V O L U M E 25, NO. 6, J U N E 1 9 5 3 (4) Flexser, L. A., Hammett, L. P., and Dingwall, A., J. Am. Chem. Soc., 57, 2103 (1935). (5) Geld, I., and Carroll, J., ANAL.CHEM.,21, 1098 (1949). (6) Hall, R. D., and Smith, E. F., J. Am. Chem. Soc., 27, 1369 (1905); Proc. Am. Phil. Soc., 44, 177 (1905). (7) Hammett, L. P., and Deyrup, A. J., J . Am. Chem. SOC.,54,2721 (1932). (8) Hiskey, C. F., ANAL.CHEM.,21, 1440 (1949); Trans. N . Y . Acad. Sci., 11, 223 (1949). (9) Hiskey, C. F., and Batik, A. L., ANAL.CHEM.,25, 823 (1953). (10) Hiskey, C. F., Newman, L., and Atkinson, R. H., Ibid., 24, 1988 (1952). (11) Hiskey, C. F., Rabinowita, J., and Young, I., Ibid., 22, 1464 (1950). (12) Klinger, P., and Koch, W., Arch. Eisenhiittenw., 13, 127 (1939). (13) Marignac, J., Ann. chim. phys., 8, 5 (1866); 9,249 (1866). (14) Melikov, P., and Pissarjewsky, M., 2. anmg. Chem., 20, 344 (1899). (15) Schaeppi, Y., and Treadwell, W. D., Helv. Chim. Acta, 31, 577 (1948).
931 116) Schoeller, W. R., “The Analytical Chemistry of Tantalum and Niobium,” London, Chapman and Hall, Ltd., 1937. (17) Sieverts, Von A., and Mtiller, E. L., 2.anmg. U . allgem. Chem., 173,297 (1928). (18) Slavin, M., Pinto, C. M., and Pinto, M., “A Tantalita de Nor-
desk,” Ministerio da Agricultura, Departmento Nacional da (Produpgo) Mineral, Rio de Janeiro, Brasil, Bd.,21 (1946). (19) Telep, G., and Boltz, D. F., ANAL.CHEM.,22, 1030 (1950); 23,
901 (1951); 24, 163 (1952). (20) Thanheiser, G., Mitt. Kaiser-Wilhelm Inst. Eisenforsch. Diisseldorf, 22, 255 (1940). (21) Tschernikow, J. A., and Karajawskaya, M. P., 2. anal. Chem.. 98, 97 (1934). (72) Weissler, A., IND.ENQ.CHEM.,ANAL.ED., 17, 696 (1945). RECEIVED for review October 29, 1952. Accepted March 26, 1953. Experimental d a t a taken in large part from the thesis submitted by F. C. PaliIla to the chemistry faculty of the Polytechnic Institute of Brooklyn in partial fulfillment of the requirements far the degree of master of science in chemistry, June 1952.
Determination of Pentosans in Highly Purified Wood Pulps EDGAR D. SMITH’ AND L. N. ROGERS The Buckeye Cotton Oil Co., Memphis, Tenn.
A more accurate, as well as a more precise, method for the determination of pentosans in highly purified wood pulps was sought. By means of newly developed analytical techniques it was shown that the present standard TAPPI method for the determination of pentosans is not suitable for application to highly purified wood pulps. The method can be greatly improved and simplified by modification of the distillation conditions to obtain a more favorable, as well as a more constant, ratio of furfural to hydroxymethylfurfural. No simple method has heretofore been applicable for the determination of pentosans in the region 0.5 to 2.0%. In the absence of such a method it has not been practicable to attempt to correlate pentosans with other properties of highly purified wood pulps. A simple and precise method is described which should make i t possible to determine such correlations.
I
K AN earlier paper by the present authors ( 4 ) it was shown
that the standard Technical Association of the Paper and Pulp Industry (TAPPI) pentosan procedure was not suitable for application t o highly purified pulps containing 1% or lew of pentosans. Primarily, this was due t o the poor sensitivity of the furfural analyFis methods used, but a potentially serious error was also introduced by uncertainty as t o the quantity of hydroxymethyl furfural distilled over with the furfural. A sensitive colorimetric furfural analysis method is presently available in the literature ( 1 ) and the present authors have described a highly sensitive method for analyzing total aldehyde (furfural plus hydroxymethyl furfural) by means of ultraviolet absorption. It was the purpose of this work to apply these methods to pentosan distillates to determine the optimum conditions for furfural recovery and analy-is. The apparatus employed for this work was that recommended by T A P P I (T223 m-48), with the exception that electrical heating was substituted for gas heating so that distillation rates could be more readily controlled. The experiments were designed factorially ( 2 ) for maximum efficiency and so that any important interartions between the variables might be discovered. The fir-t set of factorial experiments was designed to study the effect of the following variables on the quantitie- of furfural and hydroxymethyl furfural evolved from the pulps: pulp type, quantity of distillate collected, and rate of distillation. Table I summarizes the statistical design used along with the experimental results. The pentosan distillates were analyzed by both the ultraviolet absorption method (furfural plus hydroxymethyl Present addicss Thp Chemstrand Corp , Decatur, Ala.
furfural) and by the aniline acetate colorimetric technique which is specific for furfural. The differences noted between these two methods were than calculated as hydroxymethyl furfural by multiplying by the appropriate factor. Distillations were carried out by the standard T A P P I procedure except as noted. Variance analysis of this data was carried out to determine which of the indicated variables was significant, with results 8s summarized in Table 11. As indicated by this table, i t was found that there were no significant interactions between the variables studied. Other conclusions derived from the results of Tables I and I1 may be stated as follows:
Furfural Yields. Table I.
