INDLTSTRIAL A N D ENGYNBEMNG CHEMISTRY
August, 1923
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Contributions t o Chemistry of Wood Cellulose’ 111--The Acetolysis Reaction Applied to Cellulose Isolated from Commercial Species of Wood By Louis E. Wise and Walter C. Russell LABORATORIES OF THE NEWYORK STATE COLLEGE OF FORESTRY AND
HE importanceof fun-
T
THE
CHEMICAL DEPARTMENT OF SYRACUSE UNIVERSITY,
This is a continuation of the study of the chemical properties of
SYRACUSE,
N. Y.
MATERIALS
Cellulose was isolated damental data relatwood cellulose as compared with those of cotton cellulose. Cellulose ing to the chemistry from the following species: isolated by the chlorination method from a number of commercial Balsam fir (Abies balsamea), of wood cellulose has been conifcrs and hardwoods was subjected to cold alkaline treatment. hemlock (Tsuga canadenpreviously emphasized.* If The a-celluloses thus obtained, when acetolyzed under carefully such data can be obtained, sis), and red spruce (Picea controlled conditions, yielded appreciable amounts of cellobiose rubens)-all of which are new avenues in industrial octa-acetaie, which varied from 24 to 33 per cent of the theoretical imported raw materials in research, which hitherto yield. Under similar conditions “fibersil~”(from spruce) gave 24 the sulfite pulp industry; red have been closed beper cent cellobiose octa-acetate, whereas carefully puri$ed pine cedar ( J u n i p e r w uirginicause of the lack of basic cellulose prepared by the sulfote process and normal cotton cellulose una),used in pencil manuknowledge regarding the yielded 33 and 34 per cent, respectively. I t is evident that as far as facture and in cabinet makconstitution of cellulose, the cellobiose reaction i s concerned, wood cellulose from different ing; sugar pine (Pinus lamwould be opened up, and sources, and that isolated by different methods from the same source bertiam), used as finishing empirical investigations, behave very similarly, and that the cellobiose grouping is characterislumber; asDen (Populus which in the Past have tic of all the celluloses studied. grandiden tita), used in dominated the cellulose s o d a - p u 1 p manufacture; field, might be relegated to a subordinate position. To give a concrete example, if the beech (Fagus umericana), yellow birch (Betula lutea), and cellulosic portion of shortfibered hardwoods (like maple) were sugar maple (Acer saccharum), which are used in millidentical in constitution with that of spruce, there is no theoret- work and furniture as well as in the hardwood distillation ical reason why maple cellulose might not be utilized in place industry; white oak (Qwrcus alba), material for furniture; of the more valuable spruce cellulose in those industries and longleaf pine ( P i n u s p a h t r i s ) , which is now playing which, like the fiber-silk industry, are not primarily depen- such a large role in the production of sulfate pulp. With dent upon fiber length or fiber structure of the cellulose used. the exception of the cellulose of longleaf pine (furnished by Normal cotton cellulose is still the logical standard by which R. H. Stevens, of Joseph H. Wallace & Company, to whom to gage celluloses obtained from other sources. It was used grateful acknowledgment is made), the wood celluloses were in our experiments. The acetolysis reaction which the writers isolated by a chlorination method based on the analytical used in their preliminary work appeared worthy of further procedure described by Dore6 for the determination of celstudy. This reaction, while it has very decided limitations, lulose in woods. Since relatively large samples of wood indicates the presence or absence of the cellobioselinking which sawdust were used in each experiment, and since the object is so characteristic of cotton cellulose. It therefore has a was to obtain a sufficient quantity of purified cellulose for direct bearing on the question of the constitution of cellulose. further study, no attempt was made to obtain quantitative Quite recently Denham, by methylating cotton cellulose yields. In all experiments 20 to 30 grams of sawdust passing and hydrolyzing the product, obtained an 89 per cent yield through a 20-mesh sieve were used. The coniferous woods of 2,3,f%trimethyl glucose. His results have been reported were extracted for 6 hours with