Changelog

What is new and what changed on Cheméo, most recent first.

2026-11-09

Changed

• Compound identities corrected (v28). 5,487 compounds were checked against their own sources and corrected. 554 structures changed; the others gain the configuration their name and CAS number give, such as L-valine or (R)-limonene, or lose one no source supports. 12 CAS numbers and 19 names were corrected: L-Alanine, L-Valine, L-Leucine, L-Serine, L-Aspartic acid, L-Methionine and L-Phenylalanine now carry the name of the enantiomer their CAS number gives, and Ofloxacin was served as "nitrofurantoin". 285 compounds are served without a structure, with their formula and molecular weight: polymers, mixtures of isomers, and compounds whose structure was certainly wrong with no source giving the right one. Every correction is listed on the new Corrected source values page.
• 1,234 duplicate compounds merged into the compound they duplicated. The old address leads to the kept compound, where its data, names and mixtures now are, and worklists follow.
• 558 values moved to the compound they describe. Data a source gives for one enantiomer or isomer had reached another compound through a mirrored structure in the source: amino acids such as L-alanine and L-valine, limonene, carvone, pinenes, glucose.
• 299 mixture ids retired: mixtures whose records all belong to other compounds once their identity was corrected, for example "D-Alanine + Water", whose measurements are of L-alanine. 282 lead to the mixture that received most of their records; 17, whose records are all set aside, are no longer served.
• 4 compound ids retired, with no substance of their own (a second id of one compound, or a source row naming two substances). They are no longer served.
• 103 source records set aside: records of a substance Cheméo serves under no id (D-tryptophan, levofloxacin, salt hydrates, pages whose name and structure describe two substances).
• 36 source values left out where the source is wrong (a sign error, a value of another compound, a figure later work overturned): ChemSep (13), KDB (10), the NIST Chemistry WebBook (10) and three ChEDL tables (3). The other sources' values for the property stay.
• ChemSep equations stop where they leave physical ground. 362 liquid-side equations stop at the critical temperature (among them 167 vapour pressures and 118 liquid densities), 71 vapour pressures at the critical pressure, and 187 surface tensions before they turn negative. The coefficients are unchanged; each comment gives ChemSep's own range.
• Predictions recomputed on the corrected structures: Joback on 370 compounds, Crippen logP on 414, McGowan volume on 294 and Cheméo Relay on 1,748.
• 102,201 compounds and 18,103 mixtures are served, from 103,439 and 17,462.

Added

• 655 mixtures served for the first time: measurements whose components could not be resolved to one compound each before the corrections.
• The Corrected source values page lists every source value left out, every corrected identity, every record set aside and every retired compound and mixture id, with the reason. The ChemSep data and ChEDL data pages link it.

2026-10-30

Fixed

• Property range searches return the right compounds. A search with no bounds on a property, such as tb:;, disturbed the search index, and later range searches on that property, such as tb:300;400, could return wrong compounds until the next restart. A bound beyond every known value, such as tb:10000;, returned every compound with the property instead of none.
• Image and PDF links with an outdated compound name lead to the image and the PDF again, no longer to the molfile and the Excel file.

2026-10-27

Added

• Data from the ChEDL tables (v27). 16,987 values from nine published tables, collected by the Chemical Engineering Design Library (ChEDL) of Caleb Bell, are now on 9,227 compound pages. Each value cites the publication it comes from:

  • critical properties from the IUPAC series (718 compounds), Mathews (77), PSRK (963) and Passut and Danner (190);
  • melting points from the Jean-Claude Bradley Open Melting Point Dataset (8,861 compounds), triple points from Staveley (182);
  • gas-phase enthalpies of formation from ATcT 1.112 (232);
  • surface tension equations from Jasper (489) and COSTALD parameters (189).

  Like ChemSep values, they carry the compiled marker. The new ChEDL data page lists the tables and how the values are cited.

• 165 new compounds, each with its structure, predictions and a measured melting point (164) or surface tension (1).

• 3,537 more property searches answer, among them 1,152 on the melting point and 238 on the surface tension.

Changed

• ChemSep equation comments say what changed. A ChemSep equation whose range Cheméo stopped at the critical temperature now says "Range stopped at Tc; ChemSep gives it to … K." (66 equations). One cut before the equation turns negative says so with ChemSep's original limit (190 equations). The other ChemSep equations have no comment. The ChemSep data page is updated.
• A new measurement replaces its prediction. The Joback critical pressure gives way on 189 compounds. The Joback liquid viscosity equation is removed on 8 compounds whose measured melting point or critical temperature leaves it no valid range.
• 1,491 Cheméo Relay predictions are now shown, because a new measurement lifts their applicability check: 986 melting points, 162 critical volumes, 141 acentric factors, 88 critical temperatures, 72 critical pressures and 42 enthalpies of formation.
• 300 measured values changed outlier status as the ChEDL values joined the comparison.
• No compound changed identity. Names, structures, formulas, molecular weights and CAS numbers are unchanged for all 103,274 existing compounds.

