1518
INDUSTRIAL AND ENGINEERING CHEMISTRY
An important recent advance which has already received much attention in the literature is the use of a chemical which reacts with the textile fiber in such a manner as to form a water-insoluble complex. The material is a long-chain quaternary ammonium compound (9). I n textile applications the fabric is immersed in water solution of the chemical so that about 6 per cent of the substance is deposited. The fabric is then dried quickly in a low-temperature air blast of 200" E'. The fabric, however, does not become warmer than 100' F. A heating or curing operation is next in which the now dry cloth is subjected to a 3-minute heat treatment a t 300" F. It is during this period that the compound breaks down and forms the water-insoluble complex which confers the water repellent effect upon the goods. The final step is a washing operation which neutralizes the slight residual acidity on the fabric and removes unreacted and by-product compounds.
Vol. 33, No. 12
Literature Cited (1) Furry, M. S., Robinson, H. M., and Humfeld, H., IND.ENQ. C H E M .33, , 538 (1941). ( 2 ) Hubert, E. E., Ibid., 30, 1241 (1938). (3) Jackson, L. E., and Wassel, H. E., Ibid.. 19, 1175 (1927). (4) Jones, H. I., U.S. Patent 1,921,926 (Aug. 8, 1933). (5) McGill, W. J., Ibid., 1,854,948 (April 19, 1932). (6) Minaeff, M. G., and Wright, J. H., IND. ENG.C H E M .21, , 1187 (1929). (7) Prescott, S. C., and Dunn, C. G., "Industrial Microbiology", 1st ed., New York, McGraw-Hill Book Co., 1940. (8) Roark, R. C., and Busby, R. L., U. S. Dept. Agr., Bur. Entomology and Plant Quarantine, 1st. 2nd, 3rd Indices of Patented Mothproofing Materials, 1931, 1933, 1936. (9) Slowinske, G . A., Am. Dyestuff Reptr., 28,647-50 (1939). (10) Stringfellow, W . A., Ibid., 29, 266 (1940). (11) TeztiZe Colorist, 63, No. 747, 164 (1941). (12) Tyner, H. D., IND. ENO.C H E M .33, , 60 (1941). (13) U. S. Dept. Agr., Leaflet 101 (revised June, 1936).
Cellulose from Hardwoods Wood Pulp Purification GEORGE A. RICHTER' Brown Company, Berlin, N. H.
P
REVIOUS papers in this series dealt with the chemical and physical properties of New England hardwoods (2) and described their behavior when pulped with acid sulfite liquors (3). This paper describes the processing of such unbleached pulps to yield substantially white fibers with a variety of property combinations that have value in the paper industry and for esterification. So that their behavior may be compared with more widely known wood pulps, comparison treatments and tests for corresponding softwood pulps are frequently cited. Most of the discussion has to do with pulps produced when the respective woods are digested with sodium bisulfite cook liquors; it has been found impractical to use the all-calcium base liquors satisfactorily with some of the hardwood species. Table I gives typical values of unbleached wood pulps obtained when the several unseasoned wood species were chipped and digested in acid liquors that contained 5 per cent free and 1 per cent combined sulfur dioxide (defined in the previous article, 3), where the liquor volume was such that 6 per cent combined sulfur dioxide was present, based on wood. I n each case the cook schedule prescribed an increase in temperature from 25' to 140' C. in 4 hours and a maintenance a t that level for 4 hours. Maximum gage pressure was held a t 85 pounds by causing some gas escape from the digester. Tests given are representative of pulps prepared from wood chips produced with a large rotary knife chipper (3). When the raw stocks of Table I were bleached by a sequence that comprised chlorination followed by oxidation with hypochlorite, the bleached pulps took on the characteristics listed in Table 11. Results in Tables I and I1 may be summarized as follows: 1
Present address. Eaatman Hodak Company, Rochester, N. Y.
Unbleached hardwood pulps can be processed to yield substantially white products that possess properties and chemical composition suitable for esterification and for conversion into stable papers. Means are given for the elimination of resinous bodies and for the extraction of pentosans and nonalpha-cellulose constituents. All procedures cited are accompanied by parallel treatments made with the better known softwood pulps. Occasional reference is made to the purification of the kraft pulps although the discussion is confined for the most part to treatments of stocks prepared by the acid sulfite cooking process. No attempt is made to indicate preferred commercial procedures inasmuch as a chosen purification sequence depends largely upon local conditions and the outlets for which the end product is intended.
1. As shown in a previous article the unbleached hardwood pulps are richer in pentosans and lower in papermaking strength than the softwood ulps. This difference carries through to the bleached pulps ma$ by the sequence iven. 2. There is a distinct tendency for the hardwood pulps to have lower solution viscosities when dissolved in cuprammonium reagent than is found with the softwood products. This same relation holds in the case of the bleached pulps. 3. Although the maple and the beech pulps have low percentages of extractables, the birches (particularly the white birch pulps) are characterized by high ether-soluble content. In all
December, 1941
AND
INDUSTRIAL
ENGINEtRING CHEMISTRY
1519
cases the bleached pulps maintain the same relative position, but it is evident that reduction of ether-solubles in white birch pul with this articulat bleach sequence is mu& less maged than with the spruce and the fir pulps. Later work discloses more suitable bleach procedures for the hardwood pulps. 4. The alpha-cellulose levels of the hardwood and the softwood raw stocks are about the same, although in the case of the hardwood pulps the alpha-cellulose residue as prepared in the analysis contains appreciably higher amounts of pentosans than with the softwood fiber. Bleaching as here prescribed raised the alphacellulose of all pulps, both because of elimination of some pentosan groups and lignin and because of some solvent action of the free alkali on hemicellulose. 5. Each of the pulps reached substantial whiteness. The softwood and the beech pulps consumed somewhat more of the bleaching reagents than did the other varieties. I n general, the hardwood pulps bleached by the sequence described above are inferior t o the softwood pulps, both in respect to papermaking properties and ether-soluble content. The white birch product approaches most closely the physical strength of the conifer pulps but is the worst offender in respect to resin content. On the other hand, the shorter fiber of the beech and the maple permit only a limited usage by the papermaker even though their resin content is well below the maximum allowable. Earlier work had shown that some reduction in resins can be achieved by aging the wood for several months before it is ahipped and cooked, but unfortunately the advantage as reflected in the unbleached stocks does not carry through to the same degree in the bleached products. I n other words, of the resins found in the unbleached stocks, a lesser percentage is removed by bleaching in the case of pulps from seasoned
A SCALING OPICRATION JUST BEFORE HAULING WOOD
wood. Hence only part of the advantage of aged wood is realized in the white fiber, and with the white birch the net result is but little better than that recorded in Table 11. Furthermore, since it is costly to separate white birch from mixed stands of hardwood, i t becomes necessary to find processing steps for effectively extracting the resinous bodies from the white birch so that the entire outting can be used successfully. This can best be done by application of one or more special treatments of the stock before or during the refining steps by which the pulp is converted into a white fiber.
