1344
Vol. 63
NOTES
slight shoulder at 7.28 f.t and the broadening of the 7.93 f.t band are due to the presence of phenol. 4 In addition to the work described above the authors also have determined that it is possible to detect phenol in aqueous solution at a concentration of 0.45% using the band at 8.15 f.t, and phenoxide ion at 0.63% using the band at 7.93 f.t. There are experimental indications that it is possible to detect phenoxide ion at concentrations as low as approximately 0.2% in water. 6 (4) An approximation of the apparent dissociation constant for phenol can be obtained by plotting the decrease in intensity of the 7.28 '" band (which decreases in intensity on increasing the phenoxide ion concentration) versus the observed pH. When such a plot is made, it is seen that the mid-point of the curve is at pH 10, which is close to the known value for this ioni.zation.' Although only three points have been used to obtain this value, the authors feel that these points are significant. An attempt will be made in the future to refine these meas-
Table I, and are believed accurate to 0.005 A., considering the inaccuracy of the wedge technique and the lack of temperature control. The values for the pure components, viz., 3.875 and 4.059 A. for the chloride and bromide, respectively, agree satisfactorily with those of the National Bureau of Standards,'" 3.876 and 4.059 A. at 26°. I NH,CI-NH,Br
TABLE LATTICE CONSTANTS OF
Compn" mole fraction of NH,Br
0.00
.04 .08 .11 .23
Lattice constant,
A.
3.875 3.875 3.882 3.883 3.907
SOLlO SOLUTIONS
Dev. Compn., from admole Lattice ditivity, fraction constant, A. X 10' of NH.Br A.
-7 -8 -12 -10
3,963 4.009 4.060 4.059
0.47 .70 .99 1.00
Dev, from ad-
ditivity, X 10'
A.
+2 +5 +3
(5) C. M. Judson and M. Kilpatrick, J. Am. Chem. Soc., 71, 3113 (1949). (6) The quantitative determination of phenol in water by infrared spectrophotometric methods is being explored in the authors' Laboratory.
It seems clear that the U.S.P. materials in the present work contributed no error greater than that introduced by the X-ray technique itself. Table I also gives the deviation of the lattice constants from Vegard's rule of additivity. It is seen that the solid solutions follow Vegard's rule within experimental error except for those with high ammonium chloride content, which exhibit negative deviations.
LATTICE CONSTANTS OF AMMONIUM CHLORIDE-AMMONIUM BROMIDE SOLID SOLUTIONS
(4) H. E. Swanson and E. Tatge, "Standard X-Ray Diffraction Powder Patterns," Vol. 1, National Bureau of Standards, 1953, p. 59. (5) H. E. Swanson and R. K. Fuyat, ref. 4, Vol. 2, p. 49.
urements.
By
VINCENT C. ANSELMO AND NORMAN
O.
SMITH
Department of Chemisf1'1J, Fordham University, New York, N. Y. Received January 28, 1959
The need for a convenient means of analyzing solid solutions of ammonium chloride in ammonium bromide led to the measurement of the variation of their lattice constant with composition. The lattices of both components are of the interpenetrating simple cubic type at room temperature, and a complete series of solutions is possible between the two. Only one isolated measurement of a lattice constant of such a solid solution has ever been reported. 1
THE USE OF DIFFERENTIAL THERMAL ANALYSIS FOR INVESTIGATING THE EFFECTS OF HIGH ENERGY RADIATION ON CRYSTALLINE AMMONIUM PERCHLORATE By
ELI
S.
FREEMAN AND DAVlO
A.
ANDERSON
Pyrotechnics Chemical Research Laboratory, Picatinny Arsenal, Dover, New Jersey Received January 6, 1959
The lattice constants for each composition are shown in
Differential thermal analysis (d.t.a,) involves the continuous measurement of temperature differences between a sample and thermally inert reference compound as a function of sample or reference temperature and/or time, as both the sample and reference compound are heated simultaneously at a predetermined rate. This technique has been used to characterize and to study the high temperature physico-chemical behavior of clays, minerals, inorganic and organic systems 1 as well as for investigating reaction kinetics. 2 ,3 In this paper we are reporting on the application of differential thermal analysis to the study of the effects of radiation on crystalline ammonium perchlorate. A powdered sample of C.P. ammonium perchlorate was irradiated with an OEG-50 X-ray tube, in air, for 100 hours at 40 kv. and 20 mao at a distance of 1 em. from the tungsten target. The total dosage of radiation was approximately 107 roentgens. The differential thermal analysis apparatus was similar to that previously reported 4 with the exception that a two pen Leeds and
(1) R. S. Havighurst, E. Mack, Jr., and F. C. Blake, J. Am. Chem. Soc., 47,29 (1925). (2) R. K. McAlpine, ibid., 61, 1005 (1929). (3) E. T. Teatum and N. O. Smith, THIS JOURNAL, 61, 697 (1957).
(1) C. B. Murphy, Anal. Chem., 30,867 (1958). (2) E. S. Freeman and B. Carroll, THIS JOURNAL, 62, 394 (1958). (3) H. J. Borchardt and F. Daniels, J. Am. Chem. Soc., 79, 1102 (1957). (4) S. Gordon and C. Campbell, Anal. Chem., lI7, 1102 (1955).
