1416
ANALYTICAL CHEMISTRY
mination on the x-ray unit and the sample was recovered after each run. The amounts of calcium fluoride added to the dust samples varied from 0.12 (for the smallest sample of dust) to 1.71 grams (for the largest sample of dust). After adding the internal standard, the dust samples were tightly stoppered and revolved on a mixing wheel for 24 hours. It was unnecessary to resort to ball-mill methods for mixing or grinding.
Table 111. Analysis of Set I1 of Air-Borne Dust Samples from Foundry Sample No. z-1
Quartz,
7%
24.3 19.6 19.6 33.8 6.3 35.7 79.4
2-2 2-3 2-4 2-5 Z-6
E-%
e-9'
z-10 z-11 z-125 Z-135 2-14 Z-15a Z-16
a
Cu. Ft. Air Mg. Quartz Mg. Quartz/ Sampled/Min. Collected/Min. Cu. Ft. Sampled 67.1 20.8 0.309 80.1 5.53 0 .0690 82.1 2.01 0.0245 69.9 34.3 0.491 68.4 1.91 0.079 59.1 2.42 0.0409 66.4 43.8 0 . 660
....
....
35:s 51.7
7213 65.2
6.36 5.21
n.0880 0.0799
ca. i : 3
62:7
0,694
0.0111
i:7
6212
0,399
0.0641
..
..
.... .... ....
.... .... ....
Volume of sample not large enough for technique of analysis.
X-Ray Analysis of Dust Samples. The sample holders were packed in the same manner as were the standard series samples, after the dust samples had been reduced to suitable size, if necessary, by the quadrant method. The diffractometers were operated in the same manner as before. The first set of samples (21-216, Rl-R4) collected in 1952 from the areas indicated in
Figure 1 were analyzed with the Norelco diffractometer and the working curve I in Figure 2 was used to read off the percentages of quartz from the corrected intensity ratios, I Q / I ~ . These data are assembled in Table I1 together with the grams of quartz collected per hour. The second set of samples was collected in 1953 by a much improved method (Visi-Float), employing standard concentric ring paper filters, and was analyzed with the General Electric diffractometer. The quartz content read off from the working curve I1 in Figure 2. These data are assembled in Table I11 together with the cubic feet of air sampled per minute and the milligrams of quartz per minute and per cubic foot. Again it is emphasized that two sets of dust samples collected by two different methods a year apart, but in approximately the same foundry areas, were analyzed with two different diffractometers by two different observers using two different methods of measuring and correcting intensities of diffraction lines. Except for the direct experimental comparison of standard samples, indicating systematically higher values by the second technique, the data on dust comparison are consistent within each group but can give only approximately the change in the dust picture in the foundry during the course of a year. Samples R-1, R-2, R-3, and R-4 were hand-collected from places where dust had settled in rather large amounts. These samples contained up to 100 grams of dust. The dusts as received were placed in a Patterson-Kelley twin-shelled blender and mixed for 1 hour. The shell of the blender is of the V-type design which splits the sample and then recombines it every time the blender rotates. After homogenization, a portion of the dusts was ground until it all passed a 250-mesh screen. The dust was then weighed to the nearest milligram on an analytical balance and the proper amount of calcium fluoride was added as before. The dust and calcium fluoride were placed in I-ounce screw-capped bottles, placed on a mechanical mixer, and mixed for 4 hours.
(X-RAY ANALYSIS OF FOUNDRY DUSTS)
Fluorescent Spectral Analysis for Iron G. L. CLARK and H. C. TERFORD' Department o f Chemistry end Chemical Engineering, university o f Illinois, Urbana,
T
HERE has never been certain evidence of metallic iron or any of its crystalline compounds in the diffraction patterns of dusts even where 30% or more of the element is present. Because of the importance of iron determinations in foundry dusts in the diagnosis of siderosis, as contrasted with silicosis, and because of the extremely laborious and unsatisfactory analysis by most chemical methods (requiring fusions to get silicates into solution), recourse must be taken to fluorescent-spectral analysis. This is done with the same General Electric Geiger unit aa employed for quantitative diffraction analysis for a-quartz. 1
Present address, Shell Chemical Co., Houston, Tex.