TABLEI. UNBLEACHED SULFITE PULPSFROM UNSEASONED WOODSPECIES White Birch 116 138 1.5
Bursting atrengthb Tear resistance Lignin. %
Yellow Birch 90 115 1.2
Rock Maple 90 100 0.9
Beeoh 78 100 1.3
Spruce 145 160 1.2
1.1
Mixed Hardwooda 100 105 1.2
Mixed Hardwood
Fir 135 180
poisee birch, rock maple.
~~
TABLE11. BLEACHED PULPTESTS” White Birch Brightnesu by G. E. instru-
ment. 89 BGz-ii~ strength 106 Tear resmtance 132 Pentosana. Q 7.2 Ether-sol.,’ 2.4 Acid-aloohoFsol., % 0.50 Hot-water-sol., % 0.30 Cuprammonium viscosityb. 3.0 89.4
Yellow Birch
Rock Maple
Beech
Spruce
Fir
88 89 112 6.8 1.3 0.32 0.60
89 86 80 6.2 0.30 0.24 0.63
87 72 86 6.1 0.42 0.30 0.48
89.5 136 165 4.2 0.50 0.42 0.40
89.6 128 178 3.8 0.48 0.39
0.61
88.8 88 92 6.5 1.2 0.54 0.30
2.9 89.2
2.8
2.6 88.8
15.0 89.1
12.6 89.4
2.9 89.1
88.6
0 Pul 8 bleached by aequence. chlorine baaed on pul 20° C 1 hr * ( B ) 67’ aodium beach baaed on ulp, pH l&, stock, 86’ C., 6 hr. (b%aoh o a i h a t e d on usual basis of 35% ~~. .~ ..,- available .~~ ..... o&orine). .~ ..-....-,. b By AMERICAN CHEMICAL SOCIETY method.
MECHANICAL REMOVAL OF RESINOUS FINES Much of the ether-soluble material is adsorbed or contained in the very short fibers of a wood pulp composite. These short fibers and fiber fragments are called “fines” and can be removed from the pulp mass by spray washing under conditions that will allow the resinous fines to leave the system with the effluent water. I n the case of unbleached hardwood pulp, these fines contain four to eight times as much ethersolubles, nearly twice as much acid-alcoholsoluble wax, and fully three times as much lignin as the original pulp from which the fines were removed. Only about one third of the resins that are so concentrated in the fines are saponifiable. The resinous fines are dark brown and very difficult to bleach. Both hardwood and softwood pulps respond to such deresinification, although in the case of the softwood pulps considerably less fines need be removed to effect a given reduction in resin. This may be explained by a sharper distinction in fiber length. The difference may be illustrated by Table I11 and Figure 1. I n this set of experiments the fines yere removed by causing water and fines to flow through a 100mesh screen from a thin stock suspension, under conditions where a vigorous agitation of the thin suspension prevented the formation of a filtering web on the screen.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
1520
on saponifiable material in the extractables, but it is probable that reduction of surface tension is a more important factor since certain nonalkaline wetting agents act similarly and much of the extractable material is unsaponifiable. The commercial success of fines removal from unbleached sulfite pulps before they are subjected to the bleaching steps depends upon the local unit costs and price levels. Loss of total yield must; be more than offset by net savings in the process for it to be of economic value. The process has been used successfully with softwood pulps which suffer less loss in yield but does not appear practical for the hardwood fiber except where, because of quality improvement, a substantial increase in price will compensate for the greater loss of fiber. Although resin reduction by fines removal can also be applied effectively to the pulp after bleaching, there is more to be gained by deresinifying the raw stock; the fiber losses are then confined to the less costly fiber, and appreciable savings are made because of the improved bleachability of the pulp that has been rid of hard bleaching residues (Table IV).
BY REMOVAL OF FINES TABLE111. RESINREDUCTION Short Fiber Removed,
EtherSol. in Original Pulp, % ' 1.20
Unbleached Sulfite Pulp Used Mixed hardwood
% 0 2
Bleach Reauirements to Rearh G. E. Ether-Sol. Ether-Sol. Brightness of in Cleansed in Fines, go,,% Cl. Fiber, % 3' % Equivalent 5
o:i1
4
1.15
Spruce and fir
4 8
Spruce and fir
0.86
0 2
4
8
0.58
5.4 4.6
4.2
4.5
0166 0.40 0.20
6.8
0:io
5. '4 5.3 4.8
4.0 6.0 5.0 4.5 4.5 5.5
0.35
8 0 2
,
0.33 0.16
5.7 5.0
Vol. 33, No. 12
4.0
5.0
4.5 4.0
I n another instance a hardwood raw stock obtained by cooking a mixed hardwood containing all four major varieties was spray-washed on a 100-mesh screen to remove 6 per cent fines. Changes in ether-solubles and lignin are shown in Table IV.
DETERGENTS
Detergents, if properly applied, are effective in reducing the resinous matter that is regularly present in both the softOF FINES FROM UNBLEACHED HARDWOOD wood and the hardwood pulps. Here again, however, the TABLEIV. REMOVAL SULFITE PULP nature of the resinous material in the hardwoods makes it apEther-Sol., % ' Lignin, % preciably more difficult to remove than with the softwood 2.4 Original pulp 1.00 pulps. Inasmuch as the detergent is more advantageously 1.88 Pulp after spray washing 0.39 6.6 Fines 5.56 applied in the presence of some free alkali, it is probable that the higher percentage of saponifiable matter in the softwood resins helps to explain its easier removal. The detergent may be applied a t any of several stages in the processing sequence. The important points of application are (a) in the unbleached fiber, possibly after fines removal but before any bleaching or other chemical refining steps, (b) simultaneously with alkaline refining that aims to raise the alpha-cellulose, and ( c ) in the bleach treatment itself.
