"This material won't dissolve" — why you can't look up whether it arrives as a solid

A complaint on r/DIYfragrance, well written:

"I have been working with hundreds of materials without any issues until i met Tonalide… big chunks need to be crushed into powder and then stirrrrrr until you get bigger biceps then Arnold. What was your most difficult material you worked with?"

Thirty-one replies produced a list. The materials named:

Named material	The complaint
Tonalide	Solid chunks; two days at 10% in ethanol before it fully dissolved
Wool absolute	Had to scrape it up with a spoon, then drop bits carefully into the bottle
Mate absolute	"Stickiest tar on the planet"; thirty minutes to get 0.01 g
Olibanum resinoid	"Worse than strongman tacky"; two days to dissolve
Benzoin Sumatra	Easy to weigh, forever to dissolve
Pine absolute	"Like sticky chewing gum you're supposed to scrape off in a quantifiable manner"
Corps Oranger	Ethanol solubility around 1%; permanent layer of yellow grains at the bottom
Ambrocenide crystals	Painfully slow in DPG
Oceanol, IBCH	Too viscous to get out of the bottle

The value of this thread is not the list. It is why these people have to ask each other.

The short version

• For the 120 most-used materials in the corpus, this site's database holds: no appearance field for 41 of them, no melting point for 91, and both fields for only 29.
• Across all 42,225 records, only 3,080 (7.3%) carry any melting point data.
• Of the 10,270 records with an appearance value, 10,248 (99.8%) end in (est) — an estimate, not a measurement.
• And the 41 that came back empty form a tidy list: hedione, lilial, iso e super, galaxolide, triplal, aldehyde c-10, aldehyde c-14 — all trade names. The database indexes by chemical name; perfumers buy by trade name.
• Of the 29 with both fields, one contradicts itself: α-amyl cinnamaldehyde carries a melting point of 80 °C and an appearance of "pale yellow to yellow clear liquid".
• And Tonalide's difficulty is not a solubility limit. Its logP is 5.30, and it dissolves well in ethanol. What is slow is the dissolution rate, not the solubility ceiling. That distinction decides which method to use.

The database is silent on this

Start with the step I expected to be easy.

The plan was simple: take the 120 most-used materials from the corpus, check them against the database's appearance and melting point fields, and produce a table of which ones arrive as solids. That table is useful to a beginner, because it determines whether you need a warm water bath on delivery day.

The result:

	Materials
Has an appearance field	79
Has a melting point field	29
Has both	29
Has neither	41

For 41 of 120, the database says nothing about physical state.

And those 41 are not random. The first twenty: hedione, lilial, bergamot oil bergaptene reduced, ylang ylang oil, iso e super, cis-3-hexenol, cinnamic alcohol, γ-undecalactone, galaxolide 50 ipm, cis-3-hexenyl acetate, styrallyl acetate, cis-3-hexenyl salicylate, rose oxide, aldehyde c-10, aldehyde c-14, triplal, aldehyde c-12 mna, aldehyde c-11 undecylenic, orange oil, aldehyde c-12 lauric.

That is a list of trade names. Hedione is methyl dihydrojasmonate; Iso E Super is a heptamethyl octahydronaphthalenone; Triplal is a hexenal. The database indexes by chemical name, while formulas and suppliers use trade names. This series ran into the same wall a few rounds ago while trying to update the overview map. Here it appears in another form: you cannot look up whether Iso E Super is a solid, because nothing in the database is called that.

That essential oils and absolutes (ylang ylang oil, orange oil) have no single melting point is entirely reasonable — they are mixtures. But it also means the database cannot help you, and only the person on the forum will tell you that mate absolute behaves like tar.

99.8% of the appearance values are estimates

One layer further down, the situation is more worth knowing.

Of the 10,270 materials with an appearance value, 10,248 carry (est). That is 99.8%.

Which means that "white crystalline powder" and "colorless clear liquid" are, almost always, inferred from structure rather than written down by someone who opened a bottle and looked.

