A practical guide to sulfated castor oil, why it emulsifies where ordinary oils will not, what separation in the drum actually means, and how it is supplied, from a US-based distributor.
Sulfated castor oil (Turkey Red Oil, CAS 8002-33-3) is an anionic surfactant and lubricity additive made by treating castor oil with sulfuric acid. It disperses in water to give stable oil-in-water emulsions, which is why it anchors water-soluble metalworking fluids and serves as a fatliquor in leather and a softening and wetting agent in textiles. Stratus Chemical supplies SCO 70%, a highly sulphated, very light-coloured grade, in drums and totes.
| Property | Value |
|---|---|
| Chemical name | Castor oil, sulfated |
| Synonyms | Turkey Red Oil, TRO, sulphated castor oil, sulfonated castor oil, sulforicinoleate |
| CAS number | 8002-33-3 |
| EC / EINECS | 232-306-7 |
| Chemistry | Sulphated castor oil |
| Charge | Anionic |
| Function | Emulsifier / lubricity |
| Density | 8.75 lbs/gal |
| Shelf life | 12 months when properly stored |
| Grades supplied | SCO 70% (highly sulphated) |
| Packaging | Drums, totes |
| Documentation | COA & SDS provided on request |
The figures below are representative of SCO 70%. They are indicative rather than guaranteed: values vary by lot, and the certificate of analysis for your material governs.
| Property | Unit | Specification |
|---|---|---|
| Charge | — | Anionic |
| Moisture content | % wt | 28.0 – 30.0 |
| Free fatty acids | % wt | 5.0 – 12.0 |
| Combined SO3 | % wt | 5.0 – 6.0 |
| pH (10% solution) | — | 7.0 – 8.0 |
| Density | lbs/gal | 8.75 ± 0.05 |
| Emulsion (10% in distilled water) | — | Clear, stable |
Castor oil is unusual among vegetable oils because its dominant fatty acid, ricinoleic acid, carries a hydroxyl group partway along the chain. That hydroxyl is a handle nothing else offers, and sulfation attaches a sulfate group to it.
The result is a molecule with an oil-soluble tail and a water-soluble anionic head — a surfactant built out of a triglyceride. Ordinary castor oil floats on water; sulfated castor oil disperses into it and holds other oils in emulsion alongside itself.
The degree of sulfation is what separates grades. More sulfation means more water-dispersibility, more stable emulsions, and a lighter colour. SCO 70% is a highly sulphated grade, which is why its emulsion is specified as clear and stable rather than merely dispersible, and why it suits applications where colour carries into the finished product.
Two lines on the analysis follow directly from this. Combined SO3 is a direct measure of how much sulfate is chemically bound to the oil, which is the property being bought. Free fatty acids are the unbound acid left from processing; it is normal in a sulfated oil and specified as a range rather than driven to zero.
The largest industrial use. In water-soluble cutting, grinding, and drawing fluids, SCO acts as both the emulsifier that holds the oil phase dispersed and a lubricity additive in its own right, boosting film strength at the tool-workpiece interface and contributing rust protection. A soluble oil concentrate that will not emulsify cleanly is unusable, so the emulsion quality specification matters more here than almost anything else.
Used as a fatliquor, the oil emulsion that re-lubricates leather fibres after tanning so the finished hide stays soft and flexible rather than drying hard. It also serves as a topping oil and as a plasticiser in finish coatings.
A softening and wetting agent in textile processing, and the historical dye assistant that gave the product its name: the Turkey Red dyeing process depended on it long before synthetic surfactants existed.
SCO appears in agricultural adjuvants, in personal care as a solubiliser and emollient, and as a general-purpose wetting and dispersing agent where a natural-origin anionic surfactant is wanted.
SCO is soluble in water and is handled as any non-hazardous fatliquor. Bring it to room temperature before use; cold material is thick and will not disperse or meter properly.
One point causes more unnecessary rejections than any other: all fatliquors are emulsions and may separate over time. This is normal. A drum that has stood for months may show a distinct layer, and that is not a sign the product has failed. Mix it well before use and it will perform properly. Judging the material by its appearance in a settled drum rather than by mixing it first leads to good product being sent back.
Optimum performance and shelf life are maintained when the product is stored near room temperature. Keep it from freezing and from overheating; both damage the emulsion in ways that mixing will not reverse.
Shelf life is 12 months when properly stored. Normal safety precautions apply in handling; refer to the Safety Data Sheet for detailed information on hazards, handling, and disposal.
Sulfated castor oil is used as an anionic emulsifier and lubricity additive. Its largest industrial use is in water-soluble metalworking fluids, where it emulsifies the oil phase and boosts film strength and rust protection in cutting, grinding, and drawing operations. It is also used as a fatliquor and finish-coating plasticiser in leather, as a softening and wetting agent in textile processing, and in agricultural and personal care formulations. Stratus Chemical supplies SCO 70% in drums and totes.
The CAS number for sulfated castor oil is 8002-33-3 and its EC number is 232-306-7. It is also known as Turkey Red Oil or TRO, sulphated castor oil, sulfonated castor oil, and sulforicinoleate. Its formal chemical name is castor oil, sulfated.
The name comes from the Turkey Red dyeing process, a traditional method of producing a brilliant fast red on cotton in which sulfated castor oil was an essential component. The product predates synthetic surfactants by a long way and is often described as the first synthetic detergent. The name persists in the textile and leather trades while sulfated castor oil is the term used in metalworking and industrial contexts.
Because of ricinoleic acid, the dominant fatty acid in castor oil, which carries a hydroxyl group partway along its chain that other vegetable oils do not have. Sulfation attaches a sulfate group at that site, producing a molecule with an oil-soluble tail and a water-soluble anionic head. That is the structure of a surfactant, so the treated oil disperses into water and holds other oils in emulsion alongside it, while untreated castor oil simply floats.
No. All fatliquors are emulsions and may separate over time, and a distinct layer in a drum that has stood for a while is normal rather than a sign of failure. Mix the material well before use and it will perform properly. Bring it to room temperature first, since cold product is thick and will not disperse evenly. Judging the material by its appearance in a settled drum, without mixing it, is the most common reason good product gets rejected.
Combined SO3 measures how much sulfate is chemically bound to the oil, which is a direct measure of the degree of sulfation. That is the property you are actually buying: higher sulfation means better water-dispersibility, more stable emulsions, and lighter colour. It is distinct from free fatty acids, which are the unbound acid remaining from processing and are specified as a normal range rather than driven to zero.
Stratus Chemical supplies SCO 70% in drums and totes, with a certificate of analysis and Safety Data Sheet provided on request. Store it near room temperature and keep it from freezing or overheating, both of which damage the emulsion in ways mixing will not reverse. Shelf life is 12 months when properly stored. Tell us the volume you need and we will confirm pricing and availability within one business day.
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