azeotropes

On 8/23/12 this once one man band, now fully staffed, Dogbreth brought some great Arizonan pop punk with folk punk elements to Davis, CA, reminiscent of their fellow statesmen Andrew Jackson Jihad, but with some more power pop riffage.

Dragons also provided some rad, mellow, folky, poppy jams from Arizona.

Davis’ own Young Mings played their second to last show this night.  They played a variety of pop/post punk, best likened to earlier Nick Cave, but with a more contemporary use of effects.

Finally Azeotropes is a one man pop punk/power pop machine that sounds like some sort of lofi bridge between the Toy Dolls and Green Day.

Azeotropic water removal from a reaction mixture with a Dean-Stark trap.

Azeotrope is a mixture of two compounds in a specific ratio what boils lower than each of the two solvents. Why is this good? I have a solution in benzene with a little water and water has a boiling point at 100 °C, while benzene boils at 80,1 °C. If I would like to remove the water by distillation, the normal method would be to distill first the benzene, than the water, since the benzene has a lower boiling point. But luckily these two forms an azeotrope mixture what boils at 69,3 °C what is lower than the benzene and the water separately. So with this I could distill the water out from the benzene under the boiling point of these two an because this two solvents are unmiscrible, I could easily separate them from each other.

Interesting fact: absolute ethanol was made by adding benzene to 95,5 % ethanol (what is also an azeotrope mixture with water) and they distilled out the remaining water with benzene, than distilled the remaining excess benzene too. Luckily now they use the non toxic cyclohexane instead of the benzene. 

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Ethanol (alcohol, spirits) C2H5OH

  • Appearance: Colorless liquid
  • Molar Mass: 46.07 g/mol
  • Density: 0.789 g/cm3
  • Melting Point: -114°C
  • Boiling Point: 78°C
  • pKa: 15.9

Ethanol is a primary, two carbon alcohol. It’s more famously known as “grain alcohol” or “spirits”. It’s a psychoactive drug, acting as a depressant on the central nervous system. It’s used in sanitation such as medical wipes, like other alcohols. Ethanol is also used as a solvent, and is miscible with water. This can be an issue as it forms an azeotrope (96% EtOH and 4% water) which makes it difficult to obtain 100% pure ethanol. A well known way to obtain ethanol is by the fermentation of sugars and also by distilling the fermented sugars to concentrate ethanol content. Ethanol is metabolized into acetaldehyde by the enzyme alcohol dehydrogenase.

Removing the water from a reaction with a Dean-Stark water trap. 

The toluene what is a solvent in this case forms an azeotrope with water what boils at 84.1 °C while pure toluene boils at 110.8 °C and this azeotrope contains 79.8% toluene by weight, the rest is water. The mixture distills out from the flask, condenses down on a condenser (not on the picture, but its above the trap at the left side) and the water is collected in the trap, since it is not miscible with toluene and it has a higher density.

Did you know that in the chemical industry they dry almost everything with azeotropic water removal? Solid desiccants (magnesium sulfate, calcium chloride, magnesium sulfate, ect.) are non reusable and generate a lot waste, while solvents could be used several times and they remove every water what is present. The most often used solvents for drying is ethyl acetate, isopropyl acetate, toluene.