Sodium isopropyl xanthate (SIPX) sits in the middle of the xanthate family, between the highly selective short-chain salts and the powerful long-chain collectors. That position is exactly why it is one of the most widely used collectors in base-metal concentrators: it gives enough collecting power to float chalcopyrite, galena and activated sphalerite, while staying selective enough to keep pyrite and gangue in the tailings. This guide covers what SIPX is, how it behaves in a circuit, how it compares with SBX, SEX and PAX, and what to check when buying it.
What Sodium Isopropyl Xanthate (SIPX) Is
SIPX belongs to the xanthate family of sulfide collectors — salts of isopropyl xanthic acid, supplied as a pale yellow to yellow powder or as a solution, with the general formula C3H7OCSSNa. It is manufactured by reacting isopropanol with carbon disulfide in the presence of sodium hydroxide, the same route used for other xanthates; the difference is the length and shape of the alkyl group, and that is what determines how the molecule behaves at a mineral surface.
The isopropyl group is short and branched. Short chains give the collector less hydrophobic “reach”, so it attaches less aggressively than amyl xanthates, but the branched structure still provides sufficient water-repellency for fast-floating sulfides. The practical result is a collector with moderate strength and good selectivity — the combination that most copper and lead-zinc circuits are looking for.
For the wider picture of how xanthates differ from one another, see our guide to xanthate collectors in froth flotation.
SIPX Specification and Typical Properties
Because SIPX is bought on assay, not on description, the specification matters more than the trade name. The parameters that decide performance in a plant are:
| Parameter | Typical SIPX | Why it matters |
|---|---|---|
| Active content (as sodium isopropyl xanthate) | ≥ 90% | Directly sets the effective dose; low assay means higher consumption per tonne |
| Free alkali (as NaOH) | ≤ 0.5% | Too much free alkali raises pulp pH and can depress sulfides |
| Moisture | ≤ 1% | Hygroscopic product; moisture accelerates decomposition |
| Water insolubles | ≤ 0.5% | Insolubles leave residue in the dosing system |
| Appearance | Pale yellow powder or solution | Darkening indicates decomposition |
Xanthates decompose over time, releasing carbon disulfide and losing collecting power, so freshness is a specification item. A certificate of analysis per lot, plus a sensible stock rotation, is the cheapest form of process control a concentrator can buy.
How SIPX Behaves in Copper and Copper-Molybdenum Circuits
In copper flotation, SIPX is typically the primary collector for chalcopyrite, often with a small addition of a stronger collector where coarse or partly oxidised particles are present. It is also a common choice in copper-molybdenum circuits, where the priority is to float copper sulfides cleanly without over-collecting pyrite, and in lead-zinc circuits where galena is floated ahead of sphalerite.
Two behaviours define day-to-day operation:
- Selectivity against pyrite. Because the isopropyl chain is short, SIPX is less inclined than amyl xanthates to float pyrite. In ores with a high pyrite-to-chalcopyrite ratio, that alone can raise concentrate grade without extra depressant.
- Response to activation. Activated sphalerite floats readily with SIPX, which makes the reagent useful in lead-zinc flows where zinc is activated with copper sulfate after lead has been removed.
Where the ore is fine-grained, heavily oxidised or contains tarnished sulfides, the circuit generally needs more collecting power — a longer-chain xanthate or a dithiophosphate added alongside SIPX.
SIPX vs SBX, SEX and PAX: Choosing by Ore and Circuit
The xanthate family is a gradient of collecting power against selectivity, and choosing well means matching the reagent to the ore rather than to habit:
| Collector | Alkyl chain | Collecting power | Selectivity | Typical use |
|---|---|---|---|---|
| SEX (sodium ethyl xanthate) | C2 | Low | Highest | Clean, fast-floating sulfides; differential flotation |
| SIPX (sodium isopropyl xanthate) | C3, branched | Medium | High | Copper, copper-molybdenum, lead-zinc |
| SBX / SIBX (butyl) | C4 | Medium-high | Medium | Bulk sulfide flotation, higher throughput |
| PAX (potassium amyl xanthate) | C5 | High | Lower | Gold, oxidised and tarnished sulfides, scavenging |
In practice, many plants run a split reagent scheme: a selective collector such as SIPX or SEX in the rougher and cleaner stages, with SBX or PAX added in the scavenger to recover the slower-floating values. For the butyl grades specifically, the SBX and SIBX comparison guide covers how those two isomers differ in practice.
Dosage, Pulp Chemistry and Control
SIPX is normally added as a 5-10% aqueous solution, metered into the conditioner or the flotation cell feed. Typical addition rates range from roughly 20 to 120 g/t depending on ore type, head grade and circuit configuration, but the useful number is always plant-specific and should be set by test work and confirmed by grade-recovery curves rather than copied from a data sheet.
Three control points matter more than the headline dose:
- pH. Xanthates are stable and effective in alkaline pulps, but excessive lime addition suppresses sulfide flotation and shifts selectivity. Control pH to the value the circuit was designed around, not higher.
- Grinding and slimes. Over-grinding consumes collector and reduces selectivity. If SIPX consumption climbs without a recovery gain, look at the grind first.
- Fresh solution. Prepare solution in batches sized to one shift. A xanthate solution left standing loses strength and its decomposition products can affect froth behaviour.
Handling, Packaging and Sourcing
SIPX is a moisture-sensitive, slightly irritating solid and is normally shipped in sealed, moisture-proof drums or bags within the specification agreed with the buyer. Because the product degrades with heat and moisture, purchasing decisions should weigh logistics as well as assay: short transit times, sealed packaging and consistent lot quality usually matter more than a marginal price difference.
For a material that is dosed in grams per tonne, small variations in active content translate into real consumption differences over a year. Buyers should therefore ask for lot-level assay, a reasonable shelf-life statement, and evidence that the supplier can hold specification across repeat shipments — the same discipline applied to any flotation reagent supply programme.
Conclusion
Sodium isopropyl xanthate earns its place as a mainstream collector because it balances two things that usually pull in opposite directions: enough collecting power to float copper, lead and activated zinc sulfides, and enough selectivity to leave pyrite behind. For copper and lead-zinc concentrators it is often the default rougher collector, and pairing it with a stronger xanthate in the scavenger covers the slow-floating fraction. Manage it as a reagent with a shelf life — buy on assay, keep it dry, prepare fresh solution and watch the grind — and SIPX will deliver consistent grade and recovery shift after shift.