LITERATURE CITED
(1) Browning, L. C., Watts, J. O., ANAL. CHEM.29,24 (1957). (2) Desty, D. H., LiVapourPhase Chromatography,” p. xi, Academic Press, New York, 1957. (3) Dimbnt, Martin, Porter, P. E., Stross, F. H., ANAL. CHEM. 28, 290 (1956). (4) Hoare, M. R., Purnell, J. H., Truns. Faraday SOC.52, 222 (1956).
(5) James, A. T., Martin, A. J. P., Biochem. J . 50,679 (1952). (6) Keulemans, A. I. M., Kvantes, A., Zaal, P., Anal. Chim. Acta 13, 357 (1955). (7) Martin, A. J. P., Synge, R. L. M., Biochem. J . 35, 1358 (1941). (8) Pierotti, G. J., Deal, C. H., Derr, E. L.,Porter, P. E., J . Am. Chem. SOC. 78, 2989 (1956). (9) Porter P. E., Deal, C. H., Stross, F. H.,Zbid., 78, 2999 (1956).
(10) Rosie, D. M., Grob, R. L., ANAL. CHEM.29, 1263 (1957). (11) van Deemter, J. J., Zuiderweg, F. J., Klinkenberg, A,, Chem. Eny. Sci. 5 , 271 (1956). (12) Wiebe, A. K., J . Phys. Chem. 60, 685 (1956). RECEIVEDfor review May 6, 1958. Accepted October 24, 1958. Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, March 1958.
Applications of Chemisorption in Chromatographic Separations of Organic Isomers and Homologs JAMES
L. FORSTNER‘
and
L. B. ROGERS
Massachusetts Institute o f Technology, Cambridge, Mass.
b This investigation explored means for using chemisorption to enhance the separability of organic isomers and homologs. Most of the study dealt with the 2- and 4-nitroso-lnaphthols, used to evaluate chelation. A limited amount of work was devoted to evaluating coordination complexes using lower aliphatic amines. Results point to the usefulness of lowcapacity salts and impregnated highcapacity oxides as chromatographic sorbents.
S
and alumina, widely used in columnar adsorption chromatography, have high capacities resulting from their large surface areas. Relatively little work has been done with lower capacity oxides or salts which might provide greater specificity through chemisorption. Though deliberate use of chemisorption was reported 20 years ago (9), most applications have been reported within the last 5 years. Typical examples involve precipitation (13, 27, 28) and complexation (17, 19, 20, 26, 32, 34). Unfortunately, many factors contribute to the over-all separation (4, SS), so it is difficult t o evaluate individual contributions. The present study represents an attempt to define the role of chemisorption by determining the separability of 2- and 4-nitrosonaphthols on alumina, both before and after impregnation Kith copper(I1) chloride. The separability was measured in two ways. I n equilibrium studies, determinations were made of amounts sorbed, and the ratio of amounts of the potentially reactive sorbate to the “control” sorbate (physical sorption primarily) was calculated. This was deILICA
1 Present address, E. I. du Pont de Nemours & Co., Inc., Aiken, S. C.
fined as the sorption ratio, r . By assuming that the isotherms of two substances have the same general shape and using both the same weight of sorbent and the same initial concentration (and amount) of sorbate in two parallel determinations, one can use a ratio of the amounts sorbed to measure the separability of the sorbates (12). By selecting conditions under which the points fell on the gently sloping upper portions of the isotherm, gross changes in sorption could be detected. Additional points were obtained for promising sorbents . Comparable data were also obtained from column studies using R L values determined, where possible, by the “single-column-volume” method (32). Solutions containing 0.2 mg. per ml. were substituted for the recommended 0.01M; when the developer differed from the original solvent, one column volume of developer was used. For columns whose metal content interfered with the action of zone-locating reagents, the “break-through” method was used. Controls run by both methods agreed sufficiently well for screening purposes (12). A ratio comparable to r was calculated by dividing RL for the less reactive substance by that for the more reactive. EXPERIMENTAL
Chemicals. Eastman White Label 4-nitroso-1-naphthol LI as recrystallized from berizene. The 2-nitroso1-naphthol was synthesized from 1naphthol according t o the directions of Jung, Cardini, and Fuksman (18). Solutions of 2- and 4-nitroso-1-naphthol were prepared fresh each week, because they decomposed somewhat on standing. The n-butylamine, sec-monoamylamine, sec-monohexglamine, diethyla-
