(250) Plankert. M.. Gas-Wasserfach. 113, 65 11977) (251) Pochinok, K. N., Fiz. Biokhim. Kul’l. Rast., 4,101 (1972). 1 Potman. W.. Dahmen. E. A. M. F.. Mikro, 2521 , chim. Acta. 1972,303. (253) Pottkamp. F., Umland, F.. Fresenius’ Z. Anal. Chem., 255,367(1971). (254)Quenum. B.-M.. Grandaud, J -L., Berticat, P., Vallet, G., Chim. Anal., 53, 629 (1971) (255)Rains, T. C.. Menis, O.,J. Ass. Offic. Anal. Chem.. 55,1339 (1972). (256)Ratcliffe, D . B., Cunningharn. A. T. S., Fuel. London. 50,23 (1971). (257) Reeves, R. D , Molnar, C. J . , Glenn, M. I . -
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T., Ahlstrom. J. R.. Winefordner, J. D . , Anal. Chem.. 44,2205 (1972) (258)Reverchon, R . , Bull. SOC.Chim. F r . , 1972, 829. (259)Rittner, R. C., Ma, T. S., Mikrochim. Acta, 1972,404. (260) Roemer. F. G.. van Osch, G. W. S., Griepink, B. F. A., ibid.. 1971,772. (261) Roemer, F. G., van Osch, G. W. S.. Buis, W . J . , Griepink. B. F. A., ibid., 1972,674. (262)Rohm. T. J . . Nipper, H. C., Purdy, W. C., Anal. Chem.. 44,869 (1972). (263) Rook, H . L., i b i d , p 1276. (264)Roschnik, R . K.. J. Dairy Sci.. 55, 750 (1972) (265)Rost. G , Hofmann, C.. Schmidt, L., Schwarze, H..Zentralbl. Pharm Pharmakother. Lab.-Diagnostik, 111, 391 (1972) (266)Rottschafer. J. M.. Jones, J. D , Mark, H. B.. J r . , Enwron. Sci. Technol, 5, 336 (1971) (267)Ruf, H . . Rohde, H., Fresenius’ Z. Anal Chem.. 263,116 (1973). (268)Saha. J. G., Lee, Y . W., Bull. Environ. Contam Toxic 7,301 (1972) (269)Sakla. A B.. Bishara, S . W., Abo-Taleb, S. A,, Microchem. J.. 17,436 (1972). (270)Saran. J.. Khanna, P. N., Banerji, S., Mic r o c h m Acta. 1972,252. (271)Savory. J , Glenn. M. T.. Ahlstrom, J. A,, J. Chromatogr. Sci.. IO, 247 (1972). (272)Schaller. K.-H., Strasser, P., Woitowitz, R . . Szadkowski. D.. Fresenius‘ Z. Ana;. C h e m , 256,123 (1971). (273)Scheidl. F , Toome, V.. Microchem. J.. 18,
42 (1973). (274)Schiller, P., Cook, G. B., Kitzinger, A , , Woelfl. E , Analyst (London). 97, 601 (1972). (275)Schulte. K. E.. Henke, G . , Tjan. K. S.. Fresenius‘ Z. Anal. Chem., 252, 358 (1970). (276) Schwedt, G., Ruessei, H. A,, Chromatographia. 5,242 (1972). (277)Scroggins, L. H., J . Ass. Offic. Anal. Chem.. 54,808 (1971). (278) l b i d , 55,676 (1972). (279)Seis, F.. Demoen. P.. Microchem. J . , 18, 107 (19731. (280)Sheppard G , Marlow. C. G lnt J ADD/ , . Radiat Isotopes. 22,125 (1971). (281)Shimizu, M , Hozurni, K., Jap. Anal., 20, 267 (1971)
(282)Simmons, W. J., Anal. Chem., 45, 1947 (312)Toma, 0.. Crisan, T., Chim. Anal., 2, 25 (1973). (1972). (283)Sinko. I . , Gomiscek. S., Mikrochim. Acta, (313) Tong, S.C.. Gutenmann, W. H., St. John, 1972,163. L. E. Jr., Lisk, D. J . . Anal. Chem., 44, (284)Skare. I., Analyst (London), 97, 148 1069 (1972) (1972). (314)Tonkovic, M.. Mesaric, S., Croat. Chem. (285)Skorobogatova, V. I., Kravchenko. G. A,, Acta, 43,119 (1971). Faershtein, Y. M., J. Anal. Chem., USSR, (315)Toralballa. G. C., Spielholtz, G. I., 26,1967 (1971). Steinberg, R . J., Mikrochim. Acta, 1972, 484. (286) Slanina. J., Vermeer. P., Agterdenbos. J.. Griepink, B.. Mikrochim. Acta, 1973,607. (316)Trutnovsky, H., ibid., 1971,909. (287)Smith, A. J.. Myers, G. Jr.. Shaner, W. C. (317) Trutnovsky. H., Sakla, A. B.. Anal. Chim. Jr., ibid., 1972,217. Acta, 59,285 (1972). (288)Srivastava, 0.P., Mann. G. S., Lab. (318)Turunen. J . , Visapaa. A,. Pap. Puu, 54,59 Pract., 20,721 (1971). (1972). (289) Ssekaalo, H., Analyst (London), 96, 346 (319)Ubik, K.. Microchem. J., 17,556 (1972). (1971). (320)Ibid., 18,29 (1973). (290)Steyermark, A., Lalancette, R. A,, Contre- (321)Ubik, K., Horacek, J., Pechanec, V.. Colras, E. M., J. Ass. Offic. Anal. Chem., 55, lect. Czech. Chem. Commun, 37, 102 680 (1972). 11972) (291) Stoffel, R., Fresenius’ Z. Anal. Chem., (322)Clthe, J. F., Solomon. J., Grift, B., J. Ass. 262,266 (1972). Otfic. Anal. Chem., 55,583 (1972). (323) (292) Stoffel, R . . Mikrochim. Acta, 1972,242. . , Vladimirova. V. M.. Fedoseev. P. N.. Zavod. Lab., 39,8 (1973). (293)Strukova, M. P., Kashiricheva. I . I . , Abdulina, R. G., Kalashnikova, L. K . , Zh. Anal. (324)Volodina, M. A,, Moroz. N . S..Zh. Anal. Khim., 25,1198 (1970). Khim., 26,187 (1971). (294)Strukova, M . P., Lapshova, A. A,. Luk’y- (325)Volodina, M . A.. Pivovarova. A. A , , ibid., anov, V. F., Korobova, N. V.. Uchen. Zap. 27,568 (1972). Mosk. Inst. Tonkoi Khim. Tekhnol.. 1, 47 (326)Volodina. M. A.. Martynova. G. A,. ibid., (1970). 26,1002 (1971). (295)Svajgl, 0.. Chem. Prum., 21,103 (1971). (327)Volodina, M. A., Martynova, G. A,, Zavod. Lab.. 37,285 (1971). (296)Sympson, R. F.. Anal. Chim. Acta. 61,148 (328)Volodina, M. A., Moroz, N. S., Kiseleva. (1972). V. I., Zh. Anal. Khim., 27,1639 (1972). (297)Synek, L.. Vecera, M., Kratochvil, V., Collect. Czech. Chem. Commun.. 36, 2606 (329)Volodina. M. A.. Terent’ev. A. P., Besada, 11-9711 A . , ibid., 25,1017 (1970). (298)Talbott, T. D., Cavagnol, J. C., Smead, C. (330)Ibid., p 1019. F.. Evans, R. T., J. Agr. Food Chem.. 20, (331)Vrignaud, M. C.. Vrignaud, N., Blanquet. M. P., Bull. SOC. Pharm. Bordeaux, 110. 959 11972). , , 83 (1971). (299)Taylor, M. L., Arnold, E. L., Anal. Chem , (332) Ibid., p 138. 43,1328 (1971). (300)Terent’ev, A. P., Bondarevskaya, E. A,, (333)Warwick, M. A , Microchem. J . , 17, 160 11972). Gradskova, N . A,, Zh. Anal. Khim., 26, (334)Wasserrnan T I Basch. A , Israel J 1838 (1971). Chem 10,979(1972) (301)Terent’ev, A. P., Bondarevskaya, E. A.. Kirillova, T V . . PotseDkina, R . N.. ibid., (335)Weaver, J N , Anal C h e m , 45, 1950 (1973). 25,2208 (1970). (302)Terent’ev. A . P., Gradskova, N. A , , (336)Webber, M . D., Can. J. Soil Sci., 52,282 \
. I .
