ISSN:0003-2654    

DOI:10.1039/AN95075FX005

出版商:RSC    

年代:1950

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN95075BX007

出版商:RSC    

年代:1950

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN95075FP009

出版商:RSC    

年代:1950

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN95075BP013

出版商:RSC    

年代:1950

数据来源: RSC

摘要:

FEBRUARY, 1950 THE ANALYST Vol. 75, No. 887 PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS ANALYTICAL METHODS COMMITTEE SUB-COMMITTEE ON DETERMINATION OF EGG YOLK SOLIDS IN SALAD A SUB-COMMITTEE has been appointed to consider the practicability of recommending a standard method of analysis for the determination of egg yolk solids in salad cream, mayonnaise and any other salad dressing. The Sub-committee consists of H. E. Cox, D.Sc., F.R.I.C. (Chairman); E. B. Anderson, M.Sc., F.R.I.C.; G. E. Forstner, MSc., F.R.I.C.; C. L. Hinton, F.R.I.C.; H. E. Monk, B.Sc., F.R.I.C. ; C. G. Daubney, M.Sc., F.R.I.C. (Hon. Secretary). CREAM, MAYONNAISE AND ANY OTHER SALAD DRESSING EXTRAORDINARY GENERAL MEETINGS EXTRAORDIKARY General Meetings of the Society were held on September 20th, 1949, and February lst, 1950, the President occupying the chair on both occasions.Special Resolutions were carried at these meetings by overwhelming majorities altering certain of the Society’s Articles of Association. At the meeting held in September a Resolution was proposed that the name of the Society be changed to “The Society for Analytical Chemistry.” A majority of votes was cast in favour of this resolution, but failed to reach the three-fourths majority needed for a Special Resolution, so that the name will remain unchanged. SCOTTISH SECTION THE Fifteenth Annual General Meeting of the Section was held in Glasgow on January %th, 1950, and the following office bearers were elected for the year :-Chairman-Dr. J. Sword. Vice-Chairman-Mr. H.C. Moir. Hon. Secretary and Treasurer-Mr. R. S. Watson, City Analyst’s Department, 20, Trongate, Glasgow, C. 1. Elected Committee Members-Messrs. A. Dargie, H. Dryerre, M. Herd, J. M. Leitch, J. R.I. Malcolm and R. G. Thin. Hon. - 4 u d i t ~ ~ - Messrs. A. R. Campbell and W. M. Cameron. MICROCHEMISTRY GROUP THE Sixth Annual General Meeting of the Microchemistry Group was held at Sir John Cass College, London, E.C.3, on Friday, January 27th, 1950. It was reported that the number of members of the Group is now 309, an increase of 51 during 1949. The following Officers and Committee Members were elected for the ensuing year :--Chairman-Mr. Ronald Belcher. Vice-Chairman-Dr. Cecil L. Wilson. Hon. Secye.etayy--Mr. Donald F. Phillips. Hen. Treasuw-Mr. Gerald Ingram.Elected Committee Members-Messrs. A. E. Heron, R. F. Milton, J. Sandilands, C. E. Spooner, D. W. Wilson and G. H. Wyatt. An exhibition of new microchemical apparatus was organised by Dr. J. T. Stock, and a series of short papers describing the apparatus were read by Messrs. J. T. Stock, G. InPam, w. T. Chambers, M. A. Fill, P. Heath, A. J. Lindsey, F. J. McMurray, W. Marshment and A. C, Mason. 6162 INTERNATIONAL MICROCHEMICAL CONGRESS [Vol. 75 PHYSICAL METHODS GROUP THE Fifth Annual General Meeting of the Group was held at 6 p.m. on Tuesday, November 29th, 1949, in the Chemistry Lecture Theatre, Imperial College of Science and Technology, London, S.W?7. Dr. J. G. A. Griffiths, the Chairman of the Group, presided. The Group Officers and Elected Members of Committee for the forthcoming year are as follows :-Chairman- Mr.B. S. Cooper. Vice-Chairman-Dr. W. F. Elvidge. Hon. Secretary-Mr. R. A. C. Isbell, Hilger & Watts Ltd., Hilger Division, 98, St. Pancras Way, London, N.W.l. Members of Committee-Messrs. L. A. Haddock, J. Haslam, J. A. C. McClelland, H. E. Monk, J. E. Page and A. A. Smales. Votes of thanks were accorded to the three retiring members of the Committee, Messrs. J. G. A. Griffiths (Chairman), J. E. Page (Secretary) and W. Cule-Davies, for their services to the Group during the past two years, and to the Hon. Auditors for their work during the past year. The Annual General Meeting was followed by the Twenty-third Ordinary Meeting of the Group, at which Dr. J. G. A. Griffiths delivered a lecture on “The Mass Spectrometer- A Survey of its Applications in Analysis,” and by a demonstration by Dr.E. F. D. Winter of the apparatus used in the Imperial College. BIOLOGICAL METHODS GROUP THE Fifth Annual General Meeting of the Biological Methods Group was held at 6.15 p.m. on Tuesday, December 13th, 1949, in the Anatomy Lecture Theatre, University College, London, W.C.1. The following were elected as Officers and Members of the Committee for the year 1950:- Chairman-Mr. N. T. Gridgeman. Hon. Secretary- Mr. S. A. Price, Vitamins Ltd., 23, Upper Mall, London, W.6. Elected Committee Members- Mr. W. A. Broom, Dr. W. F. J. Cuthbertson, Dr. R. L. Edwards, Mr. H. Pritchard, Dr. J. Raventos, Mr. G. A. Stewart and Ex-ojicio Members, the President, Hon. Treasurer and Hon.Secretary of the Society and the Editor of The Analyst. Hon. Aaditors-Mr. D. M. Fre’eland and Dr. J. H. Hamence. The Annual General Meeting was followed by an Ordinary Meeting at which the following papers were read and discussed: “The Microbiological Assay of Riboflavine in Yeast and Yeast Products, using Lactobacilhs helveticus in a 17-hour Titrimetric Method,” by A. Jones and S. Morris; “A 24-hour Plate Assay Technique for the Vitamin B, Complex of Yeast, with a Note on the Possible Presence in Certain Yeasts of a Fourth Member of the B, Complex,” by A. Jones and S. Morris; “The Assay of Serum Gonadotrophin by the Ovary Weight Method,” by G. L. M. Harmer. NORTH OF ENGLAND SECTION AN Ordinary Meeting of the Section was held at Manchester on Saturday, November 26th, 1949. The Chairman, Mr. J. G. Sherratt, presided, and the attendance was 44, including the President, Mr. G. Taylor, O.B.E. The following papers were read and discussed: “The Standardisation of Hortvet Thermometers,” by R. W. Sutton, BSc., F.R.I.C., and J. Markland, B.Sc., F.R.I.C., and “Notes on Molasses in Grass Meals and Pellets,” by F. Robertson Dodd, F.R.I.C. Hon. Auditors-Messrs. Bassett and Garratt (re-appointed). Dr. A. J. Amos was in the chair. Vice-Chairman-Dr. H. 0. J. Collier.

