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市售芒硝,皮硝居多;市售玄明粉,也是皮硝风化干燥制品居多。因常含不溶物,测定其中硫酸钠的含量可按下法进行(试剂均按药典方法配制):取本品(105℃干燥至恒重的干燥品)约1.2g,精密称定,置于50ml 烧杯中,加水20ml 使溶解,用快速定性滤纸滤入100ml 容量瓶中,洗净烧杯、滤纸和漏斗,洗液并入容量瓶中,用水稀释至刻度。精密吸取此溶液25ml,置于250ml 烧杯中,加水75ml 和稀盐酸2 ml(或盐酸0.5ml),煮沸,不断搅拌并缓缓加入热氯化钡试液(约20ml)至不再发生沉淀,置水浴上加热30分钟,静置1小时,用慢速定量滤纸或称定重量的古氏坩埚滤过,沉淀用水分次洗涤,至洗液不再显氯化物的反应,干燥,并炽灼至恒重,精密称定,与0.6086相乘,即得供试量中含有Na_2SO_4的重量。
Commercially available Glauber’s salt, Pi Ni mostly; Xuan Ming commercial powder, but also weathered skin drying products are mostly. Since insoluble substances are often contained, the content of sodium sulphate can be determined according to the following methods (reagents are prepared according to Pharmacopoeia method): Take about 1.2 g of this product (105 °C dry to constant weight), accurately weighed and placed In a 50 ml beaker, add 20 ml of water to make it dissolve. Filter into a 100 ml volumetric flask with a quick qualitative filter paper. Wash the beaker, filter paper, and funnel. The wash solution is introduced into a volumetric flask and diluted with water to the mark. Accurately take this solution 25ml, placed in a 250ml beaker, add water 75ml and dilute hydrochloric acid 2ml (or 0.5ml hydrochloric acid), boil, stirring constantly and slowly add hot guanidinium chloride test solution (about 20ml) to no longer precipitate, Set on a water bath for 30 minutes, let stand for 1 hour, filter with a slow speed filter paper or a fixed weight of Oldham’s crucible, wash the precipitate with water, until the wash solution is no longer showing chloride reaction, dry, and ignite. To constant weight, accurately weighed, multiplied by 0.6086, that is, the weight of Na_2SO_4 contained in the test sample.