Semi-mercerization

Cotton can be causticized or half-mercerized to increase the dye uptake and economics up to 25% may be realised. Semi-mercerization or causticization is carried out in caustic soda solution between 25 and 30 Tw at a temperature of 20-25 C, sometimes without stretching the cloth to restore original dimensions. Sodium hydroxide solution above 30 Tw the rate of colour absorption decreases. Semi-mercerization is also an important step where heavy shades are required with the expensive vat colours. Better results are also observed with aniline black on goods which have received a semi-mercerization treatment. 

In this method the undyed fabric is spotted with 30% solution of caustic soda and then both mercerized and undyed spotted fabric samples are dyed by using Benzopurpurine. If the fabric is fully mercerized, the spots will not be evident after dyeing. On the other hand, if the fabric is not mercerized or semi-mercerized, dark spots will be evident and the degree of mercerization can be evaluated on comparing the spots. 

For exact estimation, correction should be made for the moisture regain of the sample. Barium activity number of unmercerized cotton is considered as 100 and semi-mercerized cotton ranges between 115 to 130 and that for completely mercerized cotton is about 155. 

Acetylation rates have also been studied by Centola37 who treated natural and mercerized ramie fibers for varying times with acetic anhydride and sodium acetate and examined the reaction products chemically and by X-ray diffraction. The reagent was considered to penetrate into the interior of fibers. A heterogeneous micellar reaction was believed to occur that converted a semi-permeable elastic membrane around the micelles into the triacetate. The rate of acetylation of mercerized ramie was observed to be faster than that of unmercerized fiber. Centola concluded that about 40 % of the cellulose in native ramie is amorphous and acetylates rapidly. 

In both the dual solution and decision function, only the inner product in the attribute space and the kernel function based on attributes appear, but not the elements of the very high dimensional feature space. The constraints in the dual solution imply that only the attributes closest to the hyperplane, the so-called SVs, are involved in the expressions for weights w. Data points that are not SVs have no influence and slight variations in them (for example caused by noise) will not affect the solution, provides a more quantitative leverage against noise in data that may prevent linear separation in feature space [42]. Imposing the requirement that the kernel satisfies Mercer s conditions (K(xj, must be positive semi-definite)... 

Let us observe this theorem, the positivity condition I K(x,z)/(x)/(z)dxdz > 0, V/ 6 Z2 (X), corresponds to the positive semi-definite condition in the finite case, this gives the second characterization of a kernel function that is proved to be most useful when we come to constructing kernels. We use the term kernel to refer to function satisfying this property, but in the literature these are often called Mercer kernel. 

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