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Diss Factsheets

Toxicological information

Basic toxicokinetics

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Administrative data

basic toxicokinetics in vitro / ex vivo
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Meets generally accepted scientific standards and is described in sufficient detail.

Data source

Reference Type:
study report
Report date:

Materials and methods

Objective of study:
other: rate of formic acid dissociation at physiological pH
Principles of method if other than guideline:
Calculation of the chemical behavior of potassium diformate and formic acid solutions from titer curves.
GLP compliance:

Test material

Constituent 1
Reference substance name:
Potassium formate(1:2)
EC Number:
EC Name:
Potassium formate(1:2)
Cas Number:
potassium formate(1:2)
Details on test material:
Test substance: Potassium diformate

Test animals

other: calculation

Results and discussion

Any other information on results incl. tables

Potassium formate is expected to form the following equilibriums in  aqueous solutions: 

      <-->         HCOOH  +  HCOOK  [equation 1]

2)         HCOOH         
      <-->              HCOO-  +  H+     [equation 2] 

3)         HCOOK  
       <-->         HCOO-  +  K+     [equation 3]     

Mapping the pH as function of dilution and titer curve allowed to estimate the buffer effect of the diformate system (equation 1) 

and to  calculate the concentration profile of diformate, formic acid and formate  as function of concentration in water solutions. 

The calculations indicate that in aqueous solutions

i) at pH <4 and at concentrations >0.1% the equilibrium in equation 1 is  in favor of potassium diformate.

ii) at pH of 4 to 5, and at dilution down to 0.001%, most of the formic acid content is released from potassium formate.

iii) further dilution and increase of pH above 5, the concentrations of  formic acid and diformate decrease rapidly, leaving only formate left at 

pH 7 and above. No diformate exists above pH 7.

Applicant's summary and conclusion

Interpretation of results (migrated information): other: potassium diformate, formate, and formic acid are in equilibrium in aqueous solution. At physiological pH values around 7, the equilibrium is in favor of formate.
Read across can be made between formic acid and formate salts provided that the pH value of aqueous solutions is around neutral.
Executive summary:

Formic acid is in equilibrium with its salts in aqueous solutions. No diformate or formic acid exists above pH 7, only formate is left. The pKa for the dissociation of potassium diformate into formic acid and potassium formate (equation 1) is approx. 4.3. The pKa for formic acid is approx. 3.75 (equation 2). Formate salts dissociate in aqueous solution (equation 3).

1)   HCOOH-HCOOK        <-->         HCOOH  +  HCOOK  [equation 1]

2)         HCOOH                 <-->             HCOO-  +  H+     [equation 2] 

3)         HCOOK         <-->         HCOO-  +  K+     [equation 3]     

The equilibrium is in favor of formate at neutral pH values. Therefore, read across can be made between formic acid and formate salts provided that the pH value of aqueous solutions is around neutral (Hydro Research Centre, 1997).