The yields were strongly affected by pulp
-
Factorial Experimental Design and Results
Pulp types: PI = acetate wood pulp: P2 viscose wood pulp Distillate volumesa Q I = 200 ml.; Qn = 300 ml.; Qs = 400 ml. Distillation ratesa: RI = 1.5 ml./min.; Rz 3.0 ml./min.; Rs = 6.0 ml./ min. Furfural Yields” Hydroxymethyl Furfural Yieldsb PI QI
Qz
Ri Rz
Rs RI Rz Rs
7.1 6.9 5.8
P2
19.6 18.1 16.4 7 . 9 19.7 6 . 9 19.5 6 . 9 18.6
Pi
Pz
2.2 1.2 1.2 4.1 5.0 2.8
1.4 1.6
1.0 3.4 3.8 2.9 7 . 32 6
Ri 8.0 19.5 6 5 . 86 7 . 6 18 8 R8 6.5 18.3 6.2 5.7 0 Standard T A P P I conditions are Q z and Rz. b Yields given in terms of milligrams of indicated compound per gram of bone dry pulp distilled. Q3
Ri
932
ANALYTICAL CHEMISTRY
type and distillation rate, and slightly affected by the quantity of distillate collected. The yields were a maximum at the slowest distillation rate used (1.5 ml. per minute). At the slowest distillation rate tested, only 200 ml. of distillate sufficed t o bring over essentially all of the furfural obtainable, n hereas, a t the faster rates, results were low even when 400 ml. of distillate were collected. Hydroxymethyl Furfural Yields. The yields were not affected by the type of pulp distilled, but were affected greatly by t h e quantity of distillate collected and slightly by the rate of dist illat ion The maximum quantity of hydroxymethyl furfural obtained undrr recommended TAPPI conditions was only 5.0 mg. per gram of pulp, vihereas T A P P I calculat.ions are based on an empirical correction factor amounting to 8.4 mg. per gram. The hydrosymethvl furfural yields increase with quantity distilled so that more hydroxymethyl furfural than furfural was evolved in the last 100 ml. of distillate collected under TAPPI conditions. T n r ~rirlds of hydroxymethyl furfural were a maximum a t the tlirtillation rate chosen by TAPPI. ~~~~
~
Table 111. Factorial Experimental Design and Results" Pulp typesb: Pi = viscose pulp. P2 = viscose pulp H C I c o n c e n t r a t i o r ~ s ~Q:I = 8%: Qr = 12%; Q P = 16% Distillate volumes: Ri = 200 ml.': Rz = 100 ml. Furfural Yieldsd Hydroxymethyl Furfural Yieldsd Pi P2 P1 PP Q i Ri 8.2 17.0 1.3 2.3 10.1 R2 4.5 0.4 0.0 Qa Ri 11.2 16.6 5.1 3.7 9.4 13.8 1.4 1.3 R2 14.0 6.4 7.6 Qa RI 8.7 10.6 Rt 7.8 3.5 5.8 a Distillation rate for all samples was 1.0 ml per minute. Tire cord type pulps from two different manufacturers. T A P P I uses 12% acid. d Yields given in ternis of milligrams of indicated compound per gram of hone dry pulp distilled.
*
Table IV.
Results of Variance Analysis of Furfural and Hydroxymethyl Furfural Yields
Source of Variance
Table 11. Results of Variance Analysis of Furfural and Hydroxymethyl Furfural Yields Soiircr of Variance'
-
Degrees of Freedom
Mean Squares
Significance Level, %
Between P Beta-een QQ Betwren Q L Between R L Residual
Furfural Yields 1 611.33 1 1.14 1 1.92 1 7.21 13 0.19
0.1 5 1 0.1
Between Q L Between RQ Residual5
Hydroxymethyl Furfural Yields 1 71.05 1 1.96 15 0.30
0.1 5
' 1 Subscripts refer t o linear or quadratic variance components of the indic a t r d variables ( 2 . p. 123). b Obtained hy pooling all factors not significant a t 5% level.
The above results show that the T.%PPI distillation rate and clidllate volume must be changed in order to rearh optimum wnditions for recovery and analysis of furfural from pentosans. A second 5et, of factorial experiments was therefore designed to determine whether the arid concrntration used for these distillations should likewise be changed. This work is summarized in Table I11 and the rrsult,s of the variance anal i n Table IV. I t will he seen from t.hrse figures that furfural yields are a maximum at 12y0 hydrovhloric acid concentration while the hytlrosymethyl furfural yield- caontinue to increase with acid conr(,ntration. It will be realized from this that lon.er acid concentrations might prove advantageous by reduring the amount of hydros,>-niethylfurfural distilled hut, Pincr the use of lower acid roncentrations would necessitate longer distillation in order to hring over all of the furfwnl, this poraibilit,- w a p not explored further. The results of Tnble I11 a190 show that even a t the very slow rate of distillation used here, more than 100 ml. of distillate were required to bring over a11 of the furfural. In hoth sets of fact,orial experiments it was found that hydroxyinethyl furfural yields were not affected by pulp type. Provided this were generally true so that under a given set of diPtillatiorl cwntlitionr the same itinourit of hydrosymethyl furfural was always evolved, then the ultraviolet analysis results could be used to obtain an accurate arid precis