mine, and triethylamine were used as obtained from the Sharples Solvents Corp. The n-propylamine and diisopropylamine were Eastman Kodak practical grade chemicals. The aluminum oxide was Merck reagent “suitable for chromatographic adsorption.” It contained free alkali, as shown by the fact that P suspension of 3 grams in 25 ml. of distilled water produced a p H of 10.1. ilnalysis for iron (6) gave a Fe& content of 0.070%. Mallinckrodt analytical reagent silicic acid, 100 mesh, produced a p H of 4.6 when 3 grams was suspended in 25 ml. of distilled water. Hyflo SuperCel (Johns-Nansville) did not sorb nitrosonaphthols or amines and was mixed with finely powdered sorbents, to improve the flow of solvent through the chromatographic column. A suspension of 3 grams in 25 ml. of distilled mater gave a p H of 9.2. Ligroin, boiling range 90’ to 100” C., was commercial heptane from the United Fuel Gas Co. Apparatus. A Beckman Model DU quartz spectrophotometer was used for all routine measurements of the final concentrations of the naphthols, for determination of iron in aluminum, and for copper in the copper chloride-alumina sorbents. A Cary recording spectrophotometer and its log-density attachment were used to identify and determine the purity of the nitrosonaphthols. Beckman Models G and H p H meters and a Leeds & n’orthrup p H Indicator (No. 7660) were employed with glass electrodes for determination of pH. Chromatographic columns were made from 12.5-cm. lengths of borosilicate glass tubing 9 mm. in internal diameter. Columns were packed with sorbent to a height of 100 =t3 mm. for quantitative measurements. At the upper end was a 7-cm. length of tubing of 14-mm. internal diameter which held about 10 ml. of developing solvent. Procedures. SEPARATION OF SORBENTS. Silica was active as received VOL. 31, NO. 3, M A R C H 1959
365
'7
Figure 1 . Effect of moisture on sorption of 3.8 X 10-4M nitrosonaphthol solution in benzene onto anhydrous copper sulfate
0
I
I 10
0
20
I 30
TIME CF EXPOSURE
Table I.
1
.
40
1
50
Y 63
Imn
2-Nitroso-1 -naphthol, 0.500 gram 4-Nitroso-1 -naphthol, 3.00 grams
and was used without further treatment. Alumina was also highly activated as obtained and was often used directly from t h e bottle. When i t had t o be compared with aluminabase sorbents which had been deactivated and then reactivated during preparation, t h e alumina was treated in a similar manner, to obtain as nearly the same surface conditions as possible. Sorbents which consisted of inorganic salts sorbed onto the surface of silica or alumina were prepared by dissolving the salts in a n organic solvent, usually
Sorption Ratios of 2- and 4-Nitroso-1 -naphthols on Various Sorbents x / m , hlg. /G.
%2
Series 1
Sorbent SiOz
2 3 4
A1203 CuClz on A1203
5
CuC12on A1208
Treatment Sorbed 2A. High Capacity Sorbentsa Direct from bottle 10.8 17.4 25.8 12.3 41.0 10.1 b 12.4 58.0 36.3 54.3 41.6 58.0 b 8.9 40.0 29.5 40.3 29.9 41.3
6
CUSOC
i
cuso4
8
CUO
B. Low Capacity Anhydrous, (heated t o 450" C.) Pentahydrate, (heated to 450' C.) Dried at 250' C.
9
Fez03
Dried a t 250" C.
-
Sorbentsd 22,O 1,49 54.2 1.54 46.9 1.89 10.6 40.0 7.8 35.0
0.21 0.20 3.05 2.ii
r
418.6 15.1 11.7 42.1 39.7 32.3 9.01 9.75 18.1
0 0 0 1 1 1 4 4 2
94 82 86 38 37 79 44 13 28
366
ANALYTICAL CHEMISTRY
EQUILIBRIUM
0.068 0.072 0.104
22 1 21 2 18 2
0.059 0 065 1.236 1.153
3 3 2 2
6 1 46 41
JfEASUREMENTS
OF
SORPTION.Isotherms were measured using a constant initial concentration of sorbate and different weights of sorbent, in order to compare isotherms by means of sorption ratios. Equilibrations were carried out in a n air-conditioned room whose temperature usually did not vary from the mean of 22 ' C. by more than + l o C. Solutions containing measured amounts of sorbent and sorbate were shaken for 0.5 hour and analyzed after the sorbent had settled. The equilibrium concentration of naphthol was determined by extracting a portion of the supernate with 0.625M ammonium hydroxide and analyzing it with the Beckman spectrophotometer. Blanks were run daily. The values for the resulting sorption ratios varied by less than 5% in a series of tests involving three different sorbents.
