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volume of 1 M tartaric acid solution to yield a
total volume of 10 ml. Then 15 ml of the hydro-
chloric acid-tartaric acid reagent (9 M HCI and
0.5 M tartaric acid) and 15 ml of 20% (w/v) am-
monium thiocyanate solution is added, following
which the aqueous phase is extracted with 5 ml
of ethyl ether.
Tests of this method have revealed that a linear
relationship exists between the absorbance and
the concentraiion of the niobium in the range 0.2
to 2.0 pg/ml. The coefficient of variation for this
method, based on standards, is 2%.
DETERMINATION OF TRACES OF COPPER
IN FLUORIDE FUEL MIXTURES
A. S. Meyer, Jr. 6. t. McDowell
Since copper is considered to be compatible with
molten fluoride salts containing sulfur impurities,
the nickel reactors used for the production of
fluoride fuel mixtures have been equipped with
copper liners to prolong their useful lifetimes.
This modification in production technique neces-
sitated the development of a s
the determination of copper in
salts. The spectrophotometri
$1 cuproine” (2,2’-biquinoline)
mogenic reagent, reported by G
for copper, was adapted for thi
Copper is determined as the
comptex formed by equilibrating
solution of the sample conta
a solution of 0.02% (w/v) cuproine in n-amyl
alcohol at pH 6. The copper complex is extracted
PERIOD ENDING JUNE 10, 1956
aqueous volume. The ammonium sulfate served
to mask the mass-action effect of ionic constituents
in the sample; however, it reduced the effective
pH range for quantitative extrsrction from a range
of 4.5 to 7.5 to a range of 6.0 to 6.5.
The absorbance of the organic extract is a linear
function of the concentration of copper up to 7.5
pg/mI, The coefficient of variation of the method,
as derived from standard samples, is 2%. Samples
of NaF-ZrF4-UF4 prepared in the copper-lined
nickel reactors have been analyzed for copper by
this method. The range of the copper concentration
was 1 to 25 ppm.
DETERMINATION OF TANTALUM
IN NoF-ZrF4=UF,
J. P. Young J. R. French
The determination3 of trace amounts of tantalum
in NaF-LiF-KF has been extended to include the
determination of tantalum in NaF-ZrF4-UF,. Since
zirconium and uranium interfere with the determi-
nation of tantalum by the pyrogallol methodI4 it
was necessary to develop some means of removing
these interferences. The separation of tontolum
from uranium in NaF-LiF-KF-UF4, which was
described previooslyI3 was accomplished by a
precipitation of the tantalum with cupferron. Zir-
conium, however, is also precipitated with cup-
ferron. According to Hillebrand et al.,’ tantalum
can bs separated quantitatively from uranium and
zirconium hy precipitation with tannin in a slightly
acidic solution of oxalate which is half-saturated
with ammonium chloride. Since the samples con-
tained alkali fluorides, it was necessary to dis-
mmonium oxalate and then pre-
’W. F. Hillebrand et ai., Ap lied Inorganic Analysis,
2R. J. Guest, Anal. Chem 25, 1484 (1953). p 598, 2d ed., Wiley, New Yore, 1953.
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