2-3-8 Dissolve 5.00 g As203 (M, =197.84) and 6.00 g NaOH in 20 cm deoxygenated water, and add 1.44 g sulfur (Mr =32.06), then heat to 100 C in a reflux device for 2 h. After filtering the excess elemental sulfur from the solution, the solution is cooled down to below 4 C. After drying under vacuum, filter the obtained crystals and then dissolve them in deoxygenated water again. Add ethanol to recrystallize (the percentage loss of sulfur is 13.3%), filter and dry to obtain 13.66 g of crystals (only one substance). The chemical formula of the crystals is