SLES 70: specification, dilution and handling

Technical article · Eapearl Chemical · 6 May 2026

Sodium lauryl ether sulfate at seventy percent active matter is the most widely traded anionic surfactant concentrate in the world, and also one of the most often mis-ordered. The number in the name describes the active content, not the product; the rest of the identity sits in the ethoxylation degree, the chain distribution and a handful of specification lines that decide how the material behaves in a mixing vessel.

What the seventy actually refers to

The material is a mixture rather than a single molecule: fatty alcohols of a defined chain-length range, ethoxylated to an average number of ethylene oxide units, then sulfated and neutralised with sodium hydroxide. Because the composition is a distribution, it is registered as a substance of variable composition, and more than one identifier is in circulation for it. The generic polymer-style entry CAS 9004-82-4 appears on many data sheets, while grades built on a narrower cut are commonly identified as CAS 68585-34-2, EC 271-557-7, for the ethoxylated and sulfated sodium salts of C12 to C14 alcohols. In cosmetic ingredient nomenclature the same family is declared as sodium laureth sulfate.

Ethoxylation degree belongs on the order

The average number of ethylene oxide units is the single most consequential variable after active matter. Two units is the general-purpose grade that most formulations are built around. Fewer units move the material towards the behaviour of the plain alkyl sulfate: lower water solubility, a different foam and a sharper response to cold. More units increase solubility and electrolyte tolerance and soften the sensory profile, at a cost in foam volume and in the raw material. Note also that the number is an average across a distribution, which is why two suppliers quoting the same figure can still give different results in a salt curve.

Chain length and feedstock origin

The alcohol feedstock may be oleochemical, derived from palm kernel or coconut oil, or petrochemical. Commercially the distinction rarely changes performance at a given chain cut, but it changes the documentation: sustainable-palm certification, mass-balance or segregated supply chain claims, and origin statements are all feedstock questions and have to be specified at enquiry, not requested later.

What the certificate of analysis has to carry

• Active matter — the number you are buying, normally by two-phase titration. Compare offers on active matter, not on tonnage of paste.
• Unsulfated matter — residual ethoxylated alcohol that never reacted. It contributes nothing to detergency and can carry odour and cloudiness.
• Sodium sulfate and sodium chloride — inorganic residues, and the hidden variable behind most viscosity complaints, as described below.
• pH of a dilute solution — stated with the dilution used. A drifting pH is an early sign of hydrolysis in store.
• Colour — the routine indicator of thermal history during manufacture, transport and storage.
• 1,4-Dioxane — the ethoxylation by-product, with the method stated and a per-lot result where the end use is cosmetic.
• Water content and microbiological status — the latter matters far more for dilute grades than for the concentrate.

Salt is not a trivial impurity

Formulators build the viscosity of shampoos and washing-up liquids by adding sodium chloride, and the response is a curve with a maximum: below it, more salt thickens; beyond it, more salt thins. The starting point of that curve is set by the chloride already present in the surfactant. A batch arriving at the top of its chloride specification and another at the bottom will place your formulation at two different points on the curve before you have added anything. If finished-product viscosity is a release parameter, either tighten the incoming chloride band or move to dosing salt against a measured viscosity endpoint.

The gel phase, and why concentrate is not simply strong solution

A seventy percent paste is not a liquid in the way a dilute solution is. As water is added, the system passes through a liquid-crystalline region in which viscosity rises before it collapses again at lower active content. The practical rule that follows is fixed: add surfactant to water, under agitation, never water to surfactant. Pouring water onto the paste creates the high-viscosity phase exactly at the interface, and that skin then protects the concentrate underneath from further contact with water, producing the lumps that resist hours of stirring. Warm the drum or IBC enough to make the paste pumpable before transfer, use a pump chosen for viscous duty, and give the vessel enough agitation to keep the whole batch turning over rather than just spinning a hole in the middle.

Stability, storage and transport

Alkyl ether sulfates hydrolyse. The reaction splits the molecule back into the fatty alcohol ethoxylate and an acidic sulfate fragment, and because the products are acidic, the reaction accelerates itself once it starts. Two conditions drive it: low pH and prolonged heat. That gives a narrow operating window. The paste must be warm enough to pump, but sustained heating darkens the product and starts hydrolysis, so heat locally and briefly at transfer rather than keeping a whole tank hot for weeks. Keep the material on the alkaline side of neutral, store it in stainless steel or a suitably lined vessel, and keep it sealed, since the surface of an open container skins and takes up water. Cold storage brings the opposite problem: the paste stiffens and becomes unpumpable long before anything is chemically wrong with it, so winter deliveries need a heating plan agreed before dispatch.

Where it is used

The same paste serves markets with very different tolerances. In personal care it is the primary foaming and cleansing surfactant of shampoos, shower gels and bubble baths, usually paired with an amphoteric co-surfactant. In household products it drives hand dishwashing liquids and hard-surface cleaners. Industrial and institutional cleaning uses it as a wetting and foaming agent where its electrolyte tolerance suits alkaline builders. Outside cleaning altogether, it appears as an emulsifier in emulsion polymerisation, as a wetting agent in textile processing, as a foaming agent in gypsum and cement-based building products, and in oilfield and agrochemical formulations. Each of these puts a different line of the certificate in first place, which is why a supplier asking what the material is for is not being inquisitive.

Classification and documentation

The substance has no harmonised European classification, so the hazard statements you see come from the supplier’s own assessment and may legitimately differ between sources. What does not differ is the practical point: the concentrate is a serious eye hazard and the dilute solution is a much milder one, so the safety data sheet you work from must be the one for the concentration you are actually handling. Alongside the safety data sheet and the per-lot certificate, a cosmetic or household customer will normally ask for a manufacturing-practice statement, a palm-origin or sustainability declaration where applicable, a statement on animal-derived materials, and an allergen declaration. Agreeing that list before the first order is faster than assembling it during an audit.

Ordering mistakes that cost time

1. Writing only the trade abbreviation, without the ethoxylation degree or the active matter.
2. Comparing prices per tonne of paste instead of per tonne of active matter.
3. Leaving chloride and sulfate unspecified, then investigating viscosity drift downstream.
4. Treating a dilute grade as the concentrate plus water, and ignoring that it now needs preservation.
5. Booking a winter delivery with no heated unloading capability on site.
6. Accepting a generic by-product statement in place of a per-lot analytical result.

Grade selection, samples for qualification and specification sheets against a named end use are handled on request.