Which of the following processes does $NOT$ result in coagulation?

The gold numbers of gelatin, haemoglobin and sodium acetate are $5 \times 10^{-3}$, $5 \times 10^{-2}$ and $7 \times 10^{-1}$, respectively. The protective actions will be in the order

The size of colloidal particles is:

The charge of $SnO_2$-sol in alkaline and acidic medium are respectively (Hint: $SnO_2$ is amphoteric oxide).

The mass of Haemoglobin in $mg$ required to protect from coagulation of $50 \ mL$ of a gold sol on adding $5 \ mL$ of $10 \% NaCl$ solution is: (Gold number of Haemoglobin $= 0.03$)

The simplest way to check whether a system is colloidal,is