A N A L Y T I C A L CHEMISTRY
96 Table YII.
Total Capacity of Some Ion Exchange Resins Resin
70 N
Sulfonic acid cation exchanger Sulfonic acid cation exchanger Sulfonic acid cation exchanger Carboxylic acid cation exchanger Anion exchanger Anion exchanger
,, ,,,
.
,
..
.,.
4.0 14.2
70 S
Total Exchange Capacity Theory Experimental
5.4 8.1
14,4
... .,. ...
1.73 2.60 4.62
...
2.86 10.1
1.70 2.55 4.58 11.0 2.81 10.0
countered during such a determination. However, commercially available organic exchangers have stable structures that mill permit an accurate determination of their total capacity without degradation. In brief, the procedures involve the transformation of the exchanger to either the hydroxyl form for anion exchangers or the hydrogen form for cation exchangers. The resins are then examined by either of two methods. For strong acid and strong base exchangers, an extraction with a neutral salt will liberate a titratable quantity of acid or base equivalent to the total capacity. T h e treatment of the ireak acid and ireak base exchangers requires treatment with an excess of standard acid and base and an analysis of the amount of acid or base neutralized after equilibration. Determination of the exchange capacity of resins by the above procedure usually agrees with a chemical analysis of the active groups contained in the resin (see Table VII). Ion Exchange Apparatus. The apparatus for utilizing ion exchange substances may be fashioned from ordinary equipment used for chromatographic analyses. However, several investigators have designed several types of apparatus that may be utilized simply and exhibit certain obvious advantages. Figure 18 illustrates a simple appara us that may be employed for semimicrooperations and contains approximately 1 nil. of exchanger. Figures 14 to 16 illustrate apparatus designed for macro work. An apparatus designed for following the analysis of the effluent continuously by radioaction measurements is illustrated in Figures 17 and 18. The use of ion exchange in analytical chemistry is not a panacea but it has simplified many analytical operations. As chemists become more and more acquainted with the principles of ion exchange and the properties of ion exchange substances, we may expect, to find ion exchange in analytical chemistry taking its place along Tvith chromatography and other related analytical processes. LITERATURE CITED
Abrahamiczik, M.,Mikrochem;e, 25, 228 (1938). Anon., Resinous R e p o r t e r , 9, Xo. 4, 1 (July 1948). Bergdoll, M. S.,and Doty, D. M.,IKD.ENG.CHEX, Ax.4~.ED., 18, 600 (1946). (4) Blumer, M., Erperientia, (Is’) 9, 15.IX, 351 (1948). (5) Boyd, G. E., .4damson, A. IT., and Myers, L. S., Jr., J . Am. Chem. Soc., 69, 2840 (1947).
Boyd, G. E., Myers, L. S.,Jr., and Adamson, A. W., Ibid., 69, 2854 (1947). Boyd, G . E., Schubert, J., and Adamson, A. W.,Ibid., 69, 2818 (1948). Cannan, K., 4nn. A‘. Y . Acad. Sci., 47, 135 (1946). Cernescu, X . , Dissertation 661 Eidg. Technische Hochschule, Zurich, 1933. Clarke, B. L., and Hermance, H. IT., ISD.ENG.CHEM.,~ N A L . ED., 10,591 (1938). Cranston, H . -4., and Thompson, J. B., Ibid., 18, 323 (1946). Dole, M.,“Glass Electrode,” p. 273, Kew York, John Wiley & Sons, 1941. Drake, B., Satzire, 160, 602 (1947). Folin, O., and Bell, R. D., J . Biol. Chem., 29, 329-35 (1917). Gaddis, S.J., J . Chem. Education, 19, 327 (1943). Harris, D. H., and Tompkins, E. R., J . Am. Chem. Soc., 69, 2794 (1947). Helrich. K., and Rieman, W., IND.ESG.CHEM.,ANAL.ED., 19, 651 (1947). Jaeger, F. M., Trans. Faraday SOC.,25, 320 (1929). Jenny, H., Kolloid-Beihefte. 23,428 (1927). and Boyd, G. E.. J . Am. Chem. Soc., 69, 2800 (1947). Ketelle, B., Kolthoff, I. M.,and Sandell, E. B., “Textbook of Quantitative Inorganic Analysis,” p. 116, Yew York, Macmillan Co., 1945. Kunin, It., and Barry, R. E . . Ind. Eng. Chem., in press. Kunin, R., and McGarvey, E‘. X., Ihid., in press. Kunin, R., and Myers, R. J., J . Am. Chem. Soc., 69, 2874 (1947).
