Abstract
Water bridges formed among particles in industrial process often contain soluble impurities such as salts. When such bridges are exposed to dry air, water in the bridges vaporizes and the salts crystallize to form solid bridges.
Solid bridges between two glass spheres were formed from NaCl, KCl, KNO3 and Na2SO4 solution by controlling the humidity, and their tensile strength was measured. It was found from these experiments that 1) the adhesion force of a solid salt bridge which was uniformly formed in the gap between two spheres was one to two orders of magnitude larger than that of a water bridge without crystallization; 2) the average adhesion force of solid bridges was proportional to the 1/2 power of the product of salt volume and particle radius; and 3) the adhesion force of bridges of NaCl and KCl was influenced by the surrounding humidity, which it was below their deliquescent points, because they adsorbed water until complete recrystallization took place.
† This report was originally printed in KAGAKU KOGAKU RONBUNSHU 20(4), 542-548 (1994) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Chemical Engineers, Japan.
