Heterogeneous Acid Hydrolysis of Native Cellulose Fibers E. A. IMMERGUT~AND B. G. R ~ N B I - ~ Institute of Physical Chemistry, University of Uppsala, Uppsala, Sweden
T
HIS investigation was carried out in order to study the
effect of dilute (nonswelling) mineral acid hydrolysis on the fine structure of native cellulose fibers. According to earlier investigations (11, do), such a heterogeneous hydrolysis apparently occurs in two stages-an initial rapid process and a subsequent slower reaction. The initial phase of the hydrolysis has been studied extensively by a number of authors ( I , 4, ?,I#, I S , 17-19, 24). Therefore, the authors' aim was to concentrate more on the prolonged hydrolysis to low yields of hydrocellulose residue, the kinetics of which has been investigated by Millett, Moore, and Saeman ( 1 5 ) .
lock sulfite pulp (an acetylation grade pulp, Rayaceta, from Rayonier, Inc., New York). The original materials Kere hydrolyzed in constant-boiling hydrochloric acid a t the boiling point to different yields given in Table I. This hydrolysis was carried out a t the Forest Products Laboratory, Madison, Wis., by a procedure described in the literature (15). The saniples were washed neutral, sterilized, and then sent to Uppsala suspended in water. They were subsequently stored in the frozen state (-16" C.) until they were used. The easily hydrolyzed portion of both the Empire cotton and the hemlock pulp was 1170 according to measurements a t the Forest Products Laboratory, Madison, Wis.
MATERIALS INVESTIGATED
The samples chosen for this study were hydrocellulose residues from a raw- dewaxed Empire cotton and from a high-alpha hem-
A
--7-* C
MOLECULAR WEIGHT V S . HYDROLYSIS EXTENT
In order to follow the effect of the prolonged hydrolysis on the degree of polymerization ( D P ) of the samples, a portion of each
m,,
Table I.
Intrinsic Viscosity, and Dimensions of Particles in Cellulose after Hydrolysis Chains Av. Particle Residue Length, Size, A. After A. (Electron Hydroly___ (5.15 Microscope) SlS, Sample % [q] DP, X DP,) Length T i d t h
00
-
'
RI
P"
0
50
%Residue
Figure 1. Effect of prolonged heterogene2 s hydrolysis on viscosity [ q ] and osmotic DP, of native wood (W) and cotton (C) cellulose
1 M 2 M 3
[VI value.
0.
DP,value
Hemlock pulp 0.982 78 0.692 61 0.562 54
400 314 278
358
..
124 107
309
95
,
Empire cotton M 4 80 1.403 88 453 450 102 M 5 40 88 453 ... 101 1.245 1.333 88 453 452 100 M 6 15 The [n] and values are measured for nitrated hydrocelluloses in butyl acetate solution a t 25" C., and D X values are calculated from the osmotic molecular weights (Mn) with the unit molecular weight 287 (corresponding to 13.5% N). The original hemlock pulp and the Empire cotton samples have the legends M 01 and M 04, respectively.
Present address, Dunlop Research Center, Toronto 8, Can. Present address, Research and Development Division, American Viscosc Corp., Marous Hook, Pa. 1
2
A.