DYNAMIC ,MEASUREMENTS OF SORP-
COLUMNS. Chromatographic columns were prepared by adding the dry sorbent in small increments. Many of the finely divided salts were mixed with a filter aid, Hyflo Super-Cel (SC), to improve flow characteristics. Invisible zones were located with streaking reagents. Columns that could not be extruded were cut out as small segments to which the streaking reagent was applied (on a spot-test plate). To locate the zones, ammonia vapor, or occasionally 0.2M sodium hydroxide, was employed to convert the naphthols to the yellow anionic form. The universal p H indicator (55) turned green in the presence of aliphatic amines on most sorbents. On copper sulfate, however, it was red in the absence of amines and yellow in their presence. Alkaline potassium permanganate, recommended by LeRosen et al. (26) for oxidizable materials, turned green in the presence of some amines, but did not work on copper-containing sorbents. Three new color reactions, not previously suggested as streak reagents, were employed when metal cations, used in some of the sorbents, interfered: p-Dimethylaminobenzaldehyde, in glacial acetic acid (IO) gave a n intense yellow color in the presence TION ON
C. Alkaline Earth Carbonatesd 35.7 16.7 5.78 MgC03 (hlerck) As recd. 29 30 65.9 15.7 5.25 11 CaC03 (Merck) -4s recd. 25.6 0.51 0.059 87 25.4 0.51 0 057 9 0 0.053 23.8 0.47 89 12 CaC03 (Mallinc- As recd. 0 026 8.3 0.17 66 krodt) 38.1 3.42 13 SrC03 (Mallinc- As recd. 0.50 69 krodt) 0.44 88.0 2.84 6 4 14 BaC03 (Mallinc- As recd. 0.039 7.5 0.71 18 4 krodt) 0 045 14 4 32.6 0.65 a 5.0 mg. of naphthol in 30 ml. of benzene. Ignited, washed with water then acetone, dried a t 125' C., and exposed to 50% humidity at 22' C.for 30 days. Ignited, washed Rith water, ignited. 2.0 mg. of naphthol in 30 ml. of benzene. 10
acetone, and adding silica or alumina. Successive portions of the solution were used until the sorbent appeared to be saturated; then it was dried and heated to about 450' C. The sorbent was then washed successively with acetone and water to remove any unfixed salt, and reheated to 450' C. for strong activation, or dried a t lower temperatures t o form less active sorbents. The amount of inorganic salt on the surface of the sorbent could be increased by resaturating the surface after the sorbent had been heated to 450' C. Pure salts were also used as sorbents. Salts 15hich contained no water of hydration were dried a t 120' C. for 12 hours or more before use; hydrated salts were heated to drive off the water; copper phosphate and iron(II1) sulfate were heated to 450' C. When the sorbents had to be ground to reduce the particle size after heating, the drying process was repeated.
of primary aromatic amines; sodium nitroprusside, in 10% acetaldehyde formed a deep blue to violet color in the presence of some amines (11); and copper(I1) chloride, in butanol gave a deep blue color in the presence of some amines. Ratios of R L ~ a l u e scould usually be determined to within 5'%, the same limit as for equilibrium measurements of sorption. Day-to-day and columnto-column variations are included. COPPERL % s . 4 ~ ~ One-half - ~ ~ ~ . gram of copper chloride-alumina sorbent was fused ivith 5 grams of sodium carbonate. The melt was dissolved in dilute sulfuric arid, and the solution digested to coagulate silica. Copper was separated as tlir sulfide and determined spectrophotometrically as the ammonia complex. DETERJlIShTIOSS OF SURFACE ACIDITY. The relative acidity or basicityof thesurface of an alumina sorbent was estimated by stirring a sample vigorously in 25 ml. of distilled water for 2 minutes, allowing the suspension to settle (about a minute), and measuring the pH of the supernatant liquid. Amounts smaller than 2 grams produced rapid changes in p H with change in weight; from 2 to 8 grams produced a change of less than 0.2 pH unit. Therefor?, 3 grams were employed in all tests. RESULTS
Preliminary Studies.