benzene and then for a like by Irvine,8 who has made a lasting contribution to the period with 95 per cent alcohol. This treatment removed chemistry of cotton cellulose. Sooner or later, no doubt, oils, fats, waxes, resins, and coloring matter, all of which this method of attack will be applied to celluloses derived might cause difficulty in subsequent treatments. from various plants, with a view towards obtaining further CHLORINATION PRocEss-The process of chlorination was carcomparative data on the similarity or dissimilarity of these ried out by passing a stream of washed chlorine, from a cylinder celluloses. Other methods of studying the problem are in of chlorine, a t the rate of 60 to. 80 bubbles per minute over the the hands of the physical chemists and physicists. The moist sawdust contained in a 2-liter, wide-mouth bottle. The bottle was first filled with an atmosphere of chlorine. It was proresearches of Herzog and his colleagues4 on the crystal struc- vided with a double-hole stopper and an inlet and outlet tube so ture of various celluloses have already been alluded to, and that the material remained in a slowly moving atmosphere of their real significance can only be gaged in the light of future chlorine during each period of chlorination. The bottle was frequently shaken and rotated during the process, but even this research. did not cause contact of each wood particle with chlorine during This paper records the results of the acetolysis reaction, each period of chlorination because of the tendency of the partistandardized and somewhat simplified as applied to normal cles to form small lumps. This lumping effect was especially (or a) cellulose isolated from a number of commercial hard- marked during the later periods of chlorination when the material woods and softwoods. These results have been compared became more of a pulp. During the first four or five chlorinations the wood became a dark orange, but the darkening became with those obtained in the case of purified cotton cellulose. less marked with subsequent chlorinations, and the sample The work is an extension of that reported in an earlier com- finally remained white in the presence of chlorine gas. The munication. chlorination periods used were 20,15,15, and 10minutes in length 1 Presented before the Division of Cellulose Chemistry a t the 64th Meeting of the American Chemical Society, Pittsburgh Pa., September 4 to 8. 1922. 2 TH19 JOURNAL, 14, 285 (1922). 3 J . Sac. Chem. i n d . , 41, 1361 (1922): J . Chcm. Sac. ( L o n d o n ; , 12S, 518 (19231. 4 Cellulosechemie, 2, 101 (1921); 2. Physik, 8 , 196, 343 (1920).
followed by 5 or 10-minute periods until the action was complete. In general, the conifers required a greater number of chlorinations than did the hardwoods. After each chlorination the material was shaken with water in order to insure same contact of all particles with chlorine. One hundred cubic centimeters of dilute sulfurous acid (50 grams sulfur dioxide per liter) were then 1 THIS JOURNAL, 18, 264 (1920).
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added as an “antichlor,” and the suspension was filtered and eutral to litmus. The addition of eriql f o becq*e lighter in solor, in addition to its dechlorinating out the procedure were made by of mercerized cofton. The use of tration, and a large part of the liquid could be pressed from the material by hand. The next step in the operation was to cover the acid-free material with a 3 per cent solution of sodium sulfite in a beaker and to heat the mixture in a boiling water bath for 45 minutes. ’At the end of this period the residue was filtered off and washed with hot water until free from sulfite. In the case of the hardwoods the sodium sulfite solution became a dark wine color when added to the material after the first few chlorinations. With subsequent periods of chlorination this color became lighter until it finally was no longer obtained. This was taken as an in n of the complete removal of lignin, and chlorination topped a t this point. Upon addition of the sulfite solution to the conifers after the earlier periods of chlorination the mixture became dark brown, but with subsequent chlorinations it became light brown until finally no color was obtained. This absence of color was taken as an arbitrary end point, and chlorination was then discmitinued.
