Beginner perfumer · 54
Is Rose Oxide 70 worth the international shipping? Converting 5 percentage points into what you actually lose
· 24 min read
Somebody posted a precisely framed question on r/DIYfragrance: the formula calls for Rose Oxide 70 (cis:trans 70:30), the material generally on sale is 75:25, both carry CAS 16409-43-1, and the 70:30 version means paying overseas shipping and import duty. All 10 replies said it makes no difference under 1 percent, and nobody converted those 5 points into a quantity. It works out to 6.7 percent less cis, and it stays 6.7 percent whether you dose at 0.5 or at 2 percent. The side question about how one CAS can cover two materials has its answer written in the database's assay field: 99 to 100, sum of isomers. And the same set of records holds something more worth looking at: the substantivity field for one molecule reads 8 hours in one record and 388 hours in another.
About a 7 minute read.
The question was framed cleanly.
"racemic Rose Oxide has cis isomer ~ 75% so basically a 75 to 25 ratio wheres 'Rose Oxide 70' claims to have a 70 to 30 ratio.
My formula calls for Rose Oxide 70, which is more difficult to find. PCW offers it but it has high delivery fee to the US plus imports. Not sure is worth it and I'm wondering if the difference is even detectable especially when the formula uses less than 1%
I'm new to this and would appreciate your feedback. Thank you.
p.s. what is the point of CAS if two different materials can have the same number?"
Ten replies came in, all pointing the same way.
"If its less than 1%, its totally interchangeable" (frioke)
"Won't mess your formula, just buy the regular one. %5 isomer ratio difference quite negligible if the formula calls for less than %1-2" (Superb_Walk4874)
"If the formula uses less than 1% Rose Oxide, those small differences get completely buried." (JessieAndEcho)
I agree with the conclusion. Nobody converted those 5 points into how much less of anything he would actually get, and that conversion is one line of multiplication that yields a more useful number than the one he asked for.
How much is 5 percentage points
What he is buying is the cis isomer. The difference shows up in how much cis he gets.
| Dose in formula | cis at 75:25 | cis at 70:30 | Difference |
|---|---|---|---|
| 0.5% | 0.3750% | 0.3500% | 250 ppm |
| 1.0% | 0.7500% | 0.7000% | 500 ppm |
| 2.0% | 1.5000% | 1.4000% | 1000 ppm |
The absolute figure moves with dose. The relative one does not: 6.7% less cis.
Whether he doses at 0.5% or at 2%, switching to 70:30 costs him 6.7% of the cis.
The thing to set beside that number is weighing error. To get 0.5% rose oxide into a formula, most people make a 10% dilution first and take from that. The pipetting error on that step, the concentration error in the dilution itself, and the resolution of the scale add up, and 6.7% is easy to exceed.
What the shipping fee would buy him is a difference smaller than his own dosing precision.
The case that flips
The database's solubility field carries supplier product text mixed into it, and these grades appear in it:
- Rose Oxide d,l 70:30
- Rose Oxide d,l 90:10
With the 75:25 the asker names, that is at least three ratios sold under one CAS.
90:10 against 70:30 is a different matter. The cis difference is 22.2%, more than three times the gap between 75:25 and 70:30.
If what he is looking at is 90:10, the line moves.
"What is the point of CAS"
Somebody answered this correctly.
"CAS numbers can apply to mixtures that have a range of substitution degrees or isomer distributions. It wouldn't surprise me if 75/25 and 70/30 are considered the same in that respect." (Odd_nonposter)
The evidence sits in the database's assay field. For (Z)-rose oxide (#35233), that field reads:
99.00 to 100.00 sum of isomers
Those three words are written into the specification. This CAS governs the total, not the ratio. Both products conform, because the spec never governed the ratio.
Another reply in the thread supplied the other half.
"The point of CAS is to give a number for each racemic mix of isomers and then specifically for each isomer. Rose Oxide (Racemic) has one CAS number no matter the exact mix of isomers. Rose Oxide Laveo has another CAS number because it consists almost solely of the Laveo entianometer." (CapnLazerz)
The database can test that. Rose oxide has five records in it.
| Record | CAS | Suppliers |
|---|---|---|
| (Z)-rose oxide (cis, racemic) | 16409-43-1 | 77 |
| laevo-rose oxide (2S,4R) | 3033-23-6 | 8 |
| (-)-(E)-rose oxide (2R,4R) | 5258-11-7 | 1 |
| (E)-rose oxide (2R,4S) | 4610-11-1 | 0 |
| dihydrorose oxide | 13477-62-8 | 2 |
Each specified configuration has its own number, and the unspecified one is shared. His account holds up.
The regulatory numbers split again
Writing about Cetalox last time turned up a pattern: CAS splits into two, FEMA and the Council of Europe merge into one. Here it is again.
| FEMA | CoE | JECFA | FLAVIS | |
|---|---|---|---|---|
| (Z)-rose oxide | 3236 | 2269 | 1237 | 13.037 |
| laevo-rose oxide | 3236 | 2269 | none | 13.170 |
FEMA and the Council of Europe assign one number; FLAVIS assigns two.
