c. Figure 1. Orthographic Projections of Several Typical Crystals of Dirnethlyglyoxime
X-RAY DIFFRACTION DATA(determined by -W. C. McCrone). I Cell Dimensions. a = 6.07 d.; b = 6.39 A,; c = 4.48 d.
Formula Weights per Cell. 1. Formula Weight. 116.12. Density. 1.353 (pycnometer); 1.32 (x-ray). OPTICALPROPERTIES (determined by W. C. McCrone). Refractive Indexes (5893 A,; 25" C,). u = 1.40 + 0.01. 0 = 1.54 * 0.01. y = 1.85 + 0. 1 Optic Axial Angles (58931:; 25" C.). 2V = 80'. Dispersion. T > v. Optic Axial Plane. Approximately pasdlel to 100. Sign of Double Refraction. (+). Acute Bisectrix. Approximately parallel to b. Extinction. 1' on 100 with y' almost psrallel to b. Molecular Refraction (R)(5893 A,; 25" C.). #/aav = 1.59. R (calcd.) = 29.7. R (obsd.) = 29.0. FUSION DATA (determined by W. C. MoCrane). The literature melting point of dimethylglyoxime is 260-266' C. However, under the usual conditions of fusion between a cover glass and slide the sample sublimes completely before melting. The sublimate is made up of large rods and tablets elongated parallel to b and usually lying on 100.
Kinetics of Paper-Chromatogram Development EVERAL concepts and criteria have been proposed to put the valuable techniques of paper-chromatography on a quantitative basis. Well known among these are the Ra value as defined by Consden, Gordon, and Martin ( 1 ) and the expressions of Flood (g) and of Hopi (3)relilting zone radii to the concentrstion. Nevertheless, it is becoming increasingly evident that kinetic studies an the process of paper chromatogrrtm development can throw much light on the nature of this complex phenomenon (4,5). We have derived and confirmed a simple expression relating the motion of solute and colored zones to elapsed time for the paper disk chromatogram described by Rutter (6). In this useful technique, a narrow rectangular strip is cut in a circular disk of filter paper from its circumference t o the center. The narrow strip is bent downward in a plane perpendicular to that of the horizontal disk. The mixture to be separated is deposited on the center of the disk or on the pendant strip, and when the latter is immersed in the eluting liquid, it acts as a wick to admit eluent to the Sample. Eluent and colored zones soon diffuse outward and eventually develop in the farm of concentric rings. For the conditions under which solvent access occurs a t a constant rate, we may write v = ct where v = volume, 1 = time, and c = a constant,
At any instant, the liquid occupies a circular spot on the paper disk, for which the volume is given by: v = rfjd
where T = radius, d = thickness of paper, and f = accommodation factor. Combining these and lumping all constants, we can write: r? = at
If the transport of colored components follows the same relationship, but a t different rates, then for successive zones, nP= bt, r? = ct, etc. This parabolic relationship has been confirmed for various solvents and several binary mixtures of dyes. It holds for the maximal, minimal, and median sone radii, but obviously with different slope factors. Furthermore, because the RF factor is defined as the ratio of the distance traversed by a colored sone to that traversed by the solvent, we have in this case:
where rs = zone radius and r, = solvent radius
ANALYTICAL CHEMISTRY
1430 This will hold at all times t for which there is a perceptible difference in the positions of the zones. As the slope factors a, b, etc., can be determined with considerable precision from a plot of the square law data, thefhvalue so computed is more convincing than a result obtained from two zone positions. A similar relationship appears to hold for separations accomplished in vertical rectangular strips in which the eluent is rising, although it is derivable from a different set of assumptions. Our measurements are not well enough along to decide upon its validity or usefulness. Experimentally, it has been found convenient to mark off radial target points on the paper disk with fine pencil dots and in the square law sequence of intervals. Under these conditions, the various components should cross successive target positions in uniform time intervals. To avoid confusion when dealing with complex mixtures, it is useful to have a multipen chronograph for accurate timing and identification. As a substitute, we used a simple tapped voltage divider with push buttons to connect identifying potentials to a recording potentiometer. The chart drive was synchronous and each push button was labeled to represent the various components and solvent. The principal limitation in precision seems t o lie in deciding when a zone crosses a target point. Although this source of error is minimized by appropriate illumination and viewing, automatic recording is advantageous, especially in view of the long time periods involved. It has been found feasible to project minute points of light on the paper in the square law sequence and record the transmitted light photoelectrically. An increase in translucency of about 35% occurs as each target point is moistened by advancing solvent and decreases occur as colored zones cross the points in proportion to the absorbance.
3-ml. sample solution in a 30-ml. test tube, add 1 ml. of reagent 1 and 1 ml. of reagent 2. Close the test tube and shake well, then allow the mixture to stand a t 20" to 25' C. Observe any color change which appears in 2 hours. Some ketones will be found which are not soluble in water alone. In that event, shake the solid sample with 1 ml. of 9592 ethyl alcohol, centrifuge, and decant. Place the clear decantate in a test tube and add water to it dropwise until a turbidity appeari, then add 95% ethyl alcohol dropwise until the mixture clears with shaking. Use this solution as the test sample and treat it a s described for samples soluble in water alone. Sample Glucose Sucrose Lactose Maltose
(2)
(31 (4) (5) (6)
Consden, W.G., Gordon, A. H., and Martin, A. J. P., Riochem. J . , 38, 224 (1944)., Flood, 2.a m l . Chem., 120, 327 (1940). HoDf. P. P.. J . Chem. soc.. 1946. 785. M&r, R. H., and Clegg, D. L., AFAL.CHEM., 21, 192 (1949) Ibid., 21, 1123 (1949). Rutter, L . , S a f u r e , 161, 433 (1948).
RALPHH.MULLER DORISL. CLEGG New York University New York 3, N. Y. RECEIVEDSeptember 29, 1949
A New Test for Fructose HE use of 3,5-dinitrosalicylic acid as a test for reducing Tsugars in urine has been reported by Sumner ( 2 ) and Short ( 1 ) . Sumner used a slightly alkaline solution of his reagent and heated the urine sample with the reagent in boiling water for 5 minutes. Short reported that more reliable results were obtained if Sumner's reagent were made more strongly alkaline with sodium hydroxide. In both methods, a color developed with any of the reducing sugars. The present investigation is part of a study to develop a systematic scheme for the qualitative analysis of a mixture of the common sugars: glucose, fructose, lactose, maltose, and sucrose. Reagents. (1) Dissolve 2 grams of 3,5-dinitrosalicylic acid in 'TO ml. of distilled water a t 80" to 90" C., and add 10 ml. of 20% aqueous solution of sodium carbonate. When this mixture has cooled to 20" to 25" C., dilute to 100 ml. with distilled water. (2) Dissolve 1.5 grams of sodium hydroxide in enough distilled water to make 100 ml. of solution at 20" to 25" C. Experimental Procedure. If the sample is a solid, dissolve 0.2 gram in 3 ml. of distilled water. If the sample is a liquid, concentrate it on a water bath until its specific gravity is approximately 1.1 at 20' C., and take 3 ml. of this concentrate. To the
Minimum Time for Orange Color t o Develop, Hours 3 Remains yellow 13
13
Remains vellon 50 m
