Laboratory Techniques for Handling High-Concentration Liquid Ozone A. C. JENKINS
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Research and Development Laboratory, Linde Co., a Division of Union Carbide Corp., Tonawanda, Ν. Y.
Because of the unstable nature of ozone, the usual techniques for determination of physical properties can rarely be applied. Contact with many mate rials generally used in experimental work, such as rubber tubing, organic stopcock grease, and mercury, must be avoided. The quantity of pure liquid ozone must be kept small in the interests of safety. Even 1 ml. of undiluted liquid ozone can cause a disastrous explosion unless suitable precautions are taken to protect the experimenter.
T h e p r o d u c t i o n of d i l u t e l i q u i d ozone a n d i t s c o n c e n t r a t i o n o n a l a b o r a t o r y scale a r e r e l a t i v e l y s i m p l e . P u r e o x y g e n is p a s s e d t h r o u g h a series of t h r e e o r f o u r glass B e r t h e l o t t u b e s ( F i g u r e 1) i m m e r s e d i n a w a t e r b a t h . T h e c e n t r a l p o r t i o n of e a c h t u b e i s f i l l e d w i t h s l i g h t l y a c i d i f i e d w a t e r a n d c o n t a i n s a m e t a l r o d . T h e c e n t e r r o d s of t h e t u b e s a r e a l l w i r e d i n p a r a l l e l a n d c o n n e c t e d t o t h e h i g h v o l t a g e t e r m i n a l of a 15,000v o l t t r a n s f o r m e r . T h e o u t e r b a t h ( F i g u r e 2) is g r o u n d e d . O x y g e n i s p a s s e d t h r o u g h t h e 2 - m m . a n n u l a r space b e t w e e n t h e i n n e r a n d o u t e r t u b e s of t h e o z o n i z e r , a n d t h e o z o n e - o x y g e n m i x t u r e p r o d u c e d i n t h e B e r t h e l o t t u b e s is c o n d e n s e d i n a glass b u l b i m m e r s e d i n l i q u i d o x y g e n . T h e ozone c o n t e n t of t h e m i x t u r e v a r i e s f r o m 1 t o 5 m o l e % , d e p e n d i n g u p o n r a t e of flow a n d t e m p e r a t u r e . B e c a u s e of t h e g r e a t difference i n v a p o r pressures b e t w e e n l i q u i d o x y g e n a n d l i q u i d ozone, o x y g e n gas c a n b e p u m p e d off t h e m i x t u r e w h i l e i t i s a t t h e n o r m a l b o i l i n g p o i n t (—183° C . ) of l i q u i d o x y g e n . A t t h i s t e m p e r a t u r e l i q u i d o z o n e has a v a p o r p r e s s u r e of o n l y 0.1 m m . of m e r c u r y , a n d i t s p u r i t y c a n e a s i l y b e c h e c k e d b y a v a p o r pressure measurement. D i l u t i o n b y e v e n 0.1 m o l e % of o x y g e n increases t h e v a p o r p r e s s u r e f r o m 0.1 t o 6.5 m m . of m e r c u r y ( F i g u r e 3 ) . O n a s u l f u r i c a c i d m a n o m e t e r , 99.99 m o l e % ozone w o u l d g i v e a r e a d i n g of 6 m m . , c o m p a r e d w i t h less t h a n 1 m m . f o r p u r e ozone. I n the l a b o r a t o r y at T o n a w a n d a , Ν . Y . , the l i q u i d ozone-oxygen m i x t u r e has a l w a y s b e e n c o n c e n t r a t e d b y t h e m e t h o d of L a i n e ( F i g u r e 2). L a i n e (8) u s e d t w o glass b u l b s , e a c h flushed o u t w i t h n i t r o g e n gas, e v a c u a t e d , a n d filled w i t h t h e v a p o r f r o m t h e m i x t u r e . T h i s series of o p e r a t i o n s is c o n d u c t e d a l t e r n a t e l y i n t h e t w o b u l b s . Lainé's s y s t e m a v o i d s p a s s i n g o x y g e n a n d t r a c e s of ozone t h r o u g h t h e p u m p i n g s y s t e m . D i r e c t p u m p i n g o n t h e l i q u i d ozone i s u s e d o n l y i n t h e final stage of c o n c e n t r a t i n g th* ozone. F r o m t h e c o n c e n t r a t i n g s y s t e m , l i q u i d ozone i s v a p o r i z e d as n e e d e d a n d γ α condensed i n t h e a p p a r a t u s t o be used f o r m a k i n g t h e p h y s i c a l measurements. T h e
13 In OZONE CHEMISTRY AND TECHNOLOGY; Advances in Chemistry; American Chemical Society: Washington, DC, 1959.
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ADVANCES
IN CHEMISTRY SERIES
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2 MM q/ip S MM. O.o. Tus/Ajq
Figure
1.
OuTGR SHaLL - 23MM-O.O. 7
