How does dextrin prevent coagulation curdling of Silver Nitr

How does dextrin prevent coagulation (curdling) of Silver Nitrate?

Also, what factors must be considered in choosing a proper absorption indicator for precipitation titration and the reasonign behind each factor for I can fully understand please!

Thank you!

Solution

At equivalence point, neither titrant nor titrate ions are in excess and the precipitate is momentarily without a surface charge.This causes the colloidal particles to coagulatethereby reducing the precipitate surface charge. It can be prevented by the addition of a small amount of dextrin to the sokution as it provides charge to the surface which prevents coagulation

factors which should be considered in choosing a proper adsorption factor for precipitation:

1. The adsorption of indicator should start just before the equivalence point and increase rapidly at the equivalence point. Some unsuitable indicators are so strongly adsorbed that they actually displace the primary adsorbed ion well before the equivalence point is reached

2. It is preferrable that the indicator ion be opposite in charge to the ion added as the titrant adsorption of the indicator will then not occur till excess titrant is present.