Question

On addition of the 1ml. solution of $10\%$ NaCl to 10ml gold sol in the presence of 0.00399gm of starch calculate the gold no.

Answer 1

Gold number is the protective power of a colloidal solution against coagulation.

Gold number = $\frac{\text{volume of gold sol coagulated}}{\text{weight of protective colloidal used}}$

In the question, 1 ml of $10\%$ NaCl.

Gold number = 1000 x 0.00399 = 4