PEG concentrations

[George DeTitta]

PEG concentrations can bemeasured quite accurately by refractometry
(you remember the good old refractometer from p chem days, don't you?).
The refractive index of PEG 8000 is related to the concentration
measured in %(w/v) by

[PEG8000] = (N - b) / a  where N is the refractive index and
 a= 0.0013889, b= 1.3325  

these values are for 24C - there is a small temperature correction
for other temperatures.  The relation holds for [PEG] in the range of
1%(w/v) to 50%(w/v).

~v

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