Arsenous acid is a toxic substance that can cause serious health problems if ingested. Antonyms, or words that have the opposite meaning of arsenous acid, would be safe, non-toxic substances that are beneficial to human health. Some examples of such substances include vitamins, minerals, and essential oils. Vitamins like vitamins C and D are essential for the proper functioning of the body and can be found in fruits, vegetables, and supplements. Minerals like calcium, potassium, and iron are important for maintaining bone health, supporting the immune system, and enhancing stamina. Essential oils like lavender, frankincense, and peppermint have been used for centuries to relieve pain, reduce stress, and promote relaxation.