S&0J B-N ■At! ^.sQ ■^'■rl x*-.^ ■^•f^li ^i^^S^\ ■iv5ffiWS '^^fitj^m-^ •'/af -^SK^ . V V UNIVERSITY OF ILLINOIS ^y^J::-^ LIBRARY Sg^i Class Book Volume ViO^. \ ^^ TfTi: t?^^ ^/^' ^^^ **v^A :>. *^ The person charging this material is re- sponsible for its return to the library from which It was withdrawn on or before the Latest Date stamped below. 'T5 UNIVERSITY OF ILLINOIS BULLETIN Vol. 4. MARCH 1, 1907 No. 13 [Entered at Urbana, Illinois, as second-class matter] STUDIES FROM THE SCHOOL OF CERAMICS NUMBER THREE. PYRO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS BY R. C. PURDY AND J. K. MOORE. PUBLISHED FORTNIGHTLY BY THE UNIVERSITY [Reprinted from the Transactions of tub Ambkican Ceramic Society, Vol. IX. Paper read at St. Louit meeting, February, 1907.] PYRO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS BY Ross C. PURDY AND JOSEPH K. MOORE^ Champaigu, Ills. INTRODUCTION. The v.'ork of Orton and Griffin on the "Effect of Car- bon in the Burning of Clay Wares," Orton on the "Role of Iron in Clays," Kennedy on the "Dehydration of Clay and Decarbonization of Calcium Carbonate," Singer on the "Decarbonization of Ferrous Carbonate," and Lovejoy on the "Expansion of Brick during Water-smoking," etc., are some of the studies of the pyro-chemical and physical be- havior of clays that have been reported in the Transactions of the American Ceramic Society. Considerable attention also has been given to similar studies by our contemporar- ies in the English Ceramic Society during the past three or four years. Time and space will not permit of a review of these studies, nor of the man}- observations that have been reported in the trade periodicals since ceramics has been classed as a science. Since in every clay industry it is in the burning that the usefulness of a clay is developed, the burning properties may justly be considered the most essential or vital factors to be studied, A clay may lend itself readily to manufac- turing processes, and yet not develop in burning the pro- perties requisite for making it into serviceable ware. Claj» may differ widely in chemical, mineralogical, and physical' constitution and yet be equally valuable for manufacture- into a given product. In clay burning, the combined influence of the chemi- cal, mineralogical and physical properties of clay consti- tute the cause, and the pyro-chemioal and physical proppT- p. & .M.— 1. Q /\. 4 PYRO-CHEMICAIi AND PHYSICAI. BEHAVIOK OF CLAYS. ties constitute the effects; knowing the causes, the effect ought to be interpretable. Owing, however, to the complex composition of clay and the variable properties of its sev- eral constituent parts, the true causes cannot all be ascer- tained in a sufficiently short time to justify the labor, even if methods were known by which they could be obtained. The effects, however, can be readily observed. Classification of clays on either the geological or the industrial basis has been attempted by many of the fore- most ceramic thinkers, yet it is freely admitted that as yet no satisfactory arrangement has been suggested. There is no agreement between the commercial value of clays and their geological age. Clays from which first class paving brick can be manu- factured, for instance, can be found in strata of any age and under almost any geological condition. Fire clays and shales of all ages are being successfully used in the manu- facture of paving brick. Glacial and alluvial deposits of clays have been found that are likewise serviceable for this purpose. Because the chances are far better of finding clays that can be made into paving brick among the fossil clays, the prevalent opinion is that it is to these types that paving brick manufacturers must look for their material. The facts are that there are many shales that are not fit to be manufactured into common building brick, much less into paving brick. Geological age or distribution, there- fore, has proven an unsatisfactory basis of classification. Chemical analyses of clays have been used in some cases as a basis of classification, but so unsatisfactory were the results that but very little importance can be attached to such a classification. A classification of the clays lying within political or natural boundaries, using as a basis the properties that are most essential to adapt each class to its commercial uses, has been the object of extensive researches of the United States Geological Survey and the various State Geological Surveys. Descriptions of the location and pro- perties of the clays to be found in the several survey re- PYBO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. 5 ports have failed in this respect. In some Survey reports, notably those of Iowa and West Virginia, a few of the pyro- chemical properties of their clays have been described, but in no case has much significance been attached to their determination. In fact, in no case has the study of the pyro-chemical properties been carried to such a degree of completeness as would warrant very conclusive deductions. Having had opportunity to study the clays of Illinois, un- der the direction of the Geological Survey of that State, the writers, after nearly three months of research, came to recognize their inability to draw satisfactory conclusions from the several tests made of the properties of raw clays, and to appreciate the importance of a more exhaustive study of the chemical and physical changes that occur dur- ing the progress of burning from dehydration and oxida- tion to fusion. Believing that a study of the changes in porosity and specific gravity at successively increasing heats affords a practical method for testing and classifying clays, and also a method that makes possible in most cases an accurate estimate of the commercial possibilities of a given class or type of clay, and further being confident that this method makes it possible to determine the most important proper- ties of any clay, we present here a detailed account of the way in which our tests were made and a few of the results of our investigations. SAMPLES OF CLAY INVESTIGATED. Location and condition : Clays used by the more im- portant paving brick factories of Ohio, Indiana, Illinois, Missouri, and Kansas were obtained in what was termed "dry-pan samples," i. e. they were taken from the chutes leading to the pug mill, after having been pulverized in the dry pans. Clays collected from several parts of Illinois and not used in the manufacture of ware at the place of sampling, were ground in a five-foot dry-pan in the labora- tories of the Ceramic Department of the University of Illinois. 6 PYKO-CIIEMICAL AKD PHYSICAL BEHAVIOR OF CLAYS. Types: Fire clays, shales and loess were the types of clays tested. There was not a sufficient variety of types nor enough samples of each type on hand to make an ex- haustive study, but this lack of samples does not lessen to any great extent the value of the results obtained. MANUFACTURE OF TEST PIECES. Wedging : Approximately one pound of dry clay was placed on a dampened plaster-covered table and sufficient water from the city mains added to develop the plasticity required to permit batting the clay into loaves. This was accomplished by adding the water in small quantities, and thoroughly working it into the clay each time, until the mass had the desired plasticity. It was then thoroughly wedged by kneading and batting until, on cutting the mass open, it appeared to be compact, i. e. without air blebs. Moulding : The loaf was then subdivided into smaller portions, each just sufficient to fill a mould 3/, inch x 21,4 inches x 4i^ inches. The slabs were made to fill the mould by pressure applied in a screw press. They were then placed in a miter-box and cut into brickettes % inch x % inch x 214 inches. Marking : The laboratory sample number and a serial number was stamped on each brickette. Drying: The brickettes were dried in an open room at summer heat. It had been found possible to dry even the most tender of clays in this manner, so it was assumed that all clays used in this test could, without detriment, be subjected to this treatment. Burning: Twenty-four brickettes of each clay were prepared. The ones on which the serial numbers 1 and 2 had been stamped were placed in a saggar to be drawn at Cone 010, those on which the serial numbers 3 and 4 were stamped were placed in a saggar to be drawn at Cone 08 and so on — each successive pair of brickettes of each clay being placed in a saggar to be drawn at a predetermined heat as follows : PYRO-CHEMIOAL AND PHYSICAIi BEHAVIOK OF CLAYS. Series No. ou 1 brickette | Heat at which drawn Hours intervening between draws Oxidized at 800 for 2 1, 2 010 hours. From 800°C to cone 010 6 hours. 3, 4 08 2 hours 5, 6 06 2 hours 7. 