similar to those obtained nith the Resofles polyester. Details on the quantitative composition of mint oils using these and other packings Fill be reported a t a future date. ACKNOWLEDGMENT
The authors thank Fred Cramer, A. h9. Todd Co., for courteously providing the mint Oil constituents in the 6%sential oil collection of our laboratories.
LITERATURE CITED
(1) Craig, B. AI., l l u r t y , N. L., Can. J . Chem. 36, 1297 (1958). (2) Fastman Chemical Products, Inc., Kingsport, Tenn., “SAIB,” Bull. L-102 (1958). (3) Johnson, H. W., Stross, F. H., ~ ~ N A L . CHEW30, 1587 (1958). (4) Lipsky, S. R., Landowne, R. A., Lovelock, J. E., Zbid., 31, 852 (1959). (5) Orr, C. H., Callen, J. E., Ann. AT. Y . Acad. Sci. 72, 649 (1959).
(6) Zlatkis, A, Ling, S. Y., Kaufmann, H. R., ANAL.CHEW31, 945 (1969). D. RIORISON SMITH JOHN C. RARTLET
LEOLEVI
Food and Drug Directorate Department of Xational Health & Kelfare
Tunney’s Pasture Ottawa, Ontario, Canada
RECEIVED for reviea December 24, 1959. Accepted February 15, 1960.
Rapid Determination of Fluorine in Phosphate Rocks SIR: I n applying the procedure of Parkw aiid Goddard ( 8 ) for the determination of aluminum in phosphate rocks (3) certain effects Lvere observed which sliolved promise for t h r determiiiation of fluoride. Parker and Goddard showed that calcium in excess douhles the sensithity of the alizarin-3sulfonate procedure for aluminum. I n the study in this lahoratory (3) the intensity of color of the complex of aluminum-calcium Alizarin Red S is unaffected by phosphate hut is diminishcd hy fluoride. T’arious 11-ays to utilize these effects for the determination of fluoride i n phosphate rocks n ere tried. A rapid simple procedure mas tieveloped in which the sample solution is passed through a cation ion exchange column. After the cations are removed, a fixed amount of aluminum is added to all samples and the fluorine is detcrniined. Fluorine is a normal constituent of phosphate rocks, where it usually ranges from 0 to about 4%. It occurs mainly in apatite, and to a lesser extent in fluorite. The l u g e amount of apatite and the small amount of fluorite can be takcn into solution with a simple acid attack. Distillation mrtliotls (1) give exccsllcnt results. but they are more timeconsliming aiid less well suited to the hantlling of large niunhers of samples than arc resin columns. A half dozen columns rcpresent a small capital outlay compared t o the cost of a single dietillation unit. REAGENTS ht o c k
Alii minuni Solution. D issolvc 87.5 mg. of pnrc aluminum foil in about 25 1111. of 6 S HC‘1 in a 100-nil. volunic+ic flask. Make to volume and mix. Dilute Aluniinum Solution. Dilute 10 nil. of the stock aluminum wlution to 1 liter.
