-541.)- The cobalt and nickel solution, which should not measure more than 100 c.c., is treated with 15 C.C.of 10 per cent.INORGANIC ANALYSIS 293 hydrogen peroxide, 30 C.C. of 5 per cent. sodium bicarbonate solution, and 30 C.C. of sodium hydroxide solution. The mixture is shaken, heated for twenty minutes to destroy the excess of hydrogen peroxide, the precipitate then dissolved by the addition of potassium iodide and sulphuric acid, and the liberated iodine titrated with thiosulphate solution.One molecule of iodine is equivalent to 1 molecule of cobalt. An alternative method depends on the different behaviour of cobalt and nickel towards a mixture of ammonia, ammonium chloride, and an oxidising substance. The solution containing the two metals is treated with 10 C.C. of 16.6 per cent. ammonium chloride solution, 10 C.C. of ammonia, and 20 C.C.of 10 per cent. hydrogen peroxide, then heated for ten minutes ; 50 C.C. of 25 per cent. potassium hydroxide solution are next added, and the solution boiled for about forty-five minutes, or until all the ammonia has been expelled, water being added from time to time to compensate for loss by evaporation. The quantities of reagents mentioned are required for each 0.1 grm.of cobalt present. After cooling, the solution is treated with potassium iodide, acidified, and the liberated iodine titrated. The cobalt precipitate dissolves slowly, and the mixture should be shaken for about fifteen minutes after the addition of the potassium iodide and acid. Results are recorded which show that the method is accurate. w. P. s. Etching Reagents and their Application.0. F. Hudson. (J. Institute ofMetaZs, 1915, advance proof, p. 22.)-This paper was prepared at the suggestion of the Publioation Committee of the Institute, and in its preparation the author received assistance from a number of well-known metallographists. The merits of the various etching reagents are discussed in such a manner that the reader can have no difficulty in selecting a reagent suitable for any particular metallographic purpose, and will as a rule select the best.The method capable of giving the best results in practical hands, however, is not always the best where experience is lacking, and the paper, as its title implies, deals very fully with the application of etching reagents, on which success so much depends, as well as with their com- position.It also deals generally with the preparation of the specimen in order to bring it into a condition suitable for etching, and with the developments of heat- tinting by Stead. Chief prominence is given to the ebching of non-ferrous metals and alloys, but the most important of the reagents used for iron and steel are dealt with briefly. Some space is devoted to methods of polish attack, which the author believes to be deserving of more attention than is generally bestowed on them.No ordinary abstract of this paper, with its carefully balanced statement of conflicting views of eminent experts, is possible. G. C. J. Separation of Gold and Platinum from Other Metals. A. Christensen. (Zeitsch. ana2. Chem., 191’5, 54, 158, 159.)-The method depends on the reduction of gold and platinum by means of hydrazine hydrochloride; gold is reduced in the cold, whilst platinum is reduced only when the mixture is heated.The solution containing gold and platinum and other metals is treated with an excess of hydra- zine hydrochloride and heated for one hour on a water-bath. The precipitated gold294 ABSTRACTS OF CHEMICAL PAPERS and platinum are collected, washed with hot nitric acid to remove mercury and traces of copper, then dissolved in aqua regia, and identified by the usual tests.Metals other than gold and platinum, even arsenic, antimony, and tin, are not precipitated by the reagent. The filtrate from the gold and platinum precipitate may be used for the detection of the presence of other metals; if Petersen's method (ANALYST, 1910, 35, 369) is used for this purpose,'the excess of hydrazine hydro- chloride must be removed previously by evaporating the solution and igniting the residue.w. P. s. Corrosion of Non-Ferrous Alloys. C. H. Deseh. (J. SOC. Chem. Id., 1915, 34, 258-261,)-The defects of laboratory tests, and especially of accelerated tests, are discussed, and a new method is described which is rapid, applicable to small Epecimens, and suitable for the investigation of adherent films.I n the case of alloys composed of two or more micrographic constituents, it was also thought desirable to observe the relative rate of corrosion of those constituents. For this purpose it was deoided to use specimens of,the size usually adopted for metallographic examination, having a polished surface suitable for direct observation by means of the microscope. Further, it was thought advisable to assist and regulate the corrosion by the applica- tion of an external electromotive force.Objections have been urged against such a procedure, on the ground that chemical and electrolytic corrosion are different in character, but experimental evidence is adduced by the author which shows clearly that the mechanism of the two processes is identical, whilst the conditions of a, rapid laboratory test, cannot be fulfilled without the aid of an applied electro-motive force.The vertical brass rod of a stand is divided into two parts, insulated from one another by a short section of ebonite. The lower rod carries a brass plate which may be clamp3d at any height, and a binding Bcrew for connection with the positive pole of some source of electrical energy, usually a storage battery, provided with a distributing board and measuring instruments for electrolytic analysis.To the brass plate is attaqhed a brass block, carrying a pair of spring clips, between which the specimen, 12.5 mm. square, is held with the polished horizontal surface upwards. The cathode is a piece of fine platinum gauze, 10 mrn.square, attached to a vertical wire suspended from the outer end of a brass arm attached to the upper half of the vertical brass rod of the stand by means of a sliding plate whicb can be raised or lowered by a rack and pinion, a scale allowing the height to be adjusted accurately.The cathode is lowered until in cQntact with the specimen, and then raised 5 mm. A wall of plasticine is built up to contain the electrolyte, which is usually 1 or 2 C.C. of a 5 per cent. solution of sodium chloride. Corrosion is allowed to proceed for five to sixty minutes, according