( 2 3 2 ) Sd1, A. O., Optika i Spektroskopiya 5,316 (1958). ( 2 3 3 ) Sa&-vyer, D. T., George, R. S., Rhodes, R. C., ANAL. CHEX 31, 2 (1959). (234) Ibid., p. 3. (2353 Sas, S. I., Steinmetz, H., U. S.
.it. Enerw Cornm.., Reot. . ORNAL-
2570 ( i o j i j . (236) Schay, G., Tagy, F., Kirkly, J., Halfisz, I . , J f o g g a r h7&~n. Folydirat 63, 14 (1957). (2371 Sch:iy, G., Szekely, Gy., Riicz, Gy., Ti,:iply. G., Periodica Polyfech. 2, 1 1~ 1958). ( 2 3 8 ) Schmidt, A , , E z p l o s i c s t o f e 5, 1 11957). (2&l Schnelle, P. D., I S A Journal 4, 128 (1957). (240) Schulek, E., Pungor. E., Trampler, J., JIikrochini. -4cta 1958, 52. (2-1;) Schxab, G. l l . , Seuwirth. 0.. C hevi.-Ing.-Tech. 29, 345 (19.57'). (242) Sello. H.. I n d . Ena. Cheni. 50. 1561
.J. I r o n Steel frisf. 188, 138 (1958'1. Shimizu, I I , , J a p a n . Patent 3699
(243
.qtroen. 84, 12 (1957). 2-48 I I b f d , u. 226. ((24:l Shinelev, 13. A , , Zai,odska!,o Lab. 23, 263 (1957). (250'1 Smiley, K,G., -1m. So?. Testing llntrrinlc, Spec. Tech. Publ. 222, 2,5 (1$957I . (2.51) Smith. J. I T , Chein. S Ind. ( L o n d o ) O 1958.' 885 (2.j2 dorg, L. V., Offutt, E. R., U. S. l'ntrnt 2,864,725 (Dec. 16, 19551. (253) dprarklen, 8. B., Campiiell, I). S . , Fellos 8 , C. G , , Ibid.! 2,876,189 ( l l a r c l i 3 , 1959 I. f2,;4) Srivast,ava. B. S . . Sazena. P. C.. J . Chetii Phus. 27., 583 ( 1957) " ( 2 -1.3- J Stnrohintsev, G. L., Ihl'shova,
T. A , , Zhiir. Anal. Khivi. 13, 235 (1958). (256) Steele, D. I., Kniazuk, 11.,I R E Trans. on lnd. Electronics PGIE-6, 64 (\ 19.58). ----, (257) Stocmeier, H. G. L. v., .-Ii,ch. Eisenhiittenw. 29, 95 (1958 I . ( 2 5 8 ) Stott, F. D., Rei. Sci. I m t r . 28, 914 (1957). (259) Strange, J. P., U. S. Patent 2,823,985 (Feb. 18, 1958). (260) Strange, J. P., -4x.4~. C H E ~ I29, . 1878 (1957). (261) Striiter, G., Landwirtrcli. Forsch. 10, 146 (1957). (262) Suzuki, T., Koshi, S.,K t a , H . , 1-amaguchi, H., K o s h u E i s e i i n Kenkyli H6koku 6, 53, (1957). (263) Swann. D. D. -1.. >- - - ~ ~A , . ~ 1Yilli:ims. ~ Analyst 83, 113 (1458). (264) Swift, G. \I7., Christ?,, J. A . , Iieckes, .I, --I., Kuratn, F., C h e i f i . En//. Progr. 54, 47 (1958). 1265) Tarinevsky, O., Vassy$ :I,, Cotjipt. rend. 244. 924 1 1957 1. '
3
Atoniic l?~iergy Resc,nrch 1:stnhl. ( G t . Brit,), ES'R-2124 (1957). 12668) Tijdt. F.. G c r . Patent 937.259
(278) Vehgerov, 31. L., Sivkov,
X.,
Malykh, E. V., Optika i Spektroskopiya
2, 823 (1957). (279) Vines, R. G., Proc. Conf. Thermo-
dynamic and Transport Properties Fluids, 120, London, 1957 (Pub. 1958). (280) Voinov, A . P., Gazovaya Prom. 1958, ?io. 4, 48. (281) ITaclanik, J., Chim. anal. 40, 247 (1958). (282) Wadelin, C. IT., .%NAL. C'FIEX. 29, 441 (1957). (283) ITalker, R. E., ITestenberg, -4.:I., Rev. Sei. Instr. 28, 789 (1957). (284) Wall, R., Ind. Eng. C ~ P ~ 49, JI. 77A (1957). (285) Wallis, G. R-,, Kilde, 5;. A , , Ecoloqv 38, 359 (1957). 1286) IVeaver. E. R.. Hughes. E. E ,
Paper 2864). ( 2 8 7 ) ITebher; J. J., F.S.Patent 2,829,952 (.Ipr. 8, 1958). 1288) Kestenlierg. -4, -4..\Talker, R . I-.,
( 2 0 0 ) \Titten, B.,I'roqtxk, .-I., h . 4 ~ CFIEM.29, 885 (1957). 1291i \l-right. J. 11.. Stiteler, D. .J.,
f
1
r . S . S . R . (English franc/.) 12,
207
(1957). (275) Ihitl., p. 208.