Two entirely unrelated materials, and both times FEMA and CoE landed on the merging side. This is starting to look like a rule rather than a coincidence.
Can anybody smell it
Laska and Teubner measured human discrimination of 10 enantiomer pairs in Chemical Senses in 1999: 20 subjects, forced-choice triangular test.
Rose oxide is among the seven pairs they could not distinguish.
I used this paper last time as a general point. Here it tested this material directly.
The comparison is not the same one, though. Laska tested (+) against (-), while the asker faces a difference in cis ratio inside a racemic mixture. Those are different questions. The direction still carries: if single enantiomers cannot be told apart, moving the ratio of a racemic mixture by 5 points is harder still.
The ratio is not meaningless
One thing needs saying so the conclusion does not get pushed too far. Cis is the one doing the work.
Wang and colleagues studied lychee-like aroma in grapes in Food Chemistry in 2026, using metabolomics and molecular sensory analysis. The key volatiles they identified were cis-rose oxide and citronellol. The paper writes cis-rose oxide, not rose oxide generically.
Suppliers are not printing a ratio for nothing. The cis fraction is a real activity marker for this material. It is just that a 5-point shift falls inside the user's own handling error.
A field problem picked up along the way
Going through the five records turned up something more worth recording than the original question.
The substantivity field:
| Record | Field text | substantivity_hr |
|---|---|---|
| (Z)-rose oxide | > 8 hours (100% neat) | 8.0 |
| laevo-rose oxide | 388 hours (10% in dipropylene glycol) | 388.0 |
Same molecule. 8 against 388, a factor of 48.5.
The difference is not in the molecule but in the measurement. One is neat and is a greater-than lower bound; the other is a point value at 10% in dipropylene glycol. There is no conversion between those two protocols.
And substantivity_hr puts 8.0 and 388.0 in the same column.
Sorting by that field to find long-lasting materials puts rose oxide at both ends of the list.
Writing about substantivity earlier I flagged that a greater-than sign marks a lower bound rather than a value. Here the same problem appears across two records of one molecule, which is a cleaner example than the earlier ones.
A misremembering in another thread
A year ago on the same board, somebody asked whether to use laevo rose oxide diluted, and this exchange followed.
"Is it fully dissolved? Rose oxide is notorious for saturating around 5% or less..." (grittyshrimps)
"Haven't heard this. I also have rose oxide dissolved in 10% eth no problem. Racemic tho. Now rose crystals on the other hand, those bastards are stubborn even at 5%..." (fibonaccighost)
"Ah, I stand corrected. I had the two confused, sorry!" (grittyshrimps)
They corrected themselves, and the database is on the side of the correction. Rose oxide boils at 182 C, the database gives it no melting point, and the appearance field reads "pale yellow to yellow clear liquid". It is a liquid, with no room-temperature crystallisation to worry about. Water solubility is 764 mg/L at 20 C, and that one is measured rather than estimated.
What stands out may be that this kind of correction is uncommon on forums. Corrected, they withdrew rather than arguing.
The corpus
Across 954 published formulas, 76 use rose oxide, or 8.0%.
Median dose 0.500%, 90th percentile 1.857%, maximum 8.60%, minimum 0.006%.
74% of uses are below 1%.
The forum's premise that everybody uses it under 1% holds up in the corpus.
By spelling: the rose oxide family totals 70, laevo-rose oxide 4, cis-rose oxide 1, dihydrorose oxide 1. Fewer than 6% specify a configuration.
What you can actually do
- Buy the ordinary 75:25. It costs 6.7% of the cis, which sits inside your own weighing error.
- If what you are looking at is 90:10, think again. That is 22.2% against 70:30.
- Under a shared CAS, check whether the assay field says "sum of isomers". If it does, the spec governs the total rather than the ratio and both products conform.
- The laevo version has to be bought separately. It has its own CAS (3033-23-6), 8 suppliers, and 4 appearances in the corpus.
- Do not sort across records by the substantivity field. One molecule can read 8 hours or 388 hours in this database depending on how it was measured.
- Start at 0.5%. That is the corpus median, and 74% of uses sit under 1%.
What this doesn't establish
- I have not smelled any of these ratios. This is database fields, corpus and two papers.
- On "6.7% sits inside weighing error", I did not measure the actual error of a home scale and pipette. That is my judgement, based on a 10% dilution step being involved.
- The 75:25 figure comes from the asker. In the database's supplier text I found 70:30 and 90:10, not 75:25.
- Laska 1999 tested (+) against (-), not a ratio difference within a racemic mixture. What carries is the direction, not the magnitude.
- Laska had 20 subjects, and the paper itself reports wide individual variation (from a subject who discriminated 6 of 10 pairs to one who failed 9). "Cannot distinguish" is a group-level result.
- Wang 2026 studied grapes, not perfume. It shows cis is a key volatile for the lychee note; it did not test the sensory effect of changing the cis:trans ratio.
- I could not find a citable figure for how far the odour thresholds of cis and trans differ. If they differ a lot, the ratio matters more than I have written. That is the biggest gap in this piece.
- On the 8 versus 388 substantivity figures I only established that the two protocols differ. Which is closer to practice, I cannot say.
- The corpus dose statistics are from concentrates, not finished sprays.