ANALYTICAL CHEMISTRY
928 Table I.
Water in Precipitated Thorium and Uranium Fluorides
Fluoride ThF4,nHiO
Sarnple
F,
7
I
Tli, c; 69.46
22 i 2
ThF, nHxO
B
67 0.5
21 98
VF, nHtO
-4
70 28
22 39
I-F,.?iH?O
B
. .
..
H2O H20 Calcd., CiO Found, cO 7.82 / . , I i 79 10 97 IO 90
- --
10 95 i.33 ,..
6.67 68
6
66 7 6.1 I
Difference 0 04 0.05
each prepared by hydrofluorination of the oxide. By the use of large (10-gram) samples in these analyses, satisfactory precision was obtained. The results for the uranium(1V) fluoride samples are believed t o be within a few hundredths of 1% of the true value, while an absolute standard for beryllium fluoride is lacking.
0 66
...
Table IT. Water Contents o€ Conimercial Fluorides Fluoride
Sample
Water Content, % ’
The rear section must, be unscre\\-ed and recharged with fresh sodium carbonate after each 10 t o 50 analrses, depending 011 the moisture content of t,he material analyzed. The first result obtained using fresh sodium carbonate was generally low, and was discarded. LITERATURE CITED
RESULTS
The accuracy of the method was determined hy application to thorium and uraniuni(IT-) fluoride samples whose metal and fluorine contents had already been reliably established through pyrohydrolytic anal~-sie ( 9 ) . The thorium and uranium(1V) fluorides were prepared by precipitation from aqueous solution with h>-drofluoric acid, centrifuging, washing with water, air drying, and grinding. Their water contents were calculated by eubtracting the total metal and fluorine percentages from 100, a procedure satisfactory for thorium fluoride but giving too high a water content for uraniuni(IT7j fluoride, prohahly atti.ilmtahle to partial oxidation during drying. Talde I s h o w that the water contents calculated and found for thorium fluoride agrce within a few hundredths of I%, but the difference in the case of nraniuni(IT-) fluoride is more than 0.5%. Table I1 shows the water contents of various batches of commercial anhydrous uraniuni(IT-) fluoride and beryllium fluoride,
Feibig, J. G., and Warf, J. C., Manhattan Pmject Rept., CC-2939 (June 29, 1946). Gooch, F. .4.,A m . Chem. J . , 2 , 247 (1880). Jannasch, P., and Weingarten, P., Z . anorg. Chem., 8 , 362 (1895). Jannasch. P.. and Veinearten. P.. Ibid.. 11. 37 (1896). Kusirian, S.B., Am. J.-Sci.. 4th Ser., 36, 401 (1913); 2. anorg. Chen,., 85, 127 (1914).
Penfield, S. L., A m . J . Sei., 3rd Sei., 48, 31 (1894); 2. nfzorg. Chem., 7 , 23 (1894).
Rodden, C . J., “Analytical Chemistry,” Natl. Nuclear Energy Series, Di\-. VIII, yo]. I, p. 250, Sew Tork, McGraw-Hill Book Co.. 1960. Sigocs, L., .4nz. A k a d . Wisa. Kim. Math. naturw. KZ.,14, 135 (18iT). Warf, J. C . , Cline, T T . D.. and Tei-ehaugh, R. D., -4s.k~.CIHEY., 26,342 (1954). RECEIVED f o r review Norember 23. 1953. Accepted February 12. 1954. Contribution S o . 249, Institute for Atomic Research and Department of Chemistry, Iowa State College, Ames, Iowa. Work performed under the Manhattan Di-trict of the U. S. Corps of Engineers.
Effect of Side Chain on the Chromatographic Adsorption of Some Ketones on Carbon EDGAR D. SMITH’and ARTHUR L. LEROSEN~ Coates Chemical Laboratory, Louisiana State University, Baton Rouge, La.
