V O L U M E 23, NO. 1, J A N U A R Y 1 9 5 1 (50) Smith, G. S., Nature. 163, 290 (1949). 22,969 (1950). (51) Snowden, F. C., and Page, H. T., ANAL.CHEM., (52) Stackelberg, h l . von., “Polarogrsphische Arbeitsmethoden,”
Berlin, W. de Gruyter & Co.. New York. Stechert-Hafner, 1950. (53) St,ankoviansky,S., Chem. Zoesti, 2,133 (1948). (54) Ibid., 3,266 (1949): (55) Steghart, F.L.,Cliemistry CQ: I n d u s t r u , 157 (Xarch 6, 1948). (56) Steinberg, hl., arid Sachtrieb, N. H., J . .lm. Chem. Soc., 72, 3558 (1950).
97 ( 5 7 ) Strehlow, H., and ron Stackelberg, M., 2. Elektrochem., 54, 51 (1950).
(58) Tamamushi, R.,and Tanaka, X., Repts. Radiation Chem. Re searchlnst. (Tokuo Uniu.),4, 20 (1949). (59) Taylor, J. K., Smith, R. E., and Cooter, I. L., J. Research Natl. Bureau Standards, 42, 387 (1949). (60) Tsimmergakl, V. A , , Zavodskaya Lab., 15, 1370 (1949). (61) Voyel, J., and Riha, J., .I. chirn. p h y s . , 47,5 (1950). RECEIVED October 12. 19.50.
Characterization of Organic Compounds ROBERT L. PECK Merck & Co.. Znc.,Rahuuy, S. J .
C
HA11ACTERIZATIOS of pure organic compounds niay be achieved today with rapidity and certainty. The continued introduction and development of new reactions and techniques have so extended the scope of the organic chenlist that only the most complex substances are a t present beyoiid the possibility of direct structural elucidation. The chemical and physical properties which constitute the criteria for recognition, identification, and proof of structure of organic compounds may be obtained a t the present time with relative rapidity and with relatively small quantities of sample. Developments in micro and semimicro techniques, applications of organic reactions to small scale operation, introduction of new procedures for evaluation of purity, adaptation of instrunients for small scale physical determinations, and t,lie ingenuity of analytical chemists and those engaged in characterization work are all in part responsible for the present scope of the field (98). Insight into the current trend of thinking is provided by a recent article (40)which surveys the course of analyticrtl chemistry over the past quarter of a century. During the past year or so, additional reactions, derivatives, and techniques of interest have been reported. The present review considers a number of these developments. It is noted, howewr, that methods of characterization may be found in a considerable numP,r of fields of study and as incidental observations made in connection with investigations whose major objective is not primarily the development of characterization procedures (2.i). Accordingly, this review is limited to procedures and reactions which :m considered to be representative. Many useful studies may be omitted here either because of overlooking material submerged in reports of primary interest from other points of view or because of lack of time. The material reviewd is, as before (98), taken up in three sections-namely, a section dealing with methods for deterinination of purity, one on techniques concerned with determination of physical properties, and one on procedures which concern the organic chemistry of the compounds being ch:tracterized. PURIlY
Procedures which are designed to evaluate the purity of an organic compound are generally considered to comprise an attempt a t separation and a test of identity. Chromatographic procedures fulfill these specifications, as do phase-solubility measurements and countercurrent distribution. The now well-known technique of countercurrent distribution, which has found many applications in determination of purity as well as in small scale separation work, has recently been reviewed (Sf). By means of a new all-glass apparatus of 200 tubes, the usefulness of this technique has been considerably extended (Sf). Advantages of the new apparatus include better visibility of solutions, greater ease of removal of sample from a
single tube for examination a t any position in tlw systr’rn, and greater versatility as regards solvent systems. The “solubility temperature” has been suggested as a criterion for characterization of pure compounds as well as of niixtures (104). This is similar to determination of consolute tcmperature, and is considered to be a convenient property to dvtermine, if sufficient quantities of material are available. Enip1o)-nient of the “critical mixing temperature” for rccognition and determination of sniall amounts of organic liquids has been descrihed (46). Fractional sublimation of organic compounds on removable transparent films (66) presents an attractive, small scale procedure for determination of purity of minute amounts of sublimable substances. The procedure permits uninterrupted sublimation and separation of several components in one operation. Removal of the sublimate by pceling off the strip facilitates ready separation of the several fractions for qualitative examination. Ion exchange resins show pronlise of far greater application in purity determination (ff6) as well as in separations related thereto (22, 61). The characterization of ribonucleotides by means of a rrsin is an elegant procedure providing separation arid identity data (26). It has been remarked that before long exchange resins will be used for srparation of most compounds of acidic or basic nature, leaving only the relatively neutral compounds as suhject for srparation by the orthodox adsorption chomatography . Charcoal chromatography has provided a useful evaluation of purity of sugars by means of a modification of the Tiselius technique (126). S e w streak reagents for location of zones of colorless substances in extruded chromatographic columns have been developed (80). Paper chromatography continues to receive much attention. hlentioii niay be made of procedures for separation and identification of mixtures of keto acids (88),of flavanol-3-glycosides (50), nucleic acids (80,lf4),purines, pyrimidines, and derivatives (81, 64), fats and fat-soluble pigments (SY), phosphoric esters (60), aromatic aldehydes and lignin degradation products ( I S ) , various phenolic compounds ( 4 2 ) , and miscellaneous antibiotics (100). Many of these methods include procedures for quantitative determination of the substances of interest. The last-mentioned procedure provides a very useful method for rapid recognition of previously known antibiotics, especially when combined with observations on physical properties and chemical reaction behavior on a micro scale. Its application to screening work is obvious. Similar applications for groups of compounds other than antibiotics are becoming apparent. A recently reported simple device for handling large numbers of two-dimensional paper chromatograms (32) would appear to solve one problem confronting investigators in this field. Photometric procedures for quantitative determinations of zones have been studied further (107). Further applications of radioactive tracers, development of a radioactivity
ANALYTICAL CHEMISTRY
98 scanning device (15), and other visualizing procedures (1, 64, 92) have further extended the quantitative aspects of paper chromatography. Development of the “chromatobar” and the “chromatostrip” provides two tools for separations of small amounts of mixtures and identification of substances (92). A similar development using silica gel on glass has been described (91). -4very useful application of the technique of paper chromatography to determination of purity of antibiotics may be illustrated in the separation of a supposedly pure polymixin B into two separate active entities. Ordinary methods of purification had given a supposedly pure substance, which when examined by strip chromatography showed t n o different antibiotically active zones (106). In the case of neomycin B, paper chromatographic examination indicated that it M iis a single antibiotic substance (105).
The application of paper chromatography for comparison of an aminohydroxy degradation fragment of low molecular weight from vitamin Bl2 with synthetic reference compounds led to the conclusion that the substance had the same RP value as synthetic 2-amino-1-propanol (29, 38). Unequivocal evidence of classical organic type subsequently established the identity of the compound in question as 1-amino-2-propanol (128). The paper chromatographic evidence thus established in this instance that using four different solvent systems the degradation product migrated at the same rate as that of the isomc~r~r compound, P-amino-lpropanol. PHYSICAL MEASUREMENTS
The general trend toward adapting the requirements for sample to smaller and smaller amounts for the x-ray diffraction, infrared absorption, and ultraviolet absorption measurements] and the adaptation of the corresponding instruments for such work steadily increase the scope of application of these techniques in characterization work. Modification of isotope dilution proced u e s (25) and adaptation to infrared analyses (119) have greatly extended possibilities for identification of organic compounds capable of atom exchanges. Polarographic studies on various types of organic compounds (53, 124) have extended the scope of this technique for characterization work. Raman spectra are being studied to an increasing estent (25). It should soon be possible to extend the use of such spectra to the convenient characterization of many additional liquid organic compounds. A new modification of an older melting point apparatus has been suggested for rapid microdetermination of melting point (73). -4 modification of the Barger (10) microdetermination of molecular weight has recently been suggested, which includes use of “opposed twin” capillary tubes (96)to avoid danger of mixing solutions and to shorten to allout 48 hours the time required. An improvement in the Rast niethod (102) eniplovs polarized light in evaluation of the melting temperature (29). Polarized infrared spectra have been employed (5, 59) in the study of structure and arrangement of proteins with regard to orientation of groupings and arrangement of the molecules. The extension of studies on the use of infrared spectrometry in elucidation of steroid structure has yielded data on the detection and location of ethylenic double bonds in steroids (69). Recent investigations on relationships of structure and rotatory power of dipeptides (W), structure and melting points of branched-chain fatty acids (23), and related studies (56) have been reported. The development of stereochemical formulas for hydroxypyroline, allohydroxyproline enantiomorphs, and related structures (66), and calculations on the number of positional isomers in aromatic systems (43) also further the understanding of relationships between structure and physical properties. Microwave spectroscopy presents interesting possibilities for Characterization of minute amounts of gaseous sample ( M ) ,but is limited to gas-phase operation and to compounds possessing polar
