In analytical chemistry in the sodium hydroxide and potassium hydroxide are often used interchangeably. But some of the applications, they cannot change. Such as hydrogen generator, specified with potassium hydroxide. Medical sodium lime, specified with sodium hydroxide. Sodium hydroxide hygroscopic than potassium hydroxide is strong, so the potassium hydroxide to commonly used in chemical analysis. In the same way if you use it as a desiccant with sodium hydroxide. For example, if you say that medical sodium lime, specified with sodium hydroxide. But two of the sodium hydroxide to cheaper price, when it can replace sodium hydroxide.
Both of them are highly corrosive and must not be in contact with metal containers, and they should be sealed and preserved. There is no difference between them.
The physical properties of sodium hydroxide:
Single product is colorless transparent crystal, relative density 2.130, melting point is 318.4 ℃. The boiling point of 1390 ℃. Caustic soda market is a solid and liquid two: pure white solid caustic soda, blocks, sheet, rod, granular, very brittle. Pure liquid caustic soda is a colorless transparent liquid. Solid caustic soda has a strong hygroscopicity. It is soluble in water, and when it is dissolved, it is very alkaline and has a feeling of greasy. Soluble in ethanol and glycerin; It is not soluble in acetone and ether. It is very corrosive and has corrosive effect on fiber, skin, glass and ceramics. Dismutation reaction with chlorine, bromine, iodine and other halogens; The salt and water are formed from the neutralization of acids.
The physical properties of potassium hydroxide:
White rhombic crystal, industrial products is white or light gray block or club-shaped. Relative density 2.044 (20 ℃), melting point is 360.4 ℃. The boiling point of 1320 ~ 1324 ℃. Soluble in water, dissolved when released a large number of solution heat, strong water absorption, can absorb the moisture in the air and dissolved, and gradually absorb carbon dioxide into potash. Soluble in ethanol, slightly soluble in ether. Strong alkali and corrosive, its properties are similar to those of caustic soda.
Content analysis: accurate said sample is about 1.5 g, soluble in 40 ml new boiling and cooling water, cold to 15 ℃, with phenolphthalein test solution (TS - 167) several drops, with 1 mol/L acid titration. When pink disappears, record the amount of acid consumed, add methyl orange test solution (TS -148), and continue titration until the pink is constant. Record the total volume of acids required for titration. Each Ml of 1mol/L of sulfuric acid is equivalent to 56.11mg of total alkalinity (KOH).