(12) Flikkema, D. S., Schablaske, R. V., U. S.Atomic Energy Comm., “X-Ray Spectrometric hlethod for Determination of Plutonium in Solution” ANL5804 (November 1957). (13) Forbes, S. G., U. S. Atomic Energy Comm., Idaho Operations Office, “A Non-Destructive Method for Fuel A s saying,” IDO-16114 (1953). (14) Furby, E., Atomic Energy Research Estab. (G. Brit), “Determination of Uranium and Thorium in Uranium/ Thorium Alloys,” AERE-C/R-1435 (1954). (15) Highfill, J. P,., New Brunswick Laboratory, unpublished work. (16) Kallmann, S., Ledoux and Co., private communication. (17) Kramer, H., Lerner, hl. W., New Brunswick Laboratory, unpublished work. (18) Larsen, R. P., ANAL. CHEM. 31, 545-9 ( 1959). (19) Larsen, R. P., Shor, R. S., Feder, H. M., Flikkema, D. S., U. S. Atomic Energy Comm., “Study of the Explosive Properties of Uranium-Zirconium Alloys,” ANL-5135 (July 1954). (20) Marley, J. L., Kiley, C. J., U. S. Atomic Energy Comm., “Determination of Uranium in Stainless Steel. Electrolytic - Volumetric,” KAF’L -MJLM-1 (October 1956).
(21) Metz, C. F., ANAL. CHEM. 29, 1748-56 (1957). (22) Milner, G. W. C., Atomic Energy ReseaPch Estab. (G. Brit.), “Analysis of Uranium-Niobium Alloys,” AEREC/R-852 (Januarv 1952). (23)’ Milner; G. c.,. Sarnett, G. A., Anal. Chem. Acta 17, 220 (1057). (24) Milner, G. W. C., Phennah, P. J., Atomic Energy Research Estab. ( G : Brit.), “Analysis of Uranium-Titanium Alloys,” AERE-C/R-1236 (1953). (25) hIilner. G. W. C.. SkewieB. A. F.. ’ Atomic Energy Research Esxab; (G: Brit.), “Analysis of Uranium-Zirconium Alloys,” AEREC/R-1126 (1953). (26) Moak, W. D., Pojasek, W. J., U. S. Atomic Energy Comm., “Determination of Uranium in UO?AlIOq - - ” Fuel Elements ,by X-ray Emission Spectrography, KAPL-1879 (1957). (27) “Modern Approaches to Isotopic Analysis of IJranium,” Conference, Chicago, Ill., Feb. 5-7, 1957, U. S. Atomic Energy Comm., TID-7531, Pts. 1 and 2 (October 1057). (28) Kv’uclear Power 4, 113-20 (1959). (29) Phillips, G., Analyst 83, 75-9 (1958). (30) Rodden, C. J., “Analytical Chemistry of the Manhattan Project,” hlcGrawHill, New York, 1950. (31) Rodden, C. J., U. S. Atomic Energy Comm. , “Current Procedures for the
Analysis of UO,, UF,, and UF,,” TID7003 (Del) (February 1956).