groups. I t is far more sensitive than the infrared for the resolution of bands. Mass spectrometry has been brought closer to easy access for application to organic characterization work (25). Of possible application in the near future for elementary analysis of highly specific qualitative nature is the determination of the nuclear magnetic resonance. This has the advantage of being capable of application to aqueous and solvent solutions from which the material can be recovered. Paramagnetic resonance absorption could be employed in characterization work, since the properties measured are fairly specific for the compounds used. This type of measurement would be useful for studies of nature of transition group elements present in complex organic compounds. Another application of physical nature which may become useful in this regard is the phosphorescence of solid solutions a t extremely low temperatures. Extension of x-ray analysis of electron density of molecules (119) promises increasing application in organic structure analysis. A new tabulation of physicochenlical data on pure organic compounds has recently appeared (118). CHEMICAL PROCEDURES
The analytical characterizatioii of organic compounds by quantitative determination of functional groups has received eonsiderable attention recently (112; cf. 39 for symposium references). Functional group analysis may be considered to comprise the identification and quantitative determination of any structural moiety of an organic compound by methods other than direct analysis (126). Consideration of requirements for new procedures (111)] applications of electrical measurements (86), and specific applications to cellulose derivatives (54) have been reviewed extensively. Group analyses have contributed much to the elucidation of structures of organic compounds in the past; the developments indicated above reflect increaeed appreciation of the value of information of t,his type in general characterizat,ion work. Attention has been drawri again to difficulties frequent,ly encountered in detecting the presence of sulfur in complex organic compounds ( 4 ) ,reference being made to the discovery of sulfur i n penicillin. Whenever possible, quantitative sulfur det,ermination is the surest method of establishing the presence of sulfur. Several modifications in micromethods for sulfur determination have been reported recently ( 2 , 3 , 4 l ,7 2 ) . A recent publication discusses quantitativewltramicroanalytical procedures in detail (71). Mention is made of additional descriptions of nlicrogram procedures (11)and semimicromethods for preparative organic chenlistry (81). Developments in technique for micromanipulation generally continue to appear as a result of the ingenuity of chemists who face the difficult task of rapid characterization of small amounts of complex natural products. &4lthough the classical application of derivatives of organic compounds is in final establishment of identity by comparison with authentic reference samples, derivatives may also be employed because of their ease of crystallization to a pure state for analytical purposes, possibilities of regeneration of purified product to some other desired forms, ability to provide protection of labile groups, or utility in labeling of moieties during degradative reactions, or because they inay effect general improvements in physical properties. Several derivative types of interest are considered] but the subject is not covered exhaustively. The use of amine bisulfites as reagents for formation of aldehyde and ketone derivatives has been reported ( 2 ) . By employing optically active reagents, the derivatives may be used for resolution of optically active isomers, rlnother reagent, &(,-phenylethyl)-semioxamazide, has also found application in forming carbonyl derivatives and may be used for resolution purposes (79), as shown by separation of the isomers of 3-methylcyclohexanone. The Girard reagents (57) for separation of ketonic substances from mixtures continue to find useful application. Allyl chloroformate, a stable and commercially available
V O L U M E 23, NO. 1, J A N U A R Y 1951 reagent, forms allyl derivatives of amino acids and similar amino compounds which crystallize about as readily as the corresponding carbobenzoxy derivatives (116). Regeneration by hydrogenolysis or by use of sodium in liquid ammonia may be readily effected. Among the amino acid derivatives which have been found useful for crystallographic identification are those prepared with 2-nitroindan-lJ3-dione (7’6)and 5-nitrobarbituric acid (75). The conversion of certain unsaturated acids and esters and hydroxyesters to well crystalline N-benzoylamino acids by reaction with benzonitrile would appear to be applicable to a small scale and may find application in characterization of such compounds (61). This reaction provides a route to reference samples of certain compound types. The formation of A‘-cyanoethyl derivatives of amino acids by reaction with acrylonitrile in alkaline medium to give crystalline products also appears applicable to a small scale (87). A reagent of special interest for derivative formation with amino acids is the N,N‘-dicarboxy dianhydride of cystine (8), which has been used for the preparation of peptides, and may find another application in forming X-cystinyl derivatives of amino compounds for