In analytical chemistry, sodium hydroxide and potassium hydroxide can often be used interchangeably with Du.

但有些應用場zhi合，兩者不能換用。

However, in some application fields, the two can not be replaced.

比如氫氣發dao生器，指定用氫氧化鉀。

For example, hydrogen generating Dao generator is specified to use potassium hydroxide.

醫用鈉石灰，指定用氫氧化鈉。

Sodium lime for medical use, sodium hydroxide as specified.

氫氧化鈉的吸濕性要比氫氧化鉀強，所以在化學分析中要常用氫氧化鉀。同理要是使用它作干燥劑時就要用氫氧化鈉。比如你說的醫用鈉石灰，指定用氫氧化鈉。但是兩個的氫氧化鈉要便宜一些，可以替換時要氫氧化鈉。

The hygroscopicity of sodium hydroxide is stronger than that of potassium hydroxide, so potassium hydroxide is commonly used in chemical analysis. Similarly, if it is used as a desiccant, sodium hydroxide should be used. For example, for medical sodium lime, sodium hydroxide is specified. But the price of two sodium hydroxide is cheaper, and sodium hydroxide is needed when it can be replaced.

二者都有強腐蝕性，不可與金屬容器接觸，且易潮解，應密封保存。

Both of them have strong corrosivity, can't contact with metal container, and are easy to deliquescence. They should be sealed and stored.

保存運輸方法上二者無差別。

There is no difference in the method of preservation and transportation.

氫氧化鈉的物性：

The physical properties of sodium hydroxide are as follows

純品為無色透明晶體，相對密度2.130。熔點318.4℃。沸點1390℃。市售燒堿有固態和液態兩種：純固體燒堿呈白色，有塊裝、片狀、棒狀、粒狀，質脆；純液體燒堿為無色透明液體。固體燒堿有很強的吸濕性。易溶于水，溶解時放熱，水溶液呈堿性，有滑膩感；溶于乙醇和甘油；不溶于丙酮、乙醚。腐蝕性極強，對纖維、皮膚、玻璃、陶瓷等有腐蝕作用。與金屬鋁和鋅、非金屬硼和硅等反應放出氫；與氯、溴、碘等鹵素發生歧化反應；與酸類起中和作用而生成鹽和水。

The purity is colorless and transparent crystal with relative density of 2.130. Melting point 318.4 ℃. Boiling point 1390 ℃. There are two kinds of caustic soda sold in the market: pure solid caustic soda is white, with block, flake, rod, granular and brittle; pure liquid caustic soda is colorless and transparent liquid. Solid caustic soda has strong hygroscopicity. It is soluble in water and exothermic when dissolved. The aqueous solution is alkaline and greasy; soluble in ethanol and glycerin; insoluble in acetone and ether. It has strong corrosivity and corrodes fibers, skin, glass, ceramics, etc. It reacts with aluminum and zinc, non-metallic boron and silicon to give out hydrogen, disproportionation with halogen such as chlorine, bromine and iodine, neutralizing with acids to form salt and water.

氫氧化鉀的物性：

The physical properties of potassium hydroxide are as follows

白色斜方結晶，工業品為白色或淡灰色的塊狀或棒狀。相對密度2.044(20℃)。熔點360.4℃。沸點1320～1324℃。易溶于水，溶解時放出大量溶解熱，有極強的吸水性，在空氣中能吸收水分而溶解，并吸收二氧化碳逐漸變成碳酸鉀。溶于乙醇，微溶于醚。有極強的堿性和腐蝕性，其性質與燒堿相似。

White orthorhombic crystal, industrial products are white or light gray block or rod. The relative density was 2.044 (20 ℃). The melting point is 360.4 ℃. The boiling point is 1320 ～ 1324 ℃. It is easy to dissolve in water. When dissolved, it releases a large amount of heat of dissolution. It has strong water absorption. It can absorb water and dissolve in the air, and absorb carbon dioxide and gradually turn into potassium carbonate. Soluble in ethanol, slightly soluble in ether. It has strong alkalinity and corrosivity, and its properties are similar to that of caustic soda.