8 04 2 hours 9,10 02 2 hours 11,12 1 2 hours 13,14 3 2 hours 15,16 5 2 hours 17,18 7 2 hours 19,20 9 2 hours 21,22 11 2 hours \ The bric'kettes in the saggars to be fired from cones 3 to 11 were packed loosely in coarse white placing-sand, so as to prevent their sticking one to another. Only those clays known to be fire clays, or at least sufficiently refrac- tory to withstand severe heat treatment were placed in the saggars to be drawn at the higher cones. The eleven saggars were placed in a coke-fired, side- down-draft kiln in a manner convenient for drawing. The "spy" cones were centrally located in the kiln in a shield that protected them at all times from direct contact with the flame. When cone 010 was bent over sufficiently to touch the placque, the wicket was opened enough to draw the cone 010 saggar, the wicket replaced, and the heat slowly raised as shown in the above table. Cooling: The saggars in which the brickettes were placed were "tile setters'' 2 inches deep and 8 inches x 8 inches in area. Before placing another saggar was in- verted over the one containing the brickettes, so that on drawing, the brickettes were at no time exposed to the re- latively cold temperature of the room, except in one case of accident. The saggars were placed, uncovered, in the ash pit of the kiln, where tliey were exposed to the direct radiation from the hot grate bars above. In this manner, the brickettes were cooled rapidly at first, thus preventing 8 PYKO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. the fused portions in the briekettes from crystallizing very much, but from dull redness down to blackness the cooling extended over a considerable period. The method of cooling pursued in this investigation was not ideal. The briekettes should have been cooled slowly for the first 200 °C which, as above stated, was not the case. Inasmuch as there is danger of checking the vitrified briekettes by cooling down to room temperature too rapidly, some attention should be given to the last as well as to the first stage of the cooling period, but more particularly to the first. It was not possible to cool the briekettes under these ideal conditions, for the services of the kiln were in demand for other purposes, and circum- stances did not permit of delaying the burning until such times as the kiln would not be in use. Preparwg briekettes for testing: When cooled, sand grains were found to be fused to many of the briekettes, requiring that they be ground off on an emery wheel. Care was taken not to unduly heat the bricks while grinding off the sand, and yet as little water as possible was used. The bricks that were thus ground were washed in distilled water to remove all traces of dirt and adhering particles. From the unground briekettes all adhering particles were removed by a dry stiff brush. Each brickette was carefully examined for flaws induced during manufacture or cooling, and also in order to remove all adhering portions such as broken corners that might have been detached later in the test. Up to this point, all briekettes were handled together, without regard to sample or series number, except as before indicated. TESTING OP BRICKETTES. In all, 60 clays w^ere prepared for testing as above de- scribed, using 16 to 22 briekettes for each. The briekettes were now sorted, those of each clay being treated as a unit, so as to insure like conditions at all times for all briekettes of the same clay. PYKO-CHEMICAl, AND PHYSICAL BEHAVIOR OF CLAYS. 9 Drying of Brickettes : Brickettes 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 t(MU]H'rature, they were cooled in desicators preparatory to obtaining the dry weight of each brickette. Dry Weights : The dry weight of each brickette was found to the third decimal place on a chemical balance. Saturation of Brickettes : After the dry weights had been obtained, the brickettes were placed in aluminum pans, keeping them arranged in the pans in their regular serial order. Distilled water was added until only the npper surface of each test piece was above the level of the water. This exposure of one face of the brickette 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 brickettes were placed in water under a bell jar, and the air exhanste o o 5 8 ' io/ct'^ v. „> > I ^ /U£Uc:/ a > 9 MO^O i ) S' '*' "(7/^ ± v; V, fi3jlPI?/S 31/0/I/ ^ '"0/(7^ ^ \. '\ '^•'^^ s- 5y^/>y /^ ^. 'W/^^"" ^^j ^ A ayo<5 L^ < sT" ,^> V to z 4 73Z/p/)tO pa^jo/^ //t^ / * ^>t7^^ tc bO 3ava9lXN30 533^930 >> ©-.J .do -«-> Ri P< Tj< o t-l a t*J5 dS^ 3 ^i3 u >> <» 1. ctf T3 7 O^ o o 2 ID a 0) O >+' h. O bCT) -U >-i 5 -< e: (U v o isS -i-t^ 5| t< 3 o 11 PYBO-CHEMICAIi AND PHYSICAL BEHAVIOR OF CLAYS, The shale oxidized easily and before it was com- pletely dehydrated. Six other clays exhibited a reversal of the usual oxidization and dehydration changes, but none in so pronounced a degree as in the case of K 14. As yet no data have been obtained concerning the chemical or physical constitution of these clays that will shed light upon these rather remarkable exceptions to the usual order in which the dehydration and oxidation take place. The fact is established, however, that the cases are not rare where both changes take place simultaneously, and in a few cases the usual order is reversed. Second. In the case of H 23, oxidation had not pro- gressed very far at the end of 24 hours exposure at 650°, and the unoxidized portion of the brickettes vitrified on further heating to as hard and dense a mass as did the outer oxidized portions. No swelling or distortion of the brick due to the oxidation of the carbon and ferrous iron was noted. In fact, the shrinkage and rate of decrease in porosity was not abnormal in any respect. In figure 2, are shown the volume-shrinkage, porosity, and specific gravity curves for this clay. (See page 216.) In this figure, the specific gravity, porosity and volume of the bricks burned at different temperatures are calcu- lated in terms of the percentage of increase or decrease over those of the unburnt bricks. In other words, the raw factors are considered as a basis or datum from which the "burned" factors are calculated as increase or decrease. Zero or the datum line, therefore, represents the data ob- tained from the unburnt bricks. The percentage of increase of the burnt ware over that of the unburnt is shown above the datum line on the ordi- nate, and the percentage of decrease is shown below the datum line. On the abscissae is shown the actual percent- age of porosity of the burned brick. Points on the same ordinate represent a single brick. We have not plotted the data from all the bricks studied in this test, but only those in which the percentage of por- PYBO-CHEMICAIj and physical behavior of CLAYS- IS 1 ^ » / w 5 -s • • J J '5 0. 1 / J 1 1 r lU Q 1 .'; > f d: o o 2 1! 1/ 5^ o hi i 1 ^ < H / F >- o il 1 i o: 0. ) (y til <\J '. F ! Ji o i/'^ 1 1 CO ' \ ! — 1 ^ i n >^ i \ * 1 /[ / / ,/ <; X / f' o o > •0 o o UJ o s «> V < or t- i;> <1> o •a Q4 O w 0) O ^- =° a 02 O > 3 5l MOIJ-IONOO 1V1X1NII tNOWJ 3SV3a79a ONV 3«V3a7NI JO ^OVlNaOb'Sd C3 4) o o 16 PYRO-CHEMICAL AND PHYSIC AIj BEHAVrOB OF CLAYS. osity differed sufficiently to fix points on the curves that would show a comparative increase or decrease in the sev- eral factors. The fact that the actual percentage of porosity of the burned brick was taken in each case as a point on the ab- scissa, without regard to the porosity of the unburiit brick, will account of the irregularity in the curves. Notwithstanding the fact that the black unoxidized core remained, even when the whole exhibited a porosity of only 2%, the brick continued to shrink normally with each increase of temperature, and the specific gravity of the brick decreased less than in the case of many normally burned paving brick shales. This steady decrease in vol- ume and comparatively slight decrease in specific gravity gives evidence of a thermo-physical behavior that is oppo- site to that of the majority of clays containing carbon. (See plate III, facing page 218.) PHYSICAL CHANGES DURING OXIDATION AND DEHYDRATION. Contrary to the statements usually made concerning the physical changes in a brick at this period, our investi- gations show positively that not only the porosity, but also the volume and specific gravity of the brick are increased, and that it is indeed an exceptional case where all of these factors are not larger during the time of oxidation and dehydration than they were in the unburnt condition. A most peculiar and noteworthy fact in this connec- tion is that in many cases the specific gravity and volume remain large until the porosity has been increased to that of the unburnt brick. FUSION. From the laws of physical chemistry, it could not be expected that the heterogeneous mineral mass called clay, consisting largely of amorphous materials, would have a definite fusion point. According to Walker^ this would more properly be called a fusion period. 'Introduction to Physical Chemistry, p. 64. PYRO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. 17 Our studies, a part of the data of which are shown in subsequent curves, bear out this statement. It will be seen that in the case of the purest clays, according to the specific gravity curves, fusion begins as early as cone 3. In the case of some of the most impure shales, high in lime, fusion begins at a period considerably earlier than cone 010, Fusion thus early begun progresses with more or less regu- larity until the whole mass enters into the active thermo- chemical reaction and deformation of the ware ensues. Incipient vitrification, vitrification, and like terms are only descriptive of the effects at different stages of fusion. It is the rate of fusion, therefore, that determines the pyro- physical effects produced in the burning of clay wares dur- ing this period. The factors affecting rate of fusion are : The factors affecting rate of fusion are : 1st. Mineralogical composition. 