* * *
MAY 1955
on the Cincinnati ACS Meeting SWEETER” SUGAR v
An extraordinary carbohydrate, 300 times as sweet as conventional sugar, is getting an intensive going over by chemists a t the National Institutes of Health. The compound is stevioside, obtained from a small shrub that grows wild in Paraguay. The crushed, dried leaves of this plant (known variously as the sweet herb of Paraguay, kaa he-e, and Stevia rebaudiana) have for centuries been used by the natives to sweeten their bitter mat6 tea. As an unusual botanical feature, stevioside is present in the dried leaves in the exceptionally high concentration of 7%. According to NIH’s Hewitt G. Fletcher, Jr., the recent interest in this natural product is purely scientific. Certainly, producers of conventional sweetening agents need not become alarmed a t the prospect of any sudden, severe commercial threat, Actually, stevioside is much too expensive, is far from easy to obtain, and, in view of the ready availability of other sweetening agents, has only limited appeal. For example, the growing of the Paraguayan plant is complicated by the fact that the seeds are usually sterile, and large scale reproduction would require the use of cuttings.
no nutritive value, could conceivably be used by calorieconscious weight-watchers who cannot bear the thought of eating ordinary sugar. Several years ago, two research teams a t N I H tackled the problem of determining the chemical structure of stevioside, which has the formula C38HS0018.The molecule has since been found to consist of three D-glucose segments attached to a noncarbohydrate residue called an aglucon. The structure and configuration of the carbohydrate groups are now clearly defined, as are a t least the general outlines of the remainder of the molecule. The structure of stevioside is unusual in that carbon 1 of one glucose segment is hooked onto carbon 2 of the adjacent glucose segment. This relatively rare linkage is found only in the hemicellulose of Iceland moss and a few other natural products. Stevioside’s third glucose segment is attached to the noncarbohydrate residue as an ester of a sterically hindered acid. This molecular arrangement is believed to be the first of its kind found in nature. While prospects for the future commercial use of stevioside as a sweetening agent look none too promising now, the compound may find important application for quite a different reason. Like many another complex natural product, it might serve as the starting material for the synthesis of some much-needed pharmaceutical. If a medicinal use for stevioside itself can be found, here happily would be a drug with a H.J.S. built-in sugar coating, PAPER 4 ,
DIVISION O F CARBOHYDRATE CHEMLSTRY
S U P E R F I C I A L SCIENCE (IT’S ALL ON THE SURFACE)
Unraveling the structure of a botanical curiosity
Some years ago, Paraguayan growers, attempting to stir up commercial interest in this unusual crop, placed large areas under cultivation-only to have their hopes dashed when economic uses failed to materialize. Now, the plant is cultivated almost exclusively in private gardens as a botanical curiosity. Of special scientific importance, stevioside is reportedly the sweetest natural substance known. Unlike the synthetics possessing exceptionally high sweetening power (such as saccharin and calcium cyclamate), the natural material contains carbohydrate groups, but no nitrogen. Like the synthetics mentioned, stevioside is nontoxic and, because it has little or May 19.55
mz
For the first time, a path is open to the production and control of cheaper and better synthetic lubricants for watches, clocks, and other intricate timing mechanisms. Simultaneously, paint chemists have acquired a tool for developing more precise understanding of the mechanisms of wetting, penetration and surface adhesion of paints and lacquers. Printing technologists should soon see clarification of many of their problems concerning the ability-or inability-of printing inks to wet paper and printing rolls without excessive spreading. These are but a few of the practical results expected to follow quickly the recent culmination of a 9-year fundamental research program a t the Kava1 Research Laboratory in Washington, D. C. The study has provided the first adequate explanation of the complex and often unpredictable spreading behavior of organic liquids on polished surfaces of high-melting solids such as glass, metals, quartz, or sapphire. Although the ability of liquids to climb capillary tubes or crevices is a common phenomenon, it has not been widely recognized that the capillary behavior of liquids with respect to organic solids (such as plastics, textiles, and waxes) depends on both the surface tension of the liquid’and the contact angle (or mettability) of the solid by the liquid. Wettability has been extremely difficult to measure in R repro-
