水玻璃砂中碳酸盐含量的测定

Determination of Sodium Carbonate in Water Glass Sand

将水玻璃砂样品(10~20g)置于测定装置的反应瓶中,并在吸收瓶中预先加入氢氧化钡标准溶液25.00mL,加水至吸收液的总体积为60mL,检查测定装置的气密性。向反应瓶中加入过量硫酸(1+9)溶液使样品中的碳酸盐反应定量释放出二氧化碳气体。反应时间约为0.5min。释出的二氧化碳导入吸收瓶中,与氢氧化钡反应生成碳酸钡沉淀。多余的氢氧化钡用盐酸标准溶液滴定,据此计算样品中碳酸盐的含量。为使吸收充分完全,采用内部强制循环吸收的方法并规定吸收时间至少15min,如样品中碳酸钠含量较高时,可延长吸收时间至20min或30min。试验时,加入标准碳酸钠量为0.104 7g,3次测定的平均值为0.106 5g,相对平均偏差为1.8%。

Sample of water glass sand(10-20g)was placed into the reaction flask of the analytical apparatus,and 25.00mL of standard solution of Ba(OH)2 were added to the absorption flask and diluted to 60mL with water.The apparatus should examined for air-tightness at this moment.An excess amount of H2SO4(1+9) was added to the reaction flask to react with the carbonate for ca.0.5min to liberate equivalent amount of CO2 which was led to the absorption flask and absorbed by Ba(OH)2to form precipitated BaCO3.The un-reacted Ba(OH)2was then titrated with standard HCl solution,and content of Na2CO3 was calculated indirectly from the titrant consumed.To attain full absorption of CO2by Ba(OH)2,compulsory recycling absorption in the absorption medium was adopted,with the time of absorption set at 15min and prolonged to 20min or 30min if necessary.It was shown that on the determination of a known quantity of Na2CO3of 0.104 7g,an average of 0.106 5g(n=3)were found by the proposed method,giving relative average deviation of 1.8%.