to circumstances. The wirea are disconnected and the electrolyte is rinsed out of the plasticine cell into a beaker, using a wash-bottle With a fine jet. A loose, flocculent precipitate is usually obtained.Any solid deposit adhering to the corroded Burface so loosely that, it is detached by light rubbing with the finger-tip may usually be added to the bulk : but a firmly adherent deposit, requiring the use of a wooden chisel-edge or a knife-blade to detach it, should be collected, if present, for separate A special apparatus is figured in the paper.INORGANIC ANALYSIS 295 analysis The surface of the corroded metal is examined under the microscope both before and after the removal of the adherent layer.The results of experiments with various brasses are given in the paper, together with the conclusions that may be drawn from them, among them the conclusion that the process of corrosion by sea and other natural waters is of essentially the same character as that of electrolytically stimulated corrosion under the conditions described above.G. C. J. Comparison of Methods for the Analysis of the Higher Lead Oxides. J. Milbauer and B. Pivnicka. (Zeitsch. anal. Chem., 1914,53, 569-580.)-Bunsen’s methoa, which depends on the reaction PbO, + 4HC1= PbCI, + 2H,O + GI2, yields results which are at the most 0.1 per cent.too low. The modification of LUX’S method described by Chwala and Colle (ANALYST, 1911, 36, 366) tends to give results which are slightly too low, whilst the figures obtained by Finzi and Rapuzzi’s method (ANALYST, 1913, 38, 343) are too high by about 1.4 per cent. The authors have endeavoured to estimate lead dioxide gasometrically by a process based on the reaction YbO, + 2NB,OH + 2KOH = Pb(OK), + 4H,O + N, ; the reaction proceeds in the cold, but the results obtained are invariably too low, owing to the retention of nitrogen by the reacting solution.w. P. s. Analysis of Litharge. P. Beek. (Zeitsch. anal. Chenz, 1915, 54, 137-147.)- A complete analysis of litharge is seldom required when the material is to be used for technical purposes, but the estimation of certain impurities contained in most specimens of litharge is of importance. For the estimation of copper, 100 grms.of the sample are dissolved in nitric acid, the lead is precipitated as sulphate and separated, and the solution is then diluted to 1 litre. According to the amount of copper present, a quantity of this solution, varying from 10 to 100 c.c., is treated with an excess of ammonia, aluminium and ferric hydroxides are separated by filtration, the filtrate is acidified with dilute sulphuric acid, and the copper deposited electro- lytically.If the colour of the deposited copper indicates the presence of other metals, the metal is dissolved in nitric acid, the solution treated with ammonia and ammonium carbonate, any precipitate (bismuth hydroxide) which forms is separated, and the copper again deposited electrolytically.Litharge for use in pottery and glass manufacture should not contain more than 0.004 per cent. of copper, or more than 0*006 per cent. of iron. These two impurities may be estimated in one portion of the sample as follows : One hundred grms. of the litharge are dissolved in nitric acid, the lead is precipitated as sulphate, washed with dilute nitric acid, and the filtrate and washings are evaporated and heated until fumes of sulphuric acid are given off; after dilution, the solution is filtered to remove any lead sulphate, and the copper precipitated as sulphide in the filtrate.The copper sulphide is collected, dissolved in nitric acid, evaporated with sulphuric acid, any traces of lead sulphate are separated, bismuth is removed by treatment with ammonia and ammonium carbonate, and the copper is again precipitated as sulphide, ignited, and weighed as oxide.The iron, contained in the filtrate from the first copper sulphide precipitate, is estimated gravimetrically in the usual way.296 ABSTRACTS OF CHEMICAL PAPERS Litharge intended for use in the manufacture of accumulators should be free from nitrites and nitrates, and should contain not more than traces of iron, copper, or other metals precipitated by hydrogen sulphide; the chlorine content should not exceed 0.05 per cent.The quantity of metallic lead in litharge may be estimated by mixing 100 grms.of the sample with 700 C.C. of water, adding 70 C.C. of nitric acid (sp. gr. 1.4) in small quantities at a time 80 that the solution does not become heated, collecting the insoluble metallic lead on a filter, then dissolving it in hot dilute nitric acid, and estimating it electrolytically or gravimetrically. Insoluble substances- e.g., lead sulphate, silica, etc.-are best estimated by heating 100 grms.of the litharge with 750 C.C. of water and 80 C.C. of nitric acid (sp. gr. 1.4) until lead oxide, metallic lead, etc., have dissolved, and collecting the insoluble portion on a filter ; the filter and its contents are washed six times with hot water, dried, ignited in a porcelain crucible, and the residue weighed. w. P. s. Estimation of Manganese in Soils.B. von Horvath. (Zeitsch. anal. Chem., 1914,53, 581-593.)-The colorimetric method described by Marshall (ANALYST, 1901, 26,195) and depending on the oxidation of manganese salts to permanganate by ammonium persulphate in the presence of silver nitrate (see also ANALYST, 1914, 39, 274) is recommended as being the most suitable process for the estimation of small quantities of manganese in soils.The hydrochloric acid extract of the soil is twice evaporated to dryness with nitric acid to expel chlorine and destroy organic substances, the residue is then heated with sulphuric acid to remove nitric acid, and the estimation proceeded with as described. Gravimetric and volumetric methods were found to be untrustworthy for the purpose. w. P.s. Estimation of Potassium by the Perchlorate Method. R. G. Thin and A. C. Cumming. (J. Chem. Soc., 1915, 107, 361-366.)