ISSN:0003-2654    

DOI:10.1039/AN94873FX033

出版商:RSC    

年代:1948

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN94873BX035

出版商:RSC    

年代:1948

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN94873FP051

出版商:RSC    

年代:1948

数据来源: RSC

摘要:

THEBOROUGH OF SHREWSBURYWATER UNDERTAKINGAppointment of Chemist & BacteriologistApplications are invited for the above permanent appoint-ment at a salary in accordance with Grade I11 of the NationalJoint Council Scales for A.P. & T. Staffs, commencing salary€450 per annum with annual increments of ,616, subject tosatisfactory service, rising to 4495 per annum.The successful candidate will be required to pass a medicalexamination and to contribute to the Corporation’s Super-annuation Fund.The Council will be prepared to consider endeavouring toassist the successful applicant to obtain living accommodationif the circumstances warrant it.Applications, stating age, education, qualifications, and fulldetails of experience and quoting not more than three personsto whom reference ’may be made, should reach the under-signed not later than Wednesday, 20th October, 1948.GUILDHALL, Town Clerk.S. R.H. LOXTON,SHREWSBURY.UNIVERSITY OF ABERDEENLECTURESHIP IN CHEMISTRYAp lications are invited for the post of Lecturer inChedstry with special qualifications in Analytical Chemistryand some inorganic interests. Salary ,6600 to ,6760, accordingto qualifications and experience, with F.S.S.U. and children’sallowance. Form of ap ication and conditions of appoint-ment may be obtained fom the undersigned.H. J. BUTCHART,THE UNIVERSITY, Stwebry.ABERDEEN.T H E Civil Service Commissioners invite ap lications forpermanent appointments as Experimental 8ficers in theChemical Inspectorate (Atomic Energy), Ministry of Supply.Candidates must be not less than 28 years of age with aminimum qualification of Higher School Certificate (orequivalent) with chemistry as a principal subject and havehad several years experience of modern methods of chemicalanalysis.Men: QiOO - ,6660Women: L4400 - ,6526Inclusive London salary scales are:Provincial scales are slightly lower.Further particulars and application forms from the Secre-tary, Civil Service Commission, Scientific Branch, 27,Grosvenor Square, London, W.l, quoting No.2297. Com-pleted applications must be returned by 4th November, 1948XPERJENCED Analytical Chemist required for theEanalytical section of research laboratories. Commencingsalary not less than 4460 p.a. F.S.S.U.benefits. Applygiving full particulars of qualifications and experience toDirector, B.L.R.A. Laboratories, Hill View Gardens, Hendon,N.W.4.RADUATE or equivalent required for the AnalyticalGLaboratory of the British Coal Utilisation ResearchAssociation. Apply in writing to the Assistant Secretary,Randall Road, Leatherhead.SSISTANT TECHNICAL OFFICERS wanted for WorksAAnalytical Department . Applicants should have a PassDegree in Chemistry or its equivalent. Salary in accordancewith experience and training. Apply in writing to StaffDepartment, Imperial Chemical Industries, Limited, HexagonHouse, Blackley, Manchester, 9. Reference W.A.WELL-ESTABLISHED analytical and consultingApractice of good standing in Shanghai, China, offers apartnership with a view to eventual purchase of practice toan experienced qualified analyst.Applicants should com-municate with the Editor or with Mr. D. G. Glenn Allen,F.R.I.C., c/o Chartered Bank 38, Bishopgate, London, E.C.,in the first instance, from whom further particulars can beobtained.ANALYST-M.Sc. with 6 years’, or Ph.D. with 2 years’analytical experience. Applicant should be thoroughlyfamiliar with recent advances in analytical methods, Initialsalary between $3450 and $4060, depending on qualificationsand experience. Write to Personnel Office, National ResearchCouncil, Ottawa, Ontario, Canada.ANALYST viiACANCIES for Analysts exist in the Antibiotics (EpsomVSurrey) and Pilot Plant (Tonbridge, Kent) Divisions okthe Central Research and Development Department of theDistillers Company Limited.Applicants should be between20 and 30 years of age and possess a B.Sc. degree in Chemistryor A.R.I.C.Applications should be submitted to the Controller ofResearch and Development, The Distillers Company Ltd.,21, St. James’s Square, London, S.W.1.A N INTERESTING OPPORTUNITY occurs for a youngqualified Chemist, experienced in Sauce and Food manu-facture with company of International Reputation. Repliesstating age, experience, etc., will be treated in strict con!fidence. Salary will be a generous one, commensurate withexperience and qualifications. Write Box 3690, THE ANALYST,47, Gresham Street, London, E.C.2.NALYST required for analytical research in connectionAwith pharmaceutical products.Pharmaceutical qualifica-tion or previous experience in this field. Salary in accordancewith qualifications and experience. Apply initially in writingquoting reference number 1943 to the Personnel Officer,May &k Baker Ltd., Dagenham, Essex.NALYTICAL Chemist, age 26-35, preferably graduate orAA.R.LC., for Analytical Laboratory of Industrial ResearchOrganisation. Work is varied and candidates to be wellacquainted with modern analytical techniques and able totrain assistants in these methods. Salary according toexperience and qualifications, etc., but not less than ,6600.Write Box No. 3692, THE ANALYST, 47, Gresham Street,London, E.C.2.VACANCY occurs in a large consulting laboratory-inALondon dealing with foods and Pharmaceuticals for aSenior Assistant Chemist.Man with Branch E, F.R.I.C.,preferred, but must be capable analyst and organiser. Com-mencing salary €700. Possibility of salaried partnership later.Write Box 3693, THE ANALYST, 47, Gresham Street, London,E.C.2.WANTED for binding ANALYST, November 1933,February March and December 1929, Index 1928September aAd October 1925 September 1919 April 1918’December 1914, March, JunGand July 1913, komplete sei1911, May to December and Index 1910. Write Box 3691,THE ANALYST 47, Gresham Street, London, E.C.2.ANALYTICALLY STANDARDISEDSAMPLESNow availableFor Universities, and Technical Colleges,Special Series which includes Carbon andelloy steels ; cast irons ; non-ferrous alloysand assorted mineralsList No.3 5 1 ~ free on request fromBUREAU OF ANALYSED SAMPLESLTD.234, Marton Road, MIDDLESBROUCH‘‘ ANfiOID ” (reg’d.)SYSTEM of RAPID ANALYSISRAPID 15 MINUTE METHODFOR SILICONIN STEEL AND CAST IRONAbsorptiometric method utilising theyellow silico-molybdate complex.Booklet No. 3 3 6 ~ on request from234, Marton Road, MIDDLJSBROUGH(ElETACLuEL(f1CAL)RIDSDALE i? CO., LTD....Vlll THE ANALYSTSpecify “DIFCO,” THE TRADE NAMEOF THE PIONEERS, in the research anddevelopment of Bacto-Peptone andDehydrated Culture MediamoreGAMINO ACIDSBAIRD & TATLOCK(LONDON LTD.)Sole Agents for Great Britain and IndiaE.C.214-17- ST. CROSS STREET, LONDON,Eight more amino acids are now available in adequate quantities for laboratoryuse from normal B.D.H.production, and again enquiries for larger amounts areinvited. The new additions are :-DL-Glutamic acid DL-Histidine DL-NorvalineG1 ycocyamine DL-MC thionine DL-Ornithine (hydrobromide)(also DL-Histidine monohydrochlorideDL-Isoleucine DL-TyrosineDL-Histidine dihydrochloride)Prices may be obtained on request for these substances as well as for the aminoacids already announced as in regular production :-DL- Alanine L-Leucine DL-SerineL-Arginine hydrochloride DL-Leucine DL-Tr yptophaneDL-Aspartic acid L-Lysine hydrochloride L-TyrosineL-Glutamic acid DL-Norleucine DL-ValineDL-PhenylalanheDevelopment work continues on L-glut amhe, DL-lysine hydrochloride andDL-threOnine, and also on p-alanine and sarcosine. It is expected that these andothers will be ready for issue shortly.T H E B R I T I S H D R U G H O U S E S L T D .B . D . H . L A B O R A T O R Y C H E M I C A L S G R O U PTelephone: Poob 962 P 0 0 1 E D 0 R S E T Telegrams: Tetradome PooleAAlLChemIZ aBlood Culture MediaBacto-Brain Heart Infusion, when made up for use, is an excellcnt liquid mediumfor primary cultivation of many pathogenic bacteria from the blood stream, particularlythe Streptococci, Pneumococci and Meningococci.Bacto-Tryptose Phosphate Broth is a very satisfactory infusion-free liquid mediumwhich supports luxurient growth of the fastidious pathogens.Bacto-Blood Agar Base, enriched with sterile blood when it is made up for use,permits development of characteristic haemolytic reactions by colonies of the inoculatedbacteria.Bacto-Tryptose Agar, particularly adapted for isolation of the Brzxella, is also a veryuseful medium for isolation of bacteria from the blood stream. It is an excellent base towhich the blood specimen may be added for direct cnumeration of organisms in bacteremias

ISSN:0003-2654    

DOI:10.1039/AN94873BP055

出版商:RSC    

年代:1948

数据来源: RSC

摘要:

SEPTEMBER 1948 THE ANALYST Vol. 73 No. 870 PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS Determination of p,p'-DDT in Commercial Samples BY R. L. WAIN AND A. E. MARTIN (Read at the Meeting of the Society on May 5th 1948) A NUMBER of worker^^^^^^^^ have employed dehydrohalogenation with boiling alcoholic alkali as the basis of a method for estimating jb,p'-DDT. We have dem~nstrated,~ however that at this temperature the reaction is not quantitative slightly more than one equivalent of hydrogen chloride per molecule being released owing to the simultaneous formation of traces of bis-(p-chloropheny1)-acetic acid. Nevertheless at ordinary temperatures we found that decinormal alcoholic alkali removed hydrogen chloride quantitatively from jb,f-DDT t h 11s permitting exact determination of the substance.Such a procedure is not directly suitable for the estimation of the p,p' isomer in commercial samples owing to the presence of con-comitant materials7 some of which also yield chloride ion under these conditions.8 The most important of these substances is o,p'-DDT the dehydrohalogenation of which has been studied by Cristol.6 He showed that this isomer which may occur in commercial samples to the extent of 8 to 21 per cent.,' reacts with potassium hydroxide in 92-6 per cent. alcohol at 20.1" C. at only 1/67th the rate of the p,p' isomer. These results have led to the methods of Soloway et at.* and of LaClairg for the estimation of p,p'-DDT in commercial samples, in both of which methods the amount of chloride liberated under specified conditions is related to the content of p,p'-DDT by means of a regression equation.The object of this paper is to present our information on the rates of dehydrohalogenation of o,p'-DDT mixtures of this with the p,p' isomer and commercial samples of DDT. MATERIALS USED-p,p'-DDT-The commercid material crystallised three times from alcohol. Colourless needles having m.p. 109" to 109.5" C. o,p'-DDT-A sample kindly supplied by Dr. I. E. Balaban was recrystallised twice from methyl alcohol and gave colourless plates m.p. 74" to 75" C. which did not depress the melting-point of an analysed specimen. Commercial samples of DDT-Five samples each representing an individual plant batch, were available. They were kindly provided bg Dr. Balaban together with a statement of their p,p'-DDT content as determined by his crystallisation method.lO Absolute alcohol dried by standing over freshly ignited quicklime and fractionated the fraction b.p.78" to 78.5" C. being collected. Standard alcoholic potassium hydroxide solution-A.R. potassium hydroxide was heated under reflux with redistilled absolute alcohol and the solution was cooled filtered and standardised. EXPERIMENTAL The concentration was 0.1964 N . (a) Rate of reaction of o,p'-DDT-500-mg. quantities of o,jb'-DDT were weighed into separate 350-ml. conical flasks and dissolved in 25 ml. of absolute alcohol. Alternatively, 26-ml. aliquots equivalent to 500 mg. of o,f-DDT of a standard solution in absolute alcohol were used. The flasks were stoppered and placed in a thermostat at 23OC.and after 47 480 WAIN AND MARTIN DETERMINATION OF ~ ~ ' - D D T IN [Vol. 73 temperature equilibrium was attained 25 ml. of the standard alcoholic potassium hydroxide were added to each from a pipette. The final concentration of alkali was 0.0982 M and that of o,fi'-DDT 0.0282 N. Each determination was performed in duplicate. The reaction was stopped after various times by addition of 25 ml. of N nitric acid and the liberated chloride then estimated by Volhard's method as previously de~cribed.~ The results are given in Table I. TABLE I DEHYDROHALOGENATION OF O,~'-DDT AT 23" c. Equivalents of C1' liberated per molecule of DDT (average of duplicates) Time min. 30 0.101 46 0.183 60 0-206 120 0.334 180 0.457 The equation for a bimolecular reaction may be expressed-where a is the initial concentration of o,p'-DDT b is the concentration of potassium hydroxide, x is the fraction of DDT consumed in time t and K is the reaction constant.Values of log,.{ (1 -s)/(l - x ) } were plotted against t and a straight line was obtained. The reaction is thus bimolecular and under the conditions used viz. employing absolute alcoholic potassium hydroxide at 23" C. the reaction constant K is 0.0008971 litres/mol./sec. (b) Rate of reaction of p,p'-DDT-The rate of reaction of @,$'-DDT with alcoholic alkali under the same conditions was calculated from the results presented in our previous communication.6 This dehydrohalogenation was also found to be bimolecular with a reaction constant of 0.03704 litres/mol./sec.(c) Rate of reaction of mixed DDT isomers-Standard solutions in absolute alcohol were prepared containing p,p'- and o,p'-DDT in the respective ratios 90/10 80/20 and 70/30 by weight. Of each solution 25 ml. contained 500 mg. of the mixed isomers and this volume was allowed to react as before with 25 ml. of the standard alcoholic potassium hydroxide at 23" C. for various times. Liberated chloride was estimated in the usual manner. The results are presented in Table 11. Curves expressing the rates of reaction of o,$' and p,$'-DDT and of the mixtures of these isomers with the standard alcoholic alkali are shown in Fig. 1. TABLE I1 DEHYDROHALOGENATION OF MIXTURES OF @,@'- AND O,P'-DDT AT 23" C. Time min. 16 30 60 90 120 160 180 Equivalents of C1' per gram molecule of total DDT 80% p,p' 4- 20% o,p' A 90% p,p' 4- 10% o,p' 70% p,p' 4- 30%;,P' 0-867 0.907 0.922 0.922 0.936 0.923 0-949 0.764 0.817 0.840 0.844 0,869 0.869 0-887 0.670 0.725 0.764 0.765 0.786 0.802 0-826 (d) Rate of reaction of commercial samples of DDT-5 g.of each sample previously dried in vacuo were accurately weighed and dissolved in absolute alcohol and the solution was diluted to 250 ml. Of each solution 25-ml. aliquots were allowed to react for various times with equal volumes of the approximately 0.2 N alcoholic potassium hydroxide solution at 23" C. and the liberated chloride was estimated as before. The results are given in Table 111, which also shows the percentage of p,fi'-DDT in each sample as determined by the crystallisa-tion method.The amount of chloride liberated cannot of course be expressed in this case as equivalents of C1' per molecule of DDT although the data in Table I1 can be readil Sept. 19481 COMMERCIAL SAMPLES 481 converted to mg. of C1’ per gram of DDT by multiplying by 100 the molecular weight of DDT being almost exactly ten times the atomic weight of chlorine. TABLE I11 DEHYDROHALOGENATION OF COMMERCIAL DDT SAMPLES AT 23” C. Milligrams of C1’ liberated per gram of sample V L u L “a 0.6. z 60. s - 0 a2 V 4 0 -n E L 00 ._ - t 20. Time min. 15 30 60 90 120 180 I 2 = 90!10 Pure mtxture 3 = Sample E (80.8% p,p’-DDT) 4 R@:20 Pure mixrut-e = Sample C (89.2’4 p,p’-DDT) Sample B 77.2 82.2 84.5 85.7 87.0 88.6 (73.7% P>P’) Sample A 80.5 85-4 87.1 88.3 89.3 90.7 (774% P*P? .Sample E (80.8% P>P? 83.1 87.2 89- 1 89.7 90.7 91.8 Sample D 84.0 87.7 89.6 90-2 90.9 92.0 (82.8% PjP’) - Sample C 88.4 92.9 94-1 94.5 94.8 96.3 (89.2% P,P’) DISCUSSION The dehydrohalogenation of both o,p’- and P,P’-DDT by means of absolute alcoholic potassium hydroxide at 23” C. has been shown to be a second-order reaction the reaction constants being O.OOO897 1 and 0.03704 litres/mol./sec. respectively. These results may be compared with those of CristoP who using 92.6 per cent. ethanol at 20-1”C. found both reactions to be of the second order with constants of 0.000371 and 0.02480 respectively.The effect of dilution of the solvent with water on the rate constant of the reaction was shown by Cristol to be consistent with electronic considerations.69ll Thus by increasing the percentage of water in his aqueous alcohol solvent the rate constant for @,p‘-DDT was decreased from 0.0248 for 92.6 per cent. alcohol to 0-0189 for 87 per cent. and to 0.0132for 76 per cent. It is clear therefore that the present results with absolute alcohol are not inconsistent with those of Cristol although under our conditions the ratio of the rates of dehydrohalogenation for the o,p’ and p,p’ isomers is only 1 41.3. As would be expected the rates of release of chloride ion from mixtures of the two pure isomers lie between those for $,fit- and o,$’-DDT (Fig. 1) 0 0 n L E c ," 90 3 - 2 80: Commercial samples -Q-T o } Pure mixtures of DDT isomers + og tion was obtained the curve within the limits investigated being linear (Fig.3). The data for the mixtures of the pure isomers (Table 11) also gave a straight line (Fig. 3) from which it is evident that the +,p'-DDT content of such a mixture can be accurately determined (cf. Fig. 3 that the commercial sample line is higher Soloway et d8). It will be observed from . $,+'-DDT contents of the commercial samples as obtained by the crystallisation method have been accepted a point which may be open to objection as no method is yet available for the 1 . accurate determination of $,p'-DDT in the 70 80 9o 100 commercial product. The crystallisation P$'-DDT 74 figures howeier do afford a -comparison between the different samples.I t is also signifi-cant that the commercial sample line and that for the pure isomers when extrapolated meet at a point corresponding approximately to 100 per cent. of +,p'-DDT. On the basis of these results the relationship between chloride liberated from a commercial sample under our conditions and its content of p,$'-DDT may be expressed as follows-Percentage of +,$'-DDT = (1.56 x mg. of C1' per gram of sample) - 58.1 This equation is given only tentatively for in view of the fact that the proportion as well as the amount of the different impurities in separate batches of commercial DDT can vary many samples would have to be critically examined before such an equation could be considered to be of general applicability.The results presented here however are in general agreement with those of LaClai~-,~ who also found a linear relationship between the chloride ion liberated from a series of commercial samples and their +,+'-DDT content as determined by a crystallisation method. The method of Soloway et aL8 for the estimation of $,p'-DDT in commercial samples although similar employs a regression equation that was calculated from the results of the decomposition of mixtures of the +,p' and o,+' isomers containing no other compounds. Our results confirm their findings that such a procedure will tend to give high results with commercial samples owing to the liberation of chloride from other materials present. SUMMARY The dehydrohalogenations of o,p'- and of $,$'-DDT by means of absolute alcoholic potassium hydroxide at 23" C.have been shown to be second-order reactions with rate constants of 0@008971 and 0.03704 litres/mol./sec. respectively. These results are in agreement with other published work when differences in technique are taken into account. The quantities of chloride ion released from mixtures of these isomers in various pro-portions and from commercial samples of DDT on treatment with absolute alcoholic alkali at 23" C. have been determined. When these values were plotted against the $,p'-DDT content (determined in the commercial samples by a crystallisation method) straight lines were obtained which when extrapolated met at a point corresponding to 100 per cent. p,$'-DDT. A regression equation has been tentatively suggested ; it should enable dehydro-halogenation of commercial samples under our conditions to give a close approximation to the p,$'-DDT content.Fig. 3. Relation between p,p'-DDT content and chloride liberation in 60 minutes at 23°C Seyt. 19481 COMMERCIAL SAMPLES REFERENCES 1. 2. 3. 4. 5. Wain R. L. and Martin A. E. ANALYST 1947 72 1. 6. 7. Haller H. L. et al. Ibid. 1945 67 1591. 8. 9. 10. 11. Neal P. A. et al. U.S. Pub. Health Serv. Pub. Health Depts. Sup#. 1944 No. 177. Powning R. F. J . Council Sci. Ind. Res. Australia 1945 18 121. Gunther F. A. Ind. Eng. Chem. Anal. Ed. 1945 17 149. Wichmann H. J. et al. J . Assoc. Off. Agr. Chem. 1946 29 188. Cristol S . J. J . Amer. Chem. SOC. 1945 67 1494. Soloway S. B. et al.“Soap and Sanit. Chemicals,” 1946 Blue Book p. 216. LaClair J. B. Ind. Eng. Chem. Anal. Ed. 1946 18 763. Balaban I. E. and Calvert R. D. Ibid. 1946 18 339. Hughes E. D. and Ingold C. K. Trans. Faraday SOC. 1941 37 657. WYE COLLEGE (UNIVERSITY OF LONDON) KENT 483 DISCUSSION Mr. D. E. BUTTERFIELD asked if the curve relating milligrams of chloride ion liberated to the percentage of p,p’-DDT was valid for various conditions of dehydrohalogenation or only for the conditions described by the authors. In reply Dr. Wain stated that as the dehydrochlorination had not been investigated under other conditions it was impossible to give a precise answer to the question. La Clair as already stated had obtained similar results using mild conditions not greatly different from those employed in the present work.The use of more drastic alcoholic alkali treatment would be unsatisfactory owing to the Occurrence of secondary reactions in which chloride ion becomes liberated. Mr. L. C. UNSTEAD-JOSS asked if the nature of the substances present in commercial DDT that lose chlorine more rapidly than the p,p’-isomer with alcoholic alkali was known and could they be removed to facilitate the determination ? Dr. Wain reminded the speaker that commercial DDT was a very complex mixture. Certain constituents had been isolated which could yield more than one molecule of hydrochloric acid under specified conditions but no method had been proposed whereby such substances could be removed prior to the estimation. Dr. H. LIEBMANN asked what was the minimum quantity of DDT with which the described method could deal in the analysis of residues.Dr. Wain replied that in work on the estimation of pure p,p‘-DDT residues on leaf tissues carried out at East Malling Research Station under his supervision quantities as low as 200mg. had been determined by the dehydrohalogenation method. The accurate estimation of residual deposits of commercial DDT on leaf tissue was complicated by the loss of various constituents during weathering and by penetration into the leaf tissue. These factors altered the composition of the deposit. Dr. D. $1. WRIGHT enquired about the extent of the danger to bees from fruit-blossom spraying with liquids csntaining DDT and whether earlier pre-blossom spraying was preferable so as to avoid the contact toxicity but retain the stomach toxicity to leaf-eating insects.Dr. Wain replied that whereas it was probably advisable to avoid spraying the open blossom with DDT preparations recent work had shown that a t the concentrations normally used this insecticide even on open blossom was practically harmless to foraging bees. Benzene hexachloride preparations however were dccidedly toxic. Dr. HAMENCE asked (1) if DDT was easily hydrolysed by water; if one had a few leaves to test would there be much risk of decomposition in extracting any residue with alcohol? (2) which of the colour reactions for DDT that have been recommended in the American literature did Dr. Wain consider the most useful ? (3) in examining commercial DDT what did Dr. Wain consider a reasonable minimum content of the active isomer? Alcohol was not a good solvent for extracting the residual deposits from leaves as it did not dissolve DDT readily. In his own experiments with pure p,p’-DDT Dr. Wain had obtained satisfactory results by washing the leaves with benzene. Such treatment however removed the surface deposit only ; the insecticide that had penetrated the leaf tissue could be recovered only by Soxhlet extraction. Of the colour reactions for DDT the speaker considered that of Schechter and Haller involving nitration foilowed by treatment with sodium methoxide, to be the most satisfactory and selective for p,p‘-DDT. Seventy per cent. was a reasonable minimum content of p,p’-DDT in a commercial sample. Dr. Wain stated that DDT was not hydrolysed by water