2nd. Size of grain. 3rd. Volatile matter. 4th. Adsorbed salts. MINERALOGICAL COMPOSITIOxN. Synthetical studies of fusions of mixtures of pure minerals, have shown that the same chemical elements, brought together as constituent parts of different minerals, produce mixtures having unlike fusion periods. The rate of fusion and the regularity with which it progresses, as well as the point of complete yielding, are affected very largely by the manner in which the various elements are previously combined. Because of the difficulty of making a microscopic mineralogical analysis of a clay, the knowl- edge of these facts cannot aid in an attempt to foretell or explain in full the fusing behavior of clays. Realization, therefore, of the fact that difference in mineralogical make- up of clays of like ultimate chemical constitution causes difference in their fusion behavior is the only result of practical value that has so far come from the study of the fusion behavior of synthetical mixtures of minerals. 18 PYBO-CHEMICAL AND I'HYSICAJj BEHAVIOR OF CLAYS. There is one yerj notable exception to the above, and that is in the case of calcium carbonate. The effect of cal- cium carbonate depending upon the size of the grain and extent and homogeneity of diffusion throughout the clay mass, operates in a two-fold manner. If thoroughly blended with the clay in small particles, it operates as a very active flux. Its fluxing effect is most notable on ac- count of the rapidity with which the thermo-chemical re- actions between the nascent oxide and clay takes place. This reaction is in some instances so rapid as to make it very dangerous to approach the vitrification temperature. If the calcium carbonate is present in nodules, the thermo- chemical reaction just described can take place only at the points of contact of the decarbonized lime and clay, the remainder of the carbonate being converted into quick lime. The different effects of lime in these two physical condi- tions on the rate and regularity of fusion of the clay mass is obvious. SIZE OF GRAIN. The full significance of this factor can be appreciated only by considering extreme cases, as in the case of cal- cium carbonate, above cited, or as in a mixture of two min- erals such as feldspar and flint. When feldspar and flint are mixed as fine powders in the proportion of 75% feld- spar and 25% flint, the mass will be fused to a fluid at ap- proximately 1100° C in a comparatively short time. If, however, these two minerals were placed side by side in the shape of rectangular pieces having the same proportional weight as in the first case, the only fluxing action that would take place at 1100°C would be at the points of con- tact. Even if the heat was held at 1100° C, complete fusion of the two piecs of mineral could only take place when the glass, formed at the point of contact, enveloped and slowly ate into the unfused portions, and thus produced an inti- mate mixture of the two minerals by diffusion or surface tension. It is common experience that if complete fusion of the two minerals at 1100° C is desired when brought togeth- ' «f -^.- ^'"- ?y> 1 1 I -I <^ Pi.ATE III. Sli(>winerr('ir uxydatiim. PYBO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. 19 er in the form of coarse particles, considerable time must be allowed, and that to effect complete fusion in a shorter time, the heat must be raised from 1100°C to 1230'^ (ap- proximately) or the fusing point of feldspar. At this tem- perature, the feldspar melting would completely envelope or perhaps float the flint particles, and slowly attack and dissolve them away, just as water will attack and dissolve away a piece of loaf sugar. The above illustration, while an exaggerated case, nevertheless is descriptive of the effect of fineness of grain on the fusion of any two minerals that have thermal reac- tions one with another, and also descriptive of the fusion of a mixture containing particles of several minerals as a clay. In the burning of clay wares, where time is an import- ant and unavoidable factor, the effect of fineness of grain influencing the fusing of clays is particularly noteworthy. By the manufacturers of pyrometric cones it has been re- cognized as being such a powerful factor that the utmost care is taken to maintain uniformity in size of grain in their materials, both before and after manufacture into powdered cone stock. The importance of the time factor has been emphasized in ceramic literature so often as to render further remarks on this point unnecessary. VOL-\TILE MATTER. Chemically combined water, carbonic acid gas, carbon, etc., do not of themselves, on expulsion, cause thermo- ehemical reactions to take place between the stable bases, acids and silicate compounds left behind, but their expul- sion does involve changes in physical and, in some sense, chemical conditions that provokes thermo-chemical reac- tions between the remaining substances. For example, in terra cotta lumber, sawdust is added, so that when it burns out, it leaves the mass extremely porous, i. e. not dense as it would otherwise have been. The sawdust in this instance has been effective in opening the structure of the ware and p. & M— 2. 20 PYBO-CHEMICAL AND PHYSICAIj BEHAVIOR OF CLAYS. preventing the particles in the clay mass from coming with- in fluxing distance of one another as they otherwise would. What is true in the case of the sawdust in terra cotta lum- ber is true of combustible organic matter in clays. It is obvious, however, that the influence of carbon in this con- nection depends to a very large degree on the size of the carbon particles. The effect on the thermo-chemical behavior of clays of the expulsion of CO2 from such compounds as ferrous carbonate, calcium carbonate, etc., is another familiar phe- nomenon, the importance of which is not recognized in the attempt to interpret the results of an ultimate chemical analysis. If two equal portions of the same clay are taken, and to the one a quantity of red iron oxide (FeoOg) and to the other an equivalent quantity of powdered ferrous car- bonate (FeCOg) and the two mixtures burned under the same thermal conditions, it will be found that the mixture containing the ferrous carbonate will begin to fuse earlier, exhibit a more erratic rate of decrease in specific gravity as the intensity of the heat increases, and may or may not, depending upon conditions other than those here consid- ered, cause an earlier ultimate fusion. The same is true to a greater or less extent in the relative fluxing effect of the oxides and carbonates of other bases. The same phenomena are also notable in the compara- tive fluxing effect of such hydrous and anhydrous silicate compounds as raw and calcined kaolin. When one ingredient of a chemical compound is driven out by heat, or otherwise separated, the remaining portion is said to be in the nascent state, i. e. eager to combine with anything for which it has an affinity. If in an intimate mixture of clay and calcium carbonate, the clay is being dehydrated at the time the calcium carbonate is losing its COo, rapid fluxing between the two will ensue. In fact, dehydration of clay in the presence of calcium carbonate causes earlier expulsion of the carbonic acid gas from the carbonate. PYB()-CHBlrflCAIi AND I'HYSICAL BEHAVIOR OF CLAYS. 21 ADSORBED SALTS. The iufluence of the adsorbed salts in a clay on its pyro-ehemical and physical changes are not very well un- derstood. In fact, little is known about adsorbed salts be- yond the fact that they are present in nearly all, if not all, plastic clays. A few thermal phenomena, however, are un- explainable except on the assumption that adsorbed salts are present in such forms and quantities that they may be considered as the cause of these phenomena. In the tirst place, assuming that it is the influence of adsorbed salts that gives to a clay its plasticity, (an ex- ceedingly probable assumption) the peculiar fact that sample K 14, before cited, could retain considerable plas- ticity even after subjection to a temperature of 625° C for 16 hours may be explained by the possibility that some of the adsorbed salts had either not lost their peculiar proper- ties of giving to the clay grains a slipperiness which we call plasticity, or that they regained these properties by rehy- dration. The same may be said in regard to the plasticity developed in slate and hornblend by wet grinding. Further, the adsorbed salts may be volatilized at tem- peratures that are sufficient to cause the dehydration of clays. We know that considerable material can be volati- lized from clay by dry distillation, and it seems safe to as- sume that the material so volatilized was present in the clay as salts unstable at comparatively low temperatures. Hopwood^ has shown that the volatile material may po.s- sibly in some cases be silica or alumina. Dr. Kahlenlmrg in a lecture delivered at the University of Illinois reported the finding of a surprisingly large quantity of SiOo in the gases given off from fodder in Silos. In fact, sufficient evidence is at hand to warrant the assumption that the ad- sorbed salts of a clay may be of various composition, and need not necessarily be alkaline salts. Loss of plasticity due to the volatilization of the soluble salts before they have had opportunity to operate as fluxes therefore, is a 'Trans. Eng. Cer. Soc, 1904-5, p. 37. 