80 40 15
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solvent (3-ml. solvent volume). The measurements mere carried out a t 25.0" C. The results are shown in Figure 1 together with data from osmotic measurements. From Figure 1 it may be seen that a considerable decrease in 1771 occurs with the wood pulp samples ( R I 1, &I 2, M 3): whereas the corresponding effect of the hydrolysis on the [ q ] values of the cotton samples (51 4, ilI 5, M 6) is much smaller. The slopes of the viscosity curves of the semilogarithmic plots (log T . ~ / Cvs. c ) are all about the same indicating a constant Huggins k' value. I n order t o obtain number-average degrees of polymerization (Dp,) by independent measurements rather than by calculation from the intrinsic viscosities, osmotic pressure measurements were carried out on the nitrates in butyl acetate. The membranes used consisted of Type 100 Ultracella filters (Rlembranfilter AG., Gottingen, Germany) and t,hey were conditioned to butyl acetate by the usual method of extracting the mater with ethanol and replacing the latter with butyl acetate by successive stages. The osmometers used were of the Zimm-Myerson type (29) equipped with stainless steel plates and Teflon gaskets (obtained from J. V. Stabin, 601 E. 19th St., Brooklyn, N. I-.). A11 measurements were carried out at 25.0 =tO.0lo C. The membranes were rather tight so that for most of the samples an equilibrium osmotic pressure head n'as established; for the samples nrhere the height us. time curve indicated diffusion of solute through the membrane t,he curve was extrapolated to zero time-a correction of 1 to 2% of the measured pressureand t,he resulting height difference used to calculate the osmotic pressure. The results for osmotic pressure measurements of cellulose nitrates in this low molecular weight region are presented in Figure 2 , shoiving A h / c vs. c plots ( A h in centimeters of butyl acet,ate, density 0.877, c in grams per deciliter). I t is again apparent (Figure 1) t,hat the prolonged hydrolysis has no noticeable effect on the cotton sample ( M 4, AI 5, RI 6 ) but causes a considerable decrease in the molecular %-eight-of the wood pulp (ai 1, 11 2, M 3). The number-average DP,,, calculated from the values of Ah/c a t c = 0 (taking the molecular n-eight of the nitrated glucose unit to be 287 for 13.5% nitrogen content)! shom a decrease of 30y0 for the wood pulp samples in going from 80%; to 15% residual cellulose (Figure 1). S o change can be observed for the c.orrespouding cotton samples. The DP, values are given in Table I.
dhcm
c grn/dl
"
Vol. 48, No. 7
t
Figure 2. Osmotic measurements of hydrolyzed wood (&I 1, R I 2, hI 3) and cotton (31 4, JP 5, RI 6) celluloses
sample v-as nitrated by a previously described procedure ( g ) . The water was removed from the hydr ocelluloses by subsequent mashing with methanol, ethanol, and cyclohexane to avoid formation of hard aggregates, and the samples r e r e dried ovei solid sodium hydroxide. The samples r e i e nitrated for 4 hours a t 0" C. with a nitration mixture containing nitric acid, phorphoric acid, and phosphorous pentoxide in the proportions 48 to 50 to 2 by weight. Thckntrinsic viscosity. [?Ij of the nitrated samples r a s determined from viscosity measurements in butyl acetate, using an Ostwald viscometer Tith a flow-time of 149.0 seconds for the pure
- n
7
A
M 04
I
Figure 3.
Photometer curves showing effect of hydrolysis on x-ray diffraction diagram of native hemlock pulp (AI 01, SI 1, ILI 3) (Rayaceta) and Empire cotton (h1 04, 3I 4, WI 6), respectirely
July 1956
Figure 4.
