A Spectrographic Method 

for Determining the 

Hafnium-Zirconium 

Ratio in Zircon

GEOLOGICAL SURVEY BULLETIN 1036-F

This report concerns work done on behalf 

of the U. S. Atomic Energy Commission 

and is published with the permission of 

the Commission

A Spectrographic Method 

for Determining the 

Hafnium-Zirconium 

Ratio in Zircon

By C. L. WARING and H. W. WORTHING

A CONTRIBUTION TO GEOCHEMISTRY

GEOLOGICAL SURVEY BULLETIN 1036-F

This report concerns work done on behalf 

of the U. S. Atomic Energy Commission 

and is published with the permission of 

ihe Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1956
UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U. S. Government Printing Office 

Washington 25, D. G. - Price 15 cents (paper covert
CONTENTS

Page

Abstract ______________________________ 81

Introduction and acknowledgments ___________ 81

Standards_______________________________ _ 82

Experimental data______________________________________ 83

Evaluation of results.____________________________________ 87

Reproducibility of results________________________________________ 88

Literature cited,_______________________ __ 90

ILLUSTRATIONS

Page

Figure 14. Working curve of hafnium-zirconium ratio in zircon_______ 84

15. Hafnium working curve_______________________________ 84

16. Zirconium working curve______________________________ 86

m

A CONTRIBUTION TO GEOCHEMISTRY

A SPEGTROGRAPHIG METHOD FOR DETERMINING 

THE HAFNIUM-ZIRCONIUM RATIO IN ZIRCON

By C. L. WARING and H. W. WORTHING

ABSTRACT

To develop a rapid spectrographic method for the determination of hafnium, 

the hafnium-zirconium ratio, and percentage of zirconium in the mineral .zircon, 

the ratio was determined first by plotting the log of the intensity ratios against 

the log of the hafnium-zirconium ratio by weight of the standards, using -zirconium as an internal standard (zirconium 2761.911 A and hafnium 2641.406 A 

or zirconium 2761.911 A and hafnium 2820.224 A). Straight-line curves were 

produced when the line pairs zirconium 2538.405 A and hafnium 2641.406 A were 

used in a similar manner for the hafnium determinations. After the liafniumzirconium ratios and the hafnium percentages were determined, the zirconium 

percentages were determined arithmetically and some were checked by direct 

spectrographic analysis. When chemical methods were used to check the 

spectrographic hafnium and zirconium totals, an average spread of 0.14 was 

obeserved. The results indicated an average accuracy of 3 percent of the hafnium 

present in the range of 0.5 to 2.0 percent, and 0.6 percent for zirconium in the 43 

to 58 percent range.

INTRODUCTION AND ACKNOWLEDGMENTS

In connection with a study of the radioactivity and geochemistry 

of minerals, rocks, and ores, a rapid spectrographic method was 

developed for the determination of the hafnium percentage, the 

hafnium-zirconium ratio, and the percentage of zirconium in the 

mineral zircon. The mineral samples were highly purified and had 

hafnium contents ranging from 0.1 percent to several percent; the 

zirconium ranged from 43 to 58 percent.

The published spectrographic methods for determining the percentage of hafnium and the hafnium-zirconium ratio have been 

reviewed by Ahrens (1950 p. 191-193). Many of these methods are 

applicable to rocks containing small amounts of zirconium and 

hafnium, after chemical concentration of these elements. The 

excellent method described by Mortimore and Noble (1953) was 

unsuitable for the complete problem at hand because the hafniumzirconium ratio was not included. Besides, the analysis of zirconium 

for hafnium with little or no silicon present and that of zircon with 

approximately 30 percent silicon would present different problems.

81
82 CONTRIBUTIONS TO GEOCHEMISTRY

The solution technique of Feldman (1949) was not suitable as a rapid 

method for determining hafnium and the hafnium-zirconium ratio 

because of the time and difficulty involved in dissolving the samples 

and preparing special electrodes. The method described by Fassel 

and Anderson (1950) also was not suitable to our problem because 

pure zirconium and pure hafnium oxide mixtures were used in pellet 

form. Our problem was to develop a rapid method (not including a 

pellet step) for the zircon mineral containing 30 percent silicon dioxide plus other impurities.

