The difficulty of interpreting the results of chemical analyses is more largely due to a lack of experimental evidence on the fluxing behavior of known complex mixtures. Interpretation of the facts concerning a given mixture is impossible until there is more known about mixtures of the same component substances in different proportional combina tions. For example, Seger' has shown that the fusibility of mixtures of pure AhOs and silica as determined by Bischof can be represented graphically as in Fig. 22.
Two important facts are shown in these curves.
First. That the kaolin-silica mixtures are more fusible than the alumin ium and silicon oxide mixture of an equivalent chemical composition.
Second. That kaolin containing 58.2 per cent flint practically the same fusibility as one containing 83 per cent, while the kaolin-silica mixtures containing percentage of silica between these two limits are more fusible than either.
Dr. Rieke' has shown that magnesite will flux kaolin, as is shown in, Fig. 23. From Dr. Rieke's results it would seem that a mixture of 85 per cent kaolin and 15 per cent magnesium carbonate has approx imately the same fusion point as 43 per cent kaolin and 57 per cent magnesite.
Dr. Mellor' has shown a similar fusion phenomenon with mixtures of feldspar and quartz, as exhibited in Fig. 24.
Surprising as are the facts shown in these three curves, there has been but very little effort to determine similar relations between the several pairs of oxides and compounds, and practically none to demon strate the fusion behavior of the several oxides and compounds in triple and quadruple combinations, and yet this is the very data that must be worked out before much can be accomplished in the interpre tation of a chemical analysis. When ceramic technology reaches this
state of progress an explanation can perhaps be made regarding the fact that in some eases the admixture of the refractory kaolin will cause a lowering of the fusion point, while the admixture of a flux such as feldspar to the same mixture raises the fusion In the following Tables XXVI and XXVII will be found the per centages of the various oxides into which the clays considered in this re port have been resolved. In Tables XXVIII and XXIX will he found the molecular composition of the clays as calculated from the analysis. In Table XXX will be found the results of a rational analysis of clays now used for paving brick manufacture in the State.
No attempt to interpret this data can be made at this time. After a discussion of the pyro-chemical properties of clays this data will be re ferred to with the endeavor to show all the possible relation there may be developed between the physical, chemical and pyro-chemical properties of clays. •