Experimental U.S.P. grade ammonium chloride and ullllllonium bromide were used without fUl'ther purification. The solid solutions were made by mixing hot concentrated aqueous solutions of the components with stil'l'ing and allowing to cool. Stirring was COll tin ued for at least 48 hoUl's to improve the homogeneity of the resulting crystals. The latter were filtered, dried ovemight and stored in a desiccator. They were then analyzed potentiometrically (silver and calomel electrodes and standard silver nitrate) with the help of an adaptation of the method of :VrcAlpine. 2 Total halide was determined, and then chloride alone, after destroying bromide with permanganate. The accuracy of the method, established by analyzing synthetic mixtures of ammonium chloride and bromide, gave mole fractions of NH,Br within 0.01 for low bromide contents and within 0.003 for high. X-Ray powder photographs were taken at room temperature as described in an earlier study3 and the lattice constants evaluated therefrom. The sharpness of the lines indicated that the soHds were essentially homogeneous. Only the last five lines of greatest glancing angle were used for the calculation of each constant, but, for each solid, the mean deviation of these was usually less than 0.002 A. and, at the most, 0.004 A. (mole fraction of NH,Br
0.23)..
,i
August, 1959
1345
NOTES
Northrup Speedomax recorder was employed to record the differential thermal analysis curves. The differential thermograms obtained for 250 mg. of non-irradiated and irradiated samples in 430 air are shown in Fig. 1. At 244° an endotherm is l- e x observed with a point of inflection at 240° which ~ corresponds to the crystalline transition of am- ::lEll. e 0 monium perchlorate from orthorhombic to cubic. 5 l- ez The point of inflection is not seen easily from the oC(...J d.t.a. curve; however, it is obtained readily from zj:: the electronically generated derivative d.t.a. curve a: ex shown in Fig. 2 which was simultaneously re- lJ..lJ.. 0 corded. 6 The crystalline transition was followed C ee z by an exothermal d.t.a. band of relatively small amplitude with a peak at 309°. During this 10 20 30 40 50 reaction gases having chlorous and nitrous odors TIME, MIN, were detected and the sample darkened. At Fig. I.-Differential thermal analysis curves for non430° a sharp, highly exothermal reaction occurred, in air at which resulted in ignition leaving no residue. Dur- irradiated and irradiated ammonium perchlorate pressure j heating rate 10 0 /min.; sample ing this reaction the sample temperature exceeded atmospheric weight 250 mg; differential temp, liT, °C. vs. time, min. that of the thermally inert reference compound, 1, non-irradiated ammonium perchlorate; 2, irradiated amalumina, by more than 80°. monium perchlorate. The behavior of the irradiated sample upon heating was significantly different from that of nonirradiated ammonium perchlorate. Unlike the non-irradiated sample, prior to the crystalline transition which occurred at the same temperature as that of non-irradiated NH4CI04, two endotherms and an exotherm are observed. The peaks of these bands appear at 81, 154 and 234°, respectively. Beginning at approximately 80° a crackling sound was heard which was accompanied by splattering of the crystals. This phenomenon ceased during the crystalline transition. It was interesting to note that the tannish colored irradiated crystals turned white over this period. Small quantities of white sublimate were observed at 130° and a chlorine odor was noticed at approximately 170°. During crystalline transition, water was liberated and the vapors condensed on the walls of the Pyrex tube containing the sample. Immediately after the crystalline transition an exothermal reaction occurred, as indicated by the band at 277°, which o 100 200 300 400 was accompanied by the evolution of brownish Sample temp., °C. vapors due to the formation of oxides of nitrogen. Fig. 2.-Derivative differential thermal mmlysis curve for This reaction was succeeded by two additional non-irradiated ammonium perchlorate; dLiT/dt vs. samplo exotherms. The fil'st occurred between 305 and temperature, °C. 385° and the second from 385 to 455°. The latter reaction is highly exothermal and corresponded to Mass-spectrometric the reactions of the non-irradiated material over the and untreated materials. same temperature interval. However, the ampli- analysis of an irradiated sample showed the prestude of the exothermal band was approximately ence of small amounts of gas consisting of a relatively one-eighth as large as that of the non-irradiated large fl'action of H 20 and relatively small fractions samples. The decrease in the extent of reaction of O2, HCI and N 20 which apparently were trapped These products are among those over this temperature interval is probably due to ill the crystals. 6 partial decomposition of the ammonium perchlorate reported for the thermal decomposition of nonduring and immediately following the crystalline irradiated ammonium perchlorate. Upon heating, the vaporization of water and expansion of the transition. In view of the significantly different thermal trapped gases probably caused the rupture of the behavior of irradiated and non-irradiated am- irradiated crystals. Acknowledgment.-The authors wish to thank monium perchlorate it is interesting to note that X-ray diffraction patterns and infrared analysis Joseph J. Campisi for irradiating the samples and did not indicate any differences between the treated for carrying out the X-ray analyses; Dr. Harold J. Matsuguma, et al" for the infrared analyses, and (5) L. L. Bircntnshaw and B. H. Newman, Proc. Roy. Soc. (London). Philip Rochlin for the mass-spectrometric analysis A227, 115 (l 954). of the gases. (6) C. Campbell, S. Gordon and C. Smith, Anal, Chern., in press.
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