111. APPARATUS
The General Electric SPG fluorescent spectrometer was used with the XRD-3 x-ray diffraction unit. The Machlett AEG-50 tungsten tube was operated a t 50 kv. and 50 ma. The fluorescent radiation was analyzed by diffraction through a mica crystal 0.0013 inch thick and defined by a 0.3" detector slit before the Geiger tube. The sample holder was of '/(-inch aluminum stock in which a cavity of I-inch diameter and 1/,-inch depth had been machined. When the holder was positioned in the sample drawer the sample completely covered the hole of the aluminum mask which defines the irradiated area. CALIBRATION CURVE
Table IV.
Composition of Standard Samples
SiOn, CaFn', Fe, G. G. % 1 3.792 0.948 1 3.696 0,924 2 3 0.900 5 3 3.600 4 0.880 3.552 6 0.852 5 3.408 9 6 0,600 0.840 1.200 3.360 10 7 0,900 1,200 3.120 0.780 15 0 The dust sample8 to be analyzed contained .20% CaF? which ,had been sdded as internal standard for the quartz determination by x-ray diffraction. Later work has proved that nickel as powdered metal or pure salts 8erves sa a satisfactory internal standard for both the diffraction and spectral snalraes. Sample
No.
Fe, G. 0.060 0.180 0.300 0.360 0.540
Ni, G. 1,200 i.2m 1.200 1.200 1,200
The calibration curve was established by plotting the ratio of the intensity of the iron K a to that of the nickel K a as a function of composition as determined from standard homogeneous samples of known composition. Table IV shows the composition of the standard samples, the constituents of which were passed through a 250-mesh sieve, weighed, and mixed for 2 hours in a Patterson-Kelley twin-shelled blender. The peak intensities of the iron K a and nickel Ka were scaled and the background for each was determined by scaling 2' on each side of the peak and taking the average value as background. The ratio of net intensities above background, I(FeKa)/
V O L U M E 26, NO. 9, S E P T E M B E R 1 9 5 4
1417
Z(NiKa), was considered the true variable as a function of composition. Standard samples 2, 4, and 5 were run in triplicate to test the effect of sample density on the intensity ratio. A different portion of the sample was packed in the holder each time and the surface carefully leveled with respect to the plane of the holder. The weight of sample was determined by difference from the weight of the holder before and after packing. From the results tabulated in Table V, the intensity ratio appeared to be essentially independent of the sample density.
as a linear regression of intensity ratio on iron concentration and an analysis of variance was made. The two requirements necessary for such an analysis are met-homogeneity of variance of intensity ratio replication exists and the variance of iron concentration is negligible relative to that of intensity ratio.
Table VII. Reproducibility.of Method in an Analysis of Variance Errora About regression Within replications Total
I-
15
Degrees of Freedom 5 6
Sum of Squares 0.00163
11
0.00167 0.00320
Mean Squareb ( I ratio) 0,00031 0,00028 Av. 0,00029
Std. Error&, % Fe 0.22 0.22
FC 0.92 0.92
The error about regression represents deviations from linearity. The error within replications represents errors not attributable to changes, in iron concentration. The total error includes both of the aforementioned errors and best represents the error in a determination in which a linear relationship is assumed for the data. b The mean squares are variance estimates, Sz or u2, for intensity ratios. C The F value compares deviations from linearity with deviations within replications, a high F value indicating nonlinearity. d Standard error, S or u, is given in units of per cent Fe.
ANALYSIS OF FOUNDRY DUSTS
5
IO PERCENT
15
~
IRON
Figure 3. Working Calibration Curve for Quantitative Determination of Iron in Dust Samples by Fluorescent Spectrometry I F s K u / I X i K u Ratio of intensities of F e K a fluorescent ray t o intensity
of NiKu ray used as internal standard
Table VI lists the intensity ratios obtained for the series of standard samples. The calibration curve plotted from these data is given in Figure 3.
