Far Infrared Absorption of Hydrous and Anhydrous Aluminas G . A. Dorsey, J r . Department of Metallurgical Research, Kaiser Aluminum & Chemical Corp., Spokane, Wash. ably well into the far infrared if the degree of alumina crosslinking is great (5).
INFRAREDSPECTRA of aluminas have been widely used to study hydroxide phase transitions ( I ) and for qualitative identification (2-4). These studies were generally limited to the intermediate infrared region, as only the hydroxyl stretching and bending modes were involved. But anhydrous aluminas generally cannot be clearly distinguished by intermediate-range infrared data: gamma, pseudogamma, eta, and chi aluminas fall into this category. We sought, instead, to identify these aluminas by using the far infrared absorptions
EXPERIMENTAL
Reference Aluminas. A series of pure alumina phases was obtained from our Permanente Metals Division Laboratory. These aluminas had been identified by X-ray diffraction and differential thermal techniques. These samples were taken as being representative ,of the alumina mineral system: (a) Alumina trihydrates: gibbsite (alpha trihydrate); bayerite (beta trihydrate). (b) Alumina monohydrates : boehmite (alpha monohydrate) ; diaspore (beta monohydrate) ; pseudoboehmite (nonstoichiometrjc monohydrate-type alpha, with a d (020) either near 6.6 A or 6.4 A). (c) Anhydrous aluminas : alpha; gamma; pseudogamma; low-temperature eta (from bayerite heated at 361 " C for 24 hours); high-temperature eta (from bayerite heated at 683" C for 24 hours); theta; low-temperature chi (from gibbsite heated at 450" C for 4
H
of their A1-0-A1 linkages; similarly, the A1-0-A1 bonds of aluminum hydroxides were also of interest, These bond groupings have absorptions only below 900 cm-', and prob(1) T. Sato,J. Appl. Chem., 14,303 (1964). ( 2 ) H. J. Eding, M. L. Huggins, and A. G. Brown, U.S.A t . Energy Comm. Rept. IDO-14580, Phillips Petroleum Co., December 5, 1961. (3) L. D. Frederickson, ANAL.CHEM., 26,1883 (1954). (4) J. W. Newsome, H. W. Heiser, A. S.Russell, and H. C . Stumpf, Alcoa Technical Paper No. 10 (1960).
( 5 ) G. A. Dorsey, Jr., J. Electrochem. SOC.,113, 169 (1966).
a9 800
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35
140 80
35
140
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800 Wavenumben (cm'
140
80
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800
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Figure 1. Far infrared spectra of aluminas and aluminates Gibbsite Bayerite Boehmite D. Pseudoboehmite E . Diaspore F. Alpha (corrundum) G . Gamma H . Pseudogamma A. B. C.
Eta (high temp 700" C) Eta (low temp -350" C) K. Theta L. Chi M . Sodium aluminate 18 H20 N . Sodium aluminate (120' C bake) 0. Sodium aluminate (400' C bake)
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hours); high-temperature chi (from gibbsite heated at 770’ C for 24 hours). Sodium aluminates were also examined, initially and after a series of bakings: 5 hours at 120” C and 2 hours at 400” C. Infrared Analysis. A modification of the polyethylene support method (6) was found whereby solid powders can easily be prepared for far infrared analysis. A small quantity (about 0.3 gram) of the powdered sample was placed on a sheet of 3.5-mil-thick low-density polyethylene. This was covered with another polyethylene sheet, and the powder was rubbed into the two sheets. After removing the excess powder, the sheets were mounted and fused together under a heat lamp. These polyethylene composites were scanned over the region from 35 to 650 cm-1, using a Beckman IR-11, in doublebeam operation us. air. The samples were incorporated in potassium bromide pellets when similarly scanning the 650 to 800 cm-1 region with a Beckman IR-7. As a check against the possibility of sample transformations during the polyethylene mounting process, the polyethylene composites were also examined with the IR-7 in the 900 to 1100 cm-1 region. The results were cross-checked against KBr and nujol mull data previously obtained for the same sample. In no case was there evidence that the mild heating had altered the integrity of the sample. (6) H. J. Sloan and K. E. S h e , Beckman Data Sheet No. IR-8084.
