Factors Influencing the Chain Lengths of Inorganic Polyphosphates

Chapter 7 F a c t o r s I n f l u e n c i n g the C h a i n L e n g t h s of I n o r g a n i c Polyphosphates Edward J. Griffith

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The theory of formation of inorganic condensed phosphates i s well established and has had many years of tests.(1) It has been demonstrated in both amorphous and crystalline systems that the M O-P O ratio of a system i s a dominant controlling factor, where M is one equivalent of cationic functions which may contain one or more metal functions. For any single molecule -ion the ratio precisely dictates the chain length. As the chain lengths of polyphosphates increase other factors play a greater and greater role but the M O-P O ratio continues to dominate as a necessary but not sufficient condition to effectively control chain lengths. These other conditions include factors as the specific metals ions contained in the metal oxides, the phase state of the phosphate (crystalline or amorphous), the composition of the system containing the polyphosphate, seed crystals, and the thermal history of the system. 2

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Alkali metal and alkaline earth polyphosphates crystallize as short chains, two to six phosphate groups per chain or very long chains with hundreds to thousands of P0 " per chain. A l l polyphosphates in the a l k a l i metal and alkaline earth systems are amorphous in the intermediate chain lengths. Control of the short chain length polyphosphates, both crystalline or amorphous, i s a function of R, the M 0-P 0 ratio. The control of the chain lengths of very long crystalline polyphosphates as Maddrell's salt, Kurro^s salt, and calcium phosphate fibers i s not well understood. 3

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0097-6156/92/0486-0086$06.00/0 © 1992 American Chemical Society Walsh et al.; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1992.

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T h i s work was d i r e c t e d t o w a r d t h r e e p r i m a r y g o a l s : 1. To g a i n a b e t t e r u n d e r s t a n d i n g o f t h e variables c o n t r o l l i n g the chain lengths of very long c r y s t a l l i n e polyphosphate molecule-ions. 2. D e t e r m i n e w h e t h e r o r n o t " c r o s s - l i n k e d " potassium K u r r o ^ s s a l t contains cross-links i n the c r y s t a l l i n e p h a s e and i s i n d e e d a c r y s t a l l i n e u l t r a p h o s p h a t e o r d o e s t h e s a l t o b e y t h e p h a s e d i a g r a m f o r t h e two component, K 0-P 0 system. 3. G a i n more u n d e r s t a n d i n g o f t h e f u n c t i o n o f seed crystals as templets i n the growth of long chain polyphosphates and the type of phosphate segment d e l i v e r i n g t h e P0 " f r o m t h e m e l t p h a s e t o t h e c r y s t a l surface during c r y s t a l l i z a t i o n . 2

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P o l y p h o s p h a t e i s d e f i n e d i n t h i s work a s any linear, condensed phosphate, i n which t h e phosphate, but not n e c e s s a r i l y t h e system c o n t a i n i n g t h e phosphate e x h i b i t s t h e c o n d i t i o n s 1 < M 0/P 0 < 2, where M i s any s i n g l e o r mixed metals w i t h a t o t a l e q u i v a l e n c y o f u n i t y . The definition i s required to differentiate the total composition of a system from the polyphosphates c r y s t a l l i z i n g i n a melt. An example i s a p o l y p h o s p h a t e c r y s t a l l i z i n g from a m e l t o f u l t r a p h o s p h a t e c o m p o s i t i o n where s e v e r a l m e t a l o x i d e s may be i n v o l v e d . 2

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One of the long accepted concepts of polyphosphate c h e m i s t r y i s d e r i v e d f r o m t h e e q u a t i o n (2)

where R = M 0/P 0 , t h e m o l a r r a t i o , and η = a v e r a g e number o f p h o s p h o r u s atoms p e r m o l e c u l e ; t h e number average c h a i n length o f the polyphosphate. The e q u a t i o n i s e x a c t f o r a s i n g l e m o l e c u l e o r f o r an assemblage o f m o l e c u l e s a l l o f w h i c h h a v e t h e same s t r u c t u r e and c o m p o s i t i o n . I t p r e d i c t s w e l l f o r s y s t e m s b o t h amorphous a n d c r y s t a l l i n e when t h e c h a i n l e n g t h o r a v e r a g e c h a i n l e n g t h o f t h e system o f molecules i s r e l a t i v e l y s m a l l , f i f t y or less. When amorphous s y s t e m s become c o m p l e x w i t h many s m a l l m o l e f r a c t i o n s o f m o l e c u l e s w i t h e x a c t l y t h e same c h a i n l e n g t h summing t o an a s s e m b l a g e o f many c h a i n l e n g t h s t h e e x a c t n e s s o f t h e e q u a t i o n c a n become c o m p r o m i s e d . ( 3 , 4, 5) O t h e r p r o b l e m s a r i s e when t h e c h a i n l e n g t h s o f t h e p o l y p h o s p h a t e become v e r y l o n g . The v a l u e o f R i s not v e r y s e n s i t i v e t o a change i n c h a i n l e n g t h f r o m 1000 t o 1001, f o r example, a s t h e v a l u e o f R approaches u n i t y as a l i m i t f o r t h e i n d i v i d u a l m o l e c u l e s . V e r y l o n g c h a i n p o l y p h o s p h a t e s (R = u n i t y ) c a n f o r m and 2

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Walsh et al.; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1992.

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crystalize i n a s y s t e m s where t h e s y s t e m ' s R i s a f r a c t i o n a l number, a s i n u l t r a p h o s p h a t e m e l t s . Factors influencing the formation of very long chain length polyphosphates are addressed. Experimental A l a r g e number o f s a m p l e s o f [ C a ( P 0 ) ] were made i n b a t c h e s f r o m a few grams t o f i f t y p o u n d s o r more. I n a l l c a s e s t h e s a m p l e s were h e a t e d t o 1000 °C a n d a l l o w e d t o s l o w l y c r y s t a l l i z e from a sodium u l t r a p h o s p h a t e melt. Under t h e b e s t c o n d i t i o n s f i b e r s o f t h r e e i n c h e s i n length were prepared from the large melts where c r y s t a l l i z a t i o n c o u l d be c o n t r o l l e d . (6) Downloaded by FUDAN UNIV on March 20, 2017 | http://pubs.acs.org Publication Date: April 7, 1992 | doi: 10.1021/bk-1992-0486.ch007

