Physicochemical properties of salicylic acid

Salicylic acid is a fat soluble organic acid with the chemical formula c7h6o3. The appearance is white crystalline powder, and the melting point is 158 ~ 161 ℃. It exists in willow bark, white pearl leaves and sweet birch in nature. It is an important fine chemical raw material and can be used for the preparation of aspirin and other drugs.

Physicochemical properties of salicylic acid

Physical property

Appearance and properties: white acicular crystal or hairy crystalline powder.

Solubility: easily soluble in ethanol, ether and chloroform, slightly soluble in water and dissolved in boiling water.

Melting point: 159 ℃

Boiling point: 211 ℃, sublimation at 76 ℃.

Chemical property

Stable at room temperature. It is decomposed into phenol and carbon dioxide by rapid heating. It has the generality of some acids. This product stimulates the skin and mucous membrane. It can react with the protein in the body tissue, so it has corrosive effect. It can make the cornea proliferate and peel off. Its toxicity is weaker than that of phenol, but taking it in large quantities can cause vomiting, diarrhea, headache, sweating, rash, shortness of breath, acidosis and excitement.  

Its aqueous solution is acidic. It has antipyretic and analgesic effects. Used as food preservative, dye disinfectant, medicine, etc. The oral LD50 of mice was 0.48 ~ 1.65 g / kg, and the minimum lethal dose was 60 mg / kg; The oral LD50 of rats was 1.5 ~ 2.0g/kg; It has moderate irritation and low toxicity through skin and mouth. The adult lethal dose is estimated to be about 5 ~ 15g, and some people think it is 20 ~ 30g. Mild poisoning can occur when the blood concentration is 55 ~ 85mg%, moderate poisoning can occur when the blood concentration is 80 ~ 110mg%, severe poisoning can occur when the blood concentration is 125 ~ 145mg%, and poisoning death can occur when the blood concentration is 160 ~ 180mg%.

Function and application of salicylic acid

1. Standards for alkalimetry and iodometry titration. Fluorescent indicator, complex indicator.

2. This product is used as anti scorch agent in the rubber industry and in the production of ultraviolet absorber and foaming agent.

3. Used as coordination indicator and coordination masking agent. Color developer and preservative for titanium, zirconium and tungsten plasma.

4. Salicylic acid is used as an additive in some weak acid electrolytes and as a complexing agent for electroplating or electroless plating.

5. Cosmetic preservatives. It is mainly used in water cosmetics such as toilet water, prickly heat water and quinine head water. In addition to antisepsis and sterilization, it also has the functions of dispelling sweat and odor, relieving itching and swelling, relieving pain and inflammation.

6. It is mainly used as the raw material of pharmaceutical industry to prepare aspirin, sodium salicylate, salicylamide, Zhitongling, phenyl salicylate, xuefang-67 and other drugs. The dye industry is used to prepare mordant pure yellow, direct brown 3gn, acid chrome yellow, etc. It is also used as rubber vulcanization retarder and disinfection preservative.

7. It can be used as accelerator for curing epoxy resin and preservative. It can be used to prepare synthetic spices such as methyl salicylate and ethyl salicylate. The dye industry is used as raw materials for the preparation of direct dyes and acid dyes. It can also be used as anti scorching agent and disinfectant for rubber.

8. small amount of used daily flavors such as animal essence and essence. Trace is used in food as a preservative. It is an important raw material for the pharmaceutical industry.

9. Salicylic acid phenol patch, commonly known as cornpaste.