I
S C O S S E C T I O S with a fundamental study of the forces involved in chromatographic adsorption ( S ) , it was desirable that a simple method be developed for determining ratio of distance moved by zone to that moved by developing solvent ( I ) of various adeorptives (compound adsorbed) ( 5 ) on colored adsorbent materials. The present work describes a method which has been found to give good results, and presents tentative conclusions reached in a study of the adsorption affinities of some simple ketones on carbon. If a chromatographic tube iq packed so that a short coluiiin of adsorbent A is placed above a longer column of adsorbent B, it should be povible to calculate the R value of a chromatographic zone on .i by noting the apparent change in R value of this zone on 13. Obviously, if the R value determined on adsorbent B in this way is the same as that found by direct measurement, then adsorbent .1 has not slowed the movement of the zone relative to the developing solvent and the R value of the zone on A is 1.00. Any apparent decrease in the rate of zone movement in the second adsorbent, however, would be an indication of adsorption of the adsorptive by adsorbent A. It remained to be proved whether this “sloning” of the ad-orptive could be made the basis for 1 2
Present address, The Chemstrand Corp., Decatur, -41s. Deceased.
calculating I? value^ 011 the upper adsorbent with any reasoliable degree of p i ~ i e i o n . PROCEDURE
Preliminary work was carried out using silicic acid as the upper adsorbent and Florid as the lower one, u.qing a number of typical adsorptives having R values from 1.00 to 0.033. It was soon learned that a certain minimum length of upper adsorbent column was necessary in order to obtain connktent, values for this adsorbent. The minimum lerigt,h increased with increasing R value on the upper adsorbent SO that for R values of about 0.1 to 0.3, a rolunin 10 to 15 mm. in length could be used, while for R values from 0.5 to 1.0, the length of the upper adsorbent column should hc 30 to 40 mm. (The upper adsorbent should be a t least ll/z times as loiig as the adsorbate zone width.) The method of making the requisite calculations can best be made clear hy wing a specific example and carrying out t’he calculations i i i three steps as follows: EXPERIMESTAL DATA
1,ength of upper adsorbent’Ai,20 mni. Length of lower adsorbent B, 60 mm. Distance leading edge of adsorptive has moved into 13, 10 1n1n. R value of adsorptive on adsorbent B, 0.50. Rat,io between the distance a given volume of solvent travels in adsorbent -4to that traveled in B, 1.12. Total distnncc developing solvent haq moved, 80 nun.
V O L U M E 26, NO. 5, M A Y 1 9 5 4
929
Knowing the distanre that the leading edge of the adsorptive has moved into B and the R value in this adsorbent, the distance that the solvent must have moved down B after the adsorptive entered this adsorbent can be calculated: lO/D, = 0.50
-
Table 11. R Values of Some Ketones on Carbon as Determined by Indirect 3Iethod Number of Carbon Atoms
R Ketone JIethylmethyl Methyl ethy Methyl propyl Methyl isopropyl Diethyl Methyl butyl I I e t h v l isobutvl Cvcldhexanonk
D, = 20 mm. Since the column of adsorbent B was 60 nim. long and the solvent was run just to the bottom of this adsorbent, it follows that the solvent moved 60 - 20 = 40 mm. down adsorbent B before the adsorptive had moved into adsorbent B-Le., had moved through the 20 mm. of adsorbent A. Converting this into terms of adsorbent A only, i t can be calculated t h a t the solvent moved 20 40( 1.12) = 64.8 mm. through A while letting the adsorptive pass through the 20 mm. of this adsorbent. Since the R value is the ratio between the distance moved by the adsorptive and t h a t moved b y the solvent through an adsorbent column, the R value of the adsorptive on A may be calculated as:
8
9 9 10 11 12 13 14 15 15 16 17 18 19
R A = 20/64.8 = 0.31 DISCUSSION OF RESULTS
T h e results obtained on silicic acid b y the "indirect method" juqt described are summarized in Table I. The incorrect values found b y using too short a column of upper adsorbent are included in this table to indicate the magnitude and direction of the resulting error. It is rather surprising t h a t the use of too short a column leads to R values t h a t are too low. The results obtained by the proper use of the indirect method, holyever, are reawnably close to those obtained b y the usual techniques.