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P o t a s s i u m K u r r o l ' s s a l t s were p r e p a r e d s i m i l a r t o t h o s e p r e p a r e d b y P f a n s t e i l a n d l i e r (7) who f i r s t r e p o r t e d t h e very i n t e r e s t i n g solution behavior of Kurrol's s a l t s p r e p a r e d from u l t r a p h o s p h a t e m e l t s . I f cross-linking i s r e s p o n s i b l e f o r t h e b e h a v i o r o f t h e s e p h o s p h a t e s when d i s s o l v e d i n water, f o r a K 0-P 0 molar r a t i o e q u a l t o 0.98, two p e r c e n t o f t h e p h o s p h a t e g r o u p s s h o u l d b e involved i n cross-linking. Two o f e v e r y 100 p h o s p h a t e g r o u p s s h o u l d n o t h a v e a m a t c h i n g K* i o n a n d must be attached to another phosphate group to maintain neutrality. In a c r y s t a l i f t h e phosphate c h a i n lengths a r e 10,000 b e f o r e c r o s s - l i n k i n g t h e n t h r e e d i m e n s i o n a l c r o s s - l i n k i n g would r e s u l t i n gigantic molecule-ions l o c k e d i n t o a complex c r y s t a l l a t t i c e . 2

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C l e a r m e l t s w i t h t h e f o l l o w i n g c o m p o s i t i o n s w e r e made b y thoroughly mixing best grades of monopotassium orthophosphate, 85% phosphoric acid, or potassium c a r b o n a t e and h e a t i n g t h e m i x t u r e s t o 8 5 0 C f o r t h i r t y minutes. Lower t e m p e r a t u r e s c a n b e u s e d f o r t h e m i x t u r e s on e i t h e r s i d e o f t h e m e t a p h o s p h a t e c o m p o s i t i o n . e

K 0\P 0 0.50 2

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= 1.02, 1.00, 0.98, 0.94, 0.85, 0.75, 0.65, a n d

X - r a y powder p a t t e r n s were v e r y c a r e f u l l y d e t e r m i n e d o f the compositions 1.02, 1.00, 0.94, 0.75, a n d 0.65. The x - r a y p a t t e r n s were i d e n t i c a l f o r r a t i o s 1.02 through 0.94 e x c e p t f o r m i n o r v a r i a t i o n s i n i n t e n s i t i e s t h a t were probably a r e s u l t of orientation o f the very fibrous c r y s t a l s . A n amorphous p h a s e was f o u n d m i x e d w i t h n o r m a l K u r r o l ' s s a l t p a t t e r n i n t h e 0.75 a n d 0.65 s a m p l e s w h i l e a sample w i t h a K 0-P 0 r a t i o o f 0.50 c o u l d n o t be crystallized. 2

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a n a l y s e s were d e t e r m i n e d

on samples


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w i t h K 0 - P 0 r a t i o s r a n g i n g f r o m 1.00 t o 0.65. T h e K P 0 K P O phase diagram (8) was extended into the u l t r a p h o s p h a t e r e g i o n a n d i s p r e s e n t e d i n F i g u r e 1. T h e e x t e n s i o n i s n o t h i g h l y p r e c i s e n o r i s t h e e x t e n s i o n an e q u i l i b r i u m phase system. The e u t e c t i c b e h a v i o r between p o t a s s i u m K u r r o l ' s s a l t a n d a p o t a s s i u m p h o s p h a t e was seen i n a l l thermal analyses and had a melting temperature o f 450 C. The phosphate mixed w i t h t h e K u r r o l ' s s a l t i s a n u l t r a p h o s p h a t e g l a s s t h a t may b e p a r t i a l l y c r y s t a l l i n e . The u l t r a p h o s p h a t e a b s o r b e d w a t e r from a zeolite dried nitrogen gas purge during thermogravmatric a n a l y s e s a s shown b y a n i n c r e a s e i n w e i g h t o f t h e samples a t t e m p e r a t u r e s between 1 0 0 C and 300 C. 2

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The f o l l o w i n g e x p e r i m e n t was p e r f o r m e d t o d e t e r m i n e i f i t is possible t o mimic the properties o b t a i n e d when p o t a s s i u m K u r r o l ' s s a l t w i t h a 0.98 K 0 - P 0 ratio i s p r e p a r e d from a m e l t i n a f u r n a c e . The approach i s t o mix t h e p o t a s s i u m u l t r a p h o s p h a t e w i t h a r a t i o o f 0.65 w i t h p o t a s s i u m K u r r o l ' s s a l t made w i t h a r a t i o K 0 - P 0 = 1.0. 2

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M i x 0.5g o f t h e 0.65 r a t i o u l t r a p h o s p h a t e w i t h 9.5g o f 1.0 K 0 - P 0 r a t i o potassium K u r r o l ' s s a l t and d i s s o l v e t h e s a l t s i n 1 l i t e r o f w a t e r c o n t a i n i n g 5.0 grams o f sodium pyrophosphate as a s o l u b i l i z i n g agent. Compare t h i s t o a s o l u t i o n made w i t h 10g o f 1.0 K 0 - P 0 ratio p o t a s s i u m K u r r o l ' s w i t h o u t added u l t r a p h o s p h a t e . The m i x t u r e s do n o t b e h a v e a s t h e p o t a s s i u m p o l y p h o s p h a t e s grown i n a n u l t r a p h o s p h a t e m e l t a n d a r e no more v i s c o u s t h a n K u r r o l ' s s a l t w i t h o u t t h e added u l t r a p h o s p h a t e . 2

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V i s u a l o b s e r v a t i o n s o f t h e c r y s t a l l i z a t i o n p r o d u c t s made f r o m m e l t s p r e p a r e d i n t h e M 0-P 0 r a n g e f r o m 0.5 t o 0.75 showed v e r y d e f i n i t e i n d i c a t i o n s o f a two p h a s e s y s t e m . The m e l t w i t h a n M 0-P 0 r a t i o o f 0.50 c o u l d n o t b e c r y s t a l l i z e d a t any temperature attempted a s low a s 4 0 0 C and was a c l e a r t r a n s p a r e n t g l a s s . T h e m e l t w i t h a M 0P 0 r a t i o o f 0.65 c o u l d b e c r y s t a l l i z e d t o f i n e c r y s t a l s contained i n milky white s o l i d . T h e m e l t w i t h a n M 0P 0 r a t i o o f 0.75 c r y s t a l l i z e d t o a p l a t e - l i k e crystal t h a t appeared t o be c r y s t a l l i n e throughout, behaved a s an a m o r p h o u s - c r y s t a l m i x i n DTAs. In a l l respects the potassium Kurrol's salt i s similar t o the calcium polyphosphate f i b e r s , [ C a ( P 0 ) ] , grown u n d e r similar conditions. 2

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Short Chain K u r r o l ' s S a l t s A t t e m p t s were made t o grow s h o r t c h a i n l e n g t h K u r r o l ' s s a l t f r o m m e l t s w i t h M 0-P 0 r a t i o s b e t w e e n 1.04 (n = 50) 2

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F i g u r e 1. 8

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An extension of the K 0-P 0 phase diagram i n t o the ultraphosphate r e g i o n . The s e c t i o n l a b e l e d K - U l t r a i s amorphous t o x-ray and i s ultraphosphate g l a s s .


