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!

二氧六環：沸點101.5℃，熔點12℃，折光率1.4424，相對密度1.0336。二氧六環能與水任意混合，常含有少量二乙醇縮醛與水，久貯的二氧六環可能含有過氧化物（鑒定和除去參閱乙醚）。二氧六環的純化方法，在500mL二氧六環中加入8mL濃鹽酸和50mL水的溶液，回流6~10h，在回流過程中，慢慢通入氮氣以除去生成的乙醛。

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.

冷卻后，加入固體氫氧化鉀，直到不能再溶解為止，分去水層，再用固體氫氧化鉀干燥24h。然后過濾，在金屬鈉存在下加熱回流8~12h，在金屬鈉存在下蒸餾，壓入饑絲密封保存。精制過的1，4‐二氧環己烷應當避免與空氣接觸。

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.