(32) Rodden, C. J., Lerner, M. W., “The hletal Thorium.” DD. 352-70. American Society for Metals,ACleveland; Ohio, 1058. (33) Rodden, C. J., Vinci, F. A., “The hletal Beryllium,” pp. 641-91, American Society for Metals, Cleveland, Ohio. (34) Rynasiewicz, J., Sleeper, M.,Consalvo, V., U. S.htomic Energy Comm., “Analysis of Sintered hlixed Oxides of Uranium and Beryllium,” KAPL421 (October 1950). (35) Scribner, B. F., hlullin, H. R., J. Research 1Vatl. Bur. Standards 37, 379-89 (1946). (36) Smiley, W. G., ANAL. CHEM.27, 1098 f 10.55). --, (37) Susano, C. D., hlenis, O., Talbott, C. K., Zbid., 28, 1072 (1956). (38) Swinehart, B. A., Graves, J. W., “Mallinckrodt Chemical Works-Uranium Division, AEE Research and Development Report, MCW-1419, X177-185 (October 1958). (39) Vogs, F. S., Greene,-e been proposed for thc determination of phosphorus. but only those based on its precipitation as :iniiiioniuni phosphomolybdate have found, until recently, important application in fertilizer analysis. Furthermore. phosphomolybdate complexes of one kind or another are the keystone of newer methods that arc winning considerable use. The gravimetric proccdure, involving separation of the phosphorus as aninioniuni phosphomolybdate antl 11 eighing as magnesium pyrophosphate. has long been the umpire method for this element. However, alkalinictric titration of the phosphoniolybdate, a less tedious procedure, early gained doniinmcc~in fertilizer practice. Althoiigh iiiucli iniiirovcmc~ntin t h e
performance and techniques of the volumetric ammonium phosphomolybdate method has been effected over the years, the presence of ammonium salts in the system has continued to cause trouble in the visual determination of the phenolphthalein end point of the titration. Recent studies (14, 65) have provided additional evidence that this difficulty can be overcome by reacting t h e ammonium with formaldehyde to form hexamethylenetetramine, an expedient suggested as early as 1915 ($9). Use of a n automatic titrator, operating o n a differential potentiometric end point system, eliminates the personal equation in detecting the end point ( I 4 ) . Another difficulty in the volumetric ammonium phosphomolybdate method is the liabilit'y to variation in the composition of the precipitate under different circumstances, particularly the interference occasioned by the sulfate present in m:my fertilizers. .4 newly proposed method, proniising to be very useful in fertilizer analysis, involves precipitation of the phosphorus as quinolinium phosphomolybdate which may be either titratrd alkalimetrically (75) or I\ eighed as such (sa). The quinoliniuni conipouiid is very insoluble, has a definite coniposi[PO?.1211003]--and tion-(C$Hj")H3 contains only 1 .40yc phosphorus. Sulfate and the other common constituents of fertilizers generally cause little or no interference in the method, and the ,quinolinium (compound. unlike ammonium phospliomolybdate, appears to have no serious tendency to adsorb or occlude impurities. Quinoline, being a much weaker base than ammonia, does not interfere in the :dkalinietric titration. Photoiiietric determination of phosphorus in fertilizers has received serious attention in only the last 10 years. The molybdenum blue method, well suited for soils and other low-phospliorus materials, has generally proved unsatisfactory for fertilizers because of its very high sensitivity. I n 1948, Iion.cvcsr2the molybdovanadate method, first tl(wri1)cd 30 years earlier for phosphorus in steels (5U), n'as successfully applied t o phosphate rock (6). With further study and modification it has h w n adnptcd to a xide variety of fc~rt~ilizcrs and is iiicludcd in the proc,cdurcs of thc *issociation of Official .~gric~ultural Chemists ( 1 3 ) . The riicthod is rapid and is capable of high accuracy and precision on materials Ivhich do not yield colored solutions or solutions containing ions other than orthophosphate that form colored coniplexrs with molybdovanadate. Recently, the molybdovanadate method was successfully adapted t o continuous analysis of tailings from a plant beneficiating phosphate rock in
Florida (63). In another syst'c.111 of continuous analysis (60), probably applicable to some fertilizers, phosphorus is determined in detergents with the aid of the molybdenum blue reaction (51). A highly accurate gravimetric method for determining phosphorus in fertilizers by double precipitation as magnesium ammonium phosphatr. without preliminary separation as ammonium phosphomolybdate, \\+asdescribed some 20 years ago (42). Recently proposed modifications accomplish the determination, either gravimetrically (25, 64) or volumetrically (46) with a single precipitation of the phosphate by sequestering calcium and other interfering cations with a chelating agent [(ethylenedinitri1o)tetraacetic acid] and lactic or citric acid, Such cations may also be eliminated by means of ion exchange, resins (411. ~