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» O ^ η g§ S

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and 1.10 ( n = 2 0 ) . I f a s l i g h t e x c e s s o f Na 0 o r K 0 behaved on the basic side of the metaphosphate c o m p o s i t i o n as P 0 i s r e p o r t e d t o behave on t h e a c i d s i d e o f t h e metaphosphate c o m p o s i t i o n i t s h o u l d be p o s s i b l e t o grow s h o r t c h a i n K u r r o l ' s s a l t s a s w e l l a s c r o s s - l i n k e d K u r r o l ' s s a l t s . In a l l cases the r e q u i r e d q u a n t i t i e s o f Na P O and K ^ O ^ c r y s t a l l i z e d i n t h e m e l t s as r e q u i r e d b y t h e p h a s e d i a g r a m w h i l e t h e K u r r o l ' s s a l t was v e r y s i m i l a r t o t h e s a l t o b t a i n e d f r o m m e l t s w i t h M 0-P 0 = 1.0. 2

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D i s c u s s i o n and R e s u l t s : I n t h e p r e p a r a t i o n o f v e r y l o n g c r y s t a l s (3 i n c h e s χ 10 μ) o f c a l c i u m p o l y p h o s p h a t e f i b e r s , t h e f i b e r s a r e grown i n sodium u l t r a p h o s p h a t e m e l t s . Both t h e c r y s t a l l i n e K u r r o l ' s s a l t and u l t r a p h o s p h a t e phases a r e d e t e c t a b l e i n t h e c o o l e d f i b e r c a k e . The u l t r a p h o s p h a t e p h a s e i s w a t e r s o l u b l e a n d c a n be q u i c k l y l e a c h e d f r o m t h e c r y s t a l l i n e phase t o produce f r e e f i b e r s . (9) The p o l y p h o s p h a t e c h a i n s grown i n t h e c a l c i u m p o l y p h o s p h a t e c r y s t a l s a r e o f u l t r a l o n g l e n g t h a n d showed no s i g n s o f c r o s s - l i n k i n g i n the crystalline phase when single crystal x-ray s t r u c t u r e s were d e t e r m i n e d . C r o s s - l i n k e d potassium K u r r o l ' s i s prepared i n e x a c t l y t h e same manner a s t h e c a l c i u m p o l y p h o s p h a t e f i b e r s . The only d i f f e r e n c e i s potassium i s s u b s t i t u t e d f o r calcium i n the p r e p a r a t i o n o f potassium K u r r o l ' s s a l t . There i s s t r o n g reason t o q u e s t i o n whether o r n o t t h e s t r a n g e s o l u t i o n behavior o f c r o s s - l i n k e d potassium K u r r o l ' s s a l t i s a r e s u l t o f c r o s s - l i n k i n g i n t h e c r y s t a l l i n e phase o r i s a r e s u l t o f u l t r a l o n g polyphosphate c h a i n s mixed w i t h an i n d e p e n d e n t u l t r a p h o s p h a t e p h a s e t h a t c o n t a i n s t h e required cross-linking. A l l o f t h e o b s e r v a t i o n s which led to the b e l i e f that the molecule-ions i n the c r y s t a l l i n e p h a s e were c r o s s - l i n k e d c a n b e e x p l a i n e d b a s e d u p o n t h e two p h a s e m o d e l where t h e u l t r a p h o s p h a t e phase i s r a t h e r q u i c k l y degraded i n aqueous s o l u t i o n s t o form a c i d i c groups. A t t e n t i o n i s d i r e c t e d toward t h e polyphosphate anions as t h e s t r u c t u r a l element under c o n s i d e r a t i o n . The c a t i o n i c f u n c t i o n s a r e considered only as they influence the behavior of the anions. Phase chemistry and thermodynamics become important considerations in d e v i s i n g schemes t o c o n t r o l t h e grow o f l o n g e r a n d l o n g e r polyphosphate chains. The c a t i o n i c components o f t h e p h a s e s y s t e m s c a n n o t be i g n o r e d , but they will be relegated to a causal role.


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N o t o n l y t h e c o m p o s i t i o n and t h e r m o d y n a m i c s c a n i n f l u e n c e the growth o f polyphosphate c h a i n s , but the thermal h i s t o r y o f the phosphate can o f t e n l e a d t o m e t a s t a b l e e q u i l i b r i a with polyphosphates t h a t are not found i n phase diagrams f o r the systems. Slow crystallization rates usually favor the formation of longer chain polyphosphates i f the crystallizing salt is the thermodynamically stable crystal under the growth conditions. During crystallization impurities (chain growth terminators) are d r i v e n t o the surface of a c r y s t a l i f n e i t h e r s o l i d s o l u t i o n s nor double s a l t s are formed between t h e i m p u r i t i e s and the crystallizing polyphosphate. The s l o w e r g r o w t h r a t e s p r o v i d e longer times f o r i m p u r i t i e s to migrate to the c r y s t a l surface. I n s y s t e m s where t h e c r y s t a l l i z i n g salt i s not the t h e r m o d y n a m i c a l l y s t a b l e s a l t t h e s y s t e m c a n be c o o l e d too slowly to o b t a i n maximum c h a i n lengths of the c r y s t a l l i z i n g polyphosphate. Sodium K u r r o l ' s s a l t i s u n s t a b l e w i t h r e s p e c t t o sodium c y c l i c t r i p h o s p h a t e under all conditions at atmospheric pressure. If a c r y s t a l l i z i n g melt i s cooled too slowly i t converts to sodium c y c l i c t r i p h o s p h a t e . P r o p e r s e e d i n g and r a t e s o f c r y s t a l l i z a t i o n are important i n o b t a i n i n g high y i e l d s of s o d i u m K u r r o l ' s s a l t where t h e c h a i n l e n g t h may be 5,000 t o 10,000, o r more. (10) M e t a l o x i d e s (and w a t e r ) a r e c h a i n g r o w t h t e r m i n a t o r s o f l o n g c h a i n p o l y p h o s p h a t e s a s p r e d i c t e d by E q u a t i o n 1. The l o n g c h a i n p o l y p h o s p h a t e c h a i n s a r e v e r y s e n s i t i v e t o chain breakers. The d i f f e r e n c e b e t w e e n a p o l y p h o s p h a t e a n i o n o f c h a i n l e n g t h 1000 and one o f c h a i n l e n g t h 2000 i s o n l y one M 0 g r o u p p e r two t h o u s a n d P0 groups. 2