Ulbricht, H., Cher!iI'ker-Zty. 81, 708 (1957). (,277) 'i'agin. E. I-., Petiikhov. S . 8.. 1,'vova. A . l'.. Iiiiiple reason that nen- developnients HI'C largrly ooiifined to a systematic inii i i ' o ~ c ~ i i i t n of t rarigc. precision. rcliaIiiIitJ., and impro1;ed performance. A ~ I I O I Y cogent roason is that our instrunwnt ninnufact~urcrsare continuing to (lo a q,lendid jot1 in describing their iirot luct 8 , t hc t 11?or>. i nvolvrtl, the s BEFORE.
M.
exact details of construction, operat'ional. and maintcnance procedures, and rhuni6s of current applications. Their excellence in this reportorial chore is a continuing challenge to those of us who venbure to write papers or textbooks. Once more, the important instruiiiental developments in each field are usually covcred by the experts who are describing advances in their respective fields. If any general trends are t o be perceived in the past two years, thc author would be inclined to mention the following. In electronic circuitrj- oiie is
struck hy the great degrec to nhich circuitq have been transistorizcd. with rewltant improvements in poucr consumption, w i g h t . bulk, cost, absence of warm-up time, and ease of component replacement. To take a specific example. the multichannel pulse height analyzers which are used in scintillation spectrometry, as a result of transistorizing. have afforded two or thrce times as many channels in an instruruent of about one third the sizc,. one siuth the w i g h t , a t ahout 60% of the cost of the conventional model. I n addition thrre is little or no warm-up time, and no need VOL. 32, NO. 5, APRIL 1960
0
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for forced ventilation. Component replacement is a matter of removing printed circuit panels, although the latter are not confined to transistorized circuitry. The degree to which data of any kind can be recorded with precision and high speed is limited only to the amount one can spend for equipment. Digital voltmeters reading to five significant figures automatically seek out the range, locate the decimal point, and indicate the polarity. If they present data faster ehan an observer can write them down, they can be fed to a printer, a tape, or punched cards. Counters or E P U T (events per unit time) meters are available which read to eight significant, figures (least count of *l) in which a 100-1Ic. crystal-controlled oscillator of that precision provides the time base. I n simpler fashion, the standard cell is no longer required in instruments. It will, of course, continue to be used &s the international standard of electromot.ive force. K i t h Zener diodes, exact reference potentials can be obtained and selected pairs can be used to attain an essentially negligible temperature coefficient of e.m.f. One prominent manufacturer (Brown) has already replaced standard cells with Zener diodes in its recording potentiometers. An impressive array of converter elements or encoders is available. These include angular deviation encoders, analog to digital converters, and digital to analog converters. Again, when cost is no consideration, such data can be stored indefinitely in meniory devices and when desired can be “devoured” by computers. These can collate the data and subject them to any prearranged form of computation. They can even play with the data and hunt out. the most precise and acceptable sets of constants. I n the author’s opinion there are some curious lacunae in instrument develop nient. Optical pyrometry seems to be in the doldrums as far as new ideas are concerned. With the exception of obvious optical, electrical, and mechanical refinements we do not seem to be very far ahead of Le Chatelier. I n these times when we are studying jets, ionic plasmas, and stellar temperatures it seems silly to peer through a n optical pyrometer. The situation is hopeless if the high temperature phenomenon happens to be of a fugitive or transient nature. There is no lack of experts, so well versed in thermodynamics, the radiation laws, etc., who are available to explain why some new idea will not work and who can prove their point with differential equations. It seems to be an open field for inventors. Inasmuch as almost any process or operation can be automated, there is the possibility that we shall soon run out of things to automate or mechanize. We 64 R
ANALYTICAL CHEMISTRY
may have to scrape the barrel for obscure and second-order phenomena to find something new. There is always the happy prospect that the analyst may again come u p with something at^ useful and simple as paper chromatography in which instruments are unnecessary, but whatever it may be, he will find elegant instruments available if they are required. To a large degree, but not exclusively, the topics discussed here have not been described in the author’s monthly column in this journal. TRANSDUCERS