Kunin, R., and Winters, J. C., Colloid Symp., .hmy Chem. Center, June 1947. Lur’e, Yu. Yu., Zaaodskaya Lab., 13,532 (1947). Lur’e, Yu. Yu., and Filippova, N. A . , Ibid., 13, 539 (1947). hfoller, J., Kolloid-Beihefie, 46, 1 (1937). Myers, R. J., “Advances in Colloid Science,” p. 317, New York, Interscience Press, 1942. Myers, R. J., Eastes, J. W., and Myers, F. J., Ind. Eng. Chem., 33, 697 (1941). Myers, R. J., Eastes, J. TI-., and Urquhart, D., Ibid., 33, 1270 (1941). Riches, J. P. R., X a t i t r e , 158, 90 (1946). Samuelson, O., I V A , 17, 1 (1946). Samuelaon, O., Ph.D. dissertation, I-Iorsal. Sweden, 1944. Samuelson, O., Suensk. Kem. Tid., 57, 91 (1945). I b i d . , 57, 114 (1945). Ibid.,57, 158 11946). Ibid., 57, 250 (1915). I b i d . , 58, 247 (1946). Ibid.,59, 14 (3947). Sandell, E . B., “Colorimetric Determination of Traces of Metals,” p. 16, New York, Interscience Press, 1944. Schachtachabel, P., Kolloid-Beihefte, 51, 199 (1940). Schubert, J., J . Phys. Colloid. Chem., 52, 340 (1948). Schubert, J., and Richter, J. W., Ibid., 52, 350 (1948). Spedding, F. H., et al., J . Am. Chem. Soc., 69, 2786 (1947). Sussman, S.,Ind. Eng. Chem., 38,1228 (1946). Thompson, H. S., J . Roy. SOC.Engl., 11, 68 (1850). Tiselius, d.,Drake, B., and Hagdahl, L., Ezperimentia, 3, Fasc. I. 15.1 119471. ToAnpkins: E. R., Khym, J. X . , and Cohn, TI7. E., J. Am. Chem. Soc., 69, 2771 (1947). Yanselow, A. P.. J . Am. Chem. Soc., 54, 1307 (1932). K a y , J. T., J . Roy. SOC.Engl., 25, 313 (1850). Wieaner. G.. J . SOC.Chem. Ind., 50, 103T (1931). Wikiander, L., Ann. R o y . i i g r . Coll. Sweden, 14, 1 (1946). Winters, J. C., and Kunin, R., Ind. Eng. Chem., in press. RECEIVED Xovember 13, 1948.
NUCLEONICS CHARLES L. GORDON, Ahtional Bureau of Standards, Washington, D . C .