The method described here consists of arcing (d-c) to completion 

1 mg of the solid sample and the synthetic standards, mixed with 

three parts by weight of spectrographically pure graphite, processing 

the plate, obtaining the intensities of selected hafnium and zirconium 

lines by means of the densitometer, preparing percentage and 

emulsion calibration curves, and calculating the results.

The method as described is not applicable to rock samples containing small amounts of zirconium. The sensitivity of hafnium is approximately 0.01 percent and would not be detected in samples of 

lower zirconium content. It would be necessary either to separate 

the zirconium-containing minerals from the rock in order to apply 

the method or to improve the method in such a way as to increase 

the detection limit of the hafnium. Additional development work 

would be necessary to adjust the method to include the hafnium and 

hafnium-zirconium ratio of most rock samples.

The authors appreciate the help of then* associates of the U. S. 

Geological Survey: Harry Levine and Koberta Smith made the 

chemical analyses, C. S. Annell prepared the pure silicon dioxide, 

K. Valentine did the semiquantitative spectrographic analysis of the 

chemical precipitates, and E. S. Larsen, Jr., and David Gottfried 

provided the samples. This study is part of a program conducted by 

the Geological Survey on behalf of the Division of Kaw Materials of 

the U. S. Atomic Energy Commission.

STANDARDS

The chemicals used in preparing the synthetic standards were 

Specpure grade. The zirconium content of the hafnium oxide was 

certified as 1.5 percent. According to the manufacturer's directions 

for using the spectrographically standardized hafnium oxide for the 

determination of the zirconium content, a small portion of the sample 

was added to pure titanium dioxide. The zirconium was then determined quantitatively as a minor constituent in the titanium dioxide. 

The percentage of zirconium was confirmed by the U. S. Geological 

Survey laboratory by using as a standard the oxide of pure zirconium
DETERMINATION OF HAFNIUM-ZIRCONIUM RATIO 83

metal (40 ppm hafnium, 800 ppm iron, 40 ppm nitgrogen, remainder 

zirconium) supplied by the U. S. Bureau of Mines, Albany, Oreg.

A method of addition and extrapolation similar to that of Pierce 

and Nachtrieb (1941) was applied to the zirconium oxide to determine 

the hafnium content. Many tests were run and the average taken to 

establish the percentage of hafnium in the zirconium oxide as 0.1 

percent. This result compared favorably with the one obtained by 

the semiquantitative method (Waring and Annell, 1953) which is 

based on standard plates prepared with Specpure chemicals and which 

has been used in the Geological Survey laboratory for the past four 

years.

The silicon dioxide was prepared from silica plate, heated to 600° C, 

cooled quickly to fracture, ground to 100+ mesh, leached in aqua 

regia, and washed with distilled water.

Standards were prepared by adding known amounts of iron, aluminum, calcium, and hafnium oxides to a mixture of 67 percent zirconium 

dioxide and 30 percent silicon dioxide. Iron, aluminum, and calcium 

were known to be present in highly purified zircon samples from the 

previous work of Larsen, Waring, and Berman (1953). The amount 

of the three oxides added to the standards varied according to the 

hafnium oxide, thus making the total percentage equal to 100 percent. 

The mixtures were ground in a boron carbide mortar to pass 100-mesh 

stainless-steel screen. For more thorough mixing, the standards 

were passed repeatedly through 80-mesh stainless-steel screen. Six 

standards were prepared with hafnium contents of 0.2, 0.5, 1.0, 1.5, 

2.0, and 2.5 percent, after corrections for the hafnium originally 

present in the zirconium oxide.

EXPERIMENTAL DATA

The usual procedure here is to consume at least 10 mg of sample in 

the arc for quantitative work. To consume completely this amount 

of the zircon mineral required a long period of burning because of the 

refractory nature of the zirconium. The long burning time of the 

10 mg sample resulted in excessive background. It was later established that results obtained by incomplete burns were low as compared 

to the zirconium-hafnium totals given by chemical analysis. Additional tests showed that 1 mg of the sample mixed with three parts 

by weight of spectrographically pure graphite were completely consumed in the d-c arc in 180 seconds using a current of 12 amperes. 