Sufficient powdered metallic nickel was added to each sample to make the final composition 20% nickel and the mixture was blended for 2 hours. The samples were irradiated under the operating conditions used for the standard series. The intensity ratios, I(FeKa)/Z( S i K a ) , were determined and converted to per cent iron from the calibration curve. Table VI11 gives the per cent iron determined for the eleven foundry dusts available for this analysis together with the quartz content determined by x-ray diffraction (from Table 111). The quartz and iron contents of the dusts are roughly inversely related, high quartz and low iron and vice versa. The iron percentages vary from 30.21% for a rafter sample R-4 down to 1.87%
Table VIII. Iron and Quartz Content of the Foundry Dusts Analyzed (Set 11) Sample
REPRODUCIBILITY OF METHOD
Table VI1 gives a statistical summary of the reproducibility of the method and adherence to linearity. The data were treated
Table V. Effect of Sample Density on Ratio of Intensities Std. Sample NO.
Fe, 70
2
3
4
6
5
9
Wt. Sample Irradiated, G. 1.277 1,426 1.703 1.126 1.494 1.791 1,209 1.447 1.673
I(FeKa)/ Z(NiKa) 0.237 0.219 0.217 0.425 0.444 0.431 0.695 0.645 0.656
No.
I(NiKa)
2-1 2-2 2-3 2-4 2-5 2-8 2-11 R-1 R-2 R-3 R-4
0.631 0.176 0.260 0.221 0.216 0.107 0.569 0.180 0.493 0 088 1.451
Table IX.
1 1 2 3 3 5 4 6 Average of triplicates.
0,067 0,2240 0.363 0.433O
5 6 7
..
9 10 15
..
0,6650 0.756 1.154
...
Fe, %. In Orig. Dust Sample 13.19 3.77 5.51 4.69 4.34 2.20 11.92 3.81 10.30 1 87 30.21
Quartz,
%
24.3 19.6 19 6 33.8 6.3 79.4 51.7 37.7 63.1 81.2 16.2
Per Cent Iron in Dust Samples (Set I )
Sample
Z-1 2-2 2-3 2-4 2-5 2-6
2-7 2-8 2-9
Table VI. Standard Samples and Corresponding Intensity Ratios
Fe, %, from Calib. Curve 8.45 2.40 3.52 3.00 2.81 1.39 7.60 2.45 6.64 1.20 19.36
2-10 2-11 2-12 2-13 2-14 2-15 2-16 R-1 R-2 R-3 R-4 a Brown color was very dark. b Brown color was very light.
Color Broarn Black Black Black Black Black Gray Black Black Brown Browna Gray Black Brown Brown Brownb Black Black Black Black
Iron, % 1.2 0.5 None Trace None None None Trace Trace 2.5 3.6 None 0.1 0.5 2.7 2.0 2.1 0.4
1.5 10.1
1418
ANALYTICAL CHEMISTRY
for another rafter sample R-3 (see Figure 1 for the foundry layout). The collected Visi-Float samples vary from 13.19% for Z-1 to 2.20% for 2-8. A notable exception to the inverse relationship is sample 2-5 from the core sand mill with 4.34% iron and 6.3% quartz. For set I of the dust samples whose quartz contents are tabulated in Table 11, chemical analyses were attempted. There were differences in color of the samples: the predominant color was black, with several appearing brown. Spot tests were performed on all 20 samples and those that appeared gray (as
received from the foundry) showed no presence of iron; some of black indicated iron and others did not. Table I X indicates the amount of iron found in each sample. Since the spot tests indicated the presence of both ferrous and ferric iron, it was necessary to reduce the iron completely to the ferrous state and then determine the per cent iron by cerate oxidimetry using o-phenanthroline as an indicator. The chemical analyses give considerably lower results than the carefully calibrated fluorescent-spectral analyses, even though two sets of dust samples are involved.
(X-RAY ANALYSIS OF FOUNDRY DUSTS)
Interpretation of Results and Correlated Medical Observations G. L. CLARK,
Department o f Chemistry and Chemical Engineering, University o f Illinois, Urbana,
L. E. HOLLY, Muskegon,
111.
Mich.
T
HIS is the first time a university laboratory has cooperated closely in the quantitative correlation of the health hazard problems of a large representative steel foundry. I t has been possible to study the hazard itself in regard to each of the functions carried out in designated areas of the foundry, correlrting this information with the data on dust concentration and constitution and with medical applications. The medical application has been made possible by making use of information obtainable from periodic chest x-rays of the foundry personnel under the direction of an eminent radiologist. As workers have been employed in their present operations at the foundry for an average of 20 years, this enables information to be applied to recommendations for future hazard control. Excessive inhalation of silica dust generally produces a seriouy pulmonary disease. For some reason, yet unexplained, silicon dioxide as quartz may produce a diarhling form of lung fibrosis. The American definition ( 2 j of silicosis states: I t is a disease due to breathing air containing silica (SiO?) characterized anatomically by generalized fibrotic changes and the development of miliary nodulation in both lungs, and clinically by shortness of breath, decreased chest expansion, lessened capacity for work, absence of fever. . .
