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UNIVERSITY OF ILLINOIS BULLETIN

Vol. V. AUGUST. 17, 1908 No. 39a

[Entered February 14. 1902, at Urbana, Illinois, as second-class matter under Act of Congress of July 16th, 1894.

BULLETIN No. 7. DEPARTMENT OF CERAMICS

C. W. ROLFE, Director

THE INFLUENCE OF FLUXES AND NON-FLUXES UPON

THE CHANGE IN THE POROSITY AND THE

SPECIFIC GRAVITY OF SOME CLAYS.

By A. V. BLEININGER and J. K. MOORE

I 907 - I 908

PUBLISHED FORTNIGHTLY BV THE UNIVERSITY

THE INFLUENCE OF FLUXES AND NON-FLUXES UPON

THE CHANGE IN THE POROSITY AND THE

SPECIFIC GRAVITY OF SOME CLAYS.

BY

A. \'. Hli:i.\in(;i:u and J. K. Mooin:. Chainpaifiii, IIL

\'itTitication may be said to be ])artial fusion. Wlion speakiiij; of clays the pronrcss of vitriticatiou is iM]uivaleiit to pro«»Tessive, partial fusiou of the various luincral coii- stitiiciits, «>ov(tii(m1 by the iiiiiiei-al constitution of the body as a whole, the size of urain and the strucrure of the ware for which the clay is employed. ('om])lete vitriticatiou ensues when enough (day has been used to till u]) the ])ores oi'iiiinally pi-esent. Fi'om the ])ractical stand])oint this is indicated by the fact that but little water is absorbed by the (day on immersion. Without lioin.u fully into the de- tails of the process it may be said that the ])henomena of fusion accomi)any the vitrificatioii of clays.

Fusion considered from the .ucneral siandi)oint of sili- cates is sharply defined only for some definite minerals; even in many silicates it is a more or less gradual transi- tion from the solid to the semi-liquid or li(iuid condition, and therefore, in a hetero_u-en(M^us rock, like (day, even thou|L»:h all of its constituents were reduced to uniform, extreme fineness, fusion must, in the nature of the cas(\ cover a considerable tem])erature interval.

From tlie practical standpoint, tln^refore, vitrification may be followc^d by determininu the i)orosities at dilferent temperarures. just as Prof. Purdy has done in his valuable contribution in Vol. IX of the Transactions of this Society.

In addition, two ])henomena of fusion demand our at- tention. Tliese are (losely r(dated and are: ('han.iie in molecular voluuu' and transference of heat. In nearly all silicates the volume is increased on fusion or, ij) other

4 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGE

words, the density is decreased. Tliis iucrease in volume is intimately connected with the fact that the amorphous or fused condition represents a greater energy potential than the crystalline state. AVe find, as a rule, that the amorphous modification of a substance is more soluble and capable of stronger reaction than the anisotropic form. That fusion results in an increased volume has been deter- mined frequently, and in a few cases it was even possible to establish this fact for minerals in the fused, liquid con- dition. Thus Doelter found the specific gravity of crys- talline augite to be 3.3, that of the hot, liquid mass 2.92, and of the solidified glass, 2.02. The so-called coefficient of crystallization, in fact, is determined by the specific gravity of an intermediate stage compared with the specific gravity of the crystal. If dx=specific gravity at any stage and dc^specific gravity of the crystal, dx-^dc==coefficient of crystallization. E. V. Fedorow has shown that this agrees with the facts.

With reference to the heat of fusion we can say that this is of constant magnitude, and is equal to about 100 gram calories per gram. Fusion is always accompanied by absorption of heat. This is a necessary conclusion, for in fusion, work is always done against the external pres sure and the cohesion of the particles, both of which tend to oppose the increase in volume. That the non-crystalline condition corresponds to a higher level of energy may be indirectly shown by experiments such as the determination of the heat of solution. Thus 1 gram of crystalline sodium silicate evolves 457 calories, while the same amorphous substance gives off 486 calories. Similarly, crystalline leucite sliows 507, the amorphous substance 533 calories.

From what has been said it follows that crystallization shows the opposite characteristics. On crystallization the volume decreases and heat is given off, thus r(?tarding the cooling of the mass.

The fact that clay bodies decrease in density on vitrifi- cation had been realized quite early by Laurent, Krong- niart and Rose, and during the last decade has been used

IN THE POROSITY AND THE SPECIFIC GRAVITY OP SOME CLAYS. 5

ill very exact work by Day and Shepherd, Mellor and oth- ers. The rate of change in specific gravity and porosity lias been enipb)ved in the ])lotting of density and porosity curves by Berdel in his excellent and extensive work on white ware bodies and, later, by Purdy in his work already cited. Piirdy eni]th;»sizes the rate of chan^'e in porosity and makes use of the specific gravity only for the purpose of determining the porosity which he considers as the cri- terion for judging the ])rogress of vitrification, lie calcu- lates the porosity, expressed in per cent, frtmi cla^^ brick- ettes burnt at different temperatui'es and uses the formula:

% h:^s)'»«.

where % P^per cent porosity, W=wet weight of brickette. D=dry weight. S=suspended weight.

The wet weight corresponds to the weight of the brickette after immersion in water, in vacuo.

By plotting the porosities of a clay at different tem- peratures he obtains a curve which un«inestionably indi- cates the progress and rate of vitrification. Prof. Purdy advocates the use of such curves in clay testing for the purpose of determining the character of a clay, and there is no doubt but that this offers a very convenient and valuable method of testing which deserves general applica- tion. The writers make continuous use of the method in carrying on clay tests.

While the porosity curve is of great practical value, yet it seems to the writ<M's that mnch information in regard to the mechanism of the changes occurring in clay during burning is obtained from the ])articnlar study of th;^ changes in s])ecific gravity, that is, the s])ecific gravity curves. In using this method we ai'e sim])ly adopting the means employed by many investigators in following chemi-

D THE INFLUENCE OF FLLXES AND NON FLUXES UPON THE CHANGE

cal trau.sformatiou, as, for instance, by Van't Hoff in his study of plasters, etc.

While in many clays and clay bodies the porosity and specific gravity curves are practically parallel, yet it may happen that certain changes occur which are indicated onl\ by the specific gravity curve.

In discussing the density of clays we must clearly dis- tinguish two values of the density which differ according to the method by which the work is carried out. If we take a brickette, weigh it when dry, immerse it in water, in vacuo, and again weigh it suspended in water, we obtain by calculation from the simple formula :

Dry weight in air Specific gravity=

Dry weight in air — suspended weight,

the specific gravity of the brickette as a whole, including the effect of enclosed pores and other cavities. On the other hand, by crushing and powdering the brickette and using the pycnometer, being careful to exhaust the air from the powdered material and water in the apparatus, we shall have the specific gravity of the burnt clay itself, the effect of the pores and cavities having been eliminated.

In addition to the change in volume brought about by fusion we have other voluiue transformations caused by so-called inversions, that is, the character of the molecular arrangement of many compounds suffers an alteration. The best known instance of this kind of transformation is the change of quartz into tridymite. On filling a crucible with pulverized cpiartz and heating it this change is mani- fested quite strikingly by the bursting of the vessel due to the increase in volume incident to this molecular change. This inversion

quartz "^ tridymite

occurs at about 800° C. Similarly it is found that fused quartz which necessarily is in the amorphous condition is transformed to tridymite, which is shown by the dim-

IN THE POROSITY AND THE SPECIFIC C;RA\ I IV OF SOME CI.AYS. I

iiiiii^ of tilt' iihiss. Since this cliaiiiie is rcvcrsihle it follows that below 800^ the tridvinite reverts to quartz. This latter fhantce is rather slu,a2:ish and requires <onsi(l(M*able time, we can say, therefoi'e, that ([uartz never crvstallizes from mineral fusions exeeptinc; in the presence of catalyzers. (Quartz* then, is the unstable foini of silica from 800' up- ward, and it will chanjic to tridymite whenever oi)por- tunity olfers. We have thus a volume change which on heatiiiii' a clay is shown by the decrease in density. Puri- fied natural (juartz has a s])ecitic «»ravity of 2.654 (25^), while tridymite ])repare<l from (]uartz has a density of 2.o2(>; when i>rei)ared from fused (|uarrz its density is 2.0I8. The density of quartz lilass was found to be 2.213. On coolinj; a clay any chanjie from tridymite to quartz stands for an increase in density, as must be evident from the above figures.

Similar inversions are known for meta and ortho cal- cium silicate. Thus we have the pseudo-hexajional nu^ta- silicate and wollastonite and three forms of the ortho calcium silicate. These are the al])ha, beta and gamma modifications whose densities are 3.27, 4.28, and 2.07, re- spectively. There are doubtless other inversions which are not yet known to us.