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Electron micrographs of hydrolyzed hemlock pulp (M 1, left) and Empire cotton (31 4, right), respectively, a t 80Yo residual cellulose
Both dispersed in water by ultrasonic irradiation, prepared on cellulose nitrate support (Zapon lacquer, membrane), and shadowed with Au-Mn. Magnification 6 X 8500 = 51,000 X
X-RAY DIFFRACTION ANALYSIS
The air-dried samples were analyzed by x-ray diffraction ( C u K a radiation from a fused Philips tube, X = 1.539 A, made monochromatic and focused with a bent quartz crystal) using Guinier powder cameras, built by G. Hagg, Uppsala. The cameras were calibrated using sodium chloride. The samples were mounted (pressed in a frame as self-supporting layers, thickness of 1.0 mm. and containing 50 rt 5 mg. of cellulose per q. em). The exposures were all 2 hours with the same x-ray intensity (emission current 25 ma. a t 45 kv.) and the film (Ilford, Industrial G, x-ray film, double-layered) was developed for 5 minutes a t 20" to 22" C. using Kodak x-ray developer. It was found that both with the cotton and the wood pulp, the x-ray reflections become better resolved going from the original unhydrolysed sample to SOYo residual cellulose (31 01 to M 1 and R!I 04 t o M 4). Photometer curves of the x-ray diagrams are given in Figure 3. Further prolonged hydrolysis shows no further change for the cotton sample (iM 6) whereas the wood pulp reflections (M 3 ) become wider [especially, the (002) reflections which are referred to lattice planes parallel v i t h the cellulose chains] and the background increases. Measurements of the widths A(sin 8/2) of the (002) reflections a t half the maximum intensity have been made using the photometer curves (Figure 3). No corrections for specimen thickness n-ere applied. The following relative widths given as A(sin 8/2)/(sin 8/2) values were obtained: 0.158, 0.137, and 0.158 for R I 01, M I, and M 3, respectively, and 0.128, 0.120, and 0.118 lor RI 04, M 4, and M 6, respectively. The difference between 11 4 and 1cI 6 is of the same order of magnitude as the estimated experimenhl error. The law width value (0.137) for M 1 may be explained as a recrystallization effect. Minor recrystallization effects (2 to 5%) in heterogeneous hydrolysis of native cot,ton cellulose have been reported (9, 26). The increase to 0.158 for M 3 is interpreted to mean a reduction in particle size with continued hydrolysis in the case of the wood pulp. ELECTRON MICROSCOPY
Preparation of Specimens. A dilute aqueous suspension of each sample was treated with ultrasonic waves (22 kc., about 1
wave/sq. em.) for 1 hour in order to disperse the material as much as possible. The samples n-ere then deposited on a phosphor-bronze grid covered with a film of Zapon lacquer (cellulose nitrate) or Formvar (polyvinyl formal) and shadowed using an alloy of gold-manganese (1 to 1 by Keight). Effect of Hydrolysis on Particle Size. Figure 4 shows electron micrographs of samples &I 1 and M 4, respectively (exposures with a Siemens electron microscope 1939, Type EM 100, operated a t a setting of 100 kv.). Prolonged hydrolysis did not change the appearance of the samples in the electron micrographs. I n order to examine the effect of the hydrolysis on the dimensions of the particles shown in the electron micrographs, the width (apparent diameter) and length of the micelles (rodlike particles) were measured on a microcomparator. The measurements were all performed on the original plates (magnification 8500 X Ilt 2%). For each sample, measurements R-ere made on three different plates of the highest resolution (well in focus) and in different directions on each plate to obtain a representative measurement. The results of the measurements of the number-average particle width and the number-average particle length are tabulated in Table I for comparison with the number-average length of the molecules obtained by multiplying the DP, from osmotic measurements by the length of the glucose unit (5.15 A.). The molecule lengths obtained by the two independent methods are comparable if n-e assume that the primary particles are bundles of unbroken straight chain molecules. In Table I the two lengths check as well as could be desired, indicating that the above assumption is really justified because the length of the micelles corresponds to the length of the cellulose molecules. Figure 5 shows the frequency distributions of the length measurements for the wood pulp (top) and the cotton (lower) a t 80% and 15% residual cellulose. It appears that the cotton sample has a wider distribution curve than the wood pulp and that there is no perceptible shift in the distribution curve for the cotton sample with prolonged hydrolysis. With the length distribution curve of the wood pulp sample there appears to be only a very slight shift toward shorter lengths, the significance of which is doubtful. Each curve represents 120 individual particles measured and on the figure, the ordinate,
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-
(lower) samples. The width-distribution curves and averages were obtained in a similar manner as described above for the particle length. Here, there is a considerable shift in the distribution curve of the wood pulp toward lower width rvith increasing extent of hydrolysis. The corresponding curves for the cotton cellulose show no perceptible shift. The average width is also tabulated in Table I and although the absolute values may not be sufficiently certain (the resolution in the electron micrographs is 30 to 40 A4.), the average width of the wood pulp micelles decreases by about one fourth during hydrolysis from SOY0 t o 15YGresidual cellulose. The corresponding change in the width of the cotton micelles is insignificant. KO part'icle thinner than 50 A. was found in accordance with previous measurements of R h b y ( 2 2 ) . The particle widths were also of the same order of magnitude ($93). The widt,h distribution appears t,o become narrower wit,h continued hydrolysis wit,h both t,he cotton and the wood pulp samples.