Bondarevskaya. E. A., Potsepkina, R . N., Kuieshova, 0. D . . ibid. 26,1850 (1971). Terent’eva, E. A,. Fedorova, M. V., Smirnova, N. N., Malolina. T. M., ibid.. 27,
1598 (1972). Terry, M . B., Kasler. F , Mikrochim. Acta.
1971,569. Thomas, A. C., Robinson, C. D., ibid.. p 1. Thomas, J.-P., Schweikert, E. A , Nucl. Instrum. Meth.. 99,461 (1972). Thomas, R. J., Hagstrom, R. A,, Kuchar, E.J., Anal Chem.. 44,512 (1972). Thorpe, V., J . Ass. Offic. Anal. Chem., 54,
206 (1971).
(1 Y IZ). Welch, R. M., Allaway, W. H.. Anal. Chem., 44,1644 (1972). Wernberg, 0.. Lamm. C. G., Nielsen, T., J. Chromatogr. Sci., 9,373 (1971) Wilkinson, B. W.. Toth-Alien, J.. Nucl. Technol., 13,103 (1972). Wojciechowska, B., Chem. Anal. (Warsaw), 16,135 (1971). Wojnowski. W.. Olszewska-Borkowska. A,. Fresenius’ Z. Anal. Chem., 262, 353
(1972). Yeager. D . W.. Cholak, J., Henderson, E. W., Environ. Sci. Technol.. 5, 1020
(1971).
Thuerauf, W., Assenmacher, H . , Mikro- (343)Zak, B . , Baginski, E. S.. Epstein, E.. chim. Acta. 1971,100. Weiner. L. M., Clin. Toxicol.. 4, 621 (1971). Thuerauf, W., Assenmacher, H., Fresenius’ Z. Anal. Chem., 262,263 (1972). (344)Zawadzka, T., Sokolowska. R., Rocz. Pansf. Zakl. Hig., 22,161 (1971). Tiwari, P. N.. Bergman, R., Larsson, B . , Int. J . AppI. Radiat. Isotopes, 22, 587 (345) Zuber, R . , Mitt. Geb. Lebensmitteiunters. Hyg., 63,229 (1972). (1971).
Thermal Analysis C. B. Murphy Xerox Corporation. Rochester, N. Y . 74644
This review covers the major trends in thermal analysis from the previous review (169) to October 1973. During this period. a new journal, Thermal Analysis Abstracts, edited by J. P. Redfern, has made its appearance. Its comprehensive keyword indexing system should make literature searching easy. Several books have appeared, including “Differential Thermal Analysis, Vol. 2, Applications” (134): “Atlas of Thermoanalytical Curves” (126),
based on results obtained with the Derivatograph; a revision of Schultze’s “Differential Thermal Analysis” (201); and “Thermogravimetry: Critical and Theoretical Study, Utilization, Principal Uses (227). A chapter, Thermal Methods, appeared in “Physical Methods in Macromolecular Chemistry” (138). The review of the analysis of high polymers (161) continues to provide excellent coverage of thermal methods.
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The philosophy and procedure adopted by the Nomenclature Committee of the International Confederation for Thermal Analysis (ICTA) has been given (135), and two reports have appeared relative to nomenclature in thermal analysis. The first pertained to differential thermal analysis (DTA) and thermogravimetric analysis (TG) apparatus, technique, and curves (136), and the second pertains to evolved gas techniques (150). Adoption of the practices recommended in these and in the preceeding publications (133, 149) would improve the reporting of data and evolve a uniform terminology for the field.