The centers of broad bands were determined by ordinate scale expansion while the wavelength accuracy of the instrument, operated under survey scan conditions, was on the order of 1 wavenumber (7). RESULTS
Representative spectra are shown in Figure 1. These illustrate the relative intensities of the various absorption bands, whose wavenumber positions are listed, and show the distinctions that exist between these aluminas. Absorptions due to the supporting medium, polyethylene, have been omitted from these tracings in the region above 650 cm-’. Note that unbaked us. baked, the far infrared spectrum of sodium aluminate is greatly altered by the presence of adsorbed water. Baking at 120” C yields the same material, by far infrared analysis, as a 400’ C bake; therefore, the alteration in far infrared spectra may largely be due to the removal of adsorbed, as contrasted with structural, water. RECEIVED and accepted February 29, 1968. The author thanks the Kaiser Aluminum & Chemical Corporation for its support of this work and for its permission to publish these results. (7) K. N. Rao, C. J. Humphreys, and D. H. Rank, “Wavelength Standards in the Infrared,” Academic Press, New York, 1966, p 145.
A Simple and Rapid Method for the Microdeterminationof Carbon and Hydrogen in Polymeric Compounds Containing Boron and Silicon Eloisa Celon and Silvano Bresadola Department of Chemistry, Universith di Padova, Italy
THE DIRECT COMBUSTION of organic compounds containing boron and silicon is known to cause the formation of oxide coatings, which occlude organic material (I), and silicon (2) and boron (3) carbides. This makes the microdetermination of carbon and hydrogen in such materials difficult. For low molecular weight compounds containing boron and silicon, reliable results are obtained with Pregl’s modified methods ( I , 4). According to these methods the aforesaid difficulty can be overcome by mixing the sample with vanadium pentoxide (4), vanadium pentoxide and potassium dichromate or tungsten oxide (3), cerium oxide and metallic or fine platinum gauze at 850” C (6). Such methods silver (3, also give good results in the case of low molecular weight organoboron and organo-boron-silicon compounds, such as carborane or its isomers and bis-(chlorodimethylsily1)neo(1) F. Pregl and H. Roth, “Quantitative Organiche Mikroanalyse,”
7th ed., Springer-Verlag, Wien, 1958, p 36. (2) J. A. McHard, P. C. Servais, and H. A. Clark, ANAL.CHEM., 20, 325 (1948). (3) R. C. Rittner and H. Culmo, Zbid., 34,673 (1962). (4) H. Roth, Angew. Chem., 50, 593 (1937). (5) G. J. Kakabadse and B. Manohin, Mikrochim. Acta, 5-6, 1136 (1965). (6) E. G. Rochow, “Introduction to Chemistry of the Silkones,” Wiley, New York, 1946, Chapter 7. 972
ANALYTICAL CHEMISTRY
carborane. However, they yielded extremely large and unreproducible negative errors when applied to polymers containing sequences such as fcBloHloC-Si(R)24- (7). Also, relatively simple polymeric compounds have been reported to offer difficulties on combustion (8). The polymers described here can be expected to show still greater errors because of their heat stability and molecular complexity. In this paper we describe a method for the microdetermination of carbon and hydrogen in polymeric compounds, containing in their sequences boron and silicon atoms, using an F & M Model 185 C-H-N analyzer. The combustion of the sample is performed in a static oxygen atmosphere for prolonged periods at high temperature, using a highly active catalytic mixture composed of Mn02, Cr203,and WO,. So far as the microdeterminations of boron and silicon in these compounds is concerned, they are performed according to the procedures of Rittner and Culm0 (9) and Christopher and Fennell (IO),respectively. (7) S . Bresadola, F. Rossetto, and G . Tagliavini, Chim. Znd. (Milan), 49, 531 (1967). (8) M. Goodman and A. Kossoy, J. Am. Chem. SOC.,88, 5010 (1966). (9) R. C. Rittner and R. Culmo, ANAL. CHEM., 35, 1268 (1963). (10) A. J. Christopher and T. R. F. W. Fennell, Talanta, 12, 1003-1008 (1965).
