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当我们作重量分析时,由溶液中分离出之沉淀,并非完全纯净者,它们或多或少总含有些杂质或母液。例如在高铁溶液中加入过量之氢氧化铵溶液,则铁可全部沉淀为氢氧化铁。以过量之氢氧化铵加入含有锌离子之溶液中,则锌形成复杂离子(Zn(NH_3)_4~(++))而存于溶液中。但若加过量之氢氧化铵于含有锌及铁离子之溶液中,则在氢氧化铁沉淀中可发现有少量锌离子存在;此种现象名为共沉淀现象。共沉淀现象在重量分析中颇为重要,因分析结果误差之主要来源系由此而起。再
When we do gravimetric analysis, the precipitates separated from the solution are not completely pure and they contain more or less total impurities or mother liquor. For example, in the high-speed iron solution by adding an excess of ammonium hydroxide solution, the iron can be all precipitated iron hydroxide. With an excess of ammonium hydroxide added to the solution containing zinc ions, the formation of complex ions of zinc (Zn (NH_3) _4 ~ (++)) and stored in solution. However, if an excessive amount of ammonium hydroxide is added to the solution containing zinc and iron ions, a small amount of zinc ions may be found in the iron hydroxide precipitate. This phenomenon is called coprecipitation. Coprecipitation is important in gravimetric analysis because of the main source of error in analytical results. again