Still another source of volume chanjies is to be souiiht in chemical reactions takinii' place in clay, such as the exothermic reaction takinji' place in clay substance at about 1000, in which evidently an isomeric compound differinji' from the ])revious com])Osition in structure is formed. Other examples are the chanei? of calcium carbonate to the oxide, the interaction of lime and iron oxide, the formation (»f <-ertain lime silicates above 1200^, the formation of .spinels, majiuetic oxide, etc. There must be many chemical i-eactions which at present are entirely unknown to us.

In studyinji; the changes in the two specific jiravities, then, we miiiht be able to summarize the causes of the volume changes as follows:

*Day and Shepherd. Jnur. Am. Clicm. Sec. \'('\. 28, p. 1099.

8 THE INKLLENCK OF FLUXES AND NON-FIAXES IPON THE CHANGE

A. Apparent specific gravity. B. True specific gravity.

1. Inversion 1. Inversion

2. Fusion • 2. Fusion

3. Clieniical reactions 3. Chemical reactions

4. Pore space 4. Crystallization

5. Formation of "blebs"

6. Crvstallization.

A slight change common to both forms of specific gravity is that caused by the differences in the coefficient of expansion between the fused and crystalline portions. We observe, lience„ that the apparent specific gravity must be the algebraic sum of at least six and thee true specific gravity of four factors.

On lieatiug a clay body the changes taking place in quartz and feldspar and perhaps in clay substance, the character of which has been discussed before, tend to in- crease tlie volume or to decrease the density. We might say, therefore, that, in terms of tlie density, the change is — in character. On cooling the clay, however, during the critical temperature intervals of each constituent inversed, the density change is-ffor then the inversion, as far as reversible, proceeds the other way. But since the cooling nearly always takes place far more rapidly than the heat- ing up, it is quite probable that this change in volume is but slight.

We already know that the volume is increased on fusion and remains increased unless crysrallizatiqu takes place on cooling. The change in density on fusion, hence, is — as far as most silicates are concerned.

Chemical reactions may cause either -|- or — changes, but on heating, according to the theorem of Le Chatelier, the changes are probably — in sign, as a rule.

The pore space, still remaining in the clay which has not yet been closed up by the softened or fused material of course, tends to decrease the apparent density. The same thing is true of the blebs forniel by the evolution of

IN THE I'OROSnV AND IHK SPECIFIC- GRAVITY OF SOME CLAYS. VI

uasos within the chiy. This formation of gas is a vorv important factor in the meclianical strenoth developed in a elav, and this fact has been brought out very clearly by Purdy. In some clays the porosity thus contributed may be coincident with vitrilication and hence, althoujih the clay itself may be perfectly vitrified, the porosity curve would, in such a case, fail to indicate vitrification. Several such clays and bodies have been observed by the writers.

Crystallization would, in the nature of the case, take place only when the temperature has ceased to rise, that is. when the kiln is "soakin<»,"' the tenii)eratnre just holding its own or wlien coolino- begins.

That crystallization does take i)lace to some extent in clays is established beyond a doul)t. The senior writer in examining a section of paving brick which happened to show two well defined ar^as of properly burnt and over- burnt clay, found numerous crystals, neefUe-like in shape, in the over-burnt portion, but no evidence of crystallization in the sound part. AVegemann, in collaboi-ation with Prof. Purdy, found considerable crystallization in over-burnt ])aving brick, fine needle-like crystals, yellowish-green in color, of unknown composition as well as minute crystals of iron oxide. Crystallization, as we know, stands for decrease in volume or increase in density, and hence wo may say that it is a + change, in terms of the density.

The investigation which is the basis of this paper was cai'ried on for the purpose of determining tlie character of the changes in the density and porosity of clay bodies to which various reagents have been added, burnt at different temperatures, and it is due Prof. Purdy to say that it was inspired by his paper on the pyrochemical and physical changes of clays. It was proposed to broaden the scope of the work and to determine, if possible, the following (juestions:

1. To what extent do tlie apparent specific gravity and porosity curves agree in indicating vitrification in the study of various additions to clays?

2. If there are anv deviations where and liow do thev

10 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGE

occur, and ^\hat is their character? Are there aii}' maxi- mum or minimum points?

3. Under what conditions are certain substances fluxes, and when are they non-fluxes or refractories?

4. At what rate do these substances either accelerate or retard fusion?

5. At what temperatures does the fluxing or refrac- tory character of certain additions begin?

6. What are the areas enclosed by some isotliermals'.' In the work of Purdy the specific gravity and porosity

curves agree quite well in indicating vitrification, and hence it is but natural to inquire whether this is the case under all conditions. Any deviations might be reasonably ascribed to conditions pointing towards certain physical or chemical plienomena peculiar to the composition stud- ied, since we know that the density changes with the trans- formation caused by chemical reactions, solution or crys- tallization.

The term flux is but a relative one, and no particular class of substances can be designated as fluxes. In a sili- cious material like clay, basic substances act as fluxes, while in basic compositions like Portland cement silicious compounds unquestionably behave as such. In addition we must consider the fact that a small portion of any sub- stance, no matter what its composition, dissolved in an- other, will lower the fusing point, provided no cliemical reaction takes place.

The rate of these changes is of interest in as much as this factor may have considerable influence upon the prac- tical application. It may be either too rapid or too slug- gish. In this manner we can establish the point at which no further change is observed and when additional amounts show no effect.

The question of temperature establishes the points at which the activity of the various additions become manifest and at what temperature the maximum effect is shown.

The areas enclosed by successive isothermal curves are designed to show the rate at Avhich vitrification progresses,

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS.

U

and the coiuiwsitiou of the fusible conibination as well as the chaiiiie in the composition on raising the temperature. It might be said that thus the changes in the eutectic com- binations are indicated.

The clays upon which the effect of various substances was studied were as follows :

1. Floi-ida kaolin, and in several instances, Georgia kaolin.

I'all clay, Tennessee Xo. 3. Shale from (lalesburg, 111. Shale from ( 'rawfordsville, Ind, Shale from Canton, Ohio. The materials added to the above claj'S were as fol- lows :

8. 4.

1 . Feldspar

2. Whiting

3. Ferric oxide

4. Flint

5. Florida kaolin

(I. Feldsi)ar-flint

7. Whiting-tlint

8. Ferric oxide-flint

0. Ferric oxide-whiting

10. Cornish stone

The composition of some of the materials are given in the following table:

	i ■								Loss	Mois-
SiOo	AljOa	Fe»03	FeO	TiOi	CaO	MgO	K.,0	Na,0	on ig-	ture
<^<.	■ 1c	%	%	%	%	%	%	9t	nition.	9fc

Galesburg* |

Shale ..■ 163.62

Crawfordsville* Shale '68.50

16.31! 6.22'2.J

16.98I 5.77I--

Canton* Shale

III

.\^l.l\\22.2\\ 7.2(j\

0.96

0.63

0.99

0.56 0.30

I--I4 1. 71

1.63 O.II

2. 6011.50 2.97

3.36

Feldsp;ir 168.22:17.83! . .

Flint igS.Oo! [ |..

I I I I Inin Oxido. ... I I l99-00[ I I I I

Whiiin^- ! 1.62I3.50! | | 152.651 |

*Pur(ly and Moore, Trans. Am. Cer. Soc, Vol. 9

12.13

6.260.38

7-mo-27 8.00 ....

1.90I0.35 ....

I0.50

12 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGE

Tlie compositions are expressed in percentages throughout, since the clianges to be noted are shown in this manner as well as if molecular relations had been em- ployed. In fact, considering the heterogeneous character of the clays used and their physical differences, the consid- eration of chemical formula would have appeared to be almost absurd. This is especially true since we were deal- ing only with the vitrification and not the fusion of bodies, and particularly since the earlier stages of vitrification were of special interest to us.

The materials were weighed out in the dry condition, and usually the two ends of a series were ground dry in the ball mill for two hours. From the two end composi tions the intermediate mixtures v.ere obtained by blending and thorough grinding in a mortar. Each batch was then made up with water to the desired consistency, and after thorough wedging was molded into a brickette of the di- mensions : 12.8x7.8x1.3 cm. in a brass mold provided with a movable bottom. Each brickette was cut up into eight prisms, which were stamped with the series numbers. After thorough drying one brickette from each mixture was taken and placed in a sagger. Each burn, therefore, con- tained one of the eight small brickettes of exerj composi- tion. Tlie saggers were placed and cones put in the kiln, well protected from any direct flame. Th(B kiln used was a down-draft test kiln, fired with coke, and has been de- scribed in the paper on "Fritted Glazes" by R. C. Purdy and H. B. Fox.* The firing temperatures wel'e cones 09, 06, 03, 01, 2, 4, 6; some brickettes which had been left by Prof. Purdy as part of an unfinished investigation were fired to cones 9, 11, and 13. The cooling of the kiln was hastened in no case, though the damper was left open.

The brickettes when cold were freed from adhering particles, weighed, and immersed in distilled water for 48 hours; they were then boiled for one hour and finally placed in a large suction flask connected to a filter pump

*Trans. Am. Cer. See, Vol. IX.