DIFFERENTIAL THERMAL ANALYSIS-DIFFERENTIAL SCANNING CALORIMETRY (DSC) Incorporation of a five element thermopile (181) has improved the sensitivity of DTA detection. Design considerations for the DSC-1B have been described (173) and its application to metal and inorganic systems demonstrated. The use of thermocouples as sample holders (2, 184) has been shown. A system has been described (63) for applying dynamic water vapor a t controllable pressures to the Lodding-Hammell (127) sample holder and apparatus for this purpose has been applied to decomposition of alkali metal-copper sulfates (218). Equipment for the study of molten fluoride systems has been constructed (88) and applied to phase equilibria and calorimetric measurements. A DSC-type equipment has been described (83) which employs heat pulses for precision calorimetry. Low-temperature DTA was surveyed (186), and equipment was developed (148) for operation from -196" to 500°, in which cooling is effected by controlled liquid N2 flow in a sample holder well. Referenceless D by thermal gradient measurement has been reported again (152), showing application to low temperatwe transitions in Hg, U, and Cr, with the last showing a thermal effect due to strain. Automated DTA and thermogravimetric (TG) equipment were reviewed (237). Influences of sample treatment continue to be investigated. Grinding of Mg(OH)2 in air was shown ( 3 ) to produce DTA peaks corresponding to the M basic carbonate, while in vacuum, MgO was produced. T%e kinetics of the massicot to litharge transformation during dry grinding was investigated (124). Several systems were explored (125) to show lattice distortion, amorphorization, polymorphic transformation, and chemical transformation can occur during dry grinding. Sample treatment has been explored to effect changes resulting in more definitive analyses. Bauxite can be analyzed by DTA after acetylacetone extraction of some of the components (91); oxidation of samples a t 400" has permitted more meaningful analyses of chlorite curves (11);and reaction DTA, where a specific component is reacted with a reagent to form a specific product (specific peak), was shown (14) to provide more ready identification of materials. Low-temperature calcination has been proposed (140) to suppress interference due to oxidizable organic materials in the characterization of carbonates. Quantification of DTA and DSC data depends on the interpretation of the thermograms. DSC normally consists of measurement of the power input required to keep the sample and reference a t the same temperature. Thus, the total DSC peak is associated with the enthalpy of transition. On the other hand, the DTA peak is a plot of the temperature difference between the sample and the reference. In endothermic transformation, the sample embedded thermocouple is retarded until termination of reaction, the peak apex, and, thus, only the area to the peak apex is related to enthalpy. This has been demonstrated by comparison of theoretical and actual heating and DTA curves (21). The thermogram beyond the peak apex is related to the specific heat of the sample, sample holder, etc. Such considerations could explain differences in peak areas obtained by heating and cooling (137), i e . , specific heat being measured of different forms, as well as a function of temperature. Quantitative DTA has been conducted a t constant heating rate, with respective peak areas giving the ratio of materials undergoing reaction. I t is assumed, but not yet demonstrated, that the nonresponsive peak area a t a fixed 452R
heating rate is a constant fraction of the total area. Thus, it can be compensated for by the constant K in the expression AH.M = KA, where AH is the heat of reaction, M is the weight of the sample, and A is the peak area. In DSC, the heating rate dependence does not exist. Using the DTA peak area from peak onset to apex, with appropriate calibration techniques (21, 181) would give quantitative data without dependence on heating rate. Quantitative work is dependent upon establishment of a thermogram base line to measure the appropriate area. The Standardization Committee of the ICTA (151) has recommended for DTA the use of the straight line obtained by connecting the points resulting from the intercept of straight lines extending the base line and adjacent peak legs. In the case of DSC, it has been pointed out that equipment is becoming more precise (76), imparting greater significance to the correct drawing of the base line, and a more precise, corrective technique for area measurement was evolved. Evaluation of DSC heats of fusion has been considered (73), accounting for base-line shift with heat capacity changes on melting and the time constant of the equipment. An elegant tape playback procedure has been devised for use with DSC (233) where a slowly changing signal has a marked effect on the base line. When this procedure was applied to zeolite dehydration, it gave results in excellent agreement with those obtained with a Calvet differential calorimeter. Heats of transition of the ICTA-NBS DTA standards were determined (137) with reasonably good agreement with literature values, except for Ag2S04. In this case, the 430" transition gave a value of 4.2 kcal/mole, as opposed to 1.9 kcal/mole in the literature. As it is difficult to perceive that much error in the DTA value, it was felt that the calorimetric value should be reinvestigated. The average of 20 DTA determinations gave a value of 21.9 cal/ gram with 95% confidence limits of f 1 . 8 cal/gram for the fusion of PbpSiOl (190). The heats of fusion of poly(ethy1ene) single crystals, as a function of crystallization temperature, were determined by DTA (22). The DTA values, precision adiabatic calorimetry values (8), and crystallization temperatures were as follows: 59.1 c a l / p a m , 54.1 cal/ gram, 70"; 56.9 cal/gram, 56.2 cal/gram, 80 ; and 60.6 cal/ gram, 57.6 caljgram, 90". In a DSC study of Cu and Ag tellurides ( I @ ) , data were presented showing this technique to be accurate to *l% for determination of Cp, but which may rise to several percent in the vicinity of the phase transition. The effect of experimental parameters on the determination of Cp by the amplitude to mass ratio (234) was investigated and was found to give linear results only up to 22 mg of zeoiite. DSC, under favorable conditions, has been shown (242) to provide routine1 1-5% accuracy, as opposed to 0.1-1.090 by adiabatic calorimetry. While moderate losses in accuracy were experienced with DTA, as opposed to drop calorimetry, the former was indicated to have a substantial advantage with respect to time (44) that was often worth the loss in accuracy. Calibration has been discussed (157). The heat of transition of cholesterol a t 40" was determined to be 550 f 13 cal/mole (205), which was somewhat lower than the 575 f 58 cal/ mole determined by heat of solution measurements. After showing that AH values by DSC were accurate to within 490, with a precision of 2%, with P b and benzoic acid standards, heats of fusion were determined for several 2'deoxynucleosides (34). Heats of fusion were determined for 21 polycyclic aromatic hydrocarbons (39), 7 nitramines (114), urea and its derivatives (245), and for the rare earth-tin compounds (175). Heats of decomposition of benzothiazole complexes of divalent metals (166) and nickel thiocyanate complexes with aromatic amines (101) have been determined. The area under the DSC polymerization peak was used (13) to determine the heats of polymerization of encapsulated curing agents for epoxy resins. An excellent review of purity determinations by DSC has appeared (142) and the factors influencing the determination were demonstrated. It was concluded that in a system containing 1 mole 70,or less, impurity, DSC would give good data. The accuracy of the DSC-1B measurement as opposed to f for was indicated to be 5 x the calorimetric method. However, the DSC technique took 20 minutes as opposed to 2-4 days for the calorimetric method. Simple equations for linearization of DSC
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C. B. Murphy received his BS and MS degrees from the College of the Holy Cross in 1941 and 1942, respectively. After three years of Navy duty, he returned to Holy Cross as a member of the Chemistry Department faculty. In 1952 he received his PhD from Clark University. In the same year he joined American Cyanamid's Stamford Research Laboratory. After 10 years with General Electric's Advanced Technology Laboratories, he joined the Xerox Corp. as Manager of the Materials Analyses Area. He is now Manager of Toner Processing in the Xerographic Technology Dept