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Long c h a i n p o l y p h o s p h a t e s c r y s t a l l i z e from m e l t s t o form s t r a i g h t molecule-ions aligned p a r a l l e l to the longest a x i s o f the c r y s t a l (Maddrell's s a l t ) o r as l o n g h e l i c a l chains (Kurrol's s a l t ) , aligned p a r a l l e l to the longest a x i s of the c r y s t a l . In n e i t h e r case are the molecules t w i s t e d nor f o l d e d i n the c r y s t a l . This i s important when c o n s i d e r i n g how l o n g c h a i n m o l e c u l e - i o n s grow f r o m melts. (12) A t t e m p t s t o o b t a i n amorphous p o l y p h o s p h a t e s w i t h a v e r a g e c h a i n l e n g t h s o f 1000 d i r e c t l y b y q u e n c h i n g m e l t s h a v e n o t b e e n s u c c e s s f u l . A v e r a g e c h a i n l e n g t h s o f amorphous p o l y p h o s p h a t e s o f n e a r 400 h a v e b e e n t h e maximum o b t a i n e d d i r e c t l y from m e l t s . Sodium K u r r o l ' s s a l t o f a v e r a g e c h a i n l e n g t h s o f s e v e r a l thousand have been m e l t e d t o make q u e n c h e d g l a s s . The c h a i n l e n g t h s a r e no longer than obtained by m e l t i n g h i g h p u r i t y s o d i u m (cyclic


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triphosphate) trimetaphosphate. I n d i r e c t methods o f o b t a i n i n g amorphous v e r y l o n g c h a i n l e n g t h g l a s s e s h a v e b e e n d e v i s e d . (12) I f t h e c a l c i u m p h o s p h a t e f i b e r s grown f r o m u l t r a p h o s p h a t e m e l t s a r e s l u r r i e d w i t h a s o l u t i o n o f sodium e t h y l e n e diamine tartaric acid the calcium crystals can be c o n v e r t e d t o a sodium phosphate g l a s s t h a t d i s s o l v e s v e r y slowly y i e l d i n g very long chains. In the d i s c u s s i o n to follow, the great differences b e t w e e n s o d i u m and p o t a s s i u m c o n d e n s e d p h o s p h a t e phase systems i s h i g h l i g h t e d . Where t h e s o d i u m K u r r o l ' s s a l t is metastable with respect to the cyclic sodium t r i m e t a p h o s p h a t e t h e r e i s no c y c l i c m e t a p h o s p h a t e i n t h e p o t a s s i u m p h o s p h a t e two component p h a s e s y s t e m and t h e K u r r o l ' s s a l t i s t h e o n l y s t a b l e compound i n t h e p h a s e system w i t h K 0-P 0 r a t i o s near u n i t y . 2

2

5

The s o d i u m p o l y p h o s p h a t e s y s t e m s p r o d u c e g l a s s e s v e r y e a s i l y w h i l e i t i s d i f f i c u l t t o make p o t a s s i u m g l a s s e s . The milky glassy masses o f p o t a s s i u m metaphosphate c o m p o s i t i o n s o b t a i n e d by q u e n c h i n g t h e p o t a s s i u m m e l t s a r e r i c h i n potassium trimetaphosphate, though t h e phase d i a g r a m f o r t h e s y s t e m c o n t a i n s none. Potassium c y c l i c triphosphate can be made t h e r m a l l y by dehydrating monopotassium orthophosphate w i t h u r e a a t temperatures l e s s than 300 C, e

Ο 3 KH P0 2

4

+ 3 NH CNH 2

2

=>

K (P0 ) 3

3

3

+

6 NH

3

+ 3

C0

2

o r i n a q u e o u s s o l u t i o n by an i o n e x c h a n g e o f s o d i u m f o r potassium i n the c y c l i c t r i p h o s p h a t e system.

Seed C r y s t a l s As

Templets

I f p o l y p h o s p h a t e s o f c h a i n l e n g t h s g r e a t e r t h a n a b o u t 350 a r e t o be o b t a i n e d a c r y s t a l l i z a t i o n p r o c e s s i s r e q u i r e d i n which a seed c r y s t a l i s behaving as a templet f o r c h a i n growth. The t e m p l e t a i d s t h e c r y s t a l l i z a t i o n t o proceed without the chains of molten polyphosphate " s e q u e s t e r i n g " metal i o n s t o t e r m i n a t e t h e i r growth o r thermal a c t i v i t y rupturing the molecules. To o b t a i n h i g h t e n s i l e s t r e n g t h s o f c a l c i u m p o l y p h o s p h a t e f i b e r s c r y s t a l s i t i s n e c e s s a r y t o grow p o l y p h o s p h a t e m o l e c u l e - i o n s as l o n g as p o s s i b l e . When a phosphate g r o u p f r o m a h i g h t e m p e r a t u r e m e l t s y s t e m moves t o a h i g h



94


temperature crystal lattice the phosphate group has t r a n s g r e s s e d a phase boundary. The m e l t s y s t e m i s a r e g i o n where r e o r g a n i z a t i o n i s c h a o t i c . In the c r y s t a l lattice the environment i s highly organized. The p h o s p h a t e g r o u p o r g r o u p s must n o t o n l y f a l l t o a l a t t i c e o f l o w e r c h e m i c a l p o t e n t i a l , b u t must a l s o b e a c c o m p a n i e d b y t h e c o r r e c t number o f c a t i o n i c g r o u p s t o e x a c t l y b a l a n c e t h e n e g a t i v e c h a r g e on t h e p h o s p h a t e . T h i s must b e d o n e w i t h o u t t h e p o l y p h o s p h a t e s e q u e s t e r i n g enough metal o x i d e t o a c t as e i t h e r chain terminators or breakers.

