Table 2. Comparison of the commercial glycerol, crude glycerol and enriched glycerol on physical properties from this and other works.

Component	Commercial glycerol			Crude glycerol		Enriched glycerol
	Ref. 30	Ref. 37	Ref. 38	Ref. 37	This work	Ref. 30	Ref. 37	Ref. 38	This work
Glycerol (wt%)a	99.9	99.98	98 min	35.60	39.63	96.0	98.20	98.67	98.44 ± 0.11
Water content (wt%)b	0.01	0.01	2.0 max	9.38	7.26	1.30	0.63	0.42	0.54 ± 0.01
Ash content (wt%)	0.0	0.002	—	4.73	5.77 ± 0.21	1.04	0.39	0.08	0.02 ± 0.03
MONG (wt%)c	0.0	0.001	1.0 max	50.29	47.34	1.09	0.78	0.83	1.00
Density (g cm−3)	1.27	—	—	—	1.07 ± 0.03	1.26		—	1.26 ± 0.01
pH	6.97	7	—	9.6	10.32 ± 0.01	6.98	7.08	7.1	6.95 ± 0.02
Viscosity (cp at 25 °C)	—	—	—	—	355.65 ± 2.22		—	—	823.30 ± 0.58
Color	Clear	Clear	Clear	Dark brown	Dark brown	Clear	Clear	Clear	Clear

^aMeasured by titration.

^bMeasured by Karl Fischer.

^cCalculated by subtracting the total of the amount of glycerol, water, and ash.