PARTICLE LENGTH DISTRIBUTION (WOOD PULP)
N
- M1 -0-
M3
PARTICLE LENGTH DISTRIBUTION (COTTON)
20 N /
---
a
OPTICAL MICROSCOPE
M4
In order to study the effect of the prolonged hydrolysis on fine structure a t a higher magnitude level, photographs of the different
M6 e e * *. Smoothed curve 10
PARTICLE WIDTH DISTRIBUTION (WOOD PULP)
---
20
200
300
4 00
500
600
700
LinA
800
M1 MP
900 N
Figure 5 . Particle length distribution curves of hemlock pulp (top) and Empire cotton (bottom), respectively, at 80% and IS% residual cellulose N = number of measured particles w i t h lengths within a 30 A. interval
A T J represents the number of particles with lengths within 30 A. interyak. These measurements of the micelle dimensions mere difficult to perform. Only straight particles with both ends visible were measured, and by a strict application of this principle only 10 to 20Yc of all particles present could be included, and no particles longer than 900 A. -cere found. The main difficulty r a s caused by the aggregation of the particles. The average dimensions of the measured particles are in agreement with measurements by Vogel(28) for ramie hydrolyzed by boiling 2 . 5 5 sulfuric acid. The values obtained, however, do not agree with data of hIorehead ( 1 6 ) who reported average particle lengths of 1460 and 1450 A. for cotton and wood pulp samples hydrolyzed in boiling 2 . 5 N hydrochloric acid from measurements on clcctron micrographs. The corresponding DP values n-ere 280 and 297, respectively, from viscosity measurements. Morehead ( 2 6 ) did not report particles shorter than 910 A,, and no length distribution curves were presented. Furthermore, DP values of Morehead are all derived from viscosity measurements in cuprammonium solutions and therefore dependent upon the K , const,ant used. No absolute DP measurements were oerformed by Morehead ( 1 6 ) , and a redetermination of the K,, constants for cellulose in both cuprammonium and copper ethylenediamine (Cu en) solutions would be of interest. Figure 6 shows the frequency distribution curves for the particle width measurements for the mood pulp (top) and the cotton
10
0
0
50
100
150 w i n
PARTICLE W I DTH 0 ISTR I BUT ION (COTTON)
200
a
---
M4
20
.a....
M5 M6
N 10
0 0
50
100
150
20 0
Winb
Figure 6. Particle width distribution curves of heinlock pulp (top) and Empire cotton (bottom), respec,tively, at 80,40, and 15% residual cellulose
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July 1956
Figure 7.
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Optical micrographs of hydrolyzed hemlock pulp at 8Oq0 (left) and 15% (right) residual cellulose, respectively Magnification 2 X 182 = 364 X
cellulose samples were taken with an optical microscope equipped with a plate camera. The specimens were prepared in the following way: the aqueous suspensions of the cellulose samples were shaken by hand (no ultrasonic irradiation was used in order to avoid particle disintegration); a drop was then transferred from the suspension by means of a glass rod onto the microscope slide and a cover glass was placed on top. Evaporation was prevented by covering the edge of the cover glass with Vaseline. Whereas the effect of hydrolysis could hardly be detected from a visual comparison of the electron micrographs (Table I), the optical micrographs clearly show the effect of the prolonged hydrolysis. Furthermore, the optical microscope shows a distinct difference in the appearance of the cotton and the wood pulp samples.
Figure 8.
