2024
A N A L Y T I C A L CHEMISTRY
All t h e oxides crystallized from their melts with t h e cubic C structure belonging t o t h e space group Ia3 ( T h 7 ) , with 16 formular ,units per cell (6). T h e lattice constant of yttrium sesquioxide has been determined recently by Swanson and F u y a t ( 3 )as 10.604 A. Templeton and Dauben ( 4 ) reported a, = 10.667 i 0.006 A. for dysprosium sesquioxide, a, = 10.547 =t0.003 -4.for erbium sesquioside, and a, = 10.439 =t0.007 h.for ytterbium sesquioxide.
X-R.4Y DIFFR.4CTIOS DATA Cell Dimension, a,;
Yttrium sesquioxide Dysprosium sesquioxide Erbium sesquioxide Ytterbium sesquioside
A.
10.605 i 0.001 10.667 + 0 . 0 0 1 10.550 zt 0 . 0 0 1 10.435 + 0.001
Formula Weight 225.84 372.92 382.4 394.08
Density, Grams/Cc. 5.030 8.161 8.651 9.213
T h e above cell dimensions have been determined by leastsquares linear extrapolation of t h e a, values calculated from highangle diffraction lines against t h e function (cos%/sin 0 cos2Ole) t o t h e zero value of t h a t function. Between 20 and 30 Cuh'orl a n d C u h ' a ~lines in t h e angular region 0 = 65" t o 85" Jvere used in each case.
+
OPTICdL PROPERTIES
Refractive Indices.
Yttrium sesquioxide Dysprosium sesquioxide Erbium sesquioxide Ytterbium sesuiiioxide
Erg 4358 -1. 1.93; 1 984
K a v e Length Na 5893 b. 1.915 1.974 1,960
6640 .1. 1 903 1 ,952
1.947
RIolecuIar Refraction (5893 A . ) . 2 l . l 3 cc. for yttrium sesquioxide, 22.4 cc. for dysprosium sesquioxide, 21.50 cc. for erbium sesquioxide, 20.6 cc. for ytterbium sesquioxide. T h e above values of molecular refraction for t h e three cubic rare earth sesquiosides have been plotted on Figure 1, together x i t h corresponding valiies for t h e hexagonal neodymium oxide ( 1 ) and t h e monoclinic samarium oxide ( 2 ) . T h e molecular refraction of rare earth sesquioxides appears t o be closely approximated by a
Table 11. Absorption Spectrum of Erbium Sesquioxide Band Maxima, mr 487.4 488.3 489.0 489.7 490.7 492.8 493.9 494. 9 496.9 499.4 505.5 513.5 521.4
Relative Intensity
1 1 1 9
Band Alaxima, mp
522. 4 524.2 525.2 526.2 527.1 528.2 529.3 530.6 531.5 533.4 534.3 536.1 537.0
Relative Intensity 6
Band Maxima, mp
540.6 541 3 547 8 548 9 550 5 551 5 553 1 555 9 558 3 566 0 650 9 656.2 662.6
10 4 4 8
6 4 3
3 1 1 1 1
Relative Intensity 1 3
linear function of t h e atomic number and not markedly affected by differences of crl-stal structure. Color, Yttrium sesquioxide is pale brown, erbium oxide pink. Dysprosium and ytterbium sesquioxides are colorless. Erbium sesquioxide exhibits a n absorption spectrum with many bands in t h e visible range, t h e half-width of t h e bands not esceeding 10 t o 30 A . except in t h e case of three red hands. T h e maxima and relative intensities of t h e absorption bands are listed in Table 11. These were measured with a Cary Spectrophotometer on a sample of crushed melt mounted in a n immersion liquid with the refractive index 1.96 for sodium light. LITERATURE CITED
(1) Douglass, R. II.,dN.$L. C H E M . 28, 551-2 (1956). ( 2 ) Douglass, R.II.,Staritzky, E., Ibid., 28, 552 (1956). (3) Swanson, H. E., Fuyat, R . K., Ugrinic, G. II.,"Standard X-Ray Diffraction Powder Patterns," Katl. Bur. Standards, Circ. 539, vol. 3, 28 (1954). (4) Templeton, D. H., Dauben, C . H., J . A m . C'/ievi..Soc. 76, 5237-9
(1954). (5) Wyckoff, R. W. G., "Crystal Structures," Interscience, Xew York, 1948.
7-01.
I, chap. 5, p. 2.
WORKdone under the auspices of the Atomic Energy Commission. Contributions of Crystallographic D a t a for this section should be sent t o W. C . McCrone, 500 East 33rd St., Chicago 16, Ill.
