Stirred fundamental aspect

Unvulcanized Latex and Latex Compounds. A prime consideration has to be the fluid-state stabihty of the raw latex concentrate and hquid compound made from it. For many years, the mechanical stabihty of latex has been the fundamental test of this aspect. In testing, the raw latex mbber content is adjusted to 55% and an 80 g sample placed in the test vessel. The sample is then mechanically stirred at ultrahigh speed (ca 14,000 rpm) by a rotating disk, causing shear and particle cohision. The time taken to cause creation of mbber particle agglomerates is measured, and expressed as the mechanical stabihty time (MST). 

In addition to the above investigations, free-radical high-pressure polymerizations should also be studied in continuously operated devices for three reasons. (1) Because of the wealth of kinetic information contained in the polymer properties, product characterization is mandatory. Sufficient quantities of polymer, produced under well defined conditions of temperature, pressure, and monomer conversion, are best provided by continuous polymerization, preferably in a continuously stirred tank reactor (CSTR). (2) Copolymerization of monomers that have rather dissimilar reactivity ratios, such as in ethene-acry-late systems, will yield chemically inhomogeneous material if the reaction is carried out in a batch-type reactor up to moderate conversion. To obtain larger quantities of copolymer of analytical value, the copolymerization has to be performed in a CSTR. (3) Technical polymerizations are exclusively run as continuous processes. Thus, in order to stay sufficiently close to the application and to investigate aspects of technical polymerizations, such as testing initiators and initiation strategies, fundamental research into these processes should, at least in part, be carried out in continuously operated devices. 

While the amusing aspect of this book is its use of allegory, the most fascinating aspect is the manner in which solid scientific reasoning, based upon experimentation, is employed to discredit some fundamental tenets of alchemical lore. While the magistery of alchemy wins the day ( The Hermetical Triumph ), early stirrings of the Scientific Revolution are quite audible. 

Nowadays, fundamental work on determination of characteristics of metal extraction processes is conducted almost exclusively in stirred cells, already referred to in the contribution on Physical Aspects of Solvent Extraction. In such cells the two phases can be stirred independently but at a rate which produces a practically uniform concentration in the bulk of each phase while the interface remains constant and quiescent. 

The basic aspects of a control system are the same, independent of the size of the automated system or of the type of the controlled process. The fundamental automation tasks, which are independent of the control system used, have to be described and implemented. An example of such a control task is closed-loop control. The system tries to move a measured process variable (e.g. temperature) towards a desired, typically analogue, value (set point) and keep it there by manipulating an output variable by controlling the current flowing through a heating jacket in a stirred vessel. 

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