Identify the correct statement$(s)$ from the following:
$a$) Protective power of a lyophilic sol is more if its gold number is more
$b$) In the coagulation of negative sols,the coagulating power of cations follow the order $Na^{+} > Ba^{2+} > Al^{3+}$
$c$) Cloud is a solid in gas type of colloid
$d$) Physical adsorption is non-specific and multilayered at high pressure.

Which of the following statements are not true?

Indicator type silica gel used as a dehumidifier contains

Adding soap to water ................

Identify the correct statements from the following.
$(i)$ In the oxidation of oxalic acid with $KMnO_4$ in acid medium, $Mn^{2+}$ acts as an autocatalyst.
$(ii)$ $CdS$ colloidal solution can be precipitated by the addition of $Cl^{-}$ ions.
$(iii)$ The gold numbers of three protective colloids $(A, B, C)$ are $0.03$, $25$, and $0.25$ respectively. Their protective power follows the order $A > C > B$.
$(iv)$ Physisorption is an irreversible process.

Sodium thiosulphate is used in photography to :-