IN THE POROSnV AND IHt SI'KCIFIC GRAVITY OF SOME CLAYS. 18

iiiul left there until uo more air bubbles were given off, which usually took several hours. This method was fouud to be more satisfactory than exhaustion by an air pump, as it seemeil to result in better absorption of water. The brickettes were then suspended in water by attaching with a silk thread to the beam of the balance and thus weighed. Immediately afterwards they were weighed in air, thus giving the wet weight. The specific gravity was calculated by the usual foimula and the ])()rosity by the Purdy for- mula.

Several hundred pycuometer specific gravity determina- tions were also made on the dried and pulverized brickettes by weighing a quantity of the powder in the jjycnometer and tilling the pycnometer a little more than half full of warm water. The pycnometer was then attached to a bent 50 cc. pipette, which contained some water. The other end of the pipette was connected to the filter pump and the air exhausted from the powder. The vacuum was sufficient to cause the water in the pjxnometer to boil at a temperature of about 30°. After no more air bubbles were evolved the pycnometer was filled by raising the pipette and allowing the air-free water to run into the apparatus. In making these determinations special pains were taken to dry the ponder in an air bath at a temperature never less than 120 . Scune of the pycnometers were collapse<l by the air pressure.

Conipai'ing the specific gravities by the two methods the differences are shown to be of the following order of majinitude:

14

THK INFLUENCE OF FLLXES AND NON-FLUXES UPON I HE CHANGE

Spec. gr. pycnoni I2.69

Spec. gr. suspension 12.55

Difference 0.14

Spec. gr. pycnom \2.68

Spec. gr. suspension J2.62

Difference 1 0. 06

Spec. gr. pycnom. . Spec. gr. suspension Difference

Spec. gr. pycnoni. . Spec. gr. suspension Difference

2.6212.73

2. 5112.54 0.11I0.19

2.65I2.65 2.61I2.59 0.0410.06

2.66 2.6512.67 5.56 2.61 2.61 o.io 0.04 0.06

2. 65 J2. 67 2.66 2. 6012. 61 2.60 0.0510.0610.06

Spec. gr. pycnom I2.70 2.65 2.67

Spec. gr. suspension I2.62I2.62I2.61

Difference |o.o8lo.03|o.o6

2.76 2.65

2.562.57 0 . 20 0 . 08

2.64 2.61 0.03

2.64 2.62 0.02

2.70 2.59

O.II

2.70 2.66 0.04

2.64

2.57 0.07

2.64 2.61 0.03

2.67 2.60 0.07

2.71 2.60

O. II

2	.66	2.67
2	58	2.61
0	08	0.06
2	67	2.67
2	63	2.,S9
0	04	0.08
2	64	2.67
2	58	2.50
0	06	0.08

2.70 2.68 0.02

2.78 2.80 0.07

2.67 2.66

O.OI

2.73 2.58 0.15

2.68 2.64 0.04

2 . 72 2 . 59 2.69 2.51 0.03 0.08

The sensibility of weighing in the pycnometer experi- ments was about 0.5 milligram for one balance and 1 milli- gram for another, the average sample of powdered material averaging 8 grams. The error of weighing thus varies from 0.005 to 0.01 per cent. In the suspension method the weight of the brickettes varied from 15 to 20 grams. The sensibility of the balances was about 2 centigrams, which corresponds for the 15 gram brickette to a variation of 0.13 per cent.

From these results it is clearly seen that the specific gravity determinations by suspension are greatly af- fected by the porous structure of the clay, that is, by the pores into which water cannot penetrate. It was recog- nized that in order to obtain comparable specific gravity curves the true specific gravity would have to be used.. But since these determinations consume much more time, and the main aim of the experiments planned was chiefly a practical one, it was decided to use only the apparent specific gravities and porosities in obtaining the rates of vitrification, since after all it is the rate and not the abso- lute values that interested the writers most at the time. The study of the true specific gravities has been reserved

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CI.AYS. 15

for inixtiires whose toinponents have themselves been de- fined more closely by chemioal and physical methods, and which are intended to be simple mixtnres rather than such complex ones as are afforded by the shales. By this method it was i)ossible to cover the j>round more rapidly, and about 4000 detei-minations were made. Owin^' to this large mass of data it is impossible to reprmlnce all of the rate curves thus obtained, and hence only the ty])ical cases are presented.

AVe shall now discuss the additions of tlic various re- agents to the clays mentioneil above.

FELDSrAK.

Feldspars are considered neutral body tiuxes. By this is meant that their fluxino- effect is additive, they being simi)ly solvents of the clay substance and the free silica. Feldspar naturally lowers the melting point of a body most when it is added to the euteetic condMnation of kaolin and quartz, which corres])onds to the ratio of 1:3. This is shown xovy clearly in the clever work of Dr. M. Simonis* on ''Tme Fusion Points of Mixtures of Zettlitz Kaolin, Quartz and Feldspar Fxpresscd in Cones."

By means of a simple arithmetical express^ion, for w lii( h ho claims no theoretical or scientific significance, though he suggests its practical use, he calculates the re- fractory (piotient for bodies high in clay and high in, quartz. In the first case, that is, in clayey bodies in which the pel' cent of kaolin is greater than one-third of the per

cent of (juartz, or where K > ^^^ Simonis obtains his re-

fi'actoi-y (|Uoti('nt by the formula

K. F.=K— ''3' -f+00,

where K=% kaolin qwr^fo quartz f-=9^ feldspar.

*Sprechsaal, Vol. 40, Nos. 29 and 30.

16

THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGE

For silicious bodies in which

K <

qu

the formula employe is :

^- K

R. F.= A f -L 60.

2

The number GO is added to prevent negative values. The values of the refractory quotient are translated into cone temperatures by the following table :

Refractory quotient . . Melting point in cones Refractory quotient . . Melting point in cones

17-5	22.6	28.0	Z3-7	39.2	44.6	50.0
14.0	15-0	16.0	17.0	18.0	19.0	20.0
65.0	72.0	80.0	89.0	102.0	114. 0	127.0
27.0	28.0	29.0	30.0	31.0	32.0	33-0

57-6

26.0

141 .0

34 P

From the consideration of the Simonis calculation it is evident that feldspar plays the role of a neutral flux.

With regard to the fusion process of triclinic feldspars we have accurate data referring to artificial spars,* which had the following composition :

We have here evidently mixtures of albite and anor- thite, and on fusing a series of these mixtures it was found that they proved to be a series of solid solutions whose

*Day and Allen. The Isomorphism and Thermal Properties of the Feldspars, Carnegie Inst., 1905.

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS.

17

AJLIAViJO D(dl03d9

IS THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGES

melting points clianged in almost linear relation to the percentage composition of the two silicates. From this result Day and Allen conclude tliat the triclinic feldspjfrs "form together an isomorphous series." This relation is brought out clearly by the curve of Fig. 1, in which the rate of change in the specific gravity of mixtures between the anorthite and albite is shown to be a linear relation. This tends to show that we are dealing here with isomor- phous mixtures and at the same time explains why they have no definite melting points. Albite was proven to melt through a range of about 150^. Although the melting- point of the average feldspar as used in the industries is about at cone 8, yet its interaction with clay substance begins at a much lower temperature. Berdel found that the dissolving action of orthoclase feldspar began as low as cone 09.

On fusing mixtures of the trilinic feldspars it Avas found that their melting points were connected by a straight line, the same linear relation that held for the specific gravities. This shows likewise that the fusion of the triclinic feldspars is a continuous smoothly i>roceeding process, and it is even possible to calculate the composition of each point on the curve from the specific gravity or the fusion temperature.

ADDITION OF FP]LDSPAR.

The behavior of orthoclase feldspar is shown suffi- ciently in the porosity and specific gravity curves of Figs. 2, 3 and 4. We observe that the vitrification due to feld- spar is indicated both by the drop in the specific gravity and the decrease in porosity. We also find confirmed that the solution effect of feldsfjar begins at quite a low tem- perature, at least as low as cone 06. It is likewise shown quite distinctly that feldspar is a neutral flux and does not undergo any chemical reactions. The only nunimum is that due to the eutectic mixture which, however, was not fixed in these series. The solution of kaolin by feldspar

IN THE POROSITY AND THE SPKCIKIC GRAVITY OF SOME CLAYS.

i

1

K

rt-

«S

'

ffi

z > ■<»- <o o

O Qi Z

n S "= ^ = =

r •< in .0,0 0° u. ° 75 ^^0

— 1

^

\

?

^.

/

\

X

i

/

J

>

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«J 5 '^ d = -~ = » ^ a: 1 .0 5^ 0? ^ < Z SSSi

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Aiisoaod o/a

20 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGES TRANS. AM. CER. 50C. VOL. X iLEININGER AND MOORE

i*,—

FIG 4.

I3t

^

\.

si^.

GEORGIA KAOLIN

"^

f^

c \

PELDSPAR

45

40

^0

(A

o

K Z5 o

"■EO

'0

5

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R

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1 1 1 1 1 1

X

^

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a

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v^

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c^

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\

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N

,

o

\

^

a.