POTASSIUM
Determination of potassium in fertilizers has long been done principally bjtwo gravimetric procedures. The perc,hlorate method is generally preferred in E:urope, \\,hereas the chloroplatinate method is commonly used in S o r t h America. Significant iniprovements in both procedures have hcen macle from time to time, and other nirthotls are gaining favor. The most important niotlification of the vliloroplatinate mrthod ~ i i p l o y s aqua regia digestion of the Folutionprepared from the sample in the usual manner-to remove aninioniuni and reduce int'erfercnce 11y othcr substances (30. 61). It eliminates several tedious and time-consuming operations. it leseens the chance of niwhanical losscs. and impurities in the ivcighet! potassium chloroplatinate are usuall\- rctlucc~l to insignificant amounts. Several recent methods for potassiriiii in fertilizers are based on its precipitation as the tetraphenylhorate, K[B(CsHJ4], antl completion of the dcttrminatioii either gravinictricall!- ( 7 , 31) or volumetrically (8, 33, 65). Tlic interference of nnimoniuni is avoitld 11y its coniplrsing with formaldehyde. I n one important niodificatic~n(35, 65) the potassium is precipitated with an wccss of standard sodium tetraphenyliioratc solution, and the excess ( i f tetraphcriylborntc is tit,rated with a standard solution of a quaternary amiiioiiiiiiii chloride (Zcphiran chloride or c.ctylt~irnethylnrliiiiiioniuni chlorid~) in tlie presence of bromophenol blue indicator. This modification is rapid and compares favorably with tlie chloroplatinate method in accuracy. The flame photometric method as first used to determine potassium in fertilizers (56) is subject to interference from the quantities of certain ions commonly present in such products. I n a recent modification (33, 35. 36) the
interference is substantially eliniinntcd by precipitating the calcium antl niagnesium as the carbonates and removing phosphatc and sulfate with an anion exchange rosin. The method is convenient and very rapid, and its accuracy is coniparable to that obtained with conventional cheniical methods. Worthy of mention are seiwnl methods for potassium which have not found extensive use in fertilizer ami\?-sis. One involves its precipitation as the dipicrylaniine salt and complr4on of the detcrinination by gravimetric or colorimetric procedures (40). Fornintion of this ,salt is the basis of a trc.hnically sound but a t present uneconoiiiical process for recovering potassium from sea water (11). Precipitation of potassium as thc cobaltinitrite has long been used for its separation from s u b stances intcsrf(,ring in the perchlornti, method. The natural radioactivity of potassium affords a r:ipid nicans for its clctermination in ~)otassiumsalts ( 5 . 67). However, nir.tliotls utilizing this prol~crty are restric.tcSt1 in thcir applicatio~i hccause of thr prcwncc of othvrradioactive. c~lrinciits in man). E d h e r s (76). SECONDARY ELEMENTS
The tinie-lioiioretl oxalate :inti :11iinioniuni phospliutr methods, niodific,tl and iniproved ovcr thr ycars, have colitinued tc! lie t h r principal ways of ( 1 ~ terinining culcirun and magnesiuin, respectivelj., in fcrtilizers. Aniong thr muny other procetlurcs for these elrmcwti;, thr most promising appear to be thP recentlg dcvelopc~l methods for their titration with (ethylcnctliiiitrilo)tetrawetic acid. T h e earlier methods usually involved :I titration for total c~:ilciuni :nit1 ni:ignesiuni using I.:rioelironie l3l:ic.k T as tllc' indicator and a second titration for calciuni with iiiurcxide as the indicator. -1s tlie niagncsium \vas calculated liy diffcrcnc*t~,the crrors in both titrations ivere rrflrctcd in its values. Later iiiodifications pcrniit indcpendcnt detcmiination of the magnesium by first precipitating the calciuni as oxalatc, sulfite, or tungstate (4, 34, 44). Interftirrncp of the orthophosphate ion is ovc'rconie by its rcmoval \r.it,h an anion cwhange resin (16, 34) or precipitation as the ferric salt (73). With t h r w modifications the results reported on limestones and fcrtilizers are genrrall). equal in accurary and precision to thosr obtained Jvith the customary but more tedious method or contributions to the, analytical choniistry of sulfur in fvrtilizcxrs appear to Iinve been made. MICROELEMENTS
