This is the first of a series of papers with a view to evaluation activities inliquid blast-furnace-type slags.The purpose of this paper is to present new results of calculation for activities of CaO and SiO_2 in liquid CaO-SiO_2,CaO-SiO_2-Al_2O_3 and CaO-MgO-SiO_2-Al_2O_3 systems from existing chemical and electrochemi-caldata with certain assumptions The activities of CaO in the above-mentionedsystems with reference to solid CaO as the standard state are plotted against(%CaO)/(%SiO_2).From a comparison of these ~αCaO-(%CaO)/(%SiO_2)curves,a new expression for basicity has been proposed instead of the simple(%CaO)/(%SiO_2)ratio.The activities of CaO in the various systems concerned becomeapproximately equal at the same basicity when the latter is calculated accordingto the new formula.Alumina shows amphoteric behaviour in the new basicityformula in agreement with the general pattern of slag constitution.

In the previous paper,a new expression for basicity has been proposed for blast-furnace-type slags.It is the purpose of the present paper to correlate thisbasicity ratio with desulfurization power using the data of Hatch and Chipman,Filer and Darken,and Taylor and Stobo on the distribution of sulfur betweenliquid blast-furnace-type slags and carbon-saturated iron.For this purpose,theactivity coefficient of CaS in liquid blast-furnace-type slags with reference to solidCaS as the standard state has been evaluated as a function of the basicity andthe sulfur content of the slags from existing equilibrium data.With the activitiesof CaS and CaO known,it has been possible to calculate the“theoretical”sulfurdistribution curve by plotting(%S)/[~αS],converted to(%S)=1.50,againstauthor's new basicity ratio.It has been found that the calculated sulfur distribu-tion curve fits fairly well the experimental data of various investigators on thesulfur equilibria between blast-furnace-type slags and metal.This fact seems toprovide an evidence for the usefulness of the new expression for basicity proposedby the author.

This paper describes the nature of striated inclusions present in certain mildsteel plates,the origin of such inclusions is discussed.Microscopic examinations supplemented by X-ray diffraction studies show thatthe main constituents of the striated inclusions present in the steel plates appearto be the same as found in the attacked layer of fire-clay refractories which predo-minately consist of mullite(3Al_2O_3·2SiO_2)and cristobalite.Taking into accountthe metallurgical history of the plate and change in the chemical compositionof the refractories brought about during teeming,there is reason to believe thatstriated inclusions in steel may be originated from the refractories caused bythe attack of MnO or MnO·FeO present in the liquid steel.

The rate of growth of ordered domains in AuCu_3 has been measured by ob-serving the rate of change of integral breadth of superlattice Debye-Scherrer lines.The result of experiment shows that in the temperature range of 350° to 370℃the rate of growth lies between 2.37×10~(-11)cm/sec to 16.8×10~(-11)cm/sec.Thelinear dimension of ordering domain is in the range of 15(?) to 300(?).Activationenergy of ordering is found to be 41600 cal./g.mole.It changes slightly with tem-perature.The activation energy,of ordering does not equal to the activationenergy of diffusion.It lies between the activation energy of diffusion of gold incopper and the activation energy of self diffusion of copper in copper.

In the previous paper,activities in liquid Fe-C alloys have been evaluatedfrom low carbon concentrations up to saturation with reference to pure liquidiron and solid graphite respectively as the standard states using Richardson andDennis' data on dilute solutions of carbon in liquid iron as the chief basis of cal-culation.Moreover,Smith's data on equilibrium between austenite and gaseousmixtures(CO_2/CO,CH_4/H_2)have been retreated to yield activities in austenitewith reference to pure γ iron and graphite respectively as the standard states.The purpose of the present paper is to make a thermodynamic analysis of theiron-graphite equilibrium diagram on the basis of these activity data and certainother data including the free energy of cementite,the derivation of which will bediscussed in another paper of this series.Direct experimental data on the solubility of graphite in ferrite are not avai-lable.Darken and Gurry as well as Hillert calculated the solubility of graphitein ferrite from that of cementite in ferrite determined by a number of investi-gators and the free energy of cementite calculated by Darken and Smith.In the present paper,the solubility of graphite in ferrite has been recalculatedusing the free energy of cementite calculated by the author and the results arecompared with the values reported in the literature.Wells' data on iron-graphite eutectoid equilibrium have been found to beessentially compatible with thermodynamic requirements.The agreement betweenthe experimental and the calculated values can,however,be still improved if 735°instead of 738° is chosen as the eutectoid temperature.Regarding the iron-graphite eutectic,the condition for equilibrium demandsthat the activities of iron in austenite and an iron-carbon melt both saturatedwith graphite at the eutectic temperature should be equal if the same standard state is used.It has been found in the present paper that this condition can bebetter fulfilled if 10.83 cal./g.atom/deg.is chosen as the heat capacity of liquidiron and 3650 cal./g.atom as the heat of fusion of iron.From an analysis of the δ iron-austenite-liquid peritectic equilibrium,it hasbeen found that a peritectic temperature of 1495° and a liquid phase of 0.58%Care better than 1493° and 0.52%C reported by Adcock as well as 1499° and0.53%C calculated by Darken and Gurry.Finally,the liquidus and solidus curves of the austenite-liquid field have beencalculated,the latter being found to concave up slightly in contradiction withthe conventional Fe-C equilibrium diagram.