Ammonium bifluoride [NH4.HF2]
Properties of NH4HF2
Formula mass : 57.04
Melting point :124.6°C (Sublimes at higher temperature)
Boiling point : 239.5°C
When dissolved in water, cooling takes place. Material is Hygroscopic at 50% humidity.
Analysis
Appearance : White crystalline solid (Orthorhombic crystals)
NH4HF2 : 98.76%*
(NH4)2SO4 : 0.05%
(NH4)2SiF6 :0.20%
Moisture :0.59%
Solubility in water : 60.2 g at 20°C and 156.4g at 60°C per 100ml of water
Solubility in HCl : 10% (w/v) sample is soluble in 15% (w/w) of HCl at 25°C
*Assay: Weigh accurately about 1.0gm of Ammonium bi fluoride sample. Dissolve it in 100ml distilled water. Titrate with about 1N NaOH. Use Phenolphthalein as indicator. End point is Colourless to Pink.
% acidity as HF = A / B
1st calculate Consumption of NaOH, B.R. X Normality of NaOH X 0.02 X 100 = A
Then Divided the result with " Weight of the sample " = B
%NH4HF= %acidityasHFx57 / 20