The Journal of the American .lIedical .4ssociation ( h i states that: Only silica (Sios) is capable of inducing silicosis but any other mineral dust under conditions of prolonged exposure and gross exposure may cause some increase in pulmonary fibrosis. If the relative potential harm of silica is rated as 100, these other nontoxic mineral dusts may be rated only on the order of 5 and 10. Moreover, the fibrosis is in itself not pathognomonic, since many other dusts, alkalies, acids, or vapors may induce somewhat eimilar if not identical x-ray markings. I n general, the damage done in silicosis is permanent; an unalterable tissue change takes place in the lungs. Deaths from uncomplicated lung fibrosis caused by dust are infrequent (d), but susceptibility to tuberculoais, pneumonia, and other respiratory diseases is known to be greatly increased. The mechanism of the action of silicon dioxide in producing silicosis is the formation of silicic acid when silicon dioxide comes in contact with body fluids. The silicic acid so produced seems to be the causative agent in nodule formation. Another theory is based on the piezoelectric properties of crystalline quartz as compared with silicates which are essentially amorphous and do not possess similar electrical characteristics. The length of exposure that will produce silicosis varies with the working conditions and individual susceptibility (6). Thus rapid and accurate methods of dust analysis are needed to study working conditions.
The practice a t the foundry is to employ aluminum powder inhalation for preventing silicosis. This is on a voluntary basis and is not a substitute for good housekeeping. The mechanism is thought to be the formation of aluminum hydroxide which neutralizes the silicic acid and thus prevents the formation of the silicotic nodule. Sone of the oxides of iron, or fine iron dust, in themselves, have been shown to be dangerous upon inhalation into the lungs, although the lungs of men who have been exposed to the iron dusts are colored characteristically and are called siderotic, and an x-ray chest film may show changes confused with silicosip. Perhaps t'he most significant observation of this investigation is that in areas where there is little or no concentration of quartz, x-ray photographs of the chests of workers show progressive changes. This can be explained in part by the fact that in areas of l o a or no concentration of quartz, there is usually a fair concentration of iron, which can be present as finely divided metallic iron, oxides, carbonates, and possible silicates of iron. Ihidences of crystalline iron and its compounds are rarely found in the diffraction patterns of dusts, indicating very low concentrations or essentially amorphous or colloidally dispersed phases. Iron, being of relatively high atomic weight, will produce shadows in small concentrations (siderosis). Iron probably undergoes hydration on the moist lung tissue to form a gelatinous colloid and this in turn very slowly forms innocuous iron silicates. There is no evidence that iron is antidotal to silicosis when injected in vivo, although aluminum dust does have this action. Unfortunately, data on siderosis are extremely fragmentary. Inspection of Figure 1shows that the working or actual foundry areas in which pollution of air by dusts is a problem of industrial hazard have been grouped into a number of larger zones labeled 4 through H , inclusive. Zone A includes the areas from which samples 2-2, 2-3, 2-4, and R-1 were collected. 2-2 is an area in which three sand mills are located; 2-3 is the small ladle repair area; and sample 2-4 was collected a t the breathing level near the crane over the double shakeout, Sample R-1 was taken from the rafter in the main bay over the double shakeout, in the same area as 2-4. The types of jobs in Zone A include bench molding, squeeze molding, pin lift molding, a small bumper, small floor molder shakeout, skimmers, pourers, crane operators, small ladle liner, sandmill operator, carryout, and supervisors. From Tables I1 and I11 it is found that a significant amount of or-quartz was found in the dust from areas 2-2, 2-3, and 2-4. 2-4 is considered the most hazardous zone, and this sample was collected from the breathing level. A significant amount (25.5 and 33.8%) of quartz was found in the rafter sample taken from area 2-4. I n Zone A , there has been a record of 14 cases of distinct silicotic nodulation in the lungs to date.
