Steam or classic distillation for proofing?

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Steam or classic distillation for proofing?

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1

Alex White [email protected] 800-722-7556 x129


Vapor Pressure

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▸All liquids exist naturally in equilibrium w/ their vapor ▸Amount of vapor measured by pressure it exerts…thus “vapor

pressure” ▸ Increasing temp increases speed of molecules and gives more

molecules energy to become gas (vap press ↑)

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Boiling

▸When liquid heated to temp where vapor press = atm press (760 torr), liquid boils. ▸ If press = 1 atm, temp = “normal boiling pt”

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Retrieved from :https://www.bing.com/images/search?q=Boiling+Point&view=detailv2&qft=%


Raoult’s Law

▸Psoln = (X) (Ppure) ▸X=1 (pure solvent) ▸X<1 for all solutions ▸Psoln < Psolvent

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Retrieved from: https://upload.wikimedia.org/wikipedia/commons/thumb/4/47/Raoultov_zakon.png/220px-Raoultov_zakon.png


Vapor Pressure

Ptotal = PA + PB

PA = (XA) PA pure

PB = (XB) PB pure Each substance lowers the vapor pressure of the other (when pure).

The vapor above mixtures of liquids is more enriched in the more volatile component(s)

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Retrieved from: http://images.tutorvista.com/cms/images/38/mix-of-benzene-and-tolune.png


▸Water = 3 torr ▸Ethanol = 50 torr

▸50% ethanol/water total vapor pressure = ? Ptotal = PA + PB

PA = (XA) PA pure

PB = (XB) PB pure

Ex: 50% ethanol/water @ room temp


Ethanol = 25 torr Water = 1.5 torr total = 26.5 torr

%vap ethanol = Pvap /Ptotal

= 25 torr / 26.5 torr = 94 mol% ethanol (vapor)

answer

Ptotal = PA + PB PA = (XA) PA pure PB = (XB) PB pure


Distillation = boiling + transporting + condensing

▸Distilling creates a liquid with a

greater purity ▸ Distillate enriched but not completely

pure ▸How would you get a distillate of

higher purity?

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http://www.chemhelper.com/images/pictures/simpledist.gif


Sequential Simple Distillation (Batch)

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http://chemistry.about.com/od/chemistryglossary/g/Steam-Distillation-Definition.htm


Fractional distillation

https://en.wikipedia.org/wiki/Fractional_distillation#/media/File:Fractional_distillation_lab_apparatus.svg


Fractional still (column, continuous) vs simple still (pot)

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http://www.stillcooker.com/patent-still.php


Steam Distillation

▸Typically used two immiscible liquids which are heat sensitive and may decompose before reaching bp ▸ Often used to extract essential oils

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Retrieved from: http://3.bp.blogspot.com/--7Npvyc_Es0/URI1Ll6pNHI/AAAAAAAAAIY/HfIJpYh9LB8/s1600/steam-distillation.jpeg


methods

▸Apparent proof: solids ≤ 400 mg/100 ml

▸True Proof by Distillation: any sample

▸True Proof by Obscuration: spirits w/ 80-100 proof w/ solids ≤ 600 mg/100 ml ▸ ie apparent proof and solids by evaporation

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Other approved devices

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Retrieved from:http://www.ttb.gov/pdf/2014-7-21-device-approval-guidlines.pdf


▸Must distill spirits with > 600 mg/100 ml dissolved solids ▸Recommend apparatus specified in AOAC 942.06

▸ Flask, column, condenser, Class A volumetric flask ▸Do not approve or disapprove distillation units ▸Distillation should take 30 min – 1 hr ▸Sample must be same temp before and after distillation ▸Condenser coolant stay below 25°C ▸ http://www.ttb.gov/spirits/proofing.shtml

TTB distillation guidelines


distillation

1. Fill vol flask a bit beyond graduation mark 2. Equilibrate in water bath 3. Remove excess sample to grad mark 4. Place in distillation flask 5. Collect a bit less than grad mark 6. Equilibrate 7. Bring to volume with water (at temp)

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http://ingles-ciencias-uah-08.wikispaces.com/file/view/enrase.jpg/34201213/292x230/enrase.jpg


▸Only ethanol/water mixtures (about 40%) used ▸no influence from other components ▸concentration measurements made with TTB-approved density meter before and after distillation

Steam vs classic comparison


Results

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Steam Distillation: difference (%v/v)

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Classic Distillation: difference (%v/v)


▸Steam Distillation ▸ Mean difference = 0.09 %v/v, Std Dev = 0.03

▸Classic Distillation

▸ Mean difference = 0.02 %v/v, Std Dev = 0.02

▸TTB Tolerances (27CFR 5.37): ▸ 0.25 %v/v (>600mg/100ml) ▸ 0.15 %v/v (<600mg/100ml)

Results


▸Tested 154 distilled spirits ▸62 found non-complaint

▸48 non-compliant due to alcohol content (40 over)

TTB 2015 Alcoholic Beverage Sampling Program

From www.TTB.gov, “TTB Alcohol Beverage Sampling Program p1. http://www.ttb.gov/pdf/2015-03-08-fy2016-results.pdf


Thank you for your attention !

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Steam or classic distillation for proofing?