SCIENTIFIC C O M M U N I C A T I O N
Precision Plating of 'Polonium SIR: T h e ease with which polonium spontaneously plates o u t on metal foils and disks has been utilized in most procedures for its analysis. Accordingly, t h e experimental conditions affecting the plating have been extensively investigated (1-6). However, a perusal of these published reports leaves the definite impression that the plating procedure is a t best somen-hat inaccurate. For example Fink and others (3) state t h a t the reproducibilitl- of their method Il-as "probably not better t h a n +5Y0." T h e Los .Alamos group ( 2 ) reported a n accuracy of 98 f 10y0 in analyzing urine. Smith, Della Rosa, and Casarett ( 5 ) demonstrated a direct relation between recovery by a single plating and the amount of polonium which can be plated-i.e., total for original plating plus several successive platings of snpernatants until the radioactivity in t h e disk approximated background of counter-with recoveries varying from 90 to 96Y0in a single plating. K h i l e these recoveries are sufficient for many purposes, a procedure giving hetter precision was needed as a prerequisite t o a program of investigation of the physicochemical properties of polonium. By combining the best features of the various published methods, it is conveniently possible to obtain single plating recoveries of 99% and better, a n accuracy within t h e probable counting error, and a reproducibility Tyithin the pipetting error.
PROCEDURE
T h e apparatus used was similar t o that of Eutsler, Milligan and Robbins (Z), in t h a t a metal foil disk (0.003 inch thick a n d 1.5 inches in diameter; silver in our case) was suspended in t h e polonium solution by means of a glass stirring rod hooked through a 1-mm. hole in t h e foil. T h e polonium solution rvas contained in a 300-ml. tall-form beaker without hp, which was suspended in a n a t e r b a t h through a sheet of copper containing six holes, each large enough to pass all but t h e lip of the beaker. Thus, si\ solutions could be plated simultaneouslv. T h e idea first suggested by Baxter and K o o d ( 1 ) of operating all the stirrers with one motor by means of a pulley and belt system v a s adopted. After plating, both sides of each silver foil n-ere counted in scintillation counters. RESULTS AND DISCUSSIOS
I n Table I are shown the results of a typical plating experiment with polonium-210 solutions containing about 3000 c.p.m. For each experiment, 1 ml. of stock polonium-210 solution n.as diluted with 200 ml. of 0 . 5 S hydrochloric acid. When t h e b a t h reached 97" C., plating was started. T h e first disk was exposed for 1112 hours. Then a second disk was exposed for 2 hours. Finally a third disk was exposed for 2 hours. T h e sides of the beakers were washed down with distilled water after 1 hour of plating each time. T h e three solutions showed a plating efficiency (in terms of total recoverable counts) of 99.8 0,2Y0for one plating. This
+
V O L U M E 2 8 , NO. 1 2 , D E C E M B E R 1 9 5 6 Table I.
2025
cy,
Plating, Plating, C.P.11.b c .P.M. 3467 4 3354 15 3390 3 -1v. 3404 i 42 i * 4 Data corrected for hackaround.
Counts, 1st C.P.Rl.b+ Platingd 3471 99 9 3369 99.5 3393 99 9 3411 + 37 998+02 3 c.o.m. ~- oer foil (both sides). t o t a l no. of counts * Probable counting error = 100% X 0.67 dtotal no. of counts = O.P%. c Total recoverable = 1st plating plus 2nd plating. Third platings always showed background only. d Per cent efficiency of plating = 100% X counts on disk/total recoverable counts. Q
MEETING R E P O R T S
T>-pic;dPlating Experiment with Polonium-210 Solutionsa
Society for Analytical Chemistry T A
meeting of the Midlands Section, held September 11, in
ABirmingham, t h e following paper was read s n d discus‘ed.
I
Tahle 11. Relationship between Total Recoverable Counts and Dilutiona Total Efficiency Probable 1st 2nd Recoverable of 1st Counting Plating, Plating, Counts, Plating, Error, C.P.RI. C.P.31. C.P.AI. 70 % 205 1 206 99 5 0 9 52 1 0 521 100.0 0.9 1020 1 1021 99.9 0.9 40i5 48 4123 98.9 0.4 -4v. 99 6 2~ 0 4 Aliquots of 10, 25, 50, and 200 ml. of stock polonium-210 solution were diluted t o 200 nil. with 0 . 5 5 hydrochloric acid. Data corrected for decay to same data as Table I experiments. 0
is re11 x i t h i n the probable counting error of 0.5’%. These results have been reproduced repeatedly. Experiments also showed t h a t failure t o wash donm the sides of the beaker during the experiment introduces an error of about l%-i.e,, recoveries of only 9S.O +C 0.4yo were obtained. The d a t a for Table I1 show that,, over a 20-fold variation in concentration, there is a strict proportionality between the total recoverable counts and dilution. This would not be expected if more t h a n a negligible amount of polonium remained unplated. Furthermore, soaking the beakers in 631 hydrochloric acid after each plating yielded no further counts, indicating t h a t a n y polonium remaining adsorbed on t h e beakers was negligible. V e have also counted pieces of glass from the bottom of the beakers used for plating and obtained only the background count, again indicating negligible absorption, if any.
