Question

Comment on the statement: “humic acids have lower total acidity and carboxyl contents and greater aromaticity than fulvic acids. The molecular masses of fulvic acids are also much less than those of humic acids. Therefore, humic acids may be isolated by acidifying an alkaline soil extract.”

Answer 1

No,

Humic acid can note isolated by acidifying the soil as it has a larger number of the aromatic ring and carboxylic acid functional group. it is insoluble in the water at neutral pH.

while fulvic acid is soluble in the water at neutral pH.

Humic acid can be isolated by forming its acid salt by adding alkali (NaOH, KOH...). In basic medium it form Sodium/potassium humate which is soluble in the water and soil remain insoluble.

Further by filtering this alkali solution we can precipitate the humic acid by acidifying it. (Note: to isolate humic acid from the soil first you have to give alkaline treatment)