192
ANALYTICAL CHEMISTRY
Acute Bisectrix. yAc = 2 ” in obtuse 8. Extinction. a i a = 39” in obtuse p. Molecular Refraction ( E ) . q z = ‘1.523. R(ca1cd.). = 37.6. R(obsd.) = 37.0. THERMAL DATA(determined by W.C. hlccrone). Pimelic acid melts a t 103” t o 1oj” C. and resolidifies spontaneously to give long rods elongated parallel to b. The optic axial plane lies crosswise of these rods and the crystals may show Bz,, Bz,, or optic axis interference figures; the Hz, or optic axis figures are most common. The optic axial angles are 2Ha = 110”; 2Va = 111”; 2 8 , = 67”. In a mixed fusion with thymol the crystals are not too well formed but usually show square ends with beta parallel to the
length less than the refractive index of thymol; the other index is usually gamma or gamma prime and therefore greater than thymol. Pimelic acid shows boundary migration a t temperatures just below the melting point. This is evident from the penetration of one crystal into its neighbor after primary crystallization is complete.
Thioacetamide in Place of Gaseous Hydrogen Sulfide for Precipitation of Insoluble Sulfides
tests. A tiny spot of the dye mixture is deposited in the channel. Somewhat beyond the sample, a fine spot of monochromatic light is focused on the paper, and on the opposite side of the sample a suitable eluting solvent is added from a microcapillary. As the eluting liquid passes over the sample, the components of the mixture are driven preferentially toward the light scanning zone. As each of these passes the spot of light, the transmittancy and reflectivity of the paper are modified. ‘We have followed the process by focusing the emergent light on a photomultiplier tube and measuring the photocurrent with a Brown Electronik recording potentiometer. Complete separation of binary mixtures in microgram amounts has been achieved in 45 seconds. The speed and sensitivity are largely due to the use of the confined channel. The details of this as well as the nonoptical methods are being submitted to ANALYTICAL CHEMISTRY. R A ~ PH. H MULLER DORE L. CLEGG New York University New York, N. Y .
LITERATURE CITED
(1) Caspari, J. Chem. SOC.London, 1928, 3235. (2) Groth, “Chemische Kristallographie,” Vol. 3, Engelmann, 1910. (3) Latour, Compt. rend., 201, 479 (1936).
p.
495, Leipzig,
HIOACETAMIDE has been successfully used in place of Tgaseous hydrogen sulfide in the development of new methods for qualitative analysis of cations of Groups I1 and 111. Thioacetamide does away almost entirely with the disagreeable odor associated with gaseous hydrogen sulfide. A water solution is added directly to the solution from which the cations are to be precipitated. Thioacetamide eliminates the use of hydrogen sulfide cylinders, generators, and other undesirable means of obtaining gaseous hydrogen sulfide. No great excess of thioacetamide is necessary. Nearly equivalent amounts of the organic sulfide and the cations will bring about complete precipitation of the insoluble metal sulfides. The hydrolysis of thioacetamide gives a relatively low concentration of the sulfide ion in solution, which favors the rapid coagulation and filtration of the insoluble sulfides. The time required for the complete precipitation of the insoluble sulfides by the use of thioacetamide is less than the overall time required when gaseous hydrogen sulfide is used. Thioacebmide is an easily obtainable commercial product. The odor is not unpleasant. It is soluble in water, keeps well in solution, and per unit precipitation is less in cost than gaseous hydrogen sulfide. H. H. BARBER Symposium on Spectroscopic Light Sources. Special Technical EDWARD GRZESKOWIAK Publication 76. 80 pages. American Society for Testing University of Minnesota Materials, 1916 Race St., Philadelphia, Pa., 1948. Price, $2. Minneapolis, Minn. The paper and discussions appearing in this volume were presented at the 1946 annual meeting of the American Society for Testing Materials, held in Buffalo, N.Y., under the sponsorship of Committee E-2 on Spectrographic Analysis. In addition to the introduction by E. B. Ashcraft, RIonsanto Chemical Co., it APER chromatography is being revived as an important adincludes the following papers: “Present Status of Excitation in junct in the analysis and identification of protein hydrolysates, antibiotics, and otherwise difficultly separable mixtures. Spectrographic Analysis,” B. F. Scribner, National Bureau of Standards; “Controlled Spectrographic Spark Source,” J. H We are engaged in the development of instruments to record Enns and R. A. Wolfe, University of Michigan; “Some Propercontinuously the process of diffusion through special paper maties of Gas Discharges Used as Spectral Sources,” R. C. Mason, trices which not only reveal the dynamics of the process but yield Westinghouse Research Laboratories; and “Short-Period Phequantitative analyses of the mixtures. Optical, conductometric, nomena in Light Sources,” by G. H. Dieke, Johns Hopkins Uniand dielectric criteria of diffusion have been found useful in this versity. The prepared discussions mere presented by R. H. technique and possess individual advantages in specific applicaBell, Lucius Pitkin, Inc.; Wendell R. Koch, U. S. Army Air tions. Corps; C. J. Feuhaus, International Nickel Co.; E. K. Jaycox, We have succeeded in recording the chromatographic separaBell Telephone Laboratories; J. R. Churchill, Aluminum Comtion of microgram quantities of dye mixtures on paper by an pany of America; AI. F. Hasler, Applied Research Laboratories; optical method. We have prepared restricted rectangular chanJ. L. Saunderson, Dow Chemical Co.; P. R. Irish, Bethlehem nels on ordinary filter paper by embossing the paper with parafSteel Co.; and L. W. Strock, Saratoga Springs Foundation. fin barriers, similar to the familiar techniques of confined spot
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Automatic Paper Chromatography
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