ISSN:0003-2654    

DOI:10.1039/AN9487300479

出版商:RSC    

年代:1948

数据来源: RSC

摘要:

484 MITCHELL TRESADERN AND WOOD ANALYSIS OF PYRETHRLM [Vol. 73 The Analysis of Pyrethrum Flowers by the Seil and Wilcoxon - Holaday Methods BY W. MITCHELL F. H. TRESADERN AXD S. A. WOOD THE active principles of pyrethrum flowers consist of two groups of esters known respectively as “pyrethrin I ” and “pyrethrin 11.” These terms were formerly thought to apply to chemical entities the first being regarded as the chrysanthemum monocarboxylic ester of a keto-alcohol pyrethrolone ” and the second as the chrysanthemum dicarboxylic monomethyl ester of “pyrethrolone,” but recent work has shown that “pyrethrolone” is in fact a complex mixture of keto-alcohols. It is however convenient to retain the use of these terms for the two groups of esters derived from the chrysanthemum mono- and di-carboxylic acids respectively (see p.489). The ideal method of assay would obviously be one in which the active principles of pyrethrum were isolated and determined as such but this is not yet practicable. Stkudinger and Harder1 published the first chemical methods of assay and isolated the pyrethrins as a crude mixture of semicarbazones the nitrogen content of which was then determined; the results were not very satisfactory. Later this method was adapted with some success and improved by Tattersfield Hobson and Gimingham,2 but the procedure is too lengthy and troublesome to be useful in practice. Gnadinger and Cod3 devised a method based on the fact that the pyrethrins and also pyrethrolone reduce alkaline copper solutions. However, it was shown later by Acree and LaForge* that the palmitic and linoleic esters of pyrethrolone also occur in pyrethrum flowers.Presumably these esters as well as any free pyrethrolone present would be included as pyrethrins by this method. The methods in most general use at the present time are those of Sei15,6 and of Wilcoxon and H ~ l a d a y ~ ~ ~ the latter having been adopted after modification as an A.O.A.C. Official Method9 for pyrethrin I (the references cited include the most recent published revisions of these methods). Both methods are based on alkaline hydrolysis of a light petroleum extract of the flowers and separate determination of the liberated chrysanthemum mono-and di-carboxylic acids. Hence they have the advantage that the corresponding pyrethrin groups are estimated separately whereas in the methods mentioned above only a figure for total pyrethrins can be obtained.An obvious disadvantage is that any other free acids present in the extract or produced by hydrolysis and not removed in the subsequent purifica-tion procedure might cause errors. In particular any free chrysanthemum acids extracted from the drug would certainly be included in the final determination and lead to high figures for pyrethrins. These acids in the free state are known to be devoid of insecticidal activity and their inclusion would constitute a serious error. RipertlO has described a method in which free acids are removed from the extract before hydrolysis and Martin” has reported on its use; his results appear to indicate that such free acids although present in appreciable amount do not cause serious error.Later Martin and Brightwell12 described a method for the separation of the free acids from pyrethrum concentrates in mineral oil; when the original extraction of the flowers had been made with light petroleum they found the error due to the presence of free acids to be small. Since light petroleum is used as the extraction solvent in both the Seil and the Wilcoxon - Holaday methods it would appear that errors due to free acids are likely to be small; in the work described in the present paper no steps were taken to remove them from the extracts. The Seil and Wilcoxon - Holaday methods are almost identical in their preliminary stages but differ in the actual isolation of the chrysanthemum monocarboxylic acid.The first method which is an improved and modified version of the earlier acid method of Tatters-field Hobson and Gimingham,2 depends on the fact that the dicarboxylic acid is not volatile in steam whereas the monocarboxylic acid is readily volatile in steam and is so isolated. The second method utilises the fact that only the monocarboxylic acid is readily soluble in light petroleum. The monocarboxylic acid reduces Denigk’s reagent which is accordingly employed as a volumetric means of assay of the acid extracted by light petroleum. There is an extensive literature (well summarised by G. B. Gnadinger13) on the use of and comparativ Sept. 19481 FLOWERS BY THE SEIL AND WILCOXON - HOLADAY METHODS 485 The results (1) The Seil method gives low and variable results for pyrethrin I owing to partial loss of chrysanthemum monocarboxylic acid in the steam-distillation procedure (Wilcoxon' ; Pantsios14; Martinll).(2) This error in the Seil method may be partly masked and compensated by the presence of other steam-volatile acidic substances which may be included in the titration of the monocarboxylic acid (Martinll) . (3) The Wilcoxon - Holaday method as amended by Graham and LaForge,15 and later adopted as an A.O.A.C. r n e t h ~ d ~ gives fairly consistent and higher results for pyrethrin I than the Seil method; on the other hand the results for pyrethrin I1 are rather lower although the methods of determination of the latter are essentially the same in both. In view of the commercial importance of pyrethrum flowers the present lack of agreement in methods of analysis used and in the results obtained constitutes a serious problem.Since both the methods in general use depend on the determination of the chrysanthemum acids it appeared desirable to re-investigate their reliability very carefully using the pure acids for this purpose. The present paper describes this work and the application of the results obtained to the analysis of pyrethrum extracts. Before proceeding to this description it seems worth while to comment on the situation produced by the work of LaForge and Barthel,l6 and West,17 already mentioned. These workers have shown that "pyrethrolone" is not a homogeneous substance but consists of a mixture of stereo-isomerides of pyrethrolone C,,H,,O, and cinerolone CI0Hl4O2.Since they have also shown that both "pyrethrin I" and "pyrethrin 11" yield mixtures of these keto-alcohols on hydrolysis and that the proportion of cinerolone isomers present varies from 20 to 30 per cent. the terms pyrethrin I and pyrethrin I1 can now be regarded as referring only to variable mixtures of esters of the corresponding chrysanthemum acids. Whether all these individual esters are equally active as insecticides remains to be determined fully,* but meanwhile there seems to be no alternative to continuing to estimate them in two groups according to the chrysanthemum acids which they yield on hydrolysis. Obviously however, the present numerical factors used in the calculation of the pyrethrins from the determinations of the corresponding acids cannot be regarded as accurate or even constant as a basis of comparison.Hence it would probably be more correct to express the results as percentages of the respective chrysanthemum acids especially since it is these that are in fact determined. This point does not seem to have been stressed sufficiently in any publication to date. Although the customary factors are used in the present paper it is suggested that this question deserves careful consideration and may provide some explanation for discrepancies in results obtained both between various chemical methods of assay and also between chemical and biological methods. The acids used in the present work were isolated by standard methods from the products of hydrolysis of a purified pyrethrum extract and had the following characteristics.Chrysanthemum monocarboxylic acid-Colourless crystalline solid; m.p. 18-5" C. ; b.p. (0.5 mm.) 97" to 98" C.; n:' 1.4760. Found C 71.8; H 9.7 per cent.; equivalent by titration 167.8. Calc. for C&&, C 71.4; H 9.6 per cent.; equivalent 168.0. 9-Phenyl-phenacyl ester m.p. 65" C. (Wilcoxon' gives 65"). Chrysanthemum dicarboxylic acid-Colourless lozenge-shaped plates ; m.p. 168" C. (corr.) . Found C 60.9; H 6-8 per cent.; equivalent by titration 197.9. Calc. for C,,H1404 C 60.6; H 7.1 per cent. ; equivalent 198.0. 9-Phenylphenacyl ester m.p. 154" C. (corr.) (Wilcoxon' gives 164'). A. SEIL METHOD 1. Stability to alkaline hydrolysis-Appropriate weights of the acids both singly and in admixture were exposed to the conditions applying in the assay.The acids were heated under reflux with 20 ml. of 0.5 N alcoholic sodium hydroxide for 14 hours after which 200 ml. of water were added and the mixture was concentrated by results obtained by these methods in the hands of numerous investigators. appear in general to be contradictory and the main conclusions to be drawn seem to b e -* Owing to delay in receipt of American journals we had not seen the paper on this subject by W. A. Gersdorff ( J . Econ. Entomology 1947 40 (6) 878) at the time of writing the above. He shows that the pyrethrins are more active than the corresponding cinerins and that pyrethrin I and cinerin I are con-siderably more active than pyrethrin I1 and cinerin I1 respectively 486 gentle boiling to about 150ml. One gram of barium chloride dissolved in 10ml.of water was added and the volume was made up with water to 250 ml. The solution was neutralised to phenolphthalein with hydrochloric acid 1 ml. of which was added in excess and the mono-carboxylic acid was extracted by shaking with two 50-ml. portions of light petroleum (b.p. 40" to 60" C.). The extracts were washed in succession with the same portion (20 ml.) of water and this in turn was washed with 20ml. of light petroleum which was afterwards added to the main quantity along with 15ml. of water previously neutralised to phenol-phthalein. The mixture was titrated to the phenolphthalein end-point with 0.02 N sodium hydroxide with continuous shaking; 1 ml. = 0.00336 g. of the monocarboxylic acid. The original acid liquor together with the water washing of the petroleum extracts was boiled down to about 50 ml.and was then saturated with sodium chloride treated with 8 ml. of hydrochloric acid and extracted with four 50-ml. portions of ether. Each extract was successively washed with the same two portions (each 10 ml.) of water and the solvent was distilled from the united extracts. The residue was dried for 10 minutes at 100" C. and then dissolved in 2 ml. of neutral alcohol and titrated to the phenolphthalein end-point with 0.02 N sodium hydroxide; 1 ml. = 0-00198 g. of the dicarboxylic acid. The modified procedure of Green Pohl Tresadern and West,ls using 20 ml. of 0.5 N potassium hydroxide in ethylene glycol monoethyl ether as the hydrolysing agent was also employed for comparison. MITCHELL TRESADERN AND WOOD ANALYSIS OF PYRETHRUM [Vol.73 TABLE I SEIL METHOD STABILITY OF PURE CHRYSANTHEMUM ACIDS TO HYDROLYSIS PROCEDURE Solvent for alkali used for hydrolysis Alcohol Y Y Y9 Ethylene glycol monoethyl ether . . . . Ethylene glycol monoethyl ether . . Ethylene glycol monoethyl ether . . Mono-carbox ylic acid taken g. 0.0517 nil 0.053 1 0.0525 nil 0.05 10 Dicarboxylic acid taken g. nil 0.0454 . 