THE CHEMICAL WORLD THIS WEEK min loss. Certain enzymes like carotenases and other lipoxidases have a destructive action. One of the most stable vitamins is D. In fact, it owes its discovery to the observation that air could be blown through hot cod liver oil without destroying its antirachitic potency. Exposure to air of a thin film of vitamin D-bearing oil on the surface of certain calcium salts and dried whey results in a rapid deterioration of potency. Packaging Materials for Food. Mr. Walters, director of research and development for General Foods, grouped packaging materials used in foods in four classifications: kraft and similar papers; sulfite: glassine; and converted papers. The main attribute of kraft papers is strength. Sulfite papers are not as strong but take printing and waxing better. Glassiné's surface is ideal for waxing, and it resists penetration by oils. It is weak, however, and tears easily. Converted papers may be joined by a laminating agent and certain characteristics may be built into them such as resistance to oils, odors, and gases. In recent years, the speaker said, these products have had to face very serious competition from plastics and films. Four plastics now widely used for packaging are saran, polyethylene, Pliofilm, and vinyls. Among the films, cellophane is coated with lacquers to render it oil- and moisture-resistant, but its protective qualities are not outstanding. Advantages are its sealability and its excellent printing surface. Metals and wood were the other packaging materials discussed. Packaging Needs. Some of the packaging industry's requirements were discussed by the speaker. One is a film that will retain its desirable characteristics throughout extreme temperature ranges from deep freeze to hot box cars in the summer. It also needs waxes with the moisture resistance and hardness of paraffin, plus the heat-sealing strength of resins for frozen foods, the impermeability of foil at the price of newsprint, and a completely grease-proof coating for carton board to be used in the bakery and similar trades. Food Fads. Dr. Di Cyan discussed what he termed facts, fallacies, and fads in foods, and one is that we should not eat both carbohydrate and protein foods at the same time. That is a fallacy because mixed foods are better metabolized. He asked his listeners if they had ever tasted the "swill" that is labeled blackstrap molasses. It contains minerals which can be had, he said, from other more palatable and "less mystical" sources. It was also a fallacy to put all of one's hopes on wheat germ, even though it has a place in the daily dietary. "While it is often desirable to supplement one's diet with vitamins," he continued, "it is a fallacy to dose up with large quantities. There is no question that vitamins are essential food elements, but it. does not hold that if 3 mgs. of thiamine hydrochloride (Bt) is an adequate daily portion that 10 mgs. daily are 3 a / 3 times as good, and that 15 mgs. are five times as good." 1972
"These anomalies cannot yet be explained," chairman Conard Fernelius (left) of Peon State said. Right. A moot point is discussed by C. F. Hiskey ( center ) of Brooklyn Poly and Harry Kroll, research director at Alrose Chemical Co., the symposium sponsor C & E N REPORTS:
Symposium on t h e C h e m i s t r y o f C h e l a t e
Compounds
Potentiomefry Holds Key to Thermodynamics of Chelates pH meter gives thermodynamic d a t a on chelate compounds in water-dioxane solution BROOKLYN.-Methods similar to those of the simple acid-base titration can provide a valuable insight into the thermodynamic properties of chelate compounds C. F. Hiskey of Polytechnic Institute of Brooklyn told a symposium conducted here by his university on April 26 under the financial sponsorship of the Alrose Chemical Co. The meeting which attracted an unexpected attendance, reflected a reawakened interest in the complex compounds stimulated by the development of new industrial uses in ion-exchange, antibiotics, and other fields. Alrose is a leading producer of these compounds. Several leaders in the field said that the results presented at the meeting represent some of the first fruits of the studies of the fundamental thermodynamics of complex formation which was initiated as recently as 1945 by a paper published by Melvin Calvin of the University of California. Dr. Calvin spoke at the meeting and reviewed the work that has been completed up to this time. He also announced that his new book on coordination complexes will be ready for distribution within a "few weeks." The new interest in the basic mechanisms of complex formation, one speaker said, mark the return of the structural physical chemist to inorganic- chemistry and reestablishes the old, but now rather tenuous, association between physical and inorganic specialists. All of the speakers agreed that there are now "more questions than answers" about the thermodynamic phenomena associated with complex formation. However, several promising techniques were suggested to the audience. CHEMICAL
