1、 The physical and chemical properties of the two are different:

1、氢氧化钾白色斜方结晶，工业品为白色或淡灰色块状及棒状。相对密度2.044(20℃)。熔点360.4℃。沸点1320～1324℃。易溶于水，溶解时放出大量溶解热，有极强的吸水性，在空气中能吸收水分而溶解，并吸收二氧化碳逐渐变成碳酸钾。溶于乙醇，微溶于醚。有极强的碱性和腐蚀性，其性质与烧碱相似。

1. Potassium hydroxide is white orthorhombic crystal, and industrial products are white or light gray block and rod. The relative density is 2.044 (20 ℃). Melting point 360.4 ℃. Boiling point 1320 ~ 1324 ℃. It is easily soluble in water. It emits a large amount of dissolution heat when dissolving. It has strong water absorption. It can absorb water and dissolve in the air, absorb carbon dioxide and gradually turn into potassium carbonate. Soluble in ethanol, slightly soluble in ether. It is highly alkaline and corrosive, and its properties are similar to caustic soda.

2、氢氧化钠为无色透明晶体，相对密度2.130。熔点318.4℃。沸点1390℃。氢氧化钠有固体和液体两种，纯固体状态时外观呈白色（有块装、片状、棒状、粒状）质脆；纯液体状态时外观为无色透明液体。氢氧化钠溶于水中会完全分解成钠离子与氢氧根离子，所以具有强碱性。在空气中容易变质成碳酸钠；与铝反应可以生成氢气。1986年，英国有一油罐车误装载重量百分率浓度为25%的氢氧化钠水溶液，氢氧化钠便与油罐壁的铝产生化学变化，导致油罐因内部压力过载而受损。

2. Sodium hydroxide is a colorless transparent crystal with a relative density of 2.130. Melting point 318.4 ℃. Boiling point 1390 ℃. There are two kinds of sodium hydroxide: solid and liquid. In the pure solid state, the appearance is white (block, flake, rod and granular) and brittle; In the pure liquid state, the appearance is colorless and transparent liquid. Sodium hydroxide dissolved in water will completely decompose into sodium ions and hydroxyl ions, so it has strong alkalinity. It is easy to deteriorate into sodium carbonate in air; Reaction with aluminum can produce hydrogen. In 1986, a British oil tank truck mistakenly loaded an aqueous sodium hydroxide solution with a weight percentage concentration of 25%. The sodium hydroxide changed chemically with the aluminum on the oil tank wall, resulting in permanent damage to the oil tank due to internal pressure overload.

二、化学分析中氢氧化钾和氢氧化钠可以互换使用。但有些应用场合，两者不能换用。比如氢气发生器，指定用氢氧化钾；医用钠石灰，指定用氢氧化钠。氢氧化钠的吸湿性要比氢氧化钾强，所以在化学分析中常用氢氧化钾；如果用作干燥剂就要使用氢氧化钠。

2、 Potassium hydroxide and sodium hydroxide can be used interchangeably in chemical analysis. However, in some applications, the two cannot be used interchangeably. For example, potassium hydroxide is specified for hydrogen generator; Sodium lime for medical use, sodium hydroxide is specified. Sodium hydroxide is more hygroscopic than potassium hydroxide, so potassium hydroxide is often used in chemical analysis; If used as a desiccant, use sodium hydroxide.

三、两者都有强腐蚀性，不可与金属容器接触，且易潮解，应密封保存。

3、 Both of them are highly corrosive, can not contact with metal containers, and are easy to deliquescence, so they should be sealed and stored.

四、皂化反应中，氧化钾制得是弱肥皂，而氢氧化钠制得的是硬肥皂。

4、 In saponification reaction, potassium oxide makes weak soap, while sodium hydroxide makes hard soap.

五、氢氧化钾的行情比氢氧化钠高很多。

5、 The market price of potassium hydroxide is much higher than that of sodium hydroxide.

六、两者应用区别：

6、 Application differences between the two:

1、氢氧化钾用作分析试剂、皂化试剂、干燥剂及水分的吸收剂；用于制草酸及各种钾盐；电镀、雕刻、石印术等；还用于印染、漂白和丝光，并大量用作制造人造纤维、聚酯纤维的主要原料，也用于制造三聚氰胺染料。

1. Potassium hydroxide is used as analytical reagent, saponification reagent, desiccant and water absorbent; Used for preparing oxalic acid and various potassium salts; Electroplating, engraving, lithography, etc; It is also used in printing and dyeing, bleaching and mercerization, and is widely used as the main raw material for the manufacture of man-made fibers and polyester fibers, as well as melamine dyes.

2、氢氧化钠用于生产纸、肥皂、染料、人造丝、冶炼金属、石油精制、棉织品整理、煤焦油产物提纯以及食品加工、木材加工及机械工业等方面。

2. Sodium hydroxide is used in the production of paper, soap, dyes, rayon, metal smelting, petroleum refining, cotton fabric finishing, coal tar product purification, food processing, wood processing and machinery industry.