E
VERY analyst is familiar with the fact that radioactive
elements in all forms of chemical combination can be identified, and quantitatively determined in extraordinarily minute quantities, by measuring the kind and amount of radioactive emission of the disintegrating nuclei. T h e application of radiation phenomena to the study of chemical reaction has progressed very rapidly in recent years. With the dropping of the first atomic bomb, the developments
in nuclear science made in the preceding 5 years were brought suddenly to the attention of the public. Most of the vast accumulation of data had been withheld from publication and now is only slowly being released from classification. The most notable advance was the successful operation of a chain-reacting pile (97). This provided a source of neutrons both for the largescale production of new radionuclides ( 6 1 ) and for the measurement of properties of atomic nuclei. The development of large
V O L U M E 2 1 , N O . 1, J A N U A R Y 1 9 4 9 facilities for the separation of stable isotopes together with the thermal neutron pile led to a sudden evpansion of the number and amount of the available radioactive and stable isotopes. For isotopes not capable of production by the pile, the cyclotron is the next most important means which can produce not only all the isotopes made in the pile but marig others (65). This article reviews the publications of the past 2 vears in the field of nucleonics that relate essentially to problems of analvsis. Its three main sections deal with types of procedure, methods of measuring radioactivity, and other related matters. TYPES O F PROCEDURE
Tracer Methods. Since the chemical properties and many physical properties of radioactive elements are substantially identical with those of their inactive isotopes, it is possible t o study chemical reactions by substituting radioactive elements for all or a part of the inactive ones. By measuring the activity of the mixture it is possible to determine the processes nhich occur with a degree of speed and accuracy not to be hoped for from other methods. This method is generally referred to as radiochemical tracer techniques. These techniques are most extensively used in the study of physiological processes, but they also provide a powerful tool of investigation for the analytical chemist. The simplest and most widely used method of utilizing the radioactive emission of a radionuclide (61) is as a tracer or tagged atom. Here the radioactive atom and its nonradioactive isotope are carriod together throughout a n operation, and are finally again determined by their knov-n specific activity. For instance, in a simple case in Tvhich samples of determined specific activity n-ere used, Thiers (103) and his eo-workers surprisingly found that no ruthenium n-as lost by volatilization during the fusion and crystallization operations of t h r fire assay, whereas considerable ruthenium passed into the slag and the cupel. To ascertain that n o ruthenium n-as lost by volatilization would have been extremely difficult, if not impossible, without the aid of a radioisotope. In testing the completeness of the cslectrolytic separation of copper from zinc, Haenny and ?.livc>laz(47),using the isotope ZnGS,found that 1 gram of copper was contaminated by less than 10-16 gram of zinc. The simple tracer technique has been applied to the difficult problem of the separation and determination of the rare earths. Studies ( 5 9 ) on separations by ion-exchange using radionuclides brought out the superiority of Doivex 50 over Amberlite IR-1 when the activity was found to decrease to background between each band of activity in the former. I n their study of the relative adsorbability of the rare earths on Don-ex 50, Ketelle and Boyd (59) found the order La > Ce > P r > S d > 61 > Sm > E u > Gd > T b > D y > Y > Ho > Er > T m > T b > Lu, with and Ho as the most difficultly separable of all the triplet Dy, I-, of the rare earths. With Amberlite I R-1, Boyd et al. (16, 1 ; ) found the order of absorption affinity was La > I' >> Ba >> C s > R b > K > S H s > X a > H > Li. One of the most useful techniques of analysis using the radioactivity of active isotopes is that of isotope dilution, most used in biochemical investigations (68, 84). The method can be used in two principal ways as outlined by Henriques and Nargnetti (53).
I. The active compound, P * , of known amount mgp*, is added to a system containing the unknown quantity of nonradioactive compound, P. After mixing, a sample, mgpp*, of the mixed compound, PP*, is taken and the ratio, R, of the specific activity of P* to t h a t of PP* is found, when mg,
=
mg,* ( R - 1)
11. The reverse procedure, usually called inverse isotope dilution, is carried out by adding a known amount, mg,, of nonradioactive compound, P , to a system containing the radioactive compound P* (and none of the nonradioactive compound) in a mixture of other radioactive compounds. The mixed compound, PP*,is isolated in the pure state and the ratio, R, of the specific activities is found by determining the specific activity of PP* and
97 calculating the specific activity of P* by stoichiometry from the known activity of the radionuclide. The amount of radioactive compound is then mg,* = mg, ( 1 / R
-
1)