Use Potentiometric Data. Hiskey contended that free energies, entropy changes, and heats of reactions could be derived from potentiometric data. He said the fact that the equilibrium constants of even simple complexing reactions are governed by statistical considerations rather than electrostatic factors has delayed the application of titrometric techniques to the study of their thermodynamics. However, he said that if ionic strength of the solution is kept high relative to the concentration of the metal and the ligands, and the calculations made purely in terms of concentrations the course of complexation can be followed either by measuring the variation in metal content with ligand concentrations or by measuring the degree of complexation with ligand concentration. He said that techniques are available for making any of these determinations. With these data, according to Hiskey it is possible to determine the relative binding of ligands at different coordination sites, and establish correlations with the basicity of the ligand and the central metal ion. pH Meier Works with Mixed Solvents. Potentiometric data has not been available for some complex-formation equilibria because t h e coordination compounds are not soluble in aqueous solutions. However, those compounds which will dissolve in water-dioxane solvents containing as much as 7 5 % dioxane can be studied with a simple p H meter according to Conard Fernelius of Pennsylvania State College. He said that his group h a d found that there is a linear relationship between the e.m.f. of a cell without liquid junctions and pH meter readings and that the slope of the curve of this relationship is AND
ENGINEERING
NEWS
SU PONT CHEMICALS YOU SHOULD INVËS7I6ATI:
SOÛÏUM DISPERSIONS ® W h a t they a r e
sodium
® H o w to m a k e t h e m • H o w ίο use t h e m
Important reagent for reduction,
Polymerization, Condensation, Hydrogénation, and Dehalogenation Reactions Although sodium is a highly reactive chemical, it can he handled with ease, and its versatile reactions can be zreadily controlled. Sodium can be used in the solid o r molten forms or can be converted into a finely divided dispersion i n inert media. Sodium dispersions can be handled a s fluids ^ t ordinary temperatures and are particularly useful in reactions at temperatures below the melting point of sodium (9*7.TC) Use of highly reactive sodium dispersions reduces cycles and increases yields in organic reactions—even with less than usual agitation. TYPICAL O R G A N I C - S O D I U M Reduction . . . Esters t o alcohols . . . nitriles to a m i n e s . . . fatty esters t o keto alcohols and acyloins .. . and aromatic hydrocarbons such as napthalene t o 1,4 dihydronapthalene. Refining Hydrocarbons . . . I n e r t hydrocarbons such as napthalene c a n be refined with less t h a n 1 % ° y weight sodium. U s e of s o d i u m dispersions recluces cycle t o m i n u t e s with little or no agitation. Claisen Condensation . . . S o d i u m dispersions pro duce striking results in Claisen condensations such as t h e preparation of aceto acetic ester by selfcondensation of ethyl acetate.
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G e t all t h e facts on s o d i u m d i s p e r s i o n s From t h e p i o n e e r of t h e field! A n e w D u P o n t b o o k l e t fully d e s c r i b e s h o w s o d i u m dispersions can be readily produced i n your plant . . . and how this highly r e a c t i v e f o r m of s o d i u m c a n b e used t o i m p r o v e efficiency in s o d i u m - o r g a n i c r e a c t i o n s . U s e t h e c o u p o n b e l o w for y o u r free copy.
REACTIONS
Ρ re ρ caring Alcohol-Free Alkoxides . . . Sodium alioxicle solutions or slurries can be readily prepared by treating sodium w i t h an excess of alcohol. Halid e Condensation . . . Sodium can be used in the condensation o f alkyl or aryl halide, such as in the 3?repa_xation of decane from a m y l chloride. Polymerization Catalyst . . . S o d i u m is useful as an a c t i v e catalyst in many polymerization reactions, inducting the preparation of butadiene-type syn"èhetio rubbers* IE. I. E u P o n t D e Nemours & Co. (Inc.) JElectr-ochernicals Dept.—Wilmington 9 9 , D e l .
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IPlease send me detailed information on metallic sodium—properties, applications, advantages, m e t h o d of handling. I would like to investigate metallic sodimm for "the following applications: Π Organic Reductions • Sodium Dispersions Booklet Q Refining FiFydrocccrbons • Preparing Alcohol-Free 0 Claisen Condensation Alkoxides D Polymerization C&talyst Q Halide Condensation Name^
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1973
THE CHEMICAL WORLD THIS WEEK exactly that predicted by the Nernst equation. Because of this relationship it is possible to calibrate a p H meter to give hydrogen ion concentrations for any given mean ionic strength. By using a hydrochloric acid activity coefficient on this reading it is possible to convert it ta a thermodynamic activity figure. 1 ie reported that this technique has successfully reproduced all of the published data that it was checked against. Fernelius admitted that the procédure does not seem consistent with all accepted electrode theory but he supported it on the basis of its proved utility. l i e also found that the stability constants measured in 75
