Concentration of concentrated hydrochloric acid

Hydrochloric acid, also known as hydrogen chloride, is a strong acid with the chemical formula HCl. Along with it is sulfuric acid, which we have already come into contact with in junior high school. It ran through all of our chemistry courses in middle school. Because hydrochloric acid is highly corrosive, it can react with many things and therefore has many uses. Including the preparation of chemical drugs and their application in production and life. When we treat back pain, we usually use hydrochloric acid solution. In different applications, we need different concentrations of hydrochloric acid. So what is the concentration of concentrated hydrochloric acid?

Hydrochloric acid with a mass fraction exceeding 20% ​​is called concentrated hydrochloric acid. The concentration of commercially available concentrated hydrochloric acid is 36%~38%, and the concentrated hydrochloric acid used in experiments is generally 36%~38%. The substance concentration is 12mol/L. Density 1.179g/cm3, it is an azeotropic mixture. Concentrated hydrochloric acid is highly volatile in the air and is highly corrosive to skin and clothing. Concentrated hydrochloric acid reacts to produce chlorine gas, chlorides and water.

2KMnO4+16HCl (concentrated)=2KCl+2MnCl2+5Cl2↑+8H2O

4HCl(concentrated)+MnO2=heating=MnCl2+2H2O+Cl2↑

14HCl(concentrated)+K2Cr2O7==3Cl2(gas)+2CrCl3+2KCl+7H2O

1. Production and storage

The main method for producing hydrochloric acid is to electrolyze sodium chloride solution using the diaphragm method. The chlorine gas precipitated from the anode and the hydrogen gas precipitated from the cathode are mixed together, and the hydrogen gas is burned in the chlorine gas. The generated hydrogen chloride dissolves in water to obtain hydrochloric acid.

The use of hydrochloric acid is second only to sulfuric acid. It is an important chemical raw material and chemical reagent used in medicine, food, electroplating, welding, enamel, and other industries.

Due to the strong volatility of hydrochloric acid, the volatilized hydrogen chloride will combine with water vapor in the air to form small droplets of hydrochloric acid that diffuse in the air. Therefore, hydrochloric acid must be stored in a sealed container, otherwise the quality of the hydrochloric acid will gradually decrease over time, and its concentration will also decrease. Store in a cool, dry and ventilated place. It should be stored separately from flammable and combustible materials, alkalis, metal powders, etc. Do not mix storage or transportation. Be careful when handling to prevent damage to the packaging and containers. Pay attention to personal protection during packaging and handling operations. Transport follows the prescribed route.

2. Chemical Uses

Hydrochloric acid is an important basic chemical raw material and is widely used. It is mainly used to produce various chlorides; various rare metals are extracted in hydrometallurgy; it is a commonly used acid in organic synthesis, textile bleaching and dyeing, petroleum processing, leather and paper making, electroplating welding, and metal pickling; in life, it can remove rust and scale; in the production of organic drugs, it is indispensable for the preparation of procaine, thiamine hydrochloride, glucose, etc.; it is also useful in the preparation of animal glue and various dyes; in the food industry, it is used to make monosodium glutamate and chemical soy sauce; doctors also directly let patients with insufficient gastric acid take extremely dilute hydrochloric acid to treat indigestion; it is one of the most commonly used chemical reagents in scientific research and chemical experiments.

3. Check:

For free chlorine or bromine, take 20 ml of the product and add 0.2 ml of zinc-potassium iodide starch indicator solution. No blue color should appear within 10 minutes.

Sulfate

Take 3 ml of the product, dilute it with 5 ml of water, then add 5 drops of 25% barium chloride solution. No turbidity or precipitation should occur within 1 hour.

Sulfites

Take 50ml of freshly boiled cold water, add 1.0g of potassium iodide, 0.15ml of iodine titration solution (0.01mol/L) and 1.5ml of starch indicator solution, and shake well; take another 15ml of the product, dilute it with 40ml of freshly boiled cold water, add it to the above solution, shake well, and the blue color of the solution must not disappear completely.

Ignition residue

Take 20 ml of the product, add 2 drops of sulfuric acid, evaporate to dryness, and inspect according to the law (Appendix VIII N). The remaining residue shall not exceed 2 mg (0.01%).

Iron salt

Take 20 ml of the product and evaporate it to dryness on a water bath. Add 25 ml of water to the residue and inspect it according to the law (Appendix VIII G). When compared with the control solution made from 1.0 ml of standard iron solution, it shall not be darker (0.000 05%).

Heavy Metals Take 10 ml of the product, evaporate it on a water bath, add 2 ml of acetate buffer (pH 3.5) and an appropriate amount of water to make 25 ml. Check according to the law (Appendix VIII H Method 1). The heavy metal content shall not exceed 2 parts per million.

Arsenic salts

Take 1.4 ml of the product, dilute it with 22 ml of water, add 5 ml of hydrochloric acid, and check it according to the law (Appendix J Method 1). It should meet the requirements (0.000 14%).