Figure 7 (left) is a photograph of sample M 1 (hemlock pulp 80% residual cellulose) a t a magnification of 364 X. The material consists of a number of rectangular particles (fiber segments) of a width of about 30 to 50 microns and a length varying from about 75 to 200 microns. These particles seem to be made up of rodlike fibrils oriented parallel with the longitudinal axis of the particles. These rodlike fibrils are about 5 to 7 microns wide. The fiber segments also show transversal subdivisions or cracks a t intervals of roughly 50 microns. Figure 7 (right) shows sample M 3 (hemlock pulp, 1.5% residual cellulose). The rectangular particles have disappeared completely and large aggregates consisting of small fragments of dimensions of the order of 1 micron were found. Figure 8 (left) shows sample M 4 (Empire cotton, 80% rcsidual cellulose). Like with sample M 1 a number of rectangular
Optical micrographs of hydrolyzed Empire cotton at 80% (left) and 15% (right) residual cellulose, respectively Magnification = 364 X
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Figure 9. Optical micrographs of hydrolyzed hemlock pulp (left) and Empire cotton (right), respectively, at 80% residual cellulose Magnification 2 X 460
fiber segments were found, but on the n-hole they are longer, thinner, and with better defined contours than those of the wood pulp. The subdivisions are less apparent, the particles seem to be covered by a skin which shows irregular t,ransversal wrinkles or cracks a t different angles t,o the fiber axis. The rectangular fiber segments have a R5dth of about 20 t o 35 microns and a length varying from about 50 to 250 microns. Rodlike fibrils may also be distinguished, which are about 3 to 4 microns vide. Figure 8 (right) shows sample 11 6 (Empire cotton, l50/, residual cellulose) and here, similar to &I 3, large aggregates consisting of small fiber fragments of dimensions of the order of magnitude of 1 micron were also found. The aggregates show a somewhat better over-all regularity than the aggregates of h l 3. Figure 9 represents characteristic particles of b1 1 and AI 4, respectively, photographed a t a magnification of 920 X . Figure 9 (left) shows the rodlike fibrils and transversal cracks of a henilock pulp fiber, whereas Figure 9 (right) illustrates the mbdivisions, sharper contours, and skinlike sheath (primary walls of the fibers) found with the Empire cotton (5, 23). DI SCCTS S I 0 3
The experimental evidence regarding the effects of hydrolysis of t,he hemlock pulp and the Empire cotton samples is summarized in Table 11.
Table 11. Effect of Hydrolysis From SO% to 15% residual cellulose Dimensions of Mol. Wt. Primary X-Ray (Osmotic Particlesa Diffraction Fiber Sample Pressure) (Micelles) Pattern Fragxnentsb Hemlock Decreases Decrease in Widening Over-all dewidth by of refleccrease in pulp by 3091, /1 tions size Empire Constant Constant KO change Over-all decotton crease In size a Electron microscopy. b Optical microscopy.
-
920 X
The effect of hydrolysis of both wood and cotton cellulosea, when studied using optical microscopy, is a general disintegration of the fibers into fragments and a reduction in size of the resulting fragments. On the molecular level, however, the wood and the cotton celluloses show different behavior. The primary particles (micelIes) of the cotton celluIose remaining after the initial rapid hydrolysis appear to be resistant' to further breakdown during the prolonged hydrolysis. The heterogeneous hydrolysis in this case is a first-order reaction (16). For the initial rapid hydrolysis, however, a zero-order kinetics has been found ( l e ) . The mechanism of the disappearance of material in this case seems therefore to be one where a particle is either left unattaclced or rapidly degraded and removed completely as already suggested by Saeman and others (15). -4kinetic treatment, for such a process might be derived from work by Simha ( I d , 27). On the other hand, the primary particles (micelles) of the wood cellulose show a gradual decrease in width indicated both by direct nieasurements on the electron micrographs and by the widening of the x-ray reflections. Furthermore, the cellulose chains making up the remaining particles are depolymerized as evidenced by the decrease in molecular weight. This is likely to happen in the surface layer of the primary particles. In cotton cellulose no such attack has been found which probably is due to its higher lattice perfection (Figure 3) resulting in strong interchain bonding. I t is well kn0n.n from mercerization experiment,s ( 8 2 ) that the less perfect lattice of wood cellulose is less resistant against alkali swelling than that of cotton cellulose. As a conclusion, the data from hydrolysis and mercerization and from direct x-ray analysis indicate that wood cellulose has a lattice of lon*er perfection and that it is therefore more susceptible to chemical attack. It is of interest to note that wood cellulose degrades with a higher rate than cotton cellulose also in homogeneous acid hydrolysis, where the cellulose is molecularly dissolved (6, 8). It is possible that chemical irregularities in the wood cellulose chains could be the reason bot,h for the higher rate of homogeneous hydrolysis and for the lower lattice perfection. The difference in behavior betmeen wood and cotton cellulose as outlined is in agreement \Tit11 previous findings also of other authors (3, 7 , 8, 25).