II. R L Values for 2- and 4-Nitroso-1-naphthol on Various Sorbents Using 0.2 M g . of Sorbate in 1 .O MI. of Benzene Sorbent Developer 2 R ~ 4 R ~ ~ R L / ~ r(Benzene) RL A. High Capacity Sorbents Used without Super-Cel 0 04 0 10 2 5 1 8 A1203 (from bottle) Methanol 5 9 1 8 107, water" 0 07 0 41 2 3 CuC12on & 0 3 , ign. 10% water" 0 0 1 0 2 3 Water 0 0 1 0 c u s o 4 on & 0 3 , ign. Methanol 0.0 1.0 ... ... mater 0.0 1.0 ... ... C;by03)z 107' viater" 0.0 0.4 ... ... on & 0 3 , ign. Water 0.0 1.0 ... .._. Ni (S O 3 2) Methanol 0.0 1.0 ... ... FeC13on A1203, ign. Water 0.0 1.o ... ... CuC12on SiOp, ign. Lower Capacity Sorbents 0.7 0.16 2.3 ... Benzene ?VIgSoc -f SC, 1 : 1 0.16 0.50 3.0 ... Benzene Fez(SO4) + SC, 1 : 1 0.05 0.20 4.0 ... Benzene CU3(PO4)+ SC, 1: 1 0.03 0.30 10.0 22 Benzene CUSO4 0.06 0.47 7.8 b GUS04 SC, 1:l Benzene 0.05 0.02 0.4 Si02 + SC, 2: 1 Benzene 0.03 0.6 d 1:l Benzene 0.05 0.06 0.7 d 1:4 Benzene 0.09 C. Alkaline Earth Carbonates (All 1:1 with SC) 4.0 2.9 0.01 0.04 lfgcoa 9.0 0.80 2.0 0.41 CaC03,hlerck 0. 34 0 82 2.4 6.6 -~ CaC03, Mallinckrodt 7.5 6.9 0.02 0.G SrCO3 10 8 14.0 0.05 0.54 B3C03 a 10% water in methanol. b Value expected to be lower than on pure CuS04 (indicating poorer separation) 3s a result of decreasing effective distribution ratio with inert SC. c Value on pure Si02 was 0.9. Value expected t o be increasingly larger (indicating a poorer separation) than on pure Si02 due t o greater dilution with SC.
Table
+
Determina-
R L Values for Amines on Various Sorbents Using Benzene as a Developer (1.0 mg. of amine in 10 ml. of benzene)
Table Ill.
n-Propyl ... n-Butyl 1.0 1 .o sec-bfonoamyl 1.O sec-Monohesyl 1.o Diethyl Diisopropyl 1.0 Triethyl 1.0 Aniline 1.0 a Appros. 10% AgS03, 407,
... 0.30 0.oc 0.78 1.0 0.56 1.0 0.62 0.71 0.36 0.60 0.95 0.40 0.86 0.90 0.61 CaC03,50% SC by volume.
Table IV.
0.07
0.22
...
0.05. 0.04 0 . 05c 0 ,04c ... 0.07 0.06 0.26
...
...
...
0.07
0.32 0.47
...
...
0.08 0.08 0.32
0.73
... * Strongly activated sorbents.
0.22 0.18
...
0.12 ...
0.15
...
... 0.12 ... ... ... 0.22 0.13 0.28 0.23 0.38 0.34 Deep blue zone at top of column. ...
0.20 0.24 0.28 0.39 0.53
RL Values for Amines on Various Sorbents Using Different Developers (1.0 mg. of amine in 1.0 ml. of benzene)
C3C03 Amine n-Propyl n-Butyl sec-llonoamy 1
+ Sc
CUSO4
Ligr.
CaHs
1.0
.,.
1.0
...
1.0 1.0
+ SC
Ligr.
COHO
0.0
...
0.0
...
0.0 0.56
Sorbent Si02 SCo Developer C6H6 EtOAc MeOH
C&,
0.06
(0.05
+
... ...
0.09
0.27
...
... ...
...
sec-Monohesyl
1.0
1.0
0.59
0.62
0.07
0.12
0.40
Diethyl Diisopropl-1
1.0 1.0
1.0 1.0
0.18 0.72
0.36 0.60
0.06 0.08
0.08 0.11
0.22 0.30
Triethyl
1.0
1.0
0.35
0.40
0.08
...
...
Aniline
1.0
1.0
0.71
0.90
0.32
...
...
a
Strongly activated sorbents.
CuCIp on Si02
(0,04
(0.04 (. ,
.
(0.05
,\ . .
-+ SCajb
EtOAc
hleOH
(0.15
...
(0.38 (0.18 ...
...
...
(. . .
,
(0.04
(0.04
(. . .
0.08
...
(0.47 (0.20
...
(0:07 (0.04 (0.06
(. . .
(.. .
(0.09 (0,23
(.
(.
(0.18 (0.37 (. . .
..
(0.26 (. . .
..
(. . . (,. .
(,.
(. .