A discussion of the precisionof these methods is g:ven by Radin (84). When all of the compound containing PP* cannot be isolated in the pure state-i.e., only an unknoFvn fraction of the whole mixture can be used-the dilution method must be modified. Bloch and Anker (f 6 ) suggest using two consecutive reverse isotope dilution experiments (method 11) with aliquots of different amounts of normal carrier added for the case \There the original amount of the compound was too small to be isolated in pure form. The error of estimation, holvever, is greatly increased. Bn exact set of equations for isotopic dilution experiments was given by Gest, Kamen, and Reiner (40, 68). Induced Radioactive Excitation Methods. A most interesting procedure, and one of limitless possibilities, is to subject ordinary materials to bombardment with various particles or forms of radiation, and thus to convert some of t'hese ordinary atoms to radioactive ones. These radioactive atoms may be isotopes of the original atoms or they may be entirely different elements. The resulting activity is then determined by one of the usual methods for such determinations. Sagane et al. ( 9 0 ) used such a method to det,ermine sodium in aluminum. By bombarding the metal with dwterons having an enr'rgy 3 m.e.v., they were able to determine the sodium content to a limiting value of 0.001%. In this type of method, bombardment may likewise he done by neutrons or protons. For example, Von iirdenne and Bernhard (106) determined carbon in iron samples by measuring the activity of the isotope S I 3 nhich \vas produced from C1* by bombardment ivith 1 m.e.v. protons, as vie11 as with deuterons. Such a method depends on the relatire activation cross sections of the elements present. The term "cross section" is a way of stating the probability of a reaction's taking place. I n this instance it is the proha1,ility that the bombarding particles will produce an active nuclide. The utilization of relative activities produced ill-nuclear excitation is not limited to corpuscular radiation. The absorption of y-rays by beryllium and deuterium, n-ith subsequent production of neutrons, was utilized by Victor (105) in dextermining radium and radiothorium. The yield of neutrons produced by the action of the x-rays on beryllium and deuterium \vas determined by measuring the p-radiation produced in silver foil by the paraffin-sloTved neutrons, and comparing the value obtained tvith that of a standard mixture. If the total emission of the original sample is known, the mesothorium content can likewise be found. An interesting example of this technique was combined with the separation by ion exchange in the analysis of a sample of highly purified erbium, which gave no spectral lines of any other rare'earth, for the amount of thulium present as an impurity (59). Processing on the Dowex 50 column after neutron bombardment gave traces of lutecium, ytterbium, 'thulium, and sodium besides the erbium. Assaying the thulium with a known counting geometry gave the number of Tn1170atoms. From the neutron cross section of Tm169, the neutron flux of the pile, the time of bombardment, and the number of Tm170atoms produced, the amount of T1nlfi9originally present was calculated. This example is an illustration of the production of extraneous radioelements. Such mixtures of radioactive substances havr t o be separated by some means from the particular radionJclide desired. The subject of such contaminants in tracers \vas covered by Colin ( 1 9 A ) . Besides chemical methods of separation, two physical methods are used. Differential decay, the simpler of these, takes advantage of the relative decay rates by letting short-lived nuclides decay to insignificant activities before measuring the activity of the nuclide under study; or more generally, measuring the activity a t two or more different times. The contributions of each component are then calculated as the sum of the individual contributions
ANALYTICAL CHEMISTRY
98 Differential Absorption. When the energies of the radiation from two (or more) radionuclides are sufficiently different, one radiation may be preferentially absorbed by some material. The other radiation of higher energy, not stopped by the absorber, then can be counted separately. .4 method of analysis based on differential absorption was used
by Nag-Chowdhury, Das, and Dasgupta ( 7 6 ) to determine uranium and thorium simultaneously by measuring the radiation with absorbers of different thicknesses. Nag-Chowdhury and blonsuf ( 7 7 ) estimated the uranium and thorium by means of the a-activity by comparison of the absorption curves of mineral samples lvith those of samples of kno\\n uranium and thorium content. The maximum energy of the p-emission is a characteristic of the particular radionuclide. Use may be made of its detcrmination as a means of chemical identification. The foyer, B. J.. Peters, B., and Schmidt, F. H., P h y s . Rev.,69, 666 (1946): (MDDC 171). (76) Nag-Chowdhury, B. D., Das, Sudhansu. and Dasgupta, 8., Proc. S a t l . Inst. Sei. I n d i a , 10, 167 (1944). (77) Nag-Chowdhnry, B. D., and Monsuf, A . K., Ibid., 12, 341 (1946). (78) Ollano, Z . , Rend. ist. lombardo sci. classe sci. mat. nat., 71, 341 (1938). (79) Parker, H. M.,A-ucleonics, 3, No. 4,44 11948). (80) Perfilov, Y . .4., Compt. rend. acarl. sci., U.R.S.S., 42, 258 (1944). JVature, 161, 884 (1948). (81) Poole, J. H. J., and Bremner, J. W., (82) Powell, C. F.,Ihid., 160, 453,486 (1947). (83) Primakoff. H.. Nucleonics. 2. No. 1. 2 (19471 (84) Radin, N. S., Ibid., 1, No. ‘1, 24, No: 2, 48, No. 4, 51 (1947); 2, No. 1, 50, No. 2 , 3 3 (1948). (85) Rainwater, L. J., and Wu, C. S.,Ibid., 1, No. 2, 60 (1947).
