1090
A N A L Y T I C A L CHEMISTRY
what abnormal and is probably due, in part, to the fact that different photometers \\ere used for the two measurements. I n any case the precision is considered satisfactory for routine work. The accuracy was determined by adding known amounts of manganese to 2.5-gram portions of a sample of magnesia in which 0.0028% of manganese was found. The added manganese was recovered within the precision of the method (Table VI). Phosphorus. A colorimetric method was selected for determination of phosphorus because of the low concentration present. After a survey of the literature the reduced phosphomolybdate method of Dickman and Bray (5) was adopted because it was applicable in the presence of hydrochloric acid and iron. The author confirmed the findings of Dickman and Biay regarding the effect of acid concentration, ammonium molybdate concentration, and stannous chloride Concentration as well as the jtability of the color. Spectral absorption data indicated that the colored compound had a minimum transmittancy between 740 and 760 millimicrons. Accordingly, a red (Wratten F-29) filter was selected for the color measurement. Silica also reacts with molybdate to give a silicomolybdate which has properties similar to that of the phosphomolybdate. However, the acidity required for the formation of the reduced phosphomolybdate is much greater than that required for the formation of the reduced silicomolybdate and should be great enough to prevent the formation of the latter. &loreover,silica added in the form of a soluble silicate had no effect upon the intensity of the color when present in concentrations as high as 2 mg. Since the preparation of the sample includes a step for the separation of silica, higher concentrations of silica are not expected. Moreover, the accurate analysis of Bureau of Standards magnesite 104, which contains 2.54% silica, as described below, indicates that silica does not interfere. Dickman and Bray found that ferric iron did not interfere when present in concentrations of less than 15 p.p.m. but that it was riecessary to reduce higher concentrations of iron to the ferrous atate prior to color development. As iron is usually present in magnesia in concentrations sufficient to give a concentration of more than 15 p.p.m. in the final aliquot, hydroxylamine hydrorhloride is added to reduce the iron. I t was shown that this procedure eliminated iron interference even when the iron-phosphate ratio was as high as 100 to 1 by analysis of Bureau of Standard3 magnesite 104, which has a stated ferric oxide content of 7.07y0 and a phosphorus pentoxide content of 0.05770. Replicate analy-
Table VI.
of Method for 3Ianganese hlanganese Recovered Error
4ccuracy
Manganese Added 70
70
0,0008 0,0020 0.0040
0.0081
o/o
0.0014 0.0024
f O ,0006
0.0037
- 0.0003
0.0080
-0.0001
+ O ,0004
ses by the above procedure gave 0.058, 0.033, 0.059, and 0.05970 phosphorus pentoxide in this sample. ACKNOWLEDGMENT
The author hereby acknonledges the contributions of H. H. Hartzell (deceased), T. Woodn ard, F. Melhase, H. Leitch, and F. R. Brooks to the development of most of the methods cited and to Dvr.ight Williams and George S.Haines of the Technical Department ‘of \Testvaco at South Charleston, IT. Va., for developmental data and advice on these procedures. Appreciation is also expressed to C. W.Redeker of the Xen-ark Control Laboratory for somr of the experimental data and summaries relating to precision. LITERATURE CITED
(1) Allen, E. T., J . Am. Chem. SOC.,25, 421 (1903). (2) Axelrod. J., arid Swift, E. H., I b i d . , 62,33-6 (1940). (3) Bluni, W., Bur. Standards Sci. Paper 286 ( M a y 10, 1916). (4) Caley, E. R., and Elving, P. J., ISD.ESG. CHEM.,ASAL.ED.,10, 264 (1938). (5) Dickman, S. R., and Bray, R. H . , Ibid., 12,665 (1940). (6) Fortune, W. B., and Mellon, M .G . , I b i d . , 10,60 (1938). (7) Gooch, F.h., a n d H a v e n s , F. S., Am. J . Science, 2 , 4 1 6 (189ti). (8) H a m m e t t , L. P., and Sottery, C. T., J . Am. Chem. Soc., 47, 142 (1925). (9) Hess, W.H., and Campbell, E. D., I b i d . , 21, 776 (1899). (10) Hillebrand, W.F., and Lundell, G. E. F., “Applied Inorganic Analysis,” pp. 722-5, New York, John Wiley & Sons, 1929. (11) Mehlig, J. P., IND. ESG.C H E M . AXAL. , ED.,11, 274 (1939). (12) Moran, R. F., I b i d . , 15,361 (1943). (13) Olsen, A. L., Gee, E. A , , and McGlendon, V., I b i d . , 16, 169 (1944). (14) Saywell, L. G., and Cunningham, B. B . , I b i d . , 9, 67 (1937). (15) Willard, H. H., a n d Cake, W.E., J . Am. Chem. Soc., 42, 2208 (1920). (16) Willard, H. H., and Greathouse, L. H., I b i d . , 39, 2366 (1917).
