Sodium monofluorophosphate solution is considered to be alkaline in normal.
However, the pH of its 2% aqueous solution is 6.5 to 8.0. It falls within the neutral range. This is because of the fact that sodium monofluorophosphate undergoes hydrolysis in aqueous solution to produce fluoride ions, phosphate ions and hydroxide ions, which effect the PH of the aqueous solution.
This process decreases bound fluorine and increases free fluorine, leading to a decrease in purity,making the aqueous solution of sodium monofluorophosphate gradually loses its original properties and functions, so it is necessary to avoid the occurrence of hydrolysis in practical applications.
How to prevent sodium monofluorophosphate from hydrolysis?
- Control the temperature: Avoid operating under high temperature, because high temperature will accelerate the hydrolysis reaction.
- Use dry environment: Keep the operation environment dry to reduce the effect of moisture on sodium monofluorophosphate.
- Avoid contact with air: When handling sodium monofluorophosphate, minimize its contact time with air to prevent moisture absorption and hydrolysis.
- Use protective gas: When necessary, inert gas (e.g. nitrogen) can be used to protect against oxidation and hydrolysis.
- Maintain PH of solution : Acids can catalyze the hydrolysis of SMFP; hydrolysis is accelerated in alkaline or very acidic solutions, or in the presence of cations capable of forming insoluble fluoride or low solubility orthophosphates.
Through the above methods, the hydrolysis of sodium monofluorophosphate can be effectively reduced to ensure its stability and functionality.
The other physical properties of sodium monofluorophosphate:
- It is soluble in water, hygroscopic.
- The solubility in aqueous solution is 42 g/100g water at 25 ℃.
- It is insoluble in ethanol and ether.
- To know more please click the link for “sodium monofluorophosphate physical properties“
Conclusion:
Sodium monofluorophosphate pH is 6.5 to 8, but it is deemed to be base generally. It is because of the ions soluted in the water showing the properties of hydroxide ion. It is important to keep the chemical from hydrolysis. The methods including controling the temperature, storing it in dry circumstances, avoiding contact with air, etc. There are also other physical properties of this chemical, which is effecting the using of it.