22 PYRO-CHEMICAL AND PHYSICAL BEHAVIOK OF CLAYS. very probable fact. It is equally probable that there are some adsorbed salts which either are not volatile, or are so confined in the clay that they are not expelled on heating-. If any salt is thus retained on heating;, the clay can readily slake down in water to a mass, the plasticity of which is proportional to the amount of retained soluble salt and degree of delinquesence of the salt so retained. It is not uncommon to find soft burned brick and drain tile slaking down to a plastic mass. It is a fact, also, that the least plastic clays and conse- quently, according to the cause of plasticity assumed in these discussions, those containing the least amount of adsorbed salts, require higher heat to make a sound frost- resisting ware, and that in most cases tlie clays that can be burned into such ware at the lowest heats are very plastic. In the first of the cases, there is an absence of a fluxing medium between the grains and in the second case the salts at their melting heat fuse and cement the grains. If, however, all the salts have neither been volatilized nor fused, it may be that they are retained in a loose com- bination with the dehydrated silicate of alumina, which can be broken down under the influence of water, and both the salt and kaolin rehydrated. This assumption is believed to be substantiated by the fact that it was the brick made from clays whose so-called coarse grains were not indivi- dual crystals, but bunches of minute grains cemented to- gether by a salt that is but slightly soluble and hence re- sists disintegration in water even under long and severe treatment, that slaked after having been subjected to 625° G in the kiln. PRECIPITATED MATERIAL. Calcium carbonate, hydrates of silica, alumina, and iron, as well as zeolitic compounds, when first precipitated or formed, are in the majority of cases in extremely fine grains. The fluxing behavior of any substance is mater- ially different when thoroughly disseminated in minute PYRO-OHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. 23 grains, especially in the colloidal form, than when present in coarser grains. Iron, for instance, has been found to enter into chemical combination with silica as a ferric sili- cate when the iron is precipitated on flint and as a ferrous silicate, if at all, when the two are mixed as dry powders.^ The vast -difference between the fluxing action of ferrous and ferric oxides and compounds need not be discussed at this time. The important fact in this connection, however, is that it depends to a very large extent on the form and manner in which the iron is disseminated through the clay, as to whether it will combine as the lower or higher oxide. What is true of iron in this regard is true in a degree of other fluxes. SUMMARY OF FACTORS AFFECTING MANNER OF FUSION OF CLAYS. 1st. The manner in which the several constituent ele- ments are combined, one with another, very materially af- fects the fluxing behavior of a clay. 2nd. The size of grains of the several mineral con- stituents is an important factor in determining the fusing behavior of clays. 3d. The amount, form, and character of the volatile constituents of clay does not directly affect the thermo- chemical reactions, but the difference in the physical con- dition, structure of the clay, and the stability of the non- volatilized compounds caused by the expulsion of these substances, does materially affect the manner in which fusion takes place. 4th. The importance of the role that adsorbed salts play in the fusing behavior of clays is little appreciated. The evidence on the manner in which they operate is so indirect and circumstantial that definite statements or con- clusions are impossible. That they are important factors, however, there is no doubt. 5th. Concerning precipitated materials, we have evi- dence from synthetical experiments that prove beyond a 'Trans. Am. Cer. Society, Vol. VII. 24 PYRO-CHEMICAL, AND PHYSICAL BP^HAVIOB OF CLAYS. doubt that they must be considered as most potent in af- fecting the fusion of clays. From the above remarks, it is evident that the writers have but little confidence in the efficacy of an ultimate analysis of a clay as a means of foretelling its burning pro- perties. The combination, size of grain of the several com- pounds, solubility, volatility, and dissemination of the several salts, and lastly the manner in which the uncom- bined oxides are introduced into the clay are omre effective factors that the total ultimate composition. THERMO-CHEMICAL AND PHYSICAL CHANGES DURING FUSION. It is indeed very difficult if not impossible to deter- mine what the actual thermo-chemical reactions really are, which take place in the fusion of the clay particles first between themselves, and secondly when the whole mass becomes a more or less homogeiieons glass. ^ By the aid of the microscope, as will be seen later, more can be told in this respect than by any other means. But the effect of thermo-chemical reactions, however, can be detected by the changes in porosity and specific gravity. Because of our present inability to ascertain in full the reactions that take place, it seems best to refer to the chemical phases of fusion as "changes" instead of "reactions." The greater portion of the constituents of our clays being mineral substances, many of which do not entirely lose their identity in the burning of clay wares, it is most natural that these should exhibit in nature the same changes when treated separately that they do when heated togetlier in clays. Roth^ gives the following description of the physical changes in minerals on melting: •Prof. G. Tamman, Sprechsaal No. 35, 1904, summarizing his stud- ies on silicates says, "The volume of the glass is, at the lowest tem- peratures, larger than that of crystals." Mellor, Vol. V, p. 78, discusses the volume changes in silicates and cites A. Laurent (Ann. Chim. Phys. (2) 66, 96, 1837; A. Brongniart, Traite des Arts Ceramiques, 1, 283, 720, 3877) and G. Rose (Pogg., Ill, 123, 1890; A. S. Day and E. S. Sheperd, Am. Journ. Science, (4) 22, 262, 1906. Dr. E. Berdel (cited Vol. VII. p. 148 A. C. S. Trans.) describes similar physical changes in the heat- ing of ceramic materials and bodies. 2Allgemeine und Chemische Geologie, Vol II, p. 52. Mineral Specific Gravity of the Crystal Spec. Grav. when melted to Glass Percent. Reduct'n in Spec. Grav 1 Rbmarks Quartz 2.663 2.228 16.3 Quartz 2.65 2.19 17.3 Average Olivine 3.3813 3.0719 2.561 2.5522 2.58 2.8571 2.2405 2.3512 2.33551 2.381 15.6 27.0 8.1 8.5 7.6 Mica Glass compact Adular Adular Glass full of fine bubbles Sanidine Glass full of fine bubbles and dark-colored. Orthoclase 2.574 2.328 9.6 Glass full of fine bubbles Orthoclase 2.5883 2.3073 10.9 Glass colorless Microcline 2.5393 2.3069 9.1 Glass, colorless Albite 2.604 2.041 21.6 Full of fine bub- bles; white glass Oligoclase 2.C6 2.258 15.1 Glass full of fine bubbles Ollgoclase 2.6061 2.3621 9.1 White glass; bub- bly Oligoclase 2.6141 2.1765 16.7 Glass full of bub- bles Labradorite Hornblende 2.7333 3.2159 2.5673 2.8256 6.1 12.2 Gli'ss sliRhtly bubbly, with black and white portions Glass compact Augite 3.2667 2.8035 14.2 Glass compact Epidote 3.409 2.984 12.5 Red brown garnet. . 3.90 3.05 20.5 Green glass Lime-iron garnet . . 3.838 3.340 25.6 Granite 2.680 2.427 12.9 Green Glass; transparent strongly blebbed. Granite 2.751 2.496 9.3 Black Glass; opaque; strongly blebbed. Hornblende granite 2.643 2.478 6.2 Black Glass ; opaque ; strongly blebbed. Felsite porphyry... 2.576 2.301 10.7 Transparent very blebby difficult of fusion. Syenite 2.710 2.43 10.3 Glass homogeneous; dark colored. Quartz diorite 2.667 2.403 9.8 Glass homogeneous; dark colored. Diorite, quartz free Gabbro 2.779 3.100 2.608 2.664 6.3 14.2 Black Glass ; opaque ; compact; somewhat difficult to fuse. Black opaque glais ; easily fusible. 25 26 PYRO-OHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. The alterations in the minerals and rocks above cited are those induced when they are changed by melting, from a crystalline to an amorphous condition. Such complete changes as this cannot be permitted to take place in the burning of clay ware, and yet, as will be shown, the per- centage of decrease in specific gravity of many of our clays from the unburnt to the vitreous stage is greater than that given in the above data. This being true, it is evident that there are factors other than the alteration of minerals from the crystalline to the amorphous condition that affect de- crease in the specific gravity of clays. In the following table are given data which show the effect of heat on physical structure of brickettes made from various clavs: i . Black iron specks. Small black iron specks. . No iron specks. 