RECEIVED February 24,1948.
‘Chromatographic Behavior of Some Aldehydes ARTHUR L. LEROSEN
AND - 4 L E X A N D E R
MAY’
Louisiana S t a t e University, Baton Rouge, La.
T
HERE are many data in the literature concerning the effect of changes in the number of adsorbed groups per molecule on the adsorption sequence in chromatographic columns. Two examples will illustrate this point, the increase of adsorption affinity with increasing number of double bonds per molecule in the carotenoid series given by Zechmeister (S),and the increase of adsorbability due to lengthening the carbon chain in hydrocarbons adsorbed on charcoal which has been excellently worked out by Claesson ( I ) . I n the present work the authors have studied the relation between side chain and R values in a series where the aliphatic side chain is essentially not adsorbed ( R is the rate of movement of the zone relative to the developing solvent. 21. ,
I
IPresent address, Chemistry Degartment, B o u t h w estrln Loiii5ianh Institiit?, Lafayettr, La.
The aldehydes were selected for this purpose, as they show good rates of movement on silicic acid when benzene is used as the developing solvent; they are easily detected by a solution of pararosaniline bleached by sulfur dioxide (Schiff’s reagent). The data for the limited number of aliphatic aldehydes available during the progress of this study are given graphically in Figure 1. I t is evident that the side chain acts as a hindrance to adsorption and thereby leads to an increase in the value of RLwith increasing number of carbon atoms The values of R, for the trailing edge were not significantly different from R( and are not given. The data for all experiments (Table I) indicate that a double bond (crotonaldehyde) produces a stronger adsorption than would be observed for the corresponding saturated compound, 0.284 compared to an estimated value of 0.475
V O L U M E 20, N O . 11, N O V E M B E R 1 9 4 8
1091
A study of the chromatographic behavior of aldehydes chromatographed on silicic acid from benzene show-s that the rate of movement of zones increases with the length of the carbon side chain and is decreased by unsaturation in this chain.
for Ri butyraldehyde. Furfural, which also contains oxygen, and the aromatic aldehyde support this observation. As indicated in Table I, the R1 values for the aliphatic aldehydes are sufficiently different to indicate the possibility of separating these compounds on the column, and this separation was easily accomplished experimentally. The phenyl aldehydes were only partially separated on the columns used (75 mm.) in agreement with the small differences between their R valuey. The separations observed were actually better than expected. The column used did not allow a complete separation of heptaldehyde from benzaldehyde, although the rates of the two zones indicate this to be just possible for a zone 15 mm. !\+de on the 75-mm. column.
0.8
c
4-
/
I
0'4
I
/
t
1
@
L
0
1
,
/
7
2
3 4 5 6 NO. OF CARBON ATOMS
7
8
9
70
Figure 1. Dependence of RLfor Some Aliphatic Aldehj-des on Number of Carbon Atoms in Aldehyde Adsorbent. Silicic acid Developer. Benzene
The initial volume was 1 ml. and the initial concentrations were W for all aldehydes except formaldehyde, which was 0.005 i 0.008 M . EXPERIMENTAL
Apparatus. Thc chromatographic tubes med in this study \veie 0 X 130 mm. tubes made b r the Scientific Glass Apparatus Com.. pany, Bloomfield, N.
