Drying of Brigueites—Briquettes belonging to two or three clays were placed in a drying oven and dried at 240° C. At the expiration of four hours at this temperature, they were cooled in dessicators pre paratory to obtaining the dry weight of each briquette. The dry weight of each briquette was found to the third decimal place on a chemical balance.
Saturation of the dry weights had been obtained, the briquettes were placed in aluminum pans, keeping them arranged in the pans in their regular serial order. Distilled water was added until only the upper surface of each test piece was above the level of the water. This exposure of one face of the briquette was to permit easy escape of the air from the interior of the brick, as it was being displaced by the distilled water. After standing thus in water for 18 to 24 hours, they were completely immersed.
After a total of 48 hours in water, the briquettes were placed in water wider a bell jar, and the air exhausted. In nearly every base, when a partial vacuum had been created, the air escaped from the briquettes at such a rate and in such volumes as to cause the water to ap pear to be boiling. From a previous experiment, the data of which are given in the following table, it was thought that in the average case, fairly complete saturation could be attained with 15 minutes treat ment in a partial vacuum.
Each saturated briquette was in turn suspended by a silk thread from the beam of a chemical balance, and its saturated weight taken, allowing for the weight of the thread. Without removal from the balance, a glass of water was placed on a bridge spanning the scale pan in such a man ner as to cause the briquette to swing absolutely free but completely immersed in the water. The suspended weight of the briquette was thus taken.
Calculations—The percentage of porosity of each briquette was cal culated by the formula : Wet Weight — Dry Weight Percentage of Porosity = X 100 Wet Weight — Suspended Weight Plotting of Results—In the previous study, that with clays molded into cones, the writer had arbitrarily established the following propor tion : Linear length on ordinate, equal to 2 per cent porosity; linear length on abscissa equal to difference of heat treatment of one cone : that is, 2:1. This( as before explained, was maintained between the coordin
ate factors of the porosity-graphs, so that the rate of decrease in porosity could be expressed numerically in terms of the tangency or slope of the curves, and that the factors so obtained would be comparable one with another at all times.
The divisions on the abscissas of the specific gravity curves are the same as those of the porosity curves. The divisions on the ordinate are proportionally; 0:1 Sp. Gr. :2 cone heat : :1:2.
Data obtained—In the following table are the data obtained in the above study. Data for a few more clays were obtained, but owing to their incompleteness they are not recorded at this place: On plotting the data obtained in this experiment they were found in most cases to be consistent, i. e., clay used for particular industries such as paving brick, fire brick, etc., exhibited porosity changes that were so concordant that the possible commercial use for each was pre dicted from the curves and in no case where the clays are now being employed did the predicted use differ from their present' use as re ported by those who collected the samples.
The curves in every instance were not straight, but curved so that their tangent or rate of declination could not he ascertained without the use of calculus. Inasmuch as the curves did not describe grad ually sloping curves, but in most cases exhibited well defined lags in decrease of porosity, it was found that a simple tangent factor would not describe in full the fusion behavior of the clays. A complicated modulus was devised which was not only a function of the tangents of the sections of the curves between points of lag, but also the length of each section. Considering the fact, however, that this scheme of study ing the fusion phenomenon is here first presented, thus not finding confirmation by other experimenters, and. since the modulus does not show more clearly the rate fusion than does the curve, no attempt was made to apply the modulus on the different types of clays.
In subsequent curves are given the limits of the areas traversed by the porosity and specific gravity curves of the different types' of clays.