2026-10-24

Added

• ChemSep pure component data (v26). The ChemSep v8.3 data by H. Kooijman and R. Taylor are now on 542 compound pages: 7,749 constants (critical properties, acentric factor, boiling, melting and triple points, enthalpies and Gibbs energies of formation, and more) and 4,590 temperature-dependent equations (vapour pressure, ideal gas and liquid heat capacity, heat of vaporization, liquid density and viscosity, thermal conductivity, surface tension). Water's ideal gas heat capacity now starts at 50 K. Every value cites ChemSep, and the new ChemSep data page documents how Cheméo's values differ from ChemSep's files: units, equation forms, and the ranges narrowed at the critical temperature or cut before a negative tail. No range was extended.
• Solvent data from SOLV-DB on 165 compounds (1,802 values), and 7 solvents new to Cheméo, and gas data from the Air Liquide Gas Encyclopedia on 73 compounds (553 values). The database build had never read either source.
• 1,038 values from NIST WebBook pages the build had always rejected, mostly pages carrying a table of diatomic-molecule constants.
• 5,444 more property searches answer: compounds are now found by a search on a property they had no value for.

Changed

• A new measured or ChemSep value replaces its prediction. Joback predictions give way on 142 compounds for the critical pressure, 204 for the Gibbs energy of formation, 412 for the ideal gas heat capacity and 333 for the liquid viscosity; Crippen and McGowan values on 154. On 383 compounds a Cheméo Relay prediction is now shown, because a new measurement lifts its applicability check.
• Equations show their source's comment. Opening an equation's details now shows the comment its source attached, such as the constants and review date of NIST's heat capacity equations or a note on a ChemSep range. The PDF and Excel exports carry it too.
• 189 measured values changed outlier status as new values joined the comparison.
• No compound changed identity. Names, structures, formulas, molecular weights and CAS numbers are unchanged for all 103,267 existing compounds.

Fixed

• 7 duplicate copies of the same measured value removed.

2026-10-22

Added

• Heat capacity equations from the NIST WebBook (v25). The critically evaluated Shomate equations of the NIST WebBook (Chase, 1998) are now on the compound pages: 643 gas, 94 liquid and 209 solid temperature ranges. Among them the ideal gas heat capacity of water, nitrogen, ammonia, carbon monoxide, hydrogen sulfide and argon, which Cheméo did not have. Each equation is shown with its coefficients and the range NIST publishes it for: water's starts at 500 K.
• Vapour pressure equations from the NIST WebBook. 1,821 Antoine equations, each with its reference and the temperature range of the fit.
• 16,303 measured values recovered on 6,489 compounds. They had been lost when several WebBook pages, or several rows of one file, for the same compound were merged: 15,357 from the NIST WebBook, 873 from KDB (71 compounds had lost all their KDB data) and 73 water solubilities.
• Vapour pressure can be searched on every compound that has it, including the ones that have it only as an equation: a vapour pressure search now finds 5,548 compounds, against 766.

Changed

• Predicted heat capacity and viscosity are equations on the compound pages too, over the ranges the Joback method was made for, as on the predict page since yesterday. The predicted viscosity says it is for the liquid. Where a predicted heat capacity would be physically impossible, as for O2 and H2, it is no longer shown.
• A new measurement replaces its prediction. Where a compound gained a measured value, the prediction for that property gives way, as for 55 Joback values.
• No compound changed identity. Names, structures, formulas, molecular weights and CAS numbers are exactly as before, for all 103,267 compounds, and the database build now checks that they stay so.

Fixed

• 136 duplicate copies of the same measured value removed in 46 compounds, and one empty vapour pressure equation (benzyl nitrile).

MCP server changes

• A temperature can be sent as a string. t_min and t_max accept "300" or "300 K" as well as 300. An assistant working from an older copy of the tool list sent the window as text and was refused with an internal type name; it now works, and a value that is not a temperature is refused with a message saying what to send.

2026-10-21

Fixed

• Correlations show their real equation. Every correlation on a compound page, in the Excel export and in the PDF was labelled as a vapour pressure equation, and the KDB ones were labelled without their last term, E/T². Each now shows its own equation, all the coefficients it uses (a zero included, it is part of the equation), the unit of the result and its temperature range.

