HANDLING AND USES OF THE ALKALI METALS

Manufacture and Use of Potassium Superoxide C. B. J A C K S O N and R. C. WERNER

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Mine Safety Appliances Co., Callery, Pa.

Commercial quantities of potassium superoxide are made by atomizing molten potassium with air. The oxidation product so produced consists of a very finely divided yellow powder approaching very closely the theoretical composition of K O . Potassium superoxide is used to supply oxygen and to absorb carbon dioxide and water in self-contained lung-actuated breathing apparatus. A description is given of the treatment of the superoxide for its use within canisters for respiratory equipment. Flow diagrams of the equipment are presented along with some considerations of the use of the equipment under conditions of extreme exercise. 2

T H E m a n u f a c t u r e of potassium superoxide for respiratory equipment was the o u t g r o w t h of a research p r o g r a m started i n 1935 b y the U . S . N a v y to develop a self-contained b r e a t h i n g apparatus without use of compressed o x y g e n or air. C o n siderable effort h a d a l r e a d y been e x p e n d e d to m a k e s o d i u m peroxide w o r k , p a r t i c u l a r l y i n F r a n c e a n d G e r m a n y , w i t h o u t success. M i l l e r a n d his associates (8) at the N a v a l Research L a b o r a t o r y t u r n e d to p o tassium superoxide. T h e y m a d e s o d i u m react w i t h potassium chloride to f o r m a p o t a s s i u m - s o d i u m alloy ( 6 0 % p o t a s s i u m ) . V a p o r phase combustion of this alloy f o r m e d a m i x t u r e of s o d i u m p e r o x i d e a n d potassium superoxide, c o m m o n l y r e f e r r e d to as M O X (8). T h i s m i x t u r e was adequate b u t inferior to p u r e superoxide. H o w e v e r , p r o d u c t i o n of the superoxide r e q u i r e d the t h e n - u n a v a i l a b l e metallic potassium f o r its success. T h e m a n u f a c t u r e of potassium has been described (5). F o r some time, potassium superoxide was regarded as the tetroxide ( K 0 ) . H o w e v e r , magnetic a n d x - r a y studies p r o v e d it to be K 0 (1, 6, 9). T h e c o m p o u n d has a m e l t i n g point of 380 ° C , a dissociation temperature, at 1 atm. of 600 ° C , a n d a density of 2.14 grams per cc. (7). 2

4

2

P o t a s s i u m superoxide is p r e p a r e d b y the M i n e Safety A p p l i a n c e s C o . f r o m metallic potassium b y atomizing the m o l t e n potassium i n a n excess of a i r (2). T h e apparatus ( F i g u r e 1) consists s i m p l y of a fluid spray g u n such as is generally used to a p p l y paints or other surface coatings. T h e g u n is adjusted to dicharge a fine spray of m o l t e n potassium into a n a i r stream h a v i n g a n o x y g e n content of f r o m 13 to 3 5 % b y v o l u m e i n a m i x t u r e w i t h nitrogen. Instantaneous oxidation occurs, w i t h the a i r stream acting to q u e n c h the oxide b e l o w its m e l t i n g point s u b s t a n t i a l l y as r a p i d l y as it is f o r m e d . T h e o v e r - a l l reaction is exothermic, w h i c h evolves sufficient heat (about 135 kcal.) to c a r r y the reaction of a l l the potassium to c o m pletion. 174

In HANDLING AND USES OF THE ALKALI METALS; Advances in Chemistry; American Chemical Society: Washington, DC, 1957.

175

J A C K S O N A N D WERNER—POTASSIUM SUPEROXIDE


Figure 1.

Potassium oxidation unit

It has been f o u n d that i f f r o m 5 to 15 times the theoretical amount of a i r r e q u i r e d f o r oxidation (9.2 cubic feet of a i r p e r p o u n d of potassium) is s u p p l i e d at about 75° C , the oxide is not overheated i n the collection tank. T h e p r o d u c t — a pale y e l l o w , light, fluffy p o w d e r of a p p r o x i m a t e l y theoretical available o x y g e n content—is collected i n large tanks w i t h cyclone separation i n yields of 9 5 % . A t present, the capacity is a p p r o x i m a t e l y 3 tons p e r d a y .

Use A t present, the o n l y i m p o r t a n t use for potassium superoxide is i n s e l f - c o n tained b r e a t h i n g apparatus. It is i d e a l for this purpose because of its a b i l i t y to control h u m i d i t y , evolve oxygen, a n d remove the carbon d i o x i d e a n d water f r o m the wearer's e x h a l e d b r e a t h . F o r use i n canisters for respiratory equipment, the fluffy powder is pressed i n a m o l d u n d e r 1800 pounds p e r square i n c h , t h e n g r a n u l a t e d a n d screened to a p p r o x i m a t e l y 2 to 4 mesh. T h i s results i n a change of density of f r o m 0.25 i n the p o w d e r to 0.72 i n the g r a n u l a r m a t e r i a l . T h e m a t e r i a l p r o d u c e d b y M i n e Safety A p p l i a n c e s C o . has a n available o x y g e n content a p p r o a c h i n g the theoretical v a l u e of 236.6 cc. per g r a m . T h e reactions of potassium superoxide w i t h w h i c h we are concerned a r e : 2K0 + H 0 > 2 K O H + 3/2 0 2

2

2

2KOH + CO.

