I want to know whether or not PEG-40 Hydrogenated Castor Oil can really solubilise Cetyl Alcohol. I read a member here asking if he/she can make their own Emulsifying Wax with Polysorbate 80/20 and Cetearyl Alcohol. Another member says commercial one, its ratio is either 1:3 or 1:2 (Polysorbate 60:Fatty Alcohol).

Sadly, I have neither Polysorbate nor Cetearyl Alcohol. I have only PEG-40 HCO and Cetyl Alcohol. I am just a DIYer, hence my materials are extremely limited. I hope to work with what I have rather than buying new chemicals.

I have problem working out the ratios in percentages as Cetearyl Alcohol is a mixture. Thus, I did a few samples of varying percentages.

1%  PEG-40 HCO and 3% Cetyl Alcohol (water q.s too 100%)
2%  PEG-40 HCO and 3% Cetyl Alcohol (water q.s too 100%)
3%  PEG-40 HCO and 3% Cetyl Alcohol (water q.s too 100%)

All failed. I still see tiny white bits of Cetyl Alcohol. The bits are kind of soft scrubs, slightly rough to the touch.

I try not to have too much PEG-40 HCO because it really can make a product draggy, very draggy, and can make skin shiny. Can be tacky too.

How much PEG-40 HCO is needed to fully and properly solubilize how much Cetyl Alcohol without the end product making skin shine like oozing oil, without adding more drag, and without adding more and more chemicals merely to mitigate each chemical's overpowering weaknesses? 

Will DATEM work to emulsify Cetyl Alcohol? (Diacetyl Tartaric Acid Ester of Mono- and Diglycerides. E number is 472e) Yes, a baking ingredient bought at a baking supply shop!  :D Inexpensive and easily accessible, how can I complain! On its own, it gives skin a very very dry feel, although not physically dry. Deposits lipid at the same time not greasy is the power of an 'ester', perhaps. I have not tried it in a combination of other stuff, yet. Maybe with other things DATEM will not be this horribly dry.

I understand that you would suggest, highly advise, or introduce me to other more chemicals than PEG-40 HCO to emulsify Cetyl Alcohol. As said, I do my best to work with what I have at present. I already have quite many chemicals which I incidentally 'collected' over the years, I bought only 100g and they are like unlimited! So, you see how little I use and make things for my own use? It is a waste of money (most of them are not cheap. I live in Asia...this is the reason why!), and since it is only for myself it is all right that I get skin problems by using expired chemicals; no one sues me.  :D


  • PEG-40 HCO is not used as a sole emulsifier. Are you trying to make your version of polawax? Have you tried searching ingredients on alibaba? Must be easily accessible in Asia.
  • @ngarayeva001

    Oh no. I am not trying to imitate any products. I want to solubilize Cetyl Alcohol using what I already have.

    I have been dealing with China sellers for many years, and they are not really honest. I cannot be a racist when I am a Chinese!  :lol: 

    Above all, most Alibaba sellers have really high MOQ. The shipping fee alone is OMFAG! Even if they could sell me less than 1kg the shipping fee is still the same.

    Here is my update, what I tested this morning:

    a. 3% Cetyl Alcohol, 6% PEG-40 HCO, 20% PG, 1% DATEM. Success!

    I took DATEM out and...

    b. 3% Cetyl Alcohol, 6% PEG-40 HCO, 20% PG. Success!

    6% PEG-40 HCO is too much. DATEM is not necessary. Hence, I...

    c. 3% Cetyl Alcohol, 3% PEG-40 HCO, 20% PG. Success! Somewhat. Bits of Cetyl Alcohol show.

    (I am not truly sure why I must have Propylene Glycol added to all hydrophobic substances. I 'feel' that it helps with the dissolution. As for Salicylic Acid and Menthol, PG 100% works, I see those things 'melt' without external heat)

    Maybe 4.5% PEG-40 HCO would work. Slightly more than 3% to see if the Cetyl Alcohol bits are gone.

    I hope I could reduce PEG-40 HCO if 0.3% Xanthan Gum is added. I previously tried 0.3% Xanthan Gum and 3% Cetyl Alcohol, there are the bits, I forgot that Cetyl Alcohol is a solid, and that is when EMULSIFIER yelled loudly in my head.