Boron. The v-ell-known alkaliiiietVOL. 31, NO. 12, DECEMBER 1959
1947
ric titration in the presence of mannitol is the basis of t h e usual methods for boron in fertilizers. Recent modifications (9, 71) avoid the methanol distillation of the boron, provide for more accurate determination of the end point of the titration, and simplify the analysis in other ways. The many colorimetric methods for boron appear to have found little application to fertilizers. Such applications include, howevcr, the use of chromatrop 2 I3 (69) or quinalizarin (66). Flame photometric procedures have been described for fertilizers (11) and boron minerals (IS),. Copper and Zinc. Analysis of fertilizers for copper is generally done in t h e United States b y iodometric methods (52). Excellent results b y a polarographic method have also been reported (39). The dithizone (diphenylthiocarbazone) system of isolation and analysis (45) is very useful in the determination of small concentrations of copper and zinc. I n one procedure developed for fertilizers it is used in connection with paper chromatography (10). Isolation of these elements, as well as manganese and molybdenum, may also be done with 8-quinolinol (18). TKO official methods are available for zinc in fertilizers. I n the gravimetric method, zinc is precipitated as the sulfide from the copper-free solution and is weighed as the oxide. The photometric method employs the dithizonate reaction. A polarographic method (39) gives results that agree closely with those by the official procedures. Manganese. I n the United States t h e colorimetric periodate and t h e volumetric bismuthate methods have been t h e official procedures for manganese in fertilizers for about 20 years. A flame photonietric method (94)may also bc useful for this purpcse. Molybdenum, Chlorine, and Iron. Fertilizers are seldom analyzed for An applicable method involves its photometric determination n-it,h the aid of &thiol (20, 21). The hlohr method has long been the official procedure for chlorine in fertilizers. Iron is commonly determined by the voluniet’ric dichromate method. EVALUATION OF NUTRITIVE QUALITY
The individual forms of a nutrient element often vary rvidely in their reactivity, and they may differ greatly in their performance in the field. Thus, evaluation of the nutritive Potential of a fertilizer requires information not only on its content of the respective elements but also on their reactivity (in fertilizer parlance comF~~ the manly latter purpose, resort is had to rapid laboratory procedures which generally
1948
ANALYTICAL CHEMISTRY
(16) Brunisholz, G., Genton, M., Plattner, E., H d v . C h k Acta 36, 782 (1953). (17) Chem. Trade J. 134, 704 (1954); 137, 748 (1955). (18) Chichilo, P., Specht, A. W., Whitta38, k e r 903 ~c. (1955). J . Assoc. ofic* A g r . Chemisfs
involve solvent extraction of the fertilizer under closely defined conditions and which are designed to give results that correlate broadly with average crop-response data. Because forms of the-elements that are readily soluble in water are generally considered to be excellent nutritive materials, evaluation of the n-ater-insoluble fraction of fertilizers is the primary objective of such procedures. Until recently, natural organic products were the only source of waterinsoluble nitrogen in fertilizers, and the availability of such nitrogen was determined by the neutral and alkaline permanganate procedures. These procedures arp not suitable, however, for evaluating the quality of the nitrogen in the new urea-formaldehyde materials, the first synthetic fertilizers to carry substantial percentages of waterinsoluble nitrogen (19). A method applicable to urea-formaldehyde materials makes use of the differential solubility of the nitrogen in water and in a buffer solution of potassium phosphate (54). I n the United States, for more than 7.5 years, solubility in neutral ammonium citrate solution has been the chief criterion of the availability of water-insolublr phosphorus (48). Procedures in other countries generally involve the use of amnionium citrate or citric acid solutiors (48). Little attention has yet been given to procedures for evaluating n-ater-insoluble forms of the other elements. Better laboratory tcchniques for rapid estimation of the nutritive potential of fertilizers continue to be an insistent need.