ISSN:0003-2654    

DOI:10.1039/AN9507500061

出版商:RSC    

年代:1950

数据来源: RSC

摘要:

62 INTERNATIONAL MICROCHEMICAL CONGRESS [Vol. 75 INTERNATIONAL MICROCHEMICAL CONGRESS THIS will be held in Graz, Austria, on the above dates, under the auspices of the Austrian Society for Microchemistry. The provisional programme includes the commemoration of the tenth and twentieth anniversary of the death of Emich and Pregl respectively, both of whom carried out their pioneering work on the development of microchemical techniques in Graz. There will be lectures by well known microchemists covering the whole field of micro- chemistry, reports, exhibitions, receptions by Government and municipal dignitaries, and bestowal of honorary membership of the Osterreichische Gesellschaft fiir Mikrochemie on participants. The Congress President is Professor H. Lieb. Further information and forms of invitation may be obtained from the Congress Secretary, H. Malissa, at the Congress H.Q., Schlogelgasse, 9, Graz, Austria, or from the Hon. Secretary Qf the Microchemistry Group, Donald F. Phillips, 10, Richmond Road, Blackpool, N.S., Lancs. JULY 2ND TO 5TH, 1950

ISSN:0003-2654    

DOI:10.1039/AN9507500062

出版商:RSC    

年代:1950

数据来源: RSC

摘要:

Feb., 19501 HASLAM AND SOPPET : METHACRYLATE POLYMERS 63 The Examination of Methyl Methacrylate Polymers and Co-Polymers BY J. HASLAM AND W. SOPPET SYNoPsIs--hIethods which have proved useful in the examination of methyl methacrylate polymers and co-polymers are described. The method of determination of plasticiser in this type of polymer is described and full details are given of the vacuum depolymerisation of plasticiser-free polymers. Observations are made on the identification of the depolymerisation products with particular reference to polymethyl methacrylate alone, and co-polymers containing polystyrene, polycyclohexyl methacrylate and polyethyl acrylate. The chemical evidence is supported by infra-red data. METHYL methacrylate polymers and co-polymers are of various types.The preparation may contain plasticiser, colouring agent or filler. It may be co-polymerised, i.e., it may consist of co-polymers of methyl methacrylate and styrene, of methyl methacrylate and ethyl acrylate, methyl methacrylate and cyclohexyl methacrylate or of other possible combinations. As the most important question which has to be answered about these preparations is the nature of the polymer or co-polymer, the purpose of this paper is to describe some of the methods which have proved to be most valuable in this connection. When dealing with compositions containing polymethyl methacrylate, the most satis- factory method of identification is to prepare as pure a monomer as possible by depolymerisa- tion of the polymer. The first fact to be realised, however, is that depolymerisation of poly- methyl methacrylate preparations in air, without preliminary treatment, yields a monomer which is distinctly unsatisfactory for the purpose of identification.A monomer prepared in this way from polymethyl methacrylate containing small proportions of plasticiser gave the following figures on examination- Saponification value (mg. of KOH per g.) . . = 527 Refractive index, 20" C. .. .. 1-42 0.11 - I - Aldehydes, as H.CH0, per cent'. .. .. The recovered monomer was shown, by polarographic and dimedone precipitation methods, to contain formaldehyde. This monomer was distilled at 20 mrn. pressure and the fractions were examined separately with the following results. 1st Fraction 2nd Fraction volatile a t 100" C . , (about 30%) (about 60%) 20 mm.pressure) Residue (not Saponification value (mg. of KOH per g. sample) 545 548 390 Refractive index, 20" C . .. . . .. 1-4135 1-4135 1.487 Carbon, per cent. . . .. .. .. - 64.9 - Aldehydes, as H.CH0, per cent. . . .. 0.064 0-016 Hydrogen, per cent. .. . . . . .. - - 7.5 - It should be noted that the accepted values for pure methyl methacrylate are as follows- Carbon, per cent. . , .. . . .. . . 60.0 Hydrogen, per cent. .. . . .. . . 8.0 Refractive index, 20" C. .. . . . . , . 1.4144 Saponification value (mg. of KOH per g.) . . 560 It is therefore desirable to remove the plasticiser as a preliminary to any satisfactory depoly- merisation process and this is best accomplished by solution of the preparation in acetone followed by precipitation of the polymer with light petroleum.This isolation of the plasticiser- free resin forms part of the ordinary method of determination of plasticiser in polymethyl methacrylate compositions and is as follows- One gram of the sample, in the form of finely divided drillings, is weighed into a beaker (250 ml.) provided with a glass stirring-rod. Twenty-five ml. of acetone are added and the liquid is brought just to the boil, with continuous stirring on the water-bath. The solution is then allowed to cool for about 1 hour. By this treatment the polymer in all ordinary64 HASLAM AXD SOPPET: THE EXAMINATIOS OF METHYL [Vol. 7 5 samples will be taken into solution, but with abnormal samples it may be necessary to allow the solution to stand for a longer time. Eighty ml.of light petroleum (b.p. 40" to 60" C.) are now added and the mixture is stirred vigorously and then allowed to settle. After standing for 1 hour the precipitate is filtered on a 1 x G3 sintered-glass Gooch crucible, the filtrate being collected in a flask (250ml.). The resin is washed three times with 5 ml. of light petroleum on each occasion. The washed resin is then dried to constant weight in the oven a t 100" C. In the determination of the plasticiser, the light petroleum solutions are collected and the solvent removed by evaporation on the water-bath, previous to drying at 100" C. Carried out in this way the method gives results for the plasticiser that are slightly on the high side, i.e., 0.0 to 0.3 per cent., owing to the solution of small amounts of low molecular weight polymer in the light petroleum extract.The behaviour of a methacrylate polymer in the plasticiser determination can on occasion yield evidence of the presence of abnormal additives. In the determination of the plasticiser in a recent competitive product, the light petroleum extract of the plasticiser had a strong odour of "oil of wintergreen," and the presence of salicylate was confirmed on hydrolysis of the resulting plasticiser. Before depolymerisation experiments are carried out, it is often desirable to make exact carbon and hydrogen determinations on the deplasticised resin ; in this connection the theoretical figures for the carbon and hydrogen contents of polymethyl methacrylate, poly- styrene, polycyclohexyl methacrylate and polyethyl acrylate are of value.They are as follows- Carbon Hydrogen Y O % Polymethyl methacrylate . . . . .. 60.0 8.0 Polyst -ene . . . . . . .. .. 92.26 7-74 Polyc- lohexyl methacrylate . . .. 71.4 9.5 Polye yl acrylate . . . . .. . . 60.0 8.0 It will be no d from the above figures that co-polymerisation of methyl methacrylate with 10 per cent. ( polystyrene leads to production of a polymer with the following elementary andysis- Per cent. Carbon . . .. . . . . . . . . 63.2 Hydrogen . . .. .. . . .. . . 7.95 Co-polymerisation with 50 per cent. of cyclohexyl methacrylate produces a polymer with the following elementary analysis- Per cent. Carbon . . . . . . .. * . . . 66.7 Hydrogen . . . . .. .. .. . , 8.75 It is important, however, to realise that co-polymerisation with ethyl acrylate produces a co-polymer with carbon and hydrogen figures exactly similar to those of polymethyl met hacrylate. Depolymerisation in air, i.e., by heating the plasticiser-free resin prepared in the above way in a small flask and subsequent distillation of the monomer, does not yield a very satis- factory monomer for identification purposes, as is shown by the following figures which were obtained by heating plasticiser-free polymethyl methacrylate in a side-arm distillation flask at 360" C., using a Wood's metal bath, for an hour.The distillate had the following characteristics- Saponification value (mg. of KOH per g.) . . 540 Refractive index, 20" C. . . . . .. . . 