Cellulose determinations

The angle of the fibrils and the content of cellulose determine the properties of the plant fibers. The Hearle et al. s model [19] considers only these two structure parameters. For the description of stiffness, solely, the St layers were considered because the properties of these fibers were decisively dominated by the amount of these layers. 

The constitutional formula and molecular weight of cellulose determined on the basis of chemical and physico-chemical experiments has been confirmed by X-ray analysis, which has also led to the discovery of the microcrystalline structure of cellulose. Today the structural model proposed by Meyer and Mark [21] and Mark and Misch [22] based on the X-ray measurements of Polanyi [23] and Sponsler and Dore [24] and taking into consideration Haworth s conclusions about the existence... 

Polymerization degree of cellulose (determined by measuring the viscosity of cuprammonium solution) 76 186 254 450 720 1540 2550... 

Figure 6. The n-h map for cellulose, determined by hard-sphere criteria (see text and Table I). Note the zones of helices of small h and large n as well as the more usual conformations with small n and large h. The short contacts found in models for intermediates between the allowed zones would not be so severe as to prevent interconversion of the two types. Increments for n and h were 1 and 0.2 A,...

Fig. 2. Reducing groups per amount of cellulose determined by BCA assay for MCC ( ), AMCC ( ), PSC (A), BMCC, (x), and A BMCC, ( ). Values represent the mean of triplicate determinations error bars represent the SE. When not shown, the error bars fall within the symbols.

KCrschner Cellulose. Kiirschner cellulose is obtained by refluxing the wood sample three times for 1 h with a 1 4 volume mixture of concentrated nitric acid and ethyl alcohol (37). The washed and dried residue is weighed as Kiirschner cellulose. The product contains a small amount of hemicelluloses. [The cellulose determined for the Ghanan and Russian woods see in Tables VI and XI) is Kiirsch-ner cellulose]. The method is not widely used because it destroys some of the cellulose and the nitric acid/alcohol mixture is potentially explosive. 

Cellulose determined using alcoholic nitric acid (Kiirschner cellulose) for Ghanan woods. A mixture of concentrated nitric acid and glacial acetic acid was used to determine cellulose in Mozambique woods. See Refs. 64 and 65 for details. 

Table I. Average Ordered Fraction Present in Celluloses Determined by Various Techniques ...

One indication that the formation of the trinitrate derivative of cellulose causes depolymerization and the formation of the tricarbanilate does not is that the DPs of cellulose determined as the tricarbanilate are considerably greater than those obtained as the trinitrate (22). Although a plausible explanation for this difference is the depolymerization of cellulose curing formation of the trinitrate derivative, comparison of DP derived from the trinitrate and the tricarbanilate using the same sources of cellulose indicates that this difference may simply be a result of errors in the Mark-Houwink coefficients for cellulose trinitrate in acetone solution (22). 

Whereas conventional gravimetric cellulose determination is complicated and time-consuming, cellulose concentrations can be determined rapidly in ammoniacal copper solution by measuring the optical rotation of the levorotatory solution. However, the solutions must be completely free of turbidity [138]. 

D. Wetzel, H. Mark. Spectroscopic cellulose determination as a criterion of flour purity with respect to bran. Cereal Foods World 22 481, 1977. 

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