Sodium Nitrate Aerosol
Transmitted Off Circular Polarized Light
The nitrate aerosol in urban areas is due to the formation of nitrogen oxides (NOX) by vehicle catalytic
converters. The NOX reacts with the salt spray aerosol near the ocean coasts, with ammonia in inland areas,
and with carbonates in arid areas. This sample is from a building near Puget Sound in Washington State.
The building was about 800 meters from the Sound and about the same distance from Interstate Highway 5 (I-5).
This crystalline form is very characteristic but only forms if the surface concentration is locally high enough
and the rate of evaporation is slow enough to form relatively large crystals. Sodium nitrate is tetragonal and
forms in the classical "calcite" rhombs. Its birefringence is extremely high at over 0.22 and it has symmetric
extiction. In this case with circular polarized light no extinction position would be evident. The omega
refractive index is about 1.58 and the epsilon refractive index is about 1.335.
The nitrate aerosol in urban areas is due to the formation of nitrogen oxides (NOX) by vehicle catalytic
converters. The NOX reacts with the salt spray aerosol near the ocean coasts, with ammonia in inland areas,
and with carbonates in arid areas. This sample is from a building near Puget Sound in Washington State.
The building was about 800 meters from the Sound and about the same distance from Interstate Highway 5 (I-5).
This crystalline form is very characteristic but only forms if the surface concentration is locally high enough
and the rate of evaporation is slow enough to form relatively large crystals. Sodium nitrate is tetragonal and
forms in the classical "calcite" rhombs. Its birefringence is extremely high at over 0.22 and it has symmetric
extiction. In this case with circular polarized light no extinction position would be evident. The omega
refractive index is about 1.58 and the epsilon refractive index is about 1.335.