and Indirect Methods" Indirect Method Direct Adsorptiveb 10-50 nim. 20-50 mm. Method Anisolp 1 00 1 00 ~.~~~.... 1.00 0 69 Nitropropane 0.78 0 84 0 69 0.82 m-Dinitrobenzene 0.81 0 57 0 7.4 Benzaldehyde 0.71 Dimethylaniline 0 61 ... 0 64 0 54 Allyl ethyl ether ... 0 56 0 42 0 41 Diethyl ketone ... 0 34 0.31 Aniline 0.32 0 19 0 .17 Benzyl alcohol ... 0 03; 0.033 E t h y l alcohol ... Florisil used as lower adsorbent a n d benzene as developing solvent. b Adsorbate zones located on lower adsorbent (Florisil) by use of streak reagents ( 2 ) . Solutions of 0.01 .If concentration were used as described
n 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ti9
63 34 60 29 51
55 43 41 41 36 31 32
30 28 2'J
7 I
Y
2.0
!
1.0
; h
--
0.4
-
0.2
-
I 0.6
R Values on Silicic Acid as Determined by Direct
Methyl octyl Methyl nonyl Methvl decvl M e t h s l undecyl Methyl dodecyl Methyl tridecyl Dibenzyl Methyl tetradecyl Methyl pentadecyl lMethyl hexadecvl LIetIiyi heptadecyl
3.0
E Table I.
0 i9 0 79 0 78 0 89 0 79 0 73 0 86 0 80
0
8
+
Value
O
;f I
I
30 60 100 PO0 300 MOLAR WEIGHT OF SIDE C H A I N
Figure 1. Absorption .iffittities Carbon of Straight-Chain AIethyl Ketones in Benzene Solutions
on
(J,.$).
;\fter it had been shon-n that the method worked ne11 with silicic acid, a system for which the results could be checked, the method was next applied to determine R values of some simple ketones on carbon (Pfanstiehl Xorit A). These data were desired in order t o obtain some idea of the factors involved in adsorption on carbon and to compare the function of the side chain with that previously observed for silicic acid ( 4 ) . The same s e r i e of aliphatic ketones was used in this work with results as I few ketones of varying types of side summarized in Table 11. : chains have been included in t)his tabulation to point out that theqe factors are also important in determining the degree of ad3orption obtained. I n general, the results for the aliphatic straight-chain methyl ketones show that adporption of these materials on carhon becomes progressively stronger as the length of the side chain is increased. Figure 1 shows the linear log-log plot obt,ained from these data when the adsorption affinity, (1 - R ) / R , is plotted against the molecular weight of the side chains of these ketones. T h e data (with the exception of the first two points) may be represented b y t h e equation of this straight, line: log ( 1
-
R ) / R = log k
+ n (log M S c )=
log (0.000375)
+ 1.6(log 'Wac) (1)
The meaning of the variou.* terms i.j i s espiained in the earlie:. work on silicic acid ( 4 ) . T h e very low value of k found for cartion indicates that the interactions between the carbonyl group and the carbon adsorbent surfaces are very \Teak and ~ o u l dnot cauw appreciable adsorption of the ketones if operative alone. It appears that the relatively strong adsorption of these material; on carbon must be primarily due t o the strong affinity of carbo11 for the organic side chains. This is evidenced bg the positive exponent of M3cin the basic equation: ( 1 - K ) , ' R = k ( J t 8 c p , ACKNOWLEDG\IEST
T h e authors wish to acknowledge their indebtedness t o the Office of S a v a l ResearLh, whose generous sporiqorship ha4 made this work p o 4 b l e . LITERATURE CITED
(1) LeRoaen, -1. L., J . Am. Chem. SUC., 64, 1905 (1942,. (2) LeRosen, A. L., etal., ;INAL. CHEM.. 22, 809 (1%o:8. (3) Ibid., 23,730 (1951). (4) Ibid., p. 73'7. ( 5 ) Weil-;\Ialherbe, H., J . C h e m SOC.,1943,303. RECEIVEDfor review August 5 , 1953. .iccepted December 30, 1953. Presented before the Division of Colloid Cheniistry at the 117th IIeeting of t h e AMERICAX CHEMICAL SOCIETY, Houston, Tex.
