place down the column. However, during analysis of the mixture, an initial flow rate decrease takes place as a result of adsorption of carbon monoxide. The nornial gas peak obtained for hydrogen in the mixture m-ill be different from that obtained in the calibration, as the column conditions are completely different (8). Such interference has already been reported for another system (6). It occurs regardless of the method used for peak measurement, as both peak height and area are affected by velocity changes (8). For optimum operation n.ith thermal conductivit: detectors, pressure changes should be kept small. Such changes augment flow changes and incrcase errors from this source. Measures for rernedying base line instahilitj which do not minimize pressure changes are satisfactory for the first type of interference, but conditions for analysis may still be far from optimum. Errors caused by the second (velocity) type of interference can be further
minimized by using small samples, and can be eliminated completely by using either a n integral detector or one which records constant peak areas regardless of gas velocity. Other interesting aspects of the argon Molecular Sieve system will be reported elsewhere. Although undesirable from an analytical viewpoint, the adsorption peak phenomenon may prove of considerable value in studying the kinetics of coniplex adsorption and desorption processes.
ACKNOWLEDGMENT
The author is indebted to P. L. Walker, Jr., and H. B. Palmer of this department, and to J. R. Lotz, 11. H. Bnrsky, and L. W. Littau of the chemistry department for discussion and review of this paper. He is also indebted to A. Roeger, 111, and L. J. Duffy of this department for their technical assistance.
LITERATURE CITED
(1) Dimbat, bl., Porter, P. E., Stross, F. &I., A N A L . CHEM.28, 290 (1956). ( 2 ) Harrison, G. F., "Vapour Phase Chromatography," D. H. Desty, ed., p. 332, Academic Press, New York, 1957. (3) Janak, J., Ilrejci, X , Dubsky, H. E., Collection Czechoslov. Cheni. C o r n i m n .
24,1080 (1959). (4) Kyryacos, G., Boord, C. E., BYAL. CHEX 29, 787 (1957). ( 5 ) Nodop, G., 2. anal. Chem. 164, 120 (1958). (6) Smith, R. E.,Sminehart, J., Lesnini, D. G., -4s.4~.CHEM.30, 1217 (1958). (7) Sullivan, I,. J., Lotz, J. R., Willingham, C. B., Ibid., 28, 495 (1956). (8) Van de Craats, F., "Gas Chromatography 1958," D. H. Desty, ed., p. 248, Academic Press, New York, 1958. ALLANWEISSTEIS
Department of Fuel Technology Pennsylvania State University University Park, I'n. RECEIVEDfor review April 17, 1959. Bccepted October 5, 1959. Excerpted from a thesis to be presented to the faculty of the Pennsylvania State University in partial fulfillment of the requirements for the Ph.D. degree.
Gas Chromatographic Separation of Metal Halides by Inorganic Fused Salt Substrates SIR: Freiser ( 2 ) has recently reported the separation of the low boiling tetrachlorides of tin and titanium (boiling point, 114' and 136" C., respectively) using a n-hesadecane column a t 102" C. The separation of metal halides using organic stationary liquid phases, hon ever, is frequently not practical, because organic compounds are generally too volatile to be used a t the temperatures required for many inorganic separations. &o undesirable reactions often occur betn een active metal halides and conventional organic liquid phases. Metal halides may be separated b y partition gas chromatography using fused salts as the stationaryliquid phase.
A chromatograni of titanium (IV) chloiide (boiling point, 136" C.) saturated a t room temperature nitli antimony(II1) chloride (boiling point 225" C.) is shown in Figure 1. A 35-pl. sample was injected with a hypodermic syringe. I n quantitative work hydrolysis must be prevented a t
the tip of the syringe. Dry nitrogen, flowing at a rate of about 30 ml. per minut'e, served as carrier gas. The column was packed with Johns-hfanville C-22 insulating brick (Sil-0-Cel) ground to 30/GO mesh and coated with a n eutectic mixture of anhydrous bismuth tricliloridc and lead chloride (89 moly 5 I(iCI.l, ntrlting point, 217" (3,).
-i c
0 .c 0
An all-glass column and detector cell was constructed from borosilicate glass tubing 6 mm. in outside diameter. Vycor tubing is required for column temperatures above approximately 520" C. Stainless steel or copper tubing cannot be used because of reaction with the fused salt and with the metal halides being separated. The apparatus consists of a flash vaporizer; a 12-foot borosilicate glass column in the form of two concentric helices, 5 inches in height and 3 inches in outer diameter; and a i)latinuni filament thermal conductivity detector cell ( 1 ) forming one arm of a conventional Wheatstone bridge arA 1x11 insulated, highrangement. vnttage fi\:ed resistor n a s used as the rciference "cell." 290
ANALYTICAL CHEMISTRY
a, c
a
c3 L Q)
B
0 a,
CK
0
I
I
I
5
IO
15
Figure 1 . Gas chromatographic separation of titanium tetrachloride solution saturated a t 27" C. with antimony trichloride Column, BiCI3-PbCI:: eutectic mixture on C - 2 2 firebrick; column temperature, 2 4 0 ' 5 1 ' C.
