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对粉尘中游离二氧化硅(SiO2)含量测定的焦磷酸质量法进行改进,并建立其操作规程。采用磷酸直接加热溶解<200目的粉尘样品,降低焦磷酸处理样品温度,增加硝酸铵的加入量处理硫化矿物,滤膜采集的粉尘样品的过滤采用抽滤。用改进后的操作规程对比分析,同时测定实际样品及石英混合样品。结果显示,改进前后实际样品检测结果相对偏差为2.95%,测得石英回收率约为95%,实际样品测定的相对标准偏差为0.28%～2.80%,硝酸铵的加入量增加到数百毫克使硫化矿物完全溶解,微孔滤膜抽滤可避免滤膜采集的粉尘样品发生透滤。用改进后的焦磷酸质量法测定工作场所粉尘中游离SiO2含量,简化了操作规程,避免了样品溶解时胶体的产生,排除了硫化矿物的干扰,解决了样品粒度过细时透虑带来的测定误差,此规程适用于工作场所粉尘中游离SiO2的测定。
Improve the pyrophosphoric acid quality method for the determination of free silicon dioxide (SiO2) in dust and establish its operating procedures. The phosphoric acid was directly heated to dissolve the dust sample of <200 mesh, the temperature of pyrophosphoric acid treatment sample was reduced, and the addition of ammonium nitrate was added to treat the sulphide minerals. The filtration of the dust sample collected by the filter membrane was filtered by suction. With the improved operating procedures comparative analysis, simultaneous determination of the actual samples and quartz mixed samples. The results showed that the relative deviation of the actual sample before and after the improvement was 2.95%, the recovery rate of quartz was about 95%, the relative standard deviation of the actual sample was 0.28% ~ 2.80%, the addition of ammonium nitrate increased to hundreds of milligrams Sulfide minerals are completely dissolved, and microporous membrane filtration can prevent diafiltration of the dust samples collected by the membrane. Using the improved pyrophosphate quality method to measure the free SiO2 content in the workplace dust, simplifying the operation procedure, avoiding the colloid production when the sample is dissolved, eliminating the interference of sulphide minerals and solving the measurement brought by the fearing when the grain size is too small Error, this procedure applies to the determination of free SiO2 in workplace dust.