Microtome preparats of wood section (thickness 20μ) obtained from the sap wood of red pine (Pinus densiflora), heart wood of larch (Larix leptolepis Murray) and beech wood (Fagus japonica Maxim) digested by 50% sodium chlorite solution and investigated under microscope. Photographs are showed on the Japanese language report in this paper.
Sodium chlorite reaction conditions are as follows : NaClO₂ 5%, PH value 5 by acetic acid medium, temperature 80°C, and after digestion wash with water, then dyed with malachite green. Compared each samples of changed time of digestions. Thus sodium chlorite treated samples were dissolved in 72% sulphuric acid and cuprammonium solution respectively.
All of the sap wood of red pine, the heart wood of larch and the beech wood almost same results are obtained by sodium chlorite digestion. Lignin almost dissolved in 30 minutes, and medullary ray content entirely dissolved in 20 minutes.Lignin dissolved easily and damage of cellulosic fibrils are not seen. Then, pulps obtained by sodium chlorite digestion are treated with cuprammonium solution and observed with microscope. Swollen fibers by cuprammonium solution showed in Fig. 22, 23 and 24.
In short time digestion are visible spherical shape of swollen parts. These phenomena indicate that the cuticle partly remained as original state by long time digestion these spherical shape of swollen parts are not seen.

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The color of pulp is important as a criterion of its quality. Usually in factories, the color of a pulp has been determined by visually comparing the sample with the “Standard white”(MgO Plate) or by measuring the reflectance at one wave length with Pulfrich Photometer.
But the former method cannot represent quantitatively the color difference of a pulp to another, and the latter cannot distinguish bright reddish pulp from dark grey one.
Generally the color of a matter can be completely represented by three quantities, in I.C.I. system, that is Luminosity, Purity and Dominant wave length.
But in calculating these quantities the spectral reflectance of a matter is necessary, which is obtained by a spectrophotometer, such as G.E. Recording Spectrophotometer.
This measurement is too troublesome to do in a factory.
§ The result obtained by G.E. Photometer shows that ordinary Rayon Pulps have nearly flat spectral reflectance curve with slight low reflectance at the short wave length region and that the color difference lies chiefly in “Luminosity” and “Dominant wave length”. Purity has almost same value throughout the range.
Therefore the reflectance at a definite wave length-such as 55omμ (R_G) and the ratio of reflectances for blue and red lights (r=R_B/R_R ) are sufficient to represent the color characteristics of a Rayon Pulp, where R_B and R_R are respectively spectral reflectance at 450mμ and 630μ.
The large value of R_G means that the pulp is bright and the small value of r means that the pulp is reddish.
§ To obtain R_G and r, each of three monochromatized lights from 200W tungsten lamp with monochromatic filters is projected alternatively on the sample and on the “Standard white plate” and the reflected light being receieved by Sb-Cs photoelectric cells, the ratio of the amplified output currents is measured.
The results of experiments are shown in Tab. 1.

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We made a semi commercial grinding test of some soft woods grown in the Shizuoka district. The woods used are as follows :
Pines (Akamatsu & Himekomatsu), Firs (Sirabe & Momi), Spruce (Tohi), Hemlock (Kometsuga), Larch (Karamatsu) and Chamaecyparis (Hinoki).
The grinding conditions : 400 Hp 3 pocket grinder, natural sandstone, 250r.p.m.press 301bs, pit temp., 70°C, Burr ; spiral 8 cut I 1/2 in. lead.
The characteristics of pulping these woods are as follows :
Akamatsu ; Refined pulp yield is high. Energy consumption is comparatively low.The pulp is short fibred, bursting ratio 0.9, whiteness 66, grayish.
Himekomatsu ; A.P.M.W. screen waste and white water loss are much, so the refined pulp yield is very low. The pulp is long fibred, bursting ratio 0.9 whiteness 70, but very yellowish. The fatal defect Is high pitch content (about 30%).
Momi ; Refined pulp yield is a little lower. The pulp is short fibred, bursting ratio 1.0, whiteness 64, a little reddish.
Shirabe ; A.P.M.W. screen waste is much. Refined pulp yield is low. Energy consumption is low. The pulp is long fibred, bursting ratio 1.1, whiteness 70.5.
Tohi ; A.P.M.W. screen waste is much. Refined pulp yield is low. The pulp is long and soft fibred, bursting ratio 1.4, whiteness 68, a little reddish.
Kometsuga ; White water loss great. Refined pulp yield is low. The pulp is a little short fibred, bursting ratio 0.6, whiteness 60, very reddish.
Karamatsu ; Refined pulp yield is low. Energy consumption is high. The pulp is short fibred, low freened, bursting ratio 0.8, whiteness 48, dirty.
Hinoki ; Refined pulp yield is a little lower. Energy consumption is high. The pulp is short and fine fibred, pulp sheet is dense, bursting ratio 1.1, whiteness 62.5, reddish.

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