INDUSTRIAL AND ENGINEERING CHEMISTRY
(Continued on page 9 A )
I A
DESIGNING ENGINEERS A N D CONSTRUCTORS FOR THE PETROLEUM A N D CHEMICAL INDUSTRIES
LUMMUS TO BUILD AIR REDUCTION CHEMICALS VINYL ACETATE PLANT AT CALVERT CITY, KENTUCKY Lum mus-Built Plant To Come O n Stream In Early 1956 T h e 30,000,000 lb. per year vinyl acetate plant which T h e Lummus Company is engineering and constructing for Air Reduction Chemical Company, a division of Air Reduction Company, Inc., is a good example of how industry can set up an integrated plant in a strategic location, and insure maximum returns for its capital investm e n t . T h e plant’s a t t r a c t i v e location a t Calvert City, Kentucky has all the benefits of readily available power, natural gas, water transportation, and a host of related chemical products. T h i s $ 3 , 0 0 0 , 0 0 0 installation scheduled for completion early in 1956, is adjacent to the calcium carbide and acetylene plant of Air Reduction’s N a t iona 1 C a r b i d e Division, and will receive pipeline acetylene from it. T h e new vinyl acetate plant will be a key develop-
ment in Air Reduction’s chemical expansion which begins with basic raw materials and ends with a variety of products having important commercial and industrial uses. Vinyl acetate goes principally into polyvinyl acetate emulsions, used in adhesives, latex paints and textile finishes, and polyvinyl alcohol used for adhesives and textile finishes. A t Calvert City, in addition to this new Air Reduction plant, L u m m u s is a l s o building a $6,000,000 high pressure acety-
lene derivatives plant for General Aniline & F i l m C o r p o r a t i o n . W h a t better example could be given to show that Lummus is ready, willing and able to design, engineer and construct your next chemical plant. T h e Lummus Company, 385 Madison Avenue, New York 17, N. Y. Engineering & Sales Offices : New York, Houston, Montreal, London, Paris, T h e Hague, Bombay. Sales Offices: Chicago, Caracas. Heat Exchanger Plant: Honesdale, Pa. Fabricated Piping Plant: East Chicago, Indiana.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47,No. 5
ducible manner, and has been nearly impossible to control or predict. Development at NRL of special surface preparation techniques-e.g! in the case of platinum, polishing the surface with 0- to 0.5-micron diamond dust in an organic vehicle, followed by flaming-coupled with use of liquids purified and handled with meticulous care, has a t long last led to the amassing of dependable, reproducible contact angle data. Stated in generalized terms, these data show that every i
Monomethylol urea (3IMU) and dimethyl01 urea (DMU) were chosen as prototypes of urea-formaldehyde resins which are monofunctional and difunctional, respectively, with respect t o the cellulose molecule. When applied to either cotton or rayon with acid catalyst, MMU produces resin chains three or four urea residues long, which are attached to the main cellulose chains a t one end. Such resin chains produce a moderate amount of crease recovery in either fabric, says Steele. DMU and other resin precondensates, with a formaldehyde urea ratio of about 2, when applied with acid catalyst react to form relatively short cross links between cellulose chains. J\Tith up t o 5 or 6y0resin content on rayon the reaction produces only slightly greater crease recovery than the reaction of an equal amount of h9MU. On cotton, however, the DMU cross-linking characteristic is very much more effective in crushproofing, even at low concentrations. The Rohm &Haas people feel this difference in the effectiveness of crosslinking resins a t low concentrations for crushproofing rayon and cotton may be due to the difference in the chemical accessibilities of these fibers. When your sxmmer trousers are crushproofed with ureaformaldehyde resins, there is apparently a two-stage reaction: a small degree of resinification occurring during the drying step, followed by a reaction with the cellulose during the subsequent cure a t a higher temperature. The function of the acid catalysts is to promote this latter reaction with cellulose rather than resinification. G. .I. P A P E R 2.