data for purity determinations have been presented (209). Purity and heats of fusion for 64 high purity compounds were determined (183). Camphor cryoscopy has been carried out (231) by measuring the temperature difference between melting of the camphor standard and camphor solution by DTA. Precise determination of melting and boiling points has been demonstrated (15), but it was pointed out that few commercial equipments have adequate atmosphere regulation for the boiling point determination. Such equipment was shown, and it was recommended that boiling points be determined at 3 pressures from 5 to 760 Torr. Plotting the data as log P (atm) us. l/t"K will permit averaging out experimental error, the value for 760 Torr can be reported, and the slope of the plot will be -E/R, where E is the heat of vaporization in cal mole. Analysis by DTA, or DSC, is based on the relationship of heat of reaction to specific amounts of material undergoing transition. The method mainly has been applied to mineralogical analyses. DTA was shown to be more accurate than X-ray diffraction for analysis of quartz in clay minerals (192) and it was pointed out that minor components registered as quartz make the chemical method unreliable. Using Ca(0H)Z as an internal standard, and plotting the area of the CaC03 peak divided by the area of the Ca(OH)2 peak us. YO CaC03 gave a linear plot that allowed analyses to be made. The presence of organic matter, dolomite, and magnesite were found to interfere with the quantitative estimation of CaC03. The determination of siderite, in the presence of kaolinite, is confounded by peak overlap which can result in as much as 30% of the siderite being missed (18). This can be reduced to 10% by using a N2 atmosphere. DSC was applied to determination of the wax fraction in petroleum products (66), where it was shown that the plot of the enthalpy of fusion us paraffin wax 7'0 was linear over the range 20100%. Further, the method was reported to be more accurate and practical than ASTM or IS0 methods for the same measurement. DSC was applied to the analysis of packaging films in conjunction with IR spectroscopy (211, 212) with a number of analytical techniques being involved. including measurement of film thickness by proportionality to peak area of constant die cut samples, and the vinyl acetate content of copolymers from the melting endotherm. In the case of determining kinetic parameters from DTA curves, the preceding comments about the significance of DTA peaks make the situation worse. Methods are based on the total peak area representing the reaction. In the most widely used Borchardt and Daniels (24) method, the fraction reacted is represented by the fractional area swept through divided by the total area. Kissinger's (109) method assumes maximum reaction rate at the peak apex, where reaction has been completed. It has been assumed that DTA and DSC curves represent the same physical phenomena (187) and that expressions derived for one apply to the other. Some of the confusion encountered can be appreciated by reading the discussion of kinetic data obtained with RDX (187). Despite the good agreement many investigators obtained with DTA techniques, most data have resulted from improper assumptions and must be revisited. Kinetic methods by DTA, DSC, and T G have been reviewed (38). Several methods of plotting DTA data were investigated
(25) for determination of the activation energy of urea nitrate decomposition and the values were compared with that obtained by TG. The low values obtained by DTA were assumed to illustrate the incorrectness of the assumption of maximum reaction rate at the point of peak apex. The other four approaches gave values close to that obtained by TG. Using a first-order kinetic expression and simplified Borchardt and Daniels technique, the decomposition kinetics of NaHC03 were investigated as a function of heating rate and particle size (215). Results indicated that particle sizes in the range 10-300 p and heating rates of 6, 12, and 18"/min had no effect on the kinetics of reaction. Results were not affected when the sample was diluted 1:4. A theory of DTA for a block type system with spherical cells packed with inert material was developed (10). From solutions of the equations utilizing total peak area, activation energies for magnesite decomposition were determined to be 61.5 (1.75"/min), 56.0 (3.49"/min), and 60.6 (5.56"/min) kcal/mole. Using a forced fit at maximum peak height, good agreement was obtained between theoretical and experimental curves (10). While not measured at the same temperature, the literature value of ca. 36 kcal/mole a t about 550" differed from those cited above. TG, DTA, differential T G (DTG), and electrical conductivity measurements have been applied to a series of cobalt amine complexes (81), where thermal dissociation temperatures were found to be in the order chloride > nitrate > bromide > iodide. DSC, in contrast to TG, provided the means of distinguishing between CY-, 0-, and y- Cu(C2O4)(NH3)z,and calculated enthalpies and apparent activation energies gave insight into bonding differences (121). DTA and TG measurements were used to elucidate the cis, trans to trans, cis isomerization of [CoCl2(NH&en]Br.HzO (224). Examination of 60 single crystals of ZrOz (162) gave sharp heating transformations in the range 1160 f 3" to 1190 f 3", while on cooling 1070 f 3" to 1100 f 3" were obtained. The polymorphism of KzCO3 was reinvestigated (199), confirming the monoclinic to hexagonal modification a t 420 f 5" and offering reasonable explanations for peaks reported by others. The thermal decomposition of several complex metal hydrides and their tertiary amine complexes by DTA and TG (48) has confirmed that the thermal stability of alkali metal aluminum hydrides increases with increased cation size of the alkali metal. In addition, this work resulted in clarification of many of the observed decomposition reactions, e.g., that LiAlH4 decomposition leads to the formation of LiSAlH6, not LiAlHz. DTA and T G were employed for investigation of ZnMo3010.5H20 and ZnMo207.5HzO (155), showing both to decompose passing through an intermediate hydrate, to the same products, ZnMo04 and MOOS. DTA, TG, and effluent gas analysis were applied to the thermal dissociation of NazS.9H20 (107), which was found to dissociate by three different sequences depending on the partial pressure of HzO. In addition to constructing the phase diagram for the system, heats of hydration were determined for Na2S.HzO (16.62 kcal/mole), NazS.2H20 (6.76 kcal/mole), and NazS.3HzO (1.96 kcal/mole). The thermal decomposition of Sr(OH)zm8Hz0, studied by DTA, TG, and DTG (49), was shown to pass through hexahydrate and amorphous monohydrate stages to Sr(0H)Z. The product resulting from exposure of CrO2 to high 0 2 pressures was examined by DTA, TG, X-ray diffraction, and magnetic measurements (206) to establish the phase boundary in the CrO2-Cr203-02 system. The effects of pressure on the surface acidity of MgS04.7H20 was studied by DTA, IR, and X-ray diffraction (106), and the increased acidity was explained in terms of lattice distortion which was demonstrated by lowering of the DTA decomposition temperature for MgS04.6HzO MgS04.5H20 + HzO with increasing pressure. TG and DTA applied to mechanically mixed and coprecipitated ZnO-Al203 have shown ( 4 ) that (A) a precursor with formula ZnO.Al203 is not favored, (B) for complete reaction to form precursor, 2Zn0.3A1203, the A1203 should be equal to, or above, the stoichiometric ratio, and (C) partial interaction to form a precursor may take place when A1203 is appreciably high, but not in stoichiometric quantity. DTA and X-ray diffraction were applied to establishment of the NaCl-MgC12 and KCl-MgC12 phase diagrams
