Alkali is a substance that comprises hydroxide ions. In other words, it makes hydroxide ions in water. A hydroxide ion (OH–) comprises an oxygen and hydrogen atom that are covalently bonded to each other. An alkali neutralizes acid and dissolves in water. If a substance doesn’t dissolve in water, but neutralizes an acid, it is referred to as ‘base’. This means all alkalis are bases but not all bases are alkalis.
Alkalis react with acids to generate salt; this reaction process is called neutralization. Acids taste sour whereas alkalis are bitter to taste. On a pH scale, alkalis have a pH value of more than 7. Sodium hydroxide (caustic soda), sodium carbonate (washing soda or soda ash), potassium hydroxide (caustic potash), etc. are alkalis.
Alkalis help make soap, ceramics, and paper. Calcium hydroxide (slaked lime), a form of alkali, is used to make lakes or soils less acidic. Medicines that counter indigestion issues (excess hydrochloric acid in the stomach) comprise calcium carbonate. The base helps neutralize the acid. Ammonia solution is an alkali that helps neutralize the acidic bee sting.
A variety of consumer goods produced are dependent on alkalis at some level of manufacturing and capacity. Caustic soda and soda ash help make soap, glass, paper, detergents and cleansers, water softeners, textiles, gasoline and other derivatives of petroleum, etc.
Alkalis can be manufactured as soda ash, caustic soda, and also potash, lye, and caustic potash. In some places, natural alkali or significant soda ash (mineral form) deposits can be found. The soda ash is usually found as trona (sodium sesquicarbonate). This natural form of alkali is primarily found in Wyoming’s underground mines and California’s dry lake beds.
Back in the day, alkalis that were used for soap manufacturing were acquired from plant ashes. Potassium hydroxide solutions were made after putting rainwater through hardwood ashes. Modern day scientists make potassium hydroxide by brining electricity and salt water together. Similarly, potassium carbonate (potash) was filtrated by subjecting wood ashes to hot water.
Strength & Safety
Alkalis can be strong or weak. A strong alkali basically has a high pH value, usually pH 14. A weak alkali has a marginally lower pH value, usually pH 11 or 12. Stronger alkalis could induce burns, and if swallowed, they may lead to internal injuries or even death. Sodium bicarbonate is a mild alkali. Sodium carbonate and potassium hydroxide are examples of strong alkalis.
Despite being in common use, alkalis are hazardous and safety precautions should be in place when using them. Generally, alkalis with a pH of 10 or higher are more corrosive and caustic, capable of even corroding or destroying tissues. When handling strong alkalis, goggles and gloves must be worn. Spills must be neutralized with an acid such as vinegar before cleaning the spot. In case a strong alkali splashes onto one’s eyes or skin, the affected area must be exposed to cool water for quite a few minutes.