New transducers are developed from time to time, often as a consequence of some peculiar requirements. A generalpurpose physiological transducer, which is an electrolytic potentiometer (SI), consists of a plastic cylinder closed a t each end by stainless steel plugs. The cylinder contains a slot running the full length, into which the exploring electrode dips. Distilled water is the electrolyte and as much as 100-volt alternating current can be applied across it. Since the resistor is a liquid, the resolution is infinite and the frictional forces are extremely minute. Though small, the damping is an advantage in some applications. Several measuring circuits are described: The electrolytic cell drives a cathode follower as a stable power amplifier; a second electrolytic cell is coupled to a recordmg milliammeter and the latter is used as a ph’asesensitive servomotor to balance changes in the measuring cell; and a transistor amplifier circuit is used for portable equipment. Another transducer, originally designed for measuring isotonic or isometric contractions of heart muscle provides rapid and accurate electrical indication of displacements of the order of 0.1 mm. (29). I n this instrument the motion is communicated to tn-o wires soldered together; the lower portion is of high resistance, the upper of low resistance. Both wires are immersed in mercury pools located in plastic cups. A capillary hole in the bottom of each cup allows the wire to pass through without loss of mercury. I n effect, this device is essentially a straight wire potentiometer in u hich the resistance element moves relative to the contacts rather than the contacts moving on the resistance element. This element is connected as one arm of a Wheatstone bridge. A pen recorder reads the output of the initially balanced bridge and yields a response practically linear with displacement. This is shown to be true over displacements of 0 to 1.6 mv. I n these days the investigator can have almost any kind of data presented to him in digital form, if he can afford the elaboration and expense. The
Jatest addition is a digital barometer manufactured by the Dynametrics Corp., Korthwest Industrial Park, Burlington, Mass. The Model PT 103 digital barometer is a null-balancing electromechanical instrument which provides five-place readings. Pressure applied to either of two reservoirs causes the transfer of a corresponding weight of fluid to the other column. unbalancing the moment beam on which the reservoirs are mounted. An electrical pickup senses this unbalance and signals a servomotor which repositions a poise weight within the beam to restore equihbriuni. The pressure is measured in terms of the position of the calibrated poise weight. The repeatability 1s 0.002 inch of mercury and the resolution is 1 part in 30,000. A variety of other readouts is available. The basic output is a shaft rotation of 10 revolutions per inch of mercury. It is not surprising that a new and automatic measurement of small deviations in periodic structures should emanate from the Bell Telephone Laboratories ( 3 ) . More than 30 years ago Coffi in that laboratory used optical grids as a means of measuring magnet+ striction coefficients, In the present instrument, called the “microdeviometer,” a lens system forms a very sharp magnified image of a moving fine grating in the plane of a second coarse grating which is fixed. The magnification is chosen to make the grating spacing of the image equal to t h a t of the coarse grating; hence movement of the fine grating causes a n intensity modulation of the emergent light beam which may be used to indicate accurately the position of the fine grating. A second optical system forms a sharp image of the front edges of a helix, or other structure to be investigated, in the plane of a narrow fixed slit. The helix moves along on the same platform that carries the fine grating, and the passage of individual turns changes the amount of light passing through the slit. The optical information from both systems is transduced into electrical form by means of photocells, is electrically processed into suitably shaped pulses, and is then fed into specially designed electrical computing equipment. Here the information is combined t o produce a concise cumulative record of departures in individual turns from the positions they would occupy in a perfect helix. This microdeviometer or comparator has a measuring accuracy of 1 micron and with its use measurements nhich formerly required nearly 2 man-days are accomplished in less than 10 minutes. The authors point out several other applications-among them the measurement of uniformity of motion of precision drive mechanisms. I n this case, the mechanism to be studied drives the grating platform, and a series of accu-