Using goniometer telescope, W. A. Zisman of Naval Research Laboratory measures contact angle of organic liquid o n platinum surface
organic liquid spreads freely on specularly smooth, clean, high-energy (high-melting) surfaces a t ordinary temperatures, unless the adsorption of the first monolayer of the liquid results in a new lowenergy surface having a critical surface tension less than the surface tension of the liquid. (Critical surface tension of a solid surface is defined as that value of the liquid surface tension above which liquids show finite cont,act angles on the given solid surface.) Fundamental cause of this behavior is the highly localized nature of the forces of adsorption between each solid and organic liquid, and between the molecules of each liquid. So great is the localization that the influence of molecules or atoms beneath the first monolayer is minor a t most; thus a monolayer of adsorbed molecules is always found sufficient to give the high-energy solid surface the same wettability properties with respect to all liquids as a low-energy solid having the same surface constitution. NRL’s work opens the door for fellow surfwe chemistry specialists to progress rapidly in research on liquid-solid wetting and adhesion-a field first explored by Thomas Young, 150 years ago. R.S.H. P A P E 9 6, D I V I S I O N O F P A I N T , PRINTING INK CHEMISTRY
PLASTICS.
AN3
FOR A B E T T E R PRESS That crease in your new summer trousers may last longer as a result of some basic research by Richard Steele and L. E. Giddings, Jr., in the Rohm & Haas laboratories. Both cotton and rayon fabrics have been examined for crease recovery after treatment by either of two types of urea resins. May 1955
DIVISION O F CELLULOSE CHEMISTRY
“M 0 LEC U LAR” PACKAGES Refrigerate, package, or add special chemicals-these are today’s tools for preserving foods and food components. Such methods are hardly efficient, however, where macro quantities must be handled to protect nutrients present in micro quantities-essential fatty acids and vitamins, for instance. I n manufacture and distribution of fortified animal feeds, protection of unstable micronutrients is especially critical; present practice is to pelletize or coat with edible waxes those feeds supplemented with unstable micronutrients. Hermann Schlenk, Hormel Institute, proposes “molecular packaging” for these and other unstable biological and medicinal products in a process derived from urea’s use in petroleum chemistry, where it is an important tool for hydrocarbon analysis and separation , I n Schlenk’s method, a complexing agent, such as urea, thiourea, deoxycholic acid, dextrin, or starch, is crystallized together with the unstable, autoxidizable material. Each molecule of the latter becomes isolated within the adduct’s crystal lattice, and it is therefore protected from any deleterious oxidation. One problem at the present research stage is finding proper host molecules, since inclusion requires an “architectural” fit between host and material to be complexed. One must also determine that the included material is nutritionally available when used to supplement feeds. Schlenk and his coworkers find essential nutrients such as linoleic and linolenic acids and vitamin A palmitate are stabilized by the method. I n addition to these and other biological and pharmaceutical products, spices and perfumes might conceivably be suitable for protecting via molecular packaging. G.H.B. PAPER 58,
DIVISION O F ORGANIC C H E M I S T R Y
INDUSTRIAL AND ENGINEERING CHEMISTRY
(Continued on page 11 A )
9A
Celite Powders provide bulking action 3 to 10 times greater than any other inert mineral filler POUND FOR POUND, Celite* diatomite powders supply more bulking action than any other inert mineral filler because their cubic volume is 3 to 10 times greater. Celite’s unique “honeycombed” structure is composed of microscopic, irregularly shaped particles that won’t pack down. I n mass they weigh only about 10 lbs. per cubic foot. That’s why Celite is so widely used to add bulk and body to industrial formulations. For example, it extends
white pigments in paints and papers . it improves dispersion of insecticides and fertilizers. it fluffs up dry powders such as household cleansers. Also, from Celite’s “honeycombed” structure comes its great absorptive capacity. T h i s characteristic is profitably utilized to keep powders ’freeflowing . . . to provide a medium for shipping or storing liquids i n dry form. And because of the physical structure of its individual particles, Celite has become the outstanding
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flatting agent f o r paints it serves as a mild, non-scratching abrasive f o r fine polishes. it improves the surface appearance of plastics. Which of the many Celite advantages can you use to build product performance or cut costs? A JohnsManville Celite Engineer will gladly discuss your problem, without obligation. For his services or more information, write Johns-Manville, Box 60, New Y o r k 16, New York. I n Canada, 1 9 9 Bay St., T o r o n t o 1, Ontario.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 5
watched today as examples of new uses for atomic radiation in organic synthesis. H.J.S.
