ORNL-1816 - the Molten Salt Energy Technologies Web Site

ANP QUARTERLY PROGRESS REPORT
presence of sulfur. A colorimetric method4 was
adapted to determine the concentration of sulfur
quantitatively. In this method, sulfur is released
from solution as H,S by acidification with HCI.
The gas is adsorbed in a solution of zinc acetate
solution, and, upon the further addition of ferric
ammonium sulfate, a reaction occurs between
the organic reagent and sulfur to form methylene
blue, an intensely colored dye. The absorbancy
of the solution of methylene blue is measured with
a photometer at 670 mp. The method is extremely
itive with a workable range of from 5 to 50 pg
100 ml of solution. This range corresponds to
a practical lower limit of determination of about
1 part of sulfur per million ports of sodium.
Analyses of the sodium revealed that the sulfur
was not mly distributed. In particular spots,
the conc ion was of the order of 0.1 to 1% or
higher. The sulfur content of the sodium sampled
from the bulk of the trap was, however, much lower,
50 to 100 pprn, and that of the sodium in the system
was less than 1 pprn. These results indicate that
sulfur in sodium precipitates rapidly as sodium
sulfide and can be effectively trapped and removed
from the system. The solubility of sodium sulfide
in sodium is evidently extremely small.
Sulfur in Fluoride Salt Mixtures. The presence
of sulfur in mixtures of fluoride salts which are
being considered as proposed reactor fuels is considered
deleterious, principally from the standpoint
of corrosion. The major problem in determining
sulfur in fluorides is that sulfur exists in at least
two oxidation states, sulfate and sulfide, and, in
order to adapt the methylene blue colorimetric
method, the sulfate must be reduced to the sulfide.
The reducing mixture recommended by Johnson
and Nishita5 for sulfate in soils is used for this
purpose. About 1 g of the fluoride mix is heated
at the boiling point with 4 ml of a reducing mixture
composed of 15 g of red phosphorus, 100 ml of
hydriodic acid, and 75 mi of formic acid. Reduction
of the sulfate is complete within 30 min, and
then the colorimetric method can be utilized. When
sulfur is found in fluoride mixtures, the principal
portion of the sulfur is in the form of sulfate rather
sky, Anal. Chem. 21, 732-4
5C. M. Johnson and H. Nishita, Anal. Chem. 24, 736
132
Sulfur in H,-HF Gas Streams. The odor of H,S
has often been noted in gas streams in the fuel
production work. Two sources of this sulfur are
known: sulfate contaminant in fluoride salts and
fluorosulfonic acid, HSO,F, in hydrogen fluoride.
Sulfur from the first source is known to be of the
order of a few parts per million. A test of the
sulfur content of hydrogen fluoride was made by
dissolving the gas in a solution of NaOH, determining
sulfur in the solution by boiling the basic
solution in the presence of H,O, and precipitating
the sulfate as BaSO, with BaCI,. The sulfur
concentration was 2.7 mg per liter of HF.
A semiquantitative method for determining sulfur
as sulfide in off-gas from fuel production was set
up in which the gas was passed through a 6%
solution of NaOH. An equal volume of bismuth
nitrate in glacial acetic acid was added to the
scrub solution, and the turbidity, as Q result of
formation of Bi,S, was compared with previously
prepared standards. The procedure was made more
precise by measuring the absorbancy of the turbid
solution at 350 mp in a 7.5-cm cell with a total
volume equal to the volume of the test solution.
The concentration of sulfur found by this pro-
cedure ranged from 2 to 35 pg per liter of off-gas.
Determination of Fluoride in
NaF-KF-LiF-Base Fuels
J. C. White B. L. McDoweII
Analytical Chemistry Division
Investigation was continued on the feasibility of
a spectrophotometric titration of fluoride based on
the decolorization of a zirconium complex or lake.
Zirconium alizarin sulfonate and zirconium Erio
Chrome cyanine were tested as possible titrants.
A titration cell based on the design of Sweetser
and Bricker6 was fabricated so that the Beckman
Model DU spectrophotometer could be used to meas-
ure absorbancy. Although the data have not yet
been thoroughly evaluated, the technique does not
appear to be feasible for application to NaF-KF-
LiF-base fuels because of the slowness with
which equilibrium is reached. The procedure will
be evaluated before further work is done.
6P, 6. Sweetser and C. E. Bricker, Anal, Chem. 25,
253 (1953).
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