Na_2CO_3属质子(Br(?)nsted)碱,可用标准HCl 溶液直接滴定。其滴定曲线有两个突跃,第一个突跃相当于:CO_3~(2-)+H~+—→HCO_3~-第二个突跃相当于:HCO_3~-+H~+—→H_2CO_3(?)在第一等当点由于HCO_3~-的缓冲作用,突跃不很明显,以酚酞褪色作为终点很难观察,误差较大。一般是滴定至第二等当点, Na_2CO_3 is a proton (Br (?) Nsted) base, available standard HCl solution titration. The titration curve has two jumps, the first jump is equivalent to: CO_3 ~ (2 -) + H ~ + - → HCO_3 ~ - The second jump is equivalent to: HCO_3 ~ - + H ~ + - → H_2CO_3 (?) At the first equivalence point, due to the buffering effect of HCO 3 ~ -, the jump is not very obvious. It is difficult to observe the fading of phenolphthalein as the end point, and the error is larger. Titration is generally the second equivalent point,