Explain electro dilysis, Ultra filtration, coagulation value & Gold number.

Electrodialysis:

 

The normal process of dialysis is slow so in order to increase the process of purification, the dialysis is performed by applying electric field. This process is called as electrodialysis.

 

Ultra-filtration: 

Ultra-filtration (UF) is the physical removal of particles and microbiological contaminants from an aqueous solution using a membrane filter with pore sizes less than 0.1 micron.  It does not remove dissolved ions and small molecules.

Coagulation value: 

The minimum amount of electrolyte required to cause precipitation of one litre of colloidal solution is called coagulation value or flocculation value of electrolyte for the sol.

Gold number:

Gold number is defined as weight of the dried protective agent in milligrams, which when added to 10 ml of a standard gold sol (0.0053 to 0.0058%) is just sufficient to prevent a colour change from red to blue on the addition of 1 ml of 10 % sodium chloride solution, is equal to the gold number of that protective colloid. Thus, smaller is the gold number, higher is the protective action of the protective agent.