The Effect of ω-Substituted Acceptors in 4-Dimethylamino-trans-Styrenes on the Polarity in the Ground and Excited Singlet State
ABSTRACT The electric dipole moment in the ground (μg) and in the first excited singlet state (μe) of co-substituted acceptors in 4-dimethylamino-trans-styrenes (Z = P(S)Ph2 , P(O)Ph2 , SO2CH3 ) were determined by solvatochromic and thermochromic methods. The obtained values of μe and μg and the values for Z = CN and Z = NO 2 known from the literature [2] fulfill the linear relation between the dipole moments (μe or μg and the Hammett constants σp of the substituents. On pincreasing the electron-acceptor power of Z, μe grows faster than μg
Molecular Relaxation Processes During Film Formation
Traditionally many coatings and polymer chemists and physicists who follow the increase in viscosity of coating materials as changes occur during drying, use only one-point or steady-state methods for monitoring the ‘cure’. Insight can be gained by determining a flow curve at various shear rates for coating binders and formulations. However, as a proper formulated coating begins the process of changing from a liquid which generally flows readily to a solid coating, all are viscoelastic in nature. Such is the case with industrial, architectural or special protective coatings manufactured by the paint industry and printing inks, adhesives, paper coatings or other similar types. Only a few materials of commercial importance are not viscoelastic in normal usage, e.g. some Newtonian oils. Since this is the case, it is important for scientists not only to measure the viscosity of a coating but also to know something about the elastic response of the material.
THE IRON-ACETOCARMINE METHOD OF FIXING AND STAINING CHROMOSOMES
A short description of this procedure was given in Vol. 55 of the American Naturalist, pp. 573â€”574. The method has now been used almost daily for five years, and certain improvements have suggested themselves. The solution can be prepared by mixing about equal volumes of glacial acetic acid and water. To this is added powdered carmine in excess. The liquid is then â€ ? just brought to boil, cooled, and decanted. To the red solution there are then added a few drops of a solution of ferric hydrate in 50 per cent. acetic acid, to act as a mordant. The amount of iron varies with different objects. Too much produces a precipitate in a short time. The more