W.j
(19) Clark, K. G., Yee, J. Y,, V. L., Lundstrom, F. O., J . Agr. Food Chem. 4, 135 (1956). J. H . ~ANAL. (21) Clark, L. J., Hill, W. L., J . Assoc. Ofic. Agr. Chemisls 41, 631 (1958). (22) Davis, H. A., Ibid., 41, 525 (1958). (23) Dean, J. A., c., ANAL. CHEM.2 7 , 4 2 (1955). (24) ~ i ~W, ~A., ~~ l ~ , i C. ~E., kbid., ~ ~ 27, 1484 (1955). (25) Donald, R., Schlvehr, E. W., ITilson, (26) H. Ellis, N., J . G. Sci. c., FoodFormaini, Agr. 7, 677R.(1956). L., J. ~~~d Chem. 3, 615 (1955). (27) Engelbrecht, R. M., RlcCoy, F. A., ANAL.CHEM.28,1619 (1956). ( 2 8 ) Etheredge, p., J * Assoc. Oflc. Agr. Chemists 32, 241 (1949). (29) Falk, K. G., sugiura, K., J . Chem. SOC. 37, 1507 (1915). (30) Ford, 0. W., J . Assoc. O$c. Agr. Chemists 36, 649 (1953). (31) Ibid., 39, 598 (1956). (32) Ibid., p. 763. (33) Ibid., 41, 533 (1958). (34) Gehrke, C. W.,Msprung, H. E., Y. C., ANAL. CHEM. 2 6 , 1944 (1954). (35) Gehrke, C. w., M ~ H, E.,~ Wood, E. I,., J . Agr. Food Chem. 3, 48 (1955). (36) Gehrke, c*w.* Wood, E. L*, hfissour1 Agr. Expt,. Sta., Research Bull.
635, (1957). ( 3 7 ) Gottlieb, 0. R., hlagalhiies, hf. T., A N A L . CHEM. 30, 995 (1958). D. Demkovich, .’ A., (38) J . Agr. Food Chem. 7, 26 (1959). (39) ~ ~ ~ K.b J,, ~J . ~A ~~ ofic, k~ , ~ Agr. Chemists 35, 791 (1952). (40) Hanson, b’.C., Fertiliser SOC.( E n d . ) Proc. 16, 33 (1952). (41) Helrich, K., Rieman, FV., 111, Ax.4~.CHEM.19, 651 (19-1.7). (42) Hoffman, J. I., Lundell, G. E. F., J . Research Xatl. Bur. Standards 19, 59 (1937). (43) Ibid., 20, 607 (1938). (44)Hoffman, W. M., Shapiro, H., J . Assoc. Ofic. A Q T . Chemists 37, 966 (1954). (45) Holmes, R. .4.,sod sci. 59, 77 (1945). (46) Huditz, F., Flaschka, H., Petzold, I., 2. anal. Chem. 135, 333 (1952). (47) Jacoh, K. D., AXAL. CHEX 21, 208 (1949); 22, 215 (1950). (48) Jacob, K. D., Hill, W.L., in “Soil and Fertilizer Phosphorlls in Crop Sutrition,” p. 299, Academic Press, Xew York, 1955. (49) Jander, G., Gensch, C., Hecht’, H., 2. a n d . CheTn. 128, 46.8 (lg48). (50) Jongen, G. H., Bcrkhollt, H. W., Chem. Weekblad. 5 2 , 909 (1956). (51) J . Agr. Food Chem. 7, 82 (1959). (52) J . A S S Q COfiC. . A7r. Chemists 24, 67(1041); 25,77(1942). (53) Ibid., 41, 32 (1958). (54) Kralovec, R. D., hrorgan, W. A.,
~
~
K.j
LITERATURE CITED
( 1 1 AXVAL. CHEY.31, No. I , 17 A(1959).