100 90

0 10

40

30 4-0 SO 60

COM POSITION

30 KAOLIN 70 SPAR

TRANS. AM CER 50C VOL. X

8L£ININ0ER AND MOORE

&0

50

4-0

FIGS.

TENNESSEE BALL CLAY N0.3

2c FELDSPAR

\

V

0^

V

<;.

- C

^5

^

V

^

^\

. .

^

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on

; 7L

10 20 30 40 50 eO 70 80 90 100 SPAR

90 80 70 60 50 40 30 20 lO 0 BALL CLAT

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS.

21

			^
		/	'		\
v9 • u.			V			\
					1
CANTON 5HALE-5PAR POROSITY. 1					/		/
	\

						\	\
							1
	ol		)
			er^	/		v/
	c	0/ Jj	O
			r Q		(
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		o

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in

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in o

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(L

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w:

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AUSO^Od %

22 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGES

TRANS. AM. CER. SOC VOL.X BLEl NINGER /\N0 MOORE

50

FIG. 7.

CANTON SHALE-SPAR POROSITY

NO.I 100% SHALE

Z 99% " l%SPAR

3 9G% » A°'o y>

4 94% " G% y S 9 2 % » ft %> "

4-5

40

35

5^

^

'^^w

6 90% « 10% n

30

^

X

^

• 25

N;

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^

\

^

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1,2. 4-

5

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---

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09

06 03

CONES

01

IN THE POROSITY AND THE SPICCIKIC GRAVITY OF SOME CLAYS.

23

takes place at a fairly rapid rate, which shows simply that there seems to be no physical obstacle to this mutual solution.

The curves also bring out the ditterence in the behavior of Georgia kaolin and Florida kaolin.

In Fig. 5 we have the porosity curve of mixtures of Tennessee ball clay No. 3 with feldspar, and it is evident that feldspar in this case becomes far more potent in its action than in the cases of the two kaolins.

The effect of various percentages of feldspar upon Canton shale is shown in Fig. 6, and we observe that though the first additions cause a small decrease in poros- ity, the result shows practically no gain in fusibility or ^itrifi cation. The same fact is brought in Fig. 7, in which some of the shale-spar curves are arranged.

In this connection it was also interesting to observe the action of Cornish stone on kaolin as shown bv Fig. 8.

TKANS AM CER &0C. VOL. X.

BLEININGER ANQ MOORE

AO

FIG. 8 FLORIDA KAJliN

8£

^=;

-^

"^

^

^^

^

N

\

^d

[^

\

X

\

N?

-^

\

sr

N

X

Sf

^

Co

k".

^

\^

\

r

^^

>

K

s

^

\

^

X

^

\

CORNWAU STONE 10	20 30 m	50	60	70	80
KAOLIN 90	SO 70 60 C 0 M PC 5ITI0N	50	.40	30	20

24 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANCES

Here we uote distinctly the slow, ueutral fluxinj^ effecL of this material whose action is more gradual than that of tlie feldspar and which offers the safest flux, as far as range and rate of vitrification are concerned.

THE ADDITION OF LIME.

Kaolin and Ball Clay. In the addition of calcium carbonate to clays we are dealing with a flux which is unlike feldspar or Cornish stone. Its action is not gradual, but variable; that is, though its presence may not be observed by means of the porosity curve, at the proper reaction temperature it suddenly combines and causes as large an amount of fusible magma to be formed as is con- sistent with the composition of the body. At the same time there is to be considered the fact that lime-alumina-silica compounds form a number of maximum and minimum fus- ing compounds. This has been clearly shown in the work

TRANS. AM. CER, SOC. VOL. X

BLEININGER AND MOORE .

37,

35

33

31

23

ZV

20

"J 18 Z

olfe U 14

I/)

FI0.3.

1

_

p

--

^

r

\ X • «

K >

^

u

\ /

X

N ____^

^

\ i

/

\

s /

i

S.

\ ^

\a

f

V

1.5 Z.0 Z.5 3,0 i5 M 4:5 SO 5.5 fiJ) 6.5 ZO 75 8J) 8.5 9.0 9.5 10.5 10.5 II.O 11.5 \ZJI MOLECULES CaO TO 1 MOLECULE Alg^O^ • ZSiOg^

IN THK POROSITV AND THE SPKCIFIC GRAVITY OF SOME CLAYS.

2o

of Rieke,* who investigated the melting points of mixtures of this kind in a most thorough and exliaustive piece of work, using an electric carbon lesistance furnace for the determination of the melting points. We shall consider only his results, referring to the AUOg : 2 Si02 mixtures and those higher in silica. The first curve brings out the fact already noted by (Jramerf that for high temperatures, additions of CaO to kaolin, up to 10%, decrease the melt- ing point in equal intervals. The lime-kaolin fusion curve of Kieke is reproduced in Fig. 0, the abscissa indicating the molecules of CaO to 1 molecule of AloO^ : 2 SiOo, the ordinates the melting points in cones. With a content of 10% CaO we have a minimum corresponding to the for- mula CaO, .2 AI2O3, .4 SiO.. On increasing the lime we find a maximum at the com])osition CaO:Al.jO;::2 SiOo. With more lime the fusion curve descends again to a mini-

TRANS

AM CER. SOC VOL X

BLEININGER

ANO MOORE

FIG. 10

'

\

^

30

1

^

Y^

^

y\

r'

-^

^

f

IS

/

(OIV UJ

2 15 0 0 IJ

1

1 /

W^

\

\ /

9

\

K

\ 1

/

Vn

i-n

05 li) 1.5 I Ih iJ) i.5 +0 4.5 SH 5.5 M 6.5 70 Z5 8.0 B.5 9.0 3.5 IttO 105 IID ir.5 IJ.O MOLECULES OF CcxO TO 1 MOLECULE AljOiOSnOi

*SprccIisaal, Vol. 40, Xos. 44, 45, 46. tTonindustrie-Zeitung, 1887, p. 197, ami 1888, p. •]2,.

26

THE INFLUENCE OF FLUXES AND NON-FLUXES UFON THE CHANGES

mum 2 CaO : AI2O3 2 SiOo, which is tlie most fusible com- bination between kaolin and lime that exists correspond- ing to a percentage composition of 36.1% SiOg, 30.5% AI2O3 and 33.4% CaO. On increasing the lime still more Rieke obtained a second maximum at 4 CaO : AUOo : 2 SiO.

This is followed by a third minimum 6 CaO : AI2O3 : 2 SiOj. After this it appears that no further decrease in melting point occurs. Since the maximum and minimum points very likely correspond to chemical coml)inations, it seems, according to Rieke, that there exist at least four distinct compounds of lime and kaolin. f

In the mixtures of CaO with AloOo : 3 SiOo shown in Fig. 10, there are observed four maxima and four minima which appear to show the existence of the following com- pounds and mixtures:

TRANS.

AM. CEK. S.OC

VOL.X

BLEifJINGER

AND

M03RE

FI6.ll

34

32

30

28

26

19

17

iul5 z

°I3 0 II

I

\

1 ■ ^

r !

\ /^

!

\ \ ^\

k

/ 1

i

\

y

1

9 7

i

\

y

1

^- ^

f

\,

^-x^

<

5

J

-J

\^

r^^v— -r"^

'\

0.5 1.0 1.5 U 1.5 3.0 3.5 4.0 +.5 5.0 55 fc.O 6.5 7.0 7.5 8.0 g.5 90 S.5 MOLECULES CaO TO MOLECULE 5">lO.O 5; baseline 0.001433 8" id="line_000032_000069"> 5">1 5">AlzO^-^SiO^

tRieke's view that the minimum as well as the maximum points cor- respond to chemical compounds is open to criticism. The minimum points ;irc probably eutectic mixtures.

IN THE POROSITY AND THE SPKCIFIC GRAVITY OF SOME CLAYS.

27

CaO

7 CaO

3 CaO

5 CaO

13 CaO

2 Al,03

4 AI0O3

Al.O,

AloO.,

2 A1.,0..

6 SiOo

12 SiOo

3 SiOs

3 SiOo

CaO Al.,03 3 SiO,

2 CaO AI0O3 3 SiO,

4 CaO ALO3 3 SiO,

6 CaO A1.,0.. 3 SiO.

6 SiO..

Finally iu mixtures of lime with AI2O3 and Si02 Rieke found one rather indistinct maximum, 5 CaO : 2 AJ^OaiS SiOs and two minima, Fig. 11. The curve as a whole is more regular than the preceding ones.

It is evident from these data that we cannot expect from lime-clay mixture the regularity of fusion induced by feldspathic fluxes, and it remains to be seen how the vitri- fication of different clays is affected by this flux.

Lime — Florida Kaolin Mixtures. Inspection of curve of Fig. 12 shows clearly that with increasing lime content at Cone 06 but little change occurs within the compositions examined, the mixture containing 10% whiting showing

TRANS. AM CER 50C. VOL.X.

