Topics in..
. Chemical Instrumentation
Edited by
S. Z. LEWIN, N e w Y o r k University, N e w Y o r k 3, N . Y,
These articles, mosl of which are lo be contributed by guest authors, are intended to serve the readers of this JOURNAL by calling allenlion to new developments in the theory, design, or availability of chemical laboralory inslnrmentation, oi by presenLing useful insights and explanalions of topics Iha( are of practical importance to hose who use, ,or teach !he use of, modern instmmentalion and instlumenla1 techniques.
VI. Differential Thermal Analysis Soul Gordon, Department o f Chemistry, Fairleigh Dickinson University \Vhen snhjected to suffir:iently high temperstures, virtually all snl~stanceswill undergo physirnl and chemical changes ranging inun simple changes in state to complete deeompc,sition that can he st,udied hy the various methods of t,hermoa n : ~ l ~ s i s I. h r i n g the course of these physicor.hcmirnl rcartions or phenomena, there will lie ctone DTA opporotur.
adjustable gain ranging from 5 t o 4000 p , or with the standard Pt-Pt, IOy0 R h thermocouple, a full-scale differential temperature of 0.5 t o 350°C. With the two-pen recorder and a n addit,ional amplifier, two samples may be run conr:urrent.ly, or the second recording channel may 1)e
used for simultaneous DTA-EGA with the npprupriate sample holder assembly, a hot,-wire gas thermal conductivity cell and a power supply assernhl?-. The power supply is also xvailahle in camhination with a rerortler t o complete the operat,innal (Continued on page A112)
Chemical Instrumentation assembly shown in Figure 12. A new thprmobalsnee is available for thermugmvimetric evaluations that may be used with either a ~ e p a r a t econtrol system or t,lrr 1ITA rerorder-controller assembly.
Technical Equipment Corp. The Deltatherm ($5875), manufactured l y Technical Equipment C o p in Denver, Colorado, is a console mounted DTA apparatus, Figure 13. This instrument incorporates a temperature programing system and four-channel dry stylus elect,rosensit,ive paper recorder, with twin furnace positions and interchangeable mult,i-sample plug-in blocks having gold plst,ed thermocouple connecting plugs and print,ed cirruik for the interconnecting
thermocouples, Figure 14. A peries of metal and ccrnmir i h e k s are avsilahle for
pressure, vscuum, and dynamic gas atmosphere studies with nine wells t o accommodate four sample-inert reference p;iirs and one for the control thermocouple. The basic unit is equipped for a fixed heating rate of 1O0C per minute hut may be replaced with a n optional ratecontrol unit for more closely controlled heating rates of 2 t o 20'C per minute t h a t are obtained with interehangenhle
Figure 13.
Technical Equipment Carp.
Delto-
lherm.
gears. A groull of six plug-in stable dc amplifiers with lvinted circuitry and trsn~istorised ~ n l i d state choppers are used for the four sample-reference differential temperature channels, the temperature indicator t h a t also provides s series of solid calibration lines acravs t,he chart
(Continued on page 4114)
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A multi-purpose meter is proChemical ln~ff~menfflfiontiometer. .id,, for ~ d ~ c t ~ ~ - ~read-out w i t c h of line
investigators who have constructed or assembled their own apparatus, many of
I Figure 15.
Figure 14. Multiple mmple holder with printed circuitry and plug-in module conrtrvction "red in Deltatherm.
t ~ 50'C t intervals, and in the rate control t,emprsture programer, Figure 15. The sensit,ivit,y of 25 pv per inch (O.tioC/in.) may lx used over the full 12 in. width of the r e a d o r with overlap of d l four traces. Any of four fined levels of st,ep attenuation mny Ile chosen to minimize or eliminate this werlap. The reference well temperat,ure is constantly dipplayed for visual pmel monitoring on a. printed tape poten-
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Block diagram showing operotion of the Deltatherm DTA opporotw.
voltage, furnace current, o r recorder chart. posit,ion for each of the four DTA traces. The use of two furnaces, and a n optional third furnace t h a t can he operated externally to the apparatus, allows for virtually continuous operation of the instrument. A companion thermohnlxnre has been developed for complementary therrnogravimetric studies.