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(75), where two incongruently melting compounds, NazMgCll and NaMgCl3, and two congruently melting compounds, K2MgC14 and KMgC13, were found. Applying the same techniques to the PbTe-AszTes system (113), no compound formation was evident. DTA also was applied to the As-Te (47) and confirmed it was a two eutectic system. DTA was employed to evolve the phase diagrams for the LiF-AlF3 and NasAlFe-LiF systems (89). An endothermic phase transition at 37" was reported (118) for cholesterol, but it is not present in hydrated cholesterol obtained from freshly removed human gallstones (167). However, the endotherm can be made to appear or disappear as the hydrate loses, or gains, water. DSC, IR, and polarizing microscope studies showed a crystal phase transition in yrazine at 29" with an enthalpy of 263 call mole (198). 8 i g h sensitivity DTA was used to determine the heats and entropies of fusion of D-, L - , and DL- mandelic acid (60). In the search for temperature standards for temperatures below Eo", DSC was applied to 13 asreceived and recrystallized compounds (105). Only two, hexachloroethane and hexamethylbenzene, were considered suitable. DSC showed that 4-nitro-rn-cresol undergoes exothermic decomposition at 230" when pure, but the exothermic decomposition temperature is lowered to 160" after aging at 155" (56). In contrast to this, p-nitrophenol, from which the compound was prepared, decomposed exothermically at 260" and showed no degradation on storage a t the same temperature. Degradation of p-nitrophenol was evident on storage a t 175", but the decomposition temperature did not o below 200". RDX-HMX mixtures were subjected to D%A (188) and, from the data, an approximate phase diagram was drawn for melting and decomposition. DTA was used to investigate transition temperatures of 107 compounds belonging to 10 homoloous series of aromatic anils (57) and DSC was applied to inary mixtures of cholesteryl esters (61). Heats of fusion and transition of cholesteryl methacrylate were measured (146). The phase diagrams of the binary systems myristic acid-stearic acid and lauric acid-stearic acid were generated (165) with DTA and X-ray diffraction, where it was found that the first system formed a complex decomposing a t ca. 48-49' and the latter formed two complexes, melting at 38" and 41". The Diels-Alder reaction temperatures of norpadiene with 19 dienophiles were determined by DSC (119). Using Stone's dynamic gas DTA equipment, the oxidation of toluene over cobalt-metal oxide catalysts was studied (176), and the activity of the catalyst was found to be proportional to the steady-state temperature rise. The morphology of deposited poly( xylylene) films was investigated (116) with the help of DTA and, by using a specially designed differential thermocouple system, the low-temperature polymerization of poly(xyly1ene) films by the vapor deposition technique was followed (222). Transition and melting temperatures of a series of poly(meta1 phosphinates) were determined by DSC (23). The melting behavior of isotactic poly(styrene), crystallized from the melt and from dilute trans-decalin solution, was examined by DSC (123), and 1, 2 , or 3 melting peaks could be observed: crystallization from the melt with large super cooling gave a small endotherm just above the crystallization temperature; melting related to the primary crystallization process; and another endotherm rising with decreasing heating rate, resulting from the second by continuous melting and recrystallization during the scan. Poly(ethylene), crystallized in a pressure capillary viscometer, was observed to give higher DSC melting points (210) than single crystals obtained by crystallization from xylene. This was attributed to crystal structure differences in the two samples. Irradiation of the viscometer samples resulted in multipeak fusion at lower temperatures (210). The observation that poly(ethy1ene) melting gave complex multiple peaks, while cooling the samples in the DTA cell gave a single identical peak ( 8 4 ) , was initially attributed to poor thermal conductivity and led to redetermination of DTA scans in silicone oil. In this medium, an exchanged-to-oil sample was resolved into 3 peaks. The highest of these represented the melting of single crystals. The other two were attributed to isolated lamellae exhibiting independent melting transitions. DSC of compressed poly(ethy1ene terephthalate) films showed (224) two glass
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transition temperatures, separated by an exothermic tendency between the two peaks, with the first peak lowered by 9-12". After treatment at 88" for 5 min, the thermograms gave essentially the same T,. Compression also lowered the crystallization temperature by 2-3" (214). This is in contrast to the DTA of poly(ch1orotrifluoroethylene) (163), where melting and recrystallization temperatures were found to increase with pressure. Transition temperatures determined by IR absorbance and DSC were found to agree for styrene-methacrylic ionomers (171). The introduction of sodium ions into this copolymer, by treatment with sodium methoxide, was found to increase the degree of ionization and Tg,the latter attributed to strengthening of residual intermolecular bonding by introduction of ions. Cis- and trans-piperazine rings, altemating between chair and boat forms, and strains have been offered as the explanation (195) for the low-temperature endotherm in soft-hard segmented polyurethanes. DTA of buthyl acrylate grafted poly(propy1ene) and poly( propylene), itself, showed the grafted material to have a slightly lower endotherm temperature and a slightly higher heat of fusion (92). The Tg of poly(ethy1ene) has been reviewed ( B ) ,with DSC among the techniques discussed. T measurement of acrylonitrile-a-methylstyrene by DSE were found to follow a sequence distribution predictive T , ,expression (IOO),rather than the linear Fox (58) expression. Using low temperature DTA measurement of the ice nucleation temperature, T,, and melting point depression, the phase diagram for water-poly(viny1 pyrrolidone) was determined (132). DSC was employed to show that a constant amount of H20, 0.36 gram per gram of poly(glycero1 monomethyl methacrylate), does not participate in ice formation (243), implying that this H2O is strongly associa k d with the polymer. DTA of atactic poly(styrene)-ethyl methyl ketone solutions ( 9 ) , with varied molecular weights of poly(styrene), has shown exothermal changes at temperatures close to the consolute temperatures of the systems. The phase diagram of transtactic poly(butadiene) with toluene, diethyl ketone, and nitrobenzene has been obtained by DTA (217) and heats of transition and fusion were measured.
THERMOGRAVIMETRIC ANALYSIS In the Derivatograph, a photo tube feedback system was used to control the voltage of the heating current to effect quasiisothermal TG (179). Combining this technique with a labryinth sample cover to impede the escape of gaseous decomposition products and back diffusion of air, quasiisothermal and quasiisobaric TG was implemented ( I 79). Application of the technique to potassium hydrogen carbonate depicted an unexplained three-step decomposition process and to manganese ammonium phosphate monohydrate where it showed no steady state being attained (180). Systems for high temperature TG have been discussed (214) and an induction heating system was demonstrated by application to N2 sorption by Nb-60 at.% Mo alloy at 1900". Equipment for use to 300 psig to 350" was fabricated (32) by mounting a DuPont 950 device in a pressure vessel. Application of this equipment to CuS04. 5H20 decomposition indicated that the initial decomposition under pressure involved solution of CuS04.3H20 in H20; the other decomposition steps were unaffected by pressure. Apparatus for TG-magnetic susceptibility to pressures of 68 atm. has been described (241) and was apof microbalanplied to K ~ [ C O ( C ~ O ~ ) ~ ]Application -H~O. ces to the measurement of gas pressure over eight decades (145) has been considered in terms of Knudsen forces and sensor reliability for various pressure ranges. A system for operation of a McBain thermobalance a t controlled sulfur atmosphere has been described (189), and the chlorination behavior of Cl2 and HC1 on metals and oxides has been investigated by T G (221). DTA, TG, DTG, and mass spectrometry measurements on siderite under atmospheres of air, N2, C02, and vacuum (115) were used to distinguish between oxidation and decomposition. T G in flowing gas, considering buoyancy effects, was used to study high temperature oxidation of Fe-16% Cr alloy (204). Pressure changes in vacuum TG, at constant temperature, were found to increase the apparent weight, M (fig), of the sample in accordance with the expression M
A N A L Y T I C A L C H E M I S T R Y , V O L . 46, NO. 5, A P R I L 1974
