By "gallate" are you referring to 3,4,5-trihydroxybenzoic acid or the salt containing oxyanion of gallium the element?
Dear Dr. Yahia and Eugene,
By Gallate, I mean 3,4,5-trihydroxybenzoic acid and not the element Gallium. I would like to synthesize Iron Gallate which is the main reason I want to synthesize Sodium Gallate for reaction with iron chloride.
Most probably you are trying to make sodium salt of gallic acid / 3,4,5-trihydroxybenzoic acid.
Here the main issue could be the acidity of the phenolic hydroxy groups, which might make the salt formation out of the carboxylic group complicated if you use sodium hydroxide (NaOH). This is because of the fact that NaOH can react with a phenol to form phenoxide.
To overcome this, instead of NaOH, you may use sodium carbonate ( Na2CO3 ) or sodium bicarbonate (NaHCO3).
Gallic acid is little bit soluble in water (solubility approximately 1.5 gm/100 ml or less at lower temperature). But one can follow this method to prepare almost pure Sodium gallate. Make a solution or suspension of Gallic acid in water and treat it NaHCO3 (saturated solution or solid) under vigorous stirring. Please use slight excess of Gallic acid, say Gallic acid : NaHCO3 ratio approximately 1.0 : 0.9. Only carboxylic acid functionality will react with NaHCO3 to form salt and the phenolic -OH groups will remain unaffected. In the solution there will be Na-salt of Gallic acid along with little unreacted free Gallic acid as contamination. Now on evaporation of the water completely under reduced pressure, the solid Na-Gallate containing very little free Gallic acid will be produced. It is to be dried under vacuum. Now the residue is to be washed repeatedly with anhydrous diethyl ether. Since the free Gallic acid is very soluble in ether, it will go out with ether solution but the sodium salt being completely insoluble in ether will remain as solid residue on the filter paper or Buchner funnel. It can be collected and dried under vacuum to get almost pure sodium gallate.
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