Ferbam

Dissociation constant

Link to relevant study record(s)

Reference

Endpoint:

dissociation constant

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1999-05-20 - 1999-05-20

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 112 (Dissociation Constants in Water)

Version / remarks:

1981

Deviations:

no

GLP compliance:

yes

Dissociating properties:

no

Results the pKa of the ammonium acetate

The equivalent points for the titration by the HCl and NaOH solutions were the following:

chloridric acid 1.0 mol/L = 8.75 mL

sodium hydroxide 1.0 mol/L = 9.30 mL

Starting from the values of the 50% equivalent point, it was observed the following values by titration:

chloridric acid 1.0 mol/L = 4.37 mL pH = 5.11

sodium hydroxide 1.0 mol/L = 4.65 mL pH = 8.98

Using interpolation calculations, it was obtained the correspondents means of pH in function of the determines volume above and, consequently the refereed pKa. The results obtained for the references substances are shown here:

Reference substanc	pKa experimental 20 °C	pKa literature
Acetic acid	5.11	4.75
Ammonium	8.98	9.26

Test substance

The Table below presents the used values for the determinations of titration curves Ferbam, by means of titration with NaOH 1.0 mol/L and HCl 1.0 mol/L.

Table Values pH of Ferbam in function of the addition of NaOH 1.0 mol/L and HCl 1.0 mol/L.

Volume	pH	Potential	Variation	Volume	pH	Potential	Variation
of NaOH	solution	(mV)	of	of HCl	solution	(mV)	of
1.0 mol/L (mL)			potential (mV)	1.0 mol/L (mL)			potential (mV)
-	5,60	240	-	-	5,88	260	-
0,25	10,31	016	224	0,25	3,48	250	010
0,50	10,64	012	004	0,50	3,18	242	008
0,75	10,83	007	005	0,75	3,00	231	011
1,00	10,96	001	006	1,00	2,88	218	013
1,25	11,06	-005	-004	1.25	2,78	216	002
1,50	11,14	-011	016	1,50	2,70	216	000
1,75	11,19	-017	028	1,75	2,64	216	000
2,00	11,26	-022	039	2,00	2,58	217	-001
2,25	11,31	-027	049	2,25	2,53	218	-001
2,50	11,35	-032	059	2,50	2,49	219	-001
2,75	11,39	-038	070	2,75	2,44	220	-001
3,00	11,42	-042	080	3,00	2,41	221	-001
3,25	11,46	-046	088	3,25	2,37	223	-002
3,50	11,49	-050	096	3,50	2,34	224	-001
3,75	11,53	-054	104	3,75	2,31	225	-001

pKa results of the substance

It was not possible to determine the dissociation constant of test substance in water, because there were not equivalent points when titration with HCl or NaOH solutions.

Conclusions:

The methodological procedures using the reference substance ammonium acetate, results pKa values consistent with those found in the literature.
It was not possible to determine the dissociation constant of test substance in water, because there were not equivalent points when titration with HCl or NaOH solutions.

Executive summary:

The dissociation constant of the test substance Ferbam was analyzed according to OECD Guideline 112 (Dissociation Constants in Water), through titration methodology by measuring the direct pH in the aqueous solution at 20°C. A solution of ammonium acetate was used as reference substance. According to the results, it was not possible to determine the dissociation constant of test substance in water, because there were not equivalent points when titrating with HCl or NaOH solutions.

Description of key information

The dissociation constant of the test substance Ferbam was analyzed according to OECD Guideline 112 (Dissociation Constants in Water) It was not possible to determine the dissociation constant of test substance in water, because there were not equivalent points when titrating with HCl or NaOH solutions.

Additional information

Key: Pessin, 1999

The dissociation constant of the test substance Ferbam was analyzed according to OECD Guideline 112 (Dissociation Constants in Water), through titration methodology by measuring the direct pH in the aqueous solution at 20°C. A solution of ammonium acetate was used as reference substance. According to the results, it was not possible to determine the dissociation constant of test substance in water, because there were not equivalent points when titrating with HCl or NaOH solutions.

Other information: Vandegans, 1987

The study was equivalent or similar to OECD guideline n°108, Ed. 1981. For the various reasons mentioned, we consider that the determination of the stability constant of FERBAM is pointless and, especially for electrochemical reasons, impossible if the OECD prescriptions are to be followed.