ANALYTICAL CHEMISTRY
602 Table VII. Sample 1
2 3 4
Spectrographic Analysis of Fluid Cracking Catalyst in Absence and Presence of Strontium Kickel, 7% Chromium, % Vanadium, 70 _ _ _Sodium, _ _ _ _ 70 CalciiiriiL/L No Sr 0.8% Sr No Sr 0.8% Sr S o Sr 0.8% Sr S o Sr 0 85% Sr 0.8“; Sr 0.43 0.012 0.013 0.0037 0.0047 0.012 0.012 .... .... 0.03
Iron, 7% No Sr 0.8% Sr
0.41 0.26 0.73 0.32
0.26
0.70
0.32
~
0,0092 0.0075 0.0098
0,011
0.0070 0.011
0.0043 0.0023 0.0025
0.0041 0.0023 0.0030
spectrographic analyses of the same samples are compared; sets of replicate spectrographic determinations provide measures of the precision of these determinations. These data indicate for the spectrographic method an approximate precision based on the component of 5% for vanadium and chromium, 8% for iron, 12TC to1 nickel, and 16% for calcium and sodium, whereas the &,viatioris of spectrographic from chrmical results are approvimately 9% for iron, 5% ior chromium, 167’ for calcium and sodium, 22Y0 for nickel, and 30% for vanadium. During development of the preeent spectrographic method thr use of several spectral line pair combinations of the internal standards and sought elements were investigated. Cobalt, foi instance, was found unsatisfactory as an internal standard for calcium because of erratic intensity ratios among the varioui measured lines of these tm-o elements. The addition of strontium provides a satisfactory reference for calcium; but this element was found unsuitable for sodium. I n the development of the method it was considered highly desirable that all contaminants tie cietermined on the same spectrogram; but because the quantity of strontium added (0.8%) is much greater than the amounts of tht other internal standards, its possible interference in the determination of other elements was suspected. To clarify this point, plant samples were analvzed with and without strontium. The results shown in Table VI1 are typical, and reflect no significant influmcc. of strontium on determinations of the other elements. Fluid cracking catalysts supplied by commercial manufacturervary in alumina content from 10 to 20%, according to type. For N given type of catalyst this variation is probably never greater than 1 or 2%. The influence of alumina content on the determination of one element (iron) was investigated by spectrographic analr,i-
0.0040
0,013 0.0074
0.003s 0.012
0,0078