rately timed electrical pulses is fed into the computer for comparison. Among optical developments, an oscillating-plate differentiator for spectrophotometry has been described (18). Many spectrophotometric curves are singularly monotonous, whereas their first-derivative presentation may be strikingly informative. Diff erentiation can be achieved in a number of wayselectrically or optically. It can be done in a spectrophotometer by modulating the wave length incident on the spectrophotometer, either by vibration of one of the slits (8) or by oscillation of a beam-deflecting mirror within the monochromator. AIcWilliam has modified this principle in a simple manner, which permits its introduction into an existing instrument with minimum interference with its normal use. As applied to a GrubbParsons S4 infrared monochromator, a transparent rectangular plate of sodium chloride is placed in the optical path of the spectrometer a t normal incidence to the beam. If the plate is oscillated through a small angle, in the vertical plane, it will produce an effective displacement of the slit. The latter is given by As = LA$ ( n
-
l)/n
where the plate of thickness t and refractive index n is rotated through a small angle $. I n the S4 monochromator and using a sodium chloride prism, i t can be shown that a plate 1.0 mm. thick oscillating through 3’ results in an amplitude modulation of about 0.005 micron a t 3 microns. The derivative spectrum illustrated by hlcwilliam shows a remarkable wealth of detail compared with the undifferentiated spectrum. Other aspects of this general problem have been discussed (16, 28). This general method which can be used to obtain first and higher derivatives has been considered in connection with mass spectrometry (1). A recording optical lever of fantastic sensitivity and good stability has been developed (9). I t can detect a change of 10-’0 rad in orientation of a 2-sq. nim. mirror with a response time of about 0.25 second. This performance is largely the result of the production of small cadmium selenide photocells by Schwartz (20). These cells were first applied to optical levers by Thulin (27). The twin photocell used in this work was the Type FT 435 of Hilger and Watts, Ltd. The optical lever system projects an image of a standard optical grid (Ronchi plate) onto the small mirror and brings it into focus, at unit magnification, in the plane of an identical grid. A small-angled prism diverts half of the beam to the lower portion of the twin photocell. The receiving grid, although dimensions are identical to those of the first grid, is
split in half and separated by one grid interval. When the mirror is tilted, the light through one half of the receiving grid is increased and in the other half it is diminished by the same amount. The differential response in the twin-photocell is amplified by a transistor amplifier with an output large enough to operate a recorder. The light source is a MES 408K kryptonfilled bulb rated a t 3.2 watts a t 4 volts. It gives sufficient light to operate the photocell without requiring any special cooling arrangements. The lamp current is stabilized by transistors. Initial adjustment of the grid pattern is accomplished by rotating a small transparent plate in the receiving line. This is done precisely by driving a lever, to which the plate is attached, by a micrometer. To cancel minor image aberrations an identical plate is fixed in the transmitting beam. Several minute effects have been recorded with this instrument. One of these was the expansion of a lithium fluoride crystal under irradiation by x-rays in which the observed expansion was somewhat less than 10-8 cm. When used as a gas refractometer, refractive index changes of 10-7 were measured and it was believed that a change in n of 3 >< 10- could be detected. Finally, in an application to the infrared, a blackened strip of Constantin was shown to expand by 4 x cm., equivalent to the detection of 4 x 10-*0 watt from a black body a t 200’ C. Electro-Optical Instruments, Inc., P. 0. Box 4234, Pasadena, Calif., manufactures a Kerr-Cell shutter. Shutter speeds as fast as 0.1 psec. are provided by a hermetically sealed Kerr-cell shutter which can be synchronized to within 2 mpsec. The cell has an aperture of 1.25 X 2.0 inches and has been designed to mount on a Crown Graphic 45 camera, Flexible leads permit the shutter to be used in a location remote from the modulator unit. The trigger puke can be as low as 50 volts. An adjustable delay can be inserted between the triggering pulse and the shutter opening. Fast light sources find uw in many types of research. A simple source provides pulses of about 10-mpsec. (10” second) duration (19). It consists of 10 cm. of 71-ohm coaxial cable, the spark occurring between the inner conductor of the cable and a brass plate having a central hole of the same diameter (0.14 cm.) as the conductor. The brass plate 0.012 cm. thick is soldered to the shell of the coaxial plug and the electrode separation for the shortest duration is found to be about 0.05 cm. The spark gap is not matched to the cable electrically, but the distant end of the cable is terminated by a IO-megohm resistor and is effectively an open end.
