Thiourea Dioxide and FAS Buyer & Technical FAQs
Find answers to common questions about Thiourea Dioxide (TDO), paper-grade Formamidine Sulfinic Acid (FAS), product quality, application trials, storage, transport and supplier evaluation.
Dasteck supplies TDO and paper-grade FAS as separate commercial product lines. Please select the product family that matches your application and request the relevant TDS, SDS, COA and technical guidance before trial or purchase.
At a glance: Dasteck manufactures Thiourea Dioxide (TDO, CAS 1758-73-2) and paper-grade FAS (same CAS No.), with commercial TDO production since 1983 at a designed capacity of 10,000 t/y across five automated lines, under ISO 9001:2015 certification (Certificate No. 05326Q00214R201).
Verified references: CAS Common Chemistry · PubChem CID 61274 · ECHA substance record · ISO 9001:2015.
Dasteck’s Thiourea Dioxide standard was adopted as China’s industry standard in 1989, and the company took part in the HG/T 3258 revisions issued in 2001 and 2010.
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Browse by Topic
Buyer and Commercial FAQ
Capacity, samples, quotations, minimum order quantity, Incoterms, delivery planning and supplier evaluation.
Quality and Compliance FAQ
ISO 9001, specifications, batch testing, COAs, traceability, retention samples, storage, packaging and transport documentation.
Textile TDO FAQ
Polyester reduction clearing, dye stripping, dyehouse cleaning, ORP control, dosage development, trial design and troubleshooting.
Pulp and Paper FAS FAQ
Deinked-pulp bleaching, mechanical-pulp applications, FAS dosing, brightness improvement, peroxide staging and paper-mill trials.
Core Guides: Start Here
Each topic below has one core guide that carries the full answer. Sub-questions link into the relevant section of a core guide instead of repeating the same answer on a separate page.
| Topic | Core guide | Sub-questions |
|---|---|---|
| Reducing-agent comparison | TDO vs Sodium Hydrosulfite (Dithionite) | Reduction strength · Stripping replacement · Odour |
| Polyester replacement | How to Replace Sodium Dithionite in Polyester Reduction Cleaning | Replacement ratio · Laboratory test · Start a trial |
| Why and when to switch | Sodium Hydrosulfite Alternatives for Textile Processing | Chemical consumption · Dose per tonne of fabric |
| FAS in paper and pulp | FAS vs Sodium Dithionite in Paper Applications | Dose per tonne of pulp & conversion · Cost · Safety |
| Cost calculation | Thiourea Dioxide Cost Calculation and Price per Ton Guide | Real cost advantage · Quotation basis |
Product Identity
What is Thiourea Dioxide?
Thiourea Dioxide is a sulphur-containing organic reducing compound supplied as a white crystalline powder or granular solid. Its CAS Registry Number is 1758-73-2.
What does TDO mean?
TDO is the common abbreviation for Thiourea Dioxide.
What are the molecular formula and molecular weight?
The molecular formula is CH4N2O2S, and the molecular weight is 108.12 g/mol.
Is Formamidine Sulfinic Acid the same as Thiourea Dioxide?
Formamidine Sulfinic Acid is a commonly used chemical name for Thiourea Dioxide and refers to the same CAS number, 1758-73-2.
For commercial and application-support purposes, Dasteck supplies TDO and paper-grade FAS as separate product lines. Product grades may differ in specification, particle-size control, packaging, documentation and recommended use. Request the grade intended for your specific process.
Which product should I request for my application?
For textile reduction clearing, dye stripping, dyehouse cleaning and selected industrial reduction applications, request TDO. For deinked-pulp bleaching, recycled-fibre processing and mechanical-pulp bleaching, request paper-grade FAS and the corresponding paper-industry technical documentation.
Selected FAQs
What Factors Affect the Accuracy of Thiourea Dioxide Purity Testing?
Standard solution stability, sample handling time, testing temperature, weighing conditions, sample dissolution and titration endpoint control.
How DASTECK Ensures Purity and Batch Consistency
Raw-material control, reaction conditions, crystallization, washing, equipment materials, drying and batch verification.
Why Is Moisture Control Critical for Thiourea Dioxide Stability and Safety?
UN3341 Class 4.2, moisture control, automated drying, storage stability and what buyers should verify.
How to evaluate a Thiourea Dioxide supplier
A buyer's checklist covering identity, capacity, specifications, batch consistency, documents, export capability and sample evaluation.
Can Thiourea Dioxide be transported as a liquid?
Practical considerations for solution preparation, stability and on-site use.
Can Thiourea Dioxide be blended with sodium dithionite (sodium hydrosulfite)?
Blending considerations, compatibility risks and trial requirements.
Why must reduction clearing be followed by rinsing and neutralisation?
