In our daily work in the laboratory , we often need to use some acids and bases to help complete the experiment, but in the process, from time to time because of some improper operation or not familiar with the properties of acids and bases, and cause damage to us. In order to better complete the work, reduce the use of acid and alkali to bring us harm, now introduce the characteristics of common laboratory acid and alkali, is willing to bring positive help.
Laboratory commonly used acids are: sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, acetic acid. Common bases are sodium hydroxide, potassium hydroxide, and ammonia. The properties of these acids and bases are not the same, and the key points to be paid attention to and the risks to be prevented are not the same. Now they are briefly introduced.
Sulfuric acid
Concentrated sulfuric acid is colorless, odorless, oil-like liquid, density 1.84g/cm³, high boiling point, difficult to volatilization. It has strong dehydrating, absorbent, oxidizing and acidic properties, which can make biological tissues dehydrate and carbonize according to the proportion of water molecules and cause serious damage to skin and other tissues. In the dilution remember “along the wall, slowly add, constantly shaking or stirring”, to prevent local overheating caused by boiling, sputtering, at the same time, must be the sulfuric acid added to the water, rather than water to add sulfuric acid, the order can not be reversed. When concentrated sulfuric acid is added to the reactant, the reactant should be cold; concentrated sulfuric acid should not be added to the hot reactant. If skin contact, a small amount of direct water rinse, a large amount of first wipe and then rinse with water.
Hydrochloric acid
Concentrated hydrochloric acid is colorless transparent liquid, has a strong pungent smell, high corrosion, acid connectivity, reduction, complexation. It is easy to volatilize HCl gas with irritating smell. When the temperature is high, rinse it under the water flow before use, reduce the pressure in the bottle, reduce the volatile hydrogen chloride gas, do a good job of protection, and use it under the fume hood. Do not face the mouth of the bottle to prevent gas from rushing out and causing injury. In case of contact, rinse immediately with plenty of water. In serious cases, seek medical advice.
Nitric acid
Pure nitric acid is colorless transparent liquid, concentrated nitric acid is light yellow liquid (dissolved with nitrogen dioxide), under normal circumstances is colorless transparent liquid, with asphyxiating smell. Volatile, producing white fog in the air. When exposed to light and heat, toxic nitrogen dioxide is produced. It is highly acidic, corrosive and oxidizing. When the temperature is high, it is necessary to cool the bottle before use. Concentrated nitric acid can not be directly added to the hot reaction medium, and a large amount of water can be washed immediately if it is accidentally touched.
Trichloroacetic acid
Trichloroacetic acid at room temperature is colorless crystal with pungent smell. Easily deliquescent, soluble in water, ethanol and ether. Low toxicity, nonflammable, corrosive gas produced by high temperature decomposition, class 2B carcinogenic. Its dust has irritating effect on respiratory tract, so attention should be paid to protection during use. Cover the reagent bottle immediately after use.
Trifluoroacetic acid
Colorless volatile fuming liquid, volatile, strong irritant and slightly toxic. It can be miscible with water, fluoroalkanes, methanol, benzene, ether, carbon tetrachloride and hexane, and can partially dissolve alkanes with more than six carbon and carbon disulfide. The acidity is affected by trifluoromethyl, which is 100000 times stronger than acetic acid. Nonflammable, highly corrosive, decomposes to produce corrosive gas. Since it is volatile, the solution shall be sealed after being prepared to prevent the concentration from being reduced due to volatilization. Wash with plenty of water in case of accidental contact. If inhaled, move to a place with fresh air immediately.
Phosphoric acid
Transparent colorless viscous solution, odorless. It belongs to medium strong acid, corrosive, acidic and easy to deliquescence. The concentrated solution is irritating to glasses and skin and can corrode skin. Wash with plenty of water immediately in case of accidental contact.
Acetic acid
At room temperature, it is colorless liquid with pungent smell, and at low temperature, it is icy solid, also known as glacial acetic acid. Acidic, concentrated solutions are corrosive and will attack the skin. The steam can irritate the airways, face, and lungs.
Sodium hydroxide
At room temperature for white flake or granular solid, with strong alkaline, strong corrosive, strong water absorption, also known as caustic soda, caustic soda, solid alkali, caustic soda, caustic soda. The air will soon deliquescent, dissolved in water heat, dissolved water needs to be constantly stirred. Dust will irritate respiratory tract, skin contact will burn, careless contact should immediately wash a lot of water. Potassium hydroxide is similar to its chemical properties. It is a white granular or flake solid at room temperature, soluble in water and ethanol, soluble in water and releasing a lot of heat, slightly soluble in ether, soluble in alcohol and glycerin, with moderate toxicity.
Ammonia
It is a colorless liquid with a strong pungent smell and a lower density than water. The higher the concentration of ammonia, the lower the density. The pH value of 1mol/L ammonia is 11.63. It has weak alkaline, corrosive and tear – inducing properties. Exothermic reaction with acid. Before use, water cooling must be carried out in the fume hood to cool the bottle. The mouth of the bottle is forbidden to people. When the concentrated ammonia water container is heated, the pressure in the container will increase and there is the danger of explosion. In case of contact, rinse immediately with plenty of water and seek medical advice immediately.
Conclusion
Transparent colorless viscous solution, odorless. It belongs to medium strong acid, corrosive, acidic and easy to deliquescence. The concentrated solution is irritating to glasses and skin and can corrode skin. Wash with plenty of water immediately in case of accidental contact.
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