When 1 kv. is applied to the system, the mean spark power is of the order of 1 kw. When running freely at a supply potential of 2 kv., the gap broke down a t irregular intervals with an average repetition rate of l o 4 sparks per second. The peak intensity was of the order of 1 watt and the radiated energy had a spectral range greater than 1900 to 6000 A., the strongest feature being the second positive system of the nitrogen molecule. MULTIPLIER PHOTOTUBES
Multiplier phototubes are widely used in a variety of precise optical instruments. Their more recent use in scintillation spectrometry has gjven rise to an epidemic of papers purporting to show that photomultipliers are quite unreliable and with the strong inference that manufacturers do not know what they are doing. It is therefore stimulating and reassuring to note that some investigators are devising elegant schemes to find out precisely what goes on in a particular tube. The test scheme devised by Draper (4) is an excellent example of what careful inquiry can provide. He uses a single oscilloscope both as a pulsed light source and as a means of analyzing the resultant photomultiplier pulse. A 0.030-inch slit in */,ginch Bakelite was placed against the bare face of the cathode-ray tube of a Tektronix hlodel 517 oscilloscope. This was received by the photomultiplier through a 3-inch Lucite light pipe of a diameter appropriate to the test, and its output was delivered to the vertical deflection plates of the same oscilloscope. The slit ww transverse to and near the left end of the cathode-ray tube sweep trace. A sweep speed of 10 mpsec. per cm. (10” sec. cm.) delivered through the slit a step-function light pulse whose calculated rise time is 1.7 mpsec.-a value larger than the slit width because of the separation of the light source and slit by the thickness of the glass face of the cathode-ray tube. With this instrument various questions can be answered: the rise time of the output current pulse for a stepfunction light pulse; the variation of transit time of cathode electrons from various regions of the photocathode and its dependence on the dynode voltage distribution of the tube in question; the magnitude of an output pulse for a standard light pulse; the magnitude of a saturated output pulse; the nature of the transition region between linearity and saturation; the uniformity of the photocathode efficiency for areas of illumination as small as 1 sq. mm.; and the absolute transit time of electrons from photocathode to collector and its variation with dynode voltages. Systematic examinations of this kind would seem to be preferable VOL. 32, NO. 5, APRIL 1960
65 R
to making perfunctory tests and scolding the manufacturer. -4 self-balancing differential refractometer ( I ? ) uses a Claesson split cell, bhe 5461 line of a mercury arc isolated with a band-pass interference filter. The beam is focused on tn-o phototubes. A servodriven feedscrew automatically repositions photot'ubes for condition of equal illumination. For a motion of 1 inch of phototubes, An = 0,0175 R.I. The long light path is minimized by reflection from two front surface mirrors a t 90". The motion of the head screw is read out by a counter (1 count per revolution), a dial reads l/lm revolution, and a vernier dial reads l/lwa. Repeatability is i l count or 1 2 . 4 1 4 x 10 7 R. I. Incremental differences of reliability are 1 2 . 5 x 10-7 in refractive index. Mullaney (15) has determined flame temperatures by x-ray absorpt,ion using a radioactive source. The flame consisted of propane-osygcn and argon. The latter was necessary to get sufficient x-ray absorption. Source w a s iroii-55 which emits hInKa x-ray by electron capture. It was tested over a range of 500' t o 2500" K. Both extended and line source of radiation vas used. the latter t o get tempwature profiles. A simple method for preparing electron-permeable windom for cathode-ray tubes (21) consists of evaporating a sodium bentonite gel in aqueous solution on a n SO-mesh nickel screen and siibsequent'ly baking the film a t 350' C. A gas-tight !Tindon- some i o pinches