The material resulting from the alternate chlorine and sulfite treatments is arbitrarily defined as “total cellulose.” f‘Korma1 cellulose,” or a-cellulose, was obtained by treating the total cellulose with 17.5 per cent sodium hydroxide solution for one-half hour, using 50 cc, of solution for each 2 grams of material. At the end of the half-hour period an equal volume of cold water was added and the suspension filtered. The material was washed with 2 to 3 liters of cold water, then with 2 liters of 10 per cent acetic acid, and finally with 2 to 3 liters of cold water. The action of the sodium hydroxide solution caused the removal of the products of oxidation by chlorine and the alkali-soluble forms of cellulosethat is, the so-called @ and y-celluloses. The normal cellulose was dried for 16 hours at 95” to 100” C., and allowed to stand in the air until it had established an equilibrium with the moisture in the air (and was air-dry). Analytical data relating to these cellulose samples are given in Table I. TABLE I-ANALYTICAL DATA ON CELLULOSES USED IN Water ’ Ash CELLULOSE FROM Per cent Per cent 0.13 7 5 Pine (wood) 0.31 7 4 Bhlsam (wood) 0.37 8 3 Birch (wood) 0 22 7 6 Spruce (wood) 0 17 7 7 Cedar (wood) 0 32 8 8 0 Maple (wood) 0.18 7 6 Aspen (wood) 0.16 7 5 Hemlock (wood) Not determined 9 7 Beech (wood) Not determined 11 2 Oak (wood) 0.15 5 1 Cotton (normal) .... 5 4 Spruce (sulfite pulp) 0.31 Pine (sulfate pulp) 5.4 0.50 7.5 Fiber silk (spruce)
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creased in the process of isolation. The a-cellulose, therefore, represents a convenient stage in the purification of cellulose, beyond which it is inadvisable or unsafe to go. As previously mentioned, the cellulose of longleaf pine was prepared not by this method, but by the sulfate process. Mr. Stevens, who carried out the isolation and purification of this pulp in the research laboratories of Joseph H. Wallace & Co., at Stamford, Conn., states’ that the pulp was made from pine stumps, and that the first step in the process was a sulfate cook, using 25 per cent active alkali (calculated on the basis of the bone-dry wood). The yield was low because of the very high resin content of P i n u s palustris and also because of the drastic nature of the cook. A yield of 24.5 per cent of fairly easy bleaching pulp (not Kraft) was thus obtained. The final methods of purification of this material are not given. Analytical data are included in Table I. The normal cotton cellulose used by the authors was purified by the method initially outlined by the Committee on Standardization of Cellulose of the Cellulose Division of the AMERICANC H E M I C ~SOCIETY. L The purification is very similar to that suggested by Robinoff.8 This material was purified and analyzed by W. Vanselow, of Syracuse University, .to whom thanks are due. Besides the celluloses mentioned, a sample of fiber silk made from Riordon pulp, obtained through the courtesy of the duPont Fibersilk Company of Buffalo, was used in one experiment.
ORIENTATING ACETOLYSIS EXPERIMENTS
I n general, the technic used in carrying out these acetolysis experiments was similar to that described in a previous articleU2 Two-gram samples of air-dried normal (a) cellulose were subjected to acetolysis. The material did not dissolve in the acetolyzing mixture as readily as in the case of cotton, owing probably to its being in a more compact form and exposing less surface t o the liquid. Heating at 40” to 50’ C. in a water bath was resorted to in order to effect peptization. In the initial experiments the best heating EXPERIMENTS Pentosans conditions were found to be for 1 hour a t the end of 24 hours Per cent of acetolysis and at the end of 48 hours. Later experiments, 15 1.7 however, indicated that such heating periods could be en3.3 1.5 tirely eliminated. The acetolysis mixture was allowed to 2 0 stand at room temperature (about 25” C.) for 6 to 7 days. 3 3 5.6 At the end of this period a crystalline mass had formed and it 1 8 3.2 was treated as described in the earlier communication. 3.0 The product crystallized from alcohol was filtered, 1.15 1.25 dried, recrystallized from 95 per cent alcohol, and again 2.2 2.4 dried for use in the melting point determinations. The
In order to avoid misinterpretation of their results, the authors wish to have it clearly understood that they do not assume a-cellulose to be a homogeneous chemical individual or that the method of isolation used is an ideal one. Any present chemical treatment leading to the removal of lignin is necessarily’ drastic. I t is inconceivable that under these conditions the cellulose originally present in the wood remains chemically unaffected. Some of the cellulose units are probably oxidized; others no doubt are hydrolyzed, but with our modern concept of a cellulose aggregate made up of innumerable cellulose units6 there is no reason to assume that all these cellulose units are destroyed. The “mercerization test” (17.5 per cent alkali treatment) removes an appreciable amount of noncellulosic material (furfural-yielding groups) originally present in .the wood. It also appears to remove substances resulting from the cellulose units that were chemically altered during the chlorination process. It is also quite probable that. the alkali dissolves a portion of the cellulose the surface area of which has been largely ins THIS JOURNAL, 16, 711 (1923).
