is Propylene Glycol and vegetable glycerine the same everywhere?

[Phydeau]

I've just found a large bottle of concentrated propylene glycol (USP) for humidors at a very low price ... is this usable for mixing juice?

Likewise for vegetable glycol.

Are all these equal for dilution?

 

[Hoosier]

USP is what you want. The thing that has me confused is "concentrated". It is either PG or VG USP or it is not.

It's like you said concentrated water. It's either water or it is not, it cannot be concentrated like flavorings or milk fat.

 

[Papa Lazarou]

The "USP" part means pharmaceutical grade, which as Hoosier says is what you want. The PG should be labelled "Propylene Glycol, USP" (or "Propylene Glycol Ph Eur" in Europe for example). Industrial grade PG should be avoided as it's not intended for consumption and I believe it can have levels of undesirable contaminants like DEG (diethylene glycol) in it.

The VG equivalent will be labelled "Glycerin, USP". You should have a read of this thread - http://www.e-cigarette-forum.com/forum/diy-e-liquid/52669-pg-vg-labeling-purity-please-read.html

As Hoosier says, I also don't understand the "concentrated" label - it is not possible to concentrate PG.