a series of computations and thus ob-
I
tain s, more reliable x-ray answer for Si02 and CaO. Which approach is the more practical one obviously depends upon the accuracy requirements of a given laboratory. Regardless of which approach is taken, the work described clearly indicates that once the nonmetallic powdered sample is presented in the proper physicochemical form t o the x-ray beam it is possible t o get meaningful values for raw mix analysis. LITERATURE CITED
(1) Andermann, G., Pittsburgh Conference on Analytical Chemistry and
Applied Spectroscopy, Pittsburgh, Pa., 1959. (2) Andermann, G., Allen, J. D., Advances in X-Ray Analysis 4, 414 (1961). (3) Asdermann, G., Allen, J. D., ANAL. CHEM.33, 1695 (1961).
XI,No. 1 (1960). ( 7 ) Claisse, F., Quebec Dept. Mines Prog. Rept No. 327, 1956. ( 8 ) Croke. J. F.. Kilev. W. R.. Norelco Re tr. VI, NO. i (i955j. (9) &rleyj E. A., Am. SOC. Testing
(6) Ibid.,
.
I
Materials, Third Pacific Area Meeting,
S m Francisco, Calif., 1959.
45
50
60
55
65
Figure 12. Corrected C a O analysis with fused synthetic standards (4) Andermann, G., Jones, J. L., David-
son, E., Proc. Conf. Ind. A p p l . X-Ray Anal., 7th Denver 1958,215. (5) Applied Research Laboratories "Spectrographer's News Letter," VII, No. 3 (1954).
(10) Davidson, E., Gilkerson, A. W., Neuhaus, H., Pittsburgh Conference on -4nalytical Chemistry and Applied Spectroscopy, Pittsburgh, Pa., 1960. (11) Hasler, M. F., Kemp, J. W., Am. SOC. ~ O T Testing Materials, ASTM Committee E2, p. 81, Philadelphia, 1957. (12) Kemp, J. W., Andermann, G., Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, 1956. (13) Kester, B. E., AIEE Cement Industry Conf., Milwaukee, Wis., 1960. (14) U. S. Geol. Survey Bull. 980, Supt. of Documents, U. S. Printing Office, Washington, D. C. RECEIVEDfor review January 23, 1961. rlccepted August 2, 1961.
X-Ray Emission Analysis of Finished Cements GEORGE ANDERMANN' and JAMES D. ALLEN Applied Research Laboratories, Inc., Glendale, Calif,
b To date, the x-ray emission analysis of finished cements has been beset with the same difficulties as the analysis of cement raw mix. Although the gap between precision and accuracy has not been as great as with cement raw mix, for the most important constituents in finished cements, accuracy has not approached precision. The application of the previously described minimum flux (MF) technique has resulted in significant improvements in accuracy.
A
of the literature (3, 4 ) discloses that in recent years a t least two laboratories have been concerned with the s-ray analysis of finished cements. Prior to the disclosure of a fusion method the analysis was performed on briquetted samples. The samples in each case %-ere from the h'ational Bureau of Standards (NBS) X-1 through X-6 series. I n one case paraffin was added as a binder; in the other case no binder was used in the briquet-making process. The x-ray analyses from both laboratories were strikingly similar. The gap between instrumental precision and accuracy in the analysis of Si02 and CaO, the two most important constituents, was par-
50
40 v)
2
30 20
IO I I2
SURVEY
Present address, Austin and Robinson Laboratory, San Gabriel, Calif.
I 16
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I
20
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ATOMIC NUMBER
Figure 1.