That explains the contradiction. Of the 29 materials with both fields, one does not reconcile:

α-amyl cinnamaldehyde (70 formulas, median dose 7.23%) Melting point field: 80.0 °C Appearance field: pale yellow to yellow clear liquid (est)

Nothing melting at 80 °C is a clear liquid at room temperature. This material is a liquid in practice, so the 80 °C value is almost certainly wrong — perhaps a reduced-pressure boiling point filed in the wrong column, perhaps a flash point. This series handles database errors by flagging them plainly and not speculating about causes: do not use that field.

One error in 29 is not many. But the point stands: if one of 29 fails to reconcile and the other 91 have nothing to reconcile against, this table can answer very little.

The reliable solids list

Tighten the standard to "melting point and appearance agree that it is a solid" and ten of the 120 most-used materials survive:

Material	Formulas	Median dose	Melting point
Coumarin	225	2.44%	68 °C
Heliotropin	140	3.17%	37 °C
Vanillin	137	1.02%	81 °C
Indole	88	0.77%	51 °C
Musk ketone	84	4.00%	135 °C
Ethyl vanillin	80	0.56%	76 °C
Dimethyl benzyl carbinyl acetate	57	2.64%	30 °C
Raspberry ketone	45	0.79%	82 °C
Ambroxan	31	0.20%	74 °C
Diphenyl oxide	29	1.13%	27 °C

Two more read "semi-solid" in appearance with no melting point: oakmoss absolute (37 formulas) and siam benzoin resinoid (27). Benzoin is exactly the one named on the forum.

Coumarin is at the top, and coumarin is the single most frequently occurring material in the whole corpus — 225 formulas, 23.6% of 954.

The implication for a beginner is direct. Your first set of materials will almost certainly include coumarin, and it will arrive as crystals. Nobody marks this on the starter lists.

Two more worth noticing: dimethyl benzyl carbinyl acetate melts at 30 °C and diphenyl oxide at 27 °C. These are solid in a cold room, possibly liquid in summer, and will melt in your hand. Materials like this are the ones most often mistaken for a defective delivery.

Won't dissolve, or dissolves slowly

The forum's methods split into two camps, resting on two different assumptions.

Crush and stir (what the poster started with) assumes the limit is contact area. Heat and wait (kdoughboy12, CapnLazerz, RingerArnos187, Ok-Wheel9962) assumes the limit is time and temperature.

Four people said the same thing independently:

"Why are you crushing and stirring? Just weigh the little chunks like crack rocks and throw em into a vial with ethanol and wait lol." (kdoughboy12)

"I don't crush Tonalide, I just break the chunks as needed. I put the vial of concentrate in my pocket for an hour or two, give it a few swirls every now and then and bingo-bango, it's in solution. You could also do the rice bowl trick or a warm water bath. It really just needs gentle heat and time." (CapnLazerz)

The poster's own conclusion: "That's what I did in the end. Bowl with warm water and waited a bit, it worked better than stirring."

Which camp is right depends on whether you are stuck on solubility or on dissolution rate.

• Solubility is the ceiling: how much this solvent can hold at all. Against the ceiling, neither crushing nor heating solves it (heat raises the ceiling, but it comes back down on cooling).
• Dissolution rate is how fast you get there. Temperature, contact area and agitation all matter.

Tonalide's data is clear: logP 5.30, water solubility 0.2879 mg/L. This is a strongly lipophilic molecule, and its ethanol solubility is nowhere near the constraint. Someone waiting two days at 10% was not sitting above the ceiling; the rate was slow.

Another comment draws the line in the same place: "It's just difficult over 10%" (AdministrativePool2) — meaning it is only at higher concentrations that the ceiling starts to matter.

Corps Oranger is the opposite case:

"Its solubility in ethanol by itself is quite low (around 1%). So I have a saturated ethanol solution at an assumed 1% that I use just the liquid portion of, with bright yellow grainy gunk at the bottom." (Feral_Expedition)

That one is against the ceiling. More heat, more crushing, more waiting: the layer stays. Using only the supernatant is the right handling, and he is honest that it is an assumed 1% — he does not know the actual concentration of what he is decanting.