Changed

• A predicted heat capacity comes with its temperature. The predict page showed the ideal gas heat capacity at the boiling point, from a handful of points spread up to the critical temperature, well outside the range the Joback method was made for. It now shows the predicted curve: its value at 298.15 K, the equation, and the range it is valid on, 273 to 1000 K. The predicted liquid viscosity is shown the same way, valid from the melting point to 0.7 Tc. /api/v1/predict returns both as correlations, and no longer lists them as points in predicted.

MCP server changes

• schema_version is now 2. predict_properties returns the predicted heat capacity (cpg) and liquid viscosity (dvisc) in tp_properties, as curves, and no longer in properties. A client that reads them from properties must read tp_properties instead. Everything else below is an addition.
• Correlations are part of the answer. get_compound_properties returns a property's correlations beside its points: the equation, its coefficients at full precision, its temperature range and its source. They come whether or not you asked for the points, because a curve is a few numbers and evaluating it inside its range beats interpolating a table. A property held only as a correlation, such as a vapour pressure known from an Antoine equation, is now returned instead of reported missing.
• A measured curve counts as a measurement. Where a property has a measured correlation, an estimate for it is no longer shown beside it, the same rule as for measured points.
• get_sources counts correlations. A source that provides only correlations is listed, with n_correlations beside n_values.
• A predicted curve stays a curve. predict_properties returns the predicted heat capacity and viscosity in tp_properties, as an equation with its coefficients and validity range, instead of one number averaged across temperatures.
• Large tables can be read window by window. get_compound_properties refuses include_points above 200 points rather than sending part of a table, and the only way to narrow it was the property filter, so water's 690 vapour pressure points were out of reach. t_min and t_max now select a temperature window: every point inside it comes back, and the next window starts where the previous one ended, so a whole table is collected page by page, each point with a temperature exactly once. Each table says how many of its points the window kept, and the refusal now explains how to page instead of pointing to the website.
• Coefficients without float noise. Correlation coefficients are written at 15 significant figures, so 6.360999999999997 arrives as 6.361. The curves move by about one part in 10^14.

2026-10-19

Added

• 3,833 measured points on gas treating with aqueous amines (v24). Removing CO2 and H2S from natural gas and flue gas with amine solutions is one of the most studied processes in chemical engineering, and most of its literature never reached the ThermoML archive Cheméo builds on. 38 papers and theses, from 1976 to 2025, have now been transcribed table by table:
  • 2,934 solubilities of CO2, H2S and methane in aqueous MDEA, DEA, MEA, piperazine, their blends, and MDEA with sulfolane;
  • 222 densities, 89 viscosities and 137 heat capacities of CO2-loaded amine solutions;
  • 170 excess enthalpies of amine and water mixtures;
  • 150 enthalpies of solution and 120 differential heats of absorption of CO2;
  • 11 vapour pressures of pure MDEA.
• On the mixture pages you already use. The data joins the existing mixtures: CO2 + MDEA + water gains 1,136 points and H2S + MDEA + water 449. 16 mixtures are new, among them CO2 + methane + MDEA + water and H2S + DEA + water.
• Solubility is stored as the liquid mole fraction of the gas. The papers report a loading (mol of gas per mol of amine) or a molality. Cheméo converts it at the solvent composition the paper prints, so these values sit on the same basis as the rest of the mixture data. Expect a different number from the one in the paper's table, describing the same measurement.
• Every value cites its paper, by DOI or by the thesis record. Where a paper prints a value wrongly, or the transcription got it wrong, the value was checked against the paper page by page: 35 corrections or removals, each recorded with its page. A value that only looked implausible was removed, never adjusted.

Fixed

• Mixture data is no longer shown twice. Since v19, every mixture page listed each dataset twice, 41,030 duplicates across 17,440 mixtures, so a mixture looked twice as well measured as it is. Each dataset now appears once.
• Mixture links stay valid. Every mixture keeps the address it had before this update, and every rebuild now checks this. The three mixtures that v19 published under two addresses keep both.