    I also tried Cocamidopropyl Betaine. It did not look like it work. It would be marvelous if it works as it is not tacky. Maybe it would be tacky if it is used too much for the sake of solubilizing Cetyl Alcohol.
  • Cocamidopropyl Betaine is a detergent. It’s used in shampoos and shower gels. 
    I still can’t understand what are you trying to achieve. Are you trying to make an emulsion with cetyl alcohol? If yes just heat the phases. However I don’t think that emulsion based on PEG-40 HCO will be stable. It’s used for achieving micro-emulsions with low % of oil. Such as solubilizing 0.5% of fragrance in a clear solution.
  • I think you are correct. A little lipid needs A LOT of PEG-40 HCO! Not suitable for normal use. If it could be used as normal then it would be famous. PEG-40 HCO basically has zero practicality because there is very little information about it on the Internet. Imagine, a very old technology but the marketing for it is so low. But the information of other old technologies are aplenty.

    I eventually drop the thought of using any lipids because they make me "sweat". I do not know how to describe this phenomenon. I guess it has something to do with occlusiveness. MCT oil or Caprylic/Capric Triglycerides seem to be okay. My skin is probably suited to very very light moisturizer, and probably best not even the slightest presence of lipid. I added lipids because I learnt that we need a little of them regardless of our skin types. It appears 'it depends', there are exceptions to the rules.

    Xanthan Gum seems to be working very well at suspending a little oil (Sunflower oil), under some blending with my mini battery-operated blender. This is only for testing, I wanted to see how Xanthan Gum fares as a "natural" suspending agent. Despite of Xanthan Gum has horrifying aesthetics (because the easiest and the cheapest source  for me to obtain stuff is at the bakery supply) it is excellent as a suspending agent at very tiny amount!

    Sadly, Xanthan Gum is not a gelling kind. I read somewhere that Carbomer's ultra sensitivity towards salts could be mitigated by adding Xanthan Gum. Is this true? Anyone here tried this combination and can attest the fact that it works that way? (The most common is Carbopol 940 and its equivalent Sumitomo Seika HV-505HC. Identical weakness and strength)

    I also read that Carrageenan mixed with Xanthan Gum creates soft gel. Carrageenan will gel but Xanthan Gum retains the liquid side so that the end product will not be unspreadable. Anyone here tried this as well?
  • What exactly  are you trying to make? Every ingredient has a purpose. PEG-40 HCO is a solubiliser. It’s used to solubilise tiny amount of oil (such as fragrance) into a clear system (microemulsion). It shouldn’t be used as an emulsifier. Xanthan gum is a water phase thickener. It shouldn’t be used as an emulsifier either.
  • Yes. I am very well aware of Xanthan Gum, Cetyl Alcohol, and others, are NOT an emulsifier despite of what the Internet says. Many myths refuse to die

    I had an old formula which is perfect. Perfect for my climate and skin, that is. Until recently I read an article by Evonik that cationic surfactant is much better than anionic surfactant in terms of the 'dry feel'.

    I thought the dry/velvety/powdery feel is what I need, suited to my skin and the climate here. Little did I know both Cetyl Alcohol and Behentrimonium are "big" lipids. MCT or Caprylic/Capric Triglicerides seem to be all right on me (in very small quantity), although it still behaves a typical oil (give skin the shine).

    My actual purpose is to make my existing moisturize a little stiff or gel-like, a 'thing' that can be lifted by finger. I am not sure what the terminology is. It is like cream, you can pick it up with your finger and will not drip like water. Carbomer is the best description.

    The only thing I know best is Carbomer, excellent suspending power, it gels but miraculously light, excellent yield value, due to its extremely low concentration needed it does not leave residue and not tacky. Problem is my formula contains salt. I was given a small sample of Carbomer to try out, true enough a few grains of Sodium Chloride or a few drops of Sodium Lactate destabilizes the polymeric network. It looked like a joke to me and I was new to the chemical wondering what the heck was going on.

    After I did my own research only to find out that Carbomer is "designed" to disintegrate with the bit of salts on skin, the purpose is to release all the actives quickly. That instantaneously made sense to me as to why Carbomer is ultra sensitive to very very little electrolytes. I contacted Lubrizol and Sumitomo Seika, they said I need the Ultrez range, and SER W-300C. Anything out of the regular Carbomer (namely Carbopol 940) does not exist here.