I
I
I
I
Detergents with Unbleached Fiber. Detergents are best applied a t slightly elevated temperature and at sufficiently high stock density to favor mass scrubbing when agitated. Table V comprises typical data when both hardwood and softwood pulps are so treated. In these treatments the unbleached stock was used a t 8 per cent consistency, the temperature was 50' C., and the mixing was continued for 2 hours. The fiber was then washed with special care to avoid fiber loss. The results in Table V show substantial reduction in extractable5 although, in the cases cited, the treatment in itself does not yield a pulp with sufficiently low resin content to be acceptable by the industry. This is particularly true when the ultimate product is intended for esterification since for that purpose ether-solubles in excess of 0.2 per cent are for the most part objectionable. Raw stock treatments as here described should be applied in conjunction with other steps that give the resultant additive effect desired. The less favorable response of the hardwood fiber is apparent,
eliminated with the fines is influenced by the presence
the fiber greatly improve the effectiveness of the removal. I n one instance a 4 per cent rejection of fines in the absence of alkali caused a reduction of ethersolubles from 4.2 to 0.5 per cent, whereas the latter figure was further reduced to 0.32 per cent when sodium hydroxide was added to the extent of 0.01 per cent in the water in which the fiber was suspended. Some of the improvement may be ascribed to a solubilizing effect
J
TABLEV. USEOF DETERGENTS WITH UNBLEACHED PULPSO Per Cent Ether-Soluble Matter 27
2%
NadOa Sulfite Pulp
~
Water alone
$
g::
~
N?zOa
$
$e!
;~0:
?i:
~aaP04 $e!
Ii8220r
~ :$:
~
;0:
f?
~
0.1% NaOH alone
:;0:
-
EaJ 'i
+red0 3% 011
$.:
a All inorganic reagents expressed as percentage solution: red oil percentage based on fiber. b Original ether-soluble content 0 98 Original ether-soluble oontent: 6962: P
I
I N D U S T R I A L A N D E N G P N E E R I N G CaHEMISTRY
December, 1941
Detergents in the Presence of Hot Alkalies. When sulfite pulp is to be refined to a high alpha-cellulose level, it is usually expedient to add the detergent to the alkali that is employed for removing the hemicellulose groups. The step is frequently carried out above 80' C., and very small amounts of detergent are required. Table VI cites several examples of conditions that may be employed and of results obtained. IN PRESENCE OF TABLEVI. ALKALINEREFINEMENT DETERGENTS Conditions of Second Treatment-8p stock Same, plus 100 C. 4 d Same, plus 1 0 7 red oil 12% NaOH' 1 . 0 7 red oil based on pulp base$ on pulp based on pulp basel on pulp Softwood Sulfite Pulp5 0.16 0.20 0.30 0.38 8% stock, 80° C.. 4 hr., 5% NaOH
Ether-sol., yo Yield e-CeiiuEse, %
91.6 91.2
.
91.5 91.1
86.0 94.8
86.1 94.6
Hardwood Sulfite Pulpb Ether-sol., % 0.46 0.25 0.38 0.19 Yield, % 90.2 90.2 85.2 55.0 a-Cellulose. % 91.7 91.8 94.5 94.2 ether-soluble6 0.94'%0' rr-cellulose 88.6%. Pulp 4 Unbleached pul prebleached with 688odium bleach bised on dulp at 25' C: a-cellulose 85.3%. Pulp b Unbleached pulp: ether-aolubles, 0.98%; Drebleached with 6% sodium bleach based on pulp at 25' 6.
Although many of the commercial sulfonated naphthalenes and the long-chain aliphatic alcohol sulfates have been used more or less successfully, fatty acids of either vegetable or animal origin have proved satisfactory as the detergent base. The alkali present in the mixture converts the fatty acids to
Rock maple
Red spruce
1521
soldde soaps which are very effective under the chosen conditions. The higher fatty acids are generally suitable. Red oil, sulfonated fatty acids, stearin, and pine ails obtained as a by-product in the recovery of pine resins from the spent liquor of a kraft pulping operation are suitable for most purposes. When the temperature of treatment is sufficiently high to saponify a fat or if the fat is first saponified, i t can also be used successfully. The saponifiable portion of the ether-solubles present in the pulp adds to the detergent effect of the material that is deliberately added to the alkali. As shown in Table VI, relatively small quantities of the detergent are needed to bring about a major reduction in ethersolubles.
Detergents in Bleach Step. When conditions permit, the detergent can be used with a fair degree of success by adding it to the stock during the final bleaching operation. This can be satisfactorily accomplished only if the fiber mixture is held on the alkaline side when both bleach and detergent are present. Substantial absence of alkaline earth residues is important, and when hypochlorite is used as the bleaching agent, one must substitute sodium for the more common calcium-base liquor. Frequently secondary reagents are added with the detergent to assure less interf&ence by unavoidable calcium contaminants that may be present. Phosphates and carbonates are so employed. Detergents are used in the bleach process generally when the pulp has had no prior alkaline treatment designed to raise the alpha-cellulose content. When alkaline refinement is carried out, it is simpler and more effective to add the detergent in that step. Moreover, at the higher tempera-
Beech
Yellow birch
Balsam fir
White birch
WOODCELLULOSE FROM VARIOUSSPECIES tx 66)
INDUSTRIAL AND ENGINEERING CHEMISTRY
1522
tures employed, lesser amounts of detergents may be used to attain a desired reduction in resins. Table VI1 includes figures to illustrate the behavior of the detergents in the bleach step. I n this set of experiments the pulps were first treated with 6 per cent sodium-base bleach based on pulp at 20" C. for 1 hour. The prebleached stock was washed and then subjected to the second bleach step as indicated. Prebleach was used rather than prechlorine, since the use of free chlorine with hardwood pulps prevents good removal of resin in subsequent steps, as will be shown later. Aside from the general benefits that result when detergent is added to the bleach mixture, i t is again noted that the ethersolubles in the softwood pulps are more easily removed than from the hardwood fiber. TABLE VII. USE OF DETERGENTS IN FINAL BLEACH STEP Second Bleach A 8 7 sodium Prebieacg 2% B. Same as bleached NaOH based on A 0.4% Sulfite fiber 40° C saponified Pulp 4 hr.,'pH 11:b red oil Softwood= 0.46 0.28 Hardwoodb 0.48 0.34 a 0.S9po ether-soluble content. b 0.9070 ether-soluhlo content.
