24小时热门版块排行榜

返回列表

当前只显示满足指定条件的回帖，点击这里查看本话题的所有回帖

xuyanglei

金虫 (小有名气)

应助: 2 (幼儿园)
金币: 1003.8
散金: 100
红花: 2
帖子: 137
在线: 92.7小时
虫号: 812357
注册: 2009-07-20
专业: 电化学

[求助] 请问 freeze-vacuum-thaw cycles 是什么怎么操作

请问 freeze-vacuum-thaw cycles 是什么具体怎么操作呢 O(∩_∩)O谢谢

回复此楼

» 猜你喜欢

药学硕士，第一、第二作者已发表6 篇 SCI，药理方向及相关方向2026年/2027年博士申请已经有4人回复
26年博士申请自荐-电催化已经有3人回复
中国地质大学（北京）博士招生补录，数理学院材料科学与工程专业和材料与化工专业已经有6人回复
收到国自然专家邀请后几年才会有本子送过来评已经有4人回复
考博已经有5人回复
26年申博自荐-计算机视觉已经有4人回复
药化及相关博士的申请已经有3人回复
一篇MDPI论文改变了学习工作和生活已经有4人回复

» 本主题相关价值贴推荐，对您同样有帮助:

外文中的提到的three freeze-pump-thaw cycles是什么意思？如何实现？？已经有7人回复

1楼 2013-07-10 11:11:13

已阅回复此楼关注TA 给TA发消息送TA红花 TA的回帖

life2006

木虫 (小有名气)

应助: 17 (小学生)
金币: 5940.5
红花: 4
帖子: 202
在线: 280.3小时
虫号: 374883
注册: 2007-05-18
性别: GG
专业: 高分子合成化学

【答案】应助回帖

★ ★ ★ ★ ★ ★
感谢参与，应助指数 +1
xuyanglei: 金币+6, ★★★很有帮助 2013-07-10 16:24:03

主要是用来除掉溶剂中的氧气，如果先加CaH2干燥,然后再进行真空转移之后进行freeze-pump-thaw的话可以制得无水无氧溶剂。具体操作如下：
Freeze-Pump-Thaw Degassing of Liquids
1) Place the solvent (or solution) in a Schlenk flask. Make sure the stopcock is closed. Be careful not to use more than 50% of the volume of the flask because overfilled flasks frequently shatter during this process.
2) Hook it up to a Schlenk line (leave the attached hose on vacuum throughout this procedure) and freeze the liquid. Liquid nitrogen is usually best for this. Before freezing make sure that the environment in the flask is free of oxygen to prevent condensing liquid oxygen upon freezing.
3) When the solvent is frozen, open the stopcock to vacuum and pump off the atmosphere for 10-30 minutes
4) Seal the flask.
5) Thaw the solvent until it just melts using a tepid water bath. You will see gas bubbles evolve from the solution. Try not to disturb the liquid. Note: Letting the frozen solvent thaw by itself, or using a container of water that melts only the bottom of the frozen solvent may cause the vessel to break.
6) Replace the water bath with the cooling bath and refreeze the solvent.
7) Repeat steps (3) – (7) until you no longer see the evolution of gas as the solution thaws. The solution should be put through a minimum of three cycles.
8) Fill the flask with nitrogen gas and seal. The solvent is ready to use.