  • I see, you want to achieve higher viscosity without adding greasiness. You can replace Cetyl Alcohol to Behenyl Alcohol. It will add viscosity and it’s very ‘dry’. See if you can find Sepimax Zen. It’s a very versatile ingredient. It acts as an emulsifier and rheology modifier (you can make a clear gel with it) and it’s relatively resistant to electrolytes (it won’t tolerate 2% of sodium lactate but it’s more resistant than carbomers). You can also replace caprylic/capric to isopropyl myristate or isododecane to achieve dryer feel.
  • Sepimax Zen is by Seppic. Regarding ultrez, the most electrolyte resistant according to Lubrizol’s tables is Ultrez 30. I don’t like it. It’s better than 980  but I wouldn’t call it electrolyte resistant.
  • Hey! I agree about the Ultrez! Looking at their brochure I was like....How can that be constituted as electrolyte resistant. Like you mentioned, Ultrez is more resistant than Carbomer but the level of resistance is a joke. I bet it is another marketing. So yes, I hate to say it but I do agree that there are better things than Ultrez 20, 21, or 30.

    Whoa, that are some new chemicals I must purchase! I try to not confuse you as I know the way I write is too much as if stories, and I am excited. You are the only one entertaining me, better than none!

    I can get Isopropyl Myristate. This is inexpensive and easily accessible.

    I can get Isododecane. It is expensive, probably due to 'green/eco' status.

    I cannot get Behenyl Alcohol.

    I thought Isododecane is a replacement of Cyclopentasiloxane. Now that we are in this topic, I have Cyclopentasiloxane, and I bought Caprylic/Capric Triglycerides.

    Here is the thing....I understood that CCT is not susceptible to high temperature as volatile silicone. I live in a tropical climate, temperature can go to as high as 36°C, average temperature is 31°C.

    I contacted Tony O’Lenick, the man who wrote "Dry Skin Feel in Cosmetic Products Volatile or Non-Volatile".

    He sent me a presentation file showing evaporation rates of a few volatile silicone at 3 temperatures:

    -22°C (room temp)
    - 33°C
    - 37°C (human body temp)

    Cyclopentasiloxane doesn't look good above 22°C, it already begins to evaporate even at 22°C. Like Carbomer, I think it is deliberately designed to be ultra sensitive to certain stimuli and vanish quickly. Having said that, products have not much issue in temperate countries due to the low temperature. In tropical countries however, products boil within containers, figuratively speaking. On a cool day over here, Behentrimonium and Cetyl Alcohol is firm, on a hot day they are a little watery. Carbomer is insanely stable in high temperature, it does not even melt with fire directed at it! (Oh yeah I experiment with all kinds of nonsense!)

    And because I do not use a vacuum/airless bottle, I can safely presume that Cyclopentasiloxane evaporates filling up the headspace, and readily escapes as soon as the container is open. Cyclopentasiloxane is not cheap either is the reason why I am stingy. Coincidentally Isododecane is also as volatile as Cyclopentasiloxane.

    Sigh. Sepimax Zen is out of my reach.
    I found a seller here selling some thickeners. Clarity and eco do not matter. Getting the right one is already a heck of a challenge, let alone the perfect all-rounder.

    1. Polyacrylamide, C13-14 Isoparaffin, Laureth-7

    I think is Sepigel 305.

    2. Acrylates Copolymer

    I do not know whose this belong to, or similar to whose product. Acrylates Copolymer may be overly general.

    Oh no! Sepigel 305 is no good! It is also very salt sensitive! I guess the other one (Acrylates Copolymer) is also very salt sensitive.

    I forgot to mention that the person at Lubrizol mentioned that Carbomer and other thickeners (cellulosic or polysacharride) work together. He said something about competing for water. Is it true? Have you tried this? Might be a rhetorical question, I should know that most people here use commercially one-size-fits-all chemical do achieve the same thing DIYer painfully try to achieve either money, quantity, or accessibility issues.

    Competing for water does not explain how other thickeners magically make Carbomer salt tolerant. He also did not explain tolerate salt by how much. I can't blame Lubrizol/them/him for not knowing because seriously makes no sense why go through all these trouble when they already produce and can use a product that is salt tolerant. :D  

  • Cyclomethicone works well in hair products where it improves spreadability and in foundations. Every ingredient has its purpose and the best application.
    Post your formula if it's ok with you and I will try to think what can be amended to make it dryer. 
    Frankly it's very hard to say anything without seeing the formula.
  • DoreenDoreen Member
    edited May 2019
    I'm about to try Aristoflex Silk, it's said to have great electrolyte tolerance and sensorials. I hope it's even less tacky than Sepimax Zen.

