caustic soda vs soda water

caustic soda

noun
  • sodium hydroxide (NaOH), a strong alkaline substance used in the manufacture of paint, soap and detergents, or as a drain cleaner. 

soda water

noun
  • Carbonated water, water that has carbon dioxide dissolved in it and has been stored under pressure in a bottle. Usually mixed before drinking with another beverage. 

How often have the words caustic soda and soda water occurred in a corpus of books? (source: Google Ngram Viewer )