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1D r • prepared for AAS analysis by dissolving 2 grams of CKD sample in a mixture of 10 ml concentrated HNO3, S m1 HF, and 40 ml distilled H2O. The sample was evap- orated to dryness. The dried sample was redissolved in 5 vol-pct HN03 to which 5 ml of 30-pc[ H2O2 was added. The solution was gently heated and, after the H2O2 reaction had subsided, 5 to 10 m1 of concentrated HC1 was added to dissolve the remaining solids. The samples were cooled and transferred to volumetric flasks for AAS analysis. Arsenic and antimony were determined by a reliable graphite furnace AAS me [hod developed by the Bureau of Mines (6, 9). Mercury was determined using the method of Agemian and Chau (1) as modified by Haynes (9). Duplicate analyses were performed on all CKD samples. To verify the results obtained by chemical dissolutions, the flame AAS procedure, and other proce- dures used in this report, a National Bureau of Standards (NBS) Standard Reference Material (SRM) cement stand- ard, SRM-637, was analyzed, and these values were compared with certificate results. The results are listed in table 5 and show good agreement between certified values and values obtained by the methods used in this study. The results Eor the major and minor element concentration [arbitrarily chosen as greater than 0.05 wt-pct (500 µg/g)] are given in table 6. Table 7 gives the trace element concentration [arbitrarily selected as less than 0.05 we-pct (500 µg/g)]. Also listed in table 7 are seven elements, and their detection Limits, that were not detected by flame atomic absorption in any of the samples. Twen- ty-eight elements were examined in ail of the samples. Thallium was detected in only one sample, at l85 Vg/g. The presence of thallium in sample 9, as determined by flame AAS, was verified by fluorescent X-ray spectrography and optical emission spectroscopic techni- ques. • TABLE S. - Comparison of NBS SRM-631 certificate values with Bureau of Mines analytical method values, wt-pct ration I Cert ttt value CaO...... 65.8 66.0 Si02..... 23.2 23.0(7) A1203.... 3.15 3.2(8) Fe203.... 1.72 1.80 SO3...... 2.28 2.3(8) MgO...... .62 .6(7) K20...... .22 .25 Ti02..... .21 .21 Na20..... .l3 .15 SrO...... .08 .09 Py05..... .22 .24 Mn20g.... .06 .06 F........ .04 .04 ZnO...... .O1 .O1 Cr~Oq.... .O1 .01 1Parentheses indicate estimated level by NBS of next digit. Table 8 lists the range, arithmetic mean, and median found for each element in the 113 CKD samples. Ranges over three orders of magnitude are seen for same elements. The median may indicate the most probable value far the CKD samples where an anomalously high or low value Eor an element was found in one of the samples. Except for Ca, Ni, and Si, the median is tower than the mean Eor each element, indicating that the high concentrations are less frequent than the lower concentrations. Because traces of mercury were leached Erom only a few samples by the F,P toxicity test, these samples and a Eew additional samples were chosen co insure an adequate geographic representation of the planes in the United States. Table 9 gives the results of analysis of L6 samples chosen by the above procedure. Mercury was determined by standard cold vapor AAS procedures (1, 9). - - i t r~~i irrwew