T’ol, 15,-No. 8
TABLEII-REsIJ&Ts
SOURCE O F CELLOBIOSE Balsam Cedar Hemlock Pine Aspen Beech Birch Maple
Pine sulfate pulp Fiber silk
OF
MELTINGPOINTDETERMINATIONS ON SAMPLES OF CELLOBIOSE OCTA-ACETATE Melting Point of Crystalline Product Mixed Melting Point of Cryswith Cellobiose Octatalline Product Alone acetate from Cotton (Uncorr ) (Uncorr.) c. a C. 227 5 t o 228 6 227 t o 228 228 6 226.5 227 227 t o 228 227 t o 228 5 227 t o 228 227 t o 228 227 t o 228 227 t o 228 6 227.5 to 228 227 5 t o 228 226 5 t o 227 5 227 226 5 to 227 227 5 to 229 227 t o 228 5 227 to 228 227 to 227.5 227 5 lo 228
226 5 t o 227 227 t o 227 6
2 2 6 . 5 to 227.5
226.6 to 227.5
yields of cellobiore octa-acetate fluctuated widely and were often far from satisfactory, probably because of the difference in the state of division of the original samples. TherePrivate communication, July 19, 1922. “Uber die Einwirkung von Waser und Natronlauge auf Baumwolle,” Dissertation, Darmstadt, 1912. 7
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I-VDUSTRIAL A N D ENGINEERING CHEMISTRY
August, 1923
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TABLE 111-COMPARISON OF YIELDS OF CELLOBIOSE OBTAINED FROM CELLULOSE ISOLATED FROX VARIOUSWOODSA N D COTTON Pine Balsam Birch Weight of air-dry cellulose taken, grams 2 000 2 000 2 000 Weight of cellulose taken (corrected for water, pentosans, a n d a s h ) , grams 1 818 1 812 1 760 Yield of cellobiose 0 980 octa-acetate, grams
1 008
1 036
Pine (Sulfate)
Fiber Silk
Spruce (Sulfite)
Purified Cottond
2 000
2 000
2 000
2 000
2 000
1 620
1 716
1 842
1 114
0 922 (all 274 ( b ) l 263
Spruce Cedar
Maple Aspen5 Hemlock Beech
2 000
2 000
2 000
1 814
1 802
1 768
1 732
1 810
1 039
1 010
1 080
0 864a
0 933
2 000
2 000
l 860b
Oakc
1 792 1 868 1 872(a) ( b ) 1 394 911(c) ( d ) 0 905 (a) 1 182 ( a ) 1 ( b ) 1 185 ( b ) 1 372 (0 1 310 (4 1 339 (a130 3 (a)35 6 24 2 (b)35 2 (b)30 3 (~132 (d)33 a
Percenldge of theoret(a133 1 icalyieldofocta-ace- 25 8 26 6 28 2 27 4 26 9 29 2 23 9 24 7 32 9 25 7 (b)32 8 5 tate calculated from corrected weight of cellulose a Xechanical loss during crystallization of cellobiose octa-acetate The result IS therefore low b Relatively smaller amounts of acetic anhydride and sulfuric acid were used In this case c h-o thermostat control was used in this case d (c) and ( d ) of this series show the effect when the thermostat control accidentally failed For a few hours the temperature of the acetolysis mixture dropped t o 14O C (from 25' C ) , otherwise, experimental condltions remained the same.
