Sodium Ethyl Xanthate (SEX, CAS 140-90-9): Properties, Uses and Selection

Sodium ethyl xanthate (SEX) is the shortest-chain of the common xanthate collectors – the most selective, and the weakest. It is used where a clean, well-differentiated concentrate matters more than raw recovery, and where the ore’s sulphides float easily. This article covers what SEX is, how it compares with SIPX, SIBX and PAX, when to use it, and how to specify and buy it.

1. What SEX is

Parameter	Typical value
Name	Sodium ethyl xanthate
CAS number	140-90-9
Formula / MW	C₃H₅NaOS₂ / about 144.2 g/mol
Appearance	Pale-yellow solid / powder
Assay	Typically 90% min (per grade)
Solubility	Soluble in water

2. What it does in the circuit

As a sulphide collector, SEX makes target mineral surfaces hydrophobic so they attach to bubbles and float. Its short ethyl chain gives it the highest selectivity and the lowest collecting power of the common xanthates – which is exactly what you want when the goal is to float one sulphide while leaving others behind.

3. SEX vs SIPX vs SIBX vs PAX

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; cleaner concentrates
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; bulk or rougher flotation

SEX is often used on the selective side of a circuit, or on ores whose sulphides float readily. The definitive choice is made by flotation testing on the actual ore.

4. Typical dosage and practice

Item	Typical practice
Dosage	About 10 – 80 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. 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 assay and form
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 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 SEX used for?

As a selective sulphide collector, especially where easily floated sulphides must be separated cleanly, or on the selective side of a circuit.

How does SEX compare with SIPX?

SEX has the shorter chain, so it is more selective but weaker; SIPX is a step stronger while still selective. Choose by flotation test on the ore.

How is SEX dosed?

Typically about 10-80 g/t, added at conditioning or grinding, usually as a solution made up on site.

How should SEX be stored?

Cool, dry and sealed, away from acids and oxidisers; rotate stock, because xanthates decompose with moisture, heat and time.