Florida Phosphate Mining Chemists, “Xlethods Used and Adopted,” 1948 ed. (3) Assoc. Offic. Agr. Chemists, Washington, Analysis,” D. 8th C.9 ed., “Official 1955. 3fethod5 Of (4) Baneivicz, J. J., Iienner, C. T., ASAL. CHEK 24, 1186 (1052). (5) Barnes, R . B., S d k ~ rn. , J., ISD. E N G . CHEXf.2 ~4x.tL.E D . 15, (1943). (6) Barton, C. J., ANAL.CHEX.20, 10G8 (1948). ( 7 ) Rcrkhout, H. W.,Chcm.. Weekblad. 48, 909 (1952). ( 8 ) Berkholit, H. W,,Jongen, G. H., Ibid., 51, 607 (1955). (9) Berry, R . C., J . Assoc. O$C. Agr. ChemiPls 36, 623 (1953). (10) Bonig, G., La~rdw. Forsch. 6 , 177 (1954). (11) novny, I.:., coSsy, A , , Mitt. Gebiete Lebensm. u . Hyq. 48, 59 (1957). (12) Brahson, J. A., A S A I I . CHEhf. 29, 643 (1957); sl, ‘88 (’“”* (13) Brabson, J. A,, T h n n , R . L., Epps, E:. A., jr,, ~ ~ f 1 ~ f .&I., ~ Jacob, ~ K. I)., J . Assoc. O$r. Agr. Chemists 41, 517 (1958). (14) R-rabson, J. .4., Wilhide, W.D., Ibid., 40, a94 (19571. (15) Bridger, G. L., ANAL. CHEM. 25, 17 (1gC53);27, 632 (1955).
,
( 2 ) Assoc.
~
(55) J . Agr. Lehmann, Food Chem. W.,2,Bodenk. 9’ (1954)* t i . P$anz a e m d w . 9-10? 766 (1938’. (56) Lundell, G. E. F., Hoffman, J. I., ~ ~ , J . Assoc. ofic. Agr. Chemists 8 1 184 (1924). (57) Auto.4nalyzer Lundgren, D. for p Selective .2 “The DeterminaTechnicon tion of Orthophosphates and Total Inorganic Phosphates,” Division of
~
,
Anal. Chem., 135th Meeting, ACS, Boston, April 1959. (58) Miller, It. D., J.Assoc. Agr. Chemists 31, 373 (1918). (59) hfisson, G., Chemiker-Ztg. 32, 633 (1908). (60) Muller, It. H., ASAL. CHEM. 30, No. 1, 53 A (1958). (61) I’errin, C. H., Zbid., 21, 984 (1949). (62) Perrin, C. H., J. Assoc. Ojic. Agr. Chemzsts 41,758 (1958). (63) Reuss, J. L., Graves, H. B., Northcott. E..“ I ~ e v e l o ~ m e noft a Continuous ‘l.,C&,haly&r,” Meeting of Am.
Inst. Mining Engrs., Sew York, February 1958.
(64) Saint-Chamant, H. de, Vigier, R . , Bull. SOC. chzm. France 1954, 180. (65) Schall, E. I)., ANAL. CHEJI. 29, 1044 (1957). (66) Scharrer, K., Kuhn, H., Luttmer, J., Landwzrtsch. Forsch. 8, 26 (1955). (67) Scheel, K., Angew. Chem. 66, 102 (1954). (68) Shuey, P. McG., J . Assoc. O B . Agr. Chemists 38, 761 ( 1955). (69) Stettbacher, A., 21.Iatt. Gebaete Lebensm. u. Hyg. 34,90 (1943). (70) Stout, P. It., Johnson, C. M., Yearbook Agr., U. s. Dept. Agr. 1957, p. 139.
(71) Taylor, D. S., J . .lssoc. Ogic. A g r . Chemzsts 32, 422 (1919). (72) Thornton, S. F., Conf. on Chem. Control Problems, p. 37, S a t l . l’lant Food Inst., Washington, U. C., 1957. (73) Van Thiel, H. L,Tucker, W. J., J. Agr. Food Chem. 5, 442 (1Y.57). (74) Watt, G. W., Chrisp, J. U., ANAL. CHEM.26, 452 (1951). (75) Wilson, H. N., Analyst 76, 65 (1951); 79, 535 (1954). (76) Wilson, H. N.,Lees, I). S., Broomfield, W., Zbid., 76,355 (1951).
RECEIVEDfor reviem Xugllst 2 5 , 1959. Accepted August 25, 1059.