thick can he prepared. which will withstand a prcesurc differmtial greater than 1 atm. (breaking prcsure is about 2 at'ni.) and is inscnsitivi. t o temperatures up tu 400" C. It is pi.rmeahlc~to electrons of energy as l o a as 15 kv. Ihtirely too little attention is biing given to optical pyrometry in vicn. of the great interest in very high tempcratures and the peculiar requircmerits which may arise such as short-tcrni measurements, hazardous conditions, anti fatigue of operators, hi intereating development. is the re,cording optical pyrometer described by Bium ( 2 ) . This instrument measures the brightncss temperature at 0.65 micron of a m a l l incandescent sample in the range of 1300' to above 3000' C. with a time constant of a few milliseconds. It was designed to be used in studies of materials exposed to the plasma jet of a high-intensity electric arc. It is reliable to +20° C. at these temperatures, but by careful calibration against s standard lamp this can be increased to + l o 3 C. A high vacuum phototube is used rather than a photomultiplier because a fast optical system consisting of a 7-inch f/2.5 .4ero Ektar lens makes up for the less sensitive but simpler detector. It n-ould be interesting to know how many important high temperature in-
66 R
ANALYTICAL CHEMISTRY
vestigations are being hampered by the lack of more research in better pyrometers. With the exception of this particular development, high temperature pyrometry seems to be in a moribund state. Automatic scanners for chromatograms are invented semiannually. usually with little reference to prior art or the fact that several good scannerJ are commercially available. Of the 1959 vintage an elaborate system has been described by Smiljani6 and Rabuzin (62), n hich will scan electrophoresis and chromatography paper strips or isotope-labeled chromatograms. In the photometric scheme the well knon n Sneet circuit (23, 24) proiidcs logarithmic output and a final output stage opcratcs a s a Jliiler integrator. I n the radioactivity measurements on labeled chromatograms a count-rate meter is u v d , the output of which can be rec o r d d . For inttgration part of thc counting is connected tlirough a diodc piin?p which ehargcs a rapacitor the voltage across n hich is proportional to the total number of pulses d n acoustic gas analyzcr described hl- Molyrmix ( 2 3 , i q capahlc of ineawring the ronccntration of halothanc ihromochiorotrifluoroethane) or chloroforni in an air and oxygen atnioydiere over the range of 0 to 4 5 by volume with an accuracy to =0.2.57,. This instrument compares the time taken hy a nulse of sound to travel through the original gas sample n ith the time takcn for another pulse to t r a w l through thc snmr sample after fhc reniowil of the vapor by activated charco:il. The soiind transduccw nrc magnetic c'ar piece ccmcvitccl t o 1)raqq collars which are in turn cementcd t o g1a.s fiihcs. The circuit1 I$ entireiry tranristonzed. Thp sound pulse gmerator 15 an asymmetrical multivibrator producing 70 eltvdrical pulsts ptxr s(v.miri nhich are coriverted into qound p u l w by the transducers. The output from the reccircr transducers is amplified. limited, and differentiated to piotiiice uniform trigger pulscs I n both chaiiIic1' the original triggers initiate rectangular forni pulres. Tn the sample channel, the trailing edgr of the rcctangular pulse is differentiated and used to terminate the rectangular pulqe in the reference channrl Hrnw the rectangular pulses in rach rhannrl begin a t a time d&mi:incd by the arrival of the acoustic pulsci: in the appropriate tube. but finish virtually at thc snmc time. As thc rectangular pulses of the two channcls are of opposite polarity, a train of pulqm the nidth of which is proportional to the differencr betmeen the transit time of a pulse in a reference tube and the transit time of a pulse in the same tube, and the polarity of which changes with tho sense of the ,)htaincd by time diffcrencp, ma\ 1 x 3
