Does chelation actually represent a new kind o f chemistry ? Are 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 hoped chemists, engineers and purchasing agents alike will find these answers helpful. Now 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 review i n c a p s u l e form: Part I i n t r o d u c e d c h e l a t i o n , o f f e r e d 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 a g e n t i s defined 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 inactive a n d h o l d s it i n s o l u t i o n . T h e a p p l i c a t i o n s in i n d u s t r y are m a n y — a n d n e w o n e s are b e i n g found almost daily. That, o f course, brings u s to another c o n s i d e r a t i o n : d i f f e r e n t c h e l a t i n g agents f o r different u s e s . VERSENE® A N D VERSENOL® Chelating agents are commercially available from D o w as 15 different products—all based on aminocarboxylic acid deriva tives. A m o n g these, wide spectrum performance i s shown by t w o series of products. T h e Versene series of products (Versene® 6 7 , Versene 100, Versene Powder, Versene Beads, Versene 9 and Versene Acid) is based o n E D T A * and the sodium salts of this material. T h e Versenol series (Versenol® 120, Versenol Powdcr a n d Versenol Beads) consists of various physical forms of Na3 H E D T A * * . T h e Versene series, except for Fe-f--|—j- in the alkaline p H range, is generally t h e stronger series of t h e t w o (more completely chelates the last traces of metal). T h e Versenol series i s notably stronger for Fe-f- + -f i n the mildly alkaline pH range and is usuaUy cheaper o n a performance basis if the con sumer can tolerate the -weaker chelate structure. Versene i s the strongest, most stable commercially available chelating agent. It is the one Λνιιΐι the greatest number o f successful applications. DESCRIPTIONS
A N D USES
H e r e are three D o w chelating agents together with descriptions and uses:
Naturally these three specific a g e n t s are not t h e ansAver t o every problem. That's the reason for the many other Versene products, to b e discussed in Part I I I . A MEASURE
OF VALUE
A measure o f the b r o a d performance capacity of a chelating agent c a n he obtained from its chelation value—determined on a reference metal. Calcium i s u s e d as t h e reference m e t a l under the standard test proceedure accepted b y the industry. D o w prefers t h i s "performance basis". I t specifies more clearly what chelating agents actually accomplish t h a n such terms as " % solids" a n d ç ç % active". Consequently, t h e " 1 0 0 " in Versene 100 m e a n s t h a t one grant of 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 the same t o k e n , one gram of Versene 67 will chelate 6 7 milligrams, and s o on. A
SUGGESTION
T w o closing thoughts: D o w w a n t s to help in a n y way possible to further develop t h e applications for chelation. Also important, D o w would like t o hear from you—your thoughts, reactions, suggestions. Please inquire about a n y problems or ideas y o u m a y have. Information or actual technical assistance will b e forthcoming promptly. Write, on your c o m p a n y letterhead, to Tecbnical Service and D e v e l o p m e n t , Dept.SC912A-l, THE DOVVT CHEMICAL COMPANY, M i d l a n d , M i c h i g a n .
their
Versene 100 is a concentrated aqueous solution of a technical grade o f t h e tetrasodium salt of E D T A . . . wTidely used in textile processing, detergent formulations a n d metal cleaning. Versene Acid is a dry form of E D T A technical. I t is used in m a n y operations as a raw material for t h e preparation of various derivatives, such as metal chelates, salts ( K , N H 4 ) . es"ters a n d m a n y others. *Ethylenediaminetetra acetic acid **Trisodiurn salt o f N-hydroxyethylethylenediaminetriacetic acid
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Versenol 120 i s a concentrated a q u e o u s solution of a technical grade of Na 3 HEDTA. It i s also very valuable t o detergent, textile a n d metal-cleaning processes.
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THE NEXT TWO TOPICS IN THIS SERIES PART III July August September
PART I V October
Specific chelating agents for specific applications (agent for iron control depends o n 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—stabilization o f hydrogen peroxide and Kier boiling in textile processing— uniform control o f trace metal catalysts in polymerization o f synthetic rubber—other industrial applications) -
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