L o n g e r c h a i n s o f p o l y p h o s p h a t e s (n > 5,000) grow t o e v e n g r e a t e r l e n g t h s i n systems d e f i c i e n t i n m e t a l o x i d e s o r c o n t a i n i n g an e x c e s s o f P 0 . Under t h e s e c o n d i t i o n s t h e m e t a l o x i d e s w i l l be a t t r a c t e d t o t h e more a c i d i c m e l t p h a s e and t h e m e l t p h a s e w i l l e x e r c i s e a n e l e m e n t o f c o n t r o l over the c r y s t a l l i z i n g polyphosphate. It is expected t h a t longer chain polyphosphate molecules should grow i n c r y s t a l s where t h e m e l t s h a v e t h e r a t i o , M 0/P 0 < 1, b u t n o t s o low a s t o move i n t o a r e g i o n o f t h e p h a s e d i a g r a m d o m i n a t e d b y o t h e r compounds. 2

5

2

2

5

C o n d e n s e d p h o s p h a t e m e l t s a r e composed o f a huge number of phosphate species that are undergoing constant r e o r g a n i z a t i o n , as judged by a n a l y s e s o f t h e g l a s s e s f o r m e d by q u e n c h i n g t h e s e m e l t s . When c r y s t a l s f o r m i n h i g h t e m p e r a t u r e systems t h e segments o f p h o s p h a t e s t h a t t r a n s f e r from t h e melt phase t o t h e c r y s t a l l i n e phase a t t h e boundry of c r y s t a l l i z a t i o n are limited to four models. 1. The c r y s t a l s may grow one P 0 g r o u p a t a t i m e u n d e r which conditions a m o l e c u l e - i o n o f 10,000 phosphate groups would require the formation of 9,999 Ρ-0-Ρ l i n k a g e s on t h e s u r f a c e o f t h e c r y s t a l t o c r e a t e a s i n g l e molecule-ion. 3

2. The P 0 g r o u p s c o u l d b e t r a n s p o r t e d t o t h e s u r f a c e o f the crystals as c l u s t e r s of threes, as the stable triphosphate chains or rings. 3

3. The P 0 g r o u p s c o u l d be t r a n s p o r t e d i n t e r m e d i a t e l e n g t h o f phosphate chains i n d i c a t e d b y some p h y s i c a l d a t a . 3

as or

short rings

to as

4. The c r y s t a l s c o u l d grow f r o m v e r y l a r g e m o l e c u l e - i o n s 10,000 P 0 l o n g i n t h e m e l t p h a s e a n d t h e c r y s t a l s c o u l d grow f r o m s i n g l e s e g m e n t s . 3

To

consider

each

model

i t

is

unlikely

that


single

7. GRIFFITH

95


monometaphosphate o r o r t h o p h o s p h a t e g r o u p s a r e f o r m e d t o be t r a n s p o r t e d from t h e m e l t t o t h e c r y s t a l l i n e phase. G l a s s e s f o r m e d f r o m c o n d e n s e d p h o s p h a t e m e l t s c o n t a i n no d e t e c t a b l e o r t h o p h o s p h a t e when a n a l y z e d s o o n a f t e r t h e y a r e p r e p a r e d . (23) T h e r e a r e s e v e r a l r e a s o n s why segments a s s h o r t a s t h r e e phosphate groups c o u l d be i n v o l v e d i n t h e t r a n s f e r o f P0 groups from a m e l t phase t o t h e c r y s t a l l i n e phase o f a long chain polyphosphate. A s n o t e d a b o v e when q u e n c h e d potassium phosphate melts y i e l d r i n g s t h a t a r e n o t found i n t h e c r y s t a l l i z e d systems. The t r i p o l y - p h o s p h a t e t h a t r e s u l t s from r i n g opening i s t o o s h o r t t o knot. I ti s well known t h a t p o l y p h o s p h a t e s r e o r g a n i z e t o c y c l i c t r i m e t a p h o s p h a t e s i n aqueous s o l u t i o n s , b u t t h i s i s y e t a n o t h e r mechanism. (14)


3

Surface tension and d e n s i t y work s u g g e s t that the t r a n s f e r u n i t may r a n g e f r o m t h e d i m e r t o a s many a s twelve phosphate groups. T h e most l i k e l y c o n d i t i o n s a r e t h a t t h e phosphate i s t r a n s p o r t e d a s segments o f s i x t o e i g h t p h o s p h a t e g r o u p s . I t was d e m o n s t r a t e d b y v i s c o s i t y m e a s u r e m e n t s o f p o l y p h o s p h a t e m e l t s t h a t t h e f l o w segment i s b e t w e e n s i x a n d e i g h t p h o s p h a t e g r o u p s i n l e n g t h . (15) Segments o f t h i s l e n g t h a r e s h o r t enough a n d r i g i d enough t o be f r e e o f entanglement w i t h o t h e r c h a i n s and s h o u l d add t o a c h a i n growing on t h e s u r f a c e o f a c r y s t a l without encountering large s t e a r i c b a r r i e r s .

Convincing experiments left little doubt that most amorphous p o l y p h o s p h a t e g l a s s e s i n t h e s o d i u m system e x h i b i t some b r a n c h i n g . (16) I t i s u n l i k e l y that long chain branched structures could f i tinto a crystal l a t t i c e without f i r s t rupturing t o destroy the branching point. I t i s w e l l e s t a b l i s h e d t h a t m e l t s w i t h M 0-P 0 > 1 r e s i s t b r a n c h i n g . (13) 2

2

5

During c r y s t a l l i z a t i o n the crystal s u r f a c e grows t o contact f r e s h melt while t h e molecule-ions o f t h e melt a r e t r a n s p o r t e d t o t h e c r y s t a l s u r f a c e by thermal motion. I t i s u n l i k e l y t h a t c h a i n s o f s e v e r a l thousand phosphate groups a r e formed i n the liquid m e l t phase, then t r a n s p o r t e d , i n t a c t , t o t h e s u r f a c e o f t h e growing c r y s t a l templet. It has been claimed that long chain ammonium p o l y p h o s p h a t e s c a n be t r e a t e d w i t h p o t a s s i u m h y d r o x i d e t o form l o n g c h a i n polyphosphates t h a t c r y s t a l l i z e from s o l u t i o n as t h e dihydrate. I t was s u g g e s t e d t h a t t h e p h o s p h a t e was a K u r r o l ' s s a l t , b u t o n l y a f t e r t h e s a l t



