Measurement of Specific Gravity by Picnometry

Determination of the specific gravity of a solution of uranyl nitrete

Summary of method
A known volume of the solution adjusted at a controlled temperature is weighed and compared to the weight of water measured in the same container.

Equipments

• Volumetric Flask, 50-mL, class A
• Water Bath, temperature controlled to ± 0.1 oC at a temperature slightly above
• normal room temperature, and provided with clips for holding volumetric flasks.

Procedure

• Weigh the clean, dry volumetric flask and its stopper to the nearest 0.1 mg
• Fill the volumetric flask with the uranyl nitrate solution to a point close to the volume mark, using a thin stemmed funnel and a glass dropper.
• Place the stoppered volumetric flask in the water bath for 30 min.
• Use a finely drawn glass dropper to adjust the liquid volume to the mark
• Leave the flask in the water bath an additional 10 min to make sure that the bath temperature has been reached.
• Dry and weigh the flask to the nearest 0.1 mg.
• Repeat step 2 up to step 6 using boiled and cooled distilled water instead of the uranyl nitrate solution.

Calculation

Very accurate determinations of specific gravity require that vacuo corrections be made, but if a median correction figure in terms of grams of sample is applied to the solution weights in all cases the resulting error will not exceed 0.05%.

Sp gr = B-A + 0.0007(B-A) /C+A + 0.0010 (C-A)

B = sample plus flask in air, g
A = flask in air, g
C = water plus flask in air,g
0.007 g/g = correction factor applicable for densities of 1.3 to 1.5 and
0.0010 g/g = correction factor for water.

Precision

The limit of error at the 95% level for a singledetermination is ± 0.003%

Literature

ASTM-C799, Standard Methods for “Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical analysis of Nuclear-Grade Uranyl Nitrate solution”