Hydrochloric acid is an aqueous solution of hydrogen chloride (HCl) and has a wide range of industrial uses. Hydrochloric acid is a colorless and transparent liquid with a strong pungent smell and high corrosiveness. Concentrated hydrochloric acid (mass fraction of about 37%) is extremely volatile, so when the container containing concentrated hydrochloric acid is opened, the hydrogen chloride gas will evaporate and combine with water vapor in the air to produce small droplets of hydrochloric acid, causing acid to appear above the bottle mouth. fog. Hydrochloric acid is the main component of gastric acid, which can promote food digestion and resist microbial infections.
1. Biological uses
Humans and other animals have special glands on the stomach wall that convert the salt they eat into hydrochloric acid. Hydrochloric acid is a component of gastric juice (concentration is about 0.5%). It can keep the gastric juice at the most suitable pH value required to activate pepsin. It can also denature the protein in food and make it easy to hydrolyze, and kill the food accompanying it. The effects of bacteria entering the stomach. In addition, after hydrochloric acid enters the small intestine, it can promote the secretion of pancreatic juice, intestinal juice, and the secretion and discharge of bile. The acidic environment also helps the absorption of iron and calcium in the small intestine.
2. Daily use
Utilize the property of hydrochloric acid to react with insoluble alkali to prepare daily necessities such as toilet cleaner and rust remover.
3. Industrial use
Hydrochloric acid is a strong inorganic acid solution that has a wide range of applications in industrial processes, such as the refining of metals. Hydrochloric acid often determines the quality of the product.
4. Analytical Chemistry
In analytical chemistry, when an acid is used to determine the concentration of a base, hydrochloric acid is generally used for titration. Titration with a strong acid solution can make the end point more distinct, resulting in more accurate results. At 1 standard atmosphere, 20.2% hydrochloric acid can form a constant boiling solution, which is often used as a benchmark in quantitative analysis under a certain pressure. Its constant boiling concentration changes with changes in air pressure.
Hydrochloric acid is often used to dissolve solid samples for further analysis, including dissolving some metals and calcium carbonate or copper oxide to form easily soluble substances to facilitate analysis.
5. Pickling steel
One of the most important uses of hydrochloric acid is in pickling steel. Before subsequent processing of iron or steel (extrusion, rolling, galvanizing, etc.), hydrochloric acid can be used to react away rust or iron oxides on the surface. Hydrochloric acid solution with a concentration of 18% is usually used as a pickling agent to clean carbon steel.
6. Hydrochloric acid also has many small-scale uses, such as leather processing, salt production, and in the construction industry.
7. Hydrochloric acid is also commonly used in the petroleum industry: hydrochloric acid is injected into oil wells to dissolve rocks and form a huge cavity.
8. Hydrochloric acid can dissolve calcium carbonate. Its applications include scale removal or lime mortar used in bricklaying. However, hydrochloric acid is more dangerous and needs to be used with caution. It reacts with calcium carbonate in lime mortar to produce calcium chloride, carbon dioxide and water
9. Hydrochloric acid is commonly used in the production of gelatin, food, food raw materials and food additives.
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