This test method determines of purity of lactic acid, by using 1N sodium hydroxide titration with a phenolphthalein indicator.
APPARATUS
a). 5 ml stoppered weighing bottle.
b). 250 ml conical flask.
c). 100 ml measuring cylinder.
d). Burette.
REAGENTS
a). Standard 1(N) sodium hydroxide (NaOH) solution.
b). Phenolphthalein indicator solution.
Lactic acid Assay / Purity Procedure
Take a Lactic Acid sample in a 5 ml stoppered weighing bottle. From this carefully transfer about 1 gm (weighing accurately) sample into a 250-ml conical flask.
Add about 100-ml distilled water and shake well to mix properly.
Titrate against standard 1(N) sodium hydroxide (NaOH) solution taken in a burette using phenolphthalein as an indicator.
Assay formula of lactic acid
Assay (%) = Titre value (ml) x normality of NaOH x 9.003 /
Wt of Lactic Acid sample taken (gm).
Purity of Lactic Acid Formula
The purity of lactic acid is typically expressed as a percentage. The formula to calculate the purity of lactic acid is:
Purity (%) = Pure Lactic Acid \Total Lactic Acid* 100
Pure Lactic Acid refers to the mass of lactic acid that is of the desired quality or purity.
Total Lactic Acid refers to the total mass of lactic acid in the sample, including both pure lactic acid and any impurities or contaminants.