Forming section, paper production

For production of woodfree uncoated and coated fine papers up to 40 kg starch per ton of paper are applied. 3 to 10 kg starch is added at the wet end, with the aim of internal strength improvement and retention increase. The major share of the starch is added to the sheet in surface treatment. A mass balance on a typical fine paper machine has shown, that more than 90% of the added starch is retained in the final paper product. Losses occur mainly during the sheet forming process in the wire section due to insufficient retention. Starch which is not held back in the paper is discharged with the process effluents to the waste water treatment plant, where a complete biodegradation process follows. 

Our previous treatment (76AHCS1, p. 12) contained a section called Chemical Methods to Study Tautomerism where the relationship between tautomerism and reactivity was discussed. Today, nobody uses chemical methods to study tautomerism. However, a great many reactions are carried out on tautomeric heterocycles, although few papers contain new insights on that topic. Authors desiring to explain reactivity results based on tautomerism must take great care to verify that the substrate is in the neutral form AH and not as a conjugated anion A or cation HAH, which are usually devoid of tautomerism. They must also realize that most frequently the reaction path from tautomers to products in-... 

The formation of relatively stable fluorescent products by the reaction of adrenaline with ethylenediamine (and certain other primary amines) in air, first reported in 1948 by Natelson et was adapted by Weil-Malherbe and Bone in 1952 for the assay of catecholamines.197 198 Since 1952 much work, largely of an empirical nature, has been carried out to improve the analytical procedure since often apparently minor variations of the reaction conditions have a significant effect on the fluorescence observed (see Section V, E, 4). Paper chromatographic examination of the reaction mixtures obtained from adrenaline and noradrenaline suggested that more than one product could be formed in each case.199-205 The main fluorescent product of the interaction of adrenochrome (1) (obtained by oxidation of adrenaline) and ethylenediamine in air has been obtained as a crystalline solid by Harley-Mason and Laird and shown to be 2,3-dihydro-3-hydroxy-l-methylpyrrolo[4,5-g]quinoxaline (94) (7% yield).206,207 This compound has two hydrogen atoms less than... 

The photochemical processes of triatomic molecules have been extensively studied in recent years, particularly those of water, carbon dioxide, nitrous oxide, nitrogen dioxide, ozone, and sulfur dioxide, as they are important minor constituents of the earth s atmosphere. (Probably more than 200 papers on ozone photolysis alone have been published in the last decade.) Carbon dioxide is the major component of the Mars and Venus atmospheres. The primary photofragments produced and their subsequent reactions are well understood for the above-mentioned six triatomic molecules as the photodissociation involves only two bonds to be ruptured and two fragments formed in various electronic states. The photochemical processes of these six molecules are discussed in detail in the following sections. They illustrate how the knowledge of primary products and their subsequent reactions have aided in interpreting the results obtained by the traditional end product analysis and quantum yield measurements. 

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