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Prepared at the 46th JECFA (1996), published in FNP 52 Add 4 (1996) superseding specifications published in FNP 4 (1978) |
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SYNONYMS |
Propanediol, Methyl glycol, INS No. 1520 |
DEFINITION | |
Chemical names |
Propane-1,2-diol, 1,2-dihydroxypropane |
C.A.S. number |
57-55-6 |
Chemical formula |
C3H8O2 |
Structural formula |  |
Formula weight |
76.10 |
Assay |
Not less than 99.5% on the anhydrous basis |
DESCRIPTION |
Clear, colourless, hygroscopic, viscous liquid |
FUNCTIONAL USES |
Solvent, glazing agent, humectant |
CHARACTERISTICS | |
IDENTIFICATION | |
Solubility |
Soluble in water, ethanol and acetone |
Infrared absorption |
The infrared spectrum of a potassium bromide dispersion of the sample corresponds with the reference infrared spectrum below |
PURITY | |
Water |
Not more than 1.0% (Karl Fischer Method) |
Distillation range |
99% v/v distils between 185-189o |
Specific gravity |
d (20, 20): 1.035 - 1.040 |
Sulfated ash |
Not more than 0.07% Test 5 g of the sample |
Free acid |
Add 3-6 drops of phenol red TS to 50 ml water, then add 0.1N sodium hydroxide until solution remains red for 30 sec. To this solution add about 50 g of the sample accurately weighed. Titrate with 0.01N sodium hydroxide until the original red colour returns and remains for 15 sec. Not more than 1.67 ml of 0.01N sodium hydroxide are consumed by a sample of 50.0 g. |
Heavy metals |
Not more than 10 mg/kg A solution of 2 g of the sample in 25 ml of water meets the requirements of the Limit Test (Method I) |
METHOD OF ASSAY |
Inject a 10-µl portion of the sample into a suitable gas chromatograph equipped with a thermal conductivity detector and a stainless steel column, 1-m x 1/4-in, packed with 4% Carbowax 20 M on 40/60-mesh Chromosorb T, or equivalent materials. The carrier gas is helium flowing at 75 ml/min. The injection port temperature is 240o, the column temperature 120 to 200o, programmed at a rate of 5o per min, and the block temperature 250o. Under the conditions described, the approximate retention time for propylene glycol is 5.7 min, and 8.2, 9.0, and 10.2 min for the three isomers of dipropylene glycol, respectively. Measure the area under all peaks by any convenient means, calculate the normalized area percentage of propylene glycol, and report as weight percentage. |
| Infrared spectrum |
Propylene glycol  |