Arsenious acid is a highly toxic compound that is used in the manufacturing of pesticides, insecticides, and other chemicals. It is also known as arsenic trioxide, arsenic acid, or arsenious anhydride. Some synonyms for arsenious acid include white arsenic, arsenic oxide, arsenic sesquioxide, and arsenic trioxide. These synonyms are often used interchangeably depending on the context in which they are used. While arsenious acid has been used in various industrial and agricultural applications, it is important to note that exposure to this substance can be extremely harmful and can lead to serious health complications.