(86) Reid, A. F., “Preparation and Measurement of Isotopic Tracers,” Ann Arbor, Mich.. J. W. Edwards, 1946. (87) Riedharnmer, 1.. Safitru~issenchaften, 32, 70 (1944)
(88) Koddis, L. H., ed., “Preparation and Measurement of Isotopes and Some of Their Medical Aspects,” Suppl. t o U. S. Naval
Medical Bull. (,March-Ami1 1948). (89) Russell, B., Sacks, D., Wattenberg; A., and Fields, R., Phys. Rev., 73, 545 (1948). (90) Sagane, R., Eguchi, M., and Shigeta, 6 . , J . Phys. M a t h . SOC. J a p a n , 16, 383 (1942). (91) Seaborg, G. T., Rea. N o d e r n P h y s . , 16, 1 (1944). (92) SegrB, E., “SegrB Chart of Nuclear Properties,” Cambridge, Mass., Addison-Wesley Press, 1947. (931 Serber. R.. MDDC 306. (94) Seren, L., Friedlander, H. N.,and Turkel, S. H., MDDC 408 abs., and MDDC 613. (95) Seren, L., Friedlander, H. N., and Turkel, S.H., Phus. Rea., 72, 888 (1947). (96) Sherr, R., Rev. Sci. Instruments, 18, 767 (1947). (97) Smyth, H. D., “Atomic Energy for Military Purposes,” Princeton, N. J., Princeton University Press, 1945, U. S. (98)
(99) (100) (101) (102) (103)
Government Printing Office, Washington, D. C., 1945. Snell, A. H.. Science, 108, 167 (1948). Stevens, G. W.W., Sature, 162, 526 (1948). Studier, M.H., and IIJ de, E. K., Phys. Rea., 74, 591 (1948). Sue, P., and Martelly, J., Bull. soc. chim., 1946, 410. Szilard. L.. and Chalmers. T. A , . Sature. 134. 462 (1934). Thiers, R., Gravdon, W.,and Beamish, F. E., A N ~ LCHEM., . 20, 831 (1948).
S.Atomic Energy Commission, Isotopes Branch, Sucleonks, 1, No. 1, 64 (1947). (105) Victor, C. P., J . phys. radium, 8, 298 (1947). (106) Yon Ardenne, M., and Bernhard, F., Z . P h y s i k . , 122,740 (1944). (104) U.
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Walker, R., MDDC-362. Way, K., etal., Xucleonics, 2, No. 5,82 (1948). Webb, J. H., Phys. Rev.,74, 511 (1948). Willard, J. E., J . Phys. & Colloid Chem., 52, 585 (1948). U’illiams, R. P., Jr., J . Chem. Phys., 16, 513 (1948). Wouters, L. F., Phys. Rea.,74, 489 (1948). Yaffe, L., and Justus, K. M., Ibid., 73, 1400 (1948). Yagoda, H., Nucleonics, 2, No. 5, 2 (1948). Yagoda, H., andKaplan, N., P h y s . Rev.,72, 356 (1947). Ibid., 73, 634 (1948). Ibid., 74, 1244 (1948). Yankwich, P. E., Science, 107, 681 (1948). Yankwich, P. E., Norris, T. H., and Huston, J., Ax.4~.CHEM.,
19, 439 (1947). (120) Yankwich, P. E., and Weigl, J.
W., Science, 107, 651 (1948).
RECEIVED December 9, 1948.
INDICATORS I. 31. KOLTHOFF Unicersity of Minnesota, Minneapolis, .Ifinn.
Q
UITE generally an indicator in chemistry io a substance which
indicates the presence of a certain constituent. I n this sense all the reagents which are used for the detection of a given constituent are indicators. I n a more limited sense an indicator is a substance which indicates the extent to which a reaction between two or more reactants occurs. I n volumetric analysis the