We found, as Feldman (1949) did, that the log of the intensity ratios 

plotted against the log of the hafnium-zirconium ratios by weight of 

either of two line pairs of the standards produced straight-line curves 

that were considered satisfactory for detennining the concentration
84 CONTRIBUTIONS TO GEOCHEMISTRY

.50 

.40

.30 

.20

.08

.06

.04

.02

.01

.0) 6 8 10 20

LOG I

FMUEE 14. Working curve of hafnium-zirconium ratio in zircon.

g ' 

£

0.I 8

i 6

Intensity rotios: -|£ 2583.4'o5A

.6 .8 1.0 2.0 

INTENSITY RATIOS

4.0 6.0 6.0 10.0

FIQTJEE 15. Hafnium working curve.
DETERMINATION OF HAFNIUM-ZIRCONIUM RATIO 85

ratios. These line pairs were zirconium 2761.911 A and hafnium 

2641.406 A, and zirconium 2761.911 A and hafnium 2820.224 A. 

Straight-line curves were produced when the spectral lines zirconium 

2538.405 A and hafnium 2641.406 A were used to plot the log of the 

intensity ratios against the log percentage concentration of hafnium 

for the hafnium determinations. The intensity ratios of the transmittance values were obtained by using the emulsion calibration curve. 

The intensity ratios were applied to the working curves to determine 

the concentrations. No background corrections were necessary because the background was insignificant. Figures 14 and 15 show 

typical examples of these curves.

In the early part of the work the ratio was determined first by plotting the log of the intensity ratios against the log of the hafniumzirconium ratio by weight of the standards, using zirconium as an 

internal standard. Straight-line curves were produced when the 

same line pairs (zirconium 2538.405 A and hafnium 2641.406 A) were 

used in a similar manner for the hafnium determinations. However, 

when chemical methods were used to check the spectrographic and 

zirconium totals, an apparent bias of +1.87'was observed. Tests 

were continued to eliminate this bias. It was found that increasing 

the graphite to three parts instead of two, cutting the cup of the lower 

electrode deeper, and using zirconium 2761.911 A with hafnium 

2641.406 A or zirconium 2761.911 A with hafnium 2820.224 A for the 

ratio curves and zirconium 2538.405 A with hafnium 2641.406 A for 

the hafnium curves, eliminated the bias.

As a check on the calculated zirconium values additional experimental work was done. Simulated samples (see table below) were 

arced under the previously described spectrographic conditions (intensity decreased from 100 percent to 25 percent). A zirconium 

working curve was prepared and three additional synthetic samples 

were analyzed for zirconium (zirconium 2761.911 A) without an 

internal standard line. The results are as follows (see working curve, 

fig. 16):

380035 66
86 CONTRIBUTIONS TO GEOCHEMISTRY

Comparisons of spectrographic and calculated percentages of hafnium and zirconium 

in simulated zircon samples

Sample

S-l

1

2 

2 

3 

3

4 

4

Element

Zr 

Hf 

Zr 

Hf 

Zr 

Hf 

Zr 

Hf

Spectrographic percentage

Added

43 

.5 

48 

1.0 

53 

1.5 

58 

2.0

Found

0.48

1.05

1.55

1.97

Ratio

0. 0110

.0216

.0290

.0340

Calculated 

percentage

43.5

48.3

53.4

58

Difference

Zr

0.5

.3

.4

.0

Hf

0.02

.05

.05

.03

Sample 

S-5 Zirconium.

6 Zirconium.

7 Zirconium.

Element

Added Found 

(percent) (percent)

45

50

55

45. 1

49.9

55.0

Zr 2761.9IIA 

T=25 percent

LOG TRANSMISSION

FIGURE 16. Zirconium working curve.
DETERMINATION OF HAFNIUM-ZIRCONIUM RATIO 87

The hafnium-zirconium ratios could be determined by analyzing 

for hafnium and zirconium independently, or by the simpler way of 

using a ratio curve.