-The authors find that this method can be depended on to give results of very satisfaetory rtcouracy. The error need never exceed 0.5 mgrm. on the weight of the potassium perchlorate. A neces- sary condition is that the precipitate shall be washed only with alcohol saturated with potassium perchlorate.This wash liquor wag recommended by Davis in a paper (ANALYST, 1913, 38, 47) in which he strongly recommended the method, but most of his test results given in that paper were obtained before he substituted this wash liquor for a weak solution of perchloric acid in strong alcohol. Consequently Davis’s test numbers, though good, are not exact, and give the impression that the method, though the best available, leaves something to be desired, whereas the authors now show that it is fully entitled to the description of an exact as well as a convenient, rapid, and cheap method.Attention is called to the fact that Mercb’s so-called ‘‘ pure ” perchloric acid (20 per cent.) is liable to contain appreciable traces of potassium perchlorate.G. C. J. Radiometric Measurements of the Ionisation Constants of Indicators. E. J. Shaeffer, M. G. Paulus, and €I. C. Jones. (J. Amer. Chem. Soc., 1915,37, 776-807.)-A satisfactory radiomicrometer, having a half-period of ten seconds and a sensibility of 5 per sq. mm. of exposed vane (candle and scale being at a metre’sINORGANIC ANALYSIS 297 distance), was constructed.Making use of the radiomicrometer and a grating spectroscope, a radiometric method was worked out for the determination of the ionisation constants of indicators. This method, which serves as well for a twc- coloured indicator as for a one-coloured indicator, is freer from objections and limitations than any method previously used. For the proof of the above claim, the original paper must be consulted. Briefly, the experimental procedure is as follows : The radiomicromoter is a thermo-electric junction attached to a loop of non-magnetic wire, the whole system being suspended by a quartz fibre in a glass tube.A strong magnetic field surrounds that portion of the tube enclosing the loop of wire. Radiant energy falling upon ,the blackened junction is converted into electrical energy, and the suspended system rotates in the magnetic field, the loop tending to set itself at right angles to the lines of force.The deflection is given by means of a mirror attached to the suspended system, Parallel light from a Nernst lamp is made to pass through the solution of the indicator, and is then deflected by a right-angle prism and focussed on the slit of the spectroscope, sl.Directly in the rear of this slit is another right-angle prism, which reflects the light through a 4-inch lens to the grating. The dispersed light is reflected back through this same lens and focussed on the slit of the spectroscope, s2, and the light emerging through this slit is again brought to a focus on the junction of the radiomicrometer.By turning the drumhead of the spectroscope it is then possible to determine quantitatively the light transmitted by any solution for all wave-lengths of light between A= 0.4 p and X = 2.0 p. Very small concentrations of coloured components were determined, and it is shown that minute concentrations of hydrogen and hydroxyl ions can be quickly and accurately estimated by means of radiometric measurements.Satisfactory constants were obtained for the ionisation of methyl orange as a base. The value found was 2.1 x 10 -11. The ionisation and hydrolysis constants for phenolphthaleln considered as a monobasic acid are far from being satisfactory. From the known ionisation constant of methyl orange and from radiometric measurements, the ionisation constant of a very weak base and the hydrolysis constant of one of its salts have been roughly determined.The method can likewise be applied for the determination of the ionisation constants of very weak acids, and the hydrolysis constants of the salts formed by these acids. G. C. J. Estimation of the Reducing Power of Natural Waters. L. W. Winkler. (Zeitsch. anal. Chem., 1914, 53, 561-564.)-The quantity of permanganate reduced in alkaline solution by natural waters (cj.ANALYST, 1902, 27, 341) may be estimated by treating 100 c.c., or less, of the water with 10 C.C. of alkaline i$a permanganate solutioo ; after standing for twenty-four hours, the mixture is acidified with sulphuric acid, potassium iodide is added, and the liberated iodine titrated with thiosulphate solution.The following procedure is recommended for waters containing nitrites, ferrous salts, and manganese salts: 100 C.C. of the water are treated with 1 C.C. of 10 per cent. sodium hydroxide solution and set aside for five minutes ; ferrous and manganous salts are thus oxidised by the dissolved oxygen in the water. The per- manganate solution is then added, and, after twenty-four hours, the mixture is298 ABSTRACTS OF CHEMICAL PAPERS 8.42 9.51 10.30 11.08 11.46 11.75 acidified with 25 per cent.phosphoric acid solution (this is preferable to sulphuric acid; as it prevents the action of the ferric salts on potassium iodide), potassium iodide is added, and the iodine titrated with thiosulphate solution. Another portion of the water is also treated with sodium hydroxide solution to oxidise the ferrous and manganous salts, permauganate solution is then added, and the excess titrated after the lapse of two minutes. The nitrites are thus oxidised whilst the organic matter is not appreciably affected; the result of this titration is a measure of the substances other than organic matters, which reduce permanganate.w. P. s.8.42 9.56 10.33 10-96 11-33 11.64 Comparison of the Relative Drying Powers of Sulphuric Acid, Calcium Chloride, and Aluminium Trioxide, when used in Ordinary Scheibler Desic- eating Jars. J. W. Marden and V. Elliott. (J. Ind. and E'ng. Chem., 1915, 7, 320-321.)-The water-vapour pressure of some materials still containing residual moisture is as low as that of the sulphuric acid over which they have been dried. By graphic interpolation it can be shown that concentrated (95 per cent.) sulphuric acid has a vapour pressure of about 0.03 mm.at 25" C. According to Thorpe (Dict. App. Chern., 1912,2,210) the speed of drying is hastened, but no more moisture is obtained by the use of vacuum. The authors found ,that with cheese, syrup, coffee, etc., using both sulphuric acid and calcium chloride, slightly more moisture was obtained with vacuum than without, in one case 0.7 per cent., in others quite small.It was found that the concentration of the sulphuric acid had little effect on its drying power for cane syrup and cheese between 95 and GO per cent. ; but with the former strength flour lost 12.48 per cent., and with the latter only 2.9 per cent., of water.Maple syrup lost as much moisture in one and a half hours when the air in the desiccator was stirred with a small motor as it lost in six hours without stirring. The following table shows the moisture lost to three different drying sub- stances kept at 25' C. The results were in the same order when vacuum desiccators were employed. Time Days. 1 2 3 5 7 13 Flour. CaC12. 