BETA-RAY BENZENE
+
Production of benzene from unconventional raw materials has been explored as far back as anyone can remember. One of the newer approaches to benzene synthesis is to take acetylene and bombard it with beta rays. This technique, developed at General Electric, is of considerable theoretical interest, even if a t the moment it offers no glittering prospect of immediate commercialization. Back in 1925, researchers working with radon alpha particles investigated the use of radiation to convert acetylene to cuprene, (C7He),. This, in fact, was one of the first hydrocarbon radiolyses ever studied. Recent work by G E chemists, involving the use of beta particles from tritium, has also led to the preparation of cuprene, although prime attention has been focused on benzene.
P A P E R 52,
DIVISION O F PHYSICAL AND INOROANIC C H E M I S T R Y
ANTISLICK LUBRICANT
m
Oil slicks on the surface of the ocean can give away the presence of submarines, and the Navy has been looking for a long time for lubricants and hydraulic fluids that, if they do leak out, do not form slicks to make submarine officers' hair prematurely gray. The Naval Research Laboratory thinks it may have finally found one answer-the use of dibasic acid esters of fluorinated alcohols. These esters meet all the necessary requirements as far as physical properties are concernedtheir low fluidity a t low temperatures is not an obstacle in submarine lubricants and hydraulic fluids. K i t h a density of 1.4 to 1.7 grams per cc. at 20" C., compared with 1.03 for sea water, there is little danger that floating oil films will be formed. Application of this new series of synthetic lubricants in aircraft gas turbine engines and high temperature electric motors and generators is also envisioned by NRL. Their reasonsthe esters do not oxidize a t temperatures approaching 400" F. and are fairly stable to pyrolysis a t 500" F.; they are less susceptible to fire and explosion hazards (many of them have spontaneous ignition temperatures ranging from 850' to 1000" F.). Diester vapors with fluorine content of more than 55% are not explosive in pure oxygen a t 200" F. Some of the diesters are comparable to petroleum oils in lubricating ability and have little effect on rubber. Greases based on these diesters already show promise in the development of antifriction bearings operating a t high temperatures. H.W.H. PAPER 4 3 ,
DIVISION O F PETROLEUM CHEMISTRY
RADIATION STERILIZING .4cetylene transformed by tritium's radiation
I n experiments carried out a t 26' C., G E researchers found that about 7 2 molecules of acetylene are converted either to benzene or cuprene per 100 e.v. of radiation energy. As the benzene yield is about five molecules per 100 e.v., about 21y0 of the acetylene consumed goes into the formation of benzene. I n 14 test runs carried out under a wide range of conditions, the acetylene pressure was varied fivefold, while the tritium pressure (proportional to the beta-ray intensity) was varied twentyfold. The fraction of acetylene converted to benzene was independent of the acetylene pressure and the radiation intensity. From this, says Leon Dorfman of GE, it can be concluded that the reactions yielding benzene and cuprene do not involve a common intermediate and are not competitive. I n other words, this partly discredits a previous theory that acetylene' upon irradiation is converted to an activated acetylene trimer which, in turn, forms either benzene on cyclization or cuprene on polymerization. Although the latest studies confirm the idea that the benzene is formed by the cyclization of activated acetylene trimer, it is now believed that the cuprene is produced independently by cleavage of activated acetylene monomer, followed by polymerization of the dissociated product. Whatever may be the theories to explain the basic mechanisms involved, these and similar reactions are being closely May 1955
