Technical Guide

Benzisothiazolinone (CAS 2634-33-5): Complete Technical Data Reference

This reference page consolidates the core chemical identity data for Benzisothiazolinone (BIT) — CAS number, molecular formula and weight, structural identifiers, and the chemical synonyms used across international specifications, safety data sheets, and regulatory filings.

Published 2026-01-15Updated 2026-07-27By Vasudev Chemo Pharma Technical TeamReviewed by Vasudev Chemo Pharma Formulation & Regulatory Affairs Team, Industrial Chemistry, Biocide Formulation

What Is the Core Chemical Identity of Benzisothiazolinone?

Benzisothiazolinone (BIT) is registered under CAS Number 2634-33-5, with molecular formula C7H5NOS, molecular weight 151.18 g/mol, EC/EINECS number 220-120-9, and UN Number 3077 for transport. Its IUPAC name is 1,2-benzothiazol-3-one.

In its neat (100% active) form, BIT is a white to pale yellow crystalline solid with a melting point of approximately 154-158°C. BIT 20% refers to this same active substance supplied as a 20% active solution in a water/glycol carrier — the dilution most commonly used for handling, dosing accuracy, and formulation compatibility. The InChIKey is DMSMPAJRVJJAGA-UHFFFAOYSA-N and the SMILES notation is C1=CC=C2C(=C1)C(=O)NS2.
Benzisothiazolinone (BIT) core identity data
PropertyValue
CAS Number2634-33-5
Molecular formulaC7H5NOS
Molecular weight151.18 g/mol
EC / EINECS Number220-120-9
UN Number (transport)3077
IUPAC name1,2-benzothiazol-3-one
InChIKeyDMSMPAJRVJJAGA-UHFFFAOYSA-N
Melting point (neat)Approximately 154-158°C

What Are the Chemical Synonyms of Benzisothiazolinone?

Benzisothiazolinone is referenced under many synonymous names across regions and documentation standards, all describing the identical substance registered under CAS 2634-33-5, including 1,2-Benzisothiazolin-3-one, Benzisothiazolone, and 1,2-Benzoisothiazol-3-one, among several other established names.

Common synonyms include: 1,2-Benzisothiazol-3(2H)-one; 1,2-Benzisothiazolin-3-one; Benzisothiazolinone; Benzisothiazolone; 1,2-Benzoisothiazol-3-one; Benz[d]isothiazol-3(2H)-one; 2,3-Dihydro-1,2-benzisothiazol-3-one; 1,2-Benzothiazol-3-one; and 3-Hydroxy-1,2-benzisothiazole. Common abbreviations include BIT, BIT 20, and BIT-20. The substance is also sold under trade names including Preventol BIT 20 N (LANXESS), Nipacide BIT 20 (Clariant), Acticide BIT, Mergal BIT20, and the Proxel family of grades from Lonza.

What Are the Typical Physical Properties of BIT 20% Solution?

Reported values for BIT 20% commercial solutions include density approximately 1.05-1.14 g/cm3, pH (as 10% dilution) approximately 11-13, and viscosity approximately 200-270 mPas at 20°C — values vary by supplier formulation, so always check the batch-specific COA.

Because these figures vary between different commercial BIT 20% formulations (different carriers, stabilisers, and manufacturing processes produce slightly different physical properties even at the same nominal active content), always refer to the specific Certificate of Analysis and Technical Data Sheet for the exact batch and supplier you are purchasing from.
BIT 20% commercial solution — typical physical property ranges
PropertyTypical valueNotes
AppearanceClear to light-yellow liquidColour varies by supplier carrier system
Density (20°C)1.05-1.14 g/cm3Confirm against batch COA
pH (10% dilution in water)11-13Formulation-dependent
Viscosity (20°C)200-270 mPasFormulation-dependent
Active content20% ± 0.5% (as supplied by Vasudev Chemo Pharma)Verify against Certificate of Analysis

Frequently asked questions

What is the CAS number of Benzisothiazolinone (BIT)?+
The CAS number of Benzisothiazolinone is 2634-33-5. This identifier is used across international chemical databases, safety data sheets, and regulatory filings regardless of trade name or synonym.
What is the molecular formula and molecular weight of BIT?+
The molecular formula of Benzisothiazolinone is C7H5NOS, with a molecular weight of 151.18 g/mol.
What is the IUPAC name of Benzisothiazolinone?+
The IUPAC name is 1,2-benzothiazol-3-one, also commonly written as 1,2-benzisothiazol-3(2H)-one in technical literature and specification documents.
Are BIT, 1,2-Benzisothiazolin-3-one, and Benzisothiazolone the same substance?+
Yes. BIT, 1,2-Benzisothiazolin-3-one, 1,2-Benzisothiazol-3(2H)-one, Benzisothiazolone, and several other names on this page all refer to the identical chemical substance under CAS 2634-33-5.

Sources

  1. European Chemicals Agency — Substance information, 1,2-benzisothiazol-3(2H)-one
  2. PubChem — 1,2-Benzisothiazol-3(2H)-one compound summary (CID 17520)