1.416 Recovery . . . . . . . . . . . . about 60% Appearance * . . .. . . . . . .Yellow Our experience with methacrylate polymers goes to show that the only satisfactory method of depolymerisation involves heating in vacuo under conditions which ensure the immediate distillation of the monomer as soon as it is formed. We are indebted to Dr. J. W. C. Crawford for details of an apparatus for this purpose, and the method we have found most satisfactory is given below in full. In this method, as applied to the depolymerisation of polymethyl methacrylate, 1 g. of the plasticiser-free sample is weighed into the tube A of the Pyrex glass vacuum depoly- mensation apparatus shown in Fig. 1.Feb., 19501 METHACRYLATE POLYMERS AXD CO-POLYMERS 65 The upper portion of tube A is then sealed off at C in the blowpipe flame, leaving a capillary tip. Tube B is now connected at E to a high vacuum pump and when the pressure on the manometer connected to the pump has been reduced to 1 mm.of mercury and with the pump still connected, the apparatus is sealed off in the blowpipe flame at D. I 'i Fig. 1. Vacuum depolymerisation apparatus of pyrex glass. Dimensions are in centimeters The apparatus is now assembled with tube A immersed in a bath of Wood's metal at 100" to 120" C . This Wood's metal is contained in a small metal bath, l-inch internal diameter and 34 inches long. *Tube B is immersed in a solid carbon dioxide - methanol freezing mixture at -70" to -80" C. contained in a Dewar flask (capacity 1 litre) and the levels of A and B are so arranged that the point G is at a higher level than point F. The temperature of the Wood's metal bath is now raised to 340" to 350" C.over a period of 15minutes and is maintained at this temperature for 1 hour. The apparatus is then withdrawn from the hot Wood's metal bath and cold solid carbon dioxide - methanol mixture, the capillary tip at C broken and the tube B cut off near the top, i.e., at a point G. The analytical examination of the monomer in tube B is carried out without delay in order to avoid polymerisation. The following figures are typical of those obtained on depolymerisation of polymethyl methacrylate by the above procedure. The figures obtained on examination of pure methyl methacrylate are also given for purposes of comparison. Monomer recovered from polymethyl methacrylate by Pure methyl depolymerisation methacrylate in vacuo monomer ... . 90-97 - .. .. . . .. . . Water white - Recovery, per cent. .. .. .. Saponification value (mg. of KOH per g.) . . .. 556-560 560 Colour . . Refractive index, 20" C. .. .. .. . . 1.4142-1*4144 1.4144 Acid value . . .. . . .. . . . . nil nil On occasion, valuable evidence about other additives in the polymer may be obtained from the odour of the recovered monomer. A recent competitive sample had a strong odour of mercaptan, presumably added in the polymerisation process. Although the amount present was extremely small it was quite sufficient to mask the very characteristic odour of methyl met hacrylate. BEHAVIOUR OF METHYL METHACRYLATE - POLYSTYRENE INTERPOLYMERS ON DEPOLYMERISATION in vacuo In our experience polymethyl methacrylate - polystyrene interpolymers may be depoly- merised by vacuum depolymerisation exactly as indicated above for polymethyl methacrylate alone.Although it might be expected that because methyl methacrylate boils at 100" C. and styrene a t 143" C., preferential depolymerisation of the polymethyl methacrylate would take The yield of monomer is rather low.66 HASLAM AND SOPPET: THE EXAMINATION OF METHYL [Vol. 75 place, our analytical evidence hardly supports such a view and the recovered monomer mixture always contains styrene. The following results were obtained on depolymerisation of a polymethyl methacrylate - polystyrene interpolymer containing 10 per cent. of polystyrene. Recovery, per cent. .. . . .. .. .. 70-76 Colour .. . . .. . . . . . . Water white Refractive index, 20" C. ... . . . Saponification value (mg. of KOH per g.) . . . . . . 1.4242 510 High carbon figures on the original deplasticised resin, together with figures similar to those given above for the recovered mixed monomer, point to the probable presence of styrene. I t is our practice to confirm the presence of styrene in such samples by heating the monomer recovered from 2 to 2.5 g. of polymer with 5 ml. of 50 per cent. w/v KOH solution for 1 hour under reflux. The mixture is cooled and diluted to 25ml. with water and the solution then extracted with 5ml. of ether. The ether layer is washed with 5ml. of water and then filtered through a dry filter paper into a test tube (5 x + inch). The ether is removed by evaporation on the water-bath, the last traces of the solvent being removed by a stream of compressed air.Eight to ten drops of the residue are measured into a clean test tube (5 x 4 inch) and liquid bromine is added dropwise until a definite excess is indicated by the colour of the mixture. The excess of bromine is removed by heating on the water-bath and the mixture cooled. The solid residue is broken up with a glass rod and dissolved by heating with 5 ml. of 80 per cent. v/v ethyl alcohol. The filtered solution is cooled and the crystalline deposit filtered off and recrystallised from 3 ml. of 80 per cent. v/v ethyl alcohol. The crystallised product is dried in air and its melting-point determined. Styrene dibromide melts at 73" C . (uncorrected). BEHAVIOUR OF POLYMETHYL METHACRYLATE - POLYETHYL XCRYLATE INTERPOLYMERS ON DEPOLYMERISATION in vacuo Polymethyl methacrylate - polyethyl acrylate interpolymers may be depolymerised by vacuum depolymerisation as indicated above for polymethyl methacrylate alone.The recovered monomer usually possesses an odour resembling to a certain extent that of ethyl acrylate and is quite different from that of methyl methacrylate alone, but the yield of recovered monomer is low, and the saponification value and refractive index do not differ appreciably from the corresponding figures for pure methyl methacrylate, as the following results indicate- Monomer recovered Monomer recovered from polymethyl from polymethyl methacrylate with methacrylate with 10 per cent. polyethyl 5 per cent. polyethyl acrylate acrylate .. .. about 60 about 60 ..Recovery, per cent. . . .. 1.4135 .. 1.4141 Refractive index, 20" C. .. .. Saponification value (mg. of KOH per g.) . . 648 557 Colour . . .. .. a . .. . . Water white Water white In material such as this it is desirable to supplement the information by carrying out a test for the detection of the ethyl ester in the recovered monomer as follows- One ml. of the monomer is heated under reffux for 1 hour with 2.5 ml. of 50 per cent. w/v KOH solution. After cooling, 2ml. of water are added and the solution is distilled until 2 ml. of distillate have been collected. To this distillate are added 5 ml. dichromate mixture (100 g. of potassium dichromate dissolved in a mixture of 280 ml. of concentrated sulphuric acid and 750ml. of water) and the solution redistilled into a 15-1111.centrifuge tube until 0.5 ml. of distillate has been collected. One pellet of solid potassium hydroxide is added and the tube placed in a beaker of boiling water. If an ethyl ester was present in the original recovered monomer, the caustic pellet will turn yellow and the solution will boil, turn yellow and emit the obnoxious odour charac- teristic of aldehyde resins. BEHAVIOUR OF POLYCYCLOHEXYL METHACRYLATE - POLYMETHYL METHACRYLATE INTERPOLYMERS ON VACUUM DEPOLYMERISATION The behaviour of polycyclohexyl methacrylate - polymethyl methacrylate interpolymers on depolymerisation in vacuo is entirely different from that of polymethyl methacrylate itself.Feb., 19501 METHACRYLATE POLYMERS AX D C 0-POLYME RS 67 The procedure is that of the general method except that where this kind of interpolymer is expected the depolymerisation is carried out for a period of 2 hours.With this type of interpolymer the depolymerisation product consists of two layers, the lower one of which is chiefly water. The figures for saponification and refractive index of the product are, therefore, of little diagnostic value. The following figures, which were obtained on the depolymerisation product of an inter- polymer containing 46 per cent. of polycyclohexyl methacrylate and 54 per cent. of polymethyl methacrylate, are typical of the results that may be obtained. Saponification value (mg. of KOH per g.) . . . . 120-200 Refractive index, 20" C . . . . . . . . . 1'42-1.43 Yield (2 hours), per cent. . . . . . . . . 40-50 ,4cid value (mg.of KOH per g.) . . . . .. 3 Water (Fischer), per cent. . . . . . . . . 7-10 Behaviour similafto that recorded above usually indicates the presence of a co-polymer of cyclohexyl and methyl methacrylates, but it is always necessary to proceed further in order to obtain evidence of this. Tests which are of great value in this connection involve the production of cyclohexene from the depolymerisation product and its subsequent identification. In this identification the cyclohexene is oxidised to adipic acid, the melting-point of which is determined. \ .WIRE SPACER F5rnm. DlAM c Fig. 3. Continuous ether extractor Fig. 2. Apparatus for continuous steam distillation The methacrylic acid in the depolymerisation product is isolated and may be identified as its fi-phenyl phenacyl bromide derivative; the presence of a methyl ester is confirmed by isolation of the corresponding alcohol, oxidation of this to formaldehyde, and the identifica- tion of the latter by the chromotropic acid reaction.Full details of the method are given below. One ml. of the depolymerisation product is heated under reflux for an hour with 5 ml. of 50 per cent. w/v potash solution. The flask containing the solution is then connected to the continuous steam distillation apparatus The mixture is cooled and 5 ml. of water added.€!ASLAM AND SOPPET: THE EXAMINATION OF METHYL [Vol. 75 Polr methyl fltthorrylQt P Fig. 4. Infra-red spectra of methyl I Pal 7 s t y re neFeb., 19501 METHACRYLATE POLYMERS ASD CO-POLYMERS 69 methacrylate polymers and co-polymers70 HASLAM AND SOPPET: THE EXAMINATIOS OF METHYL [Vol. 75 illustrated in Fig.2 and the steam distillation carried out for half an hour, by which time an oilyjayer will have collected in the detachable tube A. The aqueous layer in the detachable tube is reserved for the detection of methyl alcohol. The oily layer is transferred to a small separating funnel, and after being washed with 5 ml. of water, transferred to a 1-mi. centrifuge tube containing a small quantity of anhydrous potassium carbonate. After the solution has stood overnight, the boiling-point, refractive index and specific gravity of the clear upper layer of cyclohexene are determined. A portion of this cyclohexene is then converted to adipic acid by taking 0.2 ml. of the suspected hydrocarbon and heating it gently under reflux for 10 to 15 minutes with 5 ml. of dichromate - sulphuric acid mixture (100 g.of potassium dichromate dissolved in a mixture of 250 ml. of concentrated sulphuric acid and 750 ml. of water), The product is diluted with 5ml. of water and then extracted with ether for 15 minutes in a small continuous ether extractor (Fig. 3). The ether is evaporated to low bulk and the solution transferred t o a 1-ml. centrifuge tube previous to final evaporation to dryness. The resulting adipic acid is recrystallised from 0.5 ml. of water and the product dried at 100" C. previous to the determination of its melting-point. For the detection of methyl alcohol, the water in the detachable tube, referred to above and reserved for this test, is transferred back to the original hydrolysis flask containing potash, etc.To this distillate are added 5ml. of dichromate oxidation mixture and the solution distilled until 0.5 ml. of distillate has been collected. Three to four drops of this distillate, contained in a 6 x 8 inch test tube, are mixed with 2 ml. of diluted sulphuric acid solution (150 ml. of concentrated sulphuric acid + 100 ml. of water) and a few crystals of the sodium salt of chromotropic acid. The tube is then heated for 10 minutes by immersion in a water-bath at 60" to 70" C. The production of a violet colour indicates the presence of a polymethyl ester in the original polymer. The presence of rnethacrylic acid in the depolymerisation products is confirmed as follows- The alkaline solution obtained in the small flask, after the removal of any methyl alcohol referred to above, is acidified with concentrated hydrochloric acid and the solution saturated with sodium chloride.This saturated solution is then extracted twice with 5-ml. portions of ether. The ether extracts are combined, washed with 2 ml. of saturated sodium chloride solution and transferred to a small flask. One ml. of 10 per cent. w/v sodium hydroxide solution is now added, the ether is evaporated off on the water-bath and the residual solution neutralised with N hydrochloric acid solution. P-Phenyl phenacyl bromide (0.1 g.) is added and the mixture heated under reflux for 30 minutes. The hot solution is filtered and the filtrate allowed to crystallise. The product is recrystallised from 2 ml.of ethyl alcohol and dried in air previous to determination of its melting-point. Some idea of the kind of figures that are obtained in this kind of test may be seen from the results of the examination of two polymers, one of which was polycyclohexyl methacrylate itself, whilst the other consisted of an interpolymer containing 46 per cent. polycyclohexyl methacrylate and 54 per cent. of polymethyl methacrylate. The cyclohexene obtained from the two polymers had the following properties- Interpolymer containing 46 per cent. polycyclohexyl methacrylate and Polycyclohexyl 54 per cent. polymethyl The mixture is now distilled until 2 ml. of distillate have been collected. methacrylate methacrylate Refractive index, 20" C. .. .. .. 1.449 1.451 Boiling-point . . .. .. .. .. 84" C . 84" C. Specific gravity, 25/4' C. . . . . .. 0.838 0.846 In both, the adipic acid prepared by oxidation of the cyclohexene melted at 148" C. The melting-points of the 9-phenyl phenacyl bromide derivatives of the methacrylic acid obtained from the two depolymerisation products were respectively 121" C. for the inter- polymer and 118" C. for the cyclohexyl methacrylate. It is always desirable to supplement chemical examinations similar to those outlined above with infra-red evidence obtained on known polymers and co-polymers, e.g., a substance submitted for analysis was shown to contain Per cent. Carbon . . .. . . .. . . . . 66.3 Hydrogen . . .. . . . . . . * . 8.9 Oxygen .. 0 . , I 3 , . . . . 25.8Feb., 19501 METHACRYLATE POLYMERS AND CO-POLYMERS 71 On solution in acetone and precipitation with light petroleum followed by evaporation of the light petroleum solution, the substance yielded a residue amounting to 2.2 per cent. This residue was a hard, clear solid which possessed the smell of a monomer. It gave no evidence of the presence of a phthalate and was almost certainly low molecular weight polymer.Subsequent examination of this polymer by the chemical methods outlined above indicated that it was a co-polymer of polycyclohexyl methacrylate and polymethyl meth- acrylate and the carbon, hydrogen and oxygen figures indicated that the approximate proportions were 46 per cent. polycyclohexyl methacrylate and 54 per cent. polymethyl met h acrylat e. Support for this view was obtained when an interpolymer was prepared containing 50 per cent. of polymethyl methacrylate and 50 per cent. of polycyclohexyl methacrylate. The infra-red spectra of these two specimens, the sample and the comparison mixture were very similar indeed, as is shown in Fig; 4. On pages 68 and 69 are given the infra-red spectra of the above two specimens, together with those of- (a) Polymethyl methacrylate. (b) Polystyrene. (c) Polycyclohexyl methacrylate. (a) Interpolymer of polymethyl methacrylate containing 10 per cent. of polystyrene. (e) Interpolymer of polymethyl methacrylate containing 7 per cent. of polyethyl acrylate. (f) Interpolymer of polycyclohexyl methacrylate containing 20 per cent. of poly- methacrylic acid. We should like to take this opportunity of expressing our indebtedness to Mr. Willis of our Research Department for the preparation of the infra-red spectra and for his general interest in this investigation. IMPERIAL CHEMICAL INDUSTRIES LIMITED WELWYN GARDEN CITY PLASTICS DIVISION HERTS. June, 1949

