Document JJV18Y58nKX8ZpM9a2NqbJd2a

SCHMELZER--X-RAY DIFFRACTION-INDUSTRIAL DUSTS 127 1 careful control of grinding time and particle size appears to have rectified these inaccuracies and given good results, although calcite appears to show high absorption in the low quartz ranges. Errors as high as 50 per cent were found in some of these instances. Reproducibility was found to be in the magnitude of 1 per cent. Table 2.--Comparison of Chemical and X-Ray Results from a Series of Routine Samples Sample HaSiFo Results, Quartz, % * A'lvay uQbUlts, / 1 --------- .A.___~_______________--______ Quartz, % Initial Analysis Check Analysis 856.................................................... 3.1 2.8 857 .................................................... 2.6 13.0 1.9 858.................................................... 55.0 51.3 859................ :.................................. 44.0 42.3 862.................................................... 11.4 19.0 12.6 868..-................................................ 16.8 28.0 22.6 907.................................................... 3.25 8.4 4.5 908.................................................... Nil 0.9 * Initial chemical analyses were performed using reasonable care in a routine manner; check results were obtained using extreme care and unlimited time. Table 3.--Comparison of Results of Quarts Determinations Made on Dust Samples by Various Laboratories * Sample 811........................ .................... 812........................ .................... 813....................... ........... :.... 814....................... .................... 816........................ ................................... 817......................................... ................................... 818......................................... ................................... 819......................................... ................................... 820......................................... 821......................................... 822......................................... ................................... 823......................................... ................................... 824 ................................. 825......................................... 826......................................... 827...'.................. 828........................ 829........................ 830........................ 831........................ 832................ . 833........................ 834........................ Los Angeles City Laboratory A HaSiPe % HaPOj % 36 31 43 37 28 23 26 17 17 25 24 27 25 19 13 27 25 31 29 28 37 19 25 25 21 38 11 25 21 16 U. S. Public Health Service 'A Chemical X-Ray %% 23 17 32 33 19 20 18 20 16 15 22 19 26 21 24 27 3 .6 14 9 21 20 25. 24 26 21 31 25 15 12 14 22 17 17 18 32 27 99 21 19 13 14 18 11 California Bureau of Adult Health X-Ray % 16.3 30.8 23.8 19.2 15.6 21.5 28.8 29.6 11.6 11.7 25.6 24.4 19.4 28.8 17.9 10.9 21.0 19.6 30.8 10.9 22.2 18.2 18.2 * Los Angeles Oity Laboratory results were obtained by the Knopf (IhSiFo) method and a modified Durkan (H3POO method. The United States Public Health Service chemical results were obtained by a modified phosphoric acid method:-The values indicate the quartz percentages found. The Bureau of Adult Health results, while shown to three significant figures, would normally be reported to two significant figures. A number of dust samples that had been analyzed by the hydrofluosilicic acid method were subjected to x-ray analysis. In some cases the x-ray results, although reproducible, were grossly at variance with the chemical results (table 2). Sub sequent reanalysis by the chemical method showed much better agreement. This seems to indicate that the hydrofluosilicic acid method, long a standard in many