+
+
Treatment C. Same as A 0.47 Naocanof 0.29 0.35
+
D. 8 sodium bleacx 0.4% saponified red oil, 40' C. 4 hr., p H 7.8 0.38 0.43
+
PROPERSELECTIONOFBLEACHREAGENTSFOR LOW-RESIN PULPS The resins of the hardwood and the softwood pulps behave very differently when chlorinated. Whereas the softwood resins become only slightly more sticky, the chlorinated ethersolubles of the hardwoods (particularly of the white birch) are extremely tacky, and when present in pulp they resist saponification and removal by detergents almost completely. I n fact, chlorination of an ordinary hardwood sulfite raw stock with the usual 2 to 4 per cent application results in a product which, even after subsequent application of detergents, is almost waterproof and resists sinking in water for long periods. These chlorinated hardwood resins are so resistant to saponification that they remain so even when hot, relatively strong alkali is applied. Actual figures in Table VI11 demonstrate the futility of any attempt to remove the OF FREECHLORINE ON SUBSEQUENT TABLEVIII. EFFECT DERESINIFICATION
Ether-Sol., G. E. Sequence of Treatments0 % ' Brightness Softwood Sulfite Pulp (1.1% Ether-Sol. in Unbleached Pulp) 1 (A) 5% chlorine, 20' C 1 hr;; ( B ) 6 7 sodium bleach g H ll'.b, 35 C., 4 hr.' 0.48 89 2 ( A ) 10% s o d i u d leach, p H 8.5, 20' C.; 0.39 88 ( B ) same as 1B 3 (A) sameas 1.4; ( B ) !2ya NaOH, 100' C 4 hr.; (C)3% sodium bleach, pH 11.0; 0.24 90 35O C 4 hr 2% 4 ( A ) eamk' as 12; ( B ) same as 3~ red oil; ( C ) same as 3C 0.12 90 5 ( A ) same as 2 8 ; ( B ) same as 4 5 ; (C) same as 3C 0.08 91 Unbler tched Hardwood Sulfite Pulp (0.92% Ether -Sol. in Unblt?ached Pulp) 6 ( A ) 3Y0 chlorine: ( B ) 67a sodium bleach, H 11.0, 35O C 4 hr 0.88 89.5 7 (AT 8% sodium dieach, p H 8.5, 20" C.; same as 6B 0.45 89.1 (?ame as 6 A . ( B ) 5% NaOH SOo C 8 hr.; ( C ) 4 % sodium bleach,'pH l d 35' C., 4 hr. 0.60 89.8 same as 6 A . ( B ) 127' NaOH 9 (A?.O% red oil, lbOo C., 4 hr.; (C) same as 8C 0.40 90.1 same as 7 A ; ( B ) same as 8B; (C) 10 'Ai!ame as 8c 0.26 90.3 11 (A) same as 7 A ; ( B ) same as 9B; (C) same as 8C 0.18 91.0 12 same as 7 A . (F) same as 9B; ( C ) (Ai.6% chiorine:20 C., 1 hr.; (D)same 93.4 0.20 as 8C a I n all cases chemical is based on fiber. Expt. No.
+
(Ai
+
Vol. 33, No. 12
hardwood ether-solubles that have been exposed to chlorine in the early stages of the refining sequence. Treatments of hardwood sulfite fiber with hypochlorite, on the other hand, have no ill effect on subsequent deresinification. No data are on hand to show whether the hardwood resins resist the oxidizing effect of the hypochlorite or whether when oxidized they retain for the most part their original nontacky properties and respond normally to saponification and cleansing with detergents. Table VI11 reveals that even though chlorination has no marked detrimental effect on the softwood resins, there is some small advantage to be gained by hypochlorite substitution. Unit costs and the importance of high whiteness in the bleached product usually lead to the adoption of chlorine in the refining of the softwood fibers; but from the above it is evident that, when processing the hardwood pulps, chlorine can be used only in limited amounts if a t all. When so used it is best applied after a substantial portion of the resins has been removed by one or more of the methods already described. When in special cases a small amount of free chlorine is highly beneficial to attain highest fiber brightness, it should be added after the stock has been subjected to the hot alkaline digestion in the presence of the detergent. Such a case is given in Table VI11 and yields a product of excellent color, low ether-solubles, and more than average stability. A product so made had a G. E. brightness of 93.4 (ordinary rayon grade of sulfite pulp has a brightness of about 91) and contained only 0.2 per cent ether-solubles. When spraywashed with a removal of 2 per cent fines, the final pulp had a brightness of 93.6 and contained 0.10 per cent ether-solubles. PENTOSANS AND CY-CELLULOSE
It has already been shown that the New England hardwoods contain approximately twice as much of the pentosan groups as the softwoods and that the same relation exists in the corresponding sulfite pulps produced by the usual cook procedures. With both types of wood, slightly less than one quarter of the original pentosan content in the wood appears in the sulfite pulps. Frequently when the pulp is intended for papermaking, the pentosans possess some value inasmuch as they often add to the physical strength of the paper made from the beaten stock. I n some cases-for example, in the manufacture of glassine papers-they are essential. On the other hand, a reduced pentosan content often favors stability of paper, particularly when the original pentosans have undergone a partial acid hydrolysis, as in the sulfite process. Furthermore, by proper choice of reagents used in the reduction of pentosans, the product then resembles cotton or rag in that it produces paper that is less brittle and often has considerably higher tear resistance. There is no convincing proof that the pentosan groups in themselves are detrimental to good reaction or product quality when nitrated or xanthated, but there is ample evidence to show that it is impossible t o obtain satisfactory acetates when the pentosan content remains as high as ordinarily found in either the softwood or the hardwood pulps. I n the viscose proczss strong alkaline solutions extract pentosans from a sulfite pulp, and for this reason high pentosans make for lowered yield of regenerated cellulose. Since alkaline treatments of a sulfite pulp cause a reduction of other nonalpha-cellulose constituents as well as of pentosans, any discussion that deals with the removal of pentosans should likewise consider the increase in the alphacellulose content. It must be stressed, however, that there is no consistent arithmetic balance, since other substances present are also soluble in the alkaline reagents and some methods for removing pentosans also cause a pronounced attack on the alpha-cellulose itself. In view of the fact
December, 1941
INDUSTRIAL AND ENGINEERING CHEMISTRY
1523
