12 to 15 approximately equal portions and the column tightly tamped with a wood dowel after each addition. T o avoid compacting the top layer of each addition more densely than the rest, the dowel should not be snug-fit, but the diameter of should be perhaps the column. The packing length of these columns was 122 to 125 mm. Columns were attached to reservoirs of hexane (technical grade) saturated with nitromethane, and 10 to 15 p.s.i. of nitrogen pressure was applied. To flush out excess nitromethane, 30 to 40 ml. of solvent mas passed through each column before use. Columns should not be allowed to run dry. Determination of Relative Rates. T h e dinitrophenylhydrazones were chromatographed in pairs. About 0.3 mg. of each of the tn-o derivatives was placed on t o p of a washed column a n d dissolved in the 0.5 t o 1.0 ml. of solvent above the adsorbent. Nitrogen pressure was applied and, just before t h e column ran dry, a n additional 0.5 to 1.0 ml. of solvent was added. As this disappeared, the reservoir was opened and the column flooded with developing solvent. When the faster component had traveled about 100 mm., the distance from the top of the packing to the center of greatest color density was determined for each band. This ratio was expressed as the relative rate of movement, R,, of one dinitrophenylhydrazone in terms of the other. n-Aliphatic Aldehydes. T h e relative rates of the diiiitrophenylhydra-
Table 1.
Relative Rates of Dinitrophenyl hyd razones”
Parent R, Carbonyl Formaldehyde 0 32 Acetaldehyde 0 40 n-Propional 0 56 n-Butanal 0 75 15 n-Hexanal n-Heptanal 1 8 n-Octanol 2 3 n-Xonanal 3 0 2-Butanone 0 95 ZPentanone 1 3 2-Hexanone 1 7 a n-Valeraldehyde
Parent Carbonyl
R,
2-Heptanone 2-Octanone Acetone 3-Pentanone Methional Crotonal Acrolein Furfural Isobutanal Biacetyl (n-pentanal)
2.3 3.0
0.65 1.4 0.22 0,50 0.22 0.21 2.0 0.15
=
1.00.
.I! ci
50
100
15(
Molecular Weight of Parent Carbonyl
zones of the normal adehydes, C-1 to C-9, were determined with n-pentanal (valeraldehyde) as reference. A plot of log R, against molecular weight approximates a straight line (Figure 1). This line can be represented by the formula log R, = 4.03 - 0.297 M , where ill is the molecular weight of the other parent aldehyde. Table I lists the relative rates, compared to n-pentanal, of the dinitrophenylhydrazones-both of the n-aliphatic aldehydes and a number of other carbonyls of significance in flavor analysis. ACKNOWLEDGMENT
The author acknowledges the technical assistance of R. F. Inderbitzen.
Figure 1 . Linear relationship between relative rates of certain dinitrophenyl hydrazones and molecular weights of parent carbonyl compounds LITERATURE CITED
(1) Cheronis, S . D.. Entrikin, J. B., “Systematic Identification of Organic Compounds,” Interscience, Sew York, 1957. (2) hfonty, K. J., .kX.AL. CHEM. 30, 1350 (1958). (3) Pierson, E., Giella, M., Tishler, hl., J . Ant. Chem. SOC. 70,1450 (1948). (4) Shriner, R. L., Fuson, R. C., Curtin, D . Y.. “Svstematic Identification of Organic compounds,” Kilep, New York, 1956. WALTERG. JENNINGS University of California Davis, Calif.
Modification of a Spot Test for Sulfate Ion SIR: According to Feigl ( I ) , sulfate ion in the form of alkali salt can be detected as follows. Take a drop of neutral sample solution in a crucible, add a drop of pure barium carbonate suspension, heat the mixture to dryness on a water bath, and add a drop of phenolphthalein in aqueous alcohol (1 to I). Appearance of pink color is due to the presence of sodium carbonate produced by reaction BaCOI
+ Na2SOa= Bas04 + Ka2COs
and indicates sulfate. I n the course of a study using this method, i t was found that the pink color appears often even in the absence of sulfate ion. T o examine the cause of this phenomenon, pure barium carbonate free of alkaline impurities was prepared by slightly boiling a solution of barium bicarbonate. (The solution of barium bicarbonate v-as obtained by bubbling carbon dioxide gas through a suspension of pure barium carbonate in water.) Pink coloration of phenolphthalein was again observed in a suspension of this barium carbonate in water, and the p H of the suspension mas 9.3 to 9.5 when measured b y a p H 1 1 18
ANALYTICAL CHEMISTRY
meter with a glass electrode. The pH, calculated from solubility and dissociation constant data, is ea. 9.9 a t 18” C. (2). Value 7.2, Jvhich appears in the literature (3, 4),seems to be too low. The effect of alcohol on the p H of barium carbonate suspension was examined next. As shown in Figure 1, the p H diminishes with the addition of alcohol b u t remains a t a value higher than 8.6 at an alcohol concentration 1 to 1 by volume. This p H is sufficiently high for phenolphthalein to sho\v its alkaline color.
K h e n Feigl’s method was followed with the use of thymolphthalein in aqueous alcohol (1 to l), for which the p H interval of color change is 9.3 to 10.0, no coloration was observed when sulfate ion was absent from the sample solution, From these observations, the use of thymolphthalein in the place of phenolphthalein is recommended. The limit of identification is 4 y of sodium sulfate and the dilution limit is 1 to 10,000. LITERATURE CITED
(1) Feigl, F., “Spot Tests. I. Inorganic
Applications,” 4th ed., pp. 289-90, Elsevier, S e w York, 1954. (2) Kamitani, Y., Fukutomi, T., Scz.
Rept. Fac. Liberal Arts and Educ., Gzju Cniv. 1, 35-8 (1953) (in English). (3) Lundell, G. E. F., Hoffman, J. I., Bright, H. il., “Chemical Analysis of Iron and Steel,” p. 68, Wiley, S e w York,
1931.
(4) Wichers, E., J . Am. Chem. Soc. 46,
1826 (1924).
8.0 30
40
50
A L C O H O L ADDED TO 50 ML. OF BsCOi SUSPENSION, ML.
Figure 1. Change of p H of barium carbonate suspension with addition of alcohol
FIJKUTOMI MICHIKONAKAHARA
T.4KEO
Laboratory of Chemistry Faculty of Liberal Arts and Education Gifu University Gifu, Japan