.
.
Two different batches in different states of activation.
VOL. 31, NO. 3, MARCH 1959
367
-1F-=-z
12
O
l
60
-
0.4
01 0
I
I
I
.O.l
FINAL CONCENTRATION OF
I --I 0.2 03 NITROSONAPHTHOL(Millimcls/liler)
cb
0.4
Figurd 2. Sorption isotherms of 2- and 4-nitroso1 -naphthol from benzene onto anhydrous copper sulfate Initial naphthol concentration, 3.8
0 13
X 1 0-4M
2-Nitrosa-1 -naphthol 4-Nitroso-1 -naphthol
tions of both sorption and RL ratios were run on a large number of salts and oxides in preliminary, exploratory work. One group of results, involving possible chelation, is shown in Tables I and 11. Another group, involving possible complex formation, appears in Tables I11 and IV. There are several attractive possibilities. However, as favorable ratios of r or RL values were not in themselves sufficient to prove that chemisorption was playing an important role, experiments were run in which alumina and copper(I1) chloride-impregnated alumina were treated similarly before being used in parallel sorption studies of the 2- and 4-nitrosonaphthols. Before impregnated solvents are discussed in detail, several points in Table I require comment. Salts such as copper(I1) sulfate generally had higher r values but smaller capacities than alumina and silica. The only sorbent in Table I to show stronger sorption of the 4- than the 2isomer was silica, where dipole moment plays the dominant part (83). Thus, chelation may have occurred with the alkaline earth cations (23) and with alumina (SO). Additional support for this view is gained indirectly from the behavior of the nitrophenols, whose chelating tendencies, like those of the nitronaphthols (24), are probably very low. The nitro compounds, unlike the nitroso, generally gave r values less than unity (Table V). Differences in surface acidity of the alumina led to significant changes in r, as indicated by the parenthetical values for samples 3 and 5. Attempts to use cobalt(I1) on alumina resulted in partial (irreversible) dissolution of the cobalt, making quantitative studies useless. Reproducibility of sorption ratios for anhydrous copper(I1) sulfate was initially very poor, because of variations in the pickup of small amounts of water. Figure 1 shows copper sulfate picked
368
ANALYTICAL CHEMISTRY
1
I I I I I I 02 04 06 08 FINAL COkCENTRAT13N Cf NITROSONAPHTHOL i M ~ l ~ m o l s i l ~ t e r l
Figure 3. Sorption isotherms of 2-nitroso-1 -naphthol onto sorbents in different states of activation Initial naphthol concentration, 9
0
A A 0
X 10
Alumina, water washed, activated b y washing with acetone and drying a t 125’ C. Alumina, deactivated by exposure to 50% relative humidity a t 2 2 ’ C. Copper chloride-alumina, activated Copper chloride-alumina, deactivated
up from room air (reproducibly), 0.1% by weight of water per minute. Small amounts of water decreased chemisorption of the 2- isomer, and increased (physical) sorption of the 4- isomer. All these points emphasize the need for caution in interpreting results. Copper-Impregnated Alumina. The shape of the isotherm can be used qualitatively to distinguish between chemisorption and physical sorption. Figure 2 provides a n excellent illustration of a Langmuir isotherm (21) whose upper portion is flat because of saturation of the surface. I n contrast, the curves for pure alumina (Figure 3) follow a typical Freundlich isotherm, showing the decided slope generally attributed to multilayer phpsical sorption. Impregnation of the alumina, particularly of the deactivated sample, led to flattening of the upper portion. Further support of chemisorption is found in the calculation of surface area for copper-containing samples from the amount of 2- isomer sorbed. When atomic radii (26) were used to calculate an area of 35 to 200 sq. A. for the 2- isomer in “tail-on” and “flat” positions, the results for the surface area of each sample fell on both sides of the value reported for a similar sample on the basis of nitrogen and n-butane sorption (3-5). This agreement also indicates saturation of surface copper with the 2- isomer. Additional evidence for chemisorption is found in the striking qualitative differences in behavior of the two isomers on columns. Under ideal conditions, r values and Rr, ratios are directly