Fuel rods from nuclear reactors may find a place in future fermentation practice. Already a t the University of Michigan gamma radiation from a large cobalt-60 source has been used successfully to sterilize nutrients for a laboratory scale fermentation. Heat sterilization of nutrients and mash is the normal procedure in laboratory and industrial fermentations. Robert A. Gillies followed rates of lactic acid formation using malt sprouts or corn steep liquor as nutrients. Irradiated malt sprouts gave rates 40 to 75% higher than those obtained using heat-sterilized sprouts. Acid formation rates observed when unsterilized malt sprouts were used were similar to those obtained with the irradiated nutrient, indicating that the malt sprouts were not materially damaged by the gamma ray treatment. Corn steep liquor runs indicated some radiation damage, probably attributable to the combined effect of previous heat treatment and irradiation. Minimum dosage required has not been determined, but doses of from 2.5 to 4.5 X 106 rep rendered the nutrient solutions completely sterile. It is possible that lower doses would serve just as well. Bulk sterilization of dilute volumes of mash seems to be ruled out by the results of preliminary tests a t Michigan. I n fermentations where the entire mash was sterilized by irradiation, maximum rates of acid formation were 62 to 65y0lower than rates obtained with entirely heat-sterilized mashes. (Continued on page 13 A )
INDUSTRIAL AND ENGINEERING CHEMISTRY
11A
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*d
I
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ELECTRIC
ELECTRIC
GEAR
BRAKE
MOTOR
REDUCTION
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However, it is industrially conceivable that fuel rods discarded from nuclear reactors might be incorporated in a multipass continuous setup for sterilizing concentrated nutrient solutions before addition to the mash. G.C.I. P A P E R 20,
D I V I S I O N O F A G R I C U L T U R A L A N D FOOD C H E M I S T R Y
H O T NEEDLES x
By incorporating radioactive yttrium (YgO)into a watersoluble plastic needle, it is possible to obtain a radioactive source which can be implanted in the body for possible treatment of localized cancer, Big advantage of this type of source is the rapidity of its natural removal from the bodythe isotope’s half life is only 61 hours; the water-soluble plastics are dissolved by the body fluids and dissipated within 24 to 48 hours. T o prepare the needles, finely divided yttrium oxide, made radioactive by irradiation in an atomic reactor for 7 days, is mixed with methylcellulose. Propylene glycol is added. Polyvinyl alcohol and glycerol have also been used. The mixture is extruded through a heated die to form a flexible filament 1.5 mm. in diameter, which can be cut to the desired length. These needles have not been tried on humans yet, but they seem to have a valuable potential medical application, A.S.H. P A P E R 22,
D I V I S I O N OF B I O L O G I C A L C H E M I S T R Y
SMOKE FIGHTER Chemists have won another round in the battle against smoke. This time it’s with home heating systems, and the key to victory is dicyclopentadienyliron, called DCPI for short, the first organoiron compound containing only carbon, hydrogen, and iron to be synthesized. D u Pont workers chose this compound for fuel additive tests because of its stability, volatility, and many hydrocarbonlike characteristics-all properties essential for a good oxidation or combustion additive. ASTM L A M P
100% CATALYTICALLY CRACKED FUEL OIL
20% (boosting the heat efficiency, of course) before normal smoke levels are reached. DCPI also reduces carbon deposits on combustion chambers, fire walls, and flues. As little as 0.0fi7c by weight added t o fuel oil used in high pressure atomizing burners reduced carbon deposits 75%, a distinct aid to improved heat transfer. If the present trend toward use of higher boiling residual fuels continues, this action of DCPI may be even more important. DCPI reduces the smoking tendency of jet burners, too, and small amounts may make possible the production of jet fuels from materials now considered unsuitable. H.W.H. PAPER 5 4 ,
What does it do? Look a t the picture for a convincing demonstration of its smoke-reducing effect. Tests were made with various kinds of home oil burners. Low pressure atomizing burners fed with No. 2 fuel oil containing 0.17c DCPI produced no smoke even when operated at a fuel-air ratio 10% above normal settings. Fuel-air ratios can be advanced a full May 1955
O F PETROLEUM C H E M I S T R Y