2026-08-03

MCP server changes

• An estimate declared out of range no longer carries an error bar. When Cheméo says it cannot estimate the uncertainty on a molecule far outside a model's experience, that number is now gone from the whole answer rather than only from the summary line. It had remained a level down, where a reader looking for it would have found it and believed it.
• Every answer names the version that produced it, with a pointer to this page. Cheméo changes under long-running work, and there was no way to tell from an answer that anything had moved since the last one.
• The similarity score says what it means. Estimates from Cheméo Relay come with how closely the molecule resembles what the model was trained on, and that number reads as a promise about accuracy, which it is not. It says how well the training data covers the structure; the uncertainty says how accurate the estimate is. The answer now says so, once, beside the method.
• Citations point at the paper. Where a method's record carries the DOI of the work it comes from, that is now the link given for it rather than a page describing the method.
• A measured zero is reported. A property whose value is exactly zero came back with the value missing while the counts beside it still said a measurement was there. Propane's dipole moment is zero, because the molecule is symmetric, and that is the expected answer for every symmetric compound rather than an edge case. 80 stored properties were affected. Where Cheméo deliberately reports no representative value, as when measurements straddle zero and their middle would mean nothing, it says so as it always has.
• An out-of-domain estimate reports how far out it is, even at zero. A similarity of zero to everything a model was trained on is the strongest warning available, and it was the one case where the number went missing.

2026-08-02

Changed

• Corrected the Joback group decomposition (v23). Cheméo estimates several properties with the Joback group-contribution method (Joback and Reid, 1987), which breaks a molecule into functional groups and sums a contribution for each. Two groups in that table were defined by the wrong structural pattern: the pattern named "ester" in fact matched a peroxide, and the one named "carboxylic acid" a hydroperoxide. Any molecule carrying an ester or a carboxylic acid was therefore split into the wrong fragments, and every Joback estimate derived from that split was wrong. Aspirin, which carries both groups, had a Joback critical pressure of 4,083 kPa; it is now 3,577 kPa.

• Aligned the Joback boiling-point constant to the 198.2 published in the original paper, from the 198.0 Cheméo was using.

• Which estimates changed. All of these are Joback: ideal gas heat capacity on 72,850 compounds, liquid dynamic viscosity on 36,042, critical pressure on 22,053, enthalpy of fusion on 38,999, and standard Gibbs energy of formation on 2,959. The two curves changed on every compound that has them because Cheméo plots them between Joback endpoints, heat capacity from the boiling point to the critical temperature and viscosity from the melting point to the boiling point, so the corrected boiling point shifts the whole temperature range each is computed over.

• What did not change. No experimental measurement was touched. Cheméo Relay predictions are identical, and Relay is what Cheméo displays for boiling point, melting point and critical temperature, so those are unaffected on the compound page even though Joback's own estimate of them moved. The Wildman-Crippen logP and the McGowan characteristic volume are also unchanged: neither uses Joback. v21 and v22 were internal development databases.

MCP server changes

• A predicted heat capacity now carries its temperature. Properties that vary with temperature or pressure came back as bare numbers, with nothing to say what conditions they applied to. A heat capacity without a temperature is not data. Each predicted point now states its conditions, and each property states the range it covers, the same way measured values always have.
• Predictions say when they are extrapolations. Asked about a molecule unlike anything the model has seen, Cheméo used to answer with the same confidence it brings to a familiar one. It now says so, and how far outside its experience the molecule sits. The number is still returned: when nothing better exists you may well want it, and you can weigh it once you know.
• Predictions state their uncertainty and are rounded to it. A critical temperature whose model error is 33 K is no longer reported to six figures.
• A new list_properties tool. The property keys were not guessable, and the acentric factor being af rather than omega was enough to send a caller down the wrong path. Every key is now listed in a single call that costs no quota, with its unit and whether it is one value or a table.
• A property with no meaningful summary no longer invents one. Some reaction properties pool different reactions, so their values run from strongly negative to strongly positive. Where that happens no representative value is reported, and the reason is stated; the individual values and their range are still there.
• Smaller prediction answers, which leaves more room for the work you are actually doing.
• Better suggestions when a search goes nowhere. A SMILES Cheméo cannot read now points you at searching by name or CAS number instead, and a search that finds nothing points at prediction, but only when what you typed really was a structure.
• The tool now shows what the website shows. Where Cheméo holds both a measurement and an estimate for the same property, the compound page has always shown the measurement alone, and where it holds two estimates it shows the released model rather than the beta one. The tool was showing all of them and reporting the middle value, so a boiling point could come back as the average of a measurement and a neural network estimate, labelled experimental. On 42% of compounds the reported number moves. It now matches the page.

2026-08-01

Changed

• Search results are ranked by relevance. Searching for a compound by name now returns that compound first. Before this, results came back in Cheméo id order, so searching "ethanol" gave 757 matches with Ethanol on none of the first pages. The order is deliberately simple and readable: an exact name or synonym match, then a name that starts with what you typed, then one that contains it as a word, with better characterised compounds first within each.
• An exact match is called out. When what you typed is exactly a compound's name or one of its synonyms, that compound is marked in the results table, even among thousands of candidates. It is the difference between "this scored highest" and "this is the compound you named".
• Every result says how much data Cheméo holds for it. A new Data column counts the properties on each compound, so you can tell at a glance which of several candidates is worth opening.
• Searching by structure and by formula is exact again. Case carries meaning in chemical notation, and Cheméo was losing it: Co (cobalt) and CO (carbon monoxide) were treated as the same thing, as were the aromatic and aliphatic forms of a SMILES, so a benzene structure search could return cyclohexane. They are now distinct. Formulas Cheméo previously did not recognise as formulas, including AgCl, SbCl5 and SiF4, are recognised, and you can search by InChI.

