Use the pipette to absorb 5 ml alkali sample and inject it in the conical flask, add 90 ml demineralized water and shake it well, drop 2 ~ 3 drops of phenothalin indicator, then use 1 mol/L hydrochloric acid standard solution for titration, until the solution turn into colorless from red, record the consumption volume of HCLI standard solution, the calculation is as follows:

                              b·m·40
        NaOH%=                         ×100%=0.8b%
                             V·d·1000
        where ：
        b—showing  the consumed volume of HCL standard solution for tritration，Ml.
        M—showing  the molar concentration of HCL for titration，mol/L.
        40—showing the molar mass of NaOH，g/moL。
        V—showing the volume of alkali sample，mL。
        d— showing the specific gravity of alkali sample ，about 1. (zjl)