0.0468 nil 0.0400 0.0457 Light petroleum extraction & 0.02 N NaOH Recovery ml. % 15-35 99.8 0.25 2.0 16-1 101.9 15.6 99.8 0.15 1.26 15.4 101.5 Ether extraction -7 0.02 N NaOH Recovery ml. % nil nil 22.5 98.1 22-8 98.6 nil nil 20.0 99.0 22-7 98.4 The results (Table I) show that there is no appreciable loss of either of the chrysanthemum acids and confirm that the use of ethylene glycol monoethyl ether as solvent for the alkali gives equally satisfactory results.It is recommended that this convenient and time-saving modification be universally adopted. It is possible that in a pyrethrum assay the precipitate of barium salts of fatty acids and other unwanted substances may adsorb or occlude traces %f the chrysanthemum acids but this loss is likely to be negligible at the high dilution employed. It will be noted that where the dicarboxylic acid was present some of it was apparently extracted by the petroleum ether; this point will be dealt with later. TABLE I1 SEIL METHOD STABLLITY OF PURE CHRYSANTHEMUM ACIDS TO STEAM DISTILLATION PROCEDURE Sulphuric acid present 1 d .o f N n 99 5 mi. of N 1 ml. of 98% 1 ml. of N 99 Monocarboxylic Dicarboxylic acid taken acid taken g. g. 0.0473 nil 0-0563 Y9 0-0422 99 0.0498 99 0.0545 99 0-0562 Y9 nil 0.0462 >9 0.0s 19 0,0374 0.0406 0-0452 0.0561 Light petroleum extraction of distillate P 0.02 N NaOH Recovery ml. % 12-1 86.0 15.0 89.5 11.2 89-2 12.7 85.7 13-6 83.8 13-3 79.5 0.05 0.4 0-05 0.3 9-25 83.1 12-1 90.0 Ether extraction of residue JI 0.02 N NaOH Recovery ml. % 0.55 2.3 0-5 1.8 0.46 2.1 0.4 1.6 1-1 4.0 1.3 4.6 23.2 99.4 26.15 99.8 21.2 103-4 28.9 102. Sept. 19481 FLOWERS BY THE SEIL AND WILCOXON - HOLADAY METHODS 487 2. Steam distillation stage-Appropriate weights of the acids were titrated with 0.02 N sodium hydroxide and the solutions were diluted with water to 200 ml.acidified with sulphuric acid and steam distilled so that 300 ml. of distillate was collected in 12 hours and the final distillation residue measured about 20ml. The assay was completed as described by Seil.s The amount of sulphuric acid used was varied as shown in Table 11. The results indicate that under the conditions of the Seil steam distillation procedure the dicarboxylic acid is recoverable almost quantitatively but that the monocarboxylic acid shows a variable loss of 10 to 25 per cent. (this latter result is in line with the results of Wilcoxon7 and of Pantsios14) coupled with an apparent and variable increase of the dicarboxylic acid in the distillation residue.This apparent increase is not shown when the dicarboxylic acid only is present but occurs whenever the monocarboxylic acid is distilled either alone or in presence of the dicarboxylic acid. I t has been suggested that the excess of sulphuric acid present has a considerable effect on this loss of monocarboxylic acid and Martinll has claimed that the use of only 1 ml. of N acid eliminates it. This was not borne out by the results in Table 11 although the use of Seil's original amount of 1 ml. of pure acid caused a distinctly increased loss. The effect was investigated further by simple boiling under reflux for 13 hours of appropriate weights of the monocarboxylic acid with water or dilute sulphuric acid. The monocarboxylic acid was incompletely condensed under these conditions and it was necessary to connect the outlet of the condenser to a trap so that any issuing vapours were passed into 20 ml.of 0.05 N sodium hydroxide. This solution was finally added to the main liquor 1 ml. of hydrochloric acid was added and the mixture was extracted with two 50-ml. portions of light petroleum (b.p. 40" to 60" C.). The extracts were washed successively with two 10-ml. quantities of water and then titrated as in the Seil method (Table 111). This point is discussed later. TABLE I11 RECOVERY OF PURE CHRYSANTHEMUM MONOCARBOXYLIC ACID AFTER BOILING UNDER REFLUX UNDER VARIOUS CONDITIONS Monocarboxylic acid taken €5 0.0627 0.0557 0-0564 0.0709 0.06 1 1 0.0682 0.0538 0-0504 Light petroleum extraction Conditions of boiling under reflux liquid present 0.02 N NaOH ml.200 ml. of water 18.55 99 99 16.5 50 ml. 99 16.7 18-2 97 9 7 + 99 of pure 97 99 6.8 97 Y7 + 99 *9 99 99 8-7 200 ml. of water + 1 ml. of N sulphuric acid 200 ml. of 20% w/v aqueous NaCl solution (b.p. 105" C . ) 50 ml. of water; steam injection until total volume was 14-95 14-55 250 ml. \ Recovery 99-4 99.5 99.5 86.0 37.4 42-8 93.3 97.0 % It will be noted that boiling under reflux with water alone caused little or no loss even in relatively concentrated solution. On the other hand the presence of 1 ml. of N sulphuric acid caused a loss of the order normally observed in the Seil assay and the loss was much greater when more sulphuric acid was present. It is interesting to observe that in absence of mineral acid the injection of steam caused a small but significant loss.An even more marked loss was caused by boiling under reflux with 20 per cent. w/v aqueous sodium chloride solution (b.p. 105" C.) in place of water. Further distillation experiments both with and without steam injection were carried out (Table IV). It will be noted that the losses during steam distillation were just as great with water alone as when Seil's original amount of sulphuric acid was present and that these losses were of the same order as has already been recorded for the Seil method. Distillation without steam injection and in absence of mineral acid on the other hand showed no loss provided that the process was completed in 1 hour; otherwise small losses were observed.It would appear that under the Seil assay conditions the loss is caused only to a minor extent by the presence of mineral acid and that it is primarily an effect of heating. It may be that steam distillation owing to liberation of latent heat exposes the acid to slightly higher local temperature than simple boiling with water and the presence of mineral salts will also raise the boiling point of the mixture; the period of distillation also appears to be important and the rate of distillation should accordingly be as high as possible 488 MITCHELL TRESADERN AND WOOD ANALYSIS OF PYRETHRUM [Vol. 73 In view of these results it becomes obvious that the present Seil method cannot be expected to give accurate results for pyrethrin I and it is also clear that the use of slightly differing conditions for steam distillation in different laboratories could account for the known lack of agreement in the results obtained.It is possible that in places of high altitude such as Nairobi the magnitude of the error would be less owing to lowering of the boiling-point of the distillation mixture. Later in this paper a modified Seil method using ordinary TABLE IV RECOVERY OF PURE CHRYSANTHEMUM MONOCARBOXYLIC ACID AFTER DISTILLATION UNDER VARIOUS CONDITIONS Mono-carboxylic acid taken g. 0.0542 0.0617 0.0564 0.0593 0.0582 0.0614 0.0574 0.0642 Duration ,-of hours 1) Conditions of distillation distillation 200 ml. of water + 1 ml. of pure sulphuric acid. Steam distillation 300 ml.of distillate; residue concentrated to 30 ml. As above 14 200 ml. of water. No sulphuric acid. Otherwise as above lt 200 ml. of water. No sulphuric acid. Steam distilla- 1) tion 300 ml. of distillate. Volume of residue kept at 200 mi. throughout 200 ml. of water. No sulphuric acid. No steam injec- 2 tion; 160 ml. of water added gradually during process; 300 ml. of distillate; residue concentrated to 50ml. finally :+ As above As above As above 1 Light petroleum extraction - 0.02 N NaOH Recovery ml. % 13.8 85.5 16.3 88.8 14.9 88.8 15.7 88.9 16-2 93.5 17.6 96.3 17.05 99.8 19.05 99.7 distillation instead of steam distillation will be shown to give results for total pyrethrins in good agreement with those obtained by the Wilcoxon - Holaday method.Experiments were made to determine the reasons for the loss of monocarboxylic acid. No trace of evolved carbon dioxide could be detected when the acid was steam distilled, so that decarboxylation did not appear to be involved; since the dicarboxylic acid shows no loss under similar conditions one would not expect decarboxylation to be the explanation. The possibility of hydration perhaps followed by lactone formation was then considered. Several of the experiments described above were therefore repeated. In each the distilla-tion residue was extracted with light petroleum to remove any traces of undistilled acid; TABLE V RECOVERY OF PURE CHRYSANTHEMUM MONOCARBOXYLIC ACID AFTER DISTILLATION OR BOILING UNDER REFLUX UNDER VARIOUS CONDITIONS SHOWING RECOIVERY OF ALTERED ACID FROM RESIDUE Light petroleum Light petroleum extraction of extraction of Duration distillate saponified residue Mono- of -g* hours ml.% ml. % 0.0695 200ml. of water. No sulphuric acid. 1) 18-3 88-6 1-95 9.4 carbox ylic distilla- 0.02 N 0-02 N acid taken Conditions of distillation etc. tion NaOH Recovery NaOH Recovery Steam distillation 300 ml. of distillate; residue concentrated to 30 ml. was maintained at 200 ml. throughout w/v NaCl solution (b.p. 105" C.). Time 2 hours (compare Table 111) during distillation. No steam injection. 300 ml. of distillate. Residual volume 50 ml. 0.0642 As above except that residual volume l& 17.0 89.0 1.7 8.9 0.0624 Boiled under reflux only. 200 ml. of 20% - 17.3 93.2 1.2 6.5 0.0650 200 ml.of water + 160 ml. added gradually 2 16.5 94.7 0.75 4.6 16-0 96.6 0.26 1.5 P 16.1 99.8 0-02 0.1 0.0567 As above 0.0542 As abov Sept. 19481 FLOWERS BY THE SEIL AND WILCOXO?; - HOL.4DAY XETHODS 489 only negligible amounts were so extracted. The residue was then boiled under reflus with 5 ml. of N sodium hydroxide for 30 minutes cooled acidified (to Congo red) with hydrochloric acid and extracted with two 50-ml. quantities of light petroleum. The extracts were washed successively with the same portion (20 ml.) of water and were then titrated as in the Seil method. The end-points were not very sharp but in every instance a quantity of acid, calculated as chrysanthemum monocarboxylic acid was indicated sufficient to account for practically all the loss observed in the preliminary treatment (Table 1').It seems very likely therefore that the loss is due to formation of a hydroxy-acid or a lactone or both. From the formulae of the trans-chrysanthemum acids it will be observed that the mono-carboxylic acid (I) unlike the dicarboxylic acid (11) has a side-chain with a gem-dimethyl grouping which is identical with the terminal part of the citronellal molecule (111). Bearing in mind that this latter substance can be hydrated in presence of acids to give hydroxy-citronella1 (IV) it is suggested that the monocarboxylic acid may undergo a similar hydration to give a hydroxy-acid (V). Staudinger and RuzickalS have shown that pyrethrum contains the trans form of the monocarboxylic acid. From steric considerations the corresponding trans-hydroxy-acid would be unlikely to form a lactone though the cis-hydroxy-acid should be capable of ready lactonisation (VI).Further work is now in hand with a view to isolating and characterising these substances and it is hoped that it may form the subject of a later paper. HOOC.CH HOOC.CH (CH3)2cCH.CH C(CH,) (1) (CH,),C+CH.CH <: (11) OHC.CH,.CH(CH,).CH,.CH,.CH C(CH,) (111) OH I OHC.CH2.CH(CH3) .CH2.CH2.CH,.C(CH,)2 H 0 OC . CH OH A I (CHJ2C - CH . CH2. C(CHJ2 (V) Preliminary results have shown that a small proportion of a lactone does in fact, appear to be formed but that the main yield is of an acid which is readily soluble in ether and slightly soluble in light petroleum. It is less readily steam-volatile than is chrysanthemum monocarboxylic acid and these findings probably provide an explanation of the anomalous figures for the dicarboxylic acid recorded in Table 11.In the normal Seil assay of pyrethrum extracts we have observed that the aqueous distillate after extraction with light petroleum as usual normally yields a further significant amount of acid to ether. While part of this is certainly extraneous volatile acid mentioned later it is possible that some of the altered monocarboxylic acid is also present. B. WILCOXON - HOLADAY METHOD 1. Stability to alkaline hydrolysis-The procedure used for hydrolysis is so nearly identical with that used by Seil that it seemed unnecessary to consider it further in view of the reassuring results already obtained above (Table I). 