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= av T bT, where T is absolute temperature (240). Values of the constants were determined for Ar, N2, 02, and C02. Automated TG equipment capable of accommoding 8 samples (237) and carousel equipment for accurate weighing 20 specimens on a single microbalance (55) have been presented. The influence of particle size on the decomposition of isothiocyanatopentammine cobalt was investigated by T G (42) where it was found that the activation enthalpy was independent of particle size. The observed differences were attributed to activation entropy or related factors and were related to nucleation differences. Dehydration studies have shown ferrous malonate dihydrate (117) and BaC204.0.5H20 (231) lose water of crystallization in a single step. However, DTG applied to the malonate showed the dehydration to be a two-step process. TG showed Sr(OH)z.8H20 decomposed successively to Sr(OH)2.6H2O, Sr(OH)2.H20, and Sr(OH)2, to SrO (49). H20 sorption on ZnO has been followed by T G (147), indications being that a monolayer of hydroxide formed. In the clay minerals, such a study was combined with calorimetry (53) to show that the maximum differential heat of adsorption occurs with weights representing monolayer coverage. Dehydration of Cr(OH)3.3H20, studied by TG and DTA ( 7 I ) ,in N2 and O2 atmospheres, has shown that different results can be obtained with thin sample layers and thick samples due to water being entrapped in a microporous structure in the latter. TG, as well as DTA, IR, and X-ray diffraction, has been used to differentiate between turbostatic and well-crystallized Ni(OH)2 (122). UC was oxidized in a thermobalance in 0 2 and C02 atmospheres (228), with the ultimate products from the reaction series shown to be u308 and U02+y, respectively. Oxidation of (U, P u ) 0 2 solid solutions, with Pu/(U + Pu) ratios of 0.2 and 0.25, were studied by TG (219) with programmed heating and isothermal measurements. Mixed oxides with the 0.2 ratio were found to oxidize via a twostage process with the oxygen metal ratio increasing to 2.35 in the first stage, and to l.57 in the second. For the 0.25 ratio, the maximum oxygen/metal ratio was 2.35. The kinetics of nitridation of Si to SisN4 was studied isothermally (153), incorporating an oxygen getter technique (154), and it was found that 0 2 retarded Si3N4 formation by Si02 film formation, and, while the role of Fe is not completely understood, enhancement of a-Si3N4 is believed to occur via a vapor-liquid-solid mechanism with FeSi, as the molten phase. Isothermal T G has been used to study the reactions between Na2C03 and Vz05 over the range 400"-600" (111). Supported by DTA and X-ray diffraction. it was shown that two types of bronzes, NazV1203 and NaV6015, formed. TG, DTG, and DTA were applied to Ni[HP(C6H5)2]4 and Pd[HP(C,&)2]4 (238) confirming the identical decomposition pattern for both materials-ie., loss of one mole of benzene, followed by three moles of diphenylphosphine, to give MP( C&) as the residue. In the case of the nickel and cobalt bromide complexes, M[HP(C6H5)~]3Br2,the nickel gave NiP(C&), but the cobalt compound gave CoBr2 as the residue. The pyridine, isoquinoline, a,a-dipyridyl, and ophenanthroline complexes of the chromates and dichromates of Cu(KI), NI(II), and Co(I1) have been investigated by the Derivatograph (128). The group IIB metal halide complexes with N,N,N',N'-tetramethylenediamine and 1,2-diphenylphosphinoethanewere subjected to DSC and TG ( 2 0 ) .A series of P-diketone chelates of Nd, Gd, and E r were subjected to TG and gas chromatographic analysis (226) in an effort to find suitable reagents for GC analysis of rare earths. The data indicated isobutyrylpivaloylmethane, dipivaloylmethane, and trifluoroacetylpivaloylmethane offered this potential. TG examination of a series of 11 Pd alkyl xanthates (197) indicated that they were volatile at mm Hg, but decomposed at atmospheric pressure, leaving a Pd residue at 950". TG applied to acrylamide and acrylonitrile grafted Nylon 6 (229) showed that the thermal stability of the samples grafted with acrylonitrile increases with graft-on percentage and decreases with graft-on percentage of acrylamide. Isobutylene and butadiene were grafted to poly(vinyl chloride) (220),and T G showed the grafting to improve the thermal stability. The thermal cyclization of a poly(amic acid) to a poly(imide), in the pyromellitic dianhydride-p-phenylenediamine system, was treated by
thermal analysis (223), where it was shown that cyclization followed a zero order kinetic behavior with a n apparent activation energy of 6-7 kcal/mole. Poly(4,4-oxydiphenylene pyromellitimide) was studied by T G (43) with the carbonization step investigated in Ar and the subsequent oxidation process evaluated in air. Activation energies were 76.5 f 1.3 kcal/mole for the first step in Ar and 24.5 0.7 kcal/mole for final decomposition in air. A series of aliphatic polyoxamides were prepared by condensation of dialkyl oxalates with diamines, and TG, DTA, IR, and GC were used to assess their structure and thermal stability (203). Thermal stability of a series of poly(astriaziiies) was determined by TG (86). In the TG investigation of poly@-xylylene) (94), it was shown that chlorine substitution in the ring has essentially no effect on thermal stability, but that it is markedly improved by perfluorination of the methylene groups. The behavior of crosslinked poly(ethy1ene) was investigated by T G and DTA (139) where the former distinguished between two reactions: the first reaction, temperature decreasing with increasing peroxide content, was attributed to breaking of weak links; the second, occurring over a narrower temperature range, results from catastrophic breakdown. The different behavior pattern in air and N2 was illustrated by TG of poly[ocy(dicyclopentadienylzirconium)oxycarbonylferrocenylcarbonyl] (37). T G in N2 of four different forms of cellulose (50) indicated that the data fit most closely the plot for the Avrami-Erofeev equation. It was postulated that thermal degradation occurred by random nucleation and nucleus growth in the cellulose fibrils to yield a carbon whose microporous structure is a replica of the pore system in the parent cellulose. Isothermal TG of cellulose a t 226" for lo00 hours (30) permitted resolution of the curve into the minimum number of consecutive and competing reactions agreein with experimental data with 1%over the entire range. D8C and T G of KC1 impregnated cellulose have been used to cellulose decomposition reactions and mechanism (6). Differences in TG decomposition of a urethane polymer derived from 2,4-toluene diisocyanate and a poly01 at different heating rates were confirmed by the appearance of a second DTA peak at the higher heating rates (156).Visual observation of burning this same material indicated that it burned strongly, died down, and resumed burning again. The weight fraction a t the end of TG agreed exactly with the char left after burning. DTA, with and without retardant, indicated that the flame retardant could increase the rate of burning and make the fire worse. It was concluded (156) that a single thermogram was useless in providing data as to how a material might burn. DTG was used (93) in the study of NaNbO3.5Hz0, where, in contrast to the apparent single step dehydration shown by TG and DTA, it showed two-step dehydration. In the thermal degradation of cellulose ( 6 5 ) , DTG defined the temperature of maximum weight loss much more reproducibly than could be obtained from the T G curve and application to fresh and aged (200" for 16 hours) paper showed marked changes in the DTG curves. With the aged paper, the initial DTG peak was lowered and the second increased. Application of DTG to UV irradiated and non-irradiated poly(viny1 chloride) (65) showed that the two peaks of the latter become one in the former, serving as a sensitive indicator for degradation. DTG curves of alkaline earth formates (36) were found to generally follow the DTA curves. In the case of strontium formate, DTG curves were shown for powder, compacted disk, and two sizes of single crystals, where sample size was shown to influence decomposition-ie., to the oxide or to the carbonate. T G has been applied to the analysis of H2O in a variety of materials with success (208). However, sodium tartrate dihydrate, dried to constant weight by isothermal TG at NO",was examined microscopically and occluded water and/or mother liquor was still found in the "dehydrated crystals" ( 1 9 ) , and Karl Fischer analysis showed 0.36% H2O remained. TG measurement of the thermal stabilities of analytical precipitates continued with the study of a series of lead(I1) hexanitrocobaltate(I1) and hexacobaltate(II1) compounds (194).In a study of dithiocarbamatebased fungicides (129), a T G method was evolved for analysis of ethylene-bisdithiocarbamates that compared
