# Why would NaHO_4(s) in solution turn red litmas paper blue?

Red litmus paper turns blue under acidic conditions, so if $N a H {O}_{4} \left(s\right)$ in solution turns the litmus blue, has acidic properties.
I've never come across $N a H {O}_{4} \left(s\right)$ though. Are you sure it's not $N a H S {O}_{4}$ which is an acidic salt?