Summary Although the major contributions involving DTA studies have been made hy
which are described in the following references, i t is obvious that t,hey did so because well designed instrument pnrkxges were not eommereially available. This situat,ion hns now been greatly alleviated hy several rompanies, as previously deserihed. Kevertheless, those wit,l~limited equipment hudgets should find many usehd suggestions for instromentzdion and experiments in the references cikd below. This survey of DTA instruments has been restricted t o instmment,s that are domestieally mnnufnctured ( C o n t i n d on page A116)
Chemical Instrumentation because their foreign counterparts are not readily availshle at this time.
References
ARSENEAU, D. F., "DTA Apparatus," J. CHEM.ED., 35,130 (1958). BORCHARDT, H. J., "DTA. Anexperiment for the Physical Chemistry Laboratory," J. CHEM.ED.,33,103 (1956). CAMPBELL, C., GORDON, S., AND SMITH, C. L., "Derivative Thermoanalytical Techniques. Instrument,ation and Applications to Thermogravimetry and DTA.," Anal. Chem., 31,1188 (1959). CHIU, JEN,"Identification of Organic Compounds by DTA," Anal. Chem., 34, 1841 (1962). GARN,P. D. AND KEBSLER,J . E., "Effluence Analysis as an Aid to Thermal Analysis," Anal. Chem.,33,1247 (1961). GORDON, S., "Thermoanalyai~," McGrawHill, "Encyclopedia of Science & Technology," 13,5569 (1960). C., "ThermoGORDON S. A N D CAMPBELL, analytical Techniques. Their Importance in the Instrumental Methods Laboratory,'' Abstracts of Papers, 131st meeting, A.C.S., April 1957. C., "AutoGORDON, S. AND CAMPBELL, matic and Recording Balances," Anal. Chem., Review Issue, 32,271R (1960). C., "DifferGORDON, S. A N D CAMPBELL, ential Thermal Analysis,"in "Handbook of Analytical Chemistry," McGrawHill Book Co., New York, 1963, Sec. 8 Thermoanalytical Techniques. HENDRICKS, S. B., GOLDICA,8. S., AND NELSON,R. A,, "A Portable DTA Unit for Bauxite Exploration," Eeon. Geol., 41,64 (1946). KE, B., "Application of DTA to High Polymers," in Mitchell, J. Jr., el al., "Organic .4ndysis," Val. 4, Interscience Publishers, New York, 1960,361-93. LETDIN, S. Z. "Thermobalances," J. CHEW ED., 39, A575 (1962). I,., "High L o n o r ~ c ,W. A N D HAMMELL, Temperature Pressure-Vacuum Furnace," Reu. Sci. Inslm., 30,885 (1959). W. AND HAMMELL, L., "DTA LODDIN@, of Hydroxides in Reducing Atmosphere," Anal. Chem.,32,657 (1960). MACKENZIE,R. C. (ed.), "The Differential Thermal Investigation of Clays," Mineralogical Society, London, 1957. MACKENZIE,R. C., "Scifax DTA Data Index (punched cards)," CleaverHume Press, Ltd., London, 1962. B. D., MACKENZIE, R. C. AND MITCHELL, "DTA. A Review," The Analyst, 87, 420 (1962). MURPHY, C. B., "DTA. Review of Fundamental Developments," Anal. Chem., Annual Reviews, 30, 867 (1958); 32,168R (1960); 34,298 (1962). . "DTA. SMOTHERS. W. J. AND C n m ~ sY.. Theory 'and Practice," Chemi&l Publishing Co., 1958. STONE,R. L., "DTA by the Dynamic Gas Technique," Anal. Chem., 32, 1582. WENDLANDT, W. W., "An Inexpensive DTA Appartratus," J.CHEM.ED.,37, 94. WENI>LANDT, W. W., "Reaction Kinetics by DTA. A Physical Chemistry Experiment,," J . CHEM.ED., 38,571 (1961).
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