(z)
Loss of net line intensity
ticularly significant. Since two different commercially available instruments were used, the similarity in the scatter of points only reemphasizes the need for realizing that in x-ray analysis accuracy rather than instrumental precision is the major problem. With the disclosure of the MF technique, a n attempt was made ( I , 2) to postulate that simply briquetting powdered materials may not be sufficient for the analysis of soft region elements because of the existence of mineralogical and micro inhomogeneity effects. The x-ray emission analysis of
finished cementswithout any specialsample treatment, however, should be and is a great deal more accurate than the analysis of cement raw mix. This is undoubtedly due t o the greater physicochemical similarity of the finished cement samples. This more favorable situation is brought about by the sintering and fusion processes occurring in the kiln. Nevertheless, since the process of fusion is incomplete in the kiln, and since CaSOl is mechanically mixed with the kiln product, some mineralogical and inhomogeneity effects are undoubtedly in existence. MINIMUM FLUX METHOD
Application to Finished Cements. T h e MF technique, using a fusion temperature of 2500" F. and Li2B40T as the flux, was unsuitable for finished cements because of the drastic and nonreproducible decomposition of Cas04 a t that temperature. Experiments were carried out to determine the fusion temperature a t which the most reproducible results, including SO3, could be obtained. Four temperatures were evaluated, one at 2000' F., above the decomposition point of CaSO4, and three below 1825" F. The lowest feasible fusion temperature was 1650" F. and the highest fusion temperature used below the decomposition point of pure CaSOd was 1800" F. The median temperature below the decomposition temperature-1725" F.-was also evaluated. VOL. 33, NO. 12, NOVEMBER 1961
1695
Table 1.
Optimum Selection
of Crystals, Slit
Widths, and Detectors For Elements
Analyzed
Element Sr Fe Mn
Line Ka Ka
Wave Length 0.877 1.937 2.104 2.750 3.360 5.373 6.155 7.126 8.338 9.889
Ka KQ Ka Ka Ka
Ti
Ca
S
P Si
Slit Widths (Inch) SecondCrystal Primary ary 0.030 LiF 0.015 LiF LiF 0.020 0.030 0.060 LiF 0.120 LiF NaCl EDT EDT 0.040 EDT 0.040 0.060 ADP 0.040 0.020
Al Mg
Ext. std.
Nondispersive Table 11.
Detector Multitron Multitron Multitron Multitron Multitron Minitron Minitron Minitron Minitron Minitron Multitron
Precision and Accuracy Data on Finished Cements
Fused (F) and unfused (UF) samples
Instrumental precision
0.053 0.11 0.069 0.11
(Si')
Total precision ( u t ) Mean error Av. dev. Concn. range 0
b 0
0.07 0.10 0 . 1 0 0 . 1 3 0.038 0.008 0.018 0.07 0 . 1 2 0 . 1 0 0.13 . . 0.024 0.020
.
0.075 0.0435 0.17 0.12" 0 . 4 3 0.12b 0.04O 0.081 0.043" 0.3-4 6 3.3-6.4 19.3-24.0 0 . 0 - 0 . 5 1.5-2.7
Uncorrected. Corrected for interelement effects. Corrected for Ca interference. Table 111.
Precision and Accuracy Data on Finished Cements
Fused (F) and unfused (UF) samples UF Instrumental precision (ui') Total precision (ut) Mean error Concn. range b c
CaO
TiOz, MnzOr, F F
F
FenOt UF F
SrO, F
0.040 0.084 0.004 0.001 0.009 0.013 0.0008 0.088 0 . 1 9 0.013 0.012 0 . 4 1 0.29" 0.008b 0.003b 0.059 0.04c O . b b i b 60.5-67.7 0.2-0.4 0 . 0 - 0 . 2 1.1-3.7 0 . 4
Corrected for dilution. Uncorrected. Corrected for interelement effects
.=I,
24
A
E X P (.005ql
24
23
23
i2 2 N 0
N 22
0
21
20
20 I
I
I
,
I
84
aa
92
96
Isi/I
I
1
I
44
46
48
IT
ES Figure 2.
