Take the acid 1 ml into the conical flask, add 100 ml demineralized water and shake it well, drop 2 ~ 3 drops of methyl orange indicator, then use 1 M  NaOH standard solution for titration, until the solution turn into yellow orange, record the consumption volume of NaOH standard solution, the calculation formula is as follows:
                              a·m·40
        NaOH%=                          ×100%=0.8b%
                             V·d·1000
        where ：
a- showing the consumed volume of NaOH standard solution for tritration, mL.
M - showing the molar concentration of NaOH for titration , 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, mL.