used in the industry for a number of years to produce the refined alpha pulps. It applies equally well to softwood and hardwood sulfite products; but as would be expected, it cannot be used successfully with kraft fiber. Caustic soda is ordinarily employed although some attempts have been made to substitute lime, soda ash, and sulfides. Concentrations are maintained a t as low levels as are consistent with good results since, with this process, recovery of alkali has not yet been practiced commercially. I n this type of refining the percentage of alkali based on pulp is more im1. Major adjustments in the liquor composition used in the portant than the concentration of the solution. From 1 to primary pdpingstep. 2 per cent sodium hydroxide solution is commonly prescribed. 2. Treatment of wood ulp with relatively dilute alkali soluUsage based on pulp may vary from 6 to 15 per cent, detions at 50' to 150' C. ?Chis treatment is not effective with kraft or soda pulps. pending upon the degree of refining desired and the history 3. The application of stronger alkaline solutions at ordinary of the fiber to be refined. temperatures or with refrigeration. The treatment can be carried out a t atmospheric pres4. Prehydrolysis followed by alkaline extraction. sure or higher. For a given degree of refinement better yields 6. Digestion with properly chosen acid salts which attack pentosans without appreciable attack on cellulose. are obtained at temperatures close to 100' C. although pento6. Selective extraction with low concentrations of cupramsan reduction becomes more marked a t temperatures upward monium reagent or other swellin reagents. of 125' C. Each successive percentage improvement in 7. High-tem erature hydrofysis (160" to 200' C.) in the alpha-cellulose in the product is accompanied by a rapidly presence of suitatle buffer reagents. increasing rate of sacrifice in yield. Likewise the first-removal of pentosans is easily accomplished with high yield, whereas further TABLE IX. EFFECT OF REDUCED PERCENTAGES OF COMBINED Sn~smr DIOXIDE extraction is more difficult and is attended by TN COOKING LIQUOR ON PENTOSANS AND Q-CELIJULOSE)~ progressively higher shrinkages for each suc-+uruce Chips--White Birchcessive unit removed. This behavior suggests % combined 80s 0.5 0.5 0.4 1.0 1.0 0.5 0.6 1.0 0.4 In Ii uor 1.0 a mixture of whaj might be termed "alpha-, 4.0 6.0 4.0 3.5 6.0 4.0 3.5 6.0 4.0 6.0 Base8 on dry wood beta-, and gamma-pentosans", as assumed with 46 4 6 . 5 4 2 . 1 , 4 0 . 1 4 4 . 1 4 2 . 1 4 3 . 6 4 0 . 1 3 8 . 8 48 Yield % ' 105 143 125 124 95 91 118 103 125 145 Bursdnq strengthb cellulose, and that the raw sulfite pulp contains 146 140 136 148 165 135 230 241 180 160 Tear resistance 88.2 8 9 . 0 8 8 . 5 89.7 8 9 . 8 87.6 8 8 . 4 87.7 8 9 . 1 89.3 a-Cellulose, some of each. The hydrolyzed hemipentosans 4.1 6.1 7.9 3.1 2.7 2.2 2.0 4.2 8.6 3.1 Pentosans, are readily attacked by alkali whereas the more A. C:8.viscosity. poises 80 20 60 18 12 25 15 21 12 9 resistant portion behaves in much the same a All cooks made with wide that contain 6% free SO. maximum preeaure 75 Ib. Temmanner as does alpha-cellulose. More drastic r t u r e brought to 140° C. in 6 hours and held there 4 hours. Chips made in laboratory rom reen wood treatment as brought about by higher temb A% beatings bere in ball mills for 50 minutes. peratures or more alkali causes some further attack on the resistant pentosans but also degrades alpha-cellulose a i d thus accounts for abnormally high losses in yield. Effect of Acid Cook Liquor Composition on Pentosans. By adjusting the composition of the sulfite If we regard the pentosans in hardwood pulps as being composed of the resistant and the less resistant groups, it cook acid, one can produce pulps that have lower pentosans and higher alpha-cellulose. This can be done by adopting a helps explain the higher percentage of pentosans in the residue of an alpha-cellulose determination than is found in the case cook liquor that is lean in combined sulfur dioxide, both in of the softwood pulps. Reduction of pentosans to less than terms of liquor concentration and percentage based on wood; 3 per cent in the hardwood pulps is appreciably more difficult i t is illustrated strikingly in Table IX. The results emphawith dilute alkaline digestion than with the corresponding size the importance of a reduction in the ratio of combined softwood fiber. Yields are also less. sulfur dioxide to wood, and it is obvious that this is done Several experimental data are given in Table X to illusautomatically if its concentration in the liquor is lowered without changing the liquor-chip ratio. The better removal trate quantitative relations of yield and degree of refinement attained. I n certain instances the hot alkali was applied to of pentosans can be explained by the presence of more of the the unbleached fiber; in other cases pretreatments were stronger sulfonic acids that are formed during the cook and made to remove lignin so that the final bleach step beyond the are not wholly buffered by the combined sulfur dioxide when it is there in lesser quantities. Lower solution viscosity of alkaline digestion need be less severe to reach a high degree of brightness. Table X shows that: the pulp with the low combined sulfur dioxide suggests some interesting speculation regarding the relation of chain length, 1. For given treatments, softwood pulp yields are higher. chain length distribution, and alpha-cellulose properties, in 2. Pentosans are more difficult t o remove from hardwood view of the fact that the lower viscosity values are accomstocks. panied by higher alpha-cellulose. The higher alpha-cellulose 3. Whereas the tear resistance improves markedly with alkaline refinement of softwood fiber, this is not true of the hardpercentage gives evidence that it is more resistant to the acid woods. hydrolysis than the pentosans and that alpha-cellulose does 4. Alph*cellulose percentages higher than 94 are obtained not necessarily signify high solution viscosity when it is peponly with a disproportionate sacrifice in yield. tized in cuprammonium reagent. Improved tear resistance 5. Solution viscosity of the refined pulps decreases as severity of treatment increases. and lower bursting strength on beating is consistent with the other changes that occur as the combined sulfur dioxide is Refinement of Wood Pulps with Cold Alkali. reduced. Bleachability is not adversely affected. From 5 to 18 per cent caustic soda solutions can be used effectively to remove hemicelluloseand pentosans from all types Hot Alkaline Digestion. Extraction of pentosans and of wood pulp. The concentrations of chemical needed make hemicellulose by means of hot dilute alkaline solutions has it impractical to utilize such a process without substantial been studied by many investigators. The process has been
that the hardwood pulps are normally high in pentosans, their removal becomes an especially important problem. As in previous comparisons, in the discussion that follows frequent reference is made to the better known softwood products. . Although there are many variations and combinations of treatments that can be applied to reduce pentosans and raise alpha-cellulose, the important methods of approach comprise:
2
1524
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 33, No. 12
INDUSTRIAL AND ENGINEERING CHEMISTRY
December, 1941
-
1525
TABLE XII. ELIMINATION OF PENTOSLVS BY HYDROLYSIS FOLLOWED BY ALKALINl DIGESTION Pulp Base Stage I
Softwood Unbleached SulfitNo 0.1% HC1, No treatlooo C.. treatment 6 hr. ment
r
Original pulp
Sta e I1
.. .. ..