    Re: Ultrez 30. It has a reasonable tolerance, you just shouldn't add high levels of electrolytes. I never have problems with it.
    No polymer is totally electrolyte resistant of course.

    I tried to upload some documents here (regarding carbomers etc) but the file sizes are too large. :/

  • Oh yes. My 'original' formula is as follows:

    Urea 20.000 %
    Propanediol 20.000 %
    GdL 5.000 %
    PQ-7 (~9.5% active) 2.000 %
    NaHCO3 1.127 %
    Sodium benzoate 0.200 %
    Water q.s
    Salicylic Acid 2% (Sometimes it's added. Sometimes none)

    Basic and simple, but works great. It has zero lipid that leaves skin looking like nothing is put on. Does not make skin glow like Korean kind of glow. Not particularly dry to the touch and does not mattify skin, but excellent hydration. As for skin feel, it leaves some kind of a covering, probably is the work of Polyquaternium-7 and Propanediol, but nice hydrated feeling.

    Downside is it does not spread well. I have to add a little water every time before applying on my skin. And it drips as you can there is no thickener.

    Here is what I tried to increase the slip/spread:

    a) Increased PQ-7 to 6%. But it did not help. PQ-7 by itself even at 0.5% is extremely slippery. I think its slipperiness is limited to other ingredients in the mix.

    b) Increased Propanediol to 30%. It does give lots of play time. Maybe too much play time. Not sure why the two sides of the extremes. Maybe 25% is the sweet spot. I tried Propylene Glycol of the same concentrations, same results are acquired. I have no problem nor sensitivity towards PG or PDO, but I do not think I want them that much in my formula. They are there because they are superior to Glycerin/Glycerol in many ways and that's for sure.

    c) Added Cyclopentasiloxane. Which later Xanthan Gum, Behentrimonium Chloride, And Cetyl Alcohol are also added for the sake of suspending Cyclopentasiloxane. Marvelously glide upon application and is cream-gel-like easy for finger to pick it up. However, evaporation and temperature became new issues. This option is not good and the resulting cost can be be very high and a great wastage considering Cyclopentasiloxane cannot be kept properly in this high temperature and without airless pump. As mentioned before, Behentrionium and Cetyl Alcohol make me "sweat", I assume they are too rich for me due to their very long carbon chain.

    One of the ideas I had is the use of fumed silica (Aerosil 200). Reading Aerosil 200 data, I understood that it is can hydrophilic so it will not thicken or make water base product gel-like.

    I have trouble finding Iota Carrageenan. I guess commonly found Carrageenan is Kappa type. There are a few sellers here selling Carrageenan, however they do not state which type. I enquired two of them, they got defensive. Few won't tell and ignored me. One of them provided me with false data and CoA thinking that all buyers are completely stupid.

    Konjac is as difficult to find as some of the materials you mentioned. I found one today and minimum purchase is 1kg.
  • DoreenDoreen Member
    Cyclopentasiloxane doesn't need airless packaging on itself, neither the pure product nor if used in cosmetics, it's not as extremely volatile as you think it is. With a boiling point of 210ºC and vapour pressure of 33.2 Pa it's not that bad. The amount that evaporates in your product, when stored at room temperature, really is negligible.
  • 40% of humectants? Why?
  • @Doreen

    How much actually is 33.2 Pa water pressure? I live in a tropical country, temperature can go to as high as 36°C, average temperature is 31°C. Our "room temperature" is 31°C, it is 10°C higher than the conventional 21°C!

    The pure Cyclopentasiloxane is in its original packaging. No problem with it that I find because I poured a little into a dropper bottle to further minimize lost due to frequent opening and closing of the container. But I cannot say the same for finished product.


    I knew you would ask me that! I actually wrote the reason why but I saw my "essay" was getting longer and longer, thus I delete it.

    20% Propanediol to replace Glycerin. Propanediol is superior to Glycerin in many ways, it is not tacky and just nice on me. I tried with 10% Propanediol and experienced not much difference, a little less hydrating. Also to prevent Urea from recrystallizing upon water evaporation. This is one of the reasons why Urea is almost always mixed with petroleum jelly or some very rich and thick lipids with very little to zero water.

    20% Urea is a bit high, I know. It works for me the best. I use the moisturizer for all body parts regardless. My shins, forearms, and fingers are much drier than the rest of the body. It also does not make my 'oily' face shine nor aggravates my skin in anyway.