How rinsing and neutralisation affect residual chemicals, shade and fastness.
How should the ORP of a reduction bath be controlled?
ORP measurement, control windows and process variables to record.
FAS Dosing Guidelines for Paper Mills
Solution preparation, metering, addition-point requirements and common operating mistakes.
Can FAS be used to bleach CTMP mechanical pulp?
Application considerations for mechanical-pulp brightness improvement.
How should the reductive bleaching stage for deinked pulp be designed?
Process staging, furnish variation and trial design for DIP bleaching.
What is the specification, CAS number and packing of Thiourea Dioxide?
Product identity, specification, packaging and document references.
How much brightness improvement can FAS achieve in pulp bleaching?
Brightness response depends on furnish, starting brightness, dosage and process conditions.
Does FAS cause brightness reversion?
Factors affecting brightness stability and how to evaluate reversion in mill trials.
Safety and storage questions
Storage, handling, transport documentation and current SDS references.
Technical Guides and Resources
Thiourea Dioxide for Textile Processing
Complete guide to reduction clearing, stripping, dyehouse cleaning and trial design.
FAS for Pulp and Paper
Guide to DIP bleaching, mechanical pulp, FAS dosing and brightness improvement.
Quality and Compliance FAQ
Specifications, COAs, ISO 9001, traceability, retention samples and EHS documentation.
Technical FAQ
ORP control, dosage, applications and troubleshooting references.
FAS and Hydrogen Peroxide
Two-stage bleaching considerations for pulp and paper applications.
FAS Temperature and Reaction Time
Process-window considerations for FAS bleaching and mill trials.
Need help selecting TDO or FAS? Tell us your material, process, current reducing agent and target result. Our technical team can recommend an appropriate product and trial approach.
Complete FAQ Index
How to read this index: start with the Core Guides above; entries below are the complete question list. Sub-questions that were merged into a core guide link to that guide's section.
All 69 standalone FAQ answer pages, grouped by buyer and official topics.
Buyer & Commercial FAQ
Official Technical & Application FAQ
More TDO Operational & Quality Guides
Cleaning in place with Thiourea Dioxide
Equipment cleaning, rinseability and process control for textile dyeing machinery.
TDO auxiliary compatibility
How to check compatibility with surfactants, alkali and other textile auxiliaries.
Thiourea Dioxide for fine fabrics
Risk controls for delicate polyester, blends and fine fabric processing.
Incoming inspection checklist
Recommended checks for identity, packaging, documentation and batch release.
Switchover safety checklist
Practical steps when evaluating a transition from another reducing agent.
How to prepare a trial report
Record dosage, temperature, alkali, substrate, shade and performance results.
Complaint handling and traceability
Batch records, retention samples, investigation and corrective-action workflow.
Wastewater COD considerations
Process context, treatment evaluation and responsible use of reducing agents.
Technical Articles & Industry Updates
Selected long-form technical articles and application updates for textile, pulp and paper, safe handling and reducing-agent comparison.
Why Choose Dasteck Thiourea Dioxide
Manufacturing history, capacity, quality control and supply considerations for buyers.
Thiourea Dioxide for Textile Processing
Reduction clearing, dye stripping, dyehouse cleaning and process evaluation.
Preventing Over-Reduction in Vat Dyeing
Process controls for avoiding excessive reduction, shade changes and fibre damage.
FAS in Deinked Pulp for Newsprint
Reductive bleaching considerations for DIP and recovered-fibre brightness.
Thiourea Dioxide in Kaolin Processing
Reductive bleaching, iron removal and application evaluation for kaolin clay.
Safe Handling and Storage
Moisture, temperature, storage, packaging and safe handling guidance.
FAS for Deinked Pulp Bleaching
Paper-grade FAS for DIP, mechanical pulp and recycled-fibre applications.
TDO Features and Benefits
Reduction performance, stability, odour, handling and industrial use cases.
TDO vs Sodium Hydrosulfite
Compare reduction strength, alkaline demand, odour, storage, dosage and cost.
Long-Form Technical Guides
These pages cover the same topics in more depth, with process detail, numbers and worked examples:
Browse by intent: cost, selection, replacement, acceptance
- Cost cluster | cost per tonne and buying terms
- Selection cluster | which reducing agent
- Replacement cluster | switching from sodium dithionite
- Acceptance cluster | incoming inspection, COA and documents
Already using sodium dithionite and want the numbers? Request TDS, COA, price or a trial sample.
Dasteck Chemicals
Yantai Dasteck Chemicals Co., Ltd.
Contact
Tel: +86-535-6530669
Fax: +86-535-6530939
Address: 59 Huagong Road, Zhifu District, Yantai City, Shandong Province, China 264002
Website: dasteck.com