880~
soln % T e m p e r a d , C. Time hours Yield' % =-celiuiose, Pentosans.
J
1 100
1 100 6 85.1 94.3 2.7
6
86.1 84.4 3.28
613 4.3
7.5 20 1 91 94.4 2.2
6% SOB
Original s o h 60' C . , pulp ii hr.
7.5 20 1 90 94.2 1.3
recovery of alkali. Cold alkaline refinement can be carried out with either sulfite or kraft pulps. It is practically indispensable in the manufacture of alpha fiber from alkaline cooked stock both because the hot dilute alkali process is here inoperative and because the papermaking strength that can be realized when kraft pulps are so treated is excellent. Furthermore, when kraft pulps are to be refined by cold alkali, white liquor containing both hydroxide and sulfide is used, and the recovered chemical is then employed without additional treatment in the cooking of new wood. With the sulfite pulps cold alkaline refining is especially advantageous when it is important to reach pentosan levels less than 1.5 per cent. I n such instances there is a sacrifice in papermaking strength, but in esterification processes this is not important. Both softwood and hardwood pulps respond to cold purification. Except where liquors stronger than 8 per cent sodium hydroxide are used at temperatures less than 10" C., for a given increase in alpha-cellulose the cold alkali process of purification almost invariably results in higher yields than are obtained with the hot dilute refinement. This advantage in
I
I
10
20
30
40
50
GO
70
80
1001
9896-
94 0
J 92-
?
$9088
-
86
-
8 41-
0
..
.. Sf:S 7.3
No
treatment
1
100 4 84.0 93.8 3.8
Hardwood Unbleached Sulfite 6% SO1 No Water 0.2% HpSOa soln., 100' C . . treatdigestion soln , looo C . 6 hr. ment 150° C. 3 dr. 2 hr.
1 100 4 81 93.7 1.9
18 20 2 86.2 96.3 2.2
18 20 2 85.0 96.1 1.6
18 20 2 82.0 96.6 0.60
yield may amount to as much as 2 to 6 per cent and reflects the more selective extraction that is possible with the cold liquors. On the other hand, for a given alpha-cellulose level the papermaking strength and tear resistance of sulfite products that have been refined with the stronger liquors are never so high as can be reached by the hot process. In general, with sodium hydroxide concentrations of more than 5 per cent and at temperature levels below 60" C., removal of pentosans and hemicellulose become more complete as the concentration of the alkali is raised and as the temperature of treatment is reduced. Thus a treatment with 5 per cent sodium hydroxide a t 10" C. is usually more effective than with 7 per cent alkali a t 30" C. I n some special cases a t temperatures approaching 0 " C., considerable purification of fiber can be obtained with solutions that contain as little as 3 per cent sodium hydroxide. The alpha-cellulose content of treated pulps appears to go through a maximum a t 15-20 per cent sodium hydroxide concentrations of treating liquor. Other work not reported here suggests that, when the temperature of treatment is raised above 30" C., this maximum relation no longer holds. However, it is probable that the history of the unrefined pulp will influence the concentration levels at which maximum percentages of alpha-cellulose are obtained. As in the hot alkaline purification, the yields with the hardwoods are somewhat lower when refined by the cold process, but i t is not difficult to refine the hardwood pulps to as high an alpha-cellulose and as low a pentosan content as that of the coniferous products; when this is done, the resulting fiber esterifies equally well. As shown in Table XI and Figure 2, combinations of 98 per cent alpha-cellulose and 1 per cent pentosans are possible, although papermaking strength is materially sacrificed in those cases where the alpha-cellulose exceeds 95 per cent. Brief mention is made of the fact that interesting combinations of low solution viscosity and high alpha-cellulose can be reached by the simultaneous application of cold alkali and an oxidant. This field of investigation is, however, not the subject of the present discussion. A few values are added to Table XI to show the behavior of other alkaline solutions than sodium hydroxide. The sulfide is less effective but can be used advantageously, particularly in connection with kraft pulp purification. Potassium hydroxide is much less potent than the sodium base; strong carbonate solution is practically useless for the purpose.
Prehydrolysis Followed by Alkaline Extraction. It has already been suggested that wood pentosans may be I
I
1
I
I
IO
20
30
I
I
I 60
40 SO TEMPERATURE OC.
I 70
I I 00
FIUURE2. EFFECTOF THIYPERATU~W AND CONCHINTRATION ON ALPH~-CELLULOSE (above) AND ON YIELD ( b h ) m P!HLI! STRONG ALKALITRBATMENT OF PULP
regarded as composed of alpha, beta, and gamma groups and that the more stable form resists the solvent action of caustic soda in the same manner as does alpha-cellulose. The pentosans can be degraded by hydrolysis and in some instances by oxidation, just as in the case of the more resistant cellulose components; the resulting hemipentosan may then be extracted more easily with alkalies. When pentosans are not sufficiently reduced by a simple alkaline treatment, i t is often
I N D U S T R I A L A N D E N-GI N E E R I N G C H E M I S T R Y
1526
Vol. 33, No. 12
that has been purified with alkali. Alpha-cellulose percentage is increased, and when the pulp is coniferous in origin, the stock acquires a material improvement in tear resistance when beaten and sheeted. It is obvious that this controlled hydrolysis can be followed by additional refinement with alkali although for many purposes this is not necessary. There seems t o be no difference in the manner in which the softwood and the hardwood pulps respond to this treatment, and it has been applied successfully to both the unbleached and bleached fiber. Several examples are given in Table XIII.
Selective Removal of Hemicellulose and Pentosans by Cuprammonium Solutions. By suitable ad-
CROSSSECTION OF WHITEBIRCH LOG
practical to insert a preliminary step in which further degradation of pentosan is carried out with as little injury as possible to the even more resistant alpha-cellulose component. Although hot acidic solutions constitute the most direct means for bringing about the chemical attack on the pentosans, it is of interest to note the dual role of hot chlorine which, under chosen conditions, delignifies the pulp and solubilizes pentosans simultaneously. Table XI1 suggests a method of approach which may sometime be commercialized although its application will probably prove more fruitful with kraft pulps containing higher percentages of total pentosans that are composed almost entirely of the more stable types.