    I tried Sodium Hyaluronate and Pentavitin. These EXTREMELY expensive substances are no match for inexpensive Urea that is tried and true for more than few hundred years! What can I say...I was like many people, when beginning making products easily influenced by miraculous claims and colourful brochures, green, eco, and nonsense!
  • Your "moisturiser" isn't an emulsion. It's a toner with 40% of humectants. Isn't it easier to make a lightweight emulsion with light esters and higher % of humectants than is usually used? You are wasting ingredients in my opinion. Skin needs 1) humectants 2) emollients and 3) occlusive agents. And they must be balanced. 
  • Yes I know that my moisturiser is not an emulsion but it is still a moisturiser nonetheless, and it works to hydrate my skin, slightly softens scar and flaky skin very well.

    Lotion/cream traditionally refers to an emulsion, which is also the reason why I never mention anything else about my moisturiser other than 'moisturiser'. Not all moisturisers must be an emulsion. It is known that if you use dimethicone or Caprylic/Capric Triglycerides you can label your product as "oil-less" and still call it lotion/cream.

     Its definition has been blurred. 

    "This is one problem that hasn't suffered from lack of attention: there are dozens of creams and lotions for dry skin. They are sold as moisturizers, which is more of a marketing term than a medical or scientific one"

    Yes, I can make a lightweight emulsion with light esters. I can make anything I want to. Problem is not many things I can easily get due to material availability, selling quantity, and price since I am not selling product to get back the money. Otherwise I would not be here looking for possible alternative solutions and using some ingredients from bakery supply. Pathetic! :lol:

    Not really wasteful. I purchased Propanediol and Urea rather inexpensively. I may eventually use Propylene Glycol as it is even cheaper than Propanediol.

    There must be MEC or Minimum Effective Concentration.

    I hope I made sense. 
  • DoreenDoreen Member
    Not water pressure, but vapour pressure. You can read its exact definition in this link, it's an indication of a liquid's evaporation rate. The 'Pa' stands for 'Pascal', this is a unit of pressure (one newton per square meter). Vapour pressure is sometimes also expressed in other units, like millimeters of mercury (mmHg), or kilopascal (kPa=1000 Pa).

    Do you mean 31°C ambient temperature outside or inside your house, where the cyclopentasiloxane is stored?
  • DoreenDoreen Member
    edited May 2019
    Simply said: the higher the vapour pressure and the lower the boiling point, the more volatile the substance is.
    For example chloromethane (although a gas at room temp, wrong example maybe) has a vapour pressure of 490.000 Pa (20°C) and a boiling point of -24.2°C.

    Edit: typo
  • GuntherGunther Member
    However I don’t think that emulsion based on PEG-40 HCO will be stable. It’s used for achieving micro-emulsions with low % of oil. Such as solubilizing 0.5% of fragrance in a clear solution.
    By the way
    What's a good PEG-40 HCO to fragrance ratio?
  • AzizAziz Member
    edited May 2019
    Gunther said:
    By the way
    What's a good PEG-40 HCO to fragrance ratio?
    Here you will get a chart for diffrent oils and fragrances . 
  • I am afraid the table in the link shared by Aziz is overly optimistic. I would say that lavender is 2.5 to 3. And it can vary as EOs are not very consistent. Unfortunately there’s no straightforward answer.
  • Just a clarification, I am talking about clear solution. If clarity isn’t an issue it’s not as high.
  • Bill_TogeBill_Toge Member, Professional Chemist
    edited May 2019
    further to @Doreen's posts, atmospheric pressure is around 100,000 Pa at sea level, so anything with a vapour pressure of 33 Pa is non-volatile
    for comparison, water has a vapour pressure of around 4,000 Pa at 30 °C, around 20,000 Pa at 60 °C, around 47,000 Pa at 80 °C, around 70,000 Pa at 90 °C, and 101,300 Pa at 100 °C, where its vapour pressure equals the atmospheric pressure and it boils
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • @Bill_Toge ;

    OMG! I love examples! Yes, I 'got it'! Still a little hazy but I got it.


    Shite! I didn't know why I typed wrongly! Seriously, as I read aloud I incidentally say water pressure!

    I got an excellent explanation of vapor pressure. For idiots. Love that step by step approach to imagination. I am a visual kind of person. Certainly some knowledge in physics helps, otherwise people like my parents never understand the slightest!

    31°C ambient temperature inside my house. Sometimes in and outside the house are of the same temperature, true on cooler days.

