On the view point of the submicroscopic cellulose structure, the mechanism of the cellulose reaction has been mainly investigated by means of the x-ray diffraction method. This method is not adequate to detect the accessible property of cellulose during the reaction, but can detect the thoroughly constructed crystalline structure. Such an accessible property is related with the area of the crystalline surface, the fine crystallite, the fringe of micell, the type of hydrogen bond, and the quantity or property of the substituents. And yet, the reactivity of cellulose is rather close to the accessible property than the crystalline structure of cellulose, and also, the difficulty of separating x-ray interferences which are originated from the unreacted and reacted crystallite is frequently encounted. Therefore, the satisfactory interpretation on the mechanism of the cellulose reaction cannot be built up by the only x-ray diffraction method.
On this report, the new method which involves the infrared spectrum examination accompanied by the deutration of the partially reacted cellulose is devised, and the mechanism of the nitration is investigated by this method (infrared method) along with the x-ray diffraction method. The results are shown as follows:
As the nitration by the HNO₃-H₃PO₄ mixture, proceeds, -
1) accessibility of the hydroxyl group increases.
2) the spectrum figure of the stretching mode of the unaccessible hydroxyl group differs from the unreacted cellulose, and becomes broad,
3) the spectrum of OD stretching mode which results from deutration of the accessible hydroxyl group has two peaks.
From these phenomena, it becomes clear that a large quantity of the unaccessible hydroxyl group convertes into accessible, and also, the type of hydrogen bond of the unaccessible hydroxyl group changes as the nitration proceeds. Therefore, the mechanism of nitration by the HNO₃-H₃PO₄ mixture may be considered as follows; that the reaction-reagent penetrates into the crystallite, and most of hydroxyl groups on the cellulose chains are uniformly nitrated.
On the case of the nitration by the HNO₃-H₂SO₄ mixture,
1) at the initial period, the increase of the accessibility of the hydroxyl group is not greater than the case of the HNO₃-H₃PO₄ mixture, the spectrum figure of the unaccessible hydroxyl group is similar to the unreacted cellulose, From these findings the existence of region which is not concerned in the reaction is suggested.
2) at the later stage of nitration, the spectrum becomes similar to that of the HNO₃-H₃PO₄ mixture. From these results it is considered that at the initial period of the nitration on the HNO₃-H₂SO₄ mixture the reaction has a considerable non-uniformity, but convertes into uniformity with the proceeding of the nitration.
The results obtained by infrared method have good correlativity with the results of the x-ray method.

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In general adsorbed amount of acid dye on nylon 6 fibre is often independent of content of amino end-groups as available sites for the dye. Dyeing mechanism was investigated in order to explain the cause of unequivalency between adsorbed amount of acid dye and content of amino end-groups in the fibre. Nylon 6 fibres for test were pre-set in saturated steam and then acetylated with acetic anhydride under different conditions. Thus prepared sample A contained 6.49×10^-2m mol of amino end-groups per 1g fibre, the sample B 3.63×10^-2m mol, the sample C 1.61×10^-2m mol, and the sample D 0.567×10^-2m mol. An acid dye Orange II and a disperse dye Solvent Yellow 14 were purified before determined. Dyeing was carried out at 95°C and pH 3.
Isotherms were determined for Orange II and Solvent Yellow 14 on the samples and the following results were obtained. Isotherm for Orange II on the sample D containing the least amino end-groups shows similar to that for Solvent Yellow 14, suggesting same dyeing mechanism as that of nylon with disperse dye i.e. solution mechanism. However, from isotherm for Orange II on the sample A or B containing the more amino end-groups, dyeing may be explained by means of the solution mechanism described above. Langmiur's adsorption which is usually considered to take place on amino end-groups in nylon is also considered.

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Crystallinity of polypropylene fibers subjected to wet-heat-treatment under tensionless and stretched states, was examined by large- and small-angle X-ray diffractions.
First, the effects of crystallite size and crystal distortion in the broadening of the X-ray diffraction line were studied by applying the Warren's analysis for polypropylene fibers. The X-ray diffraction intensity curves of the (110) and (220) reflections as a set of lattice planes were measured and corrected with the method of Stokes by using Pb (NO₃)₂ powder as a standard. Applying the Warren's Fourier analysis to the true line profiles thus obtained, the average crystallite size and internal strain along the direction perpendicular to the above reflections were calculated separately.
The meridian small-angle scattering intensity curve was also measured.
The results are as follows:
(1) The degree of crystallinity and the crystallite size increase by heat-treatment, more conspicuous under stretched state.
(2) The meridian small-angle scattering intensity and the long spacing increase by heat-treatment, more conspicuous under tensionless state. The sharpness of the scattering peak, however, is more remarkable in the stretched-heat-treatment.
(3) These changes in crystallinity become more distinguished in the heat-treatment above 120°C.
(4) The distortion in the crystallite decreases by heat-treatment and is the minimum in the heat-treatment at 120°C.
From an observation of the relations between the degree of crystallinity and the crystallite size or long spacing, the crystallization in heat-treatment is discussed, as in the previous study.

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