焦硫酸钠熔融-电位滴定法和四苯硼钾重量法分别测定钾冰晶石中铝和钾  

Respective determination of aluminum and potassium in potassium cryolite by sodium pyrosulfate melting potentiometric titration and potassium tetraphenylborate gravimetry

作　　者：王秀莉[1] 宋丹丹[1] 尚玉俊[1] 张金玉 WANG Xiuli;SONG Dandan;SHANG Yujun;ZHANG Jinyu(High and New Technology Research Center of Henan Academy of Sciences,Zhengzhou 450002,China)

机构地区：[1]河南省科学院高新技术研究中心,河南郑州450002

出　　处：《冶金分析》2024年第4期57-64,共8页Metallurgical Analysis

基　　金：河南省重点研发与推广专项(科技攻关)项目(No.212102310080);郑州市基础研究及应用基础研究专项项目(No.gy21002);中央公益性科研院所河南省科学院基本科研费项目(No.220602024)。

摘　　要：为保证钾冰晶石钎剂的产品品质及其焊件的产品质量,需准确确定其K/Al分子比。X射线荧光光谱法(XRF)存在标准样品制备复杂、基体校正相对困难等问题,无法满足准确定量的要求。化学湿法分析通常需要分次熔样,过程较为繁琐。实验采用6 g焦硫酸钠于700℃熔融分解样品30 min。通过过量EDTA-氟化物置换法,于574 nm波长下采用动态等当点滴定(DET)模式用ZnCl_(2)标准滴定溶液电位滴定置换出的EDTA,有效解决了钾冰晶石中铁、钛等金属杂质离子对铝含量测定的干扰问题,建立了自动电位滴定法测定钾冰晶石中铝的方法。碱性条件下以最初6~8 s每滴、之后2~3 s每滴的速度加入10 mL沉淀剂,并采用EDTA掩蔽铝、铁、钙、镁等离子,建立起四苯硼钾重量法测定钾冰晶石中钾含量的方法。通过焦硫酸钠一次熔样的前处理方法,避免了分次熔样的繁琐步骤。按照实验方法测定钾冰晶石实际样品中铝和钾,结果的相对标准偏差(RSD,n=6)小于0.2%;与其他方法(其中铝采用YS/T 273.4—2020中规定的EDTA滴定法测定,钾采用碱性氢氧化钠熔融-四苯硼钾重量法测定)的测定结果进行对比,绝对误差小于0.4%。It is necessary to accurately determine the molar ratio of K/Al in potassium cryolite in order to ensure the product quality of potassium cryolite brazing flux and its weldments.X-ray fluorescence spectrometry(XRF)has some problems such as the complicated preparation of standard sample and the difficulty of matrix correction,and cannot meet the requirements of accurate quantification.The chemical wet analysis method usually needs fractional melting of samples,and the determination process is cumbersome.In this study,the sample was melted and decomposed at 700℃ for 30 min using 6 g of sodium pyrosulfate.The excessive EDTA-fluoride replacement method was employed.The replaced EDTA was determined by potential titration using ZnCl_(2) standard titration solution at DET mode with the wavelength of 574 nm.The interference of metallic impurity ions such as iron and titanium with the determination of aluminum in potassium cryolite was solved effectively.The method for the determination of aluminum in potassium cryolite by potentiometric titration was established.Under alkaline conditions,10 mL of precipitant was added at the rate of 6 to 8 seconds per drop at beginning and then 2 to 3 seconds per drop.The ions such as aluminum,iron,calcium and magnesium were masked with EDTA.The method for the determination of potassium in potassium cryolite by potassium tetraphenylborate gravimetry was established.The pretreatment method of once sample melting with sodium pyrosulfate avoided the tedious steps of fractional melting of sample.The contents of aluminum and potassium in actual sample of potassium cryolite were determined according to the experimental method,and the relative standard deviations(RSD,n=6)of determination results were less than 0.2%.The determination results were compared with those obtained by other methods(the content of aluminum was determined by EDTA titration in YS/T 273.4-2020,and the content of potassium was determined by alkaline sodium hydroxide melting-potassium tetraphenylborate gravimetry),and the

关 键 词：钾冰晶石 焦硫酸钠 铝 钾 电位滴定法 四苯硼钾重量法 K/Al分子比 

分 类 号：O655.1[理学—分析化学] O655.2[理学—化学] TF031[冶金工程—冶金物理化学]