ISSN:0003-2654    

DOI:10.1039/AN9507500063

出版商:RSC    

年代:1950

数据来源: RSC

摘要:

Feb., 19501 The METHACRYLATE POLYMERS AND CO-POLYMERS Determination of Phenodoxone in 71 Urine BY J. E. PAGE AND HEATHER KING SYNOPSIS-A colorimetric method has been devised for determining pheno- doxone in urine. Phenodoxone is the official name of a recently available powerful analgesic, DL-6-morpholino-4 : 4-diphenylheptan-3-one, the hydro- chloride of which is available under the proprietary name “Heptalgin.” The base from urine samples containing about 0.4mg. of the drug is liberated with alkali and extracted into toluene; the toluene extract is shaken with an aqueous solution of bromophenol blue buffered a t pH 4.0. An amount of dye, equivalent to the weight of drug in the toluene layer, is carried over into the toluene as a yellow compound, and this is decomposed by shaking the toluene layer with aqueous alkali.The sodium salt of the dye then enters the aqueous layer and is determined colorimetrically. Basic substances that react with bromophenol blue to form a toluene- soluble compound (alkaloids, such as codeine, and synthetic analgesics, such as pethidine and amidone) interfere with the determination. PHENODOXONE is the official name given to DL-6-morpholino-4 : 4-diphenyheptan-3-one. The hydrochloride of this substance was first studied under the description CB11, which will be used for convenience in the present communication; it is now generally available under the proprietary name “Heptalgin.” I t is used because of its marked action as an analgesic, which is combined with a relatively low toxicity, so that its therapeutic ratio is higher than that of other similar compounds.Its preparation has been described by Dupr6, Elks, Hems,72 PAGE AND KISG: THE DETERMINATION OF [Vol. 75 Speyer and Evans1 and by Attenburrow, Elks, Hems and Speyer,2 and its pharmacology by Basil, Edge and Somer~.~ For the determination of CBll in urine we have used a modification of Lehman and Aitken’s procedure4 for determining pethidine. Scott and Chen6 and Cronheim and Ware6 have employed like methods for the estimation of amidone and Hopewell and Page’ have described a somewhat similar technique for the determination of long-chain aliphatic amines. Ethyl- 1 -methyl-4-phenylpiperidine-4-carboxylate ,CH,.CH 2,c/C0. OCH ,. C H, \CH,.CH,/ \c> hydrochloride. Pethidine. CH,.N HC1 6-Dimethylamino-4 : 4-diphenylheptan-3-one hydrochloride.Amidone. CH/ 6 Morpholino-4 : 4-diphenylheptan-3-one hydrochloride, “ Heptalgin ” (CBll). n Fig. 1 The method depends on the reaction of equimolecular quantities of the analgesic and bromophenol blue to form a toluene-soluble compound. The free base of the drug is extracted into toluene and the toluene extract is shaken with an aqueous solution of the dye buffered at pH 4.0. An amount of dye, equivalent to the weight of drug in the toluene layer, is carried over into the toluene as a yellow compound, which is decomposed by shaking the toluene with aqueous alkali, whereupon the sodium salt of the dye enters the aqueous layer and is determined colorimetrically. Under these conditions, CBll gives a more intense colour than when tested by either Lehman and Aitken’s bromothymol blue method4 or Cronheim and Ware’s bromocresol purple method.6 The polarographic behaviour of CBll was also studied with a view to finding a suitable analytical method.In 0.1 N potassium chloride it gave a polarographic step with a charac- teristic peak at -1-75 v. (cf. Fig. 2). The step height was approximately proportional to concentration over the range 0.0075 to 0.075 per cent. However, the step height was sensitive to small amounts of surface-active material and appeared at a relatively high potential, so that the method was unsuitable for determining CBll in biological fluids. Experimental firocedure-Our recommended procedure for the determination of CB 11 is as follows. Shake 10 ml. of the solution, containing about 4 mg.of CBll per 100 ml., with 2 ml. of 10 N sodium hydroxide and 30 ml. of redistilled toluene in a separating funnel. Pipette 25 ml. of the supernatant toluene into a second separating funnel and shake for 5 minutes with 20 ml. of a bromophenol blue solution buffered at pH 4-0 (made by mixing 60 ml. of 0.05 M potassium hydrogen phthalate with 40ml. of a 0.08 per cent. bromophenol blue solution). Centrifuge (if necessary) the mixture from the separating funnel, transfer 20 ml. of the supernatant toluene to a third separating funnel, and extract in turn with three 5-ml. portions of 0.1 N sodium hydroxide. Dilute the combined alkaline extracts to 20ml. with 0.1 N sodium hydroxide and examine an aliquot portion in a Hilger photo-electric absorptio- meter fitted with a yellow gelatin filter (Ilford No.606) and a heat-resisting Chance glassFeb., 19501 PHENODOXONE IN URINE 73 filter (No. H503). The concentration of CBll can be determined from a calibration curve prepared for solutions containing between 1.0 and 10.0 mg. of CBll per 100 ml., over which range there is a linear relationship between drug concentration and absorptiometer reading. Solutions containing more than 10mg. of analgesic per 100ml. should be diluted before testing. Determinati0.n in zcrine-The bromophenol blue method may be used to determine CBll in human and rat urine, but because any basic substance capable of reacting with bromophenol blue to form a toluene-soluble compound will respond to the test, the following precautions must be observed.I lo: I = ‘0 I: I’ I 1.4 1.6 I -8 2.0 POTENTIAL IN’ VOLTS. Fig. 2. Polarogram for an 0025 yo solution of CBll in 0.1 N (Drop-time on open circuit in 9.1 N Weight of potassium chloride solution. potassium chloride solution at 26’ c.=3.13 SBCS. mercury dropping per sec. = 1.82 mg.) Certain alkaloids such as codeine, and sFthetic analgesics such as pethidine and amidone, interfere with the determination; the intensity of the colour formed by amidone is greater than that produced by an equivalent quantity of CB11, and is about the same as that formed when amidone is examined by Cronheim and Wue’s procedure.6 Adequate control specimens must therefore be tested and particular care must be exercised in analysing urine samples from subjects who have received special medication.Bacterial growth in the urine leads to the production of basic substances giving the same colour response as CB11; a small amount of an antiseptic (e.g., mercuric chloride or toluene) must therefore be placed in the vessel used for collecting the urine. During the solvent extraction of urine, the ratio of the volume of toluene to that of the urine must be kept as high as possible in order to prevent the formation of stable emulsions. The calibration curve for the determination of CBll in urine is about 30 per cent. lower than that for its determination in simple aqueous solution. REFERENCES 1. Dupre, D. J., Elks, J., Hems, B. A., Speyer, K. N., and Evans, R. M., J. Chem. SOC., 1949, 500. 2. Attenburrow, J., Elks, J., Hems, B. A., and Speyer, K. N., Ibid., 1949, 610. 3. Basil, B., Edge, N. D., and Somers, G. F., Brit. J. Pharmacol., in the press. 4. Lehman, R. A., and Aitken, T., J. Lab. Clin. Med., 1943, 28, 787. 6. Scott, C. C., and Chen, K. K.. J. Pharmacol., 1946, 87, 63. 6. Cronheim. G., and Ware, P. A., Ibid., 1948, 92, 98. 7. Hopewell, B. M. C., and Page, J. E., Analyst, 1946, 70, 17. RESEARCH DIVISION GLAXO LABORATORIES LTD. GREENFORD , MIDDLESEX May, 1949