2. Mercury reduction stage-Appropriate weights of the acids were dissolved in 10-ml.volumes of 0.1 N sodium hydroxide and these solutions were used for this part of the process. as described in the A.O.A.C. methoda; the revised factor (1 ml. of 0.01 M potassium iodate = 0.00292 g.) was used. It will be seen that for the monocarboxylic acid the method gives quantitative results, provided that the official conditions are followed. On the other hand ridiculously high results were obtained when after standing for 15 minutes a t 25' C. the mixture was warmed for 1 hour further at higher temperatures. These latter results stress the importance of rigid standardisation of the procedure as already demonstrated by Bray et al. The results also show that the reaction is not as stated by Wilcoxon,' entirely specific for the monocarboxylic acid since the dicarboxylic acid gives apparent recoveries of 3 to 4 per cent.In the Wilcoxon -Holaday method it has been assumed that only the monocarboxylic acid is extracted by The results are given in Table VI 490 MITCHELL TRESADERJS AND WOOD ANALYSIS OF PYRETHRUM light petroleum but Table I shows that 1 per cent. or more of the dicarboxylic acid is also extracted. The presence of this small amount of the dicarboxylic acid would be expected to raise the apparent content of the monocarboxylic acid only about 0.03 per cent. which is not material but would of course show itself as a figure about 1 per cent. low in its own subsequent determination. This was examined by dissolving appropriate weights of the TABLE VI [Vol.73 WILCOXON - HOLADAY METHOD ASSAY OF PURE CHRYSANTHEMUM ACIDS BY DIRECT TREATMENT WITH DENIGES REAGEKT Monocarboxylic acid taken g. 0.0460 0.0582 nil nil 0.0495 0.0523 0.0496 0.0515 Dicarboxylic acid taken €5 nil nil 0.051 1 0.0623 nil nil nil nil Temperature of reaction O c. 25 25 25 25 40 60 80 100 0.01 M KIO, 15.6 19-8 ml. 0-58 0.75 18-6 23-4 27.7 56.2 Apparent recovery 99.1 99.4 3.3 3.5 110.6 130.6 163.1 3 18-6 % two acids in 200ml. of 0.05 N sodium hydroxide and completing the whole assay in the normal manner by acidifying and extracting successively with light petroleum and with ether etc. The results in Table VII do in fact confirm that normal results for the monocarboxylic acid are obtained but that the figures for the dicarboxylic acid are low to the expected extent.It will be shown later that this effect is even more marked in analyses of pyrethrum itself. TABLE VII WILCOXO~; - HOLADAY METHOD ASSAY OF THE PURE CHRYSANTHEMUM ACIDS Mono-carboxylic acid taken g. 0.061 5 0.0594 0.0723 0.0561 Light petroleum extraction Ether extraction Dicarboxylic A \ acid taken 0.01 M KIO Recovery 0.02 N NaOH Recovery 0.0520 20.9 99.2 25.9 98.6 0.0613 20.2 99.3 30.6 98.8 0-0463 24-55 99.1 23-1 98.8 0.0549 19.1 99-4 27-3 98.5 g. ml. % ml. % This difficulty can be overcome by the simple expedient of; re-extracting with light petroleum. The alkaline extract of the light petroleum (normally used directly for the mercury reduction stage) was neutralised with hydrochloric acid diluted to 200 ml.with water and then treated with 1 ml. of hydrochloric acid. The mixture was extracted with two 50-ml. portions of light petroleum and the extracts were washed successively with water (two portions each of 10ml.). The united petroleum extracts were extracted with 5ml. of 0.1 N sodium hydroxide followed by two 5-ml. portions of water and these united aqueous alkaline extracts were used for the mercury reduction stage in the normal manner. The acid liquor and washings were added to those from the initial light petroleum extraction for concentration and ether extraction of the dicarboxylic acid as usual. TABLE VIII MODIFIED WILCOXON - HOLADAY METHOD USING TWO-STAGE LIGHT PETROLEUM EXTRACTIOX ASSAY OF THE PURE CHRYSANTHEMUM ACIDS Mono- petroleum extraction Ether extraction carboxylic Dicarboxylic f-A- (-*-, acid taken acid taken 0.01 M KIO Recovery 0.02 N NaOH Recovery 0.0620 0.0554 21.05 99.1 27-8 99.4 0.0742 0.0493 25.2 99.2 24-7 99.2 0.05 15 0.07 19 37.5 .99.2 36.0 99.1 0.0559 0.0524 19-05 99.5 26-3 99.4 Two-stage light g.g. ml. % ml. Sept. 19481 491 The results (Table VIII) were satisfactory showing over 99 per cent. recovery of both acids in all tests. It is considered that the above results provide a satisfactory explanation for the fact that the figures for pyrethrin I1 tend to be slightly lower by the Wilcoxon-Holaday than by the Seil method even after allowing for possible high results for pyrethrin I1 in the latter method (see Table 11).A modification of the method on these lines is suggested in the latter part of this paper. FLOWERS BY THE SEIL AND WILCOXON - HOLADAY METHODS C. EXPERIMENTS ON PYRETHRUM EXTRACT 1. Extraneous acidic s~bstances-Pantsios~~ and others have recorded that other acids besides the chrysanthemum acids are present during the final stages of both the Seil and the Wilcoxon - Holaday methods. (a) An extract giving 15-7 per cent. of pyrethrin I and 12.4 per cent. of pyrethrh I1 by the Wilcoxon - Holaday method was used. The hydrolysis of 0.5 g. was conducted as usual and 200 ml. of the liquor filtered after the barium chloride treatment and equivalent to 0.4g. of extract was acidified (to Congo red) with hydrochloric acid and completely extracted with five 40-ml.portions of ether. Each extract was washed successively with two 20-ml. portions of water and most of the solvent was distilled. The residue was titrated to phenolphthalein with constant shaking; 28.1 ml. of 0.02 N sodium hydroxide were required. An excess of 10 ml. of alkali was added and the rest of the ether was dissipated by warming. The cooled liquid was diluted with 50 ml. of water then re-acidified to Congo red with hydro-chloric acid and extracted with four 20-ml. portions of light petroleum. The extracts were washed successively with two 10-ml. portions of water united and titrated as in the Seil method 10.1 ml. of 0-02 N sodium hydroxide were required indicating 16.7 per cent. of pyrethrin I. The acid liquor and washings from this light petroleum extraction were then extracted with four 25-ml.portions of ether. The extracts were washed successively with two 10-ml. portions of water most of the solvent was distilled and the residue was titrated: 14-2 ml. of 0.02 N sodium hydroxide were required corresponding to 13.2 per cent. of pyrethrin 11. It will be noted that in each case the figures are some 6 per cent. higher than those found by the Wilcoxon - Holaday method; also the sum of the two titrations was considerably less than the initial titration. Probably the extraneous acids are so soluble in water as to be partly lost in each successive extraction. The titration liquor from the light petroleum extraction was then subjected to the usual mercury reduction procedure and gave a result indicating 15.6 per cent.of pyrethrin I in close agreement with the known content and showing that the high result by direct titration was due to the presence of extraneous acids. The titration liquor from the ether extraction was diluted with 100ml. of water acidified to Congo red with hydrochloric acid and boiled down to 25 ml. On re-extraction with ether by the usual procedure it now gave a result of 12.3 per cent. of pyrethrin 11 again in close agreement with the known figure. It seems evident therefore that extraneous volatile acids had been present. In the determination of pyrethrin I1 by either method these acids will be dispersed by the ordinary procedure of concentrating the acid liquor before extraction. In the determination of pyrethrin I by the Wilcoxon - Holaday method extraneous acids do not seem to interfere with the reaction and thus are not detected.In the Seil method, on the other hand it has been suggested that they are included in the extraction of the distillate and hence partly offset the low results caused by the loss of monocarboxylic acid in the distillation. In the modified Seil method described later where steps have been taken to limit loss in distillation the results for total pyrethrins are in fairly good agreement with those obtained by the Wilcoxon - Holaday method whilst the acid titrated as the mono-carboxylic acid gives almost the same result when subjected to the mercury reduction procedure. Probably the high water-solubility of the extraneous acids coupled with the relatively large volume of aqueous distillate ensures that they are not extracted to any appreciable extent in the Seil method.On the whole it seems reasonable to conclude that extraneous acids do not cause serious errors in the results obtained either by the Seil or the Wilcoxon - Holaday method provided that no free chrysanthemum acids are present in the initial extract of the flowers. ( b ) In a further experiment on the same extract the Wilcoxon - Holaday method was performed as usual except that the acid liquor containing the dicarboxylic acid was not concentrated before extraction. The results showed 15.7 per cent. of pyrethrin I and 1243 per cent. of pyrethrin 11. The titration liquor from the latter determination was diluted with 50 ml. of water treated with 1 ml. of N sulphuric acid and steam-distilled so that the This was confirmed in the following experiments 492 MITCHELL TRESADER-V AND WOOD ANALYSIS OF PYRETHRUM [Vol.73 volume was reduced to 25 ml. Re-extraction as usual now showed 12.4 per cent. of pyrethrin 11 and titration of the distillate gave a result equivalent to 0.4 per cent. of pyrethrin 11. This latter liquid was made distinctly alkaline with sodium hydroxide concentrated in vacuo to 5ml. and subjected to the mercury reduction procedure with entirely negative result for the monocarboxylic acid. Evidently a small quantity of extraneous volatile acidic matter is eliminated during the concentration procedure as suggested above. 