The Sil-0-Cel had previously been thoroughly washed with hydrochloric acid to remove iron and basic impurities and dried several hours at 260" C. The dry Sil-0-Cel was added with continual stirring t o the eutectic mixture while the temperature of the mixture was maintained above the nielting point of the eutectic. The eutectic mixture constituted about iOyo by weight of the column packing matcrial. With the column operated at 240" C., the retention times for titaniumIIV) chloride and antimony(II1) chloride were found to be 2.0 and 12.0 minutes, respectivply. The choice of fused salt is dependent upon several factors: The fused salt should be a good solvent for volatile inorganic compounds. In general the effective-
ness of the molten salt medium as a solvent is increased as the temperature of the column is decreased. For example. tin(1V) chloride and antimony(II1) chloride pass rapidly through a 12-foot column and are only partially separated when run a t 474" C. on a cadmium chloride-potassium chloride eutectic column (33 mole % KC1, melting point, 383" C.). The fused salt should have low vapor pressure a t the temperature of the column. The aluminum chloride-sodium chloride eutectic (41.1 mole yo SaC1, melting point, 126" C.) has only limited applicability because of the low sublimation temperature of aluminum chloride. The fused salt should, in general, possess a common ion with that of the
solute molecules. This condition minimizes the possibility of undesirable reactions in the column. Kitrate eutectics cannot be used for the separation of metal chlorides, because nitrates behave as strong oxidizing agents and decompose in the presence of tin(1V) chloride and titanium(1V) chloride. LITERATURE CITED
(1)'Dal Nogare, S., Safranski, L. W,, ANAL.CHEX.30,894 (1958). ( 2 ) Freiser, H., Ibid., 31, 1440 (1959). R. S.JUVET F. hl. '\V.4CHI Department of Chemistry and Chemical Engineering University of Illinois Urbana, Ill. RECEIVEDfor review October 1, 1959. Accepted Kovember 16, 1959.
A N e w Color Reaction for Methacrylate Monomer and Polymer Identification SIR: illethyl methacrylate resins can be distinguished from acrylate resins by a very simple and rapid color reaction, no mention of which was found in the literature. This test has been applied with very good results to many samples of methacrylate and acrylate resins and monomers from different sources, Depolymerize in a test tube about 0.3 gram of sample, protecting against the escape of monomer vapors by a piece of filter paper fixed with the clamp n-hich holds the tube. T o the drops of condensed monomer in the test tube add
a few milliliters of concentrated nitric acid (specific gravity 1.40) and heat gently over a small flame. I yellow color appears in the limpid solution. Cool, and add half the volume of water and then zinc powder.
This same blue color appears if sodium nitrite is used instead of zii:c powder. This seems to be the only color reaction hitherto mentioned for methacrylate resins.
A blue color is immediately developed if methacrylate resins are present in the sample. This blue color can be easily layered to chloroform, dcepening the color. The yellow component which initially is formed is not extracted by chloroform. Excess zinc turns the solution colorless.
Instituto Nacional de Tecnologia Laboratorio de Borracha e Plhsticos, Avenida Venezuela, 82, Rio de Janeiro, Brazil
ELOISAB. XANO
RECEIVEDfor review October 26, 1959. Accepted Xovember 20, 1959.
Metallic Zinc as a Catalyst for Quantitative Acetylation of Some Hydroxy Compounds SIR: Acetylation of some hydroxy compounds of high molecular weight 11ith dilute nonaqueous acetyl chloride solutions proceeds rather slonly a t ordinary temperatures in the absence of catalysts. The presence of metallic zinc greatly increases the rate of acetylation of such compounds as poly(propy1m e glycol), 2,2 '-t hiobis (4-me t hyl-6tert-butylphenol) , and glycerol monoricinoleate. Poly(propy1ene glycol) required more than 5 hours a t 35" C. t o esterify completely in the absence of zinc, but less than 30 minutes in the presence of the metal. As a n example, determination of the hydroxyl content of poly(propy1ene
glycol) (molecular weight ea. 1850) is given. Poly(propy1ene glycol), 5 grams (ea. 0.005 mole of hydroxyl), is weighed into a specially made thin-m-alled glass bulb of ca. 40- to 45-cc. capacity and 15 cc. of 0.6JI acetyl chloride in toluene (ea. 0.009 mole of acetyl chloride) is pipetted into the bulb followed by 1 cc. (ea. 3 grams) of zinc metal (c.P. grade, 20mesh granules). The stem is sealed, and the bulb is immersed in a water bath thermostatically controlled a t 35" C. After 25 minutes the bulb is taken out of the bath, immersed, and crushed into a measured volume of standard sodium hydroxide solution diluted with water. Isopropyl alcohol
is noiy added (enough to give a onephase system), and the solution is titrated with the standard sodium hydroxide to a deep blue color of thymol blue indicator. A blank is run similarly. Results obtained by the standard phthalic anhydride method are somewhat lower than those obtained by the acetyl chloride-zinc method. Typical results are shown in the table. DISCUSSION
The catalytic effect of metallic zinc may be plausibly explained as follows: The metal is a potential Lewis acid producer. The surface of the metal VOL. 32, NO. 2, FEBRUARY 1960
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