0> CD O 0) > en 03 03 W) 03* o 03 c 03 swollen & self-glazed at cone 9 , chocolate at cone 3 and black apparent swelling at cone 5 t cone 6, black at cone 7 and 9. at 7 black at cones 6, 7 and 9. Swol- at 9 spongey at 9 and biack In color en at cone 7 K - C n c 5 ^ U rt CO o a> D. CQ o U 03 a o u o 3 CO p o _cS .Q 03 o B OJ o (U G 03 C o 03 o c. 03 o o OJ 03 « P. - goo S Z « a 03 S 5 ^ o . c -a 3 o 03 3 2 ^5 g o o 2 o O •" JS ti .« JS Oi O .a 03 ^ H « "^ £ g 3 03 O. ? z J3 M .c OJ ro O 03 03 03 -^■C«Ot^ J^iiJ< V -^^ bC rt M cfl CTl 3 c;1 3 3 3 J3 « T j: ^ " rt — w3 Cx. -3 Q C-c, CO fc m 02 ffi CQ CQ CQ CQ Ck o C5 Q c/: oa ». c i n CO CO 00 Ol iH 113 lO CO s°e--o CO o 00 «j(3 fc iH iH iH CO iH iH CO CO c >. lO CO O CO t- o E o 0> CO -^ CO t- •^ CO CO • '^ tr- O "* CO M o O <0 CO t^ ■C3 CO Tf CO • CO CO CO us lO M s CLi Cq M 1-1 t-H rH T-l 1-1 i-i c ^^ 00 CO CO •SS^ CO CO c- tH M M 00 o CO CO CO OS CO CO O t- CO lfi> O CO o 3 J o US lO ■«*< ■««< lO ■* 00 r^ 00 00 t- iH CO o CO a> o> a> o OS CO iH iH iH iH CO iH CO CO CO iH CO a o OS OS tH tH T-l ^-1 1—1 a> r-t 1-1 1-1 iH 05 ^ Oi us 0> O) O) OS t^ s y^ i-C i-H tH tH 1-( 1-1 iH 1-1 '"' iH >. OS iH U5 Irt c "u! CO 1-1 o> o CO CO Tfl CO OS 0> T*< CO OJ O 05 o lO Ci CO t- -<*' O CO t- CO iH > Zh rH iH iH iH tH ■sl^ iH U5 LO CO CO iH CO O t- t- t- iH t- t- "3 E ^S^ CO 00 -f t- ■«J< Ttl U5 CO O CO 00 t- t- tH IH iH tH tH 2 s ° (5z lO t- lO lO CO ir; us OS lo us CO us CO (A •rf T^ in 05 00 rf f iH rH lO <0 t~- CO CO iH CO 00 ■* CO 00 iH C^J »H l-H c^ <:\ '"' tH E > fc, :iH Ec( > fc fc ai > fe El< ^ > ti! UJ Ui tiJ tsj til W 09 C» 03 03 03 03 ca 03 03 0) © 0) 03 a> >»>.>. >. >. >» >. >. t>^ >. >. >> b >> j3 ja J5 .a x3 .3 ja — a a fi rt ctl CIS aj at c4 0] 0] c« cd a ai 03 03 m w m w O O O D D C) U O QUO O o U .^J! .« .M .a .« .id 4>J o y « 43 y o o V 0) 0) o 9 (B - ;h b (.. ^ E u t> H b b CC( u. b U, t^ CZ4 [X4 (X4 U. u- U< W) bD W) M to 60 60 1-1 r-l iH iH tH M IM CO CO CO CO CO CO CO c 3 a _a 3 _3 3 O O O o O o O o o o o c o o c^ cd cj ^ ^ cd ^ 2 Z Z Z Z Z Z z z z z Z z Z Oi Oi 0, CLh PLi PLi 04 27 a S o w " s « S V n i3 r; - 8^1 = « « 5 ?: ■rt " C ^ ex O o m.£ " " ^^ « « •iol g -a tiUu ^ 09 Q c ^■ - — rt s wj O - rt" - «, 2 M 611 S ~ C u 3 v ca a Q J3 ^^ ^ »- o Q Q U 2 J3 -O ca o o cn o era B m Q « t^rt" = 0^- *> 15 CO CO CO CO 10 CO • OJ • CO CO • C— 1>— It-I"— iC3t-iHCOb-r-li— ICOi-IOOOOOCO rH'~''~'T-l'~* tHi-ICO t-i 1-1 ©©©©©©©©3)® 0) a; © © © © ©©©rtefloJcScaceripSaJcS rt (T| nS oJ rrt "rtrtrtxixijaxi^^pua^^^ JH x: ^ ,£3 ^ Xi x; ,S^ja«2CQiMc«a!coa3CQma! 'Si OT ra m o! CO w CQCQCQ^^^^^^^^,^^ a ^ ,M ^ ^ i< ^ jsjpM^wsJw^iiiJiiiiiJii f) c; t> uoot^TIfc-^t-.t-^t-"*-' u u. ii ;-. tH !-> T:T:T:P3pqixip:pqp3«P3mp3 m m CQ m « m m pqp3P3 tiotiobowtobobobobobo tin M 60 t>c be to W) bObObOO flfl S555.S55 p a a a p a e c O'O'O'O'O'a'O'a'O'O'O > > > > > > > rn (fl m nients are quartz, feldspar an s \ r o 1 il ■ / o a ! y !4 1 / 1 i / / / / / / \ ( / "f o vi J 5 ;" III u < z lO bo PI • S 9 o CO ^i y "Sea (0 o a CO ^.j J h o o o < LI rt-.j > C u o C4X3 ^« 7 od 6B ¥o^ ^ w UJ .. .— ^t; O o <1> \ o \ o 0. \ \ ^ 10 \ \ > V 1 1 \ \ \l ^^^^^^^ > 6 r TEMPERATURES CXPRESSeO IN COWCS Curve showing changes in porosity of clay V 2, at different temperatures. PYRO-CHEMIOAL AND PHYSICAL BEHAVIOR OK CLAYS. 39 TRANS. AM CER.'50C''voClX PL/RDY'aNO MOORE PLATE VII ZJ> k,^^ ^ ^H "^ \ \ \ \ > I \ \ i o u a. \ \ > V2 NO. 2 F1R£ CLAV 14 OlO 08 06 04 TEMPERATURES, EXPRESSED IN CONES Curve showing changes in specific gravity of clay V 2, at different temperatures. 40 PYBO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. While such clays vitrify too rapidly to produce tough bricks, such as are demanded for street paving, they become impervious to water at low temperatures and do not soften by fusion with increase of heat ranging over several cones, or swell because of the generation of gases from the interior of the brick. In other words, while bricks made from such clays are brittle, they are rendered hard and impervious to water at comparatively low temperatures, and at the same time have a relatively wide heat range before failing by complete fusion, or becoming distorted by expansion of gases in their interior. The writers have not had suflflcient experience with this method of classification to justify them in offering a complete scheme for the grouping of clays, aud have there- fore suggested only five classes. NUMBER ONE FIRE CLAYS. The writers of Clay Reports have heretofore failed to recognize that of two clays having similar ultimate chemi- cal compositions and similar ultimate fusion periods, one can be used in No. 1 fire brick, while the other would fail utterly as a fire brick material, and that the one failing as a fire brick material would be the only one that could with success be used in the stone ware industry. Several exam- ples of the foregoing were noted in the examination of the Illinois fire clays. In fact, the case is not an uncommon one. In fire brick, maintenance of an open structure through the entire heat range used in the various ceramic industries is essential. On the other hand, in stoneware, closeness of structure at comparatively low temperatures, or early vitrification followed by a long fusion range is absolutely required. It is evident, therefore, that a classi- fication of refractory fire clays (so called because they withstand heat equivalent to cone 27 or more without fail- ure) should take account of this difference in their manner PYBO-CHEMICAl, AND PHYSICAL BEHAVIOR OF CLAYS. 41 of fusion. This essential difference in the behavior of fire clays is recognized in the tentative scheme of classification here presented. It will be noted that these clays show comparatively little decrease in porosity from cone 010 to cone 11. This decrease averages from 7 to 15% of the initial porosity and in no case does it exceed 17%. The specific gravity remains fairly constant from cone 010 to cone 3, and then, even in the purest clays, it begins to decrease slightly. This decrease in specific gravity in the No. 1 fire clays, even when the porosity remains very high, is considered as evidence of the influence of the ad- sorbed or cementing salts which, while constituting but a very small part In- weight of the whole, are nevertheless the potent factor in causing fusion. The chemical comx)osition and ultimate fusion point of these clays as determined in the chemical laboratory of the University of Illinois, under the supervision of Profes- sor S. W. Parr, are as follows: Sample Number Moisture Volatile Matter SiO, AljOj Fe,0, TiO, Total Fusion point H. 24 0.6 4.63 76.10 15.31 1. 10 1.31 99.06 30 V. 11 1.74 10.28 66.28 26.68 8.24 1.29 99.60 Not reached F. 18 0.84 6.66 66.88 21.87 2.23 1.18 99.86 29 F. 19 1.19 6.31 68.12 20.08 1.76 1 16 98.62 31 42 PYBO-CHEMIOAL AND PHYSICAL BEHAVIOR OF CLAYS. TRANS. AM CER SOC VOL, IX PUROV ArvJO MOORE, PLATE IX, 50 /K> |2 T O z UJ in r L^,.^^^ Q. X III ^ k. ^^ V • >■ N \y \ o > k. ^> p^-^^ L. "^ NO. F5 I FIRE CLAY o ' TEMPERATURES, EXPRE&SE.O JtS CONES Curve showing changes in porosity of clay F 5, at different temperatures. i PYRO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. 43 TRANS AM CER SOC VOL IX PUROV AND MOORE. ^LAT^ X ' ^ . \^ ( 25 ^V k \ 1 ^ iJ > t ^1„ M U Ol 13 t* OO C^ 06 O* 02 I 3 S TEMPeRATURE^, EXPRESSED IN CON E5 Curve showing changes In specific gravity of clay F 5 at different temperatures. 44 PYBO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. TRANS AlVI CER SOC VOL IX PURDY AND MOORE. PLATE XI 1 1 in 1 j u <^ 1 — < "-^, 1 Q. Z O ^V . ^ ^ ! \ 1 1 iji \ 1 I \ i > > L^__^^ H S ^ kw 2 T 10 F 18 NO 1 FlRE CLAV CONE OF FUSION 30 - o TEMPERATURES. EXPRESSELD IN CONES Curve showing changes in porosity of clay F 18, at different temperatures. PYKO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. 45 Z7 TRANS AM CER SOC VOL. IX PURDV AND MOORE. PLATE XII 1 K L ^ zs i3 2 3 > r o ll U U a N le 1 b FI8 NO 1 FIRE CLAV CONt OF Fu6lOt4 30. i« 1 lO e b * 2 ■ 5 II TEMPERATURES, EXPRESSED IN CONES Curve showing changes in specific gravity of clay F 18, at different temperatures. 46 PYRO-OHEMICAIi AND PHYSICAL BEHAVIOR OF CLAYS. TRANS AM CER soc. VOL IX PUROY AND MC >ORE. Pi ^TE Xdl OO t- ■■ Z uJ -J 30 ' 0^ 1 *^ z . N ^ 1 D 1 ) \ . Ui a. \ \ O t**"^ ,_^ 1 1 ] U O 0. i i F19 NO 1 FIRE CLAV 1 f .TErvtPER/VTURES EXPRESSED IN CONES Curve showing changes in porosity of clay F 19, at different temperatures. PYRO-CHEMICAL AND PHYSICAL, BKHAVIOB OF CLAYS. 47 '■> rPANS AVI CER 50C VOL. 9 PURDV AND! MOOBE, PL^TE. XIV _, ._ ., ~^ — i — ^-^ ^^ c "^ I ! X """^1 i* < i 1 > r s Ojo 1 1 o bJ a If),, 1 1 1 18 — F 19 . CONC OF FUSION JO* 14 oio oa o6 04 oe I 3 5 TEMPERATURES, EXPRESSED IN CONE.' Curve showing changes in specific gravity of clay F 19, at different temperatures. 48 PYBO-GHBMICAL AND PHYaiOAL BEHAVIOR OF CLAYS. TRANS AM. CER SOC VOL IX PURDV AND M OORE. PLATE XV rs. W_ a. 'J a. N r^ ^ a "•*^ L u . \ (L X N i o g 1 t -4 H 24 NO.I FIRE C1_AV TEMPERATURES EXPRESSED IN COISES Curve showing changes in porosity of clay H 24, at different temperatures. PYBO-CHEMICAIi AND PHYSICAL BEHAVIOR OF CLAYS. 