The fact that the unbleached sulfite pulp gives a red color was recognized about thirty years ago.This phenomenon has been studied by several investigators on the softwood pulps, but not on the hardwood pulp.Though the unbleached sulfite pulp prepared from hardwood gives also a more or less distinct red color, the reddening of hardwood pulp some what differs from the reddening of softwood pulp.The reddening of softwood pulp appears in a course of storage, while the reddening of hardwood pulp appears immediately in a course of washing of pulp discharged from a digester.In this paper some studies are given on the reddening of hardwood sulfite pulp.
Sulfite pulps were prepared from seven kinds of hardwood (poplar, alder, birch, beech, oak, maple and lime), left for seventy hours to stabilize the red color appearing on the pulps and then the degree of reddening of pulp was determined by the EPIC spectrophotometer against a_magnesium oxide plate.
The red color of pulp was the most pronounced in cases of birch, maple, lime and alder. The red color gives a reflection minimum at ca. 500mp (Fig.1), though the red color of softwood pulp gives a reflection minimum at 510-520mp.It seems that this coloring matter is already produced on a half way of cooking period, and thereafter the two reactions, the production and the decomposition of the coloring matter take place simultaneously (Table 2).The deepness of red color is not always proportional to the lignin content of pulp.
The reddening of softwood pulp is considered to be caused by the lignosulfonic acid (or the product derived from it) in pulp.The same conclusion may be drawn from the following facts in case of hardwoodpulp. (1) The red color can be also observed on the pulp prepared from birch wood free from extractives (Fig.2). (2) The red color can not be observed on the pulp prepared from spruce wood (the spruce sulfite pulp gives not red color in the authors' experiment) impregnated with the extractives of birch wood. (3) The pulp prepared from spruce wood impregnated with the solid lignosulfonic acid obtained from birch wood, gives a pink color.The presence of heavy metal ion promotes the reddening of pulp (Fig.3).Bleaching powder and sodium chlorite are effective to remove the red color appearing on pulp (Fig. 6).The color can be also removed by treatment of hot water or aqueous solution of sodium hydroxide whose concentration is more than 5 milli molg.

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Alkaline degradation of protolignin using aqueous sodium hydroxide were studied in an attempt to obtain some clearance on lignin chemical structure.Of these degradation products four phenolic compounds were isolated and identified through tedious procedures vanillin, vanillic acid, acetovanillone, guaiacol and 3, 3'-dimethoxy-4, 4'-dioxy-stilbene.
Identification of the fourth compound led us to reconfirm I.A.Pearl's suggestion that a linkage exist between the a-carbon atoms of two phenylpropane units in at least a part of the protolignin structure.

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In Ca-base sulphite cooking of larch (Larix leptolepsis Murray) heart wood chip, it has been investigated how various techniques promoting penetration of cooking liquor improve the cooking results.The results obtained are as follows.
1.Effect of high concentration cooking liquors.Relating to the concentration of combined acid, its effect was investigated within the range from 1.0 to 1.7% at the same concentration of free acid (7%) and liquor to wood ratio of 6.Comparatively great improvement was found by increase of the acid from 1.0 to 1.2%, but increase over 1.2 % had not any improvement in the results.Increase of free acid brouht noticeable improvement.Under the concentration used in this study, the best pulping results was obtained with the liquor of 6.5 ro free acid and 1.5 ro bombined acid (Screenins/pulp : 20.1%, Cl₂ consumption : 7.7%, see Table I)
2.Effects of steeping chips in water, presteaming or Va-purge pretreatment.These pretreatments showed substantial improvement.Presteaming (for 4 mins.by 2.5 kg/cm2 steam) and Va-purge pretreatment (3 times for 1.5 mins.by 2.5 kg/cm2 steam) showed identical results that screensngs/pulp was ca.10% and Cl₂ consump.7.5%.Under the conditions used, the better next to the above pretreatments was steeping chips in water under reduced pressure (screenings/pulp : 12.1%, Cl2 consump. : 8.74%) followed by vacumimpregnation of cooking liquor (screenings/ pulp : 16.4% Cl₂ consump.7.25%).Steeping chips in water without evacuation showed little improvement compared with regular pulping. (see Table I andIII)
3.Although the above techniques brought considerable improvement in the pulping results, they were much inferior to the use of soluble bases such as Na and NH3 by which sceernings was only about 2 % of screened pulp and Cl2 consumption of the pulp ca.4%.
4, From curves of delignification and thiosulfate and sulfate formation during cooking, it has been deduced that, besides the decomposition of cooking liquor by taxifolin, slowness of delignification in sulphite cooking of larch heart wood is another substantial cause of difficult pulping of the wood.The slower delignification may be caused by difficult penetration of the wood.