subtraction. The average current of the resultant pulse train is aIso proport.ional to the difference in transit times, and, after amplificat,ion, is used to operate a robust microammeter. I n listing references t o nine other sonic methods the author states t h a t t'hey have used most of the methods of making sound velocity measurements, n-ith the exception of the oldest', and in principle, simplest method of all, that of measuring the time that an impulse takes to travel a certain distance. -4n electronic alternating current mutual inductance bridge for measuring susccptibilities a t liquid helium temperature has been described (18) in which a vacuum tube and a fixed mutual inductance are combined t o form a n accurately variahle mut,ual inductance. The variat'ion is obtained hy means of decade resistors. The suxeptibilities of samples 1 ce. in volunif can be measured at, low temperatures with B precision of r 2 >( 10-7 emu pcr cc. The rmults are in excellent agrecnieiit n-ith t'he more cumbersome but accepted Gouy nirthod. The falling-ball viscometer is an old principle and ninny electronic schemes hai-c b e e n di..i.eloped for automatically nipnuring t,he t r a w i t time between two pickup coils, as the metallic sphere sinks through the viscous liquid (6, 6). Ficileris and JVhtmore have revived the principle and improved the sharpuess of the signal. Instead of using a single coil through which the ball passes, they use two secondary coils in series opposition surrounded by a primary coil much in the manner of B linear differential transfornier. When properly aligned, the signals induced i n the BITondaries by the primary coil are eompletely cancelled. As the failiiig ball t w t e n the composite coil. its prtwnce iri the first secondary causes a largc unbalance and an envelope of alternating current signal. Tllis envelope coilap ball reaches n point exactly midway between the secondaries, only to rise again as the ball enters the next weondary coil. It is very easy t o establish the time a t which zero signal occurs between the two signal envelopes. An identical coil system located a t a precisely known distance from the first coil system establishes the time of arrivni. For slowly idling spheres t h timing w-as carried out with a stop watch and for rapidly falling spheres. the signals were phobgraphecl from a double-beam cathode-ray oscilloscope. one channel of which presented a mierenee time-bsse. Ln all cases, the primary coils were excited by a variable frequency oscillator and the output signals from the timing coils were fed to a bridge heterod-yne detector and presented on a n oscilloscope. The authors succeeded in obtaining consistent results for metallic and
metal-coated spheres in diameters from 0.079 to 2.00 cm. falling with velocities from 0.1 to 200 cm. per second through pure fluids and aqueous suspensions. Similar work related to this problem is quoted by the authors (7, 10, 11, 14, 25, $6). An interesting phenomenon and one of great importance is the demonstration (SO) that organic films placed in the molecular ion beam of a mass spectrometer can cause complete dissociation of the ions into their atomic constituents. According to the authors, “the film which acts as a strong force field a t a discrete point in the beam trajectory, causes uncorrelated forces to act on the constituent atoms of the molecules. The atomic groups comprising the original incident molecule are then analyzed by an electromagnetic and electrostatic lens, both having a W i n c h radius of curvature. Mass, charge, and energy of each of the atomic groups is easily determined. This technique provides the possibility of achieving
pure atomic spectra in mass spectrometry.” LITERATURE CITED
(1) Beynon, J. H., Clough, S., Williams, A. E., J. sei. rnstr. 35,164 (1958). (2) Blum, N. A,.’ Rev. Sn’. Instr. 30. . 251 (1959). (3) Closson, H. T., Danielson, W. E., Nielsen, R. J., IbG., 29, 855 (1958). (4) Draper, J. E., Ibad., 29, 179 (1958). (5) Fidleris, V., m t m o r e , R. L., In-
stitute of Fuel Conference, “Science in the Use of Coal,” Sheffield, April
1958. (6) Fidleris, V., Whitmore, R. L., J. Sci. Instr. 36, 35 (1959). (7) Franklin, P. J., Mech. Eng. 69, 928 (19471. -.