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well with the CS2 method. The levels of two phenolic antioxidants in poly(ethy1ene) disks was measured by a TG technique (191) based on the induction period before onset of degradation a t constant temperature. The TG method was extended to measure the diffusion coefficients of the phenols in poly(ethy1ene) (191). Knudsen cells have been described (33, 239) for use with the Mettler thermobalance. From the vapor pressure plots, heats of vaporization and heats of sublimation were measured. Derivatography, with simultaneous electrical conductivity, was applied to a series of hexitols and pentitols (202).Heating the hexitols to 200"-250" resulted in an endothermic weight loss, while the pentitols underwent exothermic weight loss a t ca. 230". The kinetics of isothermal solid-state reactions have been compared on the classical nucleation-and-growth process expression, -lnln(l - a ) = 1nB mlnt, where a is the fraction reacted in time t and B and m are constants (82).Kinetic data expressed as a plot of lnln(1 - a ) us. lnt will give a straight line if OC values are limited to 0.15 to 0.50. Under these conditions, the constant rn is characteristic of the process and gives an insight into the mechanism. Values of m for 10 different rate equations are given and the applicability of the technique was demonstrated with decomposition of kaolinite, brucite, and BaC03 (82). The kinetics and reaction mechanism for KzCO3 to form 4PbO.SiOz + KzC03 and for PbOSiOz Kz0.2Pb0.2SiOz were studied by isothermal weight loss and TG (213) v.here both reactions were found to be nuclei growth controlled with activation energies of 85 and 108 kcal/mole, respectively. Freeze-dried and reagent grade BeS04 were isothermally decomposed to B e 0 and SO3 (98) and the freeze-dried material was found to decompose a t a lower temperature, confirming previous observations for FeS04 and Alz(S04)3. The kinetics followed a contracting area model and gave activation energies of 51 to 54 kcal/mole for both samples of BeS04. This same material was investigated by TG in air from atmospheric pressure to 2 mm Hg (230). In this case, Piloyan's (182) method gave an activation energy of 48 kcal/mole from the TG curve and 46 kcal/mole from the DTA curve. Dissociation pressure measurements gave better agreement with the reaction BeS04 B e 0 + SO2 + '/zOZ(230). Isothermal and dynamic TG of CaC03 were conducted with different sample sizes (1-32 mg) and heating rates (0.29-73.6"/min) (62). The dynamic data were processed by three basic techniques: (A) difference-differential (59), (B) integral (46), and (C) single differential ( 1 ) . The last two, with a reaction order of 0.5, gave better results, corresponding to the contracting area equation. These data confirmed prior results on sulfates (97) that method (C) most consistently matched isothermal results in terms of kinetic model, activation energy, and preexponential term. Effects of sample mass, self-cooling, and COZ partial pressure on kinetic measurements were discussed. Dynamic results were claimed to lack the precision or consistency of the isothermal results (62). In the case of dynamic TG with the ZnO-Al203 system ( 5 ) , the integral method was found to give better results than the difference-differential method. The integral method was applied to alkaline earth carbonate decompositions (103) and, within experimental error, good agreement was obtained between observed activation energy and A H It also was observed (103) that SrC03 containing Sr(0H)Z impurity had a higher activation energy than the pure carbonate. It was noted that the original derivation of the integral method equations was in error (174). However, it was shown (104) that the error had no effect on calculation of activation energies. Isothermal TG of urea nitrate (26) with different sample sizes influenced the thermograms and reaction kinetics, Differences resulted from thinly spread and compacted samples. Freeze-dried FeS04 was found to follow a two-step decomposition sequence (96). Isothermal TG was applied to this material, and kinetic parameters for the consecutive reactions were determined by mathematical treatment of the two rate expressions (99) in reasonable agreement with reported data. A simple integral method for kinetic data evaluation was presented (196) and was applied to CaS04.0.5Hz0 dehydration. In this instance, the dynamic method had an
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advantage over the isothermal technique as the process occurs close to equilibrium temperature, without incubation, and the reaction rate increases rapidly with temperature. The isothermal method would encounter difficulty in attaining temperature without decomposition. Observation was made that the molecular weight distribution of degrading poly(styrene) tends toward a value of 1.5 for the ratio of weight to number average molecular weight and rate of weight loss for thermally prepared polymer had a 0.25 power dependence on number of polymer molecules per unit weight or volume. This resulted in an examination (236) of the rate of volatilization arising from depropagation of large radicals which showed the square of the initial rate to be a linear function of the number average degree of polymerization. a-Methyl styrene, with and without fully deuterated side chain, were polymerized by anionic methods to give monodispersed polymers over a large molecular weight range. These were subjected to pyrolysis (235) where it was shown that the rate of weight loss was proportional to the number average degree of polymerization. For a polydisperse system, the rate of conversion was proportional to the wieght average degree of polymerization. At high molecular weights. the rate was independent of molecular weight, independent of the average selected. Rate expressions were derived for these cases (235). Dynamic TG was applied (164) to obtaining order and activation energy from polymer pyrolysis using the graphical method of Briodo (29). The effects of solvent loss from a polymer were demonstrated by changing reaction order in the initial temperature range, which was converted to a first-order reaction after driving off the solvent with a subsequent sample. Changing the surface area-to-volume ratio by mincing a sheet sample of SE7501U silicone rubber changed a first-order reaction into a two-thirds order reaction. Using the expression T = (ln2)/k = 0.693k to relate the half-life, T, to the reaction rate (164), TG data predicted a half-life of 26.3 min compared to an actual value of 25 min at 500". The suggestion was made that comparison of test and part data a t elevated temperature could be used to estimate decomposition rates at slightly lower temperatures (164). This same suggestion was voiced (177) as a result of programmed and isothermal TG experiments with Dow-Corning silicone 6-1106. In dynamic TG, an activation energy of 4.4 kcal was found for evolution of solvent from the sample and a larger activation, 26.4 kcal, was associated with polymer decomposition. The isothermal data gave the same activation energy and frequency factor for the polymer decomposition ( 1 77) even with an enormous increase in sample weight and size. Based on the expression C = f ( t , T ) (108), it was suggested (130) that the partial differential equation of concentration, C, with respect to time, t, and temperature T, to be applied to non-isothermal reactions. Criticism has stated (77) that time and temperature parameters give no direct indication of conversion of C since any value of C between 0 and 1 could correspond to a given time-temperature data pair depending on the history of reaction, which is the time-temperature relationship from beginning of reaction. The basic expression, C = f ( t , T ) ,must be considered a path function, and, as such, it cannot be partially differentiated (77). The introduction of two time scales, isothermal and thermal time, with the latter simply dependent on temperature, for a single experiment was indicated to be faulty as it is based on comparison of two different isothermal experiments (207), has shown that the currently accepted practices for obtaining nonisothermal kinetic equations are not fundamentally in error. The values of the temperature integral of the Arrhenius equation were computer calculated and it was found that an approximately linear relationship was established between the log of the integral and reciprocal temperature (78). The derived expressions were compared with the approximation methods of Murray and White (170) and of Doyle (51) and the percentage error determined. It was not possible to express a preference for any one of the approximations. A simple, rapid method for estimation of reaction order has been proposed (79) based on the conversion ( x m ) corresponding to the maximum point of a
A N A L Y T I C A L C H E M I S T R Y , V O L . 46, NO. 5, A P R I L 1974
DTG curve. Calculated values of xrn us. reaction orders from 0.1 to 3.0 were plotted, for data covering the usual range of values for kinetic constants, that permitted simple graphical assessment of reaction order with an error of *5%. The approximate method of Horowitz and Metzger (90)has been made very accurate by an asymptotic exT , (31) where T is a temperapansion of 1/T about T ture attained within the system and T , is the temperature where the rate is maximum.