8-47 9.21 10.06 10.62 10.96 11.15 14.12 18.76 23.73 29-36 29.53 29.53 H2S04 15 per Cent, 15.08 19.47 25.51 29.46 29.54 29-54 CaCI2. 15.22 16.84 21-31 28-77 29.42 29-42 Coffee. 1.31 1.98 2.66 3.30 3'54 3.66 CaClz . -- 1.17 1-02 2.38 3.11 3.32 3.46 H. F. E. R.REVIEWS 299 Estimation of Dissolved Oxygen in Water. L. W. Winkler. (Zeitsch. anal. Chem., 1914, 53, 665-672.)-The following modification of the author’s well- known method is described for the estimation of dissolved oxygen in waters containing nitrites and organic substances which interfere with the process : To the bottle containing some of ‘the water under examination, manganous chloride solu- tion and sodium hydroxide solution free from potassium iodide are added in the usual way, and a current of carbon dioxide passed in. The manganous hydroxide is thus converted into manganous carbonate and manganous hydrogen carbonate ; about ten minutes’ treatment with carbon dioxide is sufEcient. The precipitate is now collected on a filter, washed with a 2 per cent. potassium hydrogen carbonate solution, then dissolved in dilute hydrochloric acid containing potassium iodide, and the liberated iodine titrated. The manganous carbonate is not oxidised by atmos- pheric oxygen during the filtration. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9154000291

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

REVIEWS 299 REVIEWS . THE BRITISH PHARMACOPCEIA, 1914. London : Constable and Go., Ltd. Price ALTHOUGH the medical man, the manufacturer, and the pharmaciet are more directly concerned, the appearance of a ne.w edition of the British Pharrnacopceia is an event of considerable importance to the public analyst and to all who are concerned with the analysis and examination of drugs. The earlier editions previous to that of 1898, reflecting the state of knowledge of the period in which they were issued, afforded little or no practical assistance to the analyst charged with the task of determining by chemical examination the purity or potency either of the crude drugs, the active principles derived from them, or the preparations containing them.The new volume shows a great advance along the lines adumbrated by its immediate predecessor, and as the doctor no longer uses, and the retail pharmacist to a large extent no longer sells, drugs of his own preparation, it aims at dealing with the problems of assaying and standardising in a manner which was not SO necessary, and certainly was not possible, before, In size and appearance and in its general arrangement the new volume is similar to its forerunners.In spite of the fact that 168 substances or preparations mentioned in the 1898 edition, as well as a good deal of descriptive matter, are omitted, and only forty-three new drugs, etc., introduced, there are now 602 pages, as against 535 before. The increase is largely due to the greater attention paid to analytical processes, the special appendices dealing with which now occupy sixty- one pages instead of the forty-one of the preceding edition.In addition to this, considerable progress has been made with the standardisation of crude drugs and the tinctures and extracts made from them, and the number of such, for which processes for estimating the active constituents are described, has been approxi- mately doubled.10s. 6d. net.300 REVIEWS Apart from the above, there are a number ol changes of a general character which are worthy of note. The introduction of the term ‘( mil ” as a subetitute for the almost universally employed cubic centimetre is to be regietted. The only apparent advantage is that it opens the way for the adoption of the terms (( decimil ” and (‘ centimil ” for the tenth and the hundredth part of the cubic centimetre ; but our weights and measures are in a, sufficiently chaotic state already, without the additionof further alternative names for measures already in use.The fact that the quantities of the materials to be employed in making up the galenical preparations are now only expressed in metric weights and measures is a valuable advance; but it is a pity that the imperial system could not have been removed from the Pharmacopceia altogether. The option allowed, in the present edition, to the medical man of employing in his prescriptions either the imperial or the metric system, and the fact that though the medicinal doses are expressed in both, the quantities only approzinzately correspond, may quite conceivably cause trouble to the public analyst when called upon to analyse medicines made up from prescriptions, as the pharmacist might consider himself equally justified in using the approximately equivalent values for the two systems given on p.534 instead of the more accurate equivalents given on p. 533. The difference between the two amounts in some cases to over 11 per cent.The most important innovations for the analyst are the introduction of quanti- tative limit tests for arsenic and lead, with detailed directions for carrying them out, and standards-or, rather, limits-for fifty-five substances in the case of lead, and ninety-one in the case of arsenic, AS regards lead, the well-known colorimetric method has been adopted, sodium sulphide solution being added to solutions of specified strengths of the substances to be examined.Any error due to the presence of copper is avoided by the addi- tion of potassium cyanide, but the possible occurrence of iron has apparently been ignored. As the colour produced is influenced by the nature of the substance in solution, the Pharmacopceia provides that two solutions (one being from twice to six times the strength of the other) of the substances to be examined shall be prepared, the strengths of which are given in a table. These are to be equalised in colour, if necessary, before the sodium sulphide is added, and the proportion of lead present is calculated from the volume of standard lead nitrate solution which has to be added, to make the weaker solution match the stronger in colour.This, though not the ideal way out of the dificulty, obviates the necessity of the analyst being supplied with lead-free specimens of the fifty-five substances which may now have to be examined for that metal. I n the case of arsenic the Gutzeit process has been adopted, and it undoubtedly has great advantages