Potassium Amyl Xanthate (PAX, CAS 2720-73-2): Properties, Uses and Selection

Potassium amyl xanthate (PAX) is the longest-chain of the common xanthate collectors, and the strongest. Where recovery matters more than selectivity, PAX is often the collector of choice for sulphide ores. This article covers what PAX is, how it compares with SIBX and SIPX, when to use it, and how to specify and buy it.

1. What PAX is

Parameter	Typical value
Name	Potassium amyl xanthate (potassium pentyl xanthate)
CAS number	2720-73-2
Formula / MW	C₆H₁₁KOS₂ / about 202.4 g/mol
Appearance	Pale-yellow solid / powder
Assay	Typically 90% min (per grade)
Solubility	Soluble in water; usually dosed as a solution

2. What it does in the circuit

Xanthates are sulphide collectors: they make the target mineral surface hydrophobic so it attaches to air bubbles and floats. The length of the alkyl chain sets the balance between collecting power and selectivity.

Longer chain = stronger collecting power, lower selectivity.
Shorter chain = more selective, weaker collecting power.

PAX sits at the strong end. It is used where the priority is recovering as much of the target sulphide as possible, and where the circuit can tolerate the lower selectivity.

3. PAX vs SIBX vs SIPX

Collector	Chain	Strength / selectivity	Typical use
SEX (sodium ethyl xanthate)	Shortest (C2)	Most selective, weakest	Selective flotation of easily floated sulphides
SIPX (sodium isopropyl xanthate)	Short (C3)	Selective	Copper and lead-zinc circuits where a cleaner concentrate matters
SIBX (sodium isobutyl xanthate)	Medium (C4)	Strong, reasonably selective	Copper, lead, zinc and gold sulphides
PAX (potassium amyl xanthate)	Longest (C5)	Strongest, least selective	Maximising recovery of sulphides; bulk or rougher flotation

The right xanthate is settled by flotation tests on the actual ore – chain length is a starting point, not a specification.

4. Typical dosage and practice

Item	Typical practice
Dosage	About 10 – 100 g per tonne of ore, set by ore and stage
Addition point	Conditioning or grinding, with controlled pH and residence time
Form	Made up as a solution on site

5. Handling and storage

Stability. Xanthates are moisture- and heat-sensitive and decompose with time; buy to your consumption rate and use within the shelf life.
Storage. Keep cool, dry and sealed, away from acids and oxidisers.
Safety. Xanthates decompose to release carbon disulphide and other species; use ventilation and PPE and follow the SDS.

6. Grades and supply

Item	Detail
Grade	Typically 90% min; confirm the assay and form you need
Packaging	Drums / bags / bulk, per supplier specification
Documents	Per-batch COA and SDS; third-party inspection on request
Delivery	FOB or CIF to African mining ports (Durban, Mombasa, Dar es Salaam, Tema/Takoradi, Lagos/Apapa and others)

Because xanthates degrade, plan the supply so the material is used well within its shelf life – tell us your monthly consumption and discharge port and we will quote accordingly.

Frequently Asked Questions

What is PAX used for?

As a strong sulphide collector for copper, lead, zinc, nickel and gold ores, where maximising recovery is the priority.

How does PAX compare with SIBX?

PAX has the longer chain, so it is a stronger but less selective collector; SIBX (C4) is strong and more selective. The right choice is set by flotation tests on the ore.

How is PAX dosed?

Typically about 10-100 g/t, added at conditioning or grinding, usually as a solution made up on site.

How should PAX be stored?

Cool, dry and sealed, away from acids and oxidisers. Xanthates decompose with moisture, heat and time, so rotate stock.