BLEININGER AND MOORE

50

40

v30

h;

o

o Q.

FLO

RID/

FIC

POP

OLIN-W lOSITY

1

HIT

INQ

.

■ —

-^ '

'

~

Co

ne

06

~~~"

^ .

-^

CO

1-1 e

^

-V"

__^

—

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c

-o>

le"^

■^

\

S,

/

V

\

/

WHITING I BALL CLAY 'i^

3 97

4 5

96 95

COM POSITION

10 90

28 THI£ INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGES

ouly 4% less porosity than the composition 99. 57^ kaolin, 0.5 7 whiting. We also observe that the first 2% of whit- ing in tlie Cone 9 curve are more eifective in decreasing porositA' tlian 3-6%, a second decrease in porosity taking place only bej'ond C/o whiting. Of course this is in agree- ment with the general theory of dilute solutions as sug- gested by Ludwig.

On studying mixtures of ball clay and larger amounts of lime we observe in the specific gravity curve, Fig. 13, a distinct minimum in the Cone 09, 03, and 2 burns at about 30% whiting and 70% ball clay, which corresponds roughly to the minimum CaO : AI2O3 : 2 SiOg observed by Rieke. This seems to be the eutectic composition under these tem- perature conditions. The corresponding porosity curve, Fig. 14, shows two maxima and minima, the first maximum being at 30 7o whiting and 70% ball clay, the second at 50% clay, 50% whiting. The minimum is at 40% whiting, 60% ball clay, a second minimum is indicated, but not

iiO

TRAN6

AM

CER. SOC.

V'OLK

BLEININGER AND MOORE

FIG 13. :SSEE BALL CLAY N23

/

^

TENNE

Qot CO3

I

Y

J,

^

/

J

/

1/

/

i

,i...O

0

4

:2.30

0/

/

^

CaCOj 10	20	30 40	50	60	70	80	id	100
ML CLAY 90	80	70 60 COM POSITION	SO	40	30	20	10	0

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS.

29

reached. Of t-ourse it would be idle to claiiu that these maximum points actuallv do represent certain compounds, as we must remember that the apparent specific gravities are the resultants of a number of factors, of which not the least important is the temperature to which each brickette was raised in the kiln. It would be claiming too much to say that each brickette actually reached or did not exceed the temperature of the burn as indicated by the cone in each sagger. There must have been temperature differ- ences. ^Vnother verj' important factor in the curves repre- senting a series of compounds, is the constantly changing initial specific gravity of each mixture as we start from one side of the curve sheet to the other. For instance, the last series, on going from left to right increases in lime. Every increase in CaO thus means a change in specific gravity, and this should be borne in mind in examining subsequent curves. If, now, in spite of these factors, certain maxim i and minima occur, coinciding, at least in most cases, with

70

TRANb.

AM

CER

soc

VOL X.

8LEININGER AND MOORE

/

-V

FIG 14. TENNESSEE BALL CLAYf Ca CO 3

4s

s.

S3

/

11

\

^

2.

'iii

'

\V

\

01

40

f

til 1^1

1

\^

03

/

"V

<

!h

\

>

/

1

\

06

J

y

-N,

M

06

o

DC

a.

i 1,03

^

N

vl\

^

\

(jj

n5> 10

10 20 30 -VO 50 60 Ca CO,

90 90 70 60 50 40 BALL tlAY

C 0 M P 0 SITIO N

30 THE INFLUENCE OF FLIWES AND NON-FLUXES UPON THE CHANGES

similar points in the porosity curves, we are led to the conclusion that certain phenomena are taking place. The technical side of the vitrification progress is represented, of course, by the porosity curves. In Fig. 15 the action of 6 and 9.5% respectively of whiting is shown for the lower temperatures, and we observe tliat the decrease in porosity begins about between cones Ofi and 01.

TRANS. AM CER 50C. 70L X

BLEININGER AND MOORE

(LIO

FIG 15.

FLORIDA KAOLIN-WHITING POROSITYANO SPECIFIC GRAVITY.

1= 90.5%KA0LIN-9.57oWHITING Z * fl+.0% >> - 6.0%)

3.1

2.7

<

a: o

2.3

1.9 1.7

03 06 03 Oi 2 +

CONES

Shales. In the porosity curves of mixtures of Hanton shale, Fig. 16, and whiting we observe that the lime begins to act as a refractory substance in percentages that vary with the temperature. In the Cone 06 curve almost the first addition of lime seems to increase the porosity, while

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAY'S.

31

Hie iiicreasi' in the ('one 01 and 2 eiirves be<>ins vitli 1.5 and 4.5% respectively. The significance of the minimum with the 0% addition, if it really is a minininm, remains lo be explained. From general considerations it api)ears that the porosity at about that point ought to decrease.

The rate at which this shale decreases in specific gravity and porosity is shown in Fig. IT, and brings out the fact that the porosity tends to increase up to Cone 06, and from this point on shows a rate of decrease slower than that of the pure shale. But after passing Cone 03 its vitrification becomes decidedly more rapid than that of unmixed shale, as we know to be the effect of lime.

In Fig. 18, representing mixtures of Crawfordsville shale and whiting, we observe a very decided increase in porosity between Cones Ofi and 03, followed by an ex- tremely sudden drop between 03 and 01. The increase in porosity after vitrification has been reached is also quite marked in .some of the lower lime mixtures.

TRANi. AM CER SOC VOL X

BLEININGER AND MOORE,

50 45 40 35

:^Z5

a.

FIG 16.

CANTON SHALE ANOWHITING

1

f

g-*>

e 0

b

^

N

^

— ■

==*

—

-^

C

gtx<

p^

^

V

y

^

r <

.^^

J^

\

S,

/

-^

^

y

^

^^

/

^

X

— '

s

"—

i

— ^

.^

SHAlflOO

WHITING

97	96 95	94	93	9Z	SI	90
3	4 5 PER CENT	fo	7	8	9	10

32 THE INFLUENCE OF FLL'XES AND NON-FLUXES UPON THE CHANGES

Of

00 U.

? «^ ^

<

>0

s - - «

Qi

o u.

i

o5 o en "Ji

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— <vj fO +

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f

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Aiisoa od 9&

1

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b = =

1 ^ S ^^-

t3 :^ -.■ c

LU

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01 tn CD «

— ivj /T) <; O O O c

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(

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KXISOyOd %

IN THE rOROSlTY AND THE SPECIFIC GRAVITY OF SOME CLAYS.

33

The Galesbiirg shale, Fig. 19, was less affected by the lime added than the two other shales at Oone 2, but at Cone 4 the mixtures had gone considerably beyond viscous vitrification and had stuck to the saggers.

TRANS. AM.

:er

soc

VOL.X

BLEININ&E.R AN0MOOf?£

FIQ.19. GALESBURG SHALE-WHITING POROSITY

40

NO Z 95.5% " 4-. 5 * WHITING

N0 +

3

s

2 "a

> ' fo.S ~/c

„

J-

-^

^

,vs

^^

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vl5

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1

5

09

06

CONES

03

With regard to the effect of lime introduced as the carbonate we may say, therefore, that it is not a neutral, gradual flux, but evidently there are produced several com- binations of lime with the other constituents of the clay which are available, wliich give risee to curves showing maximum and minimum points. This is the case especially with larger amounts of lime. This effect naturally is more

34 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGES

prominent at higher temperatures. The fluxing effect of small amounts of lime on high alumina cIsljb is not marked at lower temperatures, as evidently such temperature as Cone 2 are not jet within the temperature zone of its activity.

50 3

TRANS.

AM

CER

soc

VOL.X

BLEININGEP

AND MOORE

'I

45

_

*^,

^

s^

► 40

s

V

\su\

35

\

^

V

\

c^

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30

^

s,^

^

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I

25

>-

v^

3

\

o 0.

\

2

\

4-

15

FIG. 20.

FLORIDA KAOLIN -Fei03 POROSITY CURVES.

10

-

N0.1 = 92°/bKA0LIN 6% FezO^

N0.2 » 100 % »

NO. 3 . 94^0 '> 6% "

5

^ ■

JU.+

= y

feVo

))

+ 7o

»

03 06

CONES

03

In ferruginous shales containing lime the maximum fluxing effect is shown by not more than 5% of the car- bonate. Any increase above this amount seems to produce refractoriness at temperatures up to Cone 2 inclusive. The amount of lime drawn into reaction increases with the temperature; while at Cone 06 it does not seem to have

J

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS.

35

taken part in the condensation of the body, at Cone 01 its etfect is noticeable. In re<>ard to its «>enei'al behavMor in a pavinji; brick shale we must say, of course, that it is an undesirable constituent, not on\j because of its sudden rtuxino- effect, but also because of its tendency to produce vesicular structure.

TRA

NS.

AM

CER

soc

VOL

X

BLEININGeF

AND MOORE

Fie.2i.

CANTON SHALE

Fea03

NO 1 > 100 "o SHALE

NO 2. ^ 90'c

lO-'bFe2 03

40

N0 3 = 94% "

6% J' 1

NO 4 - ge.s^o "

N0 5 » 99 % '-

3.5 "j " j

2

i-'o " ,

35

4

A

1 1

J

\

K

25

\

^

20

\

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\

^

>-

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tl5

