The following are statements regarding sodium carbonate

i) The formula of salt soda is ${\text{Na}}_{\text{2}}{\text{CO}}_{\text{3}}.\text{1}0{\text{H}}_{\text{2}}\text{O}$

ii) Black ash is a mixture of ${\text{CaCO}}_{\text{3}}{\text{+Na}}_{\text{2}}\text{S}$

iii) The principle involved in the preparation of ${\text{Na}}_{\text{2}}{\text{CO}}_{\text{3}}$ by Solvay process is very low solubility of ${\text{NaHCO}}_{\text{3}}$