96 e


h a d b e e n h e a t e d t o 6 0 0 C . (27) There i s doubt t h a t l o n g c h a i n s c a n f i t d i r e c t l y i n t o a c r y s t a l l a t t i c e when c r y s t a l l i z e d from an aqueous s o l u t i o n . Admittedly the chaotic reorganization that takes place in high t e m p e r a t u r e m e l t s d e f i n i t e l y does n o t o c c u r i n aqueous s o l u t i o n s a t a t m o s p h e r i c p r e s s u r e , b u t more e v i d e n c e i s needed b e f o r e i t i s a c c e p t e d t h a t l o n g c h a i n a l k a l i metal p o l y p h o s p h a t e s can c r y s t a l l i z e from aqueous media. The l o n g c h a i n p o l y p h o s p h a t e s grown a s c r y s t a l s a r e a more n a r r o w d i s t r i b u t i o n of chain lengths than the amorphous s y s t e m s when m e a s u r e b y i n t r i n s i c v i s c o s i t y o r g e l chromatography. (28) The n a r r o w d i s t r i b u t i o n w o u l d be r e q u i r e d b e c a u s e t h e m o l e c u l e s must f i t a n o r d e r l y l a t t i c e , but i t has been p o i n t e d out t h a t a s i n g l e l o n g c h a i n p o l y p h o s p h a t e may r e s i d e i n t e n - t h o u s a n d o r more unit cells. (20) End g r o u p s o c c u r s o s e l d o m t h a t a c r y s t a l c a n accommodate t h e s m a l l d i s l o c a t i o n s w i t h o u t changing the x-ray p a t t e r n o f the phosphate. C r o s s - l i n k e d Potassium K u r r o l ' s S a l t T h e r e i s no r e o r g a n i z a t i o n i n a c r y s t a l o f p o t a s s i u m Kurrol's salt even at temperatures near the melt t e m p e r a t u r e b e c a u s e t h e r e a r e no p h a s e t r a n s i t i o n s i n potassium Kurrol's s a l t c r y s t a l s . I n t h e sodium system the crystals of Kurrol's salt can suffer a phase transition. A t a phase t r a n s i t i o n t h e chaos o f t h e melt i s recaptured over the i n t e r v a l of the t r a n s i t i o n . The x - r a y p a t t e r n s o f t h e c r y s t a l l i n e l o n g c h a i n (1,000 o r more p h o s p h o r u s atoms p e r a v e r a g e c h a i n ) p o t a s s i u m Kurrol's s a l t are highly reproducible despite the fact t h a t t h e p h o s p h a t e s c a n be c r y s t a l l i z e d f r o m a v a r i e t y o f melt compositions. An o u t s t a n d i n g example o f this b e h a v i o r i s the growth o f c r y s t a l s o f potassium K u r r o l ' s s a l t i n t h e more b a s i c p o l y p h o s p h a t e p h a s e r e g i o n s and the potassium Kurrol's salt grown in the acidic u l t r a p h o s p h a t e phase r e g i o n s a r e i d e n t i c a l . (19) The s o l u t i o n p r o p e r t i e s o f the l o n g c h a i n l e n g t h phosphates a r e v e r y d i f f e r e n t d e p e n d i n g on t h e c o m p o s i t i o n o f t h e m e l t f r o m w h i c h t h e c r y s t a l s were grown and y e t t h e xr a y p a t t e r n s a r e p r e c i s e l y t h e same. I t h a s b e e n assumed f o r many y e a r s t h a t t h e d i f f e r e n c e b e t w e e n t h e two p r e p a r a t i o n s was c r o s s - l i n k i n g o f t h e m o l e c u l e - i o n s o f l o n g c h a i n p o l y p h o s p h a t e s grown i n c r y s t a l s f r o m m e l t s w i t h M 0-P 0 r a t i o s l e s s t h a n u n i t y . (20) 2

2

5

The e v i d e n c e f o r c r o s s - l i n k i n g i n c r y s t a l l i n e i n o r g a n i c polyphosphates to convert them to crystalline ultraphosphates with small degrees of c r o s s - l i n k i n g i s circumstantial rather than d i r e c t . This i s not to question the triply-linked phosphate groups i n the


7. GRIFFITH

97


u l t r a p h o s p h a t e r e g i o n o f t h e condensed phosphate systems. C r y s t a l l i n e phosphorus pentoxide, P4O , i s c o m p l e t e l y triply-linked. The q u e s t i o n i s whether o r n o t t h e crystalline polyphosphates grown from ultraphosphate melts are very long chain polyphosphates or are ultraphosphates with small degrees o f c r o s s - l i n k i n g . 10

The a q u e o u s s o l u t i o n p r o p e r t i e s o f p o t a s s i u m Kurrol's s a l t p r e p a r e d from u l t r a p h o s p h a t e m e l t s a r e n o t h i n g l e s s than spectacular. A 1% s o l u t i o n o f p o t a s s i u m K u r r o l ' s s a l t c r y s t a l l i z e d f r o m a m e l t w i t h a M 0-P 0 = 1.0 i s o b v i o u s l y v i s c o u s , b u t a s a l t make w i t h a M 0-P 0 = 0.98 i s s t r i n g y b r e a k i n g i n t o t h r e a d s when a r o d i s removed from t h e s o l u t i o n . The K u r r o l ' s s a l t s c o u l d d e r i v e t h e i r aqueous s o l u t i o n p r o p e r t i e s from c r o s s - l i n k i n g o r from u l t r a - l o n g s i n g l e stranded l i n e a r molecules. When t h e calcium polyphosphate system i s compared with the potassium Kurrol's salt systems the evidence is controversial. 2

2


2

Triply-linked

5

2

5

Phosphate Groups

If the crystalline inorganic phosphates grown i n ultraphosphate media contain t r i p l y - l i n k e d phosphate groups they are either isopolyphosphates or ultraphosphates. An example i s a P 0 g r o u p s bonded t h r o u g h an oxygen l i n k a g e s t o t h r e e o t h e r P0 groups. Three types of triply-linked phosphate groups a r e possible. They a r e : 3

3

Type I C r o s s - l i n k i n g 0 0 0 0 0 0

(charges a r e

ignored) -0P0P0P0P0P0P0 0 0 0 0 0 0P0 0 0 0 0 0 0 -0P0P0P0P0P0P0 0 0 0 0 0

where t h e r e a r e

two t r i p l y - l i n k e d P03 g r o u p s , b u t t h e r e a r e two o t h e r t y p e s of bonding f o r branching and c r o s s - l i n k i n g . In the s t r u c t u r e shown a b o v e t h e r e i s a s i n g l e P03 i n t h e bridge. T h e r e i s no r e a s o n t h a t t h e r e c o u l d n o t b e s e v e r a l P 0 g r o u p s b e t w e e n t h e two l o n g e r c h a i n s . It i s a l s o p o s s i b l e t h a t t h e r e c o u l d b e no P03 b e t w e e n t h e chains as i n t h e f o l l o w i n g s t r u c t u r e . 3



98 Type I I

Cross-linking 0 0 0 0 0 0

(charges a r e

ignored) -0Ρ0Ρ0Ρ0Ρ0Ρ0ΡO Ο I Ο Ο Ο Ο ο ο I Ο Ο Ο -ΟΡΟΡΟΡΟΡΟΡΟΡ0 0 0 0 0 0 where t h e r e a r e b u t two t r i p l y - l i n k e d

P03 g r o u p s .