ISSN:0003-2654    

DOI:10.1039/AN9507500071

出版商:RSC    

年代:1950

数据来源: RSC

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74 KENDALL AND PHILLIPS: ESTIMATION OF THE THICKNESS OF [Vol. 75 Estimation of the Thickness of Wax “Bloom” on Vulcanised Rubbers BY F. KENDALL AND MISS W. M. PHILLIPS SyNoPsIs-The method consists in cutting a known area of the rubber without disturbing the surface bloom, and wiping the surface with four or five successive twists of de-fatted cotton wool, held by cleaned forceps and moistened with light petroleum. The twists are transferred to a prepared extraction funnel and the fat extracted from them and weighed. The thickness of the bloom is calculated from the area of the specimen and the weight and specific gravity of the wax recovered. CERTAIN waxes, when incorporated into a rubber mixing, “bloom” to the surface soon after vulcanisation. This bloom forms some protection against the deterioration of strained rubber which takes the form of surface cracking and which is now known to be caused by atmospheric 0zone.l In an investigation of this protective effect it was important to be able to estimate the thickness of the surface bloom of wax.Several methods for determining the thickness of the bloom have been investigated. They include methods based on removal by scraping, optical interference caused by the thin film, electrical resistivity of the rubber with and without the bloom, difference of focus of a microscope at the top and bottom of the film of bloom, microscopical examination of cut sections of the rubber, and removal of the bloom by wiping with solvent-damped cotton wool and subsequent determination of the wax in the wool. Of these several methods only two, the cutting of sections and the removal of bloom by cotton wool, proved both easy and satisfactory, although, doubtless, optical interference methods could be made satisfactory if adequate apparatus were available.A technique for cutting sections of the rubber was developed so that as far as possible the wax film was cut cleanly without fracture. By microscopical examination of the section the film thickness was measured with an eyepiece scale and a stage micrometer. Polarised light was used to provide greater contrast between wax film and rubber surface. This method gave reproducible results when used for wax blooms not less than 3 microns thick, but was found to be unsuitable for thinner films. METHOD ADOPTED FOR ROUTINE USE After trial, the removal of the wax bloom by wiping with cotton wool moistened with a solvent and the subsequent quantitative extraction of the wax from the wool was adopted as the preferred-method.Knowledge of the area of rubber involved and the specific gravity* of the wax enables the thickness to be calculated from the weight of wax recovered. It was found convenient to cut disc specimens 5 cm. in diameter from sheet by means of a press cutter, but specimens of other shapes are equally satisfactory provided disturbance of the wax bloom is avoided in cutting. PROCEDURE- Wash the appropriate fingers of the hand with solvent (light petroleum, b.p. 40” to 60” C.) and twist pre-extracted cotton wool round the end of a pair of cleaned forceps. Moisten the cotton wool with solvent and wipe the rubber surface.The wiping action should be rapid but should not involve rubbing or heavy pressure. After wiping transfer the twist of cotton wool to a prepared extraction funnel. Wiping treatments with four successive twists was found sufficient for most blooms, but a fifth twist should be ysed for heavy blooms. The total amount of cotton wool used for the four or five twists should be such that, when placed in the extraction funnel and extracted with the solvent, it should not expand above the rim of the funnel. Extraction of wax from cotton wool-The apparatus used was the micro-extraction apparatus described by G. H. Wyatt.2 * This is best determined by a flotation method such as is given in Standard Methods for Testing Pejrojeum and its Prudircts, Institute of Petroleum, Ninth Edition, London, 1948.Cut out a specimen of suitable size and determine its area.Feb., 19501 WAX "BLOOM" ON VULCANISED RUBBERS 75 Weigh a clean extraction cup. (This can be done on an ordinary analytical balance, although in the development of the procedure a micro-balance was used.) Add 2 or 3 ml. of light petroleum (boiling range 40" to 60" C.) and then transfer the cup to the extraction tube. Support the funnel containing the cotton wool to be extracted in the frame immediately above the cup, add a further 1 or 2 ml. of light petroleum and close the tube with the metal condenser. Extract for 2 hours, remove the condenser and funnel and allow the solvent to evaporate to dryness. Transfer the extraction cup to a vacuum desiccator for 15 minutes before weighing.From the weight of wax, W, and its area, A, and specific gravity, calculate the thickness, t . of the bloom: W (in g.) A (in sq. cm.) x sp.gr. t (in cm.) = DISCUSSION OF THE METHOD- Light petroleum (boiling range 40" to 60" C.) was found to be the most suitable solvent as it combines a very high solvent power (11.7 g. of paraffin wax per 100 g. of solvent) with a convenient boiling range. The standard deviation of replicate determinations was first determined from two sets of three extractions carried out at two different times on the same vulcanisate (Mix 1: pale crepe 100, sulphur 2, MPC black 5, zinc oxide 0.5, paraffin wax 7, zinc dibutyldithiocarbamate 0.5). The results expressed as the weights determined instead of the thicknesses estimated from them are given in the following table.Weight of wax extract, Mean weight, Standard deviation, mg. mg. mi?. 2-62, 2.41, 2.85 2.63 0.22 3-41, 3.93, 3.41 3.58 0.30 On examining the results obtained with other vulcanisates (details of which are omitted) for which duplicate estimations had been made, tabulation of the differences between each pair of figures showed them all to be of the same order, with two exceptions. Mix No. . . .. 2 3 4 6 6 7 8 9 10 11 Difference, mg. .. 0-37 1.60* 0.65 0-14 1.56* 0.67 0.10 0.02 0.03 0.34 0.21 0-50 0.36 0.09 0-41 0.38 * These figures ignored. From the mean of these figures, corrected to the nearest tenth of a milligram and omitting the two that were not of the same order as the others, an estimate of the average difference between duplicate results was made.It seems highly probable that a manipulative error occurred with one or other of the duplicates marked with an asterisk. The average difference between the weights of wax obtained in replicate tests is therefore such that an ordinary analytical balance has sufficient discriminating power for the purpose and can be used instead of a micro-balance. The value obtained was 0.30 mg. RESULTS OBTAINED- As an illustration of some typical results, values for a series of transparent rubbers are quoted, where the amount of wax found is shown to be correlated with the amount of wax added to the mixing. Wax content on 100 parts of rubber hydrocarbon Weight of bloom, mg. 0.7 nil 1 0-067 0.067 3 1.21 5 1-43 1-52 7 2-28 15 3.73 4-07 Thickness of bloom, cm. x 1W6 nil 3 3 6 7 8 12 19 2176 SRINIVASAN : POTENTIOMETRIC DETERMINATION OF SMALL AMOUNTS [VOl. 75 The authors acknowledge with thanks permission from the Research Association of British Rubber Manufacturers to publish this paper. REFERENCES 1. Newton, R. G., J . Rubber Res., 1945, 14, 27-62. 2. Wyatt, G. H., Analyst, 1946, 66, 362-370. RESEARCH ASSOCIATION OF BRITISH RUBBER MANUFACTURERS 106, LANSDOWNE ROAD CROYDON, SURREY January, 1949