over all other methods for the particular end in view.The details of the official process are apparently based on the work of Dunstan and Robinson; but, with a view, presumably, to the employment of larger volumes of liquid, a bottle fitted with glass tube and cork is now employed instead of the test-tube originally recommended. The delicacy of the test is of course increased, but at the expense of sitnplicity and convenience. The use of 10 grms.of zinc forRE VIEWS 301 each experiment seems an unnecessary extravagance when arsenic-free zinc is almost a precious metal, and the failure to take advantage of the treatment with hydrochloric acid to deepen the colour of the stain on the mercuric chloride paper counterbalances the advantage gained by the adoption of the bottle and glass tube.The methods for the preparation of the various substances for examination hsve evidently been worked out with great care and attention to detail, but the precise object of the procedure recommended is in some cases by no means apparent, and might have been stated with considerable advantage to the scientific worker. This is a criticism which applies more or less to all the descriptions of analytical processes throughout the book.The reader is apparently expected to regard the work as verbally inspired and to follow it blindly, without inquiring too closely into the reasons for what he is told to do. Of course, in many cases these are obvious to anyone with a knowledge of chemistry, but in others it is not so, and very brief explanations or references to already published papers would add greatly to the value of the work.At present its style is too much that of a cookery book, and one feels in doubt as to whether it is intended for the use of those who know nothing or for those who know everything. Another innovation to which reference should be made is the statement in the case of the processes for alkaloidal assay of “limits of error.” This is a valuable feature, but many will feel that a more extended experience is required of some of the newer processes before such limits can with advantage be fixed.Until a process has been in use for some time it is extremely difficult to make allowances for the quite unavoidable errors due to the personal equation, and slight but permissible variations in procedure as between different workers in different laboratories. I n some instances already disputes have arisen owing to unduly rigid insistence on these limits.To the various alterations and additions to the methods for the assay of alkaloidal drugs it is impossible to refer in detail. Very valuable improvements have in many instances been made, though in some the reaBons for the changes are not so apparent.The treatment, on the analytical side, of the essential oils is much more thorough than before, the number of substances for which ash limits have been fixed has been considerably added to, and the value of the whole work as a book of reference has been largely increased thereby. The editors are to be congratulated on the completion of a colossal task, of which only those immediately concerned in it can know the difficulty. That it has been accomplished with such a full measure of success was only to be expected from the personnel of the various committees concerned. We cannot help thinking, how- ever, that, in view of the change which has almost transformed what was once some- thing between a recipe book and & descriptive catalogue into a scientific work, the representative character of the committees of reference might well be extended so as to include one or more public analysts or analytical chemists amongst its number.C. H. CRIBB. In the new edition of the British Pharmacopceia a number of changes have been effected in materia niedica, although they are perhaps less conspicuous than those302 RE VIEWS that have been made in other sections of the Pharmacopceia.Only three new drugs have been introduced-viz,, Cassia Fructus, Ipomctm Radix, and Senna Fructzis. Of these the first is added as the source of cassia pulp, the second as one of the official sources of scammony resin, while the third is frequently ordered by the medical profession. No fewer than forty-seven have been omitted, some of which, such as pepper, mustard, figs, prunes, etc., are regarded as being either sufficiently controlled in other ways or as being commercial products not requiring official description ; while others, such as coca, jaborandi, cantharides, and pome- granate root-bark, have been deleted as unnecessary, because for t heqpeutical purposes they are efficiently represented by their active constituents, cocaine, pilocarpine, cantharidin, and pelletierine respectively.As a result of these omissions and additions, the Pharmacopceia is poorer in crude drugs by the number of about thirty-five. No fewer than fourteen have been deleted from the Indian and Colonial Addendum, and even this number could with advantage have been increased; it remains therefore to b3 seen whether the General Medical Council has succeeded in producing a ‘‘ British Pharmacopceia suitable for the whole Empire.” Amongst the well-known drugs now no longer included are arnica, rhizome, saffron, sarsaparilla, scammony, coca leaves, and elder flowers.Arnica rhizome, coca leaves, elder flowers, and sarsaparilla might well have been retained, as prepara- tions of them are in constant use.Scammony, a much adulterated drug, is suffi- ciently represented by its active constituent, scammony resin, which may now be obtained either from scammony root or, as has been for some years actually the caee, from the root of Ipomcza orixabeizsis. Saffron has in all probability nothing to recommend it but its high colouring value. The new edition exhibits therefore a distinct tendency to replace crude drugs by their active constituents, to exclude those that are not prescribed with sufficient frequency to warrant their retention, and to maintain its conservatism with regard to the introduction of new ones.Conspicuous in the introductory lines of each monograph is the omission of the reference to any illustration of the plant or animal by which it is yielded, an innova- tion that few will regret.How under such a drug as Cetaceum, for example, reference to a picture of sperm whale could afford the slightest assistance in deter- mining the identity or purity of spermaceti, has long been a puzzle to pharma- cologists, and the General