J u l y , 1915
T H E J O U R N A L O F I N D U S T R I A L A N D EA’GINEERING C H E M I S T R Y
T H E SPECIFIC ABSORPTION OF REAGENTS FOR GAS ANALYSIS
587
For example, t h e specific absorption a t room temperature of a certain solution of alkaline pyrogallol B y R. P. ANDERSON f o r oxygen, obtained b y shaking a mixture of gases Received February 10, 1915 containing 2 1 per cent oxygen with t h e reagent for 3 A knowledge of t h e absorbing power of t h e reagents minutes in t h e Hempel double pipette, was found t o t h a t are commonly used in gas analysis for t h e gases be j . By this is meant t h a t successive samples of a absorbed b y t h e m a n d for t h e conditions under which gas mixture of t h e above composition were analyzed they are ordinarily employed would be of considera- for oxygen by pyrogallol in t h e manner above indible value t o the gas analyst. Definite information cated until t h e reagent was no longer capable of removof this n a t u r e is for the most p a r t lacking. Hempell ing all of t h e oxygen in t h e t i m e allotted. T h e total has proposed t h e t e r m “analytical absorbing power,” a m o u n t of oxygen absorbed u p t o t h a t point was tl suitable expression for this property, b u t his method found t o be j times t h e volume of t h e reagent t h a t of determining i t seems open t o objection. &4ccord- was employed. ing t o his method, a n excess of pure gas was placed in Determinations of specific absorption are being made contact with I cc. of reagent over mercury a n d shaken in this laboratory in connection with investigations with t h e reagent a s long “als noch schnelle Absorpon t h e most desirable concentrations of the various tion erfolgte, so dass in Laufe einer Minute mindereagents a n d t h e most desirable conditions for their stens mehrere Kubikzentimeter \-erschwanden.” T h e use. T h e results on alkaline pyrogallol are given in decrease in volume t h u s obtained was divided b y four the following article. a n d this value termed t h e analytical absorbing CORNELLUNIVERSITY,I T H A C A , N E W YORK power. S o a t t e m p t was made t o determine t h e absolute absorbing power of t h e reagent, nor was t h e REAGENTS FOR USE I N GAS ANALYSIS reagent required t o remove t h e gas completely as i t I. ALKALINE PYROGALLOL must in actual service. T h e rapidity with which a B y R . P. ANDERSOX reagent absorbs a pure gas t h a t is present in excess Received February 10, 1915 is quite different from t h a t with which i t completely HISTORICAL R f i S U M k A N D I N T R O D U C T I O N removes t h e gas from its mixture with other gases. T o Dobereiner’ is attributed the discovery of the I n t h e first case: t h e pressure t h a t is exerted b y the gas is presumably t h a t of t h e atmosphere, while in absorption of oxygen b y an alkaline solution of pyrothe second case, t h e partial pressure of t h e gas becomes gallol. Liebig* was t h e first t o utilize this reaction less a n d less until i t equals zero or is so small a s t o for t h e quantitative removal of oxygen from its mixbe negligible for technical purposes. In general, t u r e with other gases. He employed a solution of as t h e pressure becomes less, t h e rapidity of t h e ab- potassium hydroxide of I . 4 specific gravity and added sorption decreases, t h e last traces of t h e gas being t o i t one-half its volume of a solution of pyrogallol absorbed with difficulty, or not a t all. It is evident, containing I g. t o j-6 cc. of water. Much later therefore. t h a t t h e values t h a t are obtained b y H e m - Weyl a n d Zeitler3 studied t h e effect upon t h e absorbpel’s method have little bearing upon t h e efficiency of ing power of the reagent of varying t h e concentrathe various reagents for quantitative absorptions, tion of t h e alkali. I n their work. a definite volume a n d t h a t t h e y afford t h e analyst no certainty t h a t his of air was aspirated through a U-tube t h a t contained reagents m a y be used until t h e y have absorbed t h e broken glass a n d a measured volume of the alkaline q u a n t i t y of gas indicated b y t h e analytical absorbing solution of pyrogallol. T h e a m o u n t of oxygen t h a t power now assigned t o t h e m without possibility of remained in t h e air after this t r e a t m e n t was determined by titration with a solution of sodium hypothe incomplete removal of t h e constituents. T h e determination of t h e volume of a gas which a sulfite, using indigo as t h e indicator. Three solucertain reagent will absorb up t o the point a t which tions of potassium hydroxide, of specific gravities the gas is n o t completely removed from its mixture ~ . o z j ,1 . 0 j o and I . joo, were employed, and t h e rewith other gases is needed b y gas analysts. I t is agent w a s prepared b y adding o . 2 j g. of pyrogallol here proposed t o express this value in cc. of gas per t o I O cc. of one of these solutions. T h e oxygen t h a t cc. of reagent a n d t e r m i t t h e s p e c i f i c a b s o r b i n g p o w e r , was not absorbed under t h e arbitrary conditions of or t h e speci$c absorptiofL, of the reagent. T h e state- the experiments amounted t o I . j 6 , 0 . 8 8 a n d 2 . 9 ment of t h e specific absorption of a reagent for a gas per cent for t h e solutions in which t h e specific gravity must contain t h e name of t h e a p p a r a t u s t h a t is em- of t h e alkali was ~ . o z j ,I . Cjo a n d I . 5 0 0 , respecployed, t h e method of i t s manipulation, a n d t h e tively. From these d a t a t h e authors conclude t h a t temperature of t h e reagent, since these conditions af- t h e solution of potassium hydroxide of specific gravity fect t h e results. Also t h e volume of gas t h a t is ab- I , o j o gives t h e reagent with the highest absorbing sorbed a t a time m a y have a n effect upon t h e specific power a n d t h e y s t a t e also t h a t the pyrogallol probably absorption and for t h i s reason t h e mixture t o be em- is quickly destroyed b y t h e solution of potassium ployed in t h e determination of this value should con- hydroxide of specific gravity I . j . Wehl a n d Goth‘ tain a n amount of the gas t o be removed such a s would performed similar experiments substituting sodium 1 Gilbert’s A n n . , 74 (1823), 410. most frequently be met with, a n d this amount should 2 Liebig’s Ann.. 77 (1851). 107. tie given in stating t h e specific absorption of a reagent. 3
1
“Gasanalytische Methoden.” 4th E d . , p. 128.
4
I b i d . , 206 (ISSO), 2 5 5 . B e y . . 14 (1881). 2659.
