N E W CHEMICALS
Radioactive gas mixtures c e r t i f i e d t o a high degree of accuracy are now available t h r o u g h t h e c o m b i n e d e f f o r t s of M a t h e son Gas P r o d u c t s a n d Gollob A n a l y t i c a l Service. N e w p r i m a r y s t a n d a r d s will i n c l u d e Gollob's radioanalysis a c c u r a t e t o ± 5 % of c o m p o n e n t v a l u e a n d a l s o a m a s s s p e c t r o m e t e r a n a l y s i s for i m p u r i t i e s as well as for c o m p o n e n t s of t h e b a c k g r o u n d gas m i x t u r e . Certified s t a n d a r d s at lower cost are available w i t h radioanalysis accurate to ± 1 0 % . A l m o s t a n y gas or c o m b i n a t i o n of gases can be b l e n d e d with a radioactive c o m p o n e n t , p r o v i d e d t h e i n g r e d i e n t s d o not react c h e m i c a l l y or explosively w i t h each other. M i x t u r e s c o n t a i n i n g n u c l i d e s of krypton-85, tri t i u m , sulfur-35, a n d carbon-14 are of f e r e d . M a t h e s o n Gas P r o d u c t s . 201933-2400 441 Ion-exchange r e s i n s of f i n e m e s h in narrow particle ranges (37-44 /xm) for high-resolution l i q u i d chromatography i n c l u d e Bio-Rex 5, p o l y a l k y l a m i n e , inter m e d i a t e base resin; 9, p y r i d i n i u m , s t r o n g base resin; 70, carboxylic a c i d , w e a k acid resin; 63, p h o s p h o r i c a c i d , i n t e r m e d i a t e acid r e s i n ; a n d 40, s u l f o n a t e d p h e n o l i c , s t r o n g acid resin. $25/25 g r a m s . BioRad Laboratories. 415-234-4130 442 Surface-area standards i n c l u d e 11 dif f e r e n t p o w d e r s w i t h surface areas rang i n g f r o m 0.66 t o 1000 s q u a r e m e t e r s per g r a m . Mean d i a m e t e r s are also given for each s t a n d a r d . D u k e S t a n d a r d s Co. 415-328-2400 443 R e a g e n t - g r a d e acetic a c i d s u i t a b l e for c h o l e s t e r o l d e t e r m i n a t i o n s has special controls t o l i m i t a l d e h y d e s ; a m a x i m u m l i m i t of 0.05% a c e t a l d e h y d e e n s u r e s a low level of t h i s i m p u r i t y . J . T. Baker C h e m i cal Co. 201-859-2151 444 Ultrex high-purity materials for l i q u i d crystal research i n c l u d e cholesteryl chlo ride a n d cholesteryl acetate for prepara t i o n of l i q u i d crystals a n d four m a t e r i a l s w h i c h have two or more carefully d e f i n e d t r a n s i t i o n t e m p e r a t u r e s . J . T. Baker C h e m i c a l Co. 201-859-2151 445 New chiral nmr shift reagent, Eu(TFC)·,, tris[3 - t r i f l u o r o m e t h y l h y d r o x y m e t h y l e n e ) d'-camphorato] e u r o p i u m ( l l l ) , can be used for t h e direct d e t e r m i n a t i o n of e n a n t i o m e r i c c o m p o s i t i o n (optical p u r i t y ) w i t h nuclear m a g n e t i c resonance spec t r o m e t r y . T h e material has been suc c e s s f u l l y a p p l i e d in Eu(TFC) 3 /substrate ratios up to 0.7 to alcohols, k e t o n e s , esters, e p o x i d e s , a n d a m i n e s . $30/ g r a m ; $135/5 g r a m s . Bio-Rad Labora tories. 415-234-4130 446
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