Medical Council is to be congratulated on having purged the Pharmacopceia of such absurdities.In the wording of the monographs, a striving towards terseness is very evident, and though it has led to what is in many cases a n almost unpleasant abruptness, the excision of verbose phrases needlessly repeated will probably meet with general approval. When the new monographs are examined, it will be seen that the tests, both of identity and quality, have been considerably increased in number and stringency.The identity of drugs possessing organised structure has been made more precise by an extension of the microscopical characters, while in nine instances the micro- scopical characters of the powdered drug have been introduced. I n these respects a, distinct advance is to be noted, but it is much to be regretted that no definite plan has been followed.The microscopical characters of all drugs employed in theREVIEWS 303 Pharmacopcoia in powder too fine to allow of its preparation by the pharmacist should certainly have been included, and a few others in common use might well have been added to the list ; a favoursble opportunity of accomplishing the innova- tion in a systematic manner has thus been lost.The tests designed to limit the quality of crude drugs have also been con- siderably extended. Gentian root and liquorice root are now required to yield a minimum of aqueous extract ; cubebs and ginger, of oleo-resin ; Indian hemp, of resin; and balsam of tolu and storax, of aromatic acids. Alkaloidal limits have been fixed for aconite root, belladonna leaves, ipecacuanha root, and nux vomica, while liquid extract of belladonna root, extract of henbane, and liquid extract of hydrastis, heve been standardised, although no alkaloidal limits have been fixed for the drugs from which these preparations are derived.The number of ash-limits has also been considerably increased, chiefly with the view of excluding improperly cleaned drugs. No attempt has been made to introduce the biological standardisation of such drugs as foxglove leaves, ergot, etc.This is probably due to the fact that the same drug biologically tested by different workers has had various degrees of activity assigned to it, and therefore, until a standard institution has been set up in which all such drugs can be tested under identical conditions, the introduction of such standardisa- tion is not advisable.For a similar reason, no doubt, no sera have been introduced. While there is manifested in the new Pharmacopceia a distinctly progressive tendency, there is also very evident the desire to adopt as standards high corn- mercial qualities of crude drugs, and to avoid the restriction to the very highest qualities which are often procurable in limited quantities only, and at a cost dis- proportionate to their real value. This principle is the same as that which h.as been adopted in fixing the standards of purity for chemicals, and there is no reason why crude drugs and chemicals should not be treated on similar lines ; indeed, there is much to be said in favour of such a procedure.I n the majority of cases it is quite possible to establish the identity and purity of a crude drug by means of macroscopical and microscopical characters and chemical reactions, while the past ten years have seen a notable advance in the possibility of estimating its quality by means of h e chemical determination of one or more of its constituents.The present Pharmacopoeia is, in these respects, considerably ahead of its predecessor. H.G. GREENISH. The new edition of the British Pharmacopceia, although published on the last day of 1914, had been on view for some three months previously. It is of special interest to analytical chemists, whether practising as Public Analysts or engaged in chemical factories or pharmaceutical laboratories. Earlier issues of the Phsrmacopceia were more concerned with the details of the cultivation of drugs and with their physical characters, than with the determina- tion and assay of their active constituents, and, with regard to chemicals, paid more attention to, and described more fully, processes for their production than methods of testing for impurities.A change has, however, been gradually taking place, and in the volume now placed in our hands less emphasis is laid upon the geographical304 REVIEWS and even botanical sources of drugs, whilst much more attention is paid to the evaluation of their so-called active principles.Concerning chemicals, a pregnant sentence in the preface is worthy of full quota- tion : “ The paragraphs in former issues which purported to be descriptive of the sources or modes of nianufacture of official chemical substances have been made more concise, so far as the requirements of the Medical Act of 1858 will permit, but descriptions of the characters and tests by which the substances may be determined have been amplified and increased in number.” This would seem to imply that the Pharmacopceia, on its chemical side, has become critical and analytic rather than synthetic, Under Aconite Root we find a ba.ro botanical description, but not the familiar requirement that the drug should be the product of plants grown in Great Britain.I t is required to yield not less than 0.4 per cent. of ether-soluble alkaloids-a standard which, although useful, will probably not suffice to insure equality of podency in samples drawn from different countries.Other drugs which are valued by their alkaloidal content are belladonna leaves, for the assay of which a satisfactory process is given; cinchona bark, which has been officially directed to be assayed at least since the year 1885 ; ipecacuanha root, nux vomica, and opium. There would seem to have been a mistake made in the description of the process recommended for ipecacuanha root.The powdered root is directed to be extracted by agitation with a mixture of chloroform and ether; solution of ammonia and water are then added, and 50 millilitres of the clear separated liquid are directed t9 be collected and shaken with 10 millilitres of & solution of hydrochloric acid. This amount of hydrochloric acid is not sufficient to neutralise the ammonia, and, having experienced difficulties in working from this cause, one sought informa- tion as to the genesis of the official process. This was found in a paper contributed by A.G. C. Paterson in 1903, as a result of experiments made by hi1-n i n the Research Laboratory of the Pharmaceutical