ISSN:0003-2654    

DOI:10.1039/AN9507500074

出版商:RSC    

年代:1950

数据来源: RSC

摘要:

76 SRINIVASAN : POTENTIOMETRIC DETERMINATION OF SMALL AMOUNTS [VOl. 75 Potentiometric Determination of Small Amounts of Procaine, Sulphanilamide and Related Compounds Bromate - Bromide Titration BY K. R. SRINIVASAN SYNoPsIs-Determination of procaine by direct titration with potassium bromate solution, using a pair of polarised platinum electrodes, is described. The method is simple, rapid and yields results of high precision and accuracy. It is applicable to the determination of other local anaesthetics of the p-amino- benzoic ester type, and also of some of. the sulpha drugs. SMALL amounts of procaine, in ointments, tablets, blood, etc., have been determined by colorimetric methods1J0,1* after diazotisation of the prirnary amino-group and coupling with a suitable reagent to form a coloured compound.These methods are useful only within a limited working range of concentration; they require the use of special equipment and are not rapid and direct, as they need the preparation of standard reference curves or the use of internal standards. The A.O.A.C. method of determination of procaine by brominationle consists in hydrolysis to p-aminobenzoic acid, reaction with a large excess of bromine for 2 hours at room temperature and titration of the excess of bromine with thiosulphate solution after addition of potassium iodide, when, under these conditions, tribromoaniline is formed. This method is time- consuming, and unless the conditions are strictly followed, will lead to low recoveries owing to under-bromination.15 Day and TaggartS found that p-aminobenzoic acid is not satis- factorily detehined by the excess-bromine method because of precipitation of partially brominated products.This is due to the fact that while the velocity constant of formation of tribromoaniline from aniline, or of the dibromo-derivative of @-substituted anilines, is very high, being of the order of lo8 (sees), the rate of further substitution of the latter by bromine to form tribromoaniline by elimination of the substituent group in the $-position, is relatively low, the extent of this reaction depending on conditions of temperature,' time of contact with bromine and residual bromine excess.15 Satisfactory results are, however, to be expected in determinations by direct titration with bromate and bromide ifi acid solution, since the reaction here proceeds to and stops at the stage of dibromo-substitution. But the difficulty with bromometric titration lies in the determination of the end-point.The use of an external indicator such as starch-iodide paper renders the method tedious3; with irreversible internal indicators like methyl orange the titration has to be done very slowly and any local Concentration of bromine will cause the colour of the indicator to fade before the end-point; other indicators8 besides being slow, will not be useful in solutions that are coloured. These difficulties are obviated in the present method by the use of a pair of polarised platinum electrodes as described by Foulk and Bawden.6 A very sharp end-point is obtained, as the slightest excess of bromine in the solution at once depolarises the cathode and causes a large deflection of the galvanometer. DETERMINATION OF SULPHONAMIDES Sulphanilamide and its derivatives are determined with equal facility by bromometric titration.The British Pharmacopoeia2 method consists in titration of the acid solution of the drug at a low temperature (15" C.) with standard sodium nitrite solution, wherebyFeb., 19501 OF PROCAINE, SULPHANILAMIDE AND RELATED COMPOUNDS 77 the NH, group is diazotised. The end-point is indicated by the immediate formation of a blue colour with starch-iodide paste used as an external indicator. This titration is slow and tedious, and as the reaction slows down towards the end, one has to wait for a few minutes after each addition of the reagent before testing for the end-point.Further, some uncertainty as to the exact end-point is often experienced, for even before the theoretical amount of sodium Fig. 1. Titration Assembly nitrite has been added, a blue colour is formed within a few seconds of placing a drop of the solution on the starch iodide paste. Determination of sulphanilamide as its dibromo-derivative by the excess bromine methodll often leads to erratic results owing to over-bromination, the extent of which varies with temperature, time of contact with bromine and residual bromine exce~s,~ and check results are obtained only under strictly controlled conditions of the experiment. With sulphathiazole, sulphapyridine, sulphadiazine and sulphaguanidine, Wells16 found that the excess bromine method cannot be successfully applied for their determifiation without preliminary hydrolysis to sulphanilic acid by heating with hydrochloric acid under reflux.The direct method of titration with bromate as outlined here has the advantage of simplicity and rapidity over these methods, and accurate results are obtained even with small amounts (Table I). REAGENTS AND APPARATUS- bromate, dried at 120" C. for 1 hour, is dissolved in a litre of distilled water. with water. Potassium bromate solution, 0.01 N---0-2784 g. of Analytical Reagent grade potassium DiZuted hydrochZoric acid--230 ml. of concentrated acid (sp.gr. 1.18) is made up to a litre Potassium bromide solution-10 per cent.78 SRINIVASAN : POTENTIOMETRIC DETERMINATION OF SMALL AMOUNTS [VOl. 75 The electrode is made by fusing two short pieces (about half an inch) of platinum wire at the end of glass tubing of 3-mm. bore and 10-cm.length. Connections are made by means of copper leads, silver-soldered to the platinum wires. The copper leads are sleeved by two melting-point capillaries. A polarising voltage of about 10 millivolts is obtained from a 600-ohm resistor (I.R.C. Q watt) and a small spiral of Nichrome wire (No. 26 S.W.G.) having a resistance of about 3.11 ohms, connected in series across a 14-volt dry cell as shown in Fig. 1. G is a Leeds and Northrup type 2420 spot light galvanometer, In titrating very small quantities, a 5-ml. graduated pipette (N.P.L. certified class A accuracy) with a fine tip, operated by a hypodermic syringe and rubber tube, was used in the absence of a precision micro-burette. Stirring is done by any suitable stirrer or even by swirling the beaker by hand.PROCEDURE- An aliquot containing about 5 mg. of the substance is taken in a 30-ml. beaker; 1 ml. of the potassium bromide solution and 10 ml. of the diluted hydrochloric acid are added. The electrodes, which have been cleaned by means of hot chromic acid and washed with distilled water, are dipped into the solution and connected up in the circuit. The solution is titrated with the potassium bromate solution, the end-point being indicated by a permanent deflection of the galvanometer from the zero position. TABLE I DETERMINATION BY BROMATE TITRATION Substance Procaine hydrochloride Benzocaine . . Sulphanilamide . . Sulphapyridine .. Sulphaguanidine Sulphathiazole* Sulphadiazine* . . .. .. .. .. .. .. Sample weight, mg. .. 2.32 3.25 4.26 .. 2.72 1-86 3.88 .. 1.70 1.90 3.67 .. 3-76 2-78 4.56 .. 2.64 3-37 5.45 .. 2.54 1-84 4-5-9 .. 3.08 2.85 1-89 0.01 N KBrO, required, ml. 3-42 4.75 6.27 6-60 4-55 9-42 3.95 4.42 8.55 6.0 4.45 7-32 4.52 5.75 9.37 5.95 4-35 10.72 7.40 6.80 4-54 Amount found, mg* 2.33 3.24 4.27 2.726 1.88 3.89 1.70 1.91 3-675 3-74 2.775 4.56 2-625 3.34 5-44 2.53 1.85 4.66 3.08 2-835 1.892 Equivalent weight is one-sixth of the molecular weight. DISCUSSION Recovery, 100.4 99-6 100.3 100.6 101.0 100.2 100.0 100.5 100.2 99.5 99.8 100.0 9 9 4 99.1 99.8 99.6 100.0 99-3 100.0 99.5 100.1 % Table I gives the results of a few of the determinations made and shows the accuracy and reproducibility of the method, which are satisfactory, considering the small size of the sample used.All the samples were purified by recrystallisation from alcohol or water, dried, and weighed out by means of a micro-chemical balance. Only procaine hydrochloride and benzocaine were taken for investigation, although other local anaesthetics of the $-amino- benzoic ester type may be determined similarly. In all cases except sulphathiazole and sulphadiazine the equivalent weight was taken asFeb., 19501 OF PROCAINE, SULPHANILAMIDE AND RELATED COMPOUNDS 79 one-fourth of the molecular weight, as four equivalents of bromine are taken up according to the equation NH2 0 + 4Br -+ ’8. +2HBr X X where X represents the substituent group in the $-position with respect to NH,.With sulphathiazole and sulphadiazine, six equivalents of bromine are found to be required, presumably owing to bromine substitution in the thiazole and pyrimidine nuclei as weL4 The determinations were made a t the laboratory temperature of about 30°C. and appreciable deviations in the temperature of the solution were found to have a negligible effect on the final result. An acid concentration of about 2 N was maintained. The limitation of the method is that it is useful only when any of the substances con- sidered is present alone, and in the absence of other easily brominated compounds, e g . , phenols. APPLICATION TO PROCAINE PENICILLIN As the degradation products of penicillin obtained on treatment with acid consume bromine, it was necessary to separate the procaine from penicillin by extraction with chloroform after liberating the free base with ammonia as described by Shaw.13 The procaine is taken up in hydrochloric acid from the chloroform solution and the acid solution is titrated with standard bromate.One ml. of 0.01 N potassium bromate is equivalent to 049mg. of procaine base. The results are given in Table 11. TABLE I1 DETERMINATION OF PROCAINE IN PROCAINE BENZYL PENICILLIN mg. ml. %t 25.0 16.95 39.9 The method was applied for estimating procaine in procaine benzyl penicillin. Sample* weight, 0.01 N KBrO, required, Procaine, 20.7 14-05 40-0 8.3 5-60 39.8 * Squibbs “Crysticillin” brand of procaine penicillin G was used. t The theoretical value is 40.12 per cent. of procaine. Grateful acknowledgment is made to Sri K.V. Sundaram Ayyar, Government Analyst, for his helpful suggestions and interest in the work. The author is indebted to Col. S. L. Bhatia, the Surgeon-General with the Government of Madras, for permission to publish this paper. REFERENCES 1. 2. 3. 4. 5. 6. Francis, A. W., Ibid., 1926, 48, 1632. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. - , Ibid., 1942, 25, 747. Bandelin, F. J., and Kemp, C . R., Ind. Eng. Chem., Anal. Ed., 1946, 18, 470. British Pharmacopoeia, 1948, p. 603. Day, A. R., and Taggart, W. T., Ind. Eng. Chem., Anal. Ed., 1926, 20, 546. English, J. P., et al., J . Amer. Chem. SOC., 1940, 68, 453. Foulk, C. W., and Bawden, A. T., Ibid., 1926, 48, 2045. Francis, A. W., and Hill, A. T., Ibid., 1924, 46, 2500. Hahn, F. L., Ind. Eng. Chem., Anal. Ed., 1942, 14, 571. Hoshall, E. M., J . Assoc. Off. Agr. Chem., 1939, 22, 748. Lapih-e, C., Anal. Chim. Acta, 1947, 1, 337. Martindale’s Extra Pharmaco+oeia, 22nd Ed., Vol. 11, 1945, p. 356. Methods of Analysis, Assoc. Off. Agr. Chem., 6th Ed., 1945, p. 697. Shaw, W. H. C . , J . Pharm. Pharmacol., 1949, 1, 514. Ting, K. S., et al., J . Lab. and Clinic. Med., 1949, 34, 822. Wells, E. H., J . Assoc. Ofi. Agr. Chem., 1942, 25, 541. LABORATORY OF THE GOVERNMENT ANALYST MADRAS 15, INDIA KING INSTITUTE, GUINDY, November, 1949

ISSN:0003-2654    

DOI:10.1039/AN9507500076

出版商:RSC    

年代:1950

数据来源: RSC