TABLEXIII. Liquor o/ free S,Oz combined 502 Temperature, O C. Time, hours Yield, % a-Cellulose. Pentoaans, Lignin SO-min(. ?all-mill beating Bursting strength Tear resistance
d
2
justment in the composition of cuprammonium solution, one can selectively dissolve hemicellulose and pentosans from wood fiber. Solutions relatively dilute in both copper and ammonia are effective, and the selective action becomes even more marked in the presence of small percentages of sodium hydroxide. Larger percentages of the strong alkali interfere seriously with the solvent action of the cuprammonium reagent. The different wood pulps respond differently, and for eaFh there is an optimum temperature and composition for best results as measured by the greatest removal of pentosans and/or the best yield. Low temperatures result in lower yields, and there is always more difficulty in handling because of excessive swelling of fiber and sliminess of the stock mass if the temperature is below 20" C. Temperatures upwards of 40" C. favor ease of washing and elimination of copper residues. Yields improve sharply a t the higher temperatures of treatment, and pentosan removal is a t least as effective as a t lower temperatures. When the copper concentrations are reduced below 3 grams per liter, the effectiveness of pentosan removal becomes appreciably less even though the ammonia concentration is increased materially. Good results are possible a t 50' C. with a liquor that contains 5 grams of sodium hydroxide, 5 grams of copper, and 27 grams of ammonia per liter. For some unexplained reason, the increase in the alpha-cellulose that attends the extraction is more pronounced with the kraft-base fiber than with the sulfite pulps. Both kraft and sulfite types of pulp undergo substantial decrease in pentosan content and increase in alpha-cellulose when so processed. This holds with both softwood and hardwood fiber. The sulfite products are usually characterized by appreciable betterment in esterification properties while the kraft group takes on the high physical strength values that ueually occur with the other refining processes.
REFINEMENT OF
SULFITE PULP BY Unbleached Softwood Sulfite Pulp
Original Pulp
0.5
4.5 1.05
175 3 87.2 92.8 3.5 0.66
0.75 1.0 170 3 89.3 90.8 2.9 0.9
0.6 1.0 175 5 83.7 93.9 2.2 0.8
121 158
82 220
87 195
71 222
.. ..
si: 3
1.0
Reduction of Pentosans by Acid Salt Digestion. Hydrolysis of wood pulp pentosans can be so controlled by adjustment of temperature and composition of an acidic liquor that hydrolysis products may be made to proceed in large degree to water-soluble pentose without causing severe damage to the alpha-cellulose present. When this is properly done, the product takes on the characteristics of pulp
0.5 1.0 180 3 90.0 91.4 2.4
..
.. ..
ACID SALT DIGESTION Unbleached Hardwood Sulfite Pulp Original Pulp Sf11 7.3 1.6
0.5 1.0 180 3 88.0 89.1 5.1 1.1
0.7 1.0 180 3 89.0 89.9 3.7 0.9
0.7 2.0 180 3 88.0 90.2 2.1 0.8
95 90
80 85
75 88
71 84
....
Inasmuch as some of the pentosans of hardwood pulps can be easily removed by more ordinary procedures, it is generally best when very low pentosans are sought to practice a sequence by which the major reduction is so made and where the preliminary purification is followed by a cuprammonium treatment to attain the ultimate low levels desired. To my knowledge, the cuprammonium method of refinement has not
INDUSTRIAL A N D ENGINEERTHG CHEMISTRY
December, 1941
1527
yet been used commercially. Application as an integrated refining step in connection with ultimate conversion of fiber into cuprammonium solutions may some time prove practical, particularly if no better method is found to replace cotton fiber satisfactorily with wood cellulose for this purpose. Typical laboratory figures are given in Table XIV and plotted in Figure 3. a8
-
TABLE XIV.
86 0
SELECTIVE REMOVAL OF PENTOSANS AND HEMICUPRAMMONIUM REAGENT&"
CELLULOSE BY I
I
I
1.0
2.6
5.0
1
10.0
6RAMS N a OH PER LITER
.... . . . . . . .. .. .... . . . . .. ... .. .
i
\
90t
A . Treatments of Bleached Alkaline-Refined Softwood Pulp for 2 Hours -Grams per Liter-Temp., Yield, a-CelluPentoNaOH Copper NHs OC. % lose, % sa-, % Original pulp.. . , .94.2 2,9 0.0 3 17.4 40 96.8 1.70 1.0 3 17.4 40 96.0 1.58 2.5 3 17.4 40 96.0 1.36 5.0 3 17.4 40 94.7 9i:Z 1.35 10.0 3 17.4 40 97.0 1.50 0 5 28.9 40 94.7 1.39 1.0 5 28.9 40 94.7 1.24 2.5 5 28.9 40 93.8 1.08 5.0 5 28.9 40 91.4 .. 1.08 10.0 5 28.9 40 85.5 1.10 0 3 16.8 25 97.4 1.86 0 3 33.0 25 97.2 1.82 0 3 100.0 25 97.8 1.91 10 0 0 25 99.5 *. 2.8 10 5 27.5 20 80.2 1.08 10 5 27.5 30 83.5 0.98 10 5 27.5 40 87.4 0.96 27.5 10 5 50 90.0 0.94 10 5 27.5 60 93.3 1.04 10 5 27.5 20 83.0 * . 1.13 20 5 27.5 20 91.0 .. 1.53 30 5 27.5 20 97.3 1.82
2
2.0
.. .. 1.
.. .. I.
c
\\ I
2.5
1.0
90
I 50 GRAMS N a O H PER LITER
*. .... ..
I
.. .. ....
\ I\dl
..
10.0
..
B . Treatments of Bleached Hardwood Sulfite Pulp for 2 Hours
- 2.0
-
c
2
701
20
I
I
30
40
TEMPERATURE
II
I 50
6F
----Grams per LiterNaOH Copper NHa Original pulp.. 0 5 27.5 2.5 5 27.5 5.0 5 27.5 10.0 5 27.5 10.0 6 27.5 10.0 5 27.5 10.0 5 27.5 10.0 5 27.5 5.0 1 6.1 5.0 3 17.3 5.0 5 27.4
Temp., OC.