    33.2 Pa / 0.2490212 mmHg at 25.00°C (Cyclopentasiloxane). How does Clyclopentasiloxane fare at 31°C? Is there a calculation? 

    The only calculator I found is only for water. Bill's examples are apt.

    I am not sure if this image helps me to understand.

    I assume Cyclopentasiloxane of all brands are the same. Thus, looking at the graph, Cyclopentasiloxane appears to be less volatile. Very much less volatile compared to water. When water is boiling Cyclopentasiloxane is only half way there. I hope I am correct.

    I need not worry about headspace of the container then? I do not know how much Cyclopentasiloxane is escaped (gas state filling up the gap) considering the temperature is here 10°C higher than that of in temperate climate.

    Temperature seems to be the biggest enemy when comes to heat-sensitive things. We cannot put butter on a table and still see it as solid, coconut oil here is liquid, what seems to be 'saturated' for you is 'unsaturated' for me. Unless Carbomer is used, stable emulsion (or not emulsion) is not really stable.

    Talking about Carbomer, assuming I need not worry about Cyclopentasiloxane evaporation and that is fills up the headspace of bottle ends up as wastage and inefficiency (less or no spreading) during application, I then can use Xanthan Gum as the suspending agent with Cyclopentasiloxane. Maybe, just maybe, Xanthan Gum could encapsulate Cyclopentasiloxane significantly containing it and none shall escape regardless of the temperatures. I understood that Xanthan Gum is resistant to many external insults, bacterial power. Please tell me if this is a wishful thinking!
  • Bill_TogeBill_Toge Member, Professional Chemist
    there is a way to calculate how the vapour pressure of a given substance varies with temperature, namely the Clausius-Clapeyron equation - it's equation (2) on this page
    if you substitute P1 = 33.2 Pa at T1 = 298 K (25 °C) and P2 = 101,325 Pa at T2 = 483 K (210 °C), you can work out ΔHvap/R and thereby calculate the pressure when T = 304 K (31 °C)

    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • I was carried away once again. I forgot that Xanthan Gum does not gel. I am trying to get Carrageenan.

    This page does not help me much, lots of symbols. However "Clausius-Clapeyron equation" helps! With that name I found this one

    P1 = 33.2 Pa
    T1 = 298 K (25 °C)

    P2 = 101,325 Pa
    T2 = 483 K (210 °C)

    ΔvapHm = 51942 J/mole OR 52 KJ/mole. There is no "R".

    This one produces nearly identical result but the result is ΔHvap instead of ΔvapHm or ΔHvap/R. "R" here is fixed.

    This equation looks very different to the other two. "R" here automatically appears.

    Now that I have ΔvapHm = 51942 J/mole OR 52 KJ/mole, where do I input T = 304 K (31 °C)?

    How very interesting! With this new knowledge I could extrapolate to other substances!
  • Bill_TogeBill_Toge Member, Professional Chemist
    edited May 2019
    ln(33.2 ÷ 101325) = ΔHvap/R × (1/483 - 1/298)
    hence, ΔHvap/R = ln(33.2 ÷ 101325) ÷ (1/483 - 1/298) = 6242.486494...
    let P304 be the vapour pressure at 304 K, then:
    ln(33.2 ÷ P304) = ΔHvap/R × (1/304 - 1/298) = -0.413446...
    hence, (33.2 ÷ P304) = exp(-0.413446...) = 0.661367...
    hence, (P304 ÷ 33.2) = 1 / 0.661367... = 1.512020...
    hence, P304 = 33.2 × 1.512020... = 50.2 Pa

    (as an aside, I really wish there were a proper way to format equations in HTML)
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • And I wish my built-in Microsoft scientific calculator could do more. I thought my eyes were problematic because I could not get the same answers as yours. I had to use an online calculator; there is no 'In' in the Microsoft scientific calculator.

    The steps to calculating vapour pressure at a given temperature is emphatically not a jest. You made it look simple and easy. I will try to use Google Spreadsheet to help me do the automated calculations and I need to only punch in the values.

    'P304' does not refer to Cyclopentasiloxane? It is actually P-Code to mean inhale? P304 applies to any substances that evaporates?

  • Bill_TogeBill_Toge Member, Professional Chemist
    edited May 2019
    "let P304 be the vapour pressure [of cyclopentasiloxane] at 304 K"
    I'd normally put 304 in a subscript, but the 'sub' tag doesn't seem to work on this board
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
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