Figure 2.

> K2CO3 + H 0 2

Section of Chemox canister


A D V A N C E S IN CHEMISTRY SERIES

176

H e a v y m e t a l oxides of compounds, such as copper oxide, n i c k e l oxide, cobalt oxide, a n d m a g n e s i u m dioxide, are m i x e d i n the charge to catalyze the reaction of the potassium superoxide w i t h c a r b o n dioxide a n d moisture. It is important, h o w ever, that o n l y a p o r t i o n of the superoxide be m i x e d w i t h catalyst to a v o i d excessive l i b e r a t i o n of o x y g e n .


T h e canister design is such that the e x h a l e d b r e a t h passes d o w n a center tube, filters u p t h r o u g h the potassium superoxide b e d , a n d passes out t h r o u g h a n a n n u l a r space ( F i g u r e 3 ) .

Figure 3.

Schematic diagram of Che-

mox breathing apparatus

Figure 4. Industrial application of breathing apparatus


J A C K S O N A N D WERNER—POTASSIUM

SUPEROXIDE

177

U n d e r h a r d w o r k conditions, a p p r o x i m a t e l y 8 0 % of the theoretical o x y g e n available i n the potassium superoxide is l i b e r a t e d a n d 70% of the c a r b o n dioxide absorbing capacity is utilized. W i t h m i l d w o r k i n g conditions these figures are slightly higher. H o w e v e r , the c a r b o n dioxide is 99 + % absorbed u n t i l the potas s i u m superoxide is p r a c t i c a l l y spent.


D u r i n g assembly, a p p r o x i m a t e l y 2 pounds of the superoxide are p a c k e d i n a specially designed canister ( F i g u r e 2 ) , w h i c h comprises the heart of the b r e a t h i n g apparatus (3,4). T h e efficiency of the b r e a t h i n g unit depends to a v e r y great extent o n both the construction of the canister a n d the m a n n e r i n w h i c h it is packed. B r e a t h i n g apparatus have been designed, tested, a n d constructed i n large quantities for b o t h m i l i t a r y a n d c o m m e r c i a l applications. In actual use, these apparatus have g i v e n complete respiratory protection for a p p r o x i m a t e l y 1 hour e v e n u n d e r conditions of extreme exertion. T h e y have been w i d e l y used i n m i n e rescue w o r k , i n fire fighting, a n d w h e r e v e r nonrespirable atmospheres are e n c o u n tered ( F i g u r e s 4 a n d 5 ) . S u p e r o x i d e - f i l l e d canisters have also been successfully used b y several m o u n t a i n - c l i m b i n g expeditions (10).

Figure 5.

Rescue with Chemox apparatus

Literature Cited (1) (2) (3) (4) (5) (6) (7) (8) (9) (10)

H e l m s , Α . , K l e m m , W . , Z. anorg. u. allgem. Chem. 241, 97 (1939); 242, 201 (1939). J a c k s o n , C . B. (to M i n e Safety A p p l i a n c e s C o . ) , U. S. Patent 2,405,580 ( A u g . 13, 1946). J a c k s o n , C . B., B e a h m , H. C . , Van A n d e l , A. C., Ibid., 2,494,131 (Jan. 10, 1950). J a c k s o n , C . B., V a n A n d e l , A. C., Ibid., 2,517,209 ( A u g . 1, 1950). J a c k s o n , C . B. W e r n e r , R. C . , A D V A N C E S I N CHEM. SER. NO. 19, 169 (1957). K a s a t o c h k i n , W . , K o t o v , V., J. Chem. Phys. 4, 458 (1936), K l e i n b e r g , J., "Unfamiliar O x i d a t i o n States a n d T h e i r S t a b i l i z a t i o n , " p.34, T a b l e III, U n i v e r s i t y of K a n s a s Press, L a w r e n c e , 1950. M i l l e r , R. R., associates, N a v a l Research L a b o r a t o r y , " P a r t i a l Reports on O x y g e n Source M a t e r i a l s , " N o s . 1-17 ( M a r c h 5, 1936, to A u g u s t 1945). N e u m a n , E. W . , J. Chem. Phys. 2, 31 (1934). W y s s - D u n a n t , E., Bull. schweiz. Akad. med. Wiss. 9, 221-9 (1953).


HANDLING AND USES OF THE ALKALI METALS

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