Arsemate is soluble in pyridine and chloroform, but insoluble in water and other organic solvents. For arsenic detection, a 0.5% Arsemate/pyridine solution is used. The sample should be treated with sulfuric acid, 15% potassium iodide, and 40% SnCl2/HCl solution to convert arsenic to AsH3. Arsemate reacts with AsH3 in pyridine and forms red colloidal silver with a maximum wavelength at 520-540 nm. The detection range of arsenic using the Arsemate/pyridine solution is 4-12 ppm. Alternatively, 0.5% Arsemate/chloroform solution with 30 mM triethylamine can be used for the assay. For the colorimetric detection of arsenic, the AsH3 gas generator is required.