2. Sfiecificity of mercury reduction method-In order to determine whether the reaction with Denige's reagent was confined solely to monocarboxylic acid present the following experiment was carried out on the same extract as was used above 1 g.was put through the usual procedure but using double quantities throughout; the alkaline extract of the mono-carboxylic acid was adjusted to exactly 20 ml. and 10 ml. of this solution was used for the normal mercury reduction procedure showing 15.7 per cent. of pyrethrin I. From this result the amount of pure acid calculated to be present in 5 ml. was added to a further 5 ml. of the liquor along with 5 ml. of 0-01 X sodium hydroxide and the mercury reduction process was repeated giving a result of 15.6 per cent. of pyrethrin I. This agreement appeared close enough to warrant the conclusion that the reaction is specific for the monocarboxylic acid present.Holaday methods as well as the modifications of these described below were carried out comparatively on three different commercial pyrethrum extracts. The results are shown in Table IX. TABLE IX The figure for pyrethrin 11 determined as usual was 12.4 per cent. 3. Comparison of methods iiacluding suggested rnodijed methods-The Seil and Wilcoxon COMPARISON OF SEIL ~VILCOXOX - HOLADAY AND THE PROPOSED MODIFICATIONS OF THESE METHODS APPLIED TO PYRETHRUM EXTRACTS Extract -4 Extract B Extract C Pyrethrins Pyrethrins Pyrethrins & 7- & % % % I1 Total I I1 Total I I1 Total 01 / O 0 ) Method I % % % % / O Sei16 10.8 10.4 21-2 14.3 11.7 26.0 11-2 10.1 21.3 10.9 10.4 21.3 14.4 11.8 26-2 11.3 10.1 21.4 Seil modified as 12.0 10-7 22-7 15.0 12.4 27.4 11.9 10.4 22.3 described 12.1 10.7 22.8 14.9 12.4 27.3 Wilcoxon - Holaday 13.0 9.9 22.9 16.0 11.6 27.6 12.7 9.8 22.5 according to A.0.A.C.O 13-2 9.8 23.0 16.0 11.5 27-5 12.8 9.8 22.6 Wilcoxon - Holaday 12.9 10.3 23.2 15.5 11.6 27.1 12.7 10.0 22.7 modified as described 12.8 10.3 23.1 15.6 11.7 27.3 12.8 9-95 22-75 The figures confirm the expected results in that the Seil method gives very low results for pyrethrin I and distinctly high results for pyrethrin I1 as compared with the Wilcoxon -Holaday method.In view of the results recorded in Table I1 for the dicarboxylic acid, one can expect the Seil method to give pyrethrin I1 figures that are too high but the differences here appear in general to be slightly greater than the expected error would cover.The proposed modified Wilcoxon - Holaday method on the other hand gives slightly lower results for pyrethrin I but the figures for pyrethrin I1 agree more closely with those obtained by the Seil method and allowing for the error in this method appear to be of about the correct order; the figures for total pyrethrins are almost identical with those obtained by-the Wilcoxon - Holaday method as described by the A.O.A.C. The Seil method modified to avoid steam injection and the presence of mineral acid gives almost the same figures for total pyrethrins as does the Wilcoxon - Holaday method though the figures for the individual pyrethrins are rather different; it certainly gives more accurate results than does the Seil method as used at present. On the whole it would appear that the Wilcoxon - Holaday assay should be the method of choice and it is recommended that it be generally adopted, preferably with the modification described.The modified Seil method gives accurate figures for total pyrethrins and probably is more rapid to perform and requires less skilled manipulation. For routine testing it is worthy of consideration. Both methods are described in detail below Sept. 19481 FLOWERS BY THE SEIL AND WILCOXON - HOLADAY METHODS 493 General adoption of either of these methods would presumably demand some adjustment in the strength of the Official Test Insecticide issued by the National Association of Insecticide and Disinfectant Manufacturers for use as a standard in biological testing. It is our experience that dilutions of extracts to 0.1 per cent.w/v of total pyrethrins made on the basis of the present Seil method give comparable biological results on M . domestica with the O.T.I. The preparation and testing of O.T.I. has been described21 and the pyrethrins content is given as approximately 0.1 per cent. w/v on the basis of average results from both the Seil and A.O.A.C. mercury reduction methods as well as Peet - Grady results. Analyses we have made suggest that there is considerable variation from batch to batch. It would obviously be necessary that the O.T.I. be adjusted in future on the basis of the chemical method generally adopted in order to obtain comparable biological results in the Peet - Grady procedure. The general adoption of a chemical method giving more accurate results than the present Seil method is long overdue.Wilcoxon - Holaday method-12*5 g. of flowers (30-mesh powder) are extracted with warm light petroleum (b.p. 40" to 60" C.) in a continuous extractor (e.g. Bolton - Revis type or that described in the British Pharmacopoeia 1932) for 6 hours and the solvent is then recovered. The resultant extract (or 0.5 g. in the case of commercial extracts) is boiled under reflux for 30 minutes with 20 ml. of 0.5 N potassium hydroxide in ethylene glycol monoethyl ether cooled and diluted with 200 ml. of water. One gram of barium chloride dissolved in 10 ml. of water is added and after being made thoroughly uniform the volume is made up to 250ml. with water and the whole is well shaken. The mixture is filtered through a 15-cm.fluted paper and 200 ml. of the bright filtrate is acidified to Congo red with hydrochloric acid and extracted with two 50-ml. portions of light petroleum (b.p. 40" to 60" C.). The extracts are washed successively with 20 ml. of water and this washing and the original acid liquid are united and reserved (A). The -united light petroleum extracts are then extracted with four 40-ml. portions of 0.1 N sodium hydroxide; the light petroleum is discarded. The united alkaline extracts are acidified to Congo red with hydrochloric acid and extracted with two 50-ml. portions of light petroleum and the extracts are washed in succession with two 20-ml. portions of water. The acid liquor and washings are added to (A) above and reserved. The united light petroleum solutions are then extracted with 5 ml.of 0.1 N sodium hydroxide followed by two 5-ml. portions of water; the light petroleum is discarded. The united alkaline extract is then used for the mercury reduction stage exactly as described in the A.O.A.C. m e t h ~ d . ~ The reserved acid liquors (A) are treated exactly as described in the A.O.A.C. method9 for the determination of pyrethrin 11. Seil method-The hydrolysis and barium chloride treatments are performed exactly as described for the Wilcoxon - Holaday method above. The filtered liquor (200 ml.) is acidified to Congo red with hydrochloric acid then saturated with sodium chloride and extracted with four 40-ml. portions of ether. Each extract is washed in turn with two 20-ml. portions of water and most of the solvent is distilled from the united extracts.The residue (volume about 20 ml.) is placed in a flask with a short neck provided with a small but efficient anti-splash trap and connected to a condenser for distillation. Water (200 ml.) is added and the mixture is boiled vigorously over a flame water (150 ml.) being added from a tap funnel inserted through a side-neck in the flask at approximately the same rate as distillation proceeds ; the volume of the residue is reduced finally to about 25 ml. The distillate including the small amount of ether present and residue are then treated exactly as described by Seil,6 for the determination respectively of pyrethrins I and 11. SUMMARY The modified methods recommended are as follows. The accuracy of the Seil and Wilcoxon - Holaday methods has been studied systematically, using the pure chrysanthemum acids for this purpose.It is shown that the Seil method gives very low results for pyrethrin I and slightly high results for pyrethrin 11 and that these inaccuracies are largely independent of the presence of mineral acid and due rather to a temperature effect. It is suggested that the apparent loss of chrysanthemum mono-carboxylic acid is due to hydration analogous to that undergone by citronellal and that the resultant hydroxy-acid (and perhaps a lactone derived from it) is partly responsible for the slightly high figures for pyrethrin 11. A modified Seil method which avoids steam distillation and the presence of mineral acid is shown to give accurate figures for total pyrethrins compared with the Wilcoxon - Holaday method.The Wilcoxon - Holaday method is shown to giv 494 TRINDER THE ESTIMATION OF MINUTE AMOUNTS OF BORIC ACID [VOl. 73 accurate results for pyrethrin I if followed closely but to give slightly low results for pyrethrin 11 owing to incomplete separation of the chrysanthemum acids. A small modification of the method avoids this error. Application of the methods to pyrethrum extracts confirms these conclusions. The presence of extraneous volatile acids is confirmed but found not to interfere with the accuracy of the results by either method. We wish to thank the Directors of Messrs. Stafford Allen & Sons Ltd. for permission to publish this work. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. REFERENCES Staudinger H. and Harder H. Ann. Acad. Sci. Fennicae 1927 A29 No. 18 1-14. Tattersfield F. Hobson R. P. and Gjmihgham C. T. J. Agric. Sci. 1929 19 266-296. Gnadinger C. B. and Corl C. S. J. Amer. Chem. SOC. 1929 51 3054-3064. Acree F. jun. and LaForge F. B. J. Org. Chem. 1937 2 308-313. Seil H. A. Soup 1934 10 (6) 89. Wilcoxon F. Contrab. Boyce Thompson Insl. 1936 8 176-181. Holaday D. A. Ind. Eng. Chem. Anal. Ed. 1938 10 6. Anon. J . Assoc. Oficial Agr. Chem. 1945 28 72. Ripert J. Ann. Falsifications 1934 27 580-695; 1935 28 27-38. Martin J. T. J . Agric. Sci. 1938 28 458-471. - and Brightwell S. T. P. J. SOC. Chem. Ind. 1946 65 379. Gnadinger C. B. “Pyrethrum Flowers,” McLaughlin Gormley King Co. 1936 and 1946. Pantsios A. A. Ind. Eng. Chem. Anal. Ed. 1938 10 386. Graham J. J. T. and LaForge F. B. Soap 1943 19 ( l l ) 111. LaForge F. B. and Barthel W. F. J. Org. Chem. 1944 9 242; 1945 10 106 114. West T. F. J. Chem. SOC. 1946 463. Green R. G. et al. J. SOC. Chem. Ind. 1942 41 173-176. Staudinger H. and Ruzicka L. Helv. Chim. Ada 1924 7 201-211. Bray G. T. Harper S. H. Lord K. A. Major F. and Tresadern I;. H. J. SOC. Chew. Ind., Anon. Soap 1945 21 (6) 137-141. - Ibid. 1947 23 (9) 131-133. 1947 66 275-279. STAFFORD ALLEN & SONS LTD. WHARF ROAD LONDON N.l April 22nd 194