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tfl

\

k

\

^

vv

u:

S,

^\

N

2 10

\.

^c

k

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\,

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\f^

N

>V-,

4

0^

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V

■^

1

5

s

•s^

-■^

-^

N,

s^

'*■

N.

^

2

\,

■

■^

5

09 06

CO NE5

03

ADDITION OF FERUIC OXIDE.

In the series in which we have mixtures of clay with increasinp^ amounts of ferric oxide, it is evident that each increase in iron results in an increase of specific uravity, and hence specific gravity curves are of little value in this connection.

36 THE INFLUENCE OF FLUXES AND -NON-FLUXES UPON THE CHANGES

Florida Kaolin. From Fig. 20 we observe at ouce that iron oxide is by no means an active flux when combined with clay substance, for while a small amount seems to exert some fluxing action, its general tendency seems to be a rather indifferent behavior. The areas inclosd by the 100% kaolin and the kaolin-iron mixture curves give some measure of the fluxing effect of the ferric oxide. It is noted that in part of the curves the ferric oxide behaves as a refractory agent.

In the shale-ferric oxide series practically the same effects are observed. In the Cone 2 curve up to an addition of 2.57c of ferric oxide a small decrease in porosity is ob- served, after which the iron seems to behave as a neutral agent. More iron tends to make the clay more refractory up to a certain point. There is no doubt but that, if the iron were increased still more, one or minimum and maxi- mum paints would be reached, for in the 90% Canton shale — 10% FeoOg curve the fluxing effect becomes quite marked. Fig. 21 shows the effect of the ferric oxide upon this shale by the areas enclosed between the two porosity curves. The other shales behave in much the same manner.

We may conclude from these results that ferric oxide is not an effective flux when combined with clay substance, nor has it a very marked influence upon ferruginous shales. In the first case, perhaps due to the lack of free silica, in the second due to the large amount of iron already present. At the same time the ferric oxide behaves as a slow acting and safe flux. An excess seems to promote the formation of a vesicular structure, and it might be that in the shale- iron oxide curves with varying percentages the increase in porosity is due to this cause.

The hypothetical case of adding iron oxide to clays in order to make them more suitable for the manufacture of paving brick seems, therefore, not to be well taken, though some patent specifications prescribe such a mixture.

IN THE PORCSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS. lil

TRANS. AM CER SOC VOU.X. BLElNINQER AND MOORE

50

4()

t-iO

Ol

K/

lOLI

FIG. 22. N Sc FLINT

1

CO

ie

9

kV

' ^

c.c'';^^^^^''^

.^.— -

1

^

^^

Vi^

^

FLINT 10 20 30 40 50 60 79 80

KAOLIN 90 80 70 60 50 40 30 20

C 0 MPOSITION

TRAN6. AM CER 50C VOLX.

BLEININGER AND MOORE

FLINT Z.	4 6 8	10	12	14	16	18	20
CAMTON SHALE 98	96 94 92 CO MPOSITION	90	88	86	8^	82.	80

38 THE INFLUENCE OF FLUXES AND NON-FLUXES UION THE CHANGES

ADDITION OF FLINT.

Florida Kaolin. As is to be expected, the kaolin-flint series produce curves showing increase in porosity with increase in flint, Fig. 22.

Shales. Mixtures of Canton shale and flint, Fig. 23, showed a remarkable drop in their porosity curve at the

TRANS.

AM

ZBR.

soc

VOL.X

BLEININGER AND MOORE

FIG. 24-

^

CANTON SHALE-FLINT

45 t

^

N

s

POROSI

1

TY.

^

40

^

35 4 3 1

30

N

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s

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NO r 100% SHALE

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NO 3 89% " 11% "

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composition, 90% shale, 11% flint. Up to this proportion the porosity of the shale mixtures for each temperature kept about constant. This drop is simultaneous in all of the temperature curves, and clearly indicates that a far reaching change took place at this point. The practical conclusion, hence, would be that 10% of fine flint acts as

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS.

39

ii flux ill this shale, formiug probably an easil}^ fusible silicate with the iron oxide and other fluxes. In mixtures of Galesburo- shale and flint two drops were observed in the porosity curve, though neither one of tliem was well defined, one at 89^r, the other at IS^^ flint. In the Craw-

TRANS AM CER SOC

/OL X

BUININ&ER A-iO MCJRE

40

FIG.iS.

NO 1 ' 96%GALESBURG5HALE 4fcFLINT

NO 2 ' 100 % >• 0 % » NO 3- 93% " 7% » NO 4 • 9Z.'"^o » 6% » NO 5 = 90% •> 10% »

35

NO fc • Zb% » l+% »

1

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CONES

fordsville shale mixtures the Cone 2 curve likewise showed two minimum points, one at 10%, the other at 19% flint. These points also were not as well defined as the point observed in the Canton shale, though more distinct than in the Galesburo; shale.

Referring to the absolute fluxing effect, there is no gain as regards increase in fusibility by the addition of

40 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGES

TRANS. AM CER. 50C. VOL \ BLEININCaER AND MOORE

40

35

30

Z5

20

tl5 (/) o a:

CR/i

^WF(

)RDS

Fia.26.

VILLE SHALE -FLINT OKOSITY

!

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\

^

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---

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09 06

CONES

03

01

IN THE POROSITY AND THE SPF.CIFIC GRAVITY OF SOME CLAYS.

41

tlint to Cauton shale. Auy addition of tiint at oiue makes the (lav more refractory until 11^/^ have been added, when the drop occurs. At the last point the mixture seems to be but a trilie more refractory than the unmixed shale, Fig. 24. The rate of vitrification does not seem to be affected; if at all, it is in the direction of safer buruinii,.

The Galesburg- shale mixtures with flint show a de- cidedly lower vitrification range than the pure shales, and it seems, hence, that in this case flint acts as a pronounced flux. Fig. 25.

In the Crawfordsville shale the flint acts distinctly as a flux up to 5%, and at the same time it disturbs the rate of vitrification unfavorably. Fig. 2G. Above 5% the refrac- tory character of flint appears, which is maintained until 10% have been added. In this case also the rate of vitrifi- cation is changed in an undesirable manner.

TRANS AM CER SOC VOlX

BLElNlNGER AND MOORE

100 96 38 97 96 9S 94 93 91 91 90 89 01 2345 6736 10 II C OMPOSITION

87 86 SHALE

13 1+ rt <A0L1N

42

THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGES

ADDITION OF FLORIDA KAOLIN.

Shales. The first addition of 1% of kaoliu to Cauton shale in the Cone 2 curve produced an increase in porosity which then kept practically constant until 6% had been added. At this point anotJier slight rise in [)orosity took place. Between 10 and 11% a sudden drop in porosity was observed, and it is evident that the kaolin in this proportion exerts a decided fluxing- action, Fig. 27.

In the Crawfordsville shale a rise in porosity at 2% and a drop at 3% is observed. With 15% of kaolin a very decided decrease in porosity is noted corresponding to the drop with 11% Canton shale, Fig. 28.

In the Galesburg shale we observe (Cone 2 curve) a drop in the porosity for the addition of 1% kaolin, followed by a rise, after which the curve has a slight upward slope. At the highest percentage of kaolin added, 15%, the mini- mum point, if tliere is one, has not been reached, though the curve suggests its presence. Fig. 29.

TRAN5

AM

CER

soc

VOL \

BLEININGE-K AND MOORE

60

CRAWFORDSVILLE SHALE-KAOLIN

50

40

/

^

y

\

^^^

— — .

^

Coi

i.e(

6^

^

->^

30

^

■%,

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I

KAOLIM Z.	+ 6	8	10	12.	14	15
SHALE 96	96 94- C 0 M POSITION	ga	go	88	ee	8i>

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS.

43

AXlS0>dOd%

44 THE INFLUENCE OF FLUXES AND NON -FLUXES UPON THE CHANGES

From the specific gravity and porosity curves of the single Crawfordsville shale and kaolin mixtures, Figs. 30 and 31, we observe several interesting phenomena. The 1% mixture curve is practically parallel to the pure shale curve. With the 3% mixture the kaolin acts as a flux

TRANS.

AM CER SOC VOLX

31EININGERAN0 MOORE

FIG. 30.

CRAWFORDSVltE 5H SPECIFIC GRAVITY

ALE- CU

(AOUN

^VES.

Z.9

2.7

^

^^

:^=r-

*^

J

2.5

\

=^

n

r

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.. 5 . 95 ■• " 5 • '+- 92 - " 8 ■■

1.7

• 5' t

8 -

» la •

03 06

CONES

between Cones 09, 06, and 03-2. At Cone 01 we find a distinct minimum point, which is shown also in the 5% mixture.

The Canton shale-kaolin mixtures likewise show a minimum point at Cone 01, and the curves indicate that up to about 10% the clay substance does not exert any