49 TRANS AlVl CER SOC VOL IX PUROY AND MOORE,! PLATC XVI •"t _ -^ kw N k. ^J N >- 1- 1" O o o UJ Q. H 24- Not FIRE CL.AV r 4 "O Ot 3 o •J o 4- 2 II TEMPCRATURES EXPRCSStO IN CONES Curve showing changes in specific gravity of clay H 24, at various temperatures. 50 PY BO-CHEMICAL AND PHYSICAL, BEHAVIOR OF CLAYS. TRANS. AM CCR. SOC VC ' IX PURDY AND MOOPE. PLATE XVU i __L.___ . 1 ! 1 1 ( ^.-— ^ L k^ ^**<^ L^ ^ Kv ^ k ^*v r*^ kv > V n NO 1 FIRE Cl_A,V TEMPERATURES. EWRESSED IN CONES Curve showing changes in porosity of clay V 11, at various temperatures. PYRO-CHEMICAL AKD PHYSICAL BEHAVIOR OF CLAYS. 51 TRANS. AM CER SOC VOL. IX PURDV AND MOORE PLATE Xvui o o o 1„ 1 1 ' ' ' ^ k N ^^ . vu NO 1 FIRE CLAY 010 06 O* 02 I 3 5 TEMPERATURLS. EXPRESSED IN CONES Curve showing changes in specific gravity of clay V 11, at various temperatures. P. & M —4. PYRO-OHBMIOAIi AND PHYSICAL BEHAVIOR OF CLATS. 5S NUMBER TWO FIEE CLAYS. A few number two fire clays are represented in the following collection of plates. It will be noted that while the decrease in specific gravity of this group of clays is about the same as that shown in the No. 1 fire clays, the porosity shows a much larger decrease. The early vitrifi- cation and slow fusion is quite pronounced in this group, permitting their use in the paving brick, sewer pipe, stone- ware and terra cotta industries, but not in the manufacture of No. 1 fire brick. The chemical analyses of two of these clays, made in the chemical laboratory of the University of Illinois, under the supervision of Professor S. W. Parr, are as follows : Sample 1 Number | Moisture Volatile 1 Matter | SiO, Ai.o. Fe.O, TiO, Total 1 Fusion point V. 4 K. 12 2.37 0.60 8.84 10.09 64.80 54.37 29.44 23.61 1.70 6.14 0.82 fluxes 6.97 97.97 100.78 ■ot reached not deter'ed 54 PYRO-OHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. TRANS. AM. CER. SOC VOL tX PURDY ANO MOORE. PLATE XIX ^ ^^ L ^^^^ \ ^ \, S k ^ k^.^^^ NO. a FIRE CLAY TEMPERATURES. EXPRESSED IN CONES Curve showing changes in porosity of clay F 4, at different temperatures. PYRO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. 65 TRANS AM CER SOC VOL IX PuRtTY AND MOORE PLATE XX ZJIk zs / ^ \ \ > < O ^ ^. O IJ a F 4. NO 2 FIRE CLAV • vw wo VO V*- U£ ' -J -J ' J ' < I TEMPERATURES, EXPRESSED IN CONES Curve showing changes in specific gravity of clay F 4, at different temperatures. 66 PYBO-OHEMICAL AND PHYSICAIj BEHAVIOB OF CLAYB. .TRANS . AM. ceR. soc. VOL O. PVJROY />*40 MC )ORE, Pi .ATE. XXI . ■ / 40 * ' i t \ > k \ \ 10 J) . F2I NO. e riRE CLAV CONE OF Fusion £9 o c lO O B O b O ^ o z i i ? 3 II TEMPERATURES. EKPRESiED IN COtSES Curve showing changes in porosity of clay F 21, at different temperatures. PYRO-OHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS, 57 TRANS. AM. CER SOC . VOL IX PUROV ANDlWOORE. Plate xxk 2Ji 2J ^ H S^ "V, 1 22 ~ ! 1 ! — >- 1- i 1 o o 16 ~ — - t (^ F 2» < ,OME or .f VSION 2J LJ 14- oto oo 0<> 04- OZ. I 3 5 TEMPERATURES. EXPRESSED IN CONES Curve showing changes in specific gravity of clay F 21, at different temperatures. 58 PYRO-CHEMICAL AND PHYSICAL BEHAVIOK OF CliAYS. TRANS AM CER SOC VOL. IX PWRDY AND MOORE. PLATE! XXlll * rx \ \ \ ^ \ T 1^ V N w ^ i^ *"**4 V4- NO a FIRE CLAV TEMPERATURES. EXPRESSED IN CONES Curve showing changes in porosity of clay V 4, at difEerent temperatures. PYRO-CHEMICAl. AND PHYSICAL BEHAVIOR OF CLAYS. 59 ( 2i TRANS AM CE R SOC VOL K 1 — PURDV f kNO M0< OPC. PL^ sTE XXW 2 J > > o o u Q. 19 1 V A- — CO HE or FUSION NOT AT TA INC ° V* TEMPERATURES. EXPRESSED IN CONES Curve showing changes in specific gravity of clay V 4, at different temperatures. PYBO-CHEMICAL AND PHYSICAIi BEHAVIOB OF CLAYS. 61 NUMBER THREB FIRE CLAYS. In the following ten pages are shown the porosity and specific gravity curves of a class of clays which in the judgment of the writers, ought to be put in a different catagory from the preceding group or number two fire clays. Heretofore, both have been classified together in- discriminately in ceramic and geological literature, as number two fire clays, but they are not the same. Clays of this class differ from the No. 1 and No. 2 fire clays, in that they seldom have a fusion point exceeding cone 16 or 17, fuse in a very irregular manner, and exhibit a much larger decrease in specific gravity owing to the presence of iron in nodular form as sulphides or carbonates. 62 PYRO-CHEMIOAI. AND PHYSICAI- BEHAVIOR OF CLAYS. TPANS AM CER SOC VOL IX PuROV AND .MOORE PLATE, xxv ■4-0 (0 1- z u 1 u a a r [V \ UJ If) > \ i u X a )<; u .20 >- \ \ . i \ j \ 1 o Q. \ ^ ^ ' r\ \ \ 1 \ F7 N4 3 FIRE CV.AV CONE CP FUSION 1* \ \ \ k. ^^^ p C TEMPER/KTTJRES, EXPRESSED IN CONES Curve showing changes in porosity of clay F 7, at different temperatures. PYRO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. 63 TRANS. AM. CER 50C VOL ix: PUROY AND MOORE. Plate xxvi < >«». N -^ k 2* 1 \ N ^^^^■■■^o /I > u o u a o r- F7 — ' 4> Nv^ J rir\L ».l_/-\T ( .ONL OF F L/SlOM lA ^ OlO Oa C«> O* 02- I 3 i 7 9 TEMPCRATURE.S EXPRESStD IM CONES Curve showing changes in specific gravity of clay F 7, at different temperatures. «4 PYBO-OHBMIOAIi AND PHYSIOAI. BEHAVIOR OP CLAYS. TRANS AM CER SOC VOL. IX , PUROY AND MOORE PLATE XXVll h z r — kv (£ JO Q. k. Z 1 \ Q bJ a. a. N Nil V, ^^ k. \ >- h \ o or \ A o 0. \ \ lO \ ^ \ (T sn NO. 3 FIRE CLAY CONE OF FUSION £9 \ > N ^ -J « c 10 o 8 6 4- c >2 i 5 7 9 1 TEMPERATURES. EXPRESSED HN CONES Curve showing changes in porosity of clay F 20, at different temperatures. PYRO-CHEMICAL AMD PHYSICAL BEHAVIOR OF CliAYS. 65 TRANS AM CER. SOC VOL. IX PURDY AND MOO«£.. PLATE X, ^- \ <^ ^****-^ 2S \ \ k^ > o o u a IT) ,T F20 MO 3 FIRE CLAY CONE OF FUSION Z» Cunre showing changes In specific gravity of clay F 20, at different temperatures. 66 PYRO-CHEMICAL AND PHYSICAL. BEHAVIOR OF CLAYS. TRANS AM. CERSOC VOl_ IX PURDV AND MOORE PLATE XXIX TEMPERATURES, EXPRESSED IN CONES Curve showing changes in porosity of clay K 12, at different temperatures. PYBO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. 67 TRANS AM CER SOC VOL IX PURDY AND MOORC. PLA'rt XXX ^ f ^ \ It N V \ \ i r \ 1 \ N u. o 5,. Ik K12 vJO 3 FIRE CLAY f 1 * .0 o a o «> o * o z s 5 9 > TEMPER ATURE.S. EXPRESSED IN CONES Curve showing changes in specific gravity of clay K 12, at different temperatures. p. & M.— 6. 68 PYBO-CHBMICAL AND PHYSICAL BEHAVIOR OF CLAYS. TRANS AM CEP SOC VOU IX PUROY AND MO0f?E,. PLATE XX 1 h 7 u ■z J J ^^ Q in s kv. 1 1 CO u 1 k^ w 20 >■ ^ V \ ^ \ 1 \ to 1 1 \ ^ 1 V R 1 NO 3 RRE CLAY , ^ o 1 TE.MPERATURE.5. O'-PRESSEO IN CONES Curve showing changes in porosity of clay R 1, at different temperatures. PYRO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYB. l69 27 TRANS AM CI IR. SOC VOL IX 1 1 PUROY AND MO ORE. PLATE XKXl 1 t :,. — . K 2- \ ^ »__ 12 > I'' 1 1 1 ^7r 1 I o Q. .A R I0.3 FIF 1 JE CLA^ ' 1 4- f ! OlO OS Ofe 04- 02 I J 5 TEMPERATURES. EXPRESSED 'N CONES Curve showing changes in specific gravity of clay R 1, at different temperatures. 70 PYRO-OHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. TRAMS AM CEP SOC VOL X PURDY AND MOORE. PLATE XXXItl 1 1 1 ! j - . AO i 1 1 h Z UJ in O \ k 1 o a \ > k 10 \ > P"^**^ V5 tvJO 3 FlRE CUAV CONE OF FUSION 31 N \ T) 06 O* OZ I 3 _ TEMPERATURES EXPRESSED IM COMES Curve showing changes in porosity in clay V 5, at different temperatures. PYBO-CHBMICAL^ANO I'HYSICAIj BEHAVIOR OF CLAYS. 71 i7 TRANS AM CE R SOC VOL. \X PUROV AND M OORE, PL -ATE XXX V ( 2* > kl ^^ \ , ^^ i — - ^N -^ > h o o o u 18 . 1 V 5 CONE or rtlSlON 31 08 Ob TEMPERATURtS, EXPRESSELO IN CONES Curve showing changes in specific gravity of clay V 5, at different temperatures. 72 PYRO-CHEMICAL AND PHYSICAL BEHAVIOB OF CLAYS. SUMMARY OF FIRECLAY GROUP. The manner and amount of decrease in porosity and specific gravity between these three groups is quite marked. Similar curves drawn from data obtained on clays other than those here reported, exhibited similar differences. In the laboratory the clays were known only by sample num- ber, the field data being ignored to prevent possible preju- dice, but in no case did the inferred "possible uses" of the clay disagree with data obtained in the field concerning their commercial use at the present time. So far then, as the evidence thus obtained is concerned, it can be stated that this method of classifying fire clays has succeeded where other methods have failed. PYBO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. 