July 1956
INDUSTRIAL AND ENGINEERING CHEMISTRY SUMMARY
This investigation of the heterogeneous hydrolysis of native cellulose fibers was primarily performed to study structural differences between the resistant portions of wood and cotton fibers. The heterogeneous hydrolysis of the fibers with constantboiling hydrochloric acid can be subdivided into an initial rapid process and a subsequent slower first-order reaction which was studied from SOY0 to 15% yields of residual hydrocellulose. The initial fast hydrolysis of both cotton (dewaxed Empire cotton) and wood (chemical grade sulfite pulp from hemlock) fibers involves a decomposition of the elementary cellulose fibrils (micelle strings of about 100 A. in width) into shorter rodl’ike fragments (micelles) giving sharper x-ray reflections than the original fibers. The initial hydrolytic attack studied with optical microscopy proceeds preferentially along certain cleavage planes in the fibers, giving irregular coarse fiber fragments. The following slow hydrolysis ofcotton cellulose to yields of 15% does not decrease the osmotic DP, of the hydrocellulose, gives no change in the size of micelles (measured on electron micrographs), and no change in the x-ray reflections. For the wood pulp, o n h e other hand, the slow hydrolysis to 15y0yield decreases the DP, by about 30%, reduces the width of the micelles by one fourth and increases the width of the x-ray reflections by about 15%. It was observed with the optical microscope t h a t the hydrolysis to low yields of both cotton and wood pulp causes a very marked gradual decrease in the size of the fiber fragments down to about 1 micron. From these results the mechanism of the heterogeneous hydrolysis of wood and cotton cellulose appears t o be different. The more resistant cotton cellulose micelles seem to remain unchanged until they disappear by a rapid process, whereas the wood cellulose micelles show a gradual lateral attack during the hydrolysis reaction. This indicates a basic difference in chemical resistance between native wood and cotton cellulose. ACKNOWLEDGMENT
The authors are much indebted to J. F. Saeman, Forest Products Laboratory, Madison, Wis., for preparing the hydrocellulose samples used. This investigation has been supported by a research grant from the Swedish Technical Research Council (Statens Tekniska ForskningsrLd) which is gratefully acknowledged. LITERATURE CITED
(1) Battista, 0.A.,IND.ENG.CHEM.,42, 502 (1950). (2) Dymling, E., Gierts, H. W., Rhnby, B. G., Svensk Papperste’dn. 58, 10 (1955). (3) Hartler, N., Samuelson, O., Ibid., 55, 851 (1952). (4) Hermans, P.H., Weidinger, A., J . Polymer Sci. 4, 317 (1949). (5) Hock, C. W., Textile Research J . 20, 141 (1950). (6) Immergut, E . H., Rhnby, B. G., Mark, H. F., Paper presented