Some Recent Developments and Current Problems in Metal Analysis ROBERT M. FOWLER Technology Department, Union Carbide Metals Co., Division of Union Carbide Corp., Niagara Falls, N.
,Determination of carbon in steel is discussed as an example of the progress in metal analysis in 40 years. The real revolution has come in the last 15 years with the direct-reading spectrograph and x-ray spectrometer. The future of analytical chemistry lies in development of specialized tools.
T
Fisher Award honors Dr. Hoffman for his contributions to analytical chemistry, which have been many, but does not mention the great influence his clear and direct approach to problems has had on the thinking of others. It may be interesting to consider the advances in metal analysis that have been macle during the time the Award winner has been concerned with this field. His first publication was in 1921, on the determination of cobalt and nickel in steel (6). This was a thorough classical approach to the problem. He showed that to obtain precise results a nuniber of separations and recoveries had to be made. It was a lengthy and time-consuming procedure, but the important thirg a t that time was not how long it took but that it was possible, b y applying all the necessary corrections, t o obtain prrcise results. I would estimate that 6 to 10 determinations by this procedure ir-ould require 3 mandays. Although many papers have been published since on this determination, the procedure developed in 1920 was the standard procedure for cobalt until the late 30’s and is still used. Because the field of metal analysis is so very broad, it is impossible to even mention all the. progress that has been HE
made in the nearly 40 years since Dr. Hoffman published his first paper. Instead of trying to cover the field, I would like to consider only one determination-the estimation of carbon in steel as a n example of the progress that has been made-chosen because in 1920 i t was one of the fastest determinations the steel chemist could make. CARBON IN STEEL
At that time, the bible of the steel chemist was Blair’s Chrniical Analysis of Iron and Steel (3) which originally appeared in 1888 and had gone through seven editions by 1920. Incidentally, the seventh edition makes no mention of standard samples. Even common volumetric solutions were standardized by very time-consuming methods that lacked precision except in the hands of a very skilled ninnipulator. nIost steel methods were suitable only for plain carbon steels and, even then, in many cases, the situation vas little better than the somewhat earlier experience of F. W, Sniither of the Sational Bureau of Standards. Sniither a s employed a t a sninll blast furnace to determine carbon in pig iron. There was also an old fellow named Jim n-ho estimated the carbon and gradcd the iron by fracturing a pig and looking a t the fracture. As Smither told it, it was many nioiiths before he could convince the blast furnace superintendent, in the event of a dispute, that the chemically determined figure for the carbon content was the correct one. While platinuni had been relatively cheap and some of the steel works still used platinum combustion tubes and
Y.
boats, the common reagents were of doubtful quality. Fortunately, most of the steels were either plain carbon or low alloy. Imagine trying to detcrmine carbon in one of the highly alloyed materials n’e run routinely today using a gas-fired furnace with a maximum temperature of perhaps 1100” C. as recommended by Blair. The precision some of these early workers attained was attained a t a cost of time which made most of their analysc~historical. Many will recall H. V, Churchill’s definition of a control analysis as one that is received by the mctallurgist i n time for him to do sonicthirig about it, and a historical analj.sis as one rcceivetl too late for the customer to do anj’thing about it. If one follon-ed Blair’s procedure, a carbon noultl rcquire a t least a n hour. Of course, the chemist made more than eight per day bccausc 8-hour days n’ere unknown then, and faster procedures than those dmcribed by Blair were used in some places. Many people h a w contributctl t o the progress in this ratlwr simple operation of burning a n-cighetl amount of a metal in oxygcn and estimating the amount of carbon dioxide formed. Fen. radically new idcns have been introduced, but as progress \KIF macle in furnaces and devices for purifying an(l estimating the carbon dioxide, the timc has been shortcncd and the precision improved. The nickel-chrorre alloy resistor furnace n-as a big iniprowment over the gas-fired furnace and tl:c silicon carbide resistor furnaces were a further improvement. These furnaces rcquiretl superior combustion tubes ant1 boats of more refractory matcrials, but now for low-carbon materials a new difVOL. 31, NO. 12, DECEMBER 1959
1949
