V O L U M E 20, NO. 5, M A Y 1 9 4 8 porcelain crucible, with the u>e I J ~suctioii. It nab \+askled first with a few milliliters of approximately 3 S hydrochloric acid to %voidprecipitation of basic tin salt. and then with hot distilled water until i t was free from chloride. During filtering, the precipitate was kept always covered by the solution in order to avoid nossible oxidation and, as a con\equence, solution of the tellurium The crucible was placed on a nra suction flask and the beaker, i n R hich the precipitation had bpen carried out, was n ashed with 3 few milliliters of warm 1 to 1 nitric acid which was then trans;erred into the crucible. More warm 1 to 1 nitric acid was added t o the crucible until tellurium was complf~telydissolved. The tellurium solution was transferred from the suction flask to a 50ml. beaker and evaporated to dryness on a hot plate. The residue was taken up with 3 ml. of concentrated hydrochlorir acid, transferred to a graduated test tube of 1.2-cm. diameter, brought to a volume of 8 ml. with filterd distilled water, and mixed by stirring 'rith a glass rod. One milliliter of 10% stannoui chloride was added to this solution with immediate and vieorow stirring and this was followed by the addition of 1 ml. of 5% gum arabic, with Pqually vigorous and immediate stirring. This concentration of min arabic stabilizes the tellurium suspension for about 6 hours. Deviations from this standardized technique led to irregular results. Obviously the rfficiency oi iiiising affected the particle iizes in the tellurium suspension. By adding stannous chloride before the gum arahic is added, a higher light absorption and a higher sensitivity are attained. Tellurate is not reduced by stanwus chloride under the conditions of this method. The absorption was compared in the Klett-Summerson photoelectric colorimeter, using light filter No. 42, with that of a blank. The concentration may be read off a graph or computed by mulmicrograms of tellurium ___, which riplying the reading by the factor reading i i i this case yielded 0.346. Graph and factor are readily obtained :rom a series of controls. Plotting of the amount of tellurium, be~
489 tween 5 and 140 micrograms, against the colorimeter reading gave a straight line, which shows that Beer's law is satisfied. Tahle I gives a few of the results obtained and shows that tvlluriurn can be determined with an error of * loyo. Application of the method to the analysis of urine was atwmpted. Urine blanks show ab3orption wit,h the filter employed. This difficulty may be overcome by removal of t,he tellurium by centrifuging after the colorimetric value has been determined and subtra,cting the reading obtained with the centrifugate. With the same light filter ( S o . 421 in the Klettkhimerson photoelectric colorimet,er, one may use the method also for the determinat,ion of selenium. ACKNOWLEDGMENT
Thr author is indebted to John ?;. dbersold for t,he description of the air-sampling kchnique. LITERATURE CITED
Furman, N. H., Ed., ''Scott's Standard Methods of Chemical Analysis," Vol. 1. pp. 778--93! Kew Tork, D. Yan Xostrand Co., 1939. (2) Kronenberg, 31.H., and Setterlind, 1.S . ,"Determination of Tellurium in Air Collected in Ferrous Foundries," State of Illinois Dept. Public Health, Division of Industrial Hygiene. Laboratorj- Manual, September 1942. (3) St,einberg, H. H., Massari, 9. C., Miner. A . C., and Kink, Ti.. .1. !1)
Ind. Hyg. Toricol., 24, 183 (19421. (4jVolkov, S. T., Zavodskaya Lab., 5,1429 (1938). RECEIVED M a y 2, 1947.
Direct-Reading Contact Scale for Analysis of X-Ray Spectrometer Charts WILFRID R. FOSTER, Ceramic Division, Champion Spark P l u g Company, Detroit 1 1 . Mich.
HE recording x-ray spevtrometer (Sorelco Geiger-counter 'x-ray spectrometer) which hah recently become commercial15 .tvailable is proving a boon to industrial research and control iahoratories because of the speed with which it yields results. By its use a complete diffraction pattern can ordinarily be ob+ained in a small fraction of the time required with the usual diffraction-camera equipment. The pattern so obtained i6 analogous t o the microphotometer trace of the photographic pattern, but is superior in sensitivity and resolution. Proper interpretation of such a spectrometer pattern involves, of rourse, the determination of the d-value (interplanar spacing) corre.yonding to each peak, the evaluation of the relative intensities of khr peaks, and a check of these data aga2ini.t the A.S.T.hl Bard file of x-ray diffraction data. In an industrial testing lahoratory, M here the spectrometer riiay he in continuous service, the analvsis of the steadil: accumuiatirig charts can consume a considerable amount of time. To jhvkte the tediousnestsof repeated solution of the Bragg equation by actual calculation. it has become standard practice to use tabulated data ( 2 ) relating Bragg angle to d-value for the par+ d a r target material used. This t r 4 t s in a distinct saving of time. However, errors in estimating the value of the Bragg anpk or in reading and interpolating the tahulatrd data are not infrequent. .\ time-saving and accurac? -inc>reabingdevire is a combined kwo-theta and d-value scale which. when appropriately aligned with the spectrometer pattern, alloas one t o read directly the d-values of the peaks. Two-theta, or tn-ice the Bragg angle, is Phosen as the unii of meawrcnirnt of this scale, hecause the
angular motion of the Geiger counter is eo measured. Since for most mork the speed of the Geiger counter is iuch as to give a -15-inch chart tor 90" of two-theta, the scale is made up on the hasis of 2"of txo-theta per inch. Since for mobt work the coppertarget x-ray tube is employed, the scale is made up from the data of the appropriate tables for copper K a radiation. The scale may be constructed In t a o section