Si02 analysis
Left. Before fusion Right. After fusion, corrected for matrix effects
1696
ANALYTICAL CHEMISTRY
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I
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52
The SO3 results were still poor at 2000" F., but were improved below the transition point. Of the three temperatures below the Cas04 decomposition point, 1725" F. appeared to be the most suitable in terms of reproducibility of the method and accuracy, not only for SOa, but also for CaO, SiOl, etc. Even though the fusion occurs below the decomposition temperature cited in the literature (8), there is an excessive loss of net line intensity (line above background) due to the fusion. The net line intensity loss for the various elements due to dilution and ignition losses is shown in Figure 1. Accordingly, the sulfur net line intensity should be about 45%. Actually, even at 1650" or 1725" F., the observed decrease in the sulfur net line intensity was about 58% indicating that even a t these relatively low temperatures a certain amount of decomposition was taking place in the fusion matrix. I n contradistinction t o the cement raw mix method ( I ) , which was based on a 1.5-minute fusion time, the 1725" F. fusion temperature required 5.0 minutes. In every other respect the method chosen was identical to the raw method. Similar to cement raw mix, small variations in fusion time, fusion temperature, and grinding time did not influence the results, whereas weighing errors were important.
Samples. T h e samples studied consisted of the six NBS standards X-1 through X-6, the X'BS standard No. 177, and five other very carefully analyzed standards. To obtain a before and after fusion comparison the samples were run in t h e unfused as well as t h e fused state. T o obtain a measure of the total precision, t h a t is. precision including instrumental and all other errors due to sample preparation and sample handling, duplicate briquets were made from each sample for both the fuspd and unfused states. Thus, a total of 48 briquets was investigated. Instrumentation. T h e instrument used in this investigation was the larger of the two Applied Research Laboratories vacuum polychromators-the vacuum production x-ray Quantometer-designated as the VPXQ. The V P X Q was used rather than the smaller vacuum x-ray Quantometer (VXQ), which has a more closely coupled sample-to-x-ray tube target distance, because of the number of elements deemed to be desirable for analysis in finished cements. The principles of design and operation of the VPXQ have been discussed by Davidson, Gilkerson, and Neuhaus ( 5 ) . However, for applications where the analysis of MgO, AlzOa, SiOe, CaO, SOaJ and Fe,Ol is sufficient, the VXQ would be more suitable because of its closer coupling and thus relatively higher speed. The difference in speed between the two instruments is approximately two.
The ten elements analyzed in this program are shown in Table I. This table also shows the selection of crystals, slit widths, and detector types for optimum performance for each of the elements. For example, a NaC1 crystal is used for sulfur determination rather than a n EDdT (ethylenediamine Dtartrate) crystal because of the difference in their reflectivity, since KaC1 provides about ten times more intensity than EDdT. Table I also shows that a n external standard (ES) ( 1 ) was used to monitor the x-ray source. The optimizing of slit widths is best illustrated in the case of phosphorus determination. The determination of PzOj in the concentration range of 0.05 to 0.50% PzOjand in the presence of 60 to 67% CaO is perhaps one of the most difficult determinations in the soft region due to the interference from second-order Ca lines. Specifically, the P Kcu line is a t 6.155 A , ,the weak secondorder Ca KPj line is a t 6.148 A., and the relatively strong second-order Ca KO1 line is a t 6.178 A. Using an EDdT crystal i t is impossible to eliminate the second-order contribution from the weaker Ca Kfi line. On the other hand, by using relatively narrow slits such as 0.020 inch for the primary and 0.020 inch for the secondary. curved crystal optics permit almost complete resolution of P Kcu from Ca Kpl X 2. Furthermore the wave length shift in going from P-j (phosphate sample) to Po (elemental phosphorus sample) as determined in the author’s laboratory is as much as +.0028 A. Thus, it is extremely important that the monochromator be peaked using a phosphate sample in order not to obtain any unnecessary “wing” contribution from the Ca Kpl X 2 line.
v i = [Zd2/2(n
- I)]”*[vz]
66
33 O J
32
64
e
0
6.N
a-0 62
31
150
160
170
180
116
Figure 3.
120
124
128
132
CaO analysis
left. Before fusion Right. After fusion, corrected for ignition loss
duplicate readings on the same briquet n = number of briquets m = slope (yoconstituent/unit of intensity) The calculated values of standard deviation of a 5-minute exposure (ui’) were obtained by utilizing the square root relationship, ui’ = ui/
