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 on: Today at 06:19:41 AM 
Started by juul - Last post by Enthalpy
I hadn't found quickly a mixture of water and antifreeze that melts at -80°C. Not propylene glycol, not ethylene glycol, not erythritol, not glycerol, but possibly a mixture of several glycols in water, remembering that ethylene glycol is a bit toxic. Nasa's attempts were possibly in this direction, rather than an alkane, if they sought compatibility with polyethylene.

Besides water and alcohols, alkanes offer a big fusion heat, fluoroalkanes less so. They are not always compatible with polyethyleneS and polypropyleneS, but with other usual plastics they are. Non-flammable criterium suggests the molecule shall be bigger than 2,6-dimethyloctane, and melting point criterium tells it must be branched.

Farnesane is a first idea
bp=+243°C mp<-71°C fp+109°C wow, so it does burn with a wick or as a mist, but matches won't light a leak on concrete. Other sources tell mp around -100°C. Farnesane makes 99,76% of the AMD-200 fuel attempt by Amyris, where many kg were produced. My feeling is that the company meanwhile targeted easier markets than jet fuels.
BEWARE the syntheses I suggest in the linked threads are NOT tried and I'm no chemist, so they can be complete cr*p.

2,4,6-trimethyl-dodecane has phase-change properties similar to farnesane. It seems rare too.

Unless a company like Amyris decide to produce these compounds, they are expensive lab rarities, so synthesising would be cheaper. And if you produce such an alkane, other uses and customers await you.

JP-10 is mass-produced
it melts at -79°C from NIST (Chickos et al is doubtful), and its flash point is very little above +55°C. Its kerosene smell can be misleading.

Grafting an alkane tail to cheap myrcene, then saturating everything, could be a flexible design, as the tail's length adjusts the melting point. Here myrcene

Do not believe melting points in general. Measures are rare, most values are software estimates, but these fail grossly on melting points.

 on: Today at 05:07:12 AM 
Started by wicked123 - Last post by wicked123
Hello, when dissolving [CrCl2(H2O)4]Cl.2H2O in HCl and water, why do we heat to 60°C? What happens if we heat to a temperature above that?

Thank you

 on: Today at 04:35:50 AM 
Started by becchino - Last post by Mitch
I guess you could dissolve it in water and try using a urea indicator strip like these:

 on: Today at 03:58:36 AM 
Started by MargaaMarius - Last post by Borek
Determining nitrates by titration is not trivial. Try to google for "determination of nitrates in water" - the easiest method I can think of is to use strips, but their accuracy is rather low.

 on: Today at 03:50:58 AM 
Started by becchino - Last post by becchino

Hi everyone. I immediately expose the problem to you.
I found a stain inside a product. It looks like urine.
Do you know a method to make a qualitative analysis?
A reagent, a kit.
Thanks a lot.

 on: Today at 03:13:41 AM 
Started by oilypiggy - Last post by mjc123
Are you confusing molecular geometry with electron-domain geometry?

 on: Today at 12:56:46 AM 
Started by Craig65 - Last post by AWK
4.25, 100, 80
How many significant digits you should use in the final result (remember about rounding rules)?

 on: Today at 12:07:04 AM 
Started by Al3x2012 - Last post by MargaaMarius
We've just done the same, but we only used strong acids/bases as titrants. When you use strong titrants, the equivalence point is when the amount of tirtant you have used equal the amount of acid/base in the sample before you did the titration. So let's say that you used 20 mL 0,1 mol/L NaOH to get the equivalence point. 0,020L * 0,1mol/L = 0,002 mol. You had 0,002 mol acid in your sample. Let's say the sample size was 10mL, then the concentration was 0,002mol/L / 0,010 L = 0,2 mol/L.

 on: Yesterday at 11:58:54 PM 
Started by MargaaMarius - Last post by MargaaMarius
Disclaimer: English isn't my first language, and not the one I'm learing chemistry in, so I have no idea if my terminology is correct, since I've only learnt the terms in norwegian. If any words are wrong, please ask in a comment so I can try to explain what I mean and maybe even learn that the proper term is in english

For a school project, we are supposed to write about if/how agriculture has affects nearby water sources. After some googling, we decided to measure pH,  bacteria and nitrates,  as these seemed most relevant. We have an idea of how we are going to measure pH and bacteria, but have some questions regarding finding the concentration of nitrates. Is it ok to use titration? We've done this a couple of times already, when working with acids and bases, so titration would be a method we are familiar with. But what should we use as indicator and titrant? Or is there some other, better method?

 on: Yesterday at 11:55:47 PM 
Started by Craig65 - Last post by Craig65
therefore 100grams of Benzene = 1.2802156497658 * 4.25mj * .8 = 4.35273320920372 mj ?

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