Curve resolution of partially overlapping peaks at 947 cm-1 and 965 cm-' may make it possible to quantify also the small amounts of STP.6Hz0.
ACKNOWLEDGMENT I wish to thank E. Strijks of the Chemical Technology Department of the University of Technology, Eindhoven, for measuring the Raman spectra, A. A. U'. A. van Eulem and N. J. Pritchard for supplying the phosphate samples, and Th. J. Liefkens for his skillful assistance. RECEIVEDfor review March 11, 1974. Accepted April 29, 1974.
CORRECTION Thermometric Titration Determination of Hydroxide and Alumina in Bayer Process Solutions
This paper by Eric VanDalen and L. G. Ward [Anal. Chern., 45, 2248 (1973 I] contains two errors in the concentrations of the sodium aluminate solutions described on page 2249. In the Reagents section, the 10th word in the 13th line should read 4N and not 2N. In the caption for Figure 1, the 2nd line of the paragraph, "Titration Conditions," the 9th word should read 12 g/L, and not 24 g/l.
Spectrochemical Method for Determination of Tellurium in Geological Materials lrena Schoenfeld and Armand Berman Soreq Nuclear Research Centre, Yavne, Israel
Tellurium is known as an element with a very low Clarke value, i.e., a low mean concentration in the Earth's crust. It is commonly associated with other elements of the sulfur group, but it occurs at lower concentrations. Several values for Se and Te content in geological materials are given in Ref. ( I ) . The determination of tellurium at such low concentrations is difficult and involves indirect procedures consisting of the formation of colored complexes of tellurium, their extraction and photometric (2-4) or catalytic ( 5 ) determination. For small amounts of tellurium, these methods require preliminary tedious chemical separation and are subject to the interference of many elements. The purpose of the present work was to develop a spectrochemical method for the determination of tellurium in geological samples. The two standards, Sulphide-Ore 1 (McGill University, Canada) and Basalt BCR-1 ( U S . Geological Survey, Washington) were chosen as experimental materials, although tellurium had not been previously reported in analytical data for these ores (6-8). The presence of sulfur in Sulphide-Ore 1 and selenium in BCR-1 (9), however, indicated that tellurium may have been present, but remained undetected because of its low concentration and the insensitivity of the analytical methods hitherto used. Therefore, preliminary separation of tellurium by distillation in air was undertaken. Volatilization is an attractive method because it offers enrichment of trace elements without the use of additional reagents. At a temperature of about 900 OC, the vapor pressure of tellurium oxide is high enough to allow its collection at atmospheric pressure. ( I ) "Losler-Lange Geochemische Tabellen," VEB Deutscher Verlag fur
Grundstoffindustrie,Leipzig, 1965. p 190. C. 0. lngamells and E. E. Sandell, Microchem.J., 3, 3 (1959). J. Jankovsky and 0. Ksir, Talanta, 5, 238 (1960). K. L. Cheng, Talanta, 8, 301 (1961). A. E. Hubert, U.S. Geoi. Sun/. Prof, Pap., 750-8, 188 (1971). (6) G. R. Weber, Geochim. Cosmochim. Acta, 29, 229 (1965). (7) F. J. Flanagan, Geochim. Cosmochim. Acta, 31, 289 (1967). (8) N. M. Sine, W. 0. Taylor, G. R. Weber, and C. L. Lewis, Geochim. Cos(2) (3) (4) (5)
mochim. Acta, 33, 121 (1939). (9) A . 0. Brunfeld and E. Steinnes, Geochim. Cosrnochim. Acta, 31, 283 (1967).
1826
0
EXPERIMENTAL The analytical procedure consists of the separation and subsequent spectral determination of tellurium. Separation of Tellurium. The separation of T e is based on distillation, using the apparatus shown in Figure 1. The inner walls of the quartz condenser are first lined with graphite by pouring a suspension of 2 parts (by weight) Aquadag (Aqua Deflocculated Acheson Graphite, Acheson Colloids Corp., Port Huron, Mich.) in 3 parts water into the quartz tube, closed a t one end. After 1 minute, the tube is emptied and dried slowly by means of a stream of hot air, in order to obtain a thin uniform layer of graphite. I t was experimentally established that a thickness of 0.2-0.3 mg/cm2 graphite is the most suitable. The tube is then tightly closed with a pure graphite electrode and baked in a high temperature furnace (Type K25A) a t 450 "C for 4 hours. T h e weighed sample (1-10 grams) is placed in a quartz vessel, which is then sealed to the condenser. The entire device is heated a t 900 O C in an electric furnace. After 1 2 hours, the heating is interrupted, the quartz condenser is cut from the volatilization vessel, and the graphite is removed quantitatively from the condenser walls with a special quartz spatula. The graphite is weighed, ground in an agate mortar, and packed into the same electrode that served previously as a stopper. This electrode is then excited in a dc arc. Spectral Determination of Tellurium. The sample and synthetic standards are excited under conditions given in Table I. The standards are prepared by mixing pure graphite (Specpure Johnson Mathey) with adequate amounts of oxides of Te, Se, Cd, Zn, Hg, In, Ga, Sn, Sb, Bi, Ag, and T1-i.e., all the volatile elements that can be present in sulfide and quartz sulfide ores. Photometric measurements were made with a non-recording Jarrell-Ash microphotometer. The photographic emulsion, Ilford Q-2, sensitive to short-wave radiation was applied in order to make use of the most sensitive lines, T e I2385 8, and T e I2142 A. The intensities ratio of these two lines is given in Ref. ( I O ) as 1 and in Ref. ( 1 1 ) as 1.27; under our conditions the mean ratio, experimentally established, is 1.46. The shorter wavelength line is probably attenuated by the blaze angle of our spectrograph (-3000 8,);however, it has the advantage of being interference-free compared with the T e 12385.76 A line, which can be subject to Cr 12385.74 8, interference. The use of both lines permits more controlled results. Harrison, "Massachusetts Institute of Technology Wavelength Tables," Wiley, New York, N.Y., 1939. W. F. Meggers, C. H. Coriiss, and 6.F. Scribner, "Tables of SpectralLine Intensities," Nat. Bur. Stand. Monograph 32, Pt. 1, U.S. Govt. Printing Office,Washington, D.C.
(10) G. H. (11)
ANALYTICAL CHEMISTRY, VOL. 46, NO. 12. OCTOBER 1974