I

IN THE POROSITY AND THE SPECIFIC GR.'VVITV OF SOME CLAYS.

45

tf

■«-

S: a? 6? 0^ ^ 55 . ' — m m oQ — M U to 3J uj

0 5 ^ . . . . .

I *? •^^ ?^ f - "^

P 0 W ^ C^ — ^ p- 0 OO ^ Ol CD CD

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FIG 31

CRAWFGRDSVtLLE SHALE -KAOLIN POROSITY.

Z

£

0

z

< ; - » »

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Aiisoyod %

46 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGES

iufluence upon the clay below Cone 03. The 11 % mixture, however, shows a great drop in porosity, and here the kaolin behaves as a potent flux. Fig. 32. The fluxing power of kaolin in the Galesburg shale is shown by the 1% curve, and we note also in the curves up to 8% that this action

TRANS. AM CER SOC VOL.X.

BLEININGER m M03RE

olO

FIG. 33.

GALESBURG SHALE-KAOLIN POROSITY

N0.1 - 100% SHALE

I' 99% " l^oKAOUN 3 ' 96 % ') 4% >> 4- « 94% " 6% a

5 • 91 % » 9 % »

!^

j.

\

N,

t

^v

\

k

w

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09 06

CONES

03

takes place at a low temperature, between Cones 09 and 03, the rate of decrease in porosity being quite steep.

It is shown clearly, hence, that different shales react quite differently towards kaolin, and it is not at all im- probable that this might afford a means of differentiation betAveen the structures of various shales.

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS. 47

ADDITION OF FELDSPAR-FLINT.

Kaolin. Mixtures of these three materials offer special interest to the clay worker iiiasiiuich as they make up tlie bulk of our porcelain bodies. But the study of sudi a system becomes more complex, and hence the writers have resorted to the use of the triaxial diagram, t\hich is a well known means of expressing three variable compositions

Tf^ANS. AM CER. 50C

VOL.X-BlEininGER and MOORE.

= 16.54-.

with the constant condition that the sum of the three com- ponents be equal to 100. The use of the triaxial diagram has been explained in our Transactions by ^Mr. H. E. Ashley (Vol. 7). To recapitulate briefly, let us call the lower left hand corner of the triangle, Fig. 34, the origin or 0 per cent of flint, then along the base of the triangle we measure the flint so that the right hand corner stands for lOO^f of flint. Continuing in tlie counter-clockwise direction we proceed to measure the feldspar along the right side of the triangle. This, of course, makes the 100%

48 THE INFLUEN'CE OF FLUXES AND NON-FLUXES ;;PON THE CHANGES

tliiit {'ornei' equal to 0^6 feldspar, and the apex of the triangle then becomes 100% feldspar and at the same time 0% kaolin. The latter thus is measured along* the left side of the triangle and the lower left hand corner becomes equal to 100% kaolin. We might thus represent to our- selves the diagram nmde up of three triangles, of which the apices are respectively 100% flint, 100% feldspar, and 100% kaolin. The base of each triangle then would equal 0% of flint, feldspar and kaolin respectively. If hence we desire to plot flint we would measure along any line par- allel to the base of the flint triangle, that is, parallel to the kaolin line. Similarly, we measure feldspar along any line parallel to the base of the feldspar triangle, that is, parallel to the flint line. The kaolin then would be meas- ured along lines parallel to the feldspar line. Thus, a mix- ture consisting of 25-/( flint, 25% feldspar, and 50% kaolin would be measured as follows (Fig. 34). At the point 25% flint we follow a line drawn parallel to the kaolin line. We then proceed to the feldspar side and draw a line from the 25% point parallel to the flint side. The intersection of these tAvo lines will be the point sought, for on draAving, from the intersection point, a line parallel to the feldspar side, it will strike the kaolin side at the 50% point. The point, hence, represents 25% flint, 25^^. feld- sj)ar, and 50% kaolin. Similarly anj' other mixture may be plotted.

In the diagram we can now group together these mix- tures, vitrifying at the same temperature by drawing lines connecting all mixtures whose vitriflcation point, that is, the point at which they absorb, not more than I'yc of water is the same. For instance, by drawing a line around the area including all mixtures vitrifying at Cone 4 we have defined a thermal boundary, and the resulting curve we call the isothermal. By doing the same thing for the Cones 6 and 9 we obtain successive areas which increase in extent. This method, therefore, represents not only the comijositions which may be expected to vitrify at a certain temperature from which the one most suitable for prac-

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS. 49

TRANS. AM.

VQL.X- BLEININGER AND MOORE

PIG. 35.

FLA. KAOLIN

tical operation may be selected, but it also shows distinctly the intervals between the isothernials, thns expressing the range of the vitrification areas. Fii>-. 35 thus gives us a suniniary of the vitrification behavior of the system Flor- ida kaolin-flint-feldspar, which needs no further explana- tion.

In Figs. 30, 37, 38, 39, 40, 41 we have mixtures of 30%, 40%, 50%, G0%, 70%, and 80%.- of Florida kaolin. In all the series excepting one, the 40% series, the porosity curves are fairly smooth. In this series two distinct maximum points are observed; one with lO'/c flint and 50%) spar, the other with 50% flint and 10% spar. The cause of these two changes the writers do not venture to explain. In regard to the individual porosity' curves of the kaolin-feldspar-flint series the rate of decrease in porosity becomes very sudden under two conditions, viz., in the kaolin-feldspar mixtures in the absence of flint, and in the mixtures containing but a small amount of flint compared with the amount of feld- spar. This is more pronounced in the low kaolin series.

50 THE INFLUENCE OF FLUXES AND NON-FLUXES UFON THE CHANGES

TRANS AM CER. SOC VOL X

BUEININ&ER AND MOORE

AC

30

=20

F

KA LIN

FIG.3

OLIN = T + 5P>

5. 30

Z = 7C

%

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FLINT 10	20	30	40	50	60	70
SPAR 60	50	+0	30	Zt>	10	0

TPvANS AM CER SQC VOL X

BLEININGER AND MOORE

40

30

>-

LlO

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=LIJ

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FLINT 10 20 30

SPAR 50 40 30

C OMPOSITION

IN THE POROSITY AND THE SPKCIKIC GRAVITY OK SOME CLAYS. 51

TRANS

AM CER SOC

VOLX

BLEININQER

AND

MOORE

-.

KA LIN

FIC

OLir

IT +

.38 SPA

50% ^R -

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C OMPOSITION

24	32	40	48	50
26	18	10	2	0

TRANS AM CER SOC VOL X

BLEININOER ANO MOORE

FIG 39.

KAOLIN - 60% FLINT&SPAR-407o

FLINT SPAK

6

12

18

24-

30

J4

28

COMPOSITION

22

16

10

36

4

40 0

52 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGES

TRANS AM CER SOC. VOL X BLEININGER AND MOORE

FIG 4-0.

KAOLIN =70% FLINT& SPAR 30%

FLINT 4 8 12 16 20 2+ 26

SPAR 26 22 18 14 10 6 ^

COM POSITION

TRANS AM CER. SOC

VOLX

BLEININGER

AND

MOORE

FI&41

i

8(

)7o KAOLIN -20%SPAR + FLINT

■ 1 , 11

50'

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IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS. 53

K

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04 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANCES

TRANS. AM CER S0(

.. VOLX.

BLEININGER AND MOORE

40

z

•

FIG44.

KAOLIN 50% FLINT+SPAR50% POROSITY.

4 inn o/. 1/ A ni iM

2 = 4-0 "^o FLINT -t-IO^/o SPAR

3 • 3a ' -18

\ 35

6

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03 Ot

IN THE POROSITY AND THE SPKCIFIC GRAVITY OF SOME CLAYS. -Ji)

As the fliut iucreases the curves assume a gentle slope. Au illustratiou of this behavior is shown by Figs. 42, 43, 44. It is also an interesting fact that feldspar behaves as a powerful Hux at such low temperatures as Cones OG ami 03. The writers find it impossible to discuss the many curves available from these series without greatly exceeding the limits of this paper. One more fact might be mentioned, however, and this is the tendency of high feldspar mixtures to become vesicular, even before total vitrihcation is reached, thus obscuring the real changes taking place in the molecular body structure.

^halc. The effect of a feldspar-flint mixture may be observed in Fig. 45, where we have 76% Canton shale and 24% of feldspar and flint. It is seen that even a mixture of 7% of spar and 17% of flint exerts a fluxing action upon the shale.

Similar effects are observed on the (lalesburg and Crawfordsville shales. Fig. 46 shows the vitrification of some Canton shale-spar-flint mixtures in which the flux- ing effect of these components at Cone 2 becomes quite evident.

ADDITION OF LIME SILICA.

