ported values, which have been corrected for the residual impurities present in the carbonyl nickel powder used for the dilution of the standard. Some of the data could not be included because of cobalt interferences in firstand second-order spectra as a result of the high cobalt content of the NBS nickel oxide. I n addition, a sample of nickel sheet was analyzed for iron and silicon by the thiocyanate and silicomolybdate spectrophotometric methods, respectively, and a comparison \i-ith spectrographic results is included in Table IT’. The precision data were obtained on differmt days, on different photographic plates, using the same standard sample. I n these tables each determination is the result of 1 run. The results shon a precision of *207& n-hich is typical for direct current spectrographic methods. The increased sensitivity of the method over previous spectrographic methods provides for the better evaluation of trace impurities in high purity nickel, and the accuracy and precision attained are adequate for this purpose.
Table 111.
Analysis of NBS Standard Nickel Oxide No. 672 Diluted with Carbonyl Nickel Powder
Element .4l
Amount Present in Standard, P .P. M .a 5.4
c
1Ig
20
1111
9.7 30
Error, yo
Coefficient ot Variation, C;rc
+29 +23
12
5.4
2.1 2.2
cu
a
Amount Found, P.P.h4.b 2.7 2.7 16
2.0
- 20
++ 1013
2.2 11
Si +17 35 Corrected for rcsidual impurities present in nickel p o n d e r iised as diluent. Average of foiir determinations Coefficients of variation nerc calculated as follows:
u=loo c
6.3 14 15 15 11
ti” n - 1
where c
= average concentration, p.p.m. d = difference of deterniination from mean, p.1i.m. n = niimher of determinations
Table IV.
Comparison of Spectrographic and Chemical Analyses
Concentration, P.P.RI. Chemical Spectrographica 27 27 Si 20 18 a Average of 1 1 determinations. * See footnote in Table 111. Element Fe
Error, 7c 0
- 10
Coefficient of Variation, ycb 16 20
ACKNOWLEDGMENT
The authors gratefully acknowledge the valuable assistance of R. G. Everett and R. P. TYeberling in performing many of the analyses. LITERATURE CITED
(l),Feldman, C., in i‘lIethods for Emission Spectrochemical Analysis,”
Am. Soc. Testing llaterials, Philadelphia, Pa., 1953. ( 2 ) . Jayeox, E. I
