Molecular Weights in Solution

Equation (8) was found to give results in good agreement with experiment by vaiTt Hoff (1885), van Deventer and van der Stadt (1892), and Noyes and Sammet (1903). An agreement between the observed and calculated values of A implies that the solute has a normal molecular weight in solution. 

Homoleptic silver(I) thiolates AgSR have been known and used for a long time,957,958 but until recently with little definitive information about their structures. They are insoluble or slightly soluble, yielding unreliable high molecular weights in solution, indicative of nonmolecular crystal structures. These compounds dissolve due to the presence of thiolate ions. 

Figure 8 Difference in the size of a branched polymer molecule (b) compared to its linear analogue (a) of the same molecular weight in solution. 

BECKMANN, ERNST (1853-1923). Beckmann was a German chemist who discovered in 1886 the arrangement of oximes of ketones into acid amides or anilides, named the Beckmann molecular transformation. He was the inventor of two pieces of apparatus used in determining freezing and boiling points of solutions. The Beckmann thermometer is used for determining molecular weights in solutions. 

The partial esters of phosphoric acid show strong intermolecular hydrogen bonding in the solid, liquid and solution states. This is indicated by the resnlts of crystal structure determination, the characteristic frequency shifts of infrared absorption spectra and the increased molecular weights in solution as revealed by freezing point depression. 

M. P. Vega, E. L. Lima, J. C. Pinto, In-line monitoring of weight average molecular weight in solution polymerization using intrinsic viscosity measurements , Polymer, 2001, 42, 3909. 

An evaluation of ether solvents as the polymerization media was undertaken for preparing polyamic acids to be used as adhesives. The systems that exhibited the best adhesive properties were those that seemed to build to high molecular weight in solution before precipitation occurred. In contrast to the systems where the polyamic acids precipitated from ether solvents as powders, the BTDA-diamino-benzophenone (DABP) amic acids tended to precipitate as gummy amorphous materials. For this and other cases where clouding or precipitation occurred, conditions could be reversed and clear solutions obtained by the addition of a small amount of a low molecular weight alcohol (usually ethanol). These solutions were used directly in the bonding process. 

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