water-solubilization purposes, as well as for characterization. Application of a-isocyanate aliphatic esters for vondensation with S-carbobenzoxy amino acids for peptide Eynthesis is of interest (58). Introduction of glycyl residues through condensation of amino acid or peptide esters with 2thio-5-thiazolidine (27)and of alanyl residues by means of 2-thio-4methyl-5-thiazolidine (28) x-ould appear to be useful for derivative formation. Phthalylglycyl dibenzyl phosphate, a “high energy” phosphate, reacts with glycine and with other amino acids to form peptides under mild conditions (110). This is useful both for derivative preparation in the peptide field and for peptide synthesis. The availability for organic work of reagents such as methanol coiitaining isotopic carbon (SO), carboxyl-labeled methyl bromoacetate and phenyl acetate containing isotopic methyl ( 2 2 1 ) , C14-lal)eledmethyl bromide obtained via nitrogen mustards (do), hydrogen sulfide with radioactive sulfur (74), and other labeled reagents in rapidly increasing numbers has made possible many organic rcactions which may be investigated with more clarity of interpret,ation than has ever before been possible. IIention inay be made of fluorcscent derivatives which may be prepared by means of acyl chlorides and hydrazides of coumarin carboxylic acids (9). These derivatives are of special interest in separations and identifications based on paper chromatography. Employment of 1 1 3 1 - and S3j-containing p-iodobenzene sulfonyl derivativtls of amino acids for specific separations in paper cshroniatography ( T O ) , studies on Il3*-labeled monoiodotyrosine, diiodotyrosine, and thyroxine (78), and the use of Cu6‘ in a rc1:igeut for microestimation of amino acids on strips (1%)illustrate applications in paper chromatography. The reaction of 8-alkoxyacrylic esters with secondary amines pi,ovides another means of preparing derivatives of such compounds (34). The preparation of guanido derivatives of aromatic amines by a modified method gives access to an easy procedure for prc’paring these substances in good yield ( 7 7 ) . The nitroalkanes, no\\- available in quantity and variety, provide useful derivativeforming reagents for carbonyl compounds (62). The useful application of these reagents to “up-series” synthetic reactions needs no more than mention here. Ethanolamine has been shown to be r,xtreniely useful for derivative formation in the identification of e s t m of monobasic acids (103). In recent years the investigation of organic degradation reactions has been prosecuted with great vigor and notable success. Efforts t o find new and improved reagents, reactions, and techniques made in connection with specific structural problems continue to result in an increase of our knowledge of organic compounds and to provide a better basis for full characterization of unknown compounds. Of considerable interest have been improvements in analytical
99 procedures for carbonyl compounds. Methods for determination of carbonyl compounds in the presence of organic acids (113) and of aldehydes in the presence of ketones (93) have been reported. A new term, the “hydroxylamine number” (120),has been int,roduced. The procedure described, while not exactly new (20), appears to be useful in obtaining the equivalent weights of carbonyl compounds. This information, combined with the niolecular weight data, has direct application to structural elucidation work. A quantitative micro application of the hydroxylamine titration has been described (83). A short, convenient method for the quantitative determination of aromatic nitro groups with tin (122) has been reported. A colorimetric determination of certain ortho-substituted phenols in the presence of their para isomers has been described (117). An interesting reaction involving the rearrangement of a steroidal ketone, 17,21,21-tribromopregnan-3(p)ol-20-oneacetate, to give an a-bromo, a,&-unsaturated acid, 2O-bromo-17-pregnene-3(j3)01-21-bis acid, upon treatment with a solution of potassium hydroxide in aqueous ethyl alcohol was found to be a genera! reaction of a,a,a-tribromo ketones (123). Experiments with diazomethane and diazoethane have shown that these reagents react with mono oximes of phenanthraquinone, retenequinone, and chrysenequinone to form oxazole derivatives (108). Lithium aluminum hydride, one of the newer reagents used in organic chemistry, has been investigated rather extensively. This substance is recognized as a powerful reducing agent for many types of organic compounds (86) including alcohols, glycols, phenols, carboxylic acids, primary and secondary amines, aldehydes, ketones, esters, anhydrides, acid chlorides, amides, nitriles, and aromatic nitro compounds (84). It has been shown (6) that lithium aluminum hydride in an ether-type solvent is an effective reducing agent for the disulfide linkage in organic molecules. Measurement of the stoichiomr.trically released hydrogen in lithium aluminum hydride reductions provides a bavis for a possible quantitative mPt,hod for determination of disulfides. The reduct,ion involves scission of thc sulfur-sulfur bond to form a lithium aluminuni complex, hydrolysis of which with dilute acid yields mercaptans (thiols). On thc other hand, i t has been shown (63)that aromatic disulfides as well as mercaptals and mercaptols are transferred into simple thio ethers by the action of Raney nickel that has been freed from hydrogen