The emulsion calibration curves were prepared by the two-step, 

method described by Harvey (1950, p. 76-78).

The following experimental conditions were used:

Excitation source: multisource d-c arc. This procedure can utilize any 300 

volt d-c power source where the operating discharge value remains stable 

at 12 amperes and 300 volts.

Resistance: 15 ohms.

Initiator: high.

Phase: 0.

Strike: strike position.

Amperes: 12.

Spectrograph: 21-foot Wadsworth-mounted grating.

Slit: 25 microns.

Optics: totfil arc image focused on collimating mirror; a thin crystal quartz 

cylindrical lens covered slit; no apparent imaging on slit.

Emulsion: SA-1, plates, Eastman.

Development: 5 minutes at 18° C, ±J4° C, D-19.

Arc gap: 4 to 6 mm, gap adjusted to marked positions on outside target.

Transmission: 100 percent.

Arcing time: 3 minutes.

Spectrum: lirst order.

Electrode, lower: carbon, spectroscopie carbons, J4 in., cut to outside diameter 0.22 In., depth of shoulder 0.12 in., inside diameter 0.19 in., depth of 

crater 0.20 in.

Electrode, upper: carbon, spectroscopic carbons, J4 in., hemispherical, 0.06- 

in. radius,

EVALUATION OF RESULTS

Eight samples were analyzed chemically by two methods for their 

content of zirconium and hafnium. The first chemical method (Hillebrand and Lundell, 1953, p. 567), precipitation by n-propylarsonic 

acid, gave precipitates with a high content of impurities, as shown 

by spectrographic analysis. Chemical precipitates, produced by the 

mandelic acid, precipitation method (Kumins, 1947), were tested 

spectrographically and showed aluminum, iron, and magnesium in 

the 0.1 to 0.05 percent range, barium in the 0.005 to 0.01 percent 

range, and manganese in the 0.0005 to 0.001 percent range. Results 

given by the mandelic acid precipitation method were selected for 

comparison with the spectrographic results because of the high purity 

of the precipitates. These comparisons are shown below. The data 

may be supplemented by reference to Fleischer's work (1955).
90 CONTRIBUTIONS TO GEOCHEMISTEY 

LITERATURE CITED

Ahrens, L. H., 1950, Spectrochemical anaylsis, Cambridge, Mass., Addison-Wesley 

Press, Inc., p. 191-193.

Fassel, V. A., and Anderson, C. H., 1950, Quantitative spectrographic analysis 

of zirconium-hafnium mixture: Optical Soc. America Jour., v. 40, p. 742-747.

Feldman, C., 1949, Spectrochemical determination of hafnium-zirconium ratios: 

Anal. Chemistry, v. 21, p. 1211-1215.

Fleischer, Michael, 1955, Hafnium content and hafnium-zirconium ratio in 

minerals and rocks: U. S. Geol. Survey Bull. 1021-A, p. 1-13.

Harvey, C. E., 1950, Spectrochemical procedures, Glendale, Calif., Applied Research Laboratories.

Hillebrand, W. F., and Lundell, G. E. F., 1953, Applied inorganic analysis, 2d 

ed., New York, John Wiley and Sons.

Kumins, C. A., 1947, Zirconium determination in the presence of interfering 

elements: Anal. Chemistry, v. 19, p. 376-377.

Larsen, E. S., Jr., Waring, C. L., and Herman, J., 1953, Zoned zircon from Oklahoma: Am. Mineralogist, v. 38, p. 1118-1125.

Mortimore, D. M., and Noble, L. A., 1953, Determining low concentrations of 

hafnium in zirconium: Anal. Chemistry, v. 25, p. 296-298.

Pierce, W. C., and Nachtrieb, N. H., 1941, Photometry in Spectrochemical 

analysis: Indus, and Eng. Chemistry, Anal, ed., v. 13, p. 774-781.

Waring, C. L., and Annell, C. S., 1953, Semiquantitative spectrographic method 

for analysis of minerals, rocks, and ores: Anal. Chemistry, v. 25, p. 1174- 

1179.

O