Recent Advances in the Analysis of Cast Iron and Foundry Materials. Iv. E. C L A R K EBritish , Cast Iron Re.3earch dizociation, Alvechurch. The heterogeneous nature of cast iron gives ri-e to sampling difficulties. Different types of graphite, flake and nodular. were illustrated, and sampling for carbon determination was descrihed. Many different sampling techniques have t o he used, because the size of the casting and the type of graphite affect the type of +ample required for accurate results. Kew methods include radio-frequency induction heating of samples for the determination of carbon and sulfur. The conditions required for steel samples, gray and nliite cast-iron drillings, and solid samples, including ferroalloy.. were discussed, as well as the advantages and disadvantages of this type of heating. The analysis of nodular irons was outlined. Methods for the determination of small amounts of cerium, rapid chemical methods for magnesium, and methods for analysis of nicliel-iiiagi~e.;iurn alloys were described. At a joint meeting of the Scottish Section of the Society for Analytical Chemistry and the Methods of A n n l ~ go”), formerly the Spekker Group, held i n Glasgow September 28, three papers were presented. Photometric Determination of Molybdenum a s the Thiocyanate. R. K E R RImperial , Chemical Industries Ltd., Kobe1 Divi>ion. Stevenston. Ayrshire. The paper covered a study of the inolybdeiium-thiocyaiiate complex and it,. applicability t o the routine determination of molyhdenum photometrically in various classes of steels. Determination of Copper in Steel. L. J. d. H.\vwoon .\SD P. STTCLIFFE. Catton & Co., Ltd., Yorkshire Steel Foundry, Hunslet, Leeds. Bis-cyclohexanone oxalyldihydrazone has been established as a reagent for the determination of copper in steel. and ferrous metals generally. The method has been particularly developed for routine analysis, with an ahsorptiometric finish, and ia appreciably more simple and rapid than any method hitherto puhlished. S o separations, either chemical or physical, are involved, and the solvent acids mill cover almost all types of steel alloys. Interfering elements are very few, and in all cases except one, can he virtually ignored.
ACKSOWLEDGMENT
K e are happy t o acknowledge the aid of T a f t Toribara in constructing the apparatus. This paper is based on n-ork performed under contract with the United States Atomic Energy Commission a t the University of Rochester Atomic Energy Project, Rochester, K.T. LITERATURE CITED (1) Baxter, R., Wood, D., U. S. dtomic Energy Comm. Rept. UR-
269 (1953). (2) Eutsler, B. C., LIilligan, 31. F., Robbins, RI. L., Ibid., LA-1904 (1955). (3) Fink, R. AI., ed., ”Biological Studies with Polonium, Radium, and Plutonium,” S S E S , Div. VI, vol. 3, p. 19, 1\IcGraw-Hill, NewYork, 1950. (4) Mulhoney, T. J., Sorris, IT. P., Iiisieleski, W.E., U. S. Atomic Energy Comm. Rept., ANL-4333, pp. 103-109 (1949). ( 5 ) Smith, F. A , , Della Rosa, R. J., Casarett, L. J., I b i d . , UR-305 (1 955). Department of Radiation Biology School of Medicine and Dentistry University of Rochester Rochester, K.Y . RECEIVEDfor review January 6 , 1956.
Is.4.4~FELDMAK MARGARET FRISCH
Accepted August 22, 1956.
Analysis of Titanium and Its Alloys. \I*. T. ELWELL, Imperial Chemical Industries, Ltd., Metals Division, Kitton. Birmingham. Only within the past 4 or 5 years has titanium metal become a commercial product. I t is not surprising, therefore. that published data covering methods of analysis are scantv. The recent rapid gr0wt.h of the titanium industry, the increasing uae of the metal, and the development of an ever-increasing numher of titanium alloys, make it essential that information on analytical niet!iods he available. I n the courae of considerable research over the whole field of t,itanium technolog3 , Imperial Chemical Industrie.. Ltd.. have given much attention to methods for the determination of a large number of different elements in titanium, whether pre-ent R S impurities or purposefully added. The development of recommended procedures associated with this new branch of analyrirnl chenii,try was discussed. On Octoher 3 a meeting i v a ~held in T,oridon, a t which two papers n-ere presented. Determination of Vitamin D and Related Compounds. Introduction and Preparation of Compounds in the Irradiation Series. Analysis of Irradiation Products. IT. H. C. SHA.W,J. P. J E F F E R I E R , AND T. E. HOLT, Glaxo Laboratories, Ltd., Greenford. Physical and chemical methods for the determination of the vitamins D were re-examined, particularly those for determining the composition of the complex mixtures formed during the ultra-
