The Sulfurous acid, with the CAS registry number 7782-99-2 and EINECS registry number 231-973-1, is also called Dihydrogen sulfite. It is a kind of air sensitive chemical, and belongs to the product category of Inorganics. And the molecular formula of the chemical is H₂O₃S. There is no evidence that sulfurous acid exists in solution, but the molecule has been detected in the gas phase. The conjugate bases of this elusive acid are, however, common anions, bisulfite (or hydrogensulfite) and sulfite. The conjugate bases of this elusive acid are, however, common anions, bisulfite (or hydrogensulfite) and sulfite.

The characteristics of Sulfurous acid are as followings: (1)ACD/LogP: -1.59; (2)# of Rule of 5 Violations: 0; (3)ACD/LogD (pH 5.5): -6.06; (4)ACD/LogD (pH 7.4): -6.09; (5)ACD/BCF (pH 5.5): 1; (6)ACD/BCF (pH 7.4): 1 ; (7)#H bond acceptors: 3; (8)#H bond donors: 2; (9)#Freely Rotating Bonds: 0; (10)Polar Surface Area: 54.74 Å²; (11)Index of Refraction: 1.788; (12)Molar Refractivity: 13.98 cm³; (13)Molar Volume: 33 cm³; (14)olarizability: 5.54×10^-24cm³; (15)Surface Tension: 291.3 dyne/cm; (16)Density: 2.483 g/cm³.

You should be cautious while dealing with this chemical. It is harmful by inhalation, and may cause burns. Therefore, you had better take the following instructions: Wear suitable protective clothing, gloves and eye/face protection, and if in case of contacting with eyes, rinse immediately with plenty of water and seek medical advice, or if in case of accident or if you feel unwell, seek medical advice immediately (show label where possible). 

Addtionally, the following datas could be converted into the molecular structure:
(1)SMILES: O=S(O)O
(2)InChI: InChI=1/H2O3S/c1-4(2)3/h(H2,1,2,3)
(3)InChIKey: LSNNMFCWUKXFEE-UHFFFAOYAJ

The toxicity data is as follows: