Material guide: dimethyl sulfide — the molecule people mean by "the smell of the sea", filed under onion and cabbage

Put two things side by side.

People building a marine fragrance reach for this as one of the first candidates.

And the database's odour field for it reads:

sulfurous, onion, sweet, corn, vegetable, cabbage, tomato, green, radish, creamy, fishy, seafood, berry, fruity

No "marine". No "ozonic". No "salty".

And it genuinely is the smell of the sea. This piece is about how both of those hold at once.

The short version

• It is the smallest molecule this series has covered: C₂H₆S, molecular weight 62.13. Eighty-one suppliers.
• Four of its property fields are extremes for this series: boiling point 37.3 °C (below body temperature), flash point −36.7 °C, substantivity 4 hours at 100%, and a recommendation to smell it at 0.10% or less.
• It appears seven times across 954 public formulas, and all seven are pre-dilutions (0.1% or 1%). Converted to neat, the median dose is 80 ppm (0.0080%), ranging from 0.9 ppm to 150 ppm.
• Not one of those seven is a marine fragrance. They are wild strawberry, mulberry, blueberry muffin, two geranium reconstructions, a cream soap fragrance, and a Herbatin accord.
• In nature it really is the sea's signalling molecule. A 2014 PNAS paper describes it as an established foraging cue for marine top predators, and a 2012 study found loggerhead turtles respond behaviourally to it at 10 nmol/L, and not to cinnamon, jasmine or lemon.
• The occurrence field is equally long: asparagus, beer, cabbage, cheddar, corn, durian, garlic, onion…

About 8 minutes.

Seven appearances, all of them pre-dilutions

This is the first material in this series with zero neat appearances.

Across 954 formulas, dimethyl sulfide turns up seven times:

Formula	As written	Share of formula	Neat equivalent
mulberry type	1% dilution	1.500%	150 ppm
geranium imitation 10	1% dilution	1.000%	100 ppm
geranium imitation 20	1% dilution	1.000%	100 ppm
Herbatin accord	0.1% dilution	8.000%	80 ppm
blueberry muffin (Givaudan)	1% dilution	0.200%	20 ppm
wild strawberry type	1% dilution	0.105%	10.5 ppm
cream soap fragrance	1% dilution	0.009%	0.9 ppm

A median of 80 ppm, eight parts in a hundred thousand.

And the smallest is 0.9 ppm — under one part per million.

Two things stand out.

First, nobody weighs it neat. All seven go through a dilution, which is not a coincidence: the recommended smelling concentration is 0.10%, and the amount you put in a formula is one to two orders of magnitude below that. You cannot weigh 0.9 ppm on a balance.

Second, none of the seven is marine. They are fruit, geranium and soap.

That does not mean it cannot work in a marine fragrance — 74% of the corpus comes from patents and published sources, and its vintage bias is heavy, while marine as a genre is comparatively recent. What it does show is that in the recorded uses, this material is mainly doing fruit and vegetable work rather than sea work.

So why is it the smell of the sea

Because in the sea, it is.

Marine phytoplankton produce dimethylsulfoniopropionate (DMSP), whose breakdown releases dimethyl sulfide. Release rises when the phytoplankton are grazed or stressed. So a patch of ocean with a high dimethyl sulfide concentration above it is usually a productive patch with food in it.

And animals in the sea use that to find dinner.

Savoca and Nevitt studied the Southern Ocean food web in PNAS in 2014. They describe dimethyl sulfide as an established foraging cue for marine top predators, and present evidence that procellariiform seabird species that use dimethyl sulfide as a foraging cue selectively forage on phytoplankton grazers. The iron those birds recycle back into the water via excretion then feeds the iron-limited phytoplankton.

A tritrophic mutualism, mediated by an odour molecule.

The more direct evidence comes from turtles.

Endres and Lohmann ran a clean experiment in the Journal of Experimental Biology in 2012. They placed juvenile loggerhead sea turtles in a water-filled arena where odorants could be introduced into the air above the surface.

The result: turtles exposed to air that had passed over a cup containing 10 nmol/L dimethyl sulfide spent more time at the surface with their noses out of the water than controls exposed to air passed over distilled water.

The best part of that experiment is its control.

Odors that do not occur in the sea (cinnamon, jasmine and lemon) did not elicit increased surface time, implying that the response to DMS is unlikely to reflect a generalized response to any novel odor.

They did not run "smell versus no smell". They ran "sea smell versus not-sea smell". That step rules out the turtles simply being curious about anything new.

Their conclusion: the first demonstration that sea turtles can detect dimethyl sulfide, an ability that might let them identify favourable foraging areas.

So "the smell of the sea" is ecologically true — true in the sense that the molecule marks where the food is, rather than in the sense that it smells like the sea.

Properties: four extremes

Property	Value
CAS	75-18-3
Formula	C₂H₆S, MW 62.13
Appearance	colourless to pale yellow clear liquid (est)
Boiling point	37.3 °C
Melting point	−98 °C
Flash point	−36.7 °C
logP	0.90 (est)
Water solubility	22,000 mg/L at 25 °C
Substantivity	4 hours at 100%
Strength	high, recommend smelling at 0.10% or less
Shelf life	12 months or longer
Suppliers	81
Regulatory listings	JECFA, FEMA GRAS, CoE, FLAVIS

A boiling point of 37.3 °C is below body temperature. It boils in your hand. Open it cold and work quickly.

The flash point of −36.7 °C is the lowest this series has met, by a wide margin. Cineole is 48 °C, hexyl cinnamal 113 °C, veramoss 182.8 °C. This one ignites well below freezing. That is dangerous-goods territory for both shipping and storage.

Substantivity of 4 hours. Counting the 800 materials in the database with 20+ suppliers and a substantivity record, it ranks 43rd shortest. Set against Calone's >600 hours that is two and a half orders of magnitude. This is purely an opening material.

A recommended dilution of 0.10% is the most extreme in this series. Calone and veramoss are at 10%, Ambroxan at 1%, this one at 0.1%.

Water solubility of 22,000 mg/L matches phenethyl alcohol's. It goes into a water phase.

It is everywhere in food

The occurrence field runs long:

asparagus, beer, wheat bread, brussels sprout, butter, cabbage, celery, cheddar cheese, swiss cheese, cooked chicken, chive, cocoa, corn, cream, blackcurrant, durian, egg, fish, garlic, geranium, kohlrabi, cooked lamb, onion…

It carries a FEMA GRAS number and is a formal flavour material. The smell of boiled corn, boiled cabbage and aged cheese all contain it.

Which is why the seven corpus formulas are fruit and vegetable work. In the flavour world this is a mainstream material; in the perfume world it sits at the edge.

The two geranium formulas are the interesting ones. The occurrence field does list geranium — it is a genuine natural constituent of geranium's scent, so putting a little into a geranium reconstruction is restoring a molecule that is actually there.

Handling it in practice

1. Buy it pre-diluted. Somebody in the forum recommended buying a different material pre-diluted, and this one deserves it more. The neat material boils at 37 °C, flashes at −37 °C, and you need it in parts per million.

2. If you do have the neat material, chill it before opening. With a boiling point below body temperature, opening at room temperature loses material and scents an entire room.

3. Dilute in two steps. Going straight from neat to 0.1% means weighing an impossible amount. Make a 1% first, then take the 0.1% from that. We've written about weighing and dilution.

4. It is an opening material; do not expect it to stay. Four hours is the neat figure, and you are using parts per million. It is gone after the first few minutes.

5. Do not test anything else the same day. This is in the "recommend 0.1% or less" class, and it will contaminate every blotter you touch that day.

What this doesn't establish

I have not smelled it. The whole piece sets database fields, the formula corpus and two papers against each other.

"All seven are pre-dilutions" is a fact about these 954 formulas, not proof of industry practice. The count also depends on the corpus recording the dilution in the name — a formula using the neat material without saying so would be missed.

The 80 ppm median is the median of seven values. Seven samples cannot describe a distribution, which is why I listed all seven.

"None is marine" comes from reading those seven formula titles (wild strawberry, mulberry, blueberry muffin, geranium imitation ×2, cream soap, Herbatin). I did not read the full contents to judge what each was aiming at.

Savoca's paper is an ecological study of the Southern Ocean food web, not a study of odour. I cite its description of dimethyl sulfide as a foraging cue and its tritrophic finding.

Endres's study used juvenile loggerheads in a laboratory behavioural test. Time spent with the nose out of the water is a proxy, not a direct measurement of turtles swimming toward food.

10 nmol/L is the source concentration in the cup above the water, not a concentration in the sea. I cannot convert it into a field exposure.

"High concentration above the surface means high productivity" is my statement of background. Both papers rest on that premise, and neither of the two I cite is the study that measured the association.

The boiling point field holds two values (37.30 °C and −37.50 to −37.30 °C), the second of which looks wrong. I use 37.3 °C because that matches this molecule's known boiling point, but the field itself has a problem in it.

The GHS field is empty in this record. And a blank is not a safety conclusion — this is a highly flammable low-boiling sulfide, so work from the SDS for your own batch.

References

M. S. Savoca, G. A. Nevitt, Evidence that dimethyl sulfide facilitates a tritrophic mutualism between marine primary producers and top predators, Proceedings of the National Academy of Sciences, 111(11), 4157-4161 (2014). PMID 24591607. doi:10.1073/pnas.1317120111

C. S. Endres, K. J. Lohmann, Perception of dimethyl sulfide (DMS) by loggerhead sea turtles: a possible mechanism for locating high-productivity oceanic regions for foraging, Journal of Experimental Biology, 215(20), 3535-3538 (2012). PMID 23014568. doi:10.1242/jeb.073221

Related: he asked whether one or two would do, Calone, weighing and dilution, the starter palette map.