73- PAVING BRICK SHALES. The standardization of tests for first class paving brick clays has been and perhaps will be for some time ing brick clays has been and perhaps will be for some time the subject of much consideration by ceramic investigators. The tests here reported can be said to give negative rather than positive information, in that they very effectively differentiate the clays that cannot from those which may be utilized in paving brick manufacture. Judging from the results so far obtained, they fail, however, to differentiate the paving brick clays one from another in regard to their comparative quality. For example, we have not been able to distinguish by these tests between the clays of 14% type and the 24% type, measured in percents of loss in the ratt- ler test, nor between the clays that preserve their maxi- mum strength through a wide heat range and those which attain and preserve their maximum strength only within a very narrow heat range. The cause of failure of the pyro-chemical studies in this respect is, no doubt, to be found in the fact that inher- ent strength is not wholly a function of rate of vitrification or development of vesicular structure. Tensile strength of the raw clay, fineness of grain, and many other physical and chemical tests have been made on paving brick clays in order to determine the relation between their properties and the strength of the burned ware, but after a study of 25 paving brick clays from different states, it has been found that but very little relation exists. The pyro-chemi- cal studies here reported are the only ones that give any clue to the toughness or strength of the burned ware. Pyro-chemical studies similar to those here outlined,, together with a determination of the maximum strength and the range temperature in which this maximum strength is developed, would enable the observer to pro- perly classify and differentiate paving brick clays. This, however, amounts to a sub-classification of the paving clays on a basis different from that of the main sub-divi- sion. The following are typical porosity and specific gravity curves for clays of the paving brick type : 74 PYRO-CHBMICAL AND PHYSICAL BEHAVIOR OF CLAYS. TRANS AM CER SOC VOL. IX PUROY AND MOORE,. PLATE XXX f i 1 ill! 1 i <0 1 ^ i i z -UJ « Ui a z ^*Vj ^-^. i 1 ^ \ : , i \ 1 ■! o Li \ ! 1 ! a. N ^ 1 1 a \j ! ! i y t 10 o o: o Q. Nj t 1 - 1 i ^ >vl i\ i «0 \ 1 \ 1 K6 -WING BRICK SHALE BATTLER LOSS L3 2S \ " p \ \ \ L ._ S TEMPERATURES. EXPRESSED IN CONES Curve showing changes in porosity of clay K 6, at different temperatures. PYRO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. 75 TRANS AM CER 50C. VOL IX PUPDY AND MOORE. PLATE XXHV ■ i ■ ^^ X \ \ > !■■ K o bi a. \ \ , K6 PAVIMG BRICK SHALE Rattuer loss 13 25 1 ♦ OtO on Te.MPEr?ATURES EXPRE^StD IM CONES Curve showing changes in specific gravity of clay K 6, at different temperatures. 76 PYRO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. '80 ^TRANS." AM CeR SOC • VOU' IX . puRDv AND t^ooRC, Plate xxxvii ""^^^ ■ — ^ "*'*^ 1 \ \ \ \ \ \ \ 1 \ \ \ R3 Paving brick shale »»ATT(.E« Los» i*.eo \ ' \ r\ "V*^ 5 06 O* 04 02 I 3 67 9 TEMPERATURES, EXPRESSED IN CONES Curve showing changes in porosity of clay R 3, at different temperatures. PYBO-CHEMICAL, AND PHYSICAL BEHAVIOR OF CLAYS. 77 TRAN5 AM CER SOC, VOL IX PURDY AND MOORE. PLATE XXXVMI - _ t i [N. N V \ \ \ Of y u Q. • R3 PAVIN6 BRiCK SHALE RATTLER LOSS U* tO. 1 . om 06 CO 04 TEMPERATURES. EXPRESSED IN CONE: Curve showing changes in specific gravity of clay R 3, at different temperatures. 78 PYRO-CHEMIOAL. AND PHYSICAL BEHAVIOR OF CLAYS. TRA-rJS ^M CER SOC VOL IX PURDY AND MOORE PLATE XXX rX 1 i ! ! \ N >> K^ ^*«*^ r"*^ ^ \ \ > \ \ \ \ \ 1 \ K 1 PAV1M6 BRICK SHALE 1 P^^ ^> i\ i \ ^ TE-MPERATURES, eXPR£.SSEO IN CONEJS Curve showing changes in porosity of clay K 1, at different temperatures. PYBO-CHEMICAL, AND PHYSICAL BEHAVIOR OF CLAYS. 79 TRANS AM C ER SOC VOL IX PURDV AND moors: plate XL < 2£ -^ ^ L [ Zi Z* — X 2J a. —A k ^-n O U Q. te 1 " — K 1 "~ _ f lATTLER L< 3SS 15 8: J L* oio oe 06 o* oz telmperatureg expressed in cones Curve showing changes in specific gravity of clay K 1, at different temperatures. 80 PYRO-OHEMICAIi AND PHYSIOAL BEHAVIOR OF CLAYS. 30 TRANS AM CEP SOC VOL IX PUROV AMD- MOORE. Pl_ATE XV.I ■ *0 \ \ J1 h Z u 1 \ IL N r ■ \ o u (t . Q. X \ N \^ \. L )- "V r\ O \ l\ \ \ (O \ \ J 2 PAVING BRICK SHALC RATTLER LOSS \-r lA V • V \ N^ ^^^ ^^^^^ ^^ ) TCMP£RATURES. EXPRESSED IN COINE3 Curve showing changes in porosity in clay J 2, at different temperatures. PYBO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. 81 TRANS AM. CER SOC VOL X PURDV AMD MOORE. Plate: xlh 16 23 p^ r - ■^ 2* t i 22 > h a o — — k. \ ^ o Id a \c 1 J 2 — R ATTLER LC )SS IT \A ^ L* OlO oa Otj 04 O? I J i> 7 9 II TFtVlPERA-TuRrS EXPRET.SED IN CONES Curve showing changes In specific gravity of clay J 2, at different temperatures. 82 PYRO-OHEMICAL, AND PHYSICAL, BEHAVIOB OF CLAYS. TRANS AVl CZ.R SOC VOL IX PURDV AND tv.CORt. P'-^TC: XUMI i 1 ! ! 1 1 i 1 ! i 1 i i 1 1 : ! t i 1 1 [ — ^ ^^ X n ^ i X ! \ 1 1 \ i i I I 1 ''"^—1''^ \ i i 1 \ 1 \ i \ ! n \ R2 AVING BRICK SrtAL *.TTi.ER uCSS ITS \ 1 F E \ i 1 " \ 1 1 ^ ! V 1 1 • ^ 1 1 010 Oe 06 04- 02 I 3 5 TEr-IPERATURES EXPRESSED iN CONE: Curve showing changes in porosity of clay R 2, at different temperatures. PYKO-CHEMICAIi AND PHYSICAL BEHAVIOR OK CI.AVS. 83 TRAN3 AM CtR SOC VOL IX PURDY AND MOORE. PU^-TE XUIV ( 3 ^^ --- ^ k \ V i N V \ \ \ \ » R2 PAVIN6 BRICK SHALE RATT1.CR LOSS IT 80 A TEMPERATURES. EXPRESSED IN CONES Curve showing changes in specific gravity of clay R 2, at various. temperatures. p. ft M.-6 84 PYRO-CHEMICAL AND PHY8ICAL BEHAVIOR OF CLAYS. TRANS . AM. CER. SOC . VOL. IX PUKDV AND MOORc. PLATE KLV V ,1 l^^^^^* N ^ < \ N i V \ \ 20 ^ ^ L \ \ \ \ 10 \ \ PAVIN6 BRICK SHALE RATTUER LOSS IS. II \ > L V ^ X 1 o >o c « o « ^ 2 3 5 7 i t TEMPERATURES. EKPRESSED IN CONE3 Curve showing changes in porosity of clay K 4, at different temperatures. PYRO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS, 86 TRANS AM CER &OC VOL IX PURDV AND MDORE, PLATE XLVt \^ 2.6 2* 23 22 > \ ^ k \ \ \ V \ IL 111 \ lb K4. PAVING BRICK SHALE <* » TEMPERATL/RES, EXPRESSED IN CONES Curve showing changes in specific gravity of clay K 4, at different temperatures. 86 PYRO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. TPAKJS •AM CCR 50C VOL 'X PU RDV AND MO ORE PL ^TE XLVI «« '^, u r ^ \ N^ z. N. 3- a: > k \ so >■ N 8 \ o 0. \ \ 10 . \ \ > , -^ > o IS - F 1 — BATTLER 1 .esa COS pj !♦ TEMPERATURES, EXPRESSED IN CONES Curve showing changes in specific gravity of clay F 1, at different temperatures. 88 PYRO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. TRANS. AM CER SOC. VOL," »>C PURDY AND 'MOORE. PLAXEXLIX ' ^ k \ N L ^1 '^'"^ ^^\ ^ \ \ \ \ \ \ 1 KI4- PAVING BRICK SHALE RATTLER LOSS 21 24- \ y V X N > OtO c 8 6 C * C 2 3 i 7 i I TEMPERATURES, EKPRESSEO IN CONES Curve showing changes in porosity in clay K 14, at different temperatures. PYBO-CHEMICAL AND PHYSICAL, BEHAVIOR OF CLAYS. 89 TRANS AM CER SOC k/OL IX PUROV AND. MOORE. PLATE L \ \ i \ \ N ) K14 PAVIN6 BRICK SHALE RATTLER L^aS 21. ai CIO oe ot o 0^ I J s TEMPERATURE5. EXPRESSED IN CONES Curve showing changes in specific gravity of clay K 14, at different temperatures. 90 PYRO-CHEMICAL AND PHYSIOAL BEHAVIOR OF CLAYS. TPANS. AM CER SOC VOt-. IX PUBOV AND MOORE P> -ATE LI *0 rx > I Q. JO a) a. \ z \ Q (0 \ in u \ X 20 > H V 1^ X \ \ o a o \ . \ \ ^ ) S I PAVING BRVCK SHALE Rattier loss C6 23 o I TEMPERATURES. EXPRESSED IN CONES Curve showing changes in porosity in clay S 1, at different temperatures. PYKOCHRjrtOAT, AND PHYSIOAIi BEHAVIOR OF CLAYS. 91 tt TRANS . AM CER SOC VOL IX PUROY AND MOORE. PLATE LH < "\ = hN 23 > q: o \ ) o y a. 19 18 < 5 1 PAVING BRICK SHALE RATTcEB I.033 ee. 33 4 » TEMPERATURES. EXPRESSED IN CONES Curve showing changes in specific gravity of clay S 1, at different temperatures. 92 PYKO-CHEMICAL AND PHYSICAL BEHAVIOR OP CLAYS. The chemical composition of the above clays are as follows :^ Sam. No. Mois- ture Vol'til' matter SiO, Al^Oj fe.O, CaO MgO KNaO FeO TiO, R 3 1.06 5.95 58.57 20.40 7.40 0.63 1.37 3.27 R 2 1.29 4.86 63.41 18.61 5.82 0.41 1.16 3.60 J II 1.98 6.76 62.70 16.95 8.98 1.19 1.47 3.03 F 1 2.02 7.72 58.52 15.67 4.99 1.05 1.45 4.42 3.37 0.96 K 1 0.48 6.99 63.36 15.43 1.80 0.93 1.58 3.84 4.02 i.oa K 4 0.51 5.47 64.09 14.16 2.65 1.69 1.64 3.67 3.16 0.89 K 6 0.38 5.88 63.62 16.28 3.02 0.63 1.44 3.10 2.90 0.96 K 3 0.29 7.89 59.34 15.36 3.26 0.76 1.82 4.62 3.84 1.31 K 14 0.51 6.47 64.09 14.16 2.65 1.69 1.64 3.67 3.16 0.89 Calculated into molecular ratios, the above analyses reduce to : Sample 1 Number | CaO MgO KNaO Fe,0, AljOj SiO, FeO 1 TiO„ R 3 0.056 0.171 0.209 0.231 1.00 4.88 R 2 0.040 0.159 0.253 0.199 1.00 5.79 J II 0.125 0.221 0.234 0.378 1.00 6.29 F 1 0.122 0.236 0.359 0.203 1.00 6.35 0.305 0.078 K 1 0.110 0.261 0.290 0.074 1.00 6.98 0.369 '0 . 083 K 4 0.042 0.282 0.277 0.181 1.00 5.78 ■0.156 0.060 K 6 0.070 0.225 0.325 0.118 1.00 6.64 0.252 0.075 K 3 0.090 0.302 0.356 0.135 1.00 6.57 0.354 0.108 K 14 0.217 0.295 0.311 0.119 1.00 7.69 0.309 0.080 The mechanical analyses^ of the above clays are as fol- lows: Sample Number L'gerthan 1 m. m. m. m. 0.1-0.01 m. m. 01-0.001 m m. 0.001-0 m. m. Total Surface fac- tor by Pur- dy's method R 3 11.695 6.302 52.902 21.605 11.791 104.295 290.67 K 1 7.276 6.534 56.078 24.861 9.766 104.515 256.476 K 4 1.402 1.744 48.875 29.416 22.242 103.68 513.508 K 6 1.241 1.832 65.836 25.984 7.772 102.666 220.596 K 3 1.500 2.413 57.155 25.148 13.968 100.18 341.155 K 14 H.331 6.311 42.751 25.035 9.672 98.999 254.354 •Analyses by Professor S. W. Parr, University of Illinois. »By J. F. Krehbiel and J. K. Moore. PYKO-CHEMICAL AND PHYSICAL BEHAVIOR OP CLAYS. 93 The rattler losses as determined on the commercial product of these clays,^ obtained direct from the factories, are given in the following table, b, c. d. and e. signify re- spectively, Soft-burned, No. 2 or "Alley" grade, No. 1 Paver, and Over-burned. Sample Number Total Rattler Loss at end of Absorption in per cent 1 Tranverse Modulus ot Rupture 600 Revolu. 