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

1、氫氧化鉀白色斜方結晶，工業品為白色或淡灰色塊狀及棒狀。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。

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、氫氧化鈉為無色透明晶體，相對密度2.130。熔點318.4℃。沸點1390℃。氫氧化鈉有固體和液體兩種，純固體狀態時外觀呈白色（有塊裝、片狀、棒狀、粒狀）質脆；純液體狀態時外觀為無色透明液體。氫氧化鈉溶于水中會完全分解成鈉離子與氫氧根離子，所以具有強堿性。在空氣中容易變質成碳酸鈉；與鋁反應可以生成氫氣。1986年，英國有一油罐車誤裝載重量百分率濃度為25%的氫氧化鈉水溶液，氫氧化鈉便與油罐壁的鋁產生化學變化，導致油罐因內部壓力過載而受損。

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、化學分析中氫氧化鉀和氫氧化鈉可以互換使用。但有些應用場合，兩者不能換用。比如氫氣發生器，指定用氫氧化鉀；醫用鈉石灰，指定用氫氧化鈉。氫氧化鈉的吸濕性要比氫氧化鉀強，所以在化學分析中常用氫氧化鉀；如果用作干燥劑就要使用氫氧化鈉。

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、兩者都有強腐蝕性，不可與金屬容器接觸，且易潮解，應密封保存。

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、皂化反應中，氧化鉀制得是弱肥皂，而氫氧化鈉制得的是硬肥皂。

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

五、氫氧化鉀的行情比氫氧化鈉高很多。

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

六、兩者應用區別：

6、 Application differences between the two:

1、氫氧化鉀用作分析試劑、皂化試劑、干燥劑及水分的吸收劑；用于制草酸及各種鉀鹽；電鍍、雕刻、石印術等；還用于印染、漂白和絲光，并大量用作制造人造纖維、聚酯纖維的主要原料，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、氫氧化鈉用于生產紙、肥皂、染料、人造絲、冶煉金屬、石油精制、棉織品整理、煤焦油產物提純以及食品加工、木材加工及機械工業等方面。

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.