Q49. In the precipitation of the iron group (III) in qualitative analysis, ammonium chloride is added before adding ammonium hydroxide to :\\
(1) increase concentration of $\mathrm { Cl } ^ { - }$ions\\
(2) increase concentration of $\mathrm { NH } _ { 4 } { } ^ { + }$ions\\
(3) prevent interference by phosphate ions\\
(4) decrease concentration of ${ } ^ { - } \mathrm { OH }$ ions