There i s then t h e branched isopolyphosphate t h a t c o n t a i n s a s i n g l e t r i p l y - l i n k e d P03 g r o u p a s b e l o w . Type I I I

Branching 0 0 0 0 0 0

(charges a r e

ignored) -OPOPOPOPOPOP0 0 0 0 0 0 ΟΡΟ

ο

ΟΡΟ

ο

ΟΡΟ

In an attempt t o o b t a i n d i r e c t e v i d e n c e f o r t h e p r e s e n c e of cross-linking i n t h e potassium polyphosphates c r y s t a l l i z e d f r o m u l t r a p h o s p h a t e s m e l t s two t o o l s were chosen. C r o s s - l i n k i n g s h o u l d i n t h e o r y be observed by e i t h e r phase c h e m i s t r y o r x-ray. Also the existence of end a n d m i d d l e g r o u p p h o s p h o r u s i s w e l l e s t a b l i s h e d i n nmr s t u d i e s o f i n o r g a n i c p h o s p h a t e s w h i l e t r i p l y - l i n k e d phosphate groups have been r e p o r t e d i n o r g a n i c phosphate systems. Cross-linking i n polyphosphates s h o u l d be d i r e c t l y o b s e r v a b l e by t u n n e l i n g microscopy, b u t time d i d n o t p e r m i t t h e c o m p l e t i o n o f t h i s a p p r o a c h i n t h i s work.

The l i n e a r m o l e c u l e - i o n s o f K u r r o l ' s s a l t s p a s s t h r o u g h a thousand o r so u n i t c e l l s b e f o r e t e r m i n a t i n g . This suggests t h a t i n a K u r r o l ' s s a l t w i t h a K 0-P 0 ratio e q u a l t o 0.98 o n t h e a v e r a g e e v e r y f i f t y c e l l s s h o u l d b e a c r o s s - l i n k i n g c e l l o f o n e o f t h e two t y p e s listed above. The p o t a s s i u m Kurrol's salt cells contain s e g m e n t s o f two h e l i c a l c h a i n s a n d f o u r P 0 g r o u p s p e r unit c e l l . Cross-linking within these c e l l s should create a very complex u n i t cell a n d a n e v e n more complicated l a t t i c e . 2

2

5

3

I t i s u n l i k e l y t h a t a c r y s t a l c o m p l e x enough t o c o n t a i n phosphate c h a i n s o f s e v e r a l thousand phosphate groups


7. GRIFFITH

99


c o u l d t o l e r a t e m o l e c u l e s w i t h simple b r a n c h i n g groups as shown i n T y p e I I I b r a n c h i n g . T h e r e i s no r e a s o n t o e x p e c t t h a t t h e y a r e e x c l u d e d f r o m amorphous s y s t e m s however. A s s u m i n g t h a t e i t h e r o f t h e two t y p e s o f c r o s s l i n k i n g g r o u p s a r e e q u a l l y p r o b a b l e , T y p e I I s h o u l d be accommodated by a c r o s s - l i n k i n g u n i t c e l l w i t h less d i m e n s i o n a l c o n t o r t i o n . The d i m e n s i o n s o f t h e c e l l w o u l d s h r i n k by one K 0 u n i t p e r c r o s s - l i n k . I f T y p e I were e x h i b i t e d t h e c e l l w o u l d be r e q u i r e d t o i n c r e a s e by one P 0 w h i l e d e c r e a s i n g by ^K 0. E i t h e r t y p e s h o u l d be s e e n i n x-ray patterns. 2


3

2

Three possibilities exist when a salt with a polyphosphate x - r a y p a t t e r n c r y s t a l l i z e s from a m e l t c o n t a i n i n g an e x c e s s o f p h o s p h o r u s p e n t o x i d e . 1. The phosphorus pentoxide is incorporated into the polyphosphate chains converting the chains t o c r y s t a l l i n e u l t r a p h o s p h a t e s . 2. The e x c e s s p h o s p h o r u s p e n t o x i d e d o e s n o t e n t e r t h e polyphosphate c r y s t a l s t r u c t u r e , b u t forms an amorphous p h a s e b e t w e e n t h e c r y s t a l s o f p o l y p h o s p h a t e . The amorphous p h a s e i s n o t d e t e c t e d b y x - r a y . 3. The excess phosphorus p e n t o x i d e does not e n t e r t h e c r y s t a l structure of the polyphosphate, but forms as an ultraphosphate between t h e crystalline polyphosphate c r y s t a l s as a e u t e c t i c phase. (This l a t t e r case i s precisely what happens in the calcium sodium u l t r a p h o s p h a t e system from which c a l c i u m phosphate f i b e r s a r e grown (21) and t h e p h a s e d i a g r a m o f H i l l e t . a l . i s o b e y e d a s i t s h o u l d be.) In the potassium Kurrol's salt phase system the c r y s t a l l i n e analogues t o Ca P 0 o r C a P ^ ^ were n o t f o u n d by a l i t e r a t u r e s e a r c h . (22) The amorphous p o t a s s i u m u l t r a p h o s p h a t e s y s t e m s h a v e b e e n s t u d i e d . (23) Amorphous condensed phosphates are seldom , i f ever, single compounds, b u t a r e a random m i x t u r e s o f compounds and c a n be l a r g e and v e r y c o m p l e x . I f t h e u l t r a p h o s p h a t e s were embedded b e t w e e n c r y s t a l s o f p u r e p o t a s s i u m phosphate f i b e r s t h e y w o u l d be v e r y d i f f i c u l t t o d e t e c t . 2

