In many chemical experiments, a water free environment is needed. The anhydrous environment includes the environment, raw materials and other factors. The environment is easy to understand and can be completed only by using desiccant. How can the water molecules in the raw materials be removed? Take the use of potassium hydroxide water purification dioxane as an example, to introduce the use of potassium hydroxide water removal method!

二氧六环：沸点101.5℃，熔点12℃，折光率1.4424，相对密度1.0336。二氧六环能与水任意混合，常含有少量二乙醇缩醛与水，久贮的二氧六环可能含有过氧化物（鉴定和除去参阅乙醚）。二氧六环的纯化方法，在500mL二氧六环中加入8mL浓盐酸和50mL水的溶液，回流6~10h，在回流过程中，慢慢通入氮气以除去生成的乙醛。

Two oxygen six rings: boiling point 101.5 ℃, melting point 12 ℃, refractive index 1.4424, relative density 1.0336. Dioxane can be mixed with water at will and often contains a small amount of diethanol acetal and water. Dioxane stored for a long time may contain peroxide (see ether for identification and removal). For the purification method of dioxane, 8ml concentrated hydrochloric acid and 50ml water solution were added into 500ml dioxane and refluxed for 6-10h. During the reflux process, nitrogen was slowly introduced to remove the generated acetaldehyde.

冷却后，加入固体氢氧化钾，直到不能再溶解为止，分去水层，再用固体氢氧化钾干燥24h。然后过滤，在金属钠存在下加热回流8~12h，在金属钠存在下蒸馏，压入饥丝密封保存。精制过的1，4‐二氧环己烷应当避免与空气接触。

After cooling, add solid potassium hydroxide until it can not be dissolved again, separate the water layer, and then dry it with solid potassium hydroxide for 24h. Then, it was filtered, heated and refluxed in the presence of sodium metal for 8-12 h. finally, it was distilled in the presence of sodium metal, and then pressed into the vacuum wire for sealing preservation. The refined 1,4 ‐ dioxane should be kept away from contact with air.