提出了测定化铣钛合金的腐蚀溶液中HNO₃、HF及Ti（Ⅳ）浓度的新方法。①取适量样品，在50 mL乙醇（2+3）溶液中，与1.000 g KNO₃反应，使样品中的H₂TiF₆转化为K₂TiF₆沉淀并同时生成HNO₃，借此抑制Ti（Ⅳ）的水解反应。用0.500 mol·L^-1 NaOH溶液作滴定液，耐氢氟酸pH电极作指示电极，用电位滴定法测定所取样品的总酸度。②另取适量样品，加入已知且过量的0.500 mol·L^-1 NaOH溶液，在60℃反应20 min，使Ti（Ⅳ）生成Ti（OH）₄沉淀，随即用0.500 mol·L^-1 HCl溶液电位滴定法测定体系中过量的氢氧化钠，据此计算样品中Ti（Ⅳ）的浓度。③取5.00 mL样品，加入水50 mL，用NaOH溶液调节pH至6.0~8.0，用水定容至100 mL，分取溶液5.00 mL，加入pH 6.5的六次甲基四胺缓冲溶液10 mL，加水至约60 mL，用0.016 7 mol·L^-1 La（NO₃）₃溶液为滴定剂，氟离子选择电极为指示电极，电位滴定法测定样品中的总氟化物浓度。按所给公式分别计算样品中HNO₃、HF及Ti（Ⅳ）的浓度。用标准HNO₃、HF及H₂TiF₆配制的合成样品，按所提出方法分析所得结果均与理论值相符。以生产线实际样品为基础作加标回收试验，测得HF、Ti（Ⅳ）及HNO₃的回收率依次在97.8%~101%，98.9%~99.7%，97.8%~103%之间。

A new method of potentiometric titration for determination of HNO₃, HF and Ti(Ⅳ) in etching solution for chemical milling of titanium alloys was proposed. ① For determination of total acidity, an appropriate amount of the etching solution was reacted with 1.000 g of KNO₃ in a solution containing 30 mL of water and 20 mL of ethanol, to restrain the hydrolysis of TiF₆^2- by transforming H₂TiF₆ into precipitate of K₂TiF₆ and HNO₃; and total acidity was titrated potentiometrically with 0.500 mol·L^-1 NaOH solution using HF-resistent pH electrode as indicator. ② For determination of Ti(Ⅳ), an appropriate amount of the sample was reacted with an excess and definite amount of 0.500 mol·L^-1 NaOH solution at 60℃ for 20 min to precipitate Ti(Ⅳ) as Ti(OH)₄, and the excess of NaOH in the solution was titrated with 0.500 mol·L^-1 HCl solution potentiometrically, then the concentration of titanium(Ⅳ) in the sample was calculated. ③ For determination of total fluoride, 5.00 mL of the sample were taken, and after addition of 50 mL of water, its acidity was adjusted to between pH 6.0 to 8.0 with NaOH solution, and its total volume was made up to 100 mL. An aliquot of 5.00 mL was taken, after addition of 10 mL of hexamethylenetetramine buffer solution (pH 6.5) and dilution to 60 mL with water, it was titrated potentiometrically with 0.016 7 mol·L^-1 La(NO₃)₃ solution using F^- selective electrode as indicator. Based on the data obtained, concentration of HNO₃, HF and Ti(Ⅳ) in the sample were calculated by the formulas given. In the analysis of simulated samples with addition of standards of HNO₃, HF and H₂TiF₆, by the proposed method, the results obtained were in consistency with the theoratical values. Tests for recovery were made on the base of substantial samples collected from production front, values of recovery found were in the ranges of 97.8% to 101% for HF, 98.9% to 99.7% for Ti(Ⅳ) and 97.8% to 103% for HNO₃.