Sodium Uranyl Acetate
These tetrahedal crystals form if sodium is present in a
powder added to a uranyl acetate
solution.
Transmitted Oblique Illumination
Definition/Function:
These are characteristic crystals of Na(C2H3O2)-A
standard test for sodium is to test
the dry salt with a solution of uranyl acetate
(UO2(C2H3O2)-2H2O)
in water made acid with a little acetic acid. If sodium ions are present well in excess
of any divalent
ions then these typical crystals are evident. If these crystals form then sodium is
present.
If these crystals don't form then sodium ions are not present or they are part of a
complex
crystal structure that may not be unique. Extraction of the interfering elements may be
required.
Significance in the Environment:
Characteristic Features:
Sodium Uranyl acetate has a relatively high refractive index and so may appear black due
to total internal reflection if
illuminated with transmitted, centered Kholer illumination. Transmitted oblique
illumination will allow some light to come
through on one or two of the crystal faces.
Associated Particles:
A number of other crystalline or non-crystalline phases may be present. A summary of the
elements that may cause these
other precipitates is given on page 57 and 58 of Chamot and Mason.
References:
Chamot, Emile Monnin and Clyde Walter Mason, HANDBOOK OF CHEMICAL MICROSCOPY, Volume II,
pp. 51-58, 1940.
