Why Bleach + Ammonia is Dangerous

You’ve probably heard that you should never mix household bleach with ammonia.  With a little research I’ve discovered the reason why.  Bleach is a solution of sodium hypochlorite, and sodium hypochlorite and ammonia react to form a number of products, depending on the temperature, concentration, and how they are mixed.  To be more precise, in bleach sodium hypochlorite (NaOCl) dissociates into its ionic components

NaOCl → Na⁺ + OCl^-

 

 

OCl^- in turn reacts weakly with water to form:

 

 

OCl^- + H₂O → H⁺ + Cl^- + HOCl, in which the H⁺ + Cl^- portion is just hydrochloric acid.

 

 

Stronger reactions are:

 

 

NH₃ + OCl^- → OH^- + NH₂Cl

NH₂Cl + OCl^- → OH^- + NHCl₂

NHCl₂ + OCl^- → OH^- + NCl₃

The OH^- produced in the last three reactions are probably more than enough to neutralize the hydrochloric acid made by the second reaction.  More importantly, the NH_xCl_y compounds produced by the last three are severe irritants of the eyes and mucous membranes and are also toxic. NCl₃ can also be explosive, in high enough concentrations. There still other reactions that produce toxic chemicals, but this alone should account for why mixing bleach with ammonia is such a no-no.