C O N T R O L BY CRYOSCOPY Don’t count out cryoscopic methods for process control. Cryoscopy, thanks largely to the recent commercial availability of platinum resistance recorders accurate to d ~ 0 . 0 1 ~ C., has come a long way since the day when it was limited to determinations of capillary melting points and molecular weight. At least three major chemical producers are currently using such methods in their control laboratories. A couple of examples show how American Cyanamid’s C. R. Witschonke has applied well known principles to arrive a t a number of procedures suitable for routine plant analysis and control. Suppose you want to determine the purity of a compound which decomposes at its melting point. It may be possible to form a eutectic by adding another pure chemical, so that the freezing point of the mixture is lowered by 50” to 100° C. If the eutectic-forming compound is essentially pure, any lowering of the eutectic temperature that is observed is caused only by impurities present in the original sample. Dimethylanthraquinonyl, as an example, melts at 370 O C. with rapid decomposition. Its eutectic with anthraquinone, however, melts a t 270” C., where DMQ is stable. The eutectic break is as sharp as that for a pure material, and any lowering of the melting point is a measure of impurities in the original material. I n order to determine the naphthalene content of naphthalene oils, samples of oil can be added to both high-purity naphthalene and another solvent-p-nitrochlorobenzene, for example-known to be absent from the sample. The lowering of the freezing point in naphthalene indicates the total moles of impurities in the naphthalene oil; the lowering of the freezing point of the second solvent shows the total moles of impurities plus naphthalene. From these data, the weight per cent of naphthalene present in the production sample can be readily calculated. This two-solvent method has been used at American Cyanamid to control the forerun stream from a continuous naphthalene distillation column. D.M.K, P A P E R 31,
Combustion improvement by dicyclopentadienyliron
DIVISION
DIVISION OF ANALYTICAL C H E M I S T R Y
S O U N D PLASTICS BY ULTRASOUND The “why ” isn’t entirely clear yet, but the “what” has been observed experimentally. When high frequency, low energy mechanical disturbances-ultrasonic waves, in other wordsare transmitted through partially cured thermosetting resins, their velocity i s measurably reduced, and some energy loss, or wave attenuation, occurs. Both velocity and attenuation are influenced by temperature, chemical composition, and (Continued on page 14 A )
INDUSTRIAL AND ENGINEERING CHEMISTRY
13 A
NEW NIAGARA
A I R CONDITIONED TEST CABINET USES-to determine effects of controlled temperature and humidity conditions on test subjects of all kinds -to test processes- to find optimum conditions. RANGE-With water and electric power services only, the range is from freezing temperature up to 150'F (dry bulb). With refrigeration, and using Niagara No-Frost Liquid to prevent freezing of sprays, you achieve dew point temperatures as low as minus 30' F. Control of relative humidity from 5% to 95% is obtained at all temperatures in this range, Air capacity is 200, 400 or 600 c. f. m. METHOD-Air is saturated in the air-conditioning unit at the required dew point temperature and reheated to the desired dry bulb temperature. This is the method of the Niagara Type A Air Conditioner which has been proven for the most exacting duty over twenty-five years.
physical state of the resin under study, as well as by the frequency of the impressed wave disturbance. With adequate control of these independent variables, i t can be shown that both parameters also bear a quantitative relationship to degree of cure in a given resin. Pulse propagation measurements under actual molding conditions, with ultrasonic transducers incorporated into the force and cavity of a compression mold, reveal regular dependence of velocity and attenuation on cure tilme and temperature for straight phenolic, filled phenolic, and straight and filled melamine resins. Similar results are obtained, under proper temperature conditions, with a cast polyester formulation-suggesting that the ultrasonic wave alterations reflect fundamental structural modifications. In all cases the attenuation passes through a sharp maximum, and the propagation velocity increases as the polymer acquires greater rigidity. There is some evidence that for filled formulations attenuation is higher and velocity perhaps lower than for unfilled resins. The strong dependence of ultrasonic propagation parameters on the extent of cure suggests their use as criteria for extent of polymerization in thermosetting molding resins. Since measurement of these parameters can be made during tho actual curing cycle in a typical compression mold, instantaneous information regarding the progress of cure can be made easily available. It works, although theoretical interpretation of the observed effects remains obscure. R.N.H. PAPER 23, D I V I S I O N O F PAINT, PRINTINQ INK CHEMISTRY
TEST CABINET--(inside)
dimensions are 30"x 28"x 24" with access clear opening 26" x 22". Insulation is the equivalent of 4" cork.