fore, in these preliminary experiments each cellulose required individual study, and the best conditions for securing prompt peptization of individual celluloses were only obtained after considerable experimentation. MELTINGPOINTDETER~~INATIOI~S-A short-stem thermometer, 200" to 250' C. range, and a concentrated sulfuric acid bath in a Thiele melting point apparatus were used in these determinations. A melting point determination was made of each crystalline product, both alone and in admixture with an equal amount of cellobiose octa-acetate obtained from cotton (m. p. 227.5' to 228" C., uncorr.). Table I1 shows the results of the melting point determinations. QUANTITATIVE ACETOLYSIS EXPERIMENTS A s i andardized procedure was finally adopted, which permitted us to carry out acetolysis experiments under nearly identical conditions. Two grams of air-dried sample were put into a mixture of 8 grams of acetic anhydride (b. p. 135' to 137" C.) and 2 grams of concentrated sulfuric acid (sp. gr. 1.83) in a 125-cc. widemouth, glass-stoppered bottle. The mixture was prepared by adding the sulfuric acid t o the acetic anhydride, cooled t o 10' C. a t such a rate that the temperature did not rise above 0" C. during the addition. During the preparation of the mixture and the addition of the sample the glass stopper was replaced by a cork stopper through which a thermometer was inserted. The sample was pressed down so as t o moisten the substance thoroughly, and the mixture was then allowed to stand for a t least an hour and sometimes a n hour and a half in an ice bath. The glass stopper was then replaced and the bottle put into a bath kept a t 25" * 0.2' C. by means of thermostatic control, for 6 days. If the sample had not gone into solution a t the end of 24 hours, it was stirred with a small glass rod, previously placed in the bottle, and frequent stirring was giveq until the fibers had disappeared. Crystallization began within 50 to 60 hours after placing in the bath, and a t the end of the 6-day period a stiff, crystalline mass had formed. To this mass were added 6 cc. of glacial acetic acid and the mixture was warmed on a water baih (to a temperature not above 50" C.) until it could be poured from the bottle into 200 cc. of water a t 0" to 10' C. The bottle was rinsed with 150 cc. of cold water and the precipitate allowed to stand in the water a t 5" to 10" C. for 1 hour. It was then filtered off on a Buchner funnel, mercerized cotton being used as the filtering medium. The precipitate was washed with cold water until free from acid and sulfate when tested with litmus and barium chloride solutions, and as much water as possible was removed by suction. Within 24 hours the material was removed from the Bdchner funnel with alcohol and allowed to remain under 200 to 250 cc. of alcohol until it was convenient to recrystallize it. The first crystallization from alcohol was accomplished by dissolving the precipitate and filtering or'decanting off froq any undissolved portion. 1 Crystallization was allowed to take place slowly. after which the crystals were filtered on a weighed Gooch crucible, using asbestos as the filtering medium. The filtrate was evaporated to 75 cc. and allowed t o stand for 3 days a t room temperature in order to obtain a, sgcond crop of crystals. The yields recorded in Table I11 are based on the total yields of cellobiose octa-acetate obtained under these conditions.