by heating in vacuo a t about 201” C. h quantitative micro application of the lithium aluminum hydride reaction for group analysis of various active hydrogen-containing compounds has been reported (82). .Ipplication of lithium alunlinum hydride to determination of twminal carboxyl groups of proteins by conversion to primary a-amino alcohol residues appears to be of interest (48). In structural elucidation work cleavage reactions continue to play an important role. In studies of the ring cleavage, dehydration, and epimerization of some steroids and related compounds by palladium catalyst (?), it iyas show1 that the action of 5% palladium on charcoal has differcrit effects, depending upon tlie compound used and on the temperature employed. Iting cleavage of a-allylbenzylaiiiiries using formaldehyde and formic acid has been reported (65): allylb benzyl amine yielding 1dimethyl-3-aminobutene and benzaldehyde. Periodate oxidation was found useful in determining the ririg structure of the sugar component of several naturally occurring synthetic pyrimidine nucleosides (:)4). Perbenzoic acid employed for the oxidation of 20-keto steroids effected the reaction without inversion a t the C-17 position (62). Use of o-carboxyperbenzoic acid for preparation of S-oxide derivatives is described (89). A review of experimental proofs of hyperconjugation has recently appeared (101). A new method for determining terminal amino acid residues in polypeptides and proteins (47) involves the reductive condensation with aliphatic aldehydes (17 ) . The polypeptide undergoes alkylation only on the terminal amino group, and hydrolysis of the
ANALYTICAL CHEMISTRY
100 alkylated peptide followed by isolation of the resulting alkylamino acid readily identifies the “end amino acid.” .4 study of the alkylation of amino acids by reductive condensation with higher aliphatic aldehydes (16) has shown that straight-chain amino acids furnish the corresponding N,N-dialkyl amino acids,but certain branched-chain and A’-substituted amino acids undergo monoalkylation owing to steric hindrance. Aliphatic and aromatic amino acids can therefore be reduced and S-methylated in one operation by reductive condensation with formaldehyde and hydrogen in the presence of palladized charcoal (18). An interesting reaction which may provide new tools for protein structure elucidation is the selective splitting out of aspartic acid from many proteins by means of oxalic acid (97). Stepwise degradation of peptides by means of cleavage at room temperature of the phenylthioureido derivatives in an anhydrous medium (37) and of the phenylcarbamyl derivatives (96)provides reactions of value in the characterization of peptides (49). A selective analytical micromethod for use with the phenylthiocarbamyl peptides is described (36). A reinvestigation of quantitative determination of amino acids (109) has shown that the iodometric titration of the copper salts, using washed copper phosphate for salt formation, yields increased accuracy and facility. I t has been suggested (35)that the use of random presulfonated 1-naphthol offers a more satisfactory general carbohydrate test than the conventional Molisch reaction. This new test not only can be used as an aid in identifying carbohydrate groups, but offers a simple, rapid procedure for estimating small amounts of carbohydrates. An added advantage lies in the fact that a solution of random sulfonated 1-naphthol does not darken on standing and is made up in water solution which is not possible for 1naphthol itself. Mention should also be made of the sensitive microtest for carbohydrates which employs diiinisidine acetate
(44). A general discussion of the methods of pyrolysis has been reported (14) which provides information on ring opening, ring closure, and ring enlargement and decrease. The application of pyrolytic reactions to acyl derivatives of aminophenols (51) and to acyl derivatives of streptamine (99)to give substituted benzoxaeoles provides an illustration of the utility of selected pyrolytic reactions for structural work. A procedure employing absolute sulfuric acid solutions a t low temperature has been devised for simultaneous desulfurization and acetylation of carbohydrate acid sulfates (ROS020H) in which the reaction takes place without Walden inversion. However, some glycosides may be hydrolyzed (129). The cleavage of ethers with iodide in 95% phosphoric acid a t reflux temperature provides both a degradative reaction and a method for preparing organic iodides (117). The results of microbiological assays have been made more significant by a reported method (68) for a rapid microestimation of nonvolatile organic matter. Knowledge of the amount of organic matter in a sample sent for assay offers interpretation of the results in units per milligram of organic matter rather than simply in units per milligram of dry matter. ACKNOWLEDGMENT
The author deeply appreciates the help of John E. Lyons and Paul H. Gale in the preparation of this manuscript. LITERATURE CITED
(1) Acker, R., Fromageot, C., and Jutisz, M., Biochem. et Biophys.
Acta, 5, 81 (1950). (2) ddams, R., and Garber, J. D., J . Am. Chem SOC.,71, 522
(1949). (3) Alicino, J. F., ANAL.CHEM.,20, 85 (1948). (4) Alicino, J. F., Arch. Biochem., 27, 221 (1950). (5) Ambrose, E. J., Elliot, A., and Temple, R. B., Xature, 163, 859 (1949). ( 6 ) hrnold, R. C., Lien, A. P., and .Urn, R. M . , J . Bn. Chem. SOC.,72, 731 (1950).
