The sericite-feldspar bodies were fired at 1250°C and 1300°C, and porosity, linear shrinkage, true specific gravity, modulus of rupture, thermal expansion, translucency, and thermal conductivity of the fired bodies were determined.
The results obtained were as follows:
(1) The porosity of fired specimens was reduced to nearly zero, and the firing shrinkage was nearly equal in spite of the high content of sericite.
(2) The coefficient of thermal expansion decreased gradually with increasing the amount of sericite for feldspar when fired at 1250°C, while 1300°C fired bodies reduced the value rapidly as sericite contents are up to 10%, but the higher content of sericite it decrease gradually.
(3) The transverse strength of fired specimen increased in nearly proportion to the content of sericite.
(4) The value of true specific gravity became much higher with increase in sericite content.
(5) The translucency of the bodies decreased with increasing the content of sericite, although all bodies had much higher translucency than ordinary porcelain bodies.
(6) The thermal conductivity remained nearly equal up to 50 percent sericite, but with the higher content of sericite it decreased rapidly.

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Factors affecting the fluidity of oxide powders during heating were studied using an apparatus built after the model of a rotating viscometer.
A propeller made of clay refractory was suspended by a torsion spring to put into a revolving cup containing loose powders which were heated up to about 1100° at a rate of 10-12°C/min. under constant motion. The torque exerted upon the propeller, which is in inverse proportion to the fluidity of powders, was measured in frequent intervals by the degree of twist of the spring. The speed of rotation of the cup was 30rpm. The samples were silica, alumina, the mixture of alumina and chromium oxide, aluminium hydroxide for chromatography, clay, calcium carbonate, and calcium sulphate.
The torque seemed to be affected by the following factors arranged in decreasing order of influence:
(1) The evolution of gases such as water vapour, carbon dioxide, and sulphur dioxide generated by the vaporization of adsorbed water or by the thermal decom-position of particles. In this case the decrease of torque will take place due to the loosening of packing caused by the efflux of gases.
(2) The removal of water film from the surface of particles, which gives rite to the formation of electrical double layers leading to the increase of the repulsion force between the particles (W. A. Weyl, Ceramic Age, 60, Nov., 23, 1952).
(3) The thermal motion of the ions at the particle surface with increasing temperature, which brings the powders to sintering. Changes of the torque caused by this effect, however, is complex because of the peculiar agglomeration of the particles in the container.

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In previous papers the author was able to represent the two dimensional flow at the longitudinal center-line of a throat by superposing the velocity of the laminer flow due to pull with that of the convection current calculated by Peychè's equation and multíplied by the correction factor for the frictional resistance at the wall surfaces.
However, the problem should be treated as a three dimensional flow in order to obtain the more exact velocity distribution. In this case the profile of the pull current in a normal flat-rectangular throat assumes the form represented by the curves of higher order than the usual parabolic pattern, the fact which exerts considerable influence on the horizontal component of the velocity.
Based on the model experiments carried out systematically by changing the height to width of the throat and using 85% glycerin the authors were able to express the horizontal profile of pull current by an empirical formula.
u/u₀=1-(z/b₀)ⁿ
n=1.44+0.56b/h,
whose nomenclatures are given in the list at the end of the text.
Combining this equation with that of two dimensional flow appeared in previous papers a formula representing three dimensional flow
u=f⋅ρ₀gkΔθ/6ηl⋅y(h₀²-y²)[1-(z/b₀)ⁿ′]+3/8n+1/nW/ρb₀h₀³(h₀²-y²)[1-(z/b₀)ⁿ],
wheren′=2n-1.44,
were obtained. A comparison of calculated and observed values of the model experiments with 1/10 scale model proved that above equation was able to represent the experimental results with high fidelity. With the aid of this equation the authors modified the boundary conditions given in previous papers.
Moreover, the optimum dimension of a throat was able to express as
h_opt=2.91(1/f)^1/4(n/n+1)^1/4(W_ηl/ρ₀ρbgkΔθ)

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The effect of firing conditions in the adherence of ceramic coating was studied experimentally. The nature of the interface between coating and base plate, determined by the stripping technique, and by microscopic observations, was found to be affected by firing conditions. The following changes in the nature of interface were observed:
(1) At a lower firing temperature and for shorter period of firing, chromium oxide was formed, and the coating showed a good adherence.
(2) At a higher firing temperature and for longer period of firing, chromium oxide disappeared, and a poor-adherent coating was obtained.
Chromium and manganese, together with other elements which can migrate from the base metal into the coating, produced effects on the thermal expansion of the coating, whereas the mill addition of Cr₂O₃ and clay had only a slight influence. Such a mill addition raised the softening temperature.
Practically all of the coatings on stainless steel were more or less in the state of biaxial compression at a room temperature, because of the very large difference between the expansion coefficients of coating and base plate.
Current theories concerning the failure of ceramic coating under stress are discussed.

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