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I O N E X C H A N G E FOR GASES Ion exchange resins, long used with liquids, have now been found useful for gaseous phase reactions. The Gasionic process developed by A. C. Reents and W. S. Morrison, Illinois Water Treatment Co., uses commercially available ionexchange resins to remove impurities from air or hydrocarbon streams. Here are some results: Gas
CONTROL-
The dew point thermostat is located in the air stream, the dry bulb thermostat in the test cabinet. No moisture sensitive instruments are needed. Recorders may be used to obtain a complete record of conditions.
PLASTICS,
Resin
HzS, 1% in air SO,, 1 % in air SO?, 1% in air C-02, 0.5% in air
hHx, 2% in air HzS, 0.2%,in natural gas C o t , 10% in ethylene
Anion exchanger Anion exchanger Anion exchanger Anion exchanger Cation exchanger Anion exchanger Anion exchanger
Breakthrough C a acity Lb./%u. Fk.
1 . 7 HzS 3 . 2 SO2 3 , Q SOz 1 04 COz 4,67
"3
1 . 7 HzS 2 I O 1 coz
Dry or wet beds of resin may be used. The process should be economically competitive with conventional purification methods for many applications. Cost of regeneration chemiA.S.H. cals is the chief operating expense. PAPER 82.
DIVISION
O F I N D U S T R I A L AND E N G I N E E R I N G C H E M I S T R Y
MOLY M I S S I N G L I N K S Molybdenum chemistry is beset by complexities. The buretand-balance methods of such renowned analysts as Scheele, Lavoisier, and Berzelius failed to resolve many chemical problems of molybdenum compounds. Even modern techniques have not provided sought-for answers to many uncertainties, or, indeed, permitted a definite statement that (Continued on page 16 A )
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 5
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some problems can be solved, although the contradictions in the record are at least now apparent. Molybdenum can form compounds in oxidation states of 0, 2, 3, 4, 5, and 6, and having coordination numbers of 4, 6, and 8. Coordination numbers can change easily with changing conditions. A basic problem lies in this variable valence of molybdenum, says consultant D . H. Killeffer. Look, for instance, a t molybdenum’s compounds with oxygen. Only two oxides, M o 0 and ~ Moos, are definitely proved to exist, although the existence of corresponding compounds with other elemerts strongly suggests that there must be binary oxides of the di-, tri-, and pentavalent metal. Yet the most refined of present procedures fails to confirm fully the occurrence of these other oxides. The oxides missing from the binary series apparently are found, if a t all, as hydrated compounds or in ternary compounds where another element is substituted for part of the oxygen. Divalent molybdenum occurs, if a t all, only in ternary compounds that do not yield simple hydroxide compounds, but rather remain complex until they undergo disproportionation when heated to a temperature high enough to decompose them. Other series of molybdenum compounds, Killeffer points out, show similar confusion gaps where certain valences of the metal appear to be lacking without explanation. Here, it would seem, is fertile ground for further exploration. D.M.K. P A P E R 53,
D I V I S I O N OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
HELP FOR D T ANALYSIS
ms
Differential thermal analysis is an increasingly useful tool for detecting phase changes in materials a t varying temperatures. Such studies provide an insight into thermochemical effects, ENG. as well as a clue to an unknown material’s identity [IND. CHEM.,46,17 A (August 1954)l. But DTA has its drawbacks. Sometimes a phase transformation may have only a small heat effect. Or the heat generated by one transformation may interfere with measurement of that from another at a slightly different temperature. Also, DTA procedures may not be readily suitable for work below room temperature. What to do? Paul D. Garn and S. S. Flaschen of the Bell Telephone Labs suggest continuous electrical resistance measurements to supplement DTA in such circumstances. Using a resistance bridge circuit (one arm of which is the sample being studied), a d.c. microvolt amplifier, and a strip chart recorder, and working with pressed powder or sintered samples they are able to detect sharp dips and discontinuities in resistance curves a t phase changes in many substances, including barium titanate and silver iodide. Other processessintering and calcining, for example-might benefit also from the analytical information supplied by electrical resistance data, D.M.K.
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I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 47, No. 5
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