MCP server changes

• The beta caveat about ranking is gone, because the reason for it is. The search tool reports ordering: "relevance", carries the exact match as its own field, and no longer advises searching by CAS or SMILES to work around the result order.
• Two new search options: exact, which returns only a whole-name match and returns nothing rather than falling back to a fuzzy search, and has_cas, which drops compounds Cheméo holds no CAS number for.

2026-07-30

New

• An MCP server, in beta. Cheméo now speaks the Model Context Protocol, so an AI assistant can look up property data directly instead of reading the website. Connect it at https://www.chemeo.com/api/mcp. You sign in and approve the connection yourself, the access is read only, and you can disconnect any application at any time from your profile.
• Four tools. Search for compounds, read the full property set for up to 25 of them at once, ask where a specific value came from, and run a property prediction from a SMILES string.
• Answers you can check. Every value says whether it is an experimental measurement or a prediction, how many measurements and how many independent sources back it, the spread between them, and how many were excluded as outliers. Every result carries the citation, and where a value names an original publication it says to cite that ahead of Cheméo. A property Cheméo does not hold is stated outright rather than left as a gap.
• Beta means the tools and their answers may still change. (Search results are ranked by relevance as of 2026-08-01; when this was written they were not.)

2026-07-26

Added

• 4,672 recommended liquid heat-capacity points across 376 compounds (v19). 3,279 isobaric liquid heat capacity and 1,393 saturation heat capacity. Each is a critically-reviewed recommended value that carries the source citation and the monograph table reference.
• Source: Zabransky, M., Ruzicka, V., Majer, V. and Domalski, E. (1997), Heat Capacity of Liquids: Critical Review and Recommended Values, Monograph No. 6, J. Phys. & Chem. Ref. Data (JPCRD), NIST, Gaithersburg, MD.

2026-07-19

New

• A bigger database (v18). Cheméo now covers more than 103,000 compounds and 17,400 mixtures, about 940 compounds and 1,200 mixtures more than before, from rebuilding the whole database against the current source data.
• More measured data. Thousands of added experimental values, especially phase-transition points: over 6,000 more boiling points and nearly 3,000 more melting points, plus more critical temperatures and enthalpies of vaporization. New temperature and pressure dependent property types are included too, such as saturation heat capacity and isothermal compressibility.

Changed

• Predicted values you can rely on. A predicted property is now shown only when an experimentally measured compound sits near it in chemical structure space. Predictions that fall outside the models' validated range are no longer shown as numbers. Instead the compound page points you to the prediction tool, which still computes them on demand. The aim is fewer numbers, and more trustworthy ones.

Improved

• Stereoisomers stay distinct. cis/trans and alpha/beta forms are kept as separate compounds instead of being merged into a single entry.
• More structures kept. Compounds whose structure our chemistry toolkit cannot build (some organometallics, ions, and noble-gas dimers) are now retained with their measured data rather than dropped.

2026-07-16

New

• Search for mixtures by their components. A search like "methanol water" now finds the mixtures that contain both, alongside the pure compounds. Component synonyms are matched too, so "methanol" finds mixtures listed under "Methyl Alcohol". Mixtures appear in their own section on the results page, each linking to its mixture page.

Improved

• Faster "similar compounds". The list of similar compounds on every compound page is computed noticeably faster.
• Worklist checks entries. Adding a compound or mixture to a worklist now confirms it exists first, and each list has a size limit.
• Style and script updates apply right away. After an update you no longer need to force-refresh the page to get the latest styling or behaviour.

2026-07-15

Changed

• Updated property database (v17). Predicted values are now stored next to the experimental data for the same property, so parity plots are generated near instantly in the prediction tool. Displayed averages and ranges continue to use the experimental data.

API

• Request rate limits. The public API now allows up to 120 requests per minute, with short bursts of up to 30, and reports the current limit in standard RateLimit response headers so clients can pace themselves.

2026-07-14

Changed

• A refreshed look. Cheméo has a cleaner, modern design: refreshed styling throughout, clearer and easier-to-read property tables, crisp icons, and a layout that makes better use of wide screens.