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Gold Number

0.25 g lyophi...

Question

0.25 g lyophilic colloid is added to 100 ml gold solution to prevent the coagulation on adding 1 ml 10% NaCl solution. What will be gold number of lyophilic colloid?

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Solution

“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.”

0.25 g lyophilic colloid is added to 100 ml gold solution
so 250 mg lyophilic colloid is added to 100 ml gold solution
so 25 mg lyophilic colloid is added to 10 ml gold solution
so answer will be 25

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Q. Lyophilic colloidal sols are much more stable than lyophobic colloidal sols. This is due to the extensive solvation of lyophilic colloidal sols, which form a protective layer outside it which prevents it from forming associated colloids. Lyophilic colloidal sols also protect lyophobic colloidal sols from precipitation by the action of electrolytes. This is due to the formation of a protective layer by the lyophilic sols outside lyophobic sols. Lyophilic sols are also called protective sols.
Gelatin (lyophilic) protects gold sol (lyophobic) from coagulation on the addition of a solution of sodium chloride. The protective powers of different colloidal sols are measured in terms of gold number.
Gold number is defined as the amount of protective sol in milligrams that prevents the coagulation of 10 mL of a given gold sol on adding 1 mL of a

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