练习材料：
Lesson38-3 Water and the traveller
Alcohol may be a medical disinfectant, but should not be relied upon to sterilize water. Ethanol is more effective at a concentration of 50-70 per cent; below 20 per cent, its bactericidal action is negligible. Spirits labelled 95 proof contain only about 47 per cent alcohol. Beware of methylated alcohol, which is very poisonous, and should never be added to drinking water.
If no other safe water supply can be obtained, tap water that is too hot to touch can be left to cool and is generally safe to drink. Those planning a trip to remote areas, or intending to live in countries where drinking water is not readily available, should know about the various possible methods for making water safe.
应用配置：L0+L4
知识笔记：Alcohol/ disinfectant/ bactericidal/ negligible/ poisonous/
练习感悟：用时31分。晨读。简书无法上传了。
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