Determination of Carbon Monoxide in the Orsat Gas-Analysis Apparatus with Copper(1) Sulfate-P-Na phthol

Sir: =Ilthough the use of copper(1) sulfate-/%naphthol for determining car- bon monoxide was c escribed by Lebeau and Bedel (2) as long ago as 1924, i t seems to have been far underrated as an Orsat reageni,. Many writers- e.g., Vogel (3)-have claimed it to be slon in reacting or to have a low absorp- tion capacity, and it is certainly diffi- cult and time consuming to prepare using the method given by Lebeau and Bedel. A recent pzper on "Advances in the Orsat Xnalyser" (1 ) even ig- nores the possibility of using this rea- gent for carbon monoxide and advocates instead the use of ammoniacal copper(1) chloride, no less than three absorption vessels being used in tandem to ensure quantitative absorption.

However, n e have nom developed a method of preimation by which copper(1) sulfate-[kxq?hthol of high reactivity can be prepared in little over 1 hour. We have also noted a feiv simple precautions which need to be taken to ensure that the fresh reagent is reactive and rpmains so. Ignorance of these precautiorts ha. undoubtedli been the cause of ihe poor reputation of this reagent.

Figure 2. Effect of reaction tem- perature on reactivity of copper(1) sulfate-/?+a phthol

t o a boil. ,Idd a near-boiling solu- tion of 60 grams of A.R. glucose in 400 ml. of water. Boil t h e mixture for 3 minutes. This should result in the precipitation of bright, car- mine-red copper(1) oxide. Allow this precipitate to settle, wash with water several times by decantation, then filter on a Buchner funnel, again wash with water and then Kith alcohol, and dry by sucking air through it. Yote that to obtain a high yield of copper(1) oxide uncontaminated with copper (11) oxide, i t is essential to use chemicals of - k R .

EXPERIMENTAL

Method of Preparation. Dissolve 100 grams of A.11. copper(I1) ace- t a t e in water and bring the solution

grade. .Add 20 grams of the copper(1)

oxide to 25 grams of X.R. 6-nauhthol

I 5 i 0 15 20 25

m.s of CO absor!ied per rnl of reogent

Figure 1. Effect of continued ab- sorption of carbon monoxide on re- activity of ammoniigcal copper(1) chlo- ride and copper(1:' sulfate-/?-naphthol

a, 0-0. Ammoniacal copper(1) chloride

b, A-A. Copper(1) sulfate-6-naphthol at

c, 0-0. Copptw(1) sulfate-6-naphthol

at a reaction temperature of 20' C.

a reaction temperature of 20' C.

at a reaction temperature of 40' C.

in a porcelain mortar and grind k i th a pestle until the copper(1) oxide become< incorporated onto the surface of the p- naphthol (this should take only a min- ute or two). Remove this mixture from the mortar and place in the mortar 225 ml. of 95% sulfuric acid. .idd the copper(1) oxide mixture a little at a time by sprinkling i t onto the acid surface, and grind each addition until virtually completely disqoh-ed (the reaction of the mixture n ith the sulfuric acid is highly exothermic and unless i t is added a little a t a time the heat gener- ated will cause the copper(1) oxide to decompose). Finally, when all the mix- ture is virtually dissolved, filter through glass wool and store in a stoppered bottle.

Testing Procedure. The follow- ing s tandard procedure for testing reagent reactivity was adopted for all tests. A 100-ml. sample of s tand- a rd gas consisting of 34% carbon monoxide and 66y0 nitrogen was passed once through a 220-ml. sample of the reagent in a bubbler-type ab-

sorption vessel. The number of mil- liliters of carbon monoxide absorbed from the gas was taken as the reactivity. Different batches of the reagent which had been treated in the same way were found to have reactivities no further apart than 2 ml.

Tests were carried out to determine the effects on reagent reactivity of con- tinued absorption, reaction temperature, storage time a t various temperatures, and contamination with nater. The reactivity and absorption capacity of standard ammoniacal copper(1) chlo- ride, the usual Orsat reagent for carbon monoxide, were also determined.

RESULTS AND DISCUSSION

From tlie results of these tests! as shown in Figures 1-4, the following conclusions may be drawn :

The reagent has an outstanding ab- sorption capacity (Figure 1). It is extremely reactive vhen warm, and even at temperatures as lon- as 8" C. its reactivity is quite satisfactory (Fig- ure 2). ht ordinary room temperature the reagent is much superior t'o standard ammoniacal copper(1) chloride in both reactivity and absorption capacity (Fig- ure 1). Incidentally, copper( I) sulfate- p-naphthol which had absorbed 18 times its own volume of carbon monox- ide was st,ill absorbing it quantit'atively, cvhereas the gas in equilibrium n-ith aiiinioniacal copper(1) chloride which

a i251 I 1 I I 1 'C .-

Storage time , days

Figure 3. Effect of continued storage on reactivity of copper(I) sulfate+- naphthol

All reactivities determined in the range 22' to 26' C.

a. Stared at 40" C., b W stored in

b. Stored a t 22' C., A-A stored in

c. Stored at 5' C., 0-0 stored in

darkness, 0--0 exposed to light.

darkness, A-A exposed to light

darkness

VOI. 35, NO. 9, AUGUST 1963 1315

had absorbed only once its own volume of carbon monoxide contained 8% of carbon monoxide.