(7) Bachmann, W. E., and Dreiding, A. S.,Ibid., 72, 1323 (1950). (8) Bailey, J. L., Xature, 164, 889 (1949). (9) Baker, mi., Harsar, C. N., and hlcOmie, J. F. W., J . Chem. SOC.,1950, 170. (10) Barger, G., J. Chem. SOC.,Proc., 19, 121 (1903). (11) Benedetti-Pichler, A. A., Mikrochemie, 34, 39 (1948-49). (12) Blackburn, S., and Robson, A., Chemistry and Industry, 1950, 614. (13) Bland, D. E., Nature, 164, 1093 (1949). (14) Blatt, A. H., J . Org. Chem., 15, 869 (1950). (15) Boursnell, J. C., Nature, 165, 399 (1950). (16) Bowman, R. E., J . Chem. Soc., 1950, 1346-9. (17) Ibid., pp. 1349-51. (18) Bowman, R. E., and Stroud, H. H., I M . , 1950, 1342-5. (19) Brandstatter, M., and Kofler, L., Mikrochemie, 34,364 (1948-49). (20) Bryant, W.M. D., and Smith, D. M.. J . Am. Chem. Soc., 87, 57 (1935). (21) Carter, C. E., Ibid., 72, 1466 (1950). (22) Caaon, J., Sumrell, G., and Mitchell, R. S., J . Ore. Chem., 15, 850 (1950). (23) Cason. J.. and Winans. TT. R.. Ibid.. 15. 139. 148 (1950). i24j Clarke, B’. L., I d . EnQ. Chem.’,23, i30i (1931); J.~Ch&. Education, 14, 563 (1937). (25) Coggeshall, K. D., AKAL.CHEM.,22, 351 (1950). (26) Cohn, W.E., J . Am. Chem. SOC.,72, 1471 (1950). (27) Cook, A. H.. and L e w , A. L.. J . Chem. SOC.,1950, 646. (28) Ibid.,p. 651. (29) Cooley, G., Ellis, E., and Petrow, V., J . Pharm. PharmacoZ.. 2, 128 (1950). (30) Cox, J. D., and Warm, R. J., Nature, 165, 563 (1950). (31) Craig, L. C., and Post, O., ANAL.CHEM.,21, 500 (1949); J. Clin. Invest., 28, 1014 (1949). (32) Datta, S. P., Dent, C. E., and Harris, H., Biochem. J., 46, xlii (1950). (33) Datta, S. P., Overell, B. G., and Stack-Donne, M., NatuFe, 164., 673 11849). (34) deBenneville, P. L., and blacartney, J. H., J . Am. Chem. Soc., 72, 3725 (1950). (35) Devor. A. W.. Ibid.. 72, 2008 (1950). (36) Edman, P., Acta Chem. Scand., 4, 283 (1950). (37) Edman, P., Arch. Biochem., 22, 475 (1949). (38) Ellis, B., Petrow, V., and Snook, G. F., J . Pharm. Pharmacol., 1, 60, 950 (1949). (39) Elving, P. J., AN.AL.CHEY.,22, 376 (1950). (40) Ibid., p. 411. (41) Erdos, J., Mikrochemie, 34, 286 (1949). (42) Evans, R. 9.,Parr, W.H., and Evans, W.C., Nature, 164, 674 (1949). (43) Evans, R. F., and LeQuesne, W. J., J . Org. Chem., 15, 19 (1950). (44) Feigl, F., “Qualitative Analysis by Spot Tests,” p. 343, New York, Nordemann Publishing Co., 1939. (45) Fischer, R., and Neupauer, E., Mikrochemie, 34, 319 (194849). (46) Foreman, W. W., Murray, A,, and Ronzio, A. R., J. Org. Chem., 15, 119 (1950). (47) Fox, S.W., Advances in Protein Chem., 2, 155 (1945). (48) Fromageot, C., Jutiss, M., Meyer, D., and PQnasse, L., Compt. rend., 230, 1905 (1950). (49) Fruton, J. S.,Advances in Protein Chem., 5 , 1 (1949). (50) Gage, T. B., and Wender, S.H., ANAL.CHEM.,22, 708 (1950). (51) Galatis, L. C., J . Org. Chem., 15, 333 (1950). (52) Gallagher, T. F., and Kritchevsky, T. H., J . Am. Chem. Soc., 72, 882 (1950). (53) Geissman, T. A., and Friess, S.L., Ibid., 71, 3893 (1949). (54) Genung, L. B., ANAL.CHEM.,22,401 (1950). (55) Gettler, A. O., Umberger, C. J., and Goldbaum, L., Ibid., 22, 600 (1950). (56) Gilmore, E. H., Menaul, M.,and