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<caption ALIGN="TOP">Propylene Glycol</caption>
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Propylene Glycol
Propylene glycol [57-55-6]
Synonyms: Propanediol; solar winter ban; monopropylene glycol; propane-1,2-diol; alpha-propyleneglycol; dowfrost; PG 12; sirlene; 1,2-Propanediol; 1,2-Dihydroxypropane; Methylethylene glycol; Propylene glycol; Trimethyl glycol; 1,2-Propylene glycol; PROPYLENEGLYCOL, REAGENT (ACS)
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Glycerol
glycerin [56-81-5]
Synonyms: Propanetriol; D-glycerol; L-glycerol; 1,2,3-Trihydroxypropane; 1,2,3-propanetriol; Glycerol; Glycerin; glyceritol; glycyl alcohol; trihydroxypropane; Glycerin mist; Polyhydric alcohols
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Isopropyl Alcohol
2-Propanol [67-63-0]
Synonyms: Propan-2-ol; Isopropanol; IPA; Sec-propanol; 2-Propanol; Rubbing Alcohol; Dimethylcarbinol; sec-Propyl alcohol; Alcohol; i-Propanol; petrohol; n-propan-2-ol; propol; spectrar; sterisol hand disinfectant; takineocol; alcosolve 2; 2-hydroxypropane; alcojel; alcosolve; avantin; chromar; combi-schutz; hartosol; imsol a; isohol; lutosol; DuPont Zonyl FSP Fluorinated Surfactants; DuPont Zonyl FSN Fluorinated Surfactants; DuPont Zonyl FSA Fluorinated Surfactants; DuPont Zonyl FSJ Fluorinated Surfactants; ISOPROPYL ALCOHOL (MANUFACTURING, STRONG-ACID PROCESS)
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Let's look at the chemistry of the two choices and eventually compare them to i-prop. Notice the similiarities and the differences between the two molecules. Prop Glycol has two -OH (hydroxy) groups and glycerol has 3. So what does this matter? Let me tell you...
Imagine that each of those OH groups are pulling on the "rope" wherever they are attached. This is likened to molecular polarity. In addition, the -OH groups lend themselves to increased "
solvation" due to hydrogen bonding. So, the more -OH's there are the better:
- Solvation we will get (i.e. - better PH solubility, get more powder into solution)
- Miscibility with water and other alcohols
Now, the
actual difference between the two may not be realized. Imagine if you had $10, 000, 000 and someone gave you another $10, 000...it's still an increase but since the starting amount was high anyway it goes largely un-noticed. Same this with these two...PG is already good at what it does and the benefits of Glycerol may not be noticed. But, I will be changing the PG in my mix to glycerol anyway...
Now, the comparison of both to isopropyl alcohol...do you notice the trend here with the chemical structures? Glycerol has 3 OH's, PG has 2, and now i-prop has only one. Isopropyl is more "polar" than the other 2 since the one OH is pulling on the rope and nobody is there to counter. What does this do for the mix? It allows for better solvation of PH's which ultimately decides whether you get 10 grams into solution or 15. This is also the reason that ethanol (EtOH, grain, Everclear) is better for solvation since the "rope" is shorter by 1 carbon and the polarity is higher.
The order of polarity is as such:i-prop (
highest) - Prop Glycol (
middle) - Glycerol (
lowest)
Let's wrap this up...
IMO, the preferred choice between the two would be Glycerol.
BUT, there is such a small effective difference between the two that it would be more practical to use whatever is convenient. This is said with the knowledge that i-prop alcohol is used as the primary solvent.
Chemo
BTW, I am also going to post this in the ingredient forum...
Please reply here -->
http://forum.bdcnutrition.com/showthread.php?s=&threadid=45