Society. Prtterson’s work was admittedly founded on that of Frerioh, and he directs that the ammoniacal solution shall be evaporated to one-half, and that then a definite amount of acid or excess shall be added.With this modification the official process seems to give good results. As regards drugs which cannot be standardised to an alkaloidal content - Balsam of Peru is required to contain 57 per cent. of cinnamein, the saponification value of which must be not less than 235, a process being given.Balsam of Tolu is required to yield 25 par cent. of balsamic acids, a standard which has been stated by a competent commercial expert to be too high. Prepared storax is to yield 20 per cent. of cinnamic acid, The important drug Indian hemp is only valued by its yield of extractive to alcohol, but this test will fail to distinguish between the East African and Indian varieties, as the amount of resin may vary even when the extractive is equal-a variation which, with such a potent drug, is of considerable import.There are a large number of ash limits given for crude drugs, but perhaps the section concerning natural products of most concern to the analyst is that dealing with essential oils. For these, very elaborate standards and tests are prescribed,REVIEWS involving in many cases the determination of the optical rotation and refractive index, as well as the percentage of alcohols and esters.On the inorganic side the most interesting part is that which gives limits of lead and arsenic in practically all the chemicals in which they are likely to occur, very definite and exact tests being set out for their determination.H. WIPPELL GADD. THE EXTRA PHARMAGOP~IA. By MARTINDALE and WESTGOTT. Sixteenth edition. Vol. i., pp. xl+ 1113. 14s. Vol. ii., viii + 469. 7s. London : H. K. Lewis. 1915. In no branch of applied chemistry has the war brought into greater prominence our dependence on German enterprise and appreciation of scientific research than in materia medica, pharmaceutical chemistry, pharmacognosy, pharmacology, therapeutics, and the analytical chemistry of drugs and other remedial agencies.I t is precisely with recent advances in this group of sciences that the authors of the “Extra Pharmacopceia ” deal in their greatly enlarged sixteenth edition of this comprehensive treatise. The importance of research in therapeutics is prominently emphasised by a synopsis of recent changes in the British Pharmacopceia, and among noteworthy additions to the list of official preparations may be cited the following drugs: acidum acetylsalicylicum, adrenalini liquor hydrochloricus, guaiacol, hexamina (hex amet h ylenet etramine), met h ylsulphonal and phenolpht haleinurn.The greater part of volume i. is devoted to a concise and readable summary of important drugs, oflicial and otherwise, arranged in alphabetical order.The subject- matter under each heading includes the chemical and therapeutic properties of the drug, methods of preparation, modes of administration, medicinal use, copious references to current literature, and a critical commentary on the value of drugs in various pathological conditions.A comparison between British and foreign practice is facilitated by frequent references to the pharmacopceial drugs of other countries, and notably to those in use in the United States. The most recent investigations in therapeutics and pharmacology receive recognition, as, for example, in the sections on anaesthetics, colloidal metals, ionto- phoresie (ionic medication), vaccines, radium, and radiology.In many sections the authors have either confirmed experimentally the data of other investigators or have themselves contributed additional information to the fund of knowledge. Reference may be made to coumaric acid and its derivatives, introduced into pharmacy by one of the authors (W. H. M.), who has also with promising results initiated pharma- cological experiments on colloidal copper complexes and on organic derivatives of antimony’ and mercury.The organic arsenicals continue to be popular therapeutic agents, and the two chapters on this subject have been revised and enlarged. Ehrlich’s claim to a, (‘ therapia sterilisans magna ” is critically examined. Readers of the ANALYST will be specially interested in that portion of work devoted to the analytical chemistry of drugs and other materials of physiological and pathological importance.306 REVIEWS The analytical addenda to the materia medica of volume i.are found in the opening pages of volume ii., which also contains a useful section on analytical memoranda dealing specially with the examination of water, milk, blood, urine, and various physiological and pathological substances.Assistance in the recognition of organic drugs is given in the form of a chart, the substances being arranged alphabetically. The data for these tests were chiefly obtained by personal trials in the authors' laboratory. The chapter on bacteriological aad clinical notes is a concise introduction to the study of pathogenic organisms.A suggestive synopsis of the few observed relationships between the chemical constitution of drugs and their physiological effects is included, and sections of more general interest are con- tributed on organotherapy, mineral waters, antiseptics, and proprietary medicines. The critical revision within the two years which have elapsed since the issue of the fifteenth edition of the enormous mass of detailed information contained in the '( Extra Pharmacopceia '' is a striking testimony to the indefatigable industry and encyclopzedic knowledge of the authors. The entire treatise cannot fail to be of the utmost practical value to all interested in recent developments in pharmacy, therapeutics, and the allied sciences.G. T. MORGAN. NATIONAL PHYSICAL LABORATORY.COLLECTED RESEARCHES. Vol. xi. Pp. 320. The only paper in this volume likely to attract the attention of analytical chemists is that dealing with viscometry (pp. 3-16). Careful perusal of it leaves your reviewer keenly disappointed. Nearly two years ago he prepared for the ANALYST an abstract of a paper descriptive of work done on this subject at the National Physical Laboratory, and published in the Joumal of the Society of Chemical Iizduustry.The latter Journal took the responsibility of curtailing the paper presented to it, and the present writer attributed certain unsatisfactory features of the paper to this editing, and in a, footnote directed those