北京大学：《放射化学》课程教学资源（课件讲稿，1/2）Radiochemistry（主讲教师：刘春立）

放射化学 Radiochemistry 2005-9-13 NECPKU

本课程的基本内容 ■前言、核性质(~6学时) ■统计性质(~4学时) ■核衰变 (~4学时) ■探测器 (~2学时) ■核反应 (~4学时) ■辐射防护 (~2学时) ■核分析 (~2学时) ■示踪方法 (~2学时) ■基础应用(~2学时) 北力淳 2005-9-13 NECPKU

放射化学 Radiochemistry ■主要硏究放射性核素和核转变产物的化学性质 和行为 ■研究它们的制备、分离、纯化及鉴定方法; ■研究放射性标记化合物的合成和性质; ■研究放射性核素及其标记化合物在化学、生 物、医学和其他科学技术领域以及在工农业生 立中的应用。 选自:叶明吕主编张庆喜主审《放射化学实验》(第二版), 原子能出版社,1991 北力淳 2005-9-13 NECPKU

Radiochemistry The branch of chemistry dealing with radioactive phenomena (From Webster's New World Dictionary, Third college Edition, p1108) n放射化学是化学的一个分支,是研究有 关放射性现象的一门科学。 北力淳 2005-9-13 NECPKU

放射化学研究方法的创立 ■1898年春天M. Curie发现沥青铀矿的放射性比 纯铀的放射性约大四倍,因而推测在沥青铀矿 中还有一种放射性更强的放射性元素。 ■将沥青铀矿磨碎溶解于盐酸,进行硫化物沉淀等多步化学分 离 ■在整个分离过程中,始终用跟踪放射性的办法,来确定大量其 它元素中微量放射性元素的去向; ■并巧妙地根据放射性的行踪来判断该元素的某些化学性质。 这种创造性的方法,是一种崭新的放射化学研究方法 北力淳 2005-9-13 NECPKU

Discovery of radium 2005-9-13 NECPKU

Discovery of radium Flow Chart of the Major Steps in the Separation and Purification of Radium from Pitchblende Based on Procedure described in Marie Curie's Thesis) Pitchblende ore Crush and treat with sodium carbonate Wash with warm water and dissolve in dilute sulphuric acid Yield: 1 ton: Radioactivity 4 times that of uranium Supernatant contains uranium Residue: Sulphates of Pb, Ca, silica, alumina, iron oxide. small amounts of Cu, Bi, Zn, co, Mn, Ni, Va, Sb, Th, rare Processed for uranium earths, niobidium, Ta, As, Ba, etc. Radium present as sulphate Boil with sodium hydroxide solution to remove sulfuric acid reat with hydrochloric acid 2005-9-13 NECPKU

Discovery of radium Treat with hydrochloric acid Solution Insoluble part (Po. Ac) Wash with water and boil with sodium carbonate to For separation of convert Ra and Ba sulphates to carbonates Wash with water, then with dilute hydrochloric acid Precipitate with sulphuric acid(contains Ra, Ba, Ca, Pb, Fe, etc. Yield: 10-20 kg. times of uranium Boil with sodium carbonate, treat with hydrogen su oxidize with chlorine and precipitate with pure alumilyphide 2005-9-13 NECPKU

Discovery of radium Continued Yield: 8 kg: Activity: 60 times more active than uraniu Precipitate(Ac) Supematant: Precipitate with sodium carbonate (Carbonates of alkali earth, Ra, Ba, etc. Wash the precipitate convert carbonates to chloride solution Fractional crystallisation(FC)with pure water Crystals enriched in Ra by Supernatant(B) a factor of five(5). Repeat Crystals(A) FC with both a and B Evaporate to FC dryness, FC 2005-9-13 NECPKU

Discovery of radium Evaporate to dryness, FC Supernatant I Supernatant Crystals FC More active p of B is combined with less active part of A SupernatantCrystals Supernatant FC Supernatant rystals Supernatant Crystals FC continued for 6 stages: -Activity of the most soluble fraction decreases each time, when it becomes negligible, it is discarded; -At some stage the most active crystals are withdrawn from further FC and pooled: Final yield was nearly 100 mg of pure radium chloride; -Activity nearly 2 x 10 times that of equal weight of uranium 2005-9-13 NECPKU