6

1 7

when d i s s o l v e d i n aqueous s o l u t i o n s o f d i v e r s e ions potassium Kurrol's salt is a viscous solution at c o n c e n t r a t i o n o f 1% p o l y p h o s p h a t e . The "cross-linked" K u r r o l ' s i s e v e n more v i s c o u s a n d e x h i b i t s a s t r i n g i n e s s n o t s e e n i n t h e K u r r o l ' s s a l t s p r e p a r e d w i t h K^0-P 0 r a t i o s equal to unity. The a q u e o u s s o l u t i o n b e h a v i o r o f c r o s s - l i n k e d K u r r o l ' s s a l t may be c a u s e d by t h e a s e c o n d phase of the system superimposed upon the viscous b e h a v i o r o f t h e s o l u t i o n s o f 1.0 K 0 - P 0 r a t i o p o t a s s i u m Kurrol's salt solutions. The e v i d e n c e does not support c r o s s - l i n k i n g as the p r i m a r y r e a s o n t h a t p o t a s s i u m K u r r o l ' s s a l t grown i n ultraphosphate melts e x h i b i t s the very high v i s c o s i t i e s and d r a g r e d u c i n g p r o p e r t i e s a t low c o n c e n t r a t i o n s i n a q u e o u s s o l u t i o n s . (24) I t has never been a d e q u a t e l y 2

2

2

5


5


100

demonstrated that the cross-linking is a part of the molecules in a crystalline phase. It was demonstrated, however, that even amorphous sodium polyphosphate glasses could be made to exhibit the same aqueous solution behavior as the potassium Kurrol's salt grown in melts with an M 0-P 0 ratio less than unity. (25) In the sodium ultraphosphate glasses cross-linking is required and is surely responsible for the behavior. 2

5

In the classic work of H i l l , Foust and Reynolds they prepared the crystalline ultraphosphates, CaP^^ and Ca P 0 , in phase studies. (26) The preparation of the thermodynamically stable salts were elegantly confirmed.(27) Single crystal x-ray studies were used to confirm the structures of both salts. In the work of Glonic, Van Wazer, Kleps, Legeros, and Meyers, (28, 29, 30) also classics, they approached the chemistry of triply-linked phosphorus groups preparing the 1,5-μ-οχοtetrametaphosphate anion in organic media. The 1,5-μoxo-tetrametaphosphate anion is the same anion discovered by H i l l , Foust and Reynolds. 2


2

6

17

Conclusions: It is concluded that the crystalline phase of potassium Kurrol's salt is not cross-linked. The mixture of very long chain polyphosphates and amorphous ultraphosphates dissolve to form highly viscous aqueous solutions. It is also concluded that the seed crystals aiding the growth of ultra long polyphosphate molecule-ions is built up from small segments of polyphosphate formed in a phosphate melt. Tunneling microscopy is a tool currently available potentially capable of definitively resolving the question of cross-linking in crystalline potassium Kurrol's salt. The current evidence strongly suggests that the phase diagram for the system is obeyed. Short chain (n < 50) Kurrol's cannot be prepared on the basic side of the metaphosphate compositions nor can crosslinking of the potassium Kurrol's salt chains occur in the crystals grown on the acidic side of the metaphosphate compos it ion. Literature Cited: 1. Van Wazer, J . R. and Griffith, E. J., J . Am. Chem. Soc. 77, 6140 (1955). 2. Van Wazer, J . R., J . Am. Chem. Sac. 72, 644; 647 (1950). 3. Westman, A. E. R. and Gartaganis, P. Α., J . Am. Ceramics Soc. 40, 293 (1957). 4. Parks, J.R. and Van Wazer, J . R., J . Am. Chem. Sac. 79, 4890 (1957).



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5. Griffith, E. J. and Buxton, R. L . , J . Am. Chem. Sac. 89, 2884 (1967). 6. Griffith, E. J., Proc. Phosphorus Symposium, Duke University, 75, 362, (1981). 7. Pfansteil, R. and Iler, R. Κ., J . Am. Chem. Soc. 74, 6059 (1952). 8. Morey, G. W., Boyd, F. R., England, J . L . , and Chen, W. T., J . Am. Chem. Soc. 77, 5003 (1955). 9. Griffith, E. J., U. S. Patent 4,360,625, November 23, 1982. 10. Griffith, E. J . and Kodner, I. J., U. S. Patent 3,312,523, April 4, 1967. 11. Corbridge, D. E. C., Structural Chemistry of Phosphorus. pg. 143, Elsevier Scientific Publishing Company, Amsterdam 1974. 12. Crutchfield, Μ. Μ., Private communication, Monsanto Company; Griffith, E. J., International Conference On Phosphate Chemistry. Tokyo, Japan, July, 1991. 13. Van Wazer, J . R., J . Am. Chem. Soc. 78, 5709 (1956). 14. Osterheld, Κ., Topics In Phosphorus Chemistry Vol. 7, pg. 103 Ed. M. Grayson and E. J. Griffith, John Wiley and Sons, New York, Ν. Y. 1972 15. Callis, C. F., Van Wazer, J . R. and Metcalf, J . S., J . Am. Chem. Sac. 77, 1471 (1955). 16. Strauss, U. P., Smith, Ε. H. and Wineman, P.L., J . am. Chem. Soc. 75, 3935 (1953). Strauss, U. P. and Treitler, T. L . , ibid. 77, 1473 (1955). 17. Stahlheber N. E., U. S. Patent 3,723,602 March 27, 1973. 18. Filer, W. Α., Unpublished Monsanto report. 19. Ngo, Τ. Μ., and May, F. L . , Unpublished Monsanto Report done for this work. 20. Van Wazer, J . R., Phosphorus and Its Compounds, pg. 676, Interscience Publishers, Inc. New York, Ν. Y., 1958; ibid. pg. 762. 21. Griffith, E. J., Proc. International Symposium On Phosphorus Chemistry, pg. 361, Duke University, 1981. 22. Morey, G. W., J. Am. Chem. Soc. 74, 5783 (1952). 23. Kalmykov, S. I., Bekturov, A. Β., Shevchenko, Ν. P., Malakohova, Κ. I., and Poletaev, Ε. V., Izv. Akad. Nauk. Kaz. SSR. Ser. Khim. 23, 1 (1973). 24. Hunston, D. L . , Griffith, J . R., Little, R. C., Nature 245, 141 (1973). 25. McCullough, J . F., Unpublished data, private demonstration. 26. Hill, W. L . , Faust, G. T. and Reynolds, D. S., Am. J . Sci. 242, 457, 542 (1944). 27. Bencher, Μ., Mat. Res. Bull. 4, 15 (1969). 28. Glonic, T., Meyers, T. C. and Van Wazer, J . R., J . Am. Chem. Soc. 92. 7214 (1940)._ 29. Glonic, Τ. , Van Wazer, J . R., Kleps, R. A. and Meyers, T. C., Inorg. Chem. 13, 233 (1974). 30. Van Wazer, J. R., and Legeros, R. Z., International Congress On Phosphorus Compounds, Rabat, October, 1977. pg.95 RECEIVED December 30,

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Factors Influencing the Chain Lengths of Inorganic Polyphosphates

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