So the test is this: if another day makes it better, it's a rate problem and you use heat and time. If a week later there is still sediment, it's a solubility problem and you lower the concentration or change solvent.

Even coumarin's solubility data doesn't reconcile

The obvious response is "just look up the solubility". I tried that too.

A 2022 paper by Cysewski, Jeliński and Przybyłek in Molecules opens on exactly this problem. Their subject is coumarin — the solid at the top of the list — and its solubility in neat alcohols.

The reason they took it up is in the abstract: "Despite the extensive use of coumarin, there are only a few reports documenting its solubility in organic solvents, and some reported data are incongruent."

So they did two things. First they built a consistency test using COSMO-RS-DARE to determine intermolecular interaction parameters, which let them identify outliers as suspicious datasets. Then they measured coumarin's temperature-dependent solubility experimentally in seven neat alcohols — methanol, ethanol, 1-propanol and 2-propanol for reproducibility, plus 1-butanol, 1-pentanol and 1-octanol to extend the homologous series.

A material used in 225 published formulas, known for more than two centuries, needed a dedicated paper to determine which of its published ethanol solubility figures could be trusted.

Which answers the question of why the people on that forum ask each other. It is not that they cannot be bothered to look it up. It cannot be looked up.

The paper also supplies one practical warning that none of the 31 replies mentions: solubility varies with temperature. After a warm water bath opens something up, the solution cooling back to room temperature may be carrying more than room temperature can hold. Leave it a few days and it comes back out.

So if you used heat, look at the bottom of the bottle again once it has cooled. Nobody on the forum says this, and it is the cost of the heat method.

What I got wrong this round

I set out to build the complete "which of these arrive as solids" table, as an appendix to the starter list. Halfway through I found I could fill ten cells, and the other 110 were missing either data or a matching name.

At one point I considered filling the gaps with estimated melting points derived from structure. I stopped, because the database's appearance field is already doing exactly that, 99.8% of it is estimated, and it has already produced an error like the α-amyl cinnamaldehyde entry. Stacking another layer of estimation on top would only produce a table that looks complete and has not one trustworthy cell.

So this piece went from "here is the table" to "the table cannot be built, and that is itself worth knowing". The ten cells are real. I am not filling the other 110.

What is actually usable

• Coumarin arrives as crystals, and it is the most used material there is. Knowing beforehand beats being surprised.
• The ones melting between 27 and 40 °C (diphenyl oxide, dimethyl benzyl carbinyl acetate, heliotropin) change state with room temperature. That is not spoilage.
• Separate "won't dissolve" from "dissolves slowly" first. Progress after another day means a rate problem: warm water bath and time. Sediment after a week means a ceiling problem: lower the concentration.
• After using heat, check the bottom again once it is back at room temperature. Solubility falls back with the temperature.
• Trade-name materials have no lookupable properties. For Iso E Super, Hedione, Triplal and their kind, you ask a person or ask the supplier for a spec sheet. This is not a failure of your search skills.
• The forum consensus is right: gentle heat plus time beats crushing plus stirring, provided what you are stuck on is rate.

What this doesn't establish

• "The 120 most used" is counted from 954 published formulas, not from sales. The materials most people actually buy need not be these 120.
• Absence in the database is not absence in the world. Supplier spec sheets usually carry a melting point; it simply has not made it into this database. What is measured here is whether this database can answer, not whether the answer exists anywhere.
• I did not investigate what (est) means. The database does not document its estimation method or give an error range. All I can report is how often the marker appears.
• I judged the α-amyl cinnamaldehyde field wrong but did not verify the correct value. The reasoning — that an 80 °C melting point and a clear liquid at room temperature cannot both hold — is sound, but I did not go and find the right number.
• The solubility versus dissolution-rate distinction is a general principle, not a measurement of these particular materials. Apart from coumarin, I have no measured ethanol solubility for any of them.
• Cysewski's group measured coumarin in neat alcohols, not in aqueous ethanol or DPG, and not in a mixture containing other fragrance materials. Practical solvents are almost never neat.