interested in the subject to await the publication of the full text in the next volume of Col- lected Researches (ANALYST, 1913, 38, 397). It is disappointing, therefore, to find that the full text contains little, if anything, of importance that was omitted in the publication of two years ago. The author of the paper determined the absolute viscosity of some light oils at temperatures ranging from 10" to 60" C., using the best means available. The time of flow from a Redwood viscometer was then observed for each of these oils, again making experiment at several temperatures.As a result of these observations, a formula is deduced for converting the indications of this particular Redwood viscometer into absolute viscosities. The reader might be pardoned for drawing the conclusion that the author puts forward this formula as applying with equal truth to any other Redwood viscometer, yet it is well known that the indica- tions of two of these instruments sometimes differ widely.Taking U bbelohde's formula for converting the readings of Engler's viscometer into absolute viscosities, and his own formula for the particular Redwood instru- ment in the possession of the National Physical Laboratory, the author deduces a formula connecting the readings of Engler's and Redwood's instruments.Here, 1914. Price 20s. London : Harrison and Sons.REVIEWS 307 again, the reader might be pardoned for supposing that this formula purported to correct the reading of any Engler viscometer with that of any Redwood viscometer. A careful perusal of the text, however, reveals the fact, not surpris- ing to one acquainted with the shortcomings of these convenient commercial viscometers, that a particular Engler instrument experimented with at the National Physical Laboratory gave indications differing 8s much as 8 per cent.from those which would correspond to Ubbelohde’s formula. For ths two instruments tested, therefore, the author’s formula is this much in error, and if either were changed for another of the same type, the error might be more or less.The result of the whole research seems incommensurate with the labour involved in assembling and calibrating the apparatus used for determining absolute viscosities. The writer may have expected too much from this research. I t was undertaken for the International Commission for the Unification of Tests on Petroleum Pro- ducts, and it is possible that the author was directed to apply himself mainly to a study of the Redwood and Engler viscometers.In their day these instruments yielded good service, and when the choice lay between one of them and, say, the glischrometer” of Thorpe and Rodger, there was no question which must be used for commercial work. But in view of the work of Bingham and his c01- laborators in America, it is reasonable to suppose that these instruments must soon give way to other apparatus, the indications of which can be calculated to absolute viscosities with less than some assigned small error, No very elaborate apparatus is required to keep this error as small as 0.1 per cent., but accuracy of this kind implies very close temperature control, and is unnecessary for commercial work, For many purposes results certainly accurate within 1 per cent. would be very satisfactory.With the resources of the National Physical Laboratory applied to the design of an instrument of this type, it should not be long before the Red- wood and Engler instruments were relegated to museums, and a very great service would be rendered to all who bave to collate, or try to collate, the viscometric measurements of others.Anyone who will take the pains can now determine viscosities with sufficient accuracy. The root of the Redwood and Engler tradition, which hinders progress, lies in laziness, and what is needed is an instrument designed on scientific principlea, but consistent with those principles, with the maximum regard .to ease of manipulation, so as not t o be much more trouble- some in use than the instruments it must displace. Some sacrifice of convenience there probably must be, but it need not be great for work accurate to, say, 1 per cent., and the cost should be less than that of the older instruments, G.CECIL JONES. CLAY AND POTTERIES INDUSTRIES. Being Vol. I , of the Collected Papers from the County Pottery Laboratory, Staffordshire. By several Authors.Edited by J. W. MELLOR, D.Sc. London : Charles Griffin and Go., Ltd. 1914. Price 15s. net. These papers represent some of the results of the research work carried out by the Stoke-on-Trent Pottery School from the time the editor of this volume took Pp. xvii + 411.308 REVIEWS control until it assumed its present dimensions and importance of a well-equipped Institute of Science and Technology. Most of the papers are reprinted from the Transactions of the English Ceramic Society, and those to whom this publication is not readily accessible will welcome their appearance in this handy form. Interest in the subjects dealt with is neces- sarily restricted to a comparatively limited circle of readers, but some of the paper8 deserve wider attention, and may be regarded as models of what industrial research should be, combining a highly scientific treatment of everyday problems with the practical applicability of results. This must be particularly appreciated in respect of an industry which, by reason of the employment of rule-of-thumb methods and the handing down of (‘ trade secrets ” from generation to generation, is in constant danger of stagnation.. In this connection, Dr. Mellor’s addresses on technical education are well worth reading, and from their perusal one may gather the spirit in which work is carried on in his school. The individual subjects include investigations covering a wide range of pottery and fireclay industries. The Determination of Small Amounts of Iron in Clays,” are essentially of interest to analysts, whilst those dealing with the ‘( Chemical Constitution of the Kaolinite Molecule ” and the ( 6 Xomenclature of Silicates ” may be regarded as classical work in this branch of chemistry. The very complete references to previous literature will be of great help to the student. The book is profusely illustrated, and in an introduction Mr. Graham Balfour gives an interesting account of the history of the Institute. A few, such as ‘( The Rational Analysis of Clays ” and R. LESSING.

ISSN:0003-2654    

DOI:10.1039/AN9154000299

出版商:RSC    

年代:1915

数据来源: RSC