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The tendency in the past has been to discuss alleged differences or similarities in chemical constitution of celluloses derived from different sources on the bases of analytical data. For example, certain investigators cherish the belief that if the total cellulose isolated from a wood contains a relatively large percentage of a-cellulose, whereas that prepared from another wood by a nearly identical procedure contains a much lower percentage of a-cellulose, the original celluloses in the two woods cannot be chemically identical. Similarly, a normal cellulose which retains 5 per cent of furfuralyielding material is viewed by certain experimenters as being constitutionally different from normal cellulose retaining only 1 per cent of pentosans. These differences might just as easily result from physical differences in cellulose, elaborated in the formation of the original wood. No one mill controvert the fact that residues (termed "cellulose") obtained from different woods are actually not identical. On the other hand, analytical differences cannot indicate whether or not the preponderating material in each of these various residues is actually one chemical substance, and they throw no light whatsoever on the chemical constitution of the cellulose of the original wood. Methods used in technological investigations of pulp have become a fetish and the building of hypotheses regarding the constitution of cellulose on data furnished by such methods should be discouraged. This question has been extensively discussed in a previous article.2 As a result of the authors' work, it can he definitely stated that the cellobiose linking occurs to the extent of 24 per cent in each of the celluloses examined, and hence in this respect at least all the celluloses are similar. Since the acetolysis mixture is known to destroy appreciable amounts of cellobiose durihg acetolysis, 24 per cent is a minimal figure. Taking the unavoidable losses into consideration, the cellobiose linking may occur to the extent of nearly 50 per cent in each case.g Furthermore, the rate of acetolysis in all celluloses examined is roughly the same, Whether or not the differences in cellobiose yields (24 to 35 per cent of the theoretical yield) are worthy of note is still an open-question. The influence of small amounts of impurities on cellobiose yields has not been studied. However, the data show that there are appreciable variations in cellobiose yields in the case of the same purified cotton, if the experiments are made a t different times even though similar technic is used.'O This would indicate that very slight variations in the technic of acetolysis of cellulose or isolation of the cellobiose octa-acetate cause these differences and that the quantitative yield data in Table 111, while very suggestive, cannot be interpreted too literally. 0 Freudenberg, Beu , 44, 767 (1921), whogives evidence regarding the percentage of cellobiose actually formed and lost during acetolygis, based upon experimental as well as theoretical grounds. 10 Table 111, Footnote d.
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In the writers' opinion there are no data in the literature which would force the conclusion that the celluloses of the various seed-bearing plants are different chemical substances.
APPENDIX-OPTICAL PROPERTIES
OF CELLOBIOSE OCTA-
ACETATE [By
EDGAR T.WHERRY, Crystallographer, Bureau of Chemistry, Washington, D. C . ]
Two samples of cellobiose octa-acetate prepared by Wise and Russell, one from cotton cellulose and the other from wood cellulose, were examined. They showed identical properties. In ordinary light: Seen to consist of minute rods. Kefractive indices (D): CY = 1.470, @ = 1.480, y = 1.505, all It. 0.005; y CY = 0.035 Lengthwise of the rods index p is shown, while either of the others may be shown crosswise. In parallel polarized light, Nicols crossed: Double refraction strong, the colors being bright gray, even on very thin crystals. Qxtinction parallel; elongation * The technic used in identification is as follows: Use a microscope equipped with a t least one Nicol prism, and ascertain the direction of the vibration plane of this Nicol. Immerse a small
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Vol. 15, No. 8
quantity of the substance in a drop of liquid with refractive index n near 1.48. Commercial liquid petrolatum is the most satisfactory, but almond oil, castor oil, or pseudo-cumene may also be used. Partially close the substage diaphragm, and center a broad crystal. Turn the stage until this crystal approaches parallelism with the cross hair indicating the vibration plane of the Nicol. If the substance is cellobiose octa-acetate, the crystal will disappear, and will remain invisible even on successively raising and lowering the microscope tube with the fine adjustment. This shows the refractive index lengthwise to be equal to that of the liquid, and this index is the most characteristic of the substance. Immerse another sample in a liquid with n near 1.47, such as glycerol or turpentine, and observe the behavior of crystals on turning them into perpendicular position with reference t o the vibration plane of the Nicol. Occasionally, a crystal will b a found which will disappear in this position, showing its index crosswise to be equal t o that of the liquid. Repeat with a liquid such as sandalwood oil or propyl iodide with n near 1.505. Under these conditions occasional crystals will also disappear, their index crosswise being the same as that of the liquid. In this way three refractive indices can be matched, and the identity of the substance as cellobiose octa-acetate may be definitely confirmed.