related (7, 14, 15). In this study, however, r represents measurements on the upper plateau, n-hile RL values reflect behavior on the steeply ascending portions of the isotherms. Satisfactory correlation between rate of movement on a column and the isotherm was demonstrated, as well as qualitative agreement of relative magnitudes of r and RL ratios (18). I n water the 4- isomer remained virtually in the solvent front (Table VI). The 2- isomer was completely immobilized and could be removed from copper-impregnated alumina only by aqueous acid or base. Even greater difficulty was encountered in recoveries from iron- and nickel-impregnated columns (12)* To evaluate the variation attributable t o differences in surface acidity, one series of pure alumina sorbents and another of copper chloride-alumina sorbents were prepared by washing a large quantity of the sorbent with dilute hydrochloric acid or sodium hydroxide and then rinsing several times with distilled water. When the pH of several successive washings differed by less than 0.1 p H unit, a portion of the sorbent was removed, dried, and ignited at 450” C. The remainder of the wet sorbent was treated again with acid (or base) and another small portion was removed. This process was repeated a number of times. After each portion had been activated by ignition, its surface acidity was determined by the procedure described earlier. Table VI1 shows that for a sorbent of given surface acidity, the value for
the sorption ratio was independent of the presence of copper chloride, except possibly near p H 4. Significant differences in T and RL are apparent near p H 5.0 (Table VI). I n addition to pH, the activity of the alumina is very important. I n Table I, the effect of impregnation is greater for the less active samples 2 and 4 than for 3 and 5. Russell and Cochran (89) have shown that maximum surface area and activity are obtained on heating alumina to 350' to 450' C. After deactivation by contact with mater, samples 3 and 5 were heated to give maximum activity, whereas samples 2 and 4 were washed with acetone and dried a t a moderate temperature. The results suggest that partial deactivation with water satisfied part of the physical sorption and thereby enhanced the relative contribution of chemisorption. DISCUSSION
.
The present study shons that chemisorption can be used to advantage in increasing the selectivity of chromatographic separations, where the accompanying physical sorption is weak. This conclusion parallels the statement by Hildebrand and Rotariu (16), that more efficient separations should be obtained in solvent extraction using relatively poor solvents, because good solvents tend t o swamp the differences between the solutes. Increased selectivity was accompanied by a decrease in the capacity of the sorbent, requiring use of smaller amounts of sorbate. The use of strong sorbents such as alumina and silica, impregnated with salts capable of chemisorption, permits one to compromise the limits of selectivity and capacity represented by the pure compounds alone. Sorbents having intermediate properties can readily be prepared. The primary advantage offered by impregnated sorbents over simple mixtures of the pure compounds is that impregnated sorbents can be used under conditions in 11-hich the salts themselves might be soluble in the eluting solution. Thus, copper(I1) chloride can be used by itself with solutions of benzene, but must be retained by an insoluble material such as alumina with a n aqueous solution. A combination of the present approach with that of Dickey (8) for modifying the physical structure of the sorbent might prove fruitful. This study was concerned primarily n i t h copper(I1) chloride as an impregnating agent. Brief studies using pure anhydrous copper(I1) chloride or nitrate indicated results similar to those for sulfate in Table I. The pure chloride and nitrate are not practical sorbents, because they are more soluble
Brief re-examination of the data fothe amines reveals interesting possibilities. Using benzene as a developer, the best separation within a homologous series took place on sorbents containing copper and silver. Cobalt pro-
than the sulfate in esters and alcohols which might be used as developers. Their similarity t o the sulfate in sorption behavior indicated t h a t the anion exerted only a minor influence on the process.
Table V.
Sorption Ratios for 0 - and p-Nitrophenols on Various Sorbents from 35 MI. of Benzene Containing 7.1 Mg. of Sorbate
Sorbent CuS04, anhyd.
Treatment' Direct from bottle
COzo3
1
COzo3
Treatedqithexcess
yo para 2.9 0 5 0.7
CoClZ,ign. 1 41.2 1 22.2 A1203, acidic CoC12on A1203 2 42.8 CoC12on Alz03 2 42.8 CoCl? on A1203 3 44.7 (5 treatment 8) C O ( K O ~on ) ~&03 2 71.0 Co(h'Os)? on Al203 3 62.3 (3 treatments) CuClZon r1lz03 2 24.8 1, sorbent ignited just to dull red. 2, 0 Treatments. tion, ignited. 3, sorbent resaturated after ignition.
A1203
Table VI.
T
0.030 0 054 0.0316
0 25 17 13
25.9 15.2 22.0 22.0 7.6
14.8 6.13 12.3 12.3 3 35
0.58 0.40 0.56 0.56 0.44
24.7 21.7
20.2 14.4
0.82 0.67
16.9
9.76
0.57
sorbent saturated with salt solu-
Effect of Copper Content on Sorption Ratios and RL Values of Nitrosonaphthols on Copper Chloride-Alumina ~R ,- -
MeOH Developer
HzO Developer
r
2
4
2
1.59 1.92
...
