Page 86 - Analytical Chemistry I E-book
P. 86
Organic N + H2SO4 ⎯→ (NH4)2SO4 + H2O + CO2
Potassium sulfate (K2SO4) is added to increase the boiling point of the
sulfuric acid solution. This significantly increases the rate of organic
decomposition in the digestion mixture, shortening the length of time
required for digestion.
Some substances may be added to catalyze the digestion step such as
copper sulfate (CuSO4) and selenium (Se).
• Distillation:
Excess base (NaOH) is added to the digestion product to convert
NH4+ to ammonia (NH3). Ammonia (NH3) is recovered by distillation of
the reaction product.
(NH4)2SO4 + 2NaOH ⎯→ 2NH3 ↑ + Na2SO4 + 2H2O