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A sample of half-bleached sulfate pulp (sample A) is bleached by means of chlorite (sample 13) and hypochlorite (sample C) respectively.D.P.distribution of these three samples is determined by the summative fractionation method, using cupri-ethylenediamine as solvent.The results obtained show that thoug the chlorite bleaching also shortens somewhat the chain lengths of cellulose the shape of distribution curv of (B) resembles to that of the original pulp (A), while the hypochlorite bleaching degradates the highe D.P.portion remarkably.
The summative fractionation method is approved as more convenient for the approximate estimation samples of alike species.

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1.

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アルカリ溶解度 前回報告したとおり, 本委員会においてはCCA: 53法およびMerkblatt IV/29法について詳細な研究を行ったが, 現在の所ではわが国の業界はこれらの方, あるいはこれと類似する方法を採用しようとする極積的な意図はもっていない。しかし本委員会はこれらの方法に全く無関心なわけでなく, 諸所の研究所においてアルカリ溶解度試験法について引続き検討を行っている。
CDEかCAMか 2種の溶剤の溶解能およびこれらの溶液中における繊維素の崩壊に対する安定度を測定した。2段溶解法を使用する場合, 中位の重合度を持つ繊維素試料に対しては, CAMよりCEDの方が大きい溶解力を持つ。また繊維素はCAMよりCEDの中における方が安定である。これらの試験は極限粘度との積が3になるような繊維素濃度において行われた。
繊維素溶液の流動性 粘度測定法の確立ないし改訂に対する学術的根拠を与えるため, 重合度を異にする繊維素のCEDおよびCAM溶液の流動特性を研究した。使用した粘度計はMaron-Krieger-Siskoの粘度計で, 水素気流中で測定を行えるように改良した。非ニュートン液体の粘度は流動曲線上の任意の点における剪断力と剪断速度との比として求めた。
CEDおよびCAMの溶液自身は事実上ニュートン液体であるが, 繊維素溶液は濃度がある限界をこえると非ニュートン的になる。この限界濃度は重合度が高いほど低い。log(η_SP/C)-C図を外挿して極限粘度を決定しようとすれば, 剪断速度の影響を考慮しなければならない。
一点法 或る一つの条件のもとで測定された相対粘度から極限粘度を算定する所謂一点法(onepoint method)はWetzel, ElliotおよびMaftinによって提案され, 最近Wilsonによってその実用化が図られた。この方法で得られる極限粘度の値は, 試料の重合度が余り高くない限り, 外挿法で求められた値とよく一致する。また従来のStaudinger法による値とも地較したが,差異はあまり大きくなかった。
一方CAMを使用して一点法を検討した。各国の標準法はそれぞれ組成の著しく異なるCAMを採用しているが,Martinの定数k'はCAMの銅濃度に対して鋭敏である。もしk'に適当な値を使用すれば, 一点法はCAM溶液に対しても非常によく一致した極限粘度を与える。この場合使用すべき定数k'の値は, ACS法には0.30, TAPPI法には0.31～0.32, JIS法には0.35である。

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