...
0:O
0.39
-0.1
1.0
0.0
0 23
&YG,
Sample &Os J
I
CuCl? on A1903 P
pH
x/m, M d G . Sorbent 2 4
5.4 5.0
0.0 0.0
46.3 39.1
5.8 4.7 5.0 4.7
4.4 16.P 24.3 33.8
49.5 43.8 56.2 53.4
29.0 20.4
28.8 17.7 21.0 S 18.6 a One saturation treatment (see Preparation of
2
x/m, Mg./G. Ortho
Para 0.12 0 032 0.023
1.72 2.48 2.68 2.87
.. . ...
0.0
...
...
0.52
4
0 0
1.0
... ...
...
... 0.0
1.0
Sorbents).
Table VII. Effect of Surface Acidity on Sorption Ratio for Nitrosonaphthols Sorbed from Benzene on Alumina and Copper Chloride-Alumina (5.0 mg. compound in 30 ml. benzene, 35.5 0.5 mg. sorbent) x / m , Rlg./G. Sorbent Sample PH 2 4 r A120A 10.5 58.0 32.3 1.i9 B 10.0 55.8 35.7 1.56 C 9.9+ 55.6 32.5 1.71 D 9.9 49.6 31.6 1.57 E 9.8 50.5 30.5 1.65 G 9.7 54.6 33.3 1.64 RI 8.8 55.9 36.1 1.55 H 6.9 48.4 27.7 1.75 J 5.4 46.3 29.0 1.59 I 5.0 39.1 20.4 1.91 K 4.0+ 39.5 20.1 1.96 L 4.037.8 18.6 2.03 CuClp on &OaU G 10.1 59.3 35.2 1.68 F 9.5 55.6 33.4 1.67 E 7.5 51.8 32.8 1.58 D 7.5 51.1 30.3 1.68 C 6.3 51.1 30.6 1.67 B 5.2 47.2 26.2 1.80 18.1 2.28 A 4.3 41.3 26 mg. Cu per g. sorbent.
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vided better separations among mono-, di-, and tri-substituted amines. Copper fixed the lower members of the mono-substituted amines, while silver did not, in agreement with the work of Bjerrum (1, f?),who showed that the first stability constant for copper(I1) was larger than that for silver. Bjerrum also showed that the constants for these two elements are generally larger than that for cobalt(I1). In Table I11 the RL values indicate that cobalt forms more stable complexes than silver. This anomaly may be due in part to the fact that no determination was made of the upper limits for the amounts of sorbate that could be used without saturating the sorbent on the first part of the column, or the presence of different amounts of chemically reactive substances on the impregnated sorbents. It should be possible to correlate values of RL with stability constants either for the first coordination step or the over-all complex involving each amine in a series in combination with a single metal cation. The constants for silver-amine complexes in benzene differ not only in magnitude, but possibly also in order from those in water. Thus the stability values for the mono-alkyl amines do not differ greatly in magnitude in water ( I ) , whereas the RL values in benzene for m-propyland n-butylamines on silver nitrate were different. More complete studies of such systems as those in Tables VI1 and VI11 would be of both theoretical and practical interest. Evaluation of the following equilibria is required: sorption of the salt used for impregnating the sorbent (or,
in the case of a pure salt, its solubilit.y), stability of the chemical entity formed by the salt and the sorbate, competitive equilibria involving the solvent, and rates of the reactions, particularly those involving reactions between salt and sorbate. LITERATURE CITED
(1) . . Bjerrum,. J.,, Chem.
