沧海月明
第2楼2007/10/12
在样品的盐酸溶液中加氯化钡,使硫酸盐生成白色硫酸钡沉淀,用定量滤纸过滤,烘干,灰化,灼烧至恒重。
称取5克样品,加100ml水,加热溶解,过滤到500ml容量瓶中,用水洗涤至无硫酸根离子为止(用氯化钡溶液检验),冷却,用水稀释到刻度,摇匀(溶液甲),准确汲取25ml溶液甲置于500ml烧杯中,加5ml1:1盐酸和270ml水,加热至微沸,不断搅拌滴加10ml0.5M氯化钡溶液,时间约需1.5min。继续搅拌并微沸2——3min,然后盖上表面皿,保持微沸5min。再把烧杯放在沸水浴上保持2H。将烧杯冷却到室温,用慢速定量滤纸过滤。用温水洗涤沉淀无氯离子为止(取5ml洗液,加5ml0.1N硝酸银溶液混匀,放置5min不出现混浊),将沉淀连同滤纸转移至已于800正负20℃恒重的瓷坩埚中,在110℃烘干,然后灰化,在800正负20℃下灼烧至恒重。
立静致远
第4楼2007/10/12
USP方法
weigh accurately a portion of sodium sulfate, equivalent to about 400mg of anhydrous sodium sulfate, dissolve in 200 ml of water, and add 1 ml of hydrochloric acid. heat to boiling, and gradually add, in small portions and while constantly stirring, and excess of hot barium chloride TS( about 8 ml).heat the mixture on a steam bath for 1 hour, collect the precipitate of barium sulfate on a tared filtering crucible, wash until free from chloride, dry, ignite, and weigh. the weight of the barium sulfate so obtained, multiplied by 0.6068, represents its equivalent of Na2SO4