Effect of Hydrogen-Ion Concentration on Adsorption of Dyes by Wool and Mordants' Preliminary Paper By 0.Reinmuth and Neil E. Gordon UNIVERSITYOF MARYLAND, COLLEGE PARK, MD.
W
ORK in this laboratory on inorganic gels in connection with soil colloids led us to believe that the
hydrogen-ion concentration played a very important role in (a) the adsorption of dyes, ( b ) the color which they imparted to the fiber, and (c) the manner in which they were adsorbed. The literature showed that very little had been done on the adsorption of dyes from solutions where special attention was paid to the hydrogen-ion concentration. Considerable work was carried out with this end in view, but its completion has been unavoidably delayed. I n the meantime an article by Briggs and Bull2 appeared practically covering the work which the authors had been carrying out on the color, adsorption, and hydrogen-ion concentration of fiber. However, Briggs and Bull did not take up any work on mordants, and the authors are therefore making a preliminary report on one of the mordants.
MATERIALS Orange I1 was one of the dyes first used. Other dye baths are being used a t the present. The wool was white sweater yarn of the best grade, washed, dried, and kept in a desiccator until used. The mordants used most were alumina and silica. When mordants were used without the wool they were prepared in the form of gels, as described in a previous a r t i ~ l e . ~When the mordants were used with the wool, the gels were precipitated in the fiber.
EXPERIMENTAL The baths were prepared of varying hydrogen-ion concentration by adding 0.1 N solution of sodium hydroxide or sulfuric acid. The ratio between the milligrams of dye and 1
Presented before the Division of D y e Chemistry at the 65th Meeting
of the American Chemical Society, New Haven, Conn., April 2 to 7, 1923. 2 J . Phys. Chem., 16, 845 (1922). I Soil Sci., 18, I57 (1923).
the weight of the wool or mordant was kept constant throughout the runs. The time allowed for equilibrium in each case was the same. The temperature of the bath was kept a t the boiling point during adsorption. The amount of dye adsorbed by the pure wool, mordanted wool, or mordant alone was determined by titrating a sample of the dye solution before and after adsorption had taken place. Titanium chloride was used for determining the concentration of the dye, as suggested by K n e ~ h t . ~ The pH values of the bath were determined by the use of a hydrogen electrode. The data obtained for the fiber were so much like tho& of Briggs and Bull that they will not be given in this preliminary report. The following table gives one an idea of results obtained when an acid, such as Orange 11, is permitted to be adsorbed by a mordant, such as alumina, under a varying hydrogen-ion concentration. EFFECT OP HYDROGEN-ION CONCENTRATION ON
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PH Value 3.657 3.753 3.888 4.145 4.260 4.514 4.852 5.021 5.393
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Alumina Gel Dry Wet G. G. 13.92 1 0231 14.13 1 0385 7.95 0 5843 11 17 0.8210 10 50 0 7417 9 43 0 6931 10 26 0.7541 13 65 1.0023 14 33 1.0532
BY
TH6
GELS
Dye Used Mg. 525.0 532.7 299.7 421.1 395.8 355.5 386.8 514.5 540.2
Dye Adsorbed Mg.
283.9 287.6 120.2 139.6 117.4 93 0 82 9 45.0 47.1
ADSORPTION OF DYES Dye Left in Bath Mg. 241.1 245.0 179.6 288.5 278.4 262.4 303 9 469.5 493.1
Mg. Dye Adsorbed per G. of Gel 278.2 276.9 205.9 169.4 152.2 134.3 111.0 44.9 42.2
This marked change of adsorption with the small change in p H value makes it quite evident that a control of hydrogenion concentration is a most important factor in the dye industry. There is also a marked change of color with a change of hydrogen-ion concentration. This was especially noticeable with some dyes and a t certain pH values. A full discussion of this and change of 'color with the strong adsorption of d y e will be reported in a later paper. 4
Ber., S6, 1552 (1903); 40, 3819 (1907).
