H acid 80% means the lot contains about 80% of the active compound, 4-amino-5-hydroxynaphthalene-2,7-disulphonic acid, by the supplier's assay method. The remainder is moisture, inorganic salt and organic impurities. The grade is a floor on content, not a promise about everything else in the lot.
H acid is a key intermediate for many azo dyes, including blacks, reds and reactive dyes. The H acid price moves often, and the assay percentage is only one of several reasons.
How to read the 80% figure
Ask four questions about the number before you accept it:
- How is it measured? Assay is usually done by diazotisation titration or by HPLC, and the two methods can give different results on the same lot. See how purity of intermediates is tested.
- On what basis? State whether the percentage is on the dry or the as-supplied material.
- What is the rest? Moisture, salts and isomers behave differently in your dye synthesis.
- Is it a minimum or a typical value? Write it as a minimum, with a range on moisture.
Other spec points to include
Besides assay, specify moisture, appearance and form (powder, wet cake or granules), insoluble matter, pH and the limits on the impurities that matter to your process. Isomeric and related naphthalene sulphonic acids can alter shade or reduce yield in the dye you make. Our guide on impurities in dye intermediates explains which ones to ask about.
For the written specification, see how to write a specification for H acid. To see where the compound is used, read H acid uses.
What moves the price
This article gives no price. These are the factors that change what a supplier will quote:
- Naphthalene-based raw materials and the sulphonating and processing chemicals used to make H acid.
- Assay and impurity levels: a tighter specification needs more purification and lowers the supplier's yield.
- Environmental compliance in Gujarat, since H acid production creates effluent that must be treated. See why intermediate prices change.
- Demand from dye makers, and the supply of capacity at the time you order.
- Pack, freight and Incoterm.
How to get a reliable quote
Send the same specification to each supplier, with the assay method and basis written in. Ask for a sample from current production and test it in your own process before you commit. Ask how long the quote stays valid and what happens to it if raw materials move.
Check the supplier makes the product itself rather than reselling. Our guide on finding genuine chemical manufacturers in Gujarat helps with that.
Packing, storage and safety
H acid is normally supplied as a powder or a wet cake in lined bags or drums. Moisture can change during storage, which shifts the assay on an as-supplied basis, so ask for the pack, the storage conditions and the shelf life. See shelf life of intermediates.
Check the safety data sheet for hazard and transport classification, and read how intermediates are packed and shipped. The classification decides whether you need special freight arrangements.
Next step
We find and audit intermediate plants, check samples and documents, and have lots tested. We do not publish price lists; a real quote comes from a sourcing review. To start, book a free sourcing review.