Yield,
40 40 40 20 40 50 60 40 40 40
92.4 91.9 80.1 75 80.1 91.3 93.3 97.2 94.6 92.0
%
a-Cellulose, % ..go. 1
.... . . . . . . . . .. .40. . . . . . . .92.5 . .... . . .
9616 90:s 91.0 9i:~
..
90.1 90.3 90.7
Pentosans, % 3.4 1.8 1.60 1.51 1.49 1.63 1.49 1.42 1.40 2.64 1.79 1.51
C. Treatments of Unbleached Kraft Softwood Pulps for 2 Hours at 30° C
OC.
~~
REMOVAL BY CTJPRAMMONIUM REAQENT F I G U R3.~ PENTOSAN (Abone) Extraction of softwood sulfite fiber. (Center) Extraction of hardwood sulfite fiber. (Below) Effect of temperature when processing.
-Grams per LitercopNaOH per NHI Original pulp.. 0 3 16 5 3 16 10 3 16 10 5 27
Yield,
%
a-Cellu- PentoBursting lose, % sans, % Strengthb 7.0 164 5.4 96.0 155 135 96.1 5:3 131 96.8 3.78 98
.......95.9 .....,...91.3 94.6
a
b
5
94.1 93.2 89.3
Tepr ReslsG anoe 260 279 313 314 326
stock used. beatings were continued 100 minutes.
HYDROLYSIS IN PRESENCE OF ALKALINE BUFFERS TABLE XV. HIGH-TEMPERATURE) None
Chemical
.. .. ..
8
based on soln. ime hours Tem 'erature, O C. Yie$ a-celluke, 88:2 pentosans 4.3 A. C. S. vi&&ity, poises 40.2
.;rO
.... ..
P
chemical ime hours Tem 'erature, C. Yied a-CehI%se, si:1 Pentosans , 7.3 A. C. 8.v d o o h y , poises 19.1
.;rO
Water
..3
175 84 75.0 2.1 1.0
..3
175 81 82 4.2 6.1
Water
NaI
NH;
Na acetate
NaiSOs
NatP01
CaCOt
CaCOa
BaCO:
0.5 3 200 80.1 96.1 2.1 8.2
0.6 3 175 93.3 89.0 2.8 16.0
0.6 3 200 84.5 94.4 1.7 4.0
0.5 3 200 84 94.1 1.8 2.1
.. .. .. ..
....
0.5 3 200 81.0 94.1 1.9 0.9
0.5 3 200 80.2 93.9 1.7 1.0
Unbleached Softwood Sulfite Pulp (5% Stock Suspension)
"3 200 79 68 1.9 0.8
1.0 3 200 87 78 1.2 0.4
0.5 3 81.5 94.5 1.7 3.0
1.0 3 200 86.6 94.0 2.1 6.0
0.5 3 200 83.4 94.6 1.67 7.0
Unbleached Hardwood Sulfite Pulp (5% Stock Suspension)
..
3 200 76 70.1 2.1 1.2
0.5 3 200 . 76 72 2.3 1.4
....
.. .. ** . .
..
0.5 3 200 81 93.8 2.0 2.0
0.5 3 200 79.2 94.4 1.8 1.1
.. ....
.. *. .. ....
INDUSTRIAL AND ENGINEERING CHEMISTRY
1528
High-Temperature Hydrolysis in Presence of Buffers. Wood cellulose is but slowly attacked by water at 100’ C. At higher temperatures hydrolysis becomes more marked, and at 160’ to 200’ C. there is appreciable elimination of pentosans, a definite sacrifice in a-cellulose, and a pronounced reduction in solution viscosity. Loss of a-cellulose can be avoided by adding small amounts of suitable buffer reagents that do not interfere with the convcrsion of the pentosan groups t o soluble sugars. The buffer materials serve to maintain fairly constant pH levels by progressive neutralization of some of the acidic by-products formed as hydrolysis proceeds. When such substances are present (Table XV), it is possible t o obtain products characterized by a combination of high alpha-cellulose, low pentosans, and low solution viscosity. Among the chemicals that operate satisfactorily are the borates, sulfites, acetates, aluminates, and alkaline earth carbonates, Temperatures of 180’ to 200” C. are necessary to obtain the desired effects in a few hours. Yields are somewhat less than are realized when the same alpha-cellulose levels are obtained by most other means except where low solution viscosity is produced by cold alkali treatments in the presence of substantial amounts of oxidant. The lower yields are ex-
Vol. 33, No. 12
plained by some unavoidable attack on the alpha-cellulose itself. The material of which the autoclave is constructed plays a n important role since it may serve as a secondary buffer for acids that are developed when the cellulose undergoes hydrolysis. The method of pulp purification can be used with hardwood as well as softwood pulps and is equally effective with unbleached, semibleached, and fully bleached stocks. With hardwoods the products can be brought t o suitably low viscosities to use directly as “nonaging” pulp in the manufacture of xanthates and in some instances to yield half-second nitrates when nitrated. Both the sulfite and the kraft types of wood pulps process satisfactorily, and temperatures and buffer chemicals can be chosen to obtain improved bleachability of resulting products. Table XV lists a number of data to show the extent to which the pulp properties can be altered by high-temperature buffer hydrolysis.
Literature Cited Richter, IND.EXQ.C H ~ M 23, . , 266 (1931). (2) Ibid., 33, 75 (1941). (3) Ibid., 33, 532 (1941).
(1)
THE SORCERER By Amedbe Forestier
H E R E we again have the alchemist depicted as a visionary, seeing a beautiful woman, as is the case in Nos. 79 and 99 in the Berolzheimer series of Alchemical and Historical Reproductions. This, No. 132 in the series, was painted in the early part of this century by Amedke Forestier, a Frenchman, born in 1854, but long a resident of London, where he died in 1930. Its present location is not known. Forestier was primarily an illustrator, although he executed many paintings. For many years he was one of the principal artists on the staff of the “Illustrated London News”. He also published several books. He was famous for his reconstruction drawings of‘ primitive man and other archeological subjects. He combined scientific accuracy with a vivid imagination. Forestier traveled all over the world to study the subjects he wished to illustrate or paint. In 1896 Queen Victoria sent him to Russia to paint commemorative pictures of the Coronation of the Tsar. D. D. BEROLZHEIMER
50 East 41st Street New York, N. Y.
The lists of reproductions and directions for obtaining copies appear as follows: 1 to 96, January, 1939, issue, page, 124; 97 to 120, January, 1941, page 114. An additional reproduotlon appears each month.
