Index cotton

Classification by usage or appHcation is the principal system adopted by the Colour Index (5). Because the most important textile fibers are cotton (qv) and polyester, the most important dye types are those used for dyeing these two fibers, including polyester—cotton blends (see Fibers, polyester). 

Bleached cotton stalk pulp is treated with different concentrations of ethylene diamine (50-100%) for 20 min. It is clear that the crystallinity index (CrI) of these treated pulps is decreased by increasing the concentration of ethylene diamine that is, the decrystallization increases. The degree of polymerization is nearly the same, but some increase is shown in the sample treated with 100% ethylene diamine. This indicates that 100% ethylene diamine may act as a dissolving agent for low degree of polymerization (DP) of cellulosic chains and hemicellulose. 

These are the only ranges of precursor products in the Colour Index that are still commercially significant. Azoic dyes have a close formal relationship to those monoazo pigments derived from BON acid or from acetoacetanilides (section 2.3.1) and some are chemically identical with them, although they are used in a totally different way. Azoic components are applied to produce insoluble azo dyes within the textile substrate, which is almost always cotton. Corresponding azoic components for the dyeing of cellulose acetate, triacetate and polyester fibres were once commercially important, but are now obsolete because of environmental hazards and the time-consuming application procedure. 

The UV and CD spectra of 117 and 121 (V) are shown in Figure 48. Considering 117, at —40°C a negative Cotton effect, coincident with the UV absorption, is evident, and at —5 °C a positive Cotton effect, coincident with the UV absorption (both of which are slightly red-shifted with respect to the —40°C profiles), is observed. It is thus apparent that 117 underwent a helix-helix transition at some temperature between —5 and —40°C. In contrast, the Cotton effects of 121(V) were positive at all temperatures, indicating that no helix-helix transition occurred. Similarly to 121, 88 did not undergo a helix-helix transition. These results are due to the different stiffness of the molecules, which is quantified by the viscosity index, a. 

Spanish Hemp Workers. Data collected on hemp workers have been offered in support of chronic respiratory effects associated with cotton dust exposure. Historically, hemp workers constituted the first group to call medical attention to their respiratory effects (27). More recent studies done on hemp workers, however, suggest similar limitations of methodology as mentioned above. The recruitment of subjects leaves much perplexity about the representative character of the group, when the source population is not accounted or even remotely described (28, 29, 30). The exposure length is not assessed (some of the workers have less than two years tenure) and/or the status of "retirement" is used uncritically as an index of exposure (29,... 

The naturally occurring dioxide exists in three crystal forms anatase, rutile and brookite. While rutile, the most common form, has an octahedral structure. Anatase and brookite have very distorted octahedra of oxygen atoms surrounding each titanium atom. In such distorted octahedral structures, two oxygen atoms are relatively closer to titanium than the other four oxygen atoms. Anatase is more stable than the rutile form by about 8 to 12 kJ/mol (Cotton, F.A., Wilkinson, G., Murillo, C.A and M Bochmann. 1999. Advanced Inorganic Chemistry, 6 ed, p. 697, New York John Wiley Sons) Other physical properties are density 4.23g/cm3 Mohs hardness 5.8 g/cm ( anatase and brookite) and 6.2 g/cm ( rutile) index of refraction 2.488 (anatase), 2.583 (brookite) and 2.609 (rutile) melts at 1,843°C insoluble in water and dilute acids soluble in concentrated acids. 

Circular dichroism arises from the same optically active transitions responsible for the Cotton effects observed in ORD curves, but unlike ORD it is an absorption, not a dispersion, phenomenon. Hence, the CD effect is restricted to the region of the transition and can be interpreted more straightforwardly. Both ORD and CD can best be understood if one imagines the incident plane-polarized beam resolved into two in-phase circularly polarized beams whose vectors rotate in opposite directions. A difference in index of refraction between the left and right circularly polarized beams results in rotation of the transmitted plane polarized beam while differential absorption of the two circularly polarized beams results in depolarization of the transmitted beam, so that an incident plane-polarized beam whose frequency is within that of an optically active absorption band becomes both rotated and elliptically polarized upon passage through the sample. This depolarization effect is CD, and the measured parameter is (et — er), the difference in extinction coefficient between the left and right circularly polarized beams. The data is usually recorded as the specific ellipticity, defined as ... 

Fig. 12.25 The Cotton effect (a) positive Cotton effect (b) negative Cotton effect. The absorption band is not shown it would be a positive Gaussian curve centered on Am, but o scale. The dashed line represents the ORD curve (and relates to the refractive index scale on left. The solid line represents the CD curve ( ( — scale on right). The maximum absorption, zero values of DRD. and maxima and minima of CD values occur at The...

Copper Value (Copper Index or Copper Number) of Cellulose It represents the amt of Cu reduced from the cupric to cuprous state in alkaline sola by lOOg of cellulose (such as cotton). In case of cotton, it gives an indication as to whether any appreciable changes have taken place during purification proceduresjin case of woodpulp, it indicates the degree of purity. Accdg to Doree (Ref 4 pp 26 32-3)>normal cotton cellulose has copper values below 0.2 while sulfite pulp has value>2. The alpha-cellulose obtd from sulfite pulp had a value of 0,8... 

S S CONTENTS Preface, C. Allen Bush. Methods in Macromo-lecular Crystallography, Andrew J. Howard and Thomas L. Poulos. Circular Dichroism and Conformation of Unordered Polypeptides, Robert W. Woody. Luminescence Studies with Horse Liver Dehydrogenase Information on the Structure, Dynamics, Transitions and Interactions of this Enzyme, Maurice R. Eftink. Surface-Enhanced Resonance Raman Scattering (SERRS) Spectroscopy A Probe of Biomolecular Structure and Bonding at Surfaces, Therese M. Cotton, Jae-Ho Kim and Randall E. Holt. Three-Dimensional Conformations of Complex Carbohydrates, C. Allen Bush and Perse-veranda Cagas. Index. 

From the commercial point of view, only the 2,5-diarylamino-l,4-benzoquinones have been of any significance. They were used as vat dyes for wool and cotton, but are no longer in commercial production. Other examples of early dyes of this type are listed in the Colour Index under numbers 56000-56050. The inadequate color properties of the amino-substituted benzoquinone chromogen are exemplified by 2,5-bis(dimethylamino)-l,4-benzoquinone [1521-02-4], which absorbs at 530 nm in ethanol with an absorption coefficient of only ca. 500 Lmol em1. This low intensity is characteristic of the 2,5-disubstitution pattern. Although other substitution patterns have higher intensities (e g., the 2-amino derivatives have an of ca. 5000 L mol-1 cm ), dyes based on these have not been... 

One method of classifying acid dyes is to divide them into groups according to their application behavior. The traditional wool/nylon/cotton classification is customarily employed by the Colour Index and is therefore used here, too. 

This approach is based on the introduction of molecular effective polarizabilities, i.e. molecular properties which have been modified by the combination of the two different environment effects represented in terms of cavity and reaction fields. In terms of these properties the outcome of quantum mechanical calculations can be directly compared with the outcome of the experimental measurements of the various NLO processes. The explicit expressions reported here refer to the first-order refractometric measurements and to the third-order EFISH processes, but the PCM methodology maps all the other NLO processes such as the electro-optical Kerr effect (OKE), intensity-dependent refractive index (IDRI), and others. More recently, the approach has been extended to the case of linear birefringences such as the Cotton-Mouton [21] and the Kerr effects [22] (see also the contribution to this book specifically devoted to birefringences). 

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