Schneider, J., Ibtil., 22, 892 (1950). (57) Girard, A,, and Sandulesco, G., Hela. Chim. Acta, 19, 1095 (1936). (58) Goldschmidt, S., and Wick. M., 2. Naturforsch., 5b, 170 (1950). (59) Goldstein, XI., and Halford, R. S., J . Am. Chem. SOC.,71, 3854 (1949). (60) Hanes, C. S.,and Isherwood, F. A , , Nature, 164, 1107 (1949). (61) Hartael, L. W.,and Ritter, J. J., J . Am. Chem. Soc., 71, 4130 (1949). (62) Hass, H. B., Susie, A. G., and Heider, R. L., J . Org. Chem., 15, 8 (1950). (63) Hauptmann, H., and Madsilaw, B., J . Am. Chem. SOC.,72,707 (1950). (64)Holiday, E. R., and Johnson, E. A., Nature, 163, 216 (1949). (65) Horowits, R. M., and Geissman, T. A., J . Am. Chem. Soc., 72, 1518 (1950). (66) Hudson, C. S., and Neuberger, A,, J. Org. Chena., 15, 24 (1950). (67) Idler, D. R., J . Am. C h m . SOC.,71, 3854 (1949). (68) Johnson, bl. J., J. B i d . Chem., 181, 707 (1949). ~
\ - - -
I
V O L U M E 23, NO. 1, J A N U A R Y 1 9 5 1
101
Jones, R. N., Humphries, P., Packard, E., and Dobriner, K., J . Am. Chem. Soc., 72, 86 (1950). Keston, A. S., Udenfriend, S., and Levy, M., Ibid., 72, 748 (1950). Kirk, P. L., “Quantitative Ultramicroanalysis,” New York, John Wiley & Sons, 1950. Kirsten, W., Mikrochemie, 35, 174 (1950). Kofler, L., and Kofler, W., Ibid., 34, 374 (194849). Koski, W. S., Nature, 165, 565 (1950). Larsen, J., Poe, C. F., and Witt, N. F., Mikrochemie, 34, 351 (1948-49). Larsen, J., Witt, N. F., and Poe, C. F., Ibid., 34, 1 (1949). Latham, H. G., May, E. L., and Mosettig, E., J . Org. Chem., 15, 884 (1950). Lemmon, R. M., Tarpey, W., and Scott, K. G., J . Am. Chem. SOC.,72, 758 (1950). Leonard, N. J., and Boyer, J. H., J . Org. Chem., 15, 42 (1950). LeRosen, A. L., Monaghan, P. H., Rivet, C. A., Smith, E. D., and Suter, H. A., ANAL.CHEM.,22, 809 (1950). Lieb, H., and Schoniger, R.,Mikrochemie, 34, 336 (194849). Ibid., 35, 400 (1950). Ibid., p. 407. Lintner, C. J., Schleif, R. H., and Higuchi, T., BNAL.THEM., 22, 534 (1950). Lintner, C. J., Zuck, D. A., and Higuchi, T., J . Am. P h n r m . dssoc., Sci. Ed., 39, 418 (1950). Lykken, L., - 4 ~ 4CHEM., ~. 22, 397 (1950). RIcKinney, L. L., Uhing, E. H., Setzkorn, E. A., and Cowan, J. C., J . Am. Chem. Soc., 72, 2599 (1950). Magosonik, B., and Umbarger, H. E., Ibid., 72, 2308 (1950). Mamalis, P., and Petrow, V., J . Chem. Soc., 1950, 703. Markam, R., and Smith, J. D., Biochem. J . , 46, 513 (1950). Marvel, C. S., and Rands, R. D., Jr., J . Am. Chem. Soc., 72, 2642 (1950). Miller, J. M., and Kirchner, J. G., Abstracts of Papers, 118th Meeting, AM. CHEM.SOC., Chicago, Ill., p. 10B, Sept. 3-8. 1950. Mitchel, J., Jr., and Smith, D. M., - 4 ~ ~ 1CHEM., .. 22, 746 (1950). Newmark, M. Z., Goodman, I., and Dittmer, K., J . Am. Chem. Soc., 71, 3847 (1949). Kiederl, J. B., Kasanof, D. R., Kisch, G. K., and Rao, D. S., Mikrochemie, 34, 132 (1949). Syman, A I . A., and Herbst, R. M., J . Org. Chem., 15, 108 (1950). Partridge, S. M., and Davis, H. F., .Tuture, 165, 62 (1950). Peck, R. L., ANAL.CHEM.,22, 121 (1950). Peck, R. L., Hoffhine, C. E., Jr., Peel, E. W.,Graber, R. P., Holly, F. W., Moningo, R., and Folkers, K., J . Am. Chem. Snc., 68, 776 (1946).
