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. I n 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)
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 a t 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 a t 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