ISSN:0003-2654    

DOI:10.1039/AN9487300484

出版商:RSC    

年代:1948

数据来源: RSC

摘要:

494 The TRINDER THE ESTIMATION OF MINUTE AMOUNTS OF BORIC ACID [VOl. 73 Estimation of Minute Amounts of Boric Acid BY N. TRINDER IT is well known that many hydroxyanthraquinones and their derivatives in solution in strong sulphuric acid undergo a change in colour when added to even very dilute solutions of boric acid. This phenomenon has been utilised for both the detection and the estimation of borates. On the qualitative side the use of quinalizarin,l purpurin,2 alizarin red S2 and the unsulphonated dye base of Solway purple3 may be mentioned and for quantitative work both q~inalizarin~~~s~s~ etc. and alizarin red S g9° have been used. Most workers have restricted their investigations to quinalizarin and there is little doubt that this reagent is the best for quantitative determinations of borates if the method of estimation is by visual comparison with a series of standard colours.Neither quinalizarin nor alizarin red S, however is a suitable reagent if it is desired to assess the colour change by photo-electric measurements since only a comparatively small difference in reading is obtained between the two extremes of colour even when the most appropriate filters are used. Attempts have been made to measure the colour change photo-electrica.lly7~10~11 but Berger and. TruoglO admit that no greater accuracy is obtainable than by visual estimations. A method put forward by Dermott and Trinder,O adapted to the use of the Klett colorimeter and using alizarin red S can give with care considerable accuracy but there does appear to be a need for an accurate method for the estimation of borates by means of a photo-electric com-parison.Search has therefore been made to find more suitable dyes for photo-electric work than either quinalizarin or alizarin red S. Of several examined two have been selected for this purpose and this paper is confined to a description of preliminary work with these two reagents. The dyes used were alizarin blue S and the unsulphonated dye base of Solway purple (Colour Index No. 1073) or l-hydroxy4-~-toluidino-anthraquinone. The former when dissolved in strong sulphuric acid changes in colour from purple through brown to green in presence of boric acid whilst the corresponding change for the base of Solway purple is fro Sept. 19481 TRINDER THE ESTIMATION OF MINUTE AMOUNTS OF BORIC ACID 495 pale yellowish-green to very deep blue.As with all borate estimations involving hydroxy-anthraquinone derivatives the final concentration of sulphuric acid in the solution is most critical the optimum concentration however varying from dye to dye. The acid con-centration also determines the time taken to reach maximum colour change; generally up to a limit the higher the concentration the greater the sensitivity of the reagent and the longer the time taken to reach maximum colour change. Alizarin blue S requires a very high acidity to give the best results and is only half as sensitive as the base of Solway purple (see below). However it is quite stable in sulphuric acid solution and except for fluorides and nitrates which interfere with all boric acid estimations using alizarin dyes it is unaffected by the presence of large amounts of impurities.Perhaps a further disadvantage of alizarin blue S is the fact that when the colour change is complete the colour will not deepen much further in the presence of more boric acid. The base of Solway purple possesses two dis-advantages as a reagent for borate estimation. It sulphonates slowly to a blue compound (probably Solway purple itself) at high sulphuric acid concentrations and gives a slight colour change if comparatively large quantities of manganese are present. It has the advantage over alizarin blue S in that it is sensitive to the presence of boric acid even at comparatively low sulphuric acid concentrations. It is also at least twice as sensitive a reagent as alizarin blue S and moreover the colour of the dye changes and deepens progressively over a wide range of boric acid concentrations.Which dye is most suitable for any borate determination will be governed by the circumstances such as impurities likely to be en-countered and suspected concentration of borate but what are considered to be the optimum conditions for each dye have been worked out and the main results obtained are shown below. ALIZARIN BLUE S One ml. of 10 per cent. potassium carbonate solution was placed in each of a series of porcelain basins and boric acid solution containing nil 0.002 0.004 0.006 0.008 and 0.010 mg. of boron respectively was added. The liquid in each dish was evaporated off the dish allowed to cool and 1 ml. of 20 per cent.(bj7 volume) sulphuric acid added. The dish was rotated to dissolve all solid matter and 25 ml. of a 0.004 per cent. solution of alizarin blue S in 98 per cent. w/w sulphuric acid were added by pipette with stirring. The liquid was immediately transferred to a 40-ml. specimen tube tightly stoppered and allowed to stand for at least 18 hours. Next morning the liquid containing no boric acid was placed in a 4-cm. cell in a Spekker photo-electric absorptiometer with spot galvanometer. The drum was set at 0.600 and using Ilford violet filters (No. Sol), the iris diaphragm was adjusted to give zero deflection on the galvanometer. The remaining solutions were then substituted for the blank in turn and the drum was adjusted until there was again zero deflection on the galvanometer.TABLE I ALIZARIN BLUE S IN PRESENCE OF BORIC ACID Final sulphuric acid concentration = 96.3 per cent. w/w as boron Tube A Tube B Mean A series of standard colours was prepared as follows. The following results were obtained. Absorptiometer drum reading Boric acid present f A -I mi5 nil 0-600 0.600 0.600 0.002 0465 0.470 0.468 0.004 0-345 0.350 0.348 0.006 0.230 0.235 0.233 0.008 0.135 0.125 0-130 0.010 0.038 0.043 0.041 (0.000) (O*OOO) (0.000) (0. I 3 5) (0.130) (0.133) (0.256) (0.250) (0.253) (0.370) (0.365) (0.368) (0.465) (0.475) (0.470) (0.560) (0.555) (0.568) The above results when plotted on a graph yield a curve sloping gently. Results may be replicated with precision over a period of time provided all sulphuric acid solutions are kept in tightly stoppered bottles.It is also advisable to cover the absorptiometer cell with a piece of ground glass plate during readings. This applies particularly to the setting liquid 496 TRINDER THE ESTIMATION OF MINUTE AMOUNTS OF BORIC ACID [Vol. 73 which may otherwise be exposed to the air for some time. Readings may also be taken by the method recommended by Messrs. Hilger i.e. by setting the unknown to give zero deflection on the galvanometer with the drum set at zero and then substituting the setting solution ( i e . the solution containing no boric acid). This procedure gives the same graph as above when the results are plotted; although it is more time-consuming it has the advantage that galvanometer spot deflections are much greater.Results obtained in this way are shown in brackets in Table I. Results are not altered by the presence of 3 mg. or in some cases more of the following-potassium sodium magnesium manganese calcium zinc aluminium ferrous iron sulphite, sulphate chloride and phosphate. Ferric iron manganese dioxide and permanganates may be reduced by addition of a small crystal of sodium sulphite before the alizarin blue S reagent is added. Fluorides interfere and the quantity present should not correspond to more than 0.020 mg. of fluorine. Nitrates attack the dye and must be removed before the estimation. The above method will estimate accurately amounts of boric acid equivalent to from 0.001 to 0.010 mg. of boron per ml. For larger quantities it is necessary to dilute the unknown solution with 20 per cent.sulphuric acid before addition of the alizarin blue S reagent so that it contains preferably about 0.007 mg. of boron (present as borate) per ml. It is most important to prepare the setting liquid (i.e. that containing no boric acid) at the same time as the unknowns. To avoid frequent re-calibration of the absorptiometer it is recommended that reagents be made up as follows and kept in tightly stoppered bottles. 98 Per cent. sulphuric acid w/w-Mix equal volumes of 96 ( f 0 . 1 ) per cent. w/w sulphuric acid and 100 per cent. sulphuric acid. These acids as purchased gave a mixture sufficiently near to the required concentration. 