Peterson, D. H., and Reineke, L. M.,Ibid., 72, 3598 (1950). Polangi, M., J . Chem. Phys., 46, 235 (1949). Rast, K., Ber., 55, 1051, 3727 (1922). Rauscher, W. H., and MacPeek, D. L., ANAL.CHEM.,22, 923 (1950). Reeve, W., and Adams, R., Ibid., 22, 755 (1950). Regna, P. P., and Murphy, F. X., J . Am. Chem. SOC.,72, 1045 (1950). Regna, P. R., Solomons, I. A., Forscher, B. K., and Timrech, A. E., J . Clin. Invest., 28, 1022 (1949). Rockland, L. B., and Dunn, M. S., J . Am. Chem. SOC.,71, 4121 (1949). Schonberg, A., and Awad, W. I., J . Chem. Soc., 1950, 72. Schroeder, W. A,, Kay, L. M.. and Mills, R. S.,ANAL.CHEM., 22, 760 (1950). Sheehan, J. C., and Frank, V. S., J . Am. Chem. Soc., 72, 1312 (1950). Siggia, S., ANAL.CHEM.,22, 378 (1950). Siggia, S., “Quantitative Organic Snalysis via Functional Groups,” New York, John Wiley & Sons, 1949. Smith, D. M., and Mitchell, J., Jr., ANAL.CHEM.,22, 750 (1950). Smith, J. D., and Markham, R., Biochem. J., 46, 509 (1950). Stein, W. H., and Moore, S., Abstracts of Papers, 118th Meeting, AM. CHBM.SOC., Chicago, Ill., p. 10M, Sept. 3-8, 1950. Stevens, C. M., and Watanabe, R., J . Am. Chem. SOC.,72, 725 (1950). Stone, H., and Shechter, H., J . Org. Chem., 15, 491 (1950). Timmermans, J., “Physico-Chemical Constants of Pure Organic Compounds,” New York, Elsevier Publishing Go., 1950. Trenner, N. R., A N ~ LCHEM., . 22, 405 (1950). Troaaolo, A. M., and Lieber, E., Ibid., 22, 764 (1950). Turner, R. B., J . Am. Chem. Soc., 72, 579 (1950). . 22, 572 Vanderzee, C. E., and Edgell, U’.F., A N ~ LCHEM., (1950). Wagner, R. B., and Moore, J. ri., J. Am. Chem. soc., 72, 3655 (1950). Wawzonek, S.,ANAL.CHEM.,22, 30 (1950). Webb, T. J., Ibid., 20,96 (1948). Whistler, R. L., and Durso, D. F., J . Am. Chem. SOC.,72, 677 (1950). Fillard, H. H., and Wooten, -4.L., ANAL. CHEM.,22, 423 f195O). Wolf, D. E., Jones, W. H., Valiant, J., and Folkers, K., J . Am. Chem. Soc., 72, 2820 (1950). Wolfrom, M. L., and Montgomery, R., Ibid., 72, 2859 (1950).
.----.
RECEIVEDOctober 31, 1950.
[End of Review Section]
Automatic Operations in Analytical Chemistry GORDON D . PATTERSON, JR., WITHM. G . MELLON
Purdue University, Lafayette, Znd.
T
HE automatization of analytical chemistry described a year ago (559) appears still to he accelerating with the climax not yet in sight. The volume of literature describing new iaboratory and industrial developments and applications is so voluminous as to challenge seriously the ability of any one person to keep abreast of this rapidly moving phase of quantitative analysis. The period covered in this review is essentially confined to the past two years, inasmuch as the literature search for the previous r,evien- was terminated late in 1948. Again emphasis is laid on the fact that the very desirable end of completely eliminating the human factor in the gathering of quantitative measurements is rarely attained. The analogy between the breakdown of chemical engineering processes into unit operations and a similar classification of analytical methods is continued. The desirability of measuring physical properties automatically has been evident t o man ever since the science of measurement first began. This is partly a result of man’s innate interest in the novel and unique. This was the case, no doubt, with Pharaoh Ptolemy’s fascination in Hero’s Automaton dating from 200
which was one of the mechanical marvels of ancient times (61). Far from a simple whim, however, is the chemist’s present interest. The necessity of obtaining extensive amounts of data accurately and economically has forced the adoption of instruments which will perform the required operations with a minimum of human effort. The role of physical properties becomes even more obvious in a study of automatic operations in quantitative analysis. Numerous authors have emphasized the increasingly close interdependence of physical properties and modern analytical chemistry (22, 146, 336, 403). A number of books have been published recently on physical methods and instrumentation (28, 34, 140, 464,4?2). I n fact, a scientific instrument has been defined as any Bystem which gives numerical approximations of the true magnitude of some physical property. The commercial literature available from American instrument manufacturers is frequently a good source of fundamental information (329). A number of firms regularly publish news-style periodicals which are available free. B.c.,
