so、so that、that在引导状语从句时有时可以互换。《英汉大词典》（陆谷孙）that词条：[引导状语从句，表示目的]We eat that we may live.Merriam-Webster that词条：[used as a function word to introduce a subordinate clause expressing purpose or desired result]cutting down expenses that her son might inherit an unencumbered estate不过建议在阅读时偶尔碰到了知道有这么个用法，避免在写作中使用，毕竟权威依据较少，平时见到的例子也比较少。