论文部分内容阅读
定pH法测定单体硼纯度,国内至今未见报道。它比目前我国广泛使用的指示剂法准确、快速、精度高、适用性强。本文介绍该法的测定步骤及特点。1 测定步骤称取干燥单体硼约0.2g(精确到0.0002g)于200ml烧杯中,加少许水润湿,加浓硝酸10ml,立即盖皿,待其自发反应至无黄烟时,将烧杯置电炉上加热煮沸3～5min,取下,冷至室温,加水至总体积约50ml,用盐酸(1mol·L~(-1))和NaOH(0.5mol·L(-1))在已调整定位的酸度计上调整pH为5.10。向试液中加丙三醇(AR)10ml,以NaOH标准液(0.5mol·L~(-1))滴定至pH9.18(25℃时),再加丙三醇(AR)5ml,若此时pH<9.18,则继续滴至pH为9.18,如此重复至试液pH=9.18稳定止。若NaOH标准液浓度为C(mol·L~(-1)),滴至终点时耗用的体积为V(ml),所取试样质量为ms(g),则B%=0.01081C·V÷ms×100%。2 不同温度下的终点pH值
The pH determination of monomer purity of boron, so far no reports. It is more accurate, faster, more precise and more adaptable than the indicator method widely used in our country at present. This article describes the determination of the law steps and characteristics. 1 Determination step Weigh dry monomer boron about 0.2g (accurate to 0.0002g) in 200ml beaker, add a little water wet, add concentrated nitric acid 10ml, immediately cover the dish until the spontaneous reaction to no yellow smoke, the beaker set Heated on an electric cooker and boiled for 3 to 5 minutes, removed, cooled to room temperature, and added with water to a total volume of about 50 ml. After adjustment with a hydrochloric acid (1 mol·L -1) and NaOH (0.5 mol·L -1) PH adjusted to pH 5.10. Add 10ml of glycerol (AR) to the test solution and titrate it to pH9.18 (at 25 ° C) with NaOH standard solution (0.5mol·L -1), add 5ml of glycerol At this point pH <9.18, then continue to drop to a pH of 9.18, so repeated until the test solution pH = 9.18 stable only. If the concentration of NaOH standard solution is C (mol·L -1), the volume consumed when dropping to the endpoint is V (ml) and the sample mass is ms (g), B% = 0.01081C · V ÷ ms × 100%. 2 End point pH at different temperatures