Alizarin Red S Solution (sodium alizarin sulfonate). 0.1% in water. The dye C . I . 1034 was used. Buffer Solution. Dissolve 70 grams of anhydrous sodium acetate and 30 ml. of glacial acetic acid in 470 mi. of water. A standard phosphate rock such as National Bureau of Standards standard sample 56 b or other phosphate knorrn to contain between 3 and 4% fluorine. Cation exchange resin Amberlite IR-120 (H) or equivalent. SPECIAL APPARATUS
One or preferably srveral resin columns, approsiinately 18 X 300 mm. This size corresponds to the dimensions of a 100-ml. buret vheii it is filled with resin to the 5o-ml. mark. It should be filled with the eschange resin and converted to the hydrogen form by passage of 50 ml. of 6‘V hydrochloric acid through the column, with subsequent washing until the effluent is neutral. PROCEDURE
Transfer 50 nig. of the pondered sample and 50 mg. of the standard sample to separate 100-ml. volumetric flasks. T o an additional flask transfer 25 mg. of the standard to provide a fluoride level half that of the standard. Add 10 nil. of 3 5 HNOs t o each of the flasks. and an additional 10 nil. to another flask to lie used for the acid blank. After 10 minutes. dilute to the mark and niis. Allow anothcr 10 niinutcs for the insolublcs to settle. Pass 10 ml. of each solution through the resin column a t the rate of about 1 drop per second. catching the effluent in 100-nil. Yolumetric flasks. Pass t a o 10-ml. poitions and one 30-ml. portion of watrr in succession through the column for each sample. The acid blank need not lie pawed through the column. Transfer two 10-ml. aliquots of the acid blank to two 100-ml. volumetric flasks anti add about 50 ml. of w t e r to them. Let oiie flaqk s c r w as a refereiicc tdank anti thcx other as a rcJfcrcnce
aluminum solution. T o one of these flasks, and to all of the flasks with resin separated solution, add 15 ml. of the dilute aluminum solution with a transfer pipet. Add 2 ml. of a 14% calcium nitrate solution to all flasks. Add 10 ml. of the buffer solution to all of the flasks viith a graduate, swirling as the addition is made. Allow them to sit for 10 minutes. Add by pipet 5 ml. of the Alizarin Red S solution to each flask with swirling. Make t o the mark, mix, alloiv to sit for 1 hour, then read absorbance for each solution in a spectrophotometer a t 475 nip, using the blank solution as a reference. CALCULATIONS
Subtract the absorhance of the standards and samples from that of the reference aluminum solution. These differences are nt,arly proportional to the fluorine content. Plot t h r difference values for the two standards on rectilinear graph paper against their per cent fluorine. Use a curve drawn between 0 and these two points to ohtain per cent fluorine for the samples.
Determination of Fluorine Fluorine, yo SamDle Described D i d l a Design’ation method tion KBS N o . 56
No. 56a No. 5% Mona 6
Mona 7h
Lab. No. 91064 (aluminum phosphate) 81376 81329 58709 25095
3 4 3 5 3 4
0 10 0 11
0 4 4 3
17
2 2 2 2 2
VOL. 32, NO. 4 , APRIL 1960
3 4 3 6 3 4 0 07 0 06
0 18 42 4 0
3 1
2.1
569
TEST OF PROCEDURE
The procedure described was applied to a variety of phosphates from several sources and with a range of fluoride content from 0.06 to 4.2y0 fluorine. These previously anby the s. Survey with the distillation technique during the course of several years, and also those National Bureau of Standards
189.
standard phosphates which were available. The results in the table were selected from a larger set of data to illustrate the degree of accuracy a t low, and medium levels Of fluorine* The Bureau of Standards standard sample No. 120 phosphate rock was used as the reference standard. (This s h n d ard has been discontinued.) The standard sample currently available is y o . 56b, for which only one determination is cited by the Bureau of Standards.
LITERATURE CITED
(1) Fox, J. E., Jackson,
IT. A., ANAL.
CHEM.31,1657 (1959). (2) Parkerj c. G o d d a d .4.p.1 Anal. Cham. Acta 4,517 (1950). (3) Shapiro, L., Brannock, IV. I\7., U. S. Geol. Survey, Bull. 1036-C (1956). LEONARD SHAPIRO U.S.Geological Survey Washington, D. C. 2 4 . j
authorized by the Director, U. S.Geological Survey.
PUBLICATION
Zirconium Carbide
CHARLES P. KEMPTER and R. JAY FRIES
Los Alamos Scientific Laboratory, University of California, Los Alamos, N. M. of zirconium T carbide was first reported by van Arkel ( I ) . The space group is 0; HE CRYSTAL STRUCTURE
F m 3m (NaC1 structure-type) with 4 (ZrC) per unit cell. The x-ray powder data file contains one "ZrC?" data card (1-1050) which lists approximate interplanar spacings with no Miller indices assigned. The starting material used for this investigation was high purity ZrC obtained from Union Carbide Metals Co. About 10 grams of this material were pressed in a pellet die at 25 p.s.i. to form a cylindrical sample 0.5 inch in diameter and 0.75 inch long. The sample was then set in a graphite crucible and heated inductively in 1 atm. of helium. The sample was heated slowly to about 28OO0C.,soaked a t this temperature for 1 hour, and then cooled rapidly in helium. Before this treatment, the material analyzed 87.9% Zr Hf, 0.9% free C, and