at the International Symposium on Macromolecular Chemistry, Milano-Torino, September 1954. Ricerca Sci. 25 (1955). (7) Jorgensen, L.,A c t a Chem. Scand. 4, 185,658 (1950). (8) Jorgensen, L.,“Studies on the Partial Hydrolysis of Cellulose, dissertation, Oslo, Norway, 1950. (9) Linderot, J., Svenslc Papperstidn. 59, 37 (1956). (IO) Lovell, E. L., Goldschmidt, O., IND. ENG.CHEM.38,811 (1949). (11) McBurney, L. F.,in E. Ott, H. M. Spurlin, and M. W. Grafflin, ed., “Cellulose and Cellulose Derivatives” 2nd ed., part I, chap. I11 C, Interscience, New York, 1954. (12) Madorsky, S. L.,J . Polymer Sci. 9, 133 (1952); 11, 491 (1953). (13) Mehta, P. C., Pacsu, E., Textile Research J . 18, 387 (1948); 19, 699 (1949). (14) Meller, A.,J . Polymer Sci. 4, 619 (1949);10, 213 (1953). (15) Millett, M. A.,Moore, W. E., Saeman, J. F., IND. ENG.CREM. 46, 1493 (1954). (16) Morehead, F. F., Textile Research J.20, 549 (1950). (17) Nelson, M. L.,Conrad, C. M., Ibid., 18, 149 (1948). (18) Nickerson, R. F., IND.ENG. CHEM.33, 1022 (1941);34, 85, 1480 (1942). (19) Nickerson, R. F., Habrle, J. A.,Ibid., 37, 1115 (1945). (20) Purves, C. B., in L. E. Wise and E. C. Jahn, ed., “Wood Chemistry,” 2nd ed., vol. I, pp. 182-205, Reinhold, New Y o r k , 1952.
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(21) ROnby, B. G., Acta Chem. Scand. 6, 116, 128 (1952). (22) Rhnby, B. G., “Fine Structure and Reactions of Native Cellulose,” dissertation, Uppsala, 1952. (23) Rollins, M. L.,Tripp, V. W., Teztile Research J . 24, 345 (1954). (24) Roseveare, W. E.,IND.ENG.CHEM.44, 168 (1952). (25) Samuelson, O., GrangLrd, G., Jonsson, K., Schramm, K., Svensk Papperstidn. 56, 779 (1953). (26) Sharples, A.,J . Polymer Sci. 13, 393 (1954). (27) Simha, R., Trans. N . Y . Acad. Sci. 14, 151 (1952). (28) Vogel, A.,J . makromol. Chem. 11, 111 (1953). (29) Zimm, B. H., Myerson, I., J . Am. Chem. SOC.6 8 , 911 (1946). RBCEIVED for review June 10, 1955. ACCEPTED February 29, 1956. Division of Cellulose Chemistry, 127th ACS Meeting, Cincinnati, Ohio March-April 1955. ~
~~
Corrections The editors regret that, in the final printing, the references for ENG.CHEM.48, 797 (April 1956)] were both corrections [IND. interchanged. Once again, the editors are printing these corrections as they should have appeared. I n the article entitled “Sizing Pipe for Flow of Cellulose Acetate Solutions” [F. L. Symonds, +4.J. Rosenthal, E. H. Shaw, IND.ENQ.CHEM.47, 2463 (1955)], Equation 10 on page 2464 should read D A p / 4 L = 32gp(/uD3 I n the article entitled, “Stearato Chromic Chloride’’ [R. K. Iler, IND.E N G .CHEM.46, 766 (1954)], U. S. Patent number in literature cited (6) on page 769 should be
U.S. Patent 2,307,045 I n the article entitled “Granulated Fertilizers” [H. W. Haines, Jr., Fremont Lange, IND. ENG. CHEM. 48, 966 (1956)], the figure on page 967 should be replaced with the following drawing:
U.S. Consumption of Plant Nutrients and Fertilizers I>
(Million Tons)
Source
USDA
20
15 10
5 5 The top line of each shaded a r e a is the actua1:consurnption d a t a
I n the article entitled “Liquid Propellant Handling, Transfer, and Storage” [P.M. Terlizzi, Howard Strem, IND.ENQ.CHEW 48,774 (1956)], t h e following correction should be made: On page 776, column 2, the third paragraph, line 4, General Motors Corp. should be changed to read GMC-type canister
