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Room Temperature

Sample 1

Sample 2

Sample 1

Sample2

0 1.5 1.43 1.48

0 -1.4 1.43 1.30

I0 -0.9 1.46 1.38

10 1.1 1.46 1.42

Note: Mixes based on composition ofTable II, solvent ofTable III. All specimens baked at 950°C.

lene, Koppers Co., Pittsburgh, Pa., No. FS 6296 (Table III) with good results. It is believed that this was due t o the h i g h e r boiling point of this solvent compared with xylene as well as its wide boiling r a n g e which permitted more gradual r e l e a s e of v o l a tiles on baking with less likelihood of porosity in the baked carbon. With increased content of solvent in the pitch, baking shrinkage decreased for specimens pressed at room temperature ( F i g . 3). Observation indicated at l e a s t 10 pct solvent was necessary for workability at room temperature. At this level, GAD was c l o s e to the objective of 1.53 g/cm 3. Despite the presence of solvent, baking shrinkage was less than for the hot

The Thermodynamic Activity of PbO in Liquid PbO-PbCI2 System H. SUGAWARA, K. NAGATA, AND K. S. GOTO In many c a s e s of accelerated hot corrosion of metals and alloys, liquid mixtures of oxides, halides, and nitrates play an important role, because these mixtures with low melting point could dissolve the protective oxide layer and then transport ions with a l a r g e velocity. However, thermodynamic data are very much lacking for ionic m e l t s containing various different types of anions. In 1970, Kay, Mitchell, and Ram1 reported the chemical activity of " F e O " in the liquid CaF2-CaO-"FeO" system. T h e i r results a r e very interesting, because a strong thermodynamic interaction is expected between oxygen anion and fluorine anion in the m e l t . This can be deduced because the activity of " F e O " very remarkably decreased with the replacement of 2F- by O2- ions. However, t h e i r melt composition was quite complicated, because the melt always contained two different cations and two different anions, as a total of at l e a s t four ionic species. H. SUGAWARA, formerly a graduate student, is now with Kawasaki Steel Corp., Mizushima Works, Karashiki, Japan. K. NAGATA, formerly a graduate student, is now with Centro de Ingenieria y Computacion, I. V. I. C., Caracas, Venezuela and K. S. GOTO, Associate Professor, T o k y o Institute of Technology, Department of Metallurgy, Member AIME. Manuscript submitted February I 1, 1977. METALLURGICAL

TRANSACTIONS B

m e l t . Accordingly, further tests were done with 10 pct methylnaphthalene solvent in the binder. Baked properties of 50 mm diam laboratory pressed specimens made at room temperature with 10 pct solvent compared well with those of laboratory specimens pressed from the hot-melt composition at 75°C (Table IV). In addition t o the u s u a l properties, "cathoding expansions" also were determined in a laboratory c e l l .3 Each specimen was suspended as a cathode and the change in spacing of two holes at different levels in the specimen was followed by m e a n s of extension r o d s . Cathoding expansions of the r o o m temperatur