I EQUIPMENT Tracking D o w n Traces G a s c h r o m a t o g r a p h y is put to w o r k to m e a s u r e t r a c e impurities a n d to p r e p a r e h i g h p u r i t y m a t e r i a l s Whether de tecting impuri ties, separating highly pure c ο m ρ ο η ents Analytical from complex Chemistry volatile mix tures, or bring ing a packed audience into a late afternoon session of the Division of Analytical Chem istry at Miami, gas chromatography is attracting attention. • For Trace Analysis. The tech nique, for instance, has proved invalu able to D u Pont's Polychemicals De partment for analyses at the parts-permillion level. C. E u g e n e Bennett told the Division of Analytical Chemistry that D u Pont uses a high sensitivity in strument to measure impurities in monomers. Although these impurities are present in only trace amounts, they can drastically alter physical properties of resultant polymers. T h e unit is designed to handle com plex organic mixtures at temperatures u p to 150° C , although Bennett be lieves that its range can b e extended to temperatures u p to about 300° C. merely by using detectors designed for higher temperatures. Heart of the D u Pont instrument is a preamplifier which increases the sig nal from an inexpensive thermistor detector. T h e amplified signal is then fed into a standard recorder. This combination is used because of the high signal to noise level of thermistors and the availability of suitable ampli fiers. T h e instrument, as designed by Ben nett and coworkers, contains an inter changeable stainless steel U-shaped column, V 4 -in. o.d. and 4 to 6 ft. long. Because slight temperature changes are readily detected at the 25 to 100 μν. range at which t h e instrument op erates, exact temperature control is essential. The column, therefore, is protected b y a vapor jacket in which suitable liquids could b e refluxed; other exposed parts are carefully in sulated. In use, t h e test sample is injected into preheated helium carrier gas, which then passes through the column, ST ACS NATIONAL MEETING
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over the detector, a n d through a flow meter into the atmosphere. Reference and detector themistors are set u p as part of a W h e a t s t o n e bridge in which the unbalance signal is constantly am plified and measured on a recording potentiometer. As components of t h e vaporized sample reach the detector, the resulting change in thermistor tem perature produces a corresponding change in resistance.
Trace analysis by gas chromatog raphy, Bennett points out, allows rapid measurements to b e made of individual components in complex mixtures at concentrations t h a t are extremely diffi cult to detect by other means. Among these: isopropyl alcohol in benzene; benzene, cyclohexanol, or other im purities in toluene; methanol i n water; impurities in cyclohexane. Instruments for parts-per-million analysis have been used for about a year at Du Pont for research analyses and now a r e being applied to process control. • S e p a r a t i n g Pure S a m p l e s . With a simple modification, Perkin-Elmer's Vapor Fractometer can be used to produce relatively large samples of very p u r e materials. All that is neces sary, according t o Nathaniel Brenner and Vincent Coates, is t o replace the instrument's standard column with a 1-in. o.d. column, and to build a by pass system into t h e end of t h e column so t h a t the main gas stream flows di rectly to a collecting system and only
φ More Quantitative Chromatography To make quantitative gas chromatography more precise, it is necessary to correct areas u n d e r chromatogram peaks for t h e thermal conductivity characteristics of each com p o u n d being anaylzed, according to Douglas M. Rosie and Robert L. Grob of Esso Research. G r o b (seated Analytical above) and Rosie have investigated t h e thermal con Chemistry ductivity of a number of hydrocarbons with a PerkinElmer Vapor Fractometer, using helium carrier gas. T h e y find t h a t the area under the peaks of chromatograms is not a direct measure of either mole per cent or weight per cent of individual components in mixtures. E a c h compound, they report, produces a significantly large difference in response output of the thermal conductivity cell. When G r o b and Rosie assumed t h a t per cent area equals mole per cent in calculating quantita tive results, they c a m e u p with errors as great as 3 5 % . Closer, but still only approximate, agreement was obtained when they assumed that per cent area under peaks is equivalent to weight per cent. ST ACS NATIONAL MEETING
here's what NATIONAL ANILINE offers
Urethane Producers V.e*9 e oS
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) 1-17 N A C C O N A T E S . . . General Product Information ) I-17A N A C C O N A T E 80 (Tolylcne Diisocyanate Isomeric Mixture) ) I-17B N A C C O N A T E 65 (Toîylene Diisocyanate Isomeric Mixture) ι I-17C N A C C O N A T E 100 (2.4 Tolylcne Diisocyanate) ι I-17D N A C C O N A T E 200 (3,3'-Bitolylene4,4'-Diisocyanate) (TODI) » I-17E N A C C O N A T E 300 (Diphenyimethane 4,4'-Diisocyanate) ( M D I ) ) I-17F N A C C O N A T E 310 (3.3'-Dimethyldiphenylmethanc 4,4'-Diisocyanate) ( D M M D I ) APPLICATION
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For new routes and new products—consider these reactions of
