ORNL-1771 - Oak Ridge National Laboratory

ANP QUARTERLY PROGRESS R €PO RT
P h y s ic a I Chem i s try
PHnDUCTION OF PURlFlED
E, R. Van Artsdalen
MOLTEN FLUORBBE5
Chemistry Division F. F. Blankenship
The heat of combustion and the heat of formation
have been determined for boron carbide,
The corn-
bustion process in a high-pressure bomb is both
incomplete and nonstoichiometric, it yields some
free carbon, but the amount depends upon certain
extraneous conditions. However, it is possible to
obtain a fairly reliable value for the heat of the
reaction
B,@ i-40,---? 2B,O3 + 20,
by allowing for incomplete combustion and non-
stoichiometry as determined by direct analysis of
products. The heat of combustion is W;,,., 2
-583.5 + 2.2 kcal/mole. From this value and otter
established thermal data, it is found that the heat
of formation is AH;,,.,, = -14.1 rt 2-7 kcal/i-nole
and thot the free energy of formation is 3F ;,., =
-13-9 kcaVmole,
The low-temperature heat capacity of molybdic
oxide, MOO,, has been measured in the range from
15 to 30OoK, arid the results are in fair agreement
with the work of Seltz, Dunkerley, and DeWitt,’,
who measured the heat capacify above 6Q°K. How-
ever, low-temperature extrapolations by these
3
authors according to the Debye T law ure in error.
Molybdic oxide has a layer structure, and its heat
capacity between 15 and 60°K varies a5 T2 in the
manner found for certain other crystals with layer
lattice structure, such as boron nitride.30 The
following values were obtained for Moa3 at 25OC:
C; 298,,6 = 17.93 cal/molendeg and SO,,,.,,
18.58 eu. Similar studies are in progress with
molybdenum disulfide, MoS,, another layer com-
pound,
Electrical conductivity and density measurements
are nearly complete for the molten salt systern,
potassium chloride-potassium iodide, which, in a
number oi respects, has hem observed to resemble
31
systems discussed previously.
28DetaiIs of this work will be published in separate
reports and articles from ths Chemistry Division. See
also Chem. Senizunn. Prog. Rep. June 20, 1954, Ol?bll.-
1755 (in press).
29H. Seltr, F. H. Dunkerley, and 3. J. DeWitt, J. Am
Chem. SOC. 65, 600 (1943).
30A. S, Dworkin, D. J. Sasmor, and E. R. Van Artsdnlen,
1. Chern. Phys. 21, 954 (19531, 22, 837 (1954), and Cbem.
Semzuim. Prog. Rep. June 20, 1953, ORNL-1587, p 19.
72
G. J. Nessle G, M. Watson
Materials Chemi stry Division
Use of Zirconium Metal as a Scavenging Agent
c, M, Blood I-!. A. Friedman
F. P. Boody
F. !4, Miles
G. M. Watson
Materials Chemistry Division
The most important contaminants of fluoride
melts (HF, FeF,, and NiF,) can be removed by
treatment of the melt wth hydrogen, but this proc-
ess reyuirrs long periods for newly complete re-
moval of the FeF,. Attempts have therefore been
made to demonstrate the effectiveness of zirconium
metal iri removing these impurities in a short time,
In NaF-Zrf, Mixtures, Known concentrations of
contaminants were added to 3.5-kg batches of previously
purified NaF-ZrF, (53-47 mole X) in nickel
containers and allowed to remain overnight at
800°C in contact with a considerable excess of
metallic zirconium (30 9); some stirring was assured
by continuous sparging with helium. No experi-
mental difficulties were observed either in equili-
bration or in filtration of the product,
In one experiment, the 10 g of FeF, added gave
an initial contaminant concentration of 1700 ppm
Fa. After treatment, the contaminants present in
the filtrate were 70 ppm Fe, 15 ppm Ni, and 15 pprn
Cr. In a second experiment, 9 g of CrF, was added
to give an initial contaminant concentratian of 1650
ppm Cr. The contaminants found in the filtrate in
this case were 90 ppm Fc, 2.5 ppm Ni, and 15 ppni
Cr. Thus these experiments indicate that the zirconium
metal addition is an effective means of
preparing pure NaF-ZrF, mixtures.
In NaF,KF-L*F Mixtures, The purity of several
2-ky batches of NaF-KF-Li F eutectic after treat-
ment with hydrogen and with zirconium mctal at
800°C is given in Table 5.11. It is evident thot
scavenging with metallic zirconium con be sub
stituted for most, if not all, of the time-consuming
hydrogen stripping process, Since the impurities in
fluoride melts are initially present in low concen-
trations, it is anticipated tliat the small aniouilt of
’E. f?. Vun Antsdalen, ANP Qunr. Prog. Rep. DPC. 10,
1953, ORNL-1649, p 58; ANP Quar. Prog. Rep. June 10,
1954, ORNL-1729, p 57.