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OTHER METHODS Application of mass spectrometry to the detection of evolved gases has been applied to aluminum and hafnium sulfates (178), where primary peaks were identified as S02, SO, and 0 2 a t 800" and 725".Typical of polymer applications was the investigation of poly(methy1 methacrylate) (193), where generation of the parent ion of the monomer was followed as a function of the heating rate and Arrhenius plots for a first-order reaction were generated. Equipment for simultaneous DTA-mass spectrometric analysis has been described (7). Combined DTA-mass spectrometry was employed to show that heating urea leads to the formation of biuret and cyanuric acid (120) and also that the reactions are not separate, but overlap to a large degree. Simultaneous TG-mass spectrometry equipment was built to identify the thermal decomposition products evolved from nonmetallic materials (1I O ) and a similar system was applied to the analysis of the Orgueil carbonaceous chondrite meteorite (68). The latter system was coupled to a computer (67) and applied to Green River shale and lunar soil samples. A scan-programmer to monitor specific mass numbers in the course of thermal decomposition has been described (45), and was demonstrated in TG of zinc hydrocarbonate. A fluoride specific electrode was employed to monitor HF swept from hydrofluoro polymers undergoing thermal decomposition (54), opening the door to a totally different approach to effluent measurement. Comparing results with TG, H F elimination was found to be the major decomposition route for poly(viny1 fluoride) and poly(viny1idene fluoride), but not for poly(trifluoroethy1ene). Activation energies were calculated from the electrochemically determined inflection point. The radioactive emanation method for effluent gas analysis continues to be applied in Europe. The H2 reduction of NiO was followed by the emanation method and catharometric determination of water (185).In both cases, data permitted calculation of an activation energy of 28 kcal/mole. The emanation method also has been applied to the thermal decomposition of periodates (12) and CaC03 ( 8 0 ) . Equipment for emanation analysis and DTA was described (52) and was applied to FeC204.2H20, ZnO, and Li2CO3. Principles of the technique have been used, entrapping small organic molecules within inorganic materials during precipitation and measuring their emanation during phase transformation by gas chromatography (64). It was stated that this technique was broadly applicable and did not involve radiation hazard. Evolution of gaseous decomposition products from copolymers of acrylonitrile were monitored by a pirani gauge ( 7 4 ) and manometric measurement of increasing pressure was used to follow decomposition of Si3N4 (17). Thermal conductivity of H2O in a He stream, together with isothermal TG, was used to study the dehydration of tetracycline hydrates (141). The introductory remarks to the symposium on therLITERATURE CITED Achar, B. N . , Brindley. G W . , Sharp, J . H , Proc Int. Clay Conf.. Jerusaiem. 1, 67 ( 1 966) Akiyarna, J , Therm. A n a l , Proc. lnt. Conf.. 3rd. 7977 1, 45 (1972). Arai, Y . . Yasue. T., Miyake, H . , Nippon Kagaku Kaishi 1972,547: CA. 76, 144362 ( 1 972) (4) Arora, E. R . . Banerjee. R. K , Prasad Rao, T . S. R , Mandal, N K., Bhattacharyya, N . 6 . . Sen, S P., Thermoch!mica Acta. 6,
119 (1973) Arora, B. R
,
Banerjee, R . K . , Prasad Rao.
momechanical analysis (27) discussed the features of torsional pendulum, torsional braid, and Rheovibron dynamic tension methods, including sample size, temperature range, and phenomena detected. At the same symposium, torsional braid and torsional pendulum analysis of polymers were reviewed (69). Poly(norb0rnadiene) was examined by torsional braid analysis, DTA, and TG (70), where it was shown that the polymer had a glass-transition temperature of 320" (more readily determined by torsional braid) and started to decompose a t 425".The glass transition temperatures of atactic, syndiotactic, and isotactic poly(methy1 methacrylate) and poly( tert-butyl methacrylate) were determined by torsional braid, dilatometry, and DSC (72). Agreement between the techniques left something to be desired. Apparatus for measurement of resistivity up to 1000" in vacuum has been constructed (144). Simultaneous electrical conductivity and DTA measurements were made on a number of sulfate systems (35) showing the electrical measurement to be effective for determination of melting and for some solid state transformations. In the Ag2S04Li2SO4-Cs2SO4 system, successive solid state transformations were followed by steps in the conductivity curve. Electrical resistance measurements on liquid S and Se (232) have shown some similarities in the two materials and polymerization and chain scission temperatures were established for S. LuF3 and YF3 high temperature forms were shown to be solid electrolytes (172) by conductivity measurements. Resistance measurements were used (87) to determine the phase diagram for the Th-ThCx system. Simultaneous electrothermal analysis and dilatometry was applied in studies (102) of the thermal decomposition of commercial cathode coatings. A hot stage microscope for use to 100" has been described (40) and was used to measure the reflected light intensity from inorganic salts. Fusion for KN03, by this technique, occurred a t 334", 1" different from DTA measurement. It has been suggested that this technique be called thermooptical analysis, TOA (85). Work also was performed with KC104 and K2Cr04, the ICTA-NBS temperature standards, and glauberite and gypsum (85). Apparatus for depolarized light intensity, DLI, for use with DTA was described (16) and its applicability demonstrated with anisaldazine and cast poly(propy1ene). DLI measurement applied to poly(styrene) (159) showed excellent agreement with DTA, but both techniques failed to show the 75" second-order transition detected by linear and volumetric expansion. White light transmission, in addition to the two preceding techniques, was applied to poly(styrene) and was found to give data in good agreement with dilatometry for initial transformations as a function of molecular weight. (158).Transmitted light intensity was used (200) and compared with DSC in a study of poly(2,6-disubstituted-1,4-phenyleneoxide) blends. Identical results were obtained with white and green light. A review of the application of ultrasonics in the study of phase changes has appeared (95). The technique was applied to a series of dialkoxyazoxybenzenes (143), bibenzyl (168), pentadecane (216), and benzene, p-xylene, and cyclohexane (112). Equipment has been described (225) and applied to measurement of transition temperature of polymers. In the examination of a number of polymers (41) under dynamic heating conditions, response was found to be influenced by two factors: (A) orientation of polymer molecules, and (B) viscoelasticity or sonic viscoelastic function of the polymer. Equations were given (41) relating these parameters to sonic response.
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