The reagent slon-ly deteriorates on standing and should be stored in as cool a place as possible to reduce this to a minimum. The storage stability was not affected by exposure to light (Figure 3). Care should be taken to prevent n ater or confining fluid from contaminating the reagent, as this cause- a marked deterioration in re- agent reactivity. Figure 4 shows only part of this effect; on standing over- night, the reagent left from the last test shown in Figure 4 contained so much sediment that it became almost solid, and could not be tested further.

Finally, when air was bubbled through the reagent, it absorbed 0.2 ml. of o\ygcn per pass. Therefore i t should lie -tored only in stoppered bot-

Effect of Tem perature

1

- '0 10 20 30 40 5 0

Water addition, % of origiML voiume

Figure 4. Effect of contamination whit water on reactivity of copper(I1 sulfate- P-naphthol

tles; or, if stored in an absorption vessel in the Orsat apparatus, any surface exposed to the atmosphere should be protected by a layer of kerosine previ- ously washed with concentrated sulfuric acid.

LITERATURE CITED

(1) Bracht, G., Brennstofl-Chem. 42, 123 (1961).

( 2 ) Lebeau, P., Bedel, C., Compt. Rend. 179, 108 (1924).

(3) Vogel, A. I., "A Text-Book of Quan- titative Inorganic Analysis," Longmans, Green 8: Co., London, 1939.

Ross STEWART D. G. EVAKS

Brown Coal Research Laboratory University of Melbourne Parkville N.2. Victoria, Australia

and Time of Heating on the Carbazole Reaction of Uronic Acids and Acid Mucopolysaccharides

SIR: Earlier work (2-4, 6) on the carbazole reaction of hexuronic acids suggested that each uronic acid upon heating with sulfuric acid reacts with different intensities of color. More re- cent studieq (5) observed a similar re- sponse it11 anthrone and indicated the possibility of differentiating uronic acids and uronic acid-containing mucopoly- saccharides (RIPS) in mixtures by means of reactions at controlled tem- peratures. The adrantages of ob- serving the same thermal variations with the more specific carbazole reaction irarranted still further investigation. Hence, a -ysteniatic study was made of -ewral uronic acids and LIPS a t various temperature. and for various heating periods.

EXPERIMENTAL

Materials. UROh-IC -4CIDS. D- Crlucuroiiic and D-galacturonic acids, purchased from Corn Products Re- fining Co., Yew York, N . Y . , and from 1Iniin Research Laboratories, Inc.. S e w l o r l i . S. Y., were good com- iiiercial samples and were used without liurification. The barium salt of D- iiiannuroiiic acid obtained from Bios Laboratories, Inc., New York, N. Y., \\-as converted into the free acid by passing it over Doiyex 50 H+. 1,2-0- iqopropylidene-Iriduronolactone was a gift from li. L. Jt701from, University of Ohio. It was hydrolyzed to the free acid by treatment with a n aqueous solution of Amberlite IR-120 Hf at 100' C. for 1 hour. The concentration of the solutions of D-glucuronic, D-

mannuronic, and L-iduronic acids used in all of the experiments was 50 pg. per ml., whereas that of the solution of D-galacturonic acid was 25 fig. per ml.

dium heparin (143 USP units per mg.) was obtained from the Upjohn Co. Chondroitin sulfate B and hyaluronic acid were gifts from J. A. Cifonelli, University of Chicago. These YIPS

A C I D hIUCOPOLYSACCHARIDES. S O -

and others mere available in the lab- oratory from other investigations after having been obtained by extensive electrophoretic and chromatographic techniques. The concentration of the solutions of the hIPS was 100 pg. per ml.

Procedure. The analyses were car- ried out essentially as suggested by Dische (2 ) with the slight modifications noted below-. Concentrated sulfuric

0.5 4'

y 0 . L f Z d ' l a R 2 0.61

.O - 0.5 1 / Gal

Man

IO ' 2 0 ' 40 5 5 70 85 i o ~ ' l o 20 ' 40 5'5 70 8 5 Id0 HEATING TIME, MINUTES

Figure 1 . Intensity of carbazole color of hexuronic acids (D-glucuronic 0--0; D-galacturonic 0-0; 1-iduronic A---A; and D-mannuronic A-A) following digestion with sulfuric acid at various temperatures and for various periods of heating

13 16 ANALYTICAL CHEMISTRY