What is Aqua dag?

Colloidal solution cannot be obtained from two such substances which are:

Which of the following colloids is $NOT$ a gel?

$Fe(OH)_3$ sol and gold sol are positively and negatively charged,respectively. Which of the following statements is incorrect?

If $1 \ mL$ of $10\% \ NaCl$ solution is added to $10 \ mL$ of gold sol containing $0.25 \ g$ of starch to prevent coagulation,what is the gold number of starch?

$X$ is a protecting colloid. The following data is obtained for preventing the coagulation of $10 \ mL$ of gold sol to which $1 \ mL$ of $10 \% NaCl$ is added. What is the gold number of '$X$'?

Expt. No.	Weight of $X$ (in $mg$) added to gold sol	Coagulation
$1$	$24$	Not prevented
$2$	$23$	Not prevented
$3$	$26$	prevented
$4$	$27$	prevented
$5$	$25$	prevented