.--
I -
(8) French, C. S., Church, A. B., Annual Report, Carnegie Institution of Washington, p. 162, 1954-5. (9) Jones, R. V., Richards, J. C. S., J.Sn’. Instr. 36,90 (1959). (10) Klassen, V. I., Shchurkin, N. A., Gornya Zhur 4, 44 (1956). (11) Lamson, H. W., Rev. Sci.Znstr. 9, 272 (1938). (12) McWilliam, I. G., J. Sci. Instr. 36, - 5’1 (1959). . (13) Molyneux, L., Zbid., 36, 118 (1959). (14) Moore, L. P., Cuthbertson, A. C.,
I N D . ERG. CHEW, AXAL.ED. 2, 419 (1930). (15) hfullaney, G. J., Rev. Sci. Instr. 29, 87 (1958). (16) Oberley, J. J., Ibid., 24, 125 (1953). (17) Penther, C. J., Noller, G. W., Ibid., 29, 43 (1958). (18) Pillinger, W. L., Jastram, P. S., Daunt, J. G., Ibid., 29, 159 (1958). (19) Porter, G., Woodring, E. R., J. Sci. In&. 36, 147 (1959). (20) Schwartz, E., Proc. Phys. Soc. (London) B64,821 (1951). (21) Seehof, J., Smithberg, S., Armstrong, M., Rev. Sci. Instr. 29, 776 (1958). (22) SmiljaniC., G., Rabuzin, T., J. Sci. In& , in press. (23) Sweet. hl. H.. Electronics 19, 105 ’ (1946). ’ (24) Sweet, M. H., J . Opt. SOC.Am. 37, 432 (1947). (25) Symmes, E. M., Lanta, E. A., ISD. ESG. CIIEM.,ANAL.ED. 1, 35 (1929). (26) Thompson, A. M., J. Sei. Instr. 26, 75 (1948). (27) Thulin, A., Ibid., 32,387 (1955). (28) Walsh, A., J. Opt. SOC.Am. 42, 94 (1952). (29) Whalen, W. J., Weddle, O., Rcu. SCZ.Instr. 29, 144 (1958). (30) White, F. A., Rourke, F. M., Sheffield, J. C., Ibid., 29, 182 (1958). (31) Whittlestone. W. G.. J. Sci. Instr. ‘ 36, 8 (1959). ’
Review of Fundamental Developments in Analysis
Ion Exchange Robed Kunin Rohrn & Haas Co., Philadelphia, Pa.
T
BE use of ion exchange techniques throughout the field of analytical chkmistry has become so widespread that considerable selectivity must now be exercised during the preparation of a review of this nature. Little attention has therefore. been drawn to those areas in which ion exchange is being used routinely in chemical analyses. In addition, the areas of the published literature on ion exchange pertaining to general theory and separations not of analytical interest were omitted since these are now well covered annually in
Industrial a d Eagineering Chemistry (Unit Operations Review) and in Rm’ews of Physical Chemistry. The past 2 years have witnessed the standardization of several ion exchange methods and of ion exchange materials suitable for use in analytical operations. For example, instiuments and standardized ion exchange resins are now commercially available for routinely separating a mixture of amino acids by ion exchange chromatography. The field of paper chromatography has been broad-
ened with the recent availability of ion exchange chromatographic paper. There is little doubt that ion exchange techniques are now widely employed throughout the analytical world aa a separation tool. REVIEWS
Of generd interest to the analytical chemist are the books on ion exchange by Kitchener (SA), Kunin (6A), and Salmon and Hale (7A). Kraus has written a chapter in a book edited by Yoe and Koch (4A) reviewing the use of ion exchange and its application to trace analyses. Edge and others (1A) have also reviewed this topic of trace analyses. A more general review of the analytical applications of ion exchange has been written by Kunin @A). Of special interest t o the analytical chemist involved in the use of ion exchange materials will be the chapter written by Fisher and Kunin (2A) on the analysis of ion exchange materials.
INORGANIC SEPARATIONS
Ion exchange has been employed for the analytical separation of practically all of the inorganic ionic species. Oehlmann and Heimer (74B), Gabrielson (sell), and Reichen ( Z B ) have been able to employ such techniques for the analysis of the alkali metals. The alkaline earths and other divalent ions have been analytically separated. Knappe and Bockel (66B) have studied calcium and Power and others (76B) h+ve separated radium and barium. G k h a m (S8B) and Bryant and othen (20B)have developed ion exchange procedures for determining strontium-90. Berg and Truemper (97B) and Kallmann and others (6dB) have separated zinc and cadmium. The snalysis of zirconium by means of an anion exchanger haa been described by KO (67B) and Korkisch and Farag (69B, COB). Hoshino (@B) and Belyavskaya and others (9B, 10B) describe the use of mtion exchangers for the separation of eirconium and hafnium and for the separation of zirconium and VOL. 32, NO. 5, APRk 3960
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