Use the pipette to absorb 5 ml acid sample and inject it in the conical flask, add 90 ml demineralized water and shake it well, drop 2 ~ 3 drops of methyl orange indicator, then use 1 mol/L NaOH standard solution for titration, until the solution turns into orange, record the consumption volume of NaOH standard solution, the calculation is as follows
                        a×M×36.5
        HCl%=                         ×100%=0.73a%
                         V·d·103
where：
a—showing  the consumed volume of NaOH standard solution for tritration，mL.
M—Showing  the molar concentration of NaOH，mol/L.
36.5—showing the molar mass of hydrochloric acid，g/moL.
V—refers to the volume of acid samples，mL.
d— refers to the specific gravity of acid sample，about。(zjl)