D o e s chelation actually represent a n e w kind of chemistry ? A r e the possibilities as exciting as many s e e m to think ? T h i s series endeavors t o answer these—and many other—pertinent questions o n this fascinating subject. It is h o p e d chemists, engineers a n d purchasing agents alike, will find these answers helpful. N o w on to . . .
T h e Chemistry of Chelation: Part II Versene and Versenol Series · Descriptions and Uses A measure of Value · A Suggestion T o r e v i e w i n c a p s u l e form: P a r t I i n t r o d u c e d c h e l a t i o n , offered e x a m p l e s o f typical c h e m i c a l r e a c t i o n s , a p p l i c a t i o n s , a n d d i s c u s s e d f u t u r e p o s s i b i l i t i e s . Y o u w i l l r e m e m b e r that a chelating agent is d e n n e d as a chemical which surrounds m e t a l l i c i o n s w i t h a m u l t i p l e - r i n g s t r u c t u r e that k e e p s t h e m e t a l c h e m i c a l l y i n a c t i v e a n d h o l d s it i n s o l u t i o n . T h e applications in industry are many—and n e w ones a r e being f o u n d a l m o s t d a i l y . T h a t , of c o u r s e , b r i n g s u s t o a n o t h e r c o n s i d e r a t i o n : different c h e l a t i n g agents f o r d i f f e r e n t u s e s . VERSENE® A N D
VERSENOL®
Chelating agents are commercially available from E)ow a s 15 different products—all based o n aminocarboxylic acid derivatives. A m o n g these, wide spectrum performance is s h o w n by t w o series of products. T h e Versene series of products ( V e r s e n e ® 67, Versene 100, Versene Powder, Versene Beads, Vsrsene 9 and Versene Acid) is based on E D T A * a n d the s o d i u m s a l t s of this material. T h e Versenol series (Versenol® 120, Versenol Powder a n d Versenol Beads) consists of various physical forms of Nae H E D T A * * . T h e Versene series, except for F e + - f - - l · in the alkaline p H range, is generally the stronger series o f the t w o (more completely chelates t h e last traces of m e t a l ) . T h e Versenol series is notably stronger for F e + - f - + in the mildly alkaline p H range and is usually cheaper on a performance basis i f the consumer can tolerate the weaker chelate structure. Versene i s the strongest, most stable commercially available chelating agent. I t is t h e one with the greatest number of successful applications. DESCRIPTIONS
A N D USES
Versenol 120 is a concentrated aqueous solution o f a technical grade of Na 3 H E D T A . I t is also very valuable t o detergent, textile and metal-cleaning processes. Naturally these three specific agents are not t h e answer to every problem. That's t h e reason for the m a n y other Versene products, to be discussed in Part I I I . A MEASURE OF
VALUE
A measure of t h e hroad performance capacity of a chelating agent can be obtained from i t s chelation value—determined on a reference metal. Calcium is used as t h e reference metal under the standard t e s t proceedure accepted by t h e industry. D o w prefers this "performance basis". I t specifies more clearly what chelating agents actually accomplish than such terms as "% solids" and " % active". Consequently, t h e " 1 0 0 " in Versene 100 means that one gram o f t h i s product will chelate 100 milligrams of calcium carbonate i n accordance w i t h the standard test procedure. B y t h e same t o k e n , one gram o f Versene 67 will chelate 67 milligrams, and so on. A
SUGGESTION
T w o closing thoughts: D o w w a n t s to help in any w a y possible t o further develop t h e applications for chelation. Also important, D o w would like to bear from you—your thoughts, reactions, suggestions. Please inquire about a n y problems or ideas y o u may have. Information or actual technical assistance will b e forthcoming promptly. Write, on your c o m p a n y letterhead, to Technical Service and D e v e l o p m e n t , D e p t . SC913A-3. T H E DOW CHEMICAL COMPANY, Midland, Michigan.
Here are three D o w chelating agents together w i t h descriptions and uses:
their
THE NEXT TWO TOPICS IN THIS SERIES
Versene 100 is a concentrated aqueous solution of a technical grade of t h e tetrasodium salt of E D T A . . . w i d e l y used i n textile processing, detergent formulations a n d m e t a l cleaning. Versene Acid is a dry form of E D T A technical. It is used i n m a n y operations as a raw material for t h e preparation o f various derivatives, such a s metal chelates, salts ( K , N E L ) , esters a n d m a n y others.
PART III July August September
*Ethylenediaminetetra acetic acid **Trisodium salt of N-hydroxyethylethyleoediaminetriacetic acid
YOU
CAN
P A R T IV October
Specific chelating agents for specific applications (agent for iron control depends on pH—Versene Fe-3 Specific® for iron and transition metals on the alkaline side, Versene T ® for iron in presence of free caustic—other solutions to special problems). Applications in specific industries (formulation of alkaline cleansers—stahilization of hydrogen peroxide and Kier boiling in textile processing— uniform control of trace metal catalysts in polymerization of synthetic rubber—other industrial applications).
DEPEND
Dow
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