I S O B UTYRALDEHYDE a versatile chemical building block Ν s C—G—C—C—CHO 2, 2-DIMETHYL, 4-CYANOBUTYRALDEHYDE (R)
C—C—COOH 4-METHYL PENTENOIC ACID(R) 2-ETHYLISOHEXANOL (C)
2 , 2, 4-TRIMETHYL-l, 3-PENTANEDIOL (C)
ISOBUTYRONITRILE (C)
C—C—C—C—COH NONYL ALCOHOL (C)
j 1
Products so i n d i c a t e d are a v a i l a b l e from Eastman Chem c a l Products, Inc. in t h e f o l l o w ng quantities: (R) research, (C) commercia
HOC—C—COH C NEOPENTYL GLYCOL (C)
Eastman
CHEMICAL PRODUCTS, INC. K l NGSPORT, T E N N E S S E E
subsidiary of Eastman Kodak Company
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Commercially available in tank car quantities, Eastman isobutyraldehyde is one of the chemical industry's newest building blocks. The reactions indicated here have been selected from among many as receiving the greatest amount of attention since the introduction of isobu tyraldehyde as a basic raw material. Useful in themselves or as intermediates, these derivatives of isobutyral dehyde are becoming increasingly important as a source of solvents, plasticizers, pharmaceuticals, polymers, resins, insecticides, hydraulic fluids and lubricants. Samples of isobutyraldehyde and of those derivatives so indicated are available for your evaluation. Write to us at Kingsport, Tennessee or contact our nearest sales representative.
1957
West
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Coast:
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a reduced stream travels the normal path through t h e detector. Using large-diameter columns, Bren ner is able to isolate the components from such materials as essential oils or chlorinated solvents. One example Brenner cites is separation of a mixture of cis- and trarw-dichloroethylene into two pure isomers. Sizes of samples put through t h e l-in. column range up to 2 ml., although separations of samples of at least 5 ml. probably are possible. W i t h this size of sample, individual components can be iden tified directly b y infrared or ultraviolet spectra or other conventional analytical means. Because of t h e large cross sec tion of the column a n d the large vol ume of gas t h a t will pass through, air or nitrogen is u s e d as a carrier in place of helium.
special plug with accessories for stand ing the high pressures generated. There is a fused silica side window near the e n d plug for looking in while the compressor is fired. In the end plug itself are two recesses for instru ments. Into one t h e NOL workers p u t a piezoelectric pressure gage with a response time of about 5 microseconds. Into the other, they have put anotlier window through which they can either measure t h e radiation emitted by gases at the extreme conditions reached or measure t h e final position of the piston. T h e piston is fired by pressure exerted on it from a gas reservoir large in comparison to the volume of the compressor. Thus, reservoir pressure ends u p at 9 5 % or more of its original value; in this way, a force essentially constant has been applied to the piston during compression.
So far, the N O L researchers have calibrated the compressor with C 0 2 to 20,000 p.s.i. Armed with these cali bration data, they have measured P-V data for nitrogen u p to about 25,000 p.s.i. They have run into a hampering leak problem. Test gas has leaked around die piston to such an extent that con siderable correction of t h e data is needed to make them meaningful. But Lalos and Miss Price feel that this leak age problem will be reduced enough t o allow measurements to 50,000 p.s.i. And, since gases at high density and temperature act as radiators, they ex hibit a continuous spectrum in the visible region. Russian workers have reported this, too. So another phase of N O L work will be a study of this gas radiation at higher pressures (above 30,000 p.s.i. or s o ) .
Compressor for High Τ, Ρ April 22, 1957
A d î a b a t i c compressor d e signed b y N a v a l Ordnance Lab f o r equation o f state studies Most extreme condition work to date has been ACS NATIONAL MEETING either at high Industrial Br * temperatures or Engineering at high pres But Γ Chemistry * s u r e s. Naval Ordnance Laboratory has designed an adiabatic compressor for use at both high temperature and high pressure at t h e same time. NOL's Donna Price and George T . Lalos are a m o n g N O L workers w h o have designed a compressor to develop pressures u p t o 100,000 p.s.i. and tem peratures to 4 0 0 0 ° K. Miss Price told the Division of Industrial and Engineer ing Chemistry's symposium on high pressures the unit is aimed a t reaching these conditions for only a short t i m e about 20 microseconds—by firing a pis ton down a cylinder. T h e compressor has so far developed pressures to 60,000 p.s.i. a n d h a s been used for P-V-T measurements up to 25,000 p.s.i. T h e compressor is very much like a large rifle barrel, only with t h e exit end sealed off. Taking the place of the rifle bullet is a piston three inches in diameter, 8 inches long, and weighing some 17 p o u n d s . T h e barrel itself is about 30 inches long, is made of specially treated steel having high yield and tensile strengths, and is closed off at t h e low pressure end by the piston and at the high pressure end by a
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