Product code RXSOL-60-6604-769Category Lab Chemical

Price and availability on request. Send us the quantity and delivery location in Oman.

Request infoGet MSDSGet technical bulletin

Product description

The pyridine-free Karl Fischer reagent consists of two solutions, a dissolving agent and a titrating agent. The dissolving agent contains sulfur dioxide and a pyridine substitute in a solvent and is used for taking up the sample to be investigated with respect to its water content.

Applications

An essentially pyridine-free Karl Fischer reagent useful in the determination of water, comprising a dissolving agent containing sulfur dioxide and a pyridine substitute in a Karl Fischer solvent, and a titrating agent containing iodine in a Karl Fischer solvent, wherein the pyridine substitute is an alkali or alkaline.

Dosage

Karl Fischer Reagent (Pyridine free). single soln for titrimetric determination of water 1 ml reagent ~5 mg water.

Also known as

KARL FISCHER REAGENT Pyridine Free

Notes

The analysis of the water content of a sample by Karl Fisher titration can be carried out using a volumetric method or a coulometric one.

Remarks

Karl Fischer titration is simply a method for quantifying water content of samples. The fundamental principle behind this reaction is based on the Bunsen reaction between compounds such as iodine, sulphur dioxide to form sulphuric acid and hydrogen iodide. Karl Fischer initiated a new method based on Bunsen’s reaction. He discovered that the reaction could be modified for determining water in a non-aqueous system containing an excess of sulphur dioxide in the presence of a suitable base. He used a primary alcohol (methanol) as the solvent and a base (pyridine) as the buffering agent.
 
What is the Karl Fischer Reaction?
(1) CH3OH + SO2 + RN [RNH]SO3CH3
 
Reaction-1:  is where the alcohol reacts with sulphur dioxide (SO2) and base to form an intermediate alkylsulfite salt
 
(2) H2O + I2 + [RNH]SO3CH3 + 2RN [RNH]SO4CH3 + 2[RNH]I
 
Reaction-2: is the oxidation step where the intermediate is then oxidised to an alkylsulphate salt. This reaction consumes water.

Water and iodine are consumed in a 1:1 ratio. Once all of the water present is consumed, the presence of excess iodine is detected by the indicator electrode. That signals the end-point of the titration. The amount of water present in the sample is calculated based on the concentration of iodine in the Karl Fisher titrating reagent and the amount of Karl Fisher Reagent consumed in the titration. Depending on the type of base used the rate of reaction will vary. Classic Karl Fischer reagents contained pyridine, a noxious carcinogen, as the base. Due to its weak basicity the reaction is slow and the end point is not stable. The most common base used today is imidazole where greatest accuracy and repeatability can be achieved. Coulometry is an absolute technique so standardisation of Karl Fischer reagents is not necessary.
 
 
Coulometric Titration Method
In coulometric Karl Fischer, iodine is generated electrochemically in situ during the titration.
The anolyte contains iodide, sulphur dioxide, bases and solvents such as methanol. Electrolytic oxidation occurs when a sample is added to this anolyte.
Iodine is generated at the anode of the titration cell as shown in formula (3)
(3) 2I--2e ---> I2
Stoichiometrically, 1 mole of water will react with 1 mole of iodine, so that 1 milligram of water is equivalent to 10⋅71 coulombs of electricity

Where we supply

Oman. Stocked at our warehouse in Barka, South Al Batinah, and supplied to Muscat, Ruwi, Mutrah, Seeb, Rusayl, Barka, Sohar, Shinas, Saham, Buraimi, Nizwa, Ibri, Sur, Salalah, Duqm, Khasab and every other governorate.

Ports and free zones. Port Sultan Qaboos (Mutrah), Mina Al Fahal, Sohar Port and Freezone, Port of Salalah and Salalah Free Zone, Port of Duqm and the Duqm Special Economic Zone, Port of Sur, Khasab Port and Al Mazunah Free Zone.

Industrial areas. Rusayl, Sohar, Barka (Sanaya), Raysut (Salalah), Nizwa, Sur, Buraimi and Duqm industrial estates, Knowledge Oasis Muscat, and oil and gas sites across Oman.

Beyond Oman. We have branches in the UAE (including Fujairah) and in India (Kandla, Kolkata, Visakhapatnam, Chennai and Mumbai), and we also supply to South Africa.