0.1 Per cent. alizarin bZue S reagent-Dissolve 1 g. of alizarin blue S in a litre of 98 per cent. w/w sulphuric acid.This solution keeps indefinitely if stored in a dark-coloured bottle. 0.004 Per cent. alizarin bZue S reagent-Mix 80ml. of the 0.1 per cent. reagent with 1920 ml. of 98 per cent. w/w sulphuric acid. This solution also keeps indefinitely in a dark-coloured bottle. UNSULPHONATED DYE BASE OF SOLWAY PURPLE-One ml. of 10 per cent. potassium carbonate solution was placed in each of a series of porcelain basins and boric acid solution containing nil 0.001 0.002 0.003 0.004 0.005 0.0075 0.010 0.015 0.020 0.030 0.040 and 0.080 mg. of boron respectively was added. The liquid in each dish was completely evaporated off the dish was allowed to cool and 3 ml. of 20 per cent. (by volume) sulphuric acid were added. The dish was rotated until all solid matter dissolved and 25 ml.of a freshly prepared 0-075 per cent. solution of unsulphonated base of Solway purple in 84 per cent. w/w sulphuric acid were added by pipette with stirring. The liquid was immediately transferred to a 40-ml. specimen tube tightly stoppered and allowed to stand for 18 hours. Next day the first standard liquid was placed in a cell in a Spekker photo-electric absorptiometer with spot galvanometer and the iris diaphragm adjusted to give zero deflection on the galvanometer with the drum set at 0 and using Ilford yellow filters (No. 606). The solution containing no boric acid was then substituted and the drum adjusted until there was again no deflection of the galvanometer needle; the other solutions were read in the same way. Results obtained by this procedure are shown in Table 11.The results when plotted yield a series of curves all of the same form with a slight bump in one place. It was found that the reagent became slightly more zensitive with age and the results in the table were obtained with the reagent freshly prepared. Standards prepared on different days appeared to differ slightly in reading. The cause of this effect has not yet been investigated but the temperature reached on addition of the reagent would appear to be important. I t is probably advisable to cool the reagents used to prepare the colours at a constant low temperature-say 0" to 1°C.-prior to use. By this means the maximum temperature reached on mixing will be fairly constant in each test and as low as can be con-veniently obtained. Results are not altered by the presence of 3 mg.or in some cases more of the following-potassium sodium magnesium calcium zinc aluminium ferrous iron sulphate chloride and phosphate. Manganese intensifies the colour of the reagent and not more than forty times as much manganese as boron or 0.1 mg. should be present whichever is the larger. Sulphites bleach the colour given with boric acid slightly and fluorides and nitrates interfere A series of standard colours was prepared as follows Sept. 19481 TRINDER THE ESTIMATION OF MINUTE AMOCSTS OF BORIC ACID 497 in the same way as with alizarin blue S. It is most important as before to prepare the setting liquid (i.e. that containing no boric acid) at the same time as the unknowns. The above method will estimate amounts of boric acid in solution equivalent to from 04005 to 0.040mg.of boron per 3ml. and for larger quantities the test solution may be TABLE I1 UNSULPHOSATED BASE OF SOLWAY PURPLE IS PRESEXCE OF BORIC ACID Final sulphuric acid concentration = 80.1 per cent. w/w Nitrates attack the dye. Absorptiometer drum reading A Boric 7 7 acid Using 4-cm. cells Using 2-cm. cells Using I-cni. cells Using 0.5-cm. cells present & 1 as boron Tube Tube Tube Tube Tube Tube Tube Tube g. *'I B Mean A B Mean -4 B Mean A B Mean nil O*OOO 0.000 0-000 0-000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0400 0*001 0.100 0.105 0.103 0.044 0.040 0.052 0-002 0-210 0.225 0-218 0.095 0.100 0.098 0.046 0.048 0.047 0.003 0.366 0.360 0.363 0.175 0.173 0.174 0.083 0.086 0.085 0.004 0.470 0.485 0.478 0.225 0.233 0.229 0.005 0.610 0.595 0.603 0.295 0,695 0.295 0.147 0.146 0.147 0.0075 0.865 0.865 0-435 0.435 0-220 0.220 0.010 1.075 1.080 1-078 0.570 0.580 0.575 0.285 0.292 0.289 0.015 0.860 0.870 0.865 0.428 0.435 0.432 0.020 1.080 1.050 1.065 0.565 0.545 0.555 0.285 0.290 0.288 0.030 0.865 0.870 0.865 0.040 1.080 1.075 1.078 0.510 0.516 0.613 0.080 0.770 0-780 0.775 diluted suitably with 20 per cent.v/v sulphuric acid before estimation. It is not claimed that this method in its present form is as accurate as that using alizarin blue S but the range of estimation is wider and smaller quantities may be estimated. To avoid frequent re-calibration of the absorptiometer it is recommended that reagents be made up as. follows. 84 Per cent. w/w sulphuric ncid-Add 525 ml.of water cautiously to 2000 ml. of 96 ( f 0.1) per cent. w/w sulphuric acid. 0.3 Per cent. unsuljd~onated base of Solway purfde in 77.5 per cent. w/w sulphuric ncid-Add 130ml. of water to 870ml. of 84 per cent. w/w sulphuric acid and then immediately 3 g. of the dye base. 0.0075 Per cent. unsulphonated base of Solway purple in 84 per cent. w/w sulphuric acid-Add 25 ml. of the 0.3 per cent. solution of the dye base in 77-5 per cent. w/w sulphuric acid to 975 ml. of 84 per cent. w/w sulphuric acid and mix well. Prepare immediately before use in the quantity required. 20 Per cent. szrlphuric acid (by volume)-Add 200 ml. of concentrated sulphuric acid to 800 i d . of water. For the work detailed above the dye base used was obtained by desulphonation of Solway purple (Colour Index No.1073) itself by autoclaving with concentrated hydrochloric acid, the dye base being then filtered off washed with water and dried. The unsulphonated base, however is now obtainable from dye manufacturers. They must all be kept in tightly stoppered bottles. Store at 0" to 1" C. Shake. This reagent keeps indefinitely. Store a t 0" to 1" C. Store at 0" to 1" C. General methods (not described here) have been worked out for the determination of borates in plant ash and of water soluble boron in soils. REFERENCES 1. "Organic Reagents for Metals," Hopkin & Williams Ltd. 4th Edition 1943. 2. Fiegl F. and Krumholtz P. Microchemie Pregl. Festschr. 1929 77. 3. Radley J. A, ANALYST 1944 69 47-48. 4. Scharver K. and Gottschall R. 2. PjZanzenernahv. Dicngiing 1 4 . BodetLk. 1932 39 178. 5. Smith G. S. ANALYST 1935 60 735-739. 6. Berger K. C. and Truog E. Ind. Eng. Chem. .4nal. Ed. 1939 11 540. 7. Olson L. C. and De Turk E E. Soil Sci. 1940 50 257-264. 8. Dickinson D. ANALYST 1943 68 106-109. 9. Dermott W. and Trinder N. J . Agric. Sci. 1947 37 152-155. 10. Berger K. C. and Truog E. Soil Sci. 1944 57 25-36. 11. Owen E. C. ANALYST 1946 71 210-217. ELSWICK HALL NEWCASTLE-UPON-TYNE January 194

ISSN:0003-2654    

DOI:10.1039/AN9487300494

出版商:RSC    

年代:1948

数据来源: RSC

摘要:

426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents.It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate.There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international.The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively.Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited.The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation.Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE.By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time.The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction

ISSN:0003-2654    

DOI:10.1039/AN9487300498

出版商:RSC    

年代:1948

数据来源: RSC

摘要:

426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents.It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate.There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international.The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively.Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited.The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction

ISSN:0003-2654    

DOI:10.1039/AN9487300501

出版商:RSC    

年代:1948

数据来源: RSC

摘要:

426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents.It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate.There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international.The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively.Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited.The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction

ISSN:0003-2654    

DOI:10.1039/AN9487300502

出版商:RSC    

年代:1948

数据来源: RSC