1200 Revolu 1 1800 Revolu. R 3 8.74 12.22 14.80 1.27 2800 R 2 9.76 14.78 18.61 2.21 2505 450 900 1350 1800 Revolu. Revolu. 1 Revolu. |' Revolu. | 2.315 J II 8.43 12.25 15.11 17.14 2220 Fib 19.32 29.31 38.88 46.67 13.2 c 12.70 19.81 25.08 30.15 4.8 1700 ' d 9.13 13.89 17.64 20.84 2.8 1980 e 9.75 17.20 23.22 28.35 1.7 1670 K 1 b 17.37 28.56 39.96 46.06 11.2 c 13.28 21.46 28.20 33.91 6.1 1630 (1 8.43 11.50 14.08 15.82 0.9 2535 e 9.42 16.15 21.77 26.99 1.2 1420 K 4 b 19.69 30.60 38.17 45.12 12.20 980 c 9.22 14.47 17.00 19.94 5. '00 2360 d 9.91 14.18 16.87 19.11 1.16 2250 e 14.83 18.92 broh en up 0.60 1890 K 6 b 7.9 13.36 18.20 22.77 c 7.5 11.68 15.40 18.33 d 5.84 9.06 11.58 13.25 e 8.42 12.85 16.52 20.32 K 3 b 18.54 29.53 38.35 46.21 10.0 995 c 11.34 17.45 21.23 24.61 3.5 2100 d 12.69 19.01 22.49 24.89 1.05 2350 e 11.07 18.58 23.11 26.42 0.70 2700 K 14 d 8.35 13.35 17.30 20.79 4.218 1617 'By Professor A. N. Talbot, University of Illinois. 94 PYRO-CHEMICAIi AND PHYSICAL BEHAVIOR OF CLAYS. The writers confess their inability to correlate the chemical and mechanical analyses of these clays with their pyro-chemical behavior or their rattler loss, but since they represent the most commonly accepted facts which have been collected heretofore in the study of paving brick clays, they are here recorded for reference. PYBO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. 95 COMMON OK HUILUING BRICK SHALES. Typical porosity aucl speeilic gravity curves of this class of clays are given in the following six charts. The striking difference between these and the paving brick shales is apparent. Earlier vitrification, irregularity in decrease of porosity and specific gravity, apparently larger quantity of vesicular glass formed within the mass, or at least a more notable bloating, due to volatilization of certain constituents, probably the soluble and adsorbed salts, are the distinguishing features of this class. Sufficient evidence is at hand to warrant the state- ment that any clay which vitrifies to a porosity of 2 or 3 per cent, before cone 5 is reached in the heat-treatment pre- scribed in this method of burning test pieces, will be too brittle for use as paving brick material, no matter how little vesicular structure is developed. The fact is, how- ever, that it will be a rare case in which vesicular struc- ture is not strongly developed, if the clay shows an early and rapid rate of vitrification. The use of the comparative terms "early" and "rapid" in reference to this type of clays in contrast to their rela- tive use in regard to fire clays, is best illustrated by refer- ence to the curves. While the writers admit that the evidence here pre- sented is too meagre to permit of a complete or satisfactory plan of classification, they do feel that it is sufficient to indicate that a classification on the basis suggested is more rational than any other heretofore presented. 96 PYRO-CHBMICAL AND PHYSICAL BEHAVIOR OP CLAYS. TRANS AM CER SOC VOL IX PURDY AND MOORE. PLATE Ull «0 tr,- r z hJ V) U X t o r\ ^ \ \ \ 10 \ \ FS COMMON BRtCK SHALE \ L^ p TEMPERATURES. EXPRESSED IN CONES Curve showing changes in porosity of clay F 8, at different temperatures. 1 PYKO-CHEMICAL AND PHYSICAIi BEHAVIOR OF CIiAY8. 97 TRANS AM. CER SOC VOL IX PURDY AND MOORE, PLATE UIV ( \ \ \ i \ > N ^ f \ o a. I0l9 • \ ) F 8 COMMON BRICK SHALE t4- O>0 OS 06 O*^ 02 I 3 i TEMPERATURES. EXPRESSED IN CONES Curve showing changes in specific gravity of clay F 8, at different temperatures. 98 PYRO-CHEMICAIi AND PHYSICAL BEVAVIOR OF CLAYS TRANS AM CER SOC VOL. rx PURDV /AND MOORE PLATE LV ■ ' N N ^ N. \ V \ \ lO \ \ F9 COMMON BRICK SHALE ^ k N i< V o TEMPtRATURES. EXPRESSED IN CONES Curve showing changes in porosity of clay F 9, at different temperatures. PYRO-CHEMICAL AND PHYSICAL. BEHAVIOR OF CLAYS. 99 TRANS. AM CER. SOC VOL. IX PURDY AND MOORE. PLATE UVI < 2^ ^ at I o " \ 1 F9 COMMON BRICK SHALE 1 • 4 1 [ 1 oio 06 Ob o* oz I J .; TEMPERATURES. EXPRESSED IN CO:Jf:; Curve showing changes In specific gravity of clay F 9, at different temperatures. 100 PYRO-CHEMICAL AND PHY8I0AI. BEHAVIOR OF CLAYS. TRANS AM. CER SOC VOL IX PURDY AND MOORE. PLATE. LVII j 1 1 ] jv \ \ \ 1 \ \ \ FIO COMMON BRICK SHALE \ 1 \ L..^ 1 — r TEMPERATURES. EXPRESSED IN CONeS. Curve showing changes in porosity of clay No. F 10, at different temperatures. PYBO-CHBMIOAL AND PHYSICAL BEHAVIOR OF CLAY8. 101 TRANS AM CER SOC VOL IX PUROV ».ND_'M0OREJ PLATt LVIII > ( ^^ \ \ N > 1" iZ o UJ 0. \ \ \ ^ \ FIO COMMON BRICK SHALE \ \ \ OlO 06 Ofc CM- 02 I TCMPERATURES. EXPRESSED IN CONES Curve showing changes in specific gravity of clay F 10, at different temperatures. p. & M— 7. 102 PYRO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. COMPARATIVE THERMO-PHYSICAL CHANGES. The following curves are presented to show the com- parative rate at which the three most important thermo- physical changes take place. A full explanation of the method of plotting these curves has been given earlier in the text. The volume, porosity, and specific gravity of the dry unfired brick being considered as a basis, and plotted in the datum line, the co-ordinate points of increase or de- crease of these same factors in the burned brick are plotted as shown on the curves. PYRO-CHEMICAL AND PHYSICAL BKHAVIOR OF CLAYS. 103 ^ / J a. u 1 1 /I / / o 8 ^ 1 1 in : / / o k^ • <»-i H -*J u. CI f> ■y '" / UJ 1 > >?6 KiOliiaNOO IVlilNi lAjOaj ■3SV3M030 ONV 39V3aONI JO 3<3VX»g30a3d O C CO -!-> dj o 104 PYRO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. X _) u (J M 1 1 1 1 il 11 1 u 1 is 1 ! 7 j^ 1 i j < 1 > \ I 1 ! O • f IT 1 j' i D. J 4 i 1 f j / / CM ^ / — 1 ■) y '•J 1 / 1 X / \ J o / J • 1 1 I \ < «) 7 < Of 1 1- ' o ii a . O OS > m n o ii '- s^ < .2 o 4 \j JO !?5 S^ « o o S O O PYKO-CHEMICAL AND PHYSICAL BEHAVIOR OF CLAYS. ]()5 X J • C? • 1 UJ ^ ji 1 \ ^ x^! f a. 1: 1 1 o o ^; 1 1 1 o % < jf >- 1 / u 1 a. • / a. 1 / i / I / f / 1 / / / / • / y /^ / ^ i ^/ ^^^ >^ ^y^ / I / i f o / \ tfl / %' / \\ \ UJ ii ? • < { IT /■ < «r h s -- .. •g o 5 NOIXIQKOD "IVIXIMI IMOaj ■aSV:3a03a aSlV 3SV9aONI JO 3 ^ a o 106 PYRO-CHBMICAL. AND PHYSICAL BEHAVIOR OF CLAYS. >< J y 1 j i / < J a 1 ^ ■^ v5; 1 / f J I < > o K 1 / 0. i % 1 1 ^ 1 / / / , r / / / / l/^ . ' ^ : 1/ 17 i_J V X /^ J f \ 1 5 1 1 i J ' i / o ■* 2 < 2 o ? a o D S^O 5S ID 53 'O ^ JP NOIXKDNOO TVUINI INOdd 39V3y030 ONV 3SV3yONIt JO 3OVXN30ii3d PYRO CHEMICAIv AND PHYSICAL BEHAVIOR OF CLAYS. 107 Si 5 5 !S » NOIXIQNOO "IVlXINl kNOyj 3'5V3iiD30 ONV BSVaa-SNI JO 3OVXN30aBd 108 PYBO-OHEMICAL AND PHYSIOAL BEHAVIOR OF CLAYS. Si 's o >« S i? 2 ^gvxNaoirad PYRO-CHHMICAL AND PHYSICAL BEHAVIOR OF CLAY8. 109 ^ M \ / 1 •i •0 If / j4 ? ^ 1 / i i \ t M y y^^- "1 1 — ^ / I (0 / 1 1 f 1 — — \ 1 \ i j o . ■aa o a ^5« < < u. O < h * u o 3 "O o9 bo a '$ o 3 o 110 PYRO-OHEMICAL AND PHYSICAL BEHAVIOR OP CLAYS. ULTIMATE FUSIBILITY OF CLAYS. Liidwig-,^ by the application of kiiown i^liysico-cheiiii- cal laws, deduced a scheme by which he was able to predict the fusibility of clays. H. J. Robertsoii,^ discussing Lud- wig's results quite fully, concurred in his general conclu- sions. The Ludwig scheme as presented by Robertson was followed in the construction of the chart on page 313. The Seger cone molecular formulae were reduced to Al203=l. The molecular equivalents of silica were plotted on the ordinate, and the molecular equivalents of RO fluxes on the abscissae. It will be noted that in no case does the molecular ratio of AI2O3 to SiOa exceed 1 :10. This being the ratio of AI2O3 to SiOg in cones 5-25, their co-ordinate position is located on a horizontal line drawn from the or- dinate 10. Having the chemical composition of clays of various kinds, the chart was prepared and the co-ordinate position of each clay plotted. The accuracy with which the fusibility of a clay can be thus ascertained, is shown by the fact that in nearly every case, the result reached by plotting the molecular ratios checked with that reached by the actual fusibility test, regardless of the purity or grade of the clay tested. The labor of making the analyses and calculating the molecular formulae, and the chances of disagreement be- tween the plotted and actual fusibility, places the Ludwig scheme at a serious disadvantage. Inasmuch as direct tests afford an easier and surer method, Ludwig's indirect test will hardly come into general use. The Ludwig scheme, however, has been of great value in that it has established the fact that clays, although a heterogeneous mixture of minerals, do, as a rule, obey definite laws in fusion. ^Tonindustrie Zeitung No. 63, 1904, abstracted by Prof. Bleininger, Vol. VII, p. 275, A. C. S. Trans. 'Brick, Vol. XXV. No. 2, 1906, p. 62. PYRO-CHEMICAL, AND PHYSICAL BEHAVIOR OF CLAYS. Ill o *' I «- ^0 N- =^0 u. u. (C- zo (Ti-. ^J ^ Z-. .,W CQ lU. ■J, >c ^ 0- 4. S^ ^, t-" «>- *-« 8- JW. <\) *- -a ■o id- 'g >o K a> (Ji _ fj s /'" s V V \ I \ I z i:S 1 _ P^ ? D '?^ fl-J ^ < cd •3 |;€|.6 o z e3 . <: 00 g 121 (0 ^'3 UJ ^ fl >< 2 O 1-113 S 'S _/ .2 li. ^4 VH f T1 11 J " o < O tH ._ a) «>o\^ •sl Z a. a !:eOiiJ « 2 u 9 -^ uou - S .r.^ ^r >^/:^i^'^>^- •^^ UNIVERSITY OF ILUN0I9-URBANA 3 0112 052567101 ^*N»