硫化钐中硫和钐的分离与测定

研究了一种可同时测定硫化钐中硫和钐含量的方法。硫化钐样品经氢氧化钠、过氧化钠熔融,将负二价硫全部氧化为正六价,经两次氨水分离,滤液在pH值为2~5的条件下,煮沸加入氯化钡溶液沉淀硫酸根,计算硫含量;氨水分离两次后的氢氧化钐沉淀经盐酸酸化后,用EDTA标准溶液滴定,测定钐含量。通过正交实验确定了熔样条件为550 ℃熔融10 min,氯化钡溶液沉淀硫酸根时沉淀不需陈化;由方差分析得出氨水分离次数和沉淀pH值为影响实验结果的显著因素,进一步试验确定氨水分离次数为2次、沉淀时pH值为2~5;此外,通过实验证明方法采用镍坩埚熔样所引入的镍并不影响测定结果。按实验方法对硫化钐样品进行精密度考察,硫和钐测定结果的相对标准偏差(RSD)分别为0.73%、0.18%;加标回收试验表明,硫和钐的回收率分别在101%~103%、100%~102%之间。采用实验方法对两个硫化钐样品进行测定,并分别与氯化钡滴定法测定硫及草酸盐重量法测定钐的结果进行对照,吻合较好。实验方法相比单元素测定法,避免了重复熔样,减少了样品预处理过程,实现了硫和钐的联合测定,可用于日常生产分析。

Separation and determination of sulfur and samarium in samarium sulfide

A simultaneous determination method of sulfur and samarium in samarium sulfide was studied. The samarium sulfide sample was fused with sodium hydroxide and sodium peroxide. The S^2- was totally oxidized to S⁶⁺. After separation twice with ammonia water, the filtrate at pH 2-5 was heated to boiling. The barium chloride solution was added to precipitate the sulfate. Then, the content of sulfur could be calculated. The samarium hydroxide precipitate was acidified with hydrochloric acid followed by titration with EDTA standard solution. Then, the content of samarium could be determined. The conditions were obtained by orthogonal experiments: fusion at 550 ℃ for 10 min;the aging was not required during the precipitation of sulfate using barium chloride solution. The variance analysis indicated that the ammonia water separation times and precipitation pH values were significant factors influencing the experimental results. The optimal separation times by ammonia water was twice, and the pH for precipitation was 2-5. In addition, the results proved that the experimental results were not affected by the nickel introduced in sample fusion from nickel crucible. The precision of samarium sulfide sample was investigated according to the experimental method. The relative standard deviation (RSD) for sulfur and samarium was 0.73% and 0.18%, respectively. The recovery test of standard addition indicated that the recoveries for sulfur and samarium were 101%-103% and 100%-102%, respectively. Two samarium sulfide samples were determined according to the experimental method, and then compared with the determination results of sulfur by barium chloride titration and samarium by oxalate gravimetry. The found results were in good agreement. Compared to the single element determination method, the repeated sample fusion was avoided in proposed method, reducing the pretreatment process of sample. The simultaneous determination of sulfur and samarium was realized. The proposed method could be used in routine production and analysis.