Revs. 46. 381
(1950). (2) Bjerrum, J., “Metal Amine Formation in A ueous Solution,” P. Haase and Son, &openhagen, 1941. (3) Brunauer, S., Emmett, P. H., J. Am. Chem. SOC.59, 2682 (1937). (4) Cassidy, H. G., “Adsorption and Chromatography,” pp. 178-80, Interscience, Xew York, 1951. (5) Deitz, V. R., Ann. N . Y . Acad. Sci. 49. 315 11948). - ~ (6, DeSesa, hl. A., Rogers, L. B., Anal. Chim. Acta 6,534 (1952). (7) . . DeVault, D., J . Am. Chem. SOC. 65, 532 (1943). ‘ (8) Dickey, F. H., J . Phys. Chem. 59, 695 il9.55). (9) Erlenmeyer, H., Dahn, H., Helv. Chim. Acta 22, 1369 (1939). (10) Feigl, F., “Quantitative Analysis by Spot Tests,” p. 307, Nordemann, New York, 1939. (11) Ibdd., p. 317. (12) Forstner, J. L., Ph.D. thesis, Massachusetts Institute of Technology, 1952. (13) Gapon, E. K.,Belen’kaya, I. M., Kolloid. Zhur. 14, 323 (1952). (14) Gliickauf, E., Nature 156, 748 (1945). (15) Ibid., 160, 301 (1947). 116) Hildebrand. J. H.. Rotariu.‘ G. J.. ANAL.CHEW24, 770 (1952). (17) James, T. H., Vanselow, W., J . Am. Chem. SOC.73, 5617 (1951); 74, 2374 (1952). (18) Jung, W.,Cardini, C. E., Fuksman, hl., Anales asoc. qufm. arg. 31, 122 (1943). (19) Jura, J., Grota, L. Hildebrand, J. H., 118th Meeting, AkS, Chicago, Ill., September 1950. I
\
\--
- I
- - - I
~
(20) Khym, J. X., Zill, L. P., J . Ani. Chem. SOC.74, 2090 (1952). (21) Langmuir, I., Phys. Rev. 6 , i 9 (1915). (22) LeRosen, A. L., Vonaghan, P. H., Rivet, C. A., Smith, E. D., ANAL. CHEM.22,809 (1950). (23) hlartell, A. E., Calvin, &I.,“Chemistry of Metal Chelate Compounds,” Appendix I, Prentice-Hall, Xew York, 1952. (24) Mayr, C., Prodinger, W.,Z. anal. Chem. 117, 334 (1939). (25) O’Connor, D. J., Bryant, F., Nature 170,84 (1952). (26) Pauling, L., “Sature of the Chemical Bond,” Cornel1 University Press, Ithaca, N. Y., 1940. (27) Reichl, E. R., Loffler, J. E., Mikrochim. Acta 1954, 226. (28) Robinson, G., Discussions Faraday SOC.7. 195 11949). (29) Russell, A. ’S.,Cochran, C. K., Ind. Ens. Chem. 42, 1336 (1950). (30) Sacconi, L., Dzscussions Faraday SOC.7, 173 (1949). 1311 Samuelson. 0.. Z. Elektrochem. 57. 207 11953). (32) Smith,’ E. D., LeRosen, A. L., ANAL. CHEM. 23, 732 (1951). (33) Strain, H. H., “Chromatographic Adsorption Analysis,” p. 93, Interscience, New York, 19+2. (34) Rielund, T., Fischer, E., Naturwissenscha ten 35, 29 (1948). 1351 Willardf H. H.. Merritt. L. L.. Jr.. ’ Dean, J. A,,“Ins&umental’Metho’ds of Analysis,” p. 140, Van Kostrand, New York, 1948. I
,
RECEIVED for reviea December 19, 1957. Accepted October 13, 1958. Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Pittsburgh, Pa., March 1953. Taken from a thesis submitted by James L. Forstner in partial fulfillment of the requirements for the degree of doctor of philosophy, Massachusetts Institute of Technology, Cambridge, Mass., December 1952. Work supported in part by the Atomic Energy Commission under contract .;1T(30-1)-905
Improved Spent Sulfite Liquor Determination by the Nitrosolignin Method OTTO GOLDSCHMID and L. FRANK MARANVILLE Olympic Research Division, Rayonier lnc., Shelton, Wash.
b The Pearl and Benson determination of spent sulfite liquor with a photoelectric colorimeter has been improved by a filter combination which gives more nearly monochromatic light of about 430 mp, This eliminates the undesirable light absorption due to the nitrite reagent and improves both sensitivity and reproducibility. Interference of certain materials such as water-soluble extractives from bark and wood can b e reduced but not eliminated by the use of an alkaline blank solution of the water sample of 370
ANALYTICAL CHEMISTRY
the same pH as the reagent-treated sample. Agreement or disagreement between the results obtained using both a neutral and the alkaline blank indicates the probable absence or presence of substances other than spent sulfite liquor.
T
HE determination of spent sulfite liquor (SSL) in sea water by the nitrosolignin color reaction was originally developed by Pearl and Benson (5) as a visual colorimetric method. Nitrite and acetic acid were added to
the water sample in a Sessler tube; after addition of ammonia to enhance the color by conversion of the nitrosolignin formed into the quinoidal salt form, the color was compared visually with that of similarly treated known spent liquor dilutions or platinumcobalt standard solutions. ilnderson ( I ) , who investigated the effects of reagent concentration, pH, and temperature on the rate of nitrosolignin color formation in detail and established optimum conditions for the formation of a stable, reproducible
