Soda ash is the common name for sodium carbonate. It is also referred to as washing soda. On the pH scale, it is further on the base side than sodium bicarbonate. Soda ashes main purpose is to increase pH levels. Because swimming pools must be maintained at the proper pH level, soda ash is used for this purpose.
Calcium carbonate is added to municipal swimming pools. It neutralizes chlorine's acid affect by adjusting the pH.
In general, the amount of sodium carbonate to use in pool water is 16 oz. of sodium carbonate for every 10,000 gallons of water. The powder must be dissolved in water. It can then be added to the pool by a chemical feeder. It can also be dissolved in a bucket and poured into the pool. Only add the chemical to the pool when no one will swim for a day.
If pool water is not kept within a pH level of 7.2 to 7.6, the imbalance can create problems in the pool. Low pH when the water is acidic can cause cloudy water, staining, red eyes, hair loss, equipment destruction and the surfaces of the pool to deteriorate. When the pH is high or more basic other problems can occur such as a reduced effectiveness of chlorine, scales form and the filtration system can get plugged.
Sodium carbonate has only a slight toxicity, according to The Safety Data Sheet from Tradeasia International Pte Limited. High doses can cause health conditions, however, the Safety Data Sheet does not indicate what is a high dose. When inhaled, it can cause respiratory irritation, coughing and breathing difficulties as well as potential nasal septum damage. Large doses can cause gastro-intestinal problems, such as severe abdominal pain, diarrhea, vomiting, collapse and potential death. Eye contact can cause conjuctival edema and corneal destruction.
Sodium carbonate does have other important uses. It softens water for laundry. It is used to to adjust the pH in photographic developing agents. It is used in the brick making industry in the process of extruding clay. One of the other important uses is making glass. Through a chemical process and heat, it is used to create a non-crystalline transparent product, specifically glass.