Shales. The effect of lime-silica upon the Galesburg and Crawfordsville shales is shown in Figs. 47 and 48. A mixture of 5% whiting and 15% flint has evidently lowered the vitrification point of the Galesburg shale to Cone 2 and that of the Crawfordsville shale to 01. In each case this is accomplished at the sacrifice of the safe to a rapid rate of vitrification. The presence of the silica seen)s to have a slight modifying effect since the curves are not so abrupt as they would be if the lime were added alone.

In Figs. 49, 50 and 50a we find assembled some of the vitrification curves of these shales blended with varying amounts of flint and whiting.

56 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGES

sC CO

1

Xl*ISO^Od'

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS. ")7

TRANS AM. GER SOC VOL X.

BLEJNINGER AND MOORE

40

35

30

25

ZO

H|5

10

0^

FIG 4-6

CANTON SHALE-SPAR-FLINT POROSITY.

NO l')00 7o SHALE

2 76% » 2^%SPAR 2.%FLINT

3 » ^^16 ''6 »

5 " » e >< 16 »

J

^^

1

^

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58 THE INFLUENXE OF FLUXES AND NON-FLUXES UPON THE CHANGES

TRANS. AM. CER, SOC VOLX BLEININGER AND -MOORE

CaCOj 3

5

7 9

II

13

15

17

19

FLINT 17

15

13 11

COM POSITION

3

7

5

i

1

TRANS. AM CER SOC VOLX

BLEININGEf? AND MOORE

FIG 4-8

CRAWFOROSVILLE SHALE 80% FLINT 8c CaCO^ 20%

C01CO3 Z 4 6 8

FLINT la 16 14- la

I

10 12 1+ 16 18 i.Q

10 9 6 4. 2 0

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS.

59

t=

X

= '

-

FIG 50.

;rawfordsville shale

flint-whiting

porosity.

1 0-° 5S #

H^ iT) ts. cr>

S *9 0^ «^ t \2 !2 —

^ , . . =

X

■^ 0-9

OO " " ° — cj rn -»■ "O

m

m-

l-ivi-

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^

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J

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/

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s.

/kiisoy Od %

i

5

i

UJ

>3 3 To

u. cDi-a:

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o

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i

JO ^ o >o rO

UJ

i = = ^ - §

o

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in

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:=^

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n

3

n

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L

r>

A i I s 0 y 0 d °/o

60 THE IXFLUKNCE OF FLUXES AND NON-FLUXES UPON THE CHANGES

TRANS. AM CER. SOC VOLX

BLEININGER ANDMOORE

4-0

35

30

25

20

I/) o

£•0

3

80

FIG.SOa. %GALESBURG SHALE FLINT-WHITING POROSITY

Kin 4 ,(C<»/-CIIMX CO/_\A/UlTIMr.

>

s.

"""^

X

2=11% " 9% »

/

\

V-

\

3 -- 7% " 13% '^-. 100% SHALE

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1

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k

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i 4-

2

!3

OS

06 03

CONES

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS. 61

ADDITION OF FERKK" OXIDE-FLINT.

Shales. Iii Fig. 51, sliowing the porosity curves of 80% Crawfordsville shale and 20% ferric oxide and flint, Ave observe at once that the reactions appear complex, and by no means continuous. In the Cone 2 curve we have three distinct minimum points. We also observe that the reactions, whatever they may be, begin at a low tempera- ture, since the curves lie very close together. With 6^c FeoOg even the Cone 01 curve has come considerably below tlie porosity shown in the normal shale at Cone 2. We observe in this connection the fact that at Cone 01 the shale shows a lower porosity than at Cone 2. This increase in porosity at the higher temperature appears to be due to vesicular structure, wliich is observed eyen before vitrifica- tion is reached at any point. With 16% FeaO-. the shale mixture reaches complete vitrification at Cone 2, at which temperature the normal shale has a porosity of 11%.

In a mixture of 759^ Canton shale and 257^ ferric

TRANS. AM CER SOC VOLX.

BLEININGER AND MOORE

*-0

30

»-

FIG 51. CRAWFORDSVILLE SHALE=807o FLINT+ Fez 03=20% • POROSITY.-

fctOj	^	♦	6 8 10	12	14-	16	m	20
FLINT	18	16	14 12 10 % COMPOSITION	8	6	4	2	0

62 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGES

oxide and flint, Fif>-. 52, we observe somewhat similar con- ditions. Complete vitrification is reached here as low as Cone 01, at which temperature the normal shale has a porosity of 12%. This point occurs with a mixture of 10% FCoOg, 15% flint, that is, with a ratio of 2 : 3.

The Galesburg' shale seems to behave more regularly than the preceding clays, and does not appear to produce the vesicular structure observed in the former. No decided change seems to take place at Cone 2 for the changes in the iron-flint ratio. Fig. -53.

The individual vitrification curves of these shales- iron-flint combinations are illustrated in Figs. 54, 55, 5(i.

Similar results have l>een obtained by "\\'orcester in experiments involving the production of nuxtures of red Bedford shale and ground Berea grit.

ADDITION OF FERRIC OXIDE-LIMB.

Shales. Here we observe that in a mixture of 90% of Crawfordsville shale, 3% FegOg and 7%^ whiting have

TRANS. AM CER SOC VOLX.

BLEININGER AND MDORE

FIG 52. CANTON SHALE 75% FLINT + FCsOa 25% POROSITY,

IN THE POROSITY AND THK SPECIFIC GRAVITY OF SOME CLAYS.

03

uJ O 1 z					/
		/		\
oc UJ			/		/
z z UJ					/	/
IC				I	(
	"-^ .		\	\,
			\'	\
						\
	LLI ■• go-
				Fl		01
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< I—

CD M

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OO^J,

li

-^^fi

c?

' MSOyOd %

64

THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CH.\NGES

FIG 55.

CANTON SHALE

FLINT- Fe^Oa

POROSITY.

u.

^

IM -t -^ « -

l-

-

fO

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X

? 7

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Axisoyod %

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS. 65

TRAN5. AM CER SOC VOLX.

BLEININGER AND MOORE

FIG 56.

GALESBURG SHALE FLINT-FezOj POROSITY.

N0.1.30%SHALE I7%FUNT 3%Fe?0.

2 '• 1+ " 6

3 •> 10 " 10

3

4 " 6 " 14 -J

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CONES

66 THE INFI.UENXE OF FLUXES AND NON-FLUXES UPON THE CHANGES

TRANS AM CER i'OC VOLX BlEININGER AND MOORE

FIG 57. CRAWFOFfOSVILLE 5HALE=90%. CaCOj + FeaOj-IO"'.- POROSITY.

1

III!

I

1

30

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CaCOj 9

3 4-5

7 6 5

.C OMPOSITION

TRANS AM CER 50C VOL X.

BlEININGER

AND MOaRE

40

FIG 58.

GALESBURG SHALE =90% '

CaCOi+Fe2.03-107«

POROSITY,

1 1 , 1 1 . , 1

1

c

5iae

06

30

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UJ

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V.

a:20

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IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS.

r.7

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All SO y od '=>/o

68 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGES

brought the vitrification down to Cone 01. Increase in ferric oxide causes the vitrification point to rise until the mixture, 9% FeoO-; and 1% whiting is reached, where we have a second minimum point. The Cone 01 and Cone 2 curves, it will be observed, are very close together. Fig. 57.

In the Galesburg shale conditions appeal* to be some- what different and we have, within the range studied, only one minimum point which is close to 6% Fe203, 4% whit- ing in the Cone 01 curve. In the Cone 2 curve it has ad- vanced to 7% Fe203 and S^c whiting. Fig. 58.

The Canton shale seems to be more sensitive to sucli j^dditions, as is shoAvn in Fig. 59, where it appears that the shale has been rendered vesicular in structure at Cone 2. It is especially peculiar that this should be the case, since Cone 01 does not seem to have produced vitrification. It is possible that the vitrification range is so narrow that it was missed in the experiments. Yet this seems hardly probable. The natural conclusion would be that the for- mation of ''blebs" took place before general vitrification set in.

In the individual curves of the Crawfordsville shale series, Fig. GO, a gradual change in the slope of the curves is noted, which tends to become smaller as the FeoOg in- creases. With the increase of the ferric oxide there is ob- served a peculiar retardation between Cones 06 and 03. indicating perhaps some phenomena taking place between the lime and the iron. Of course it is impossible to deter- mine just what this change is.

In the Galesburg shale series, Fig. 61, the gradation OH increasing the iron is smoother and not marked by the retardation noted above, excepting perhaps in the 4% whiting, 6% FeoO:^ curve.

The Canton shale series, Fig. 62, is not comparable with the two preceding series, owing to the fact that here we have but 80% shale with 20% lime and iron oxide. However, some facts are brought out. First we have the change in slope with the decrease in lime, and second, we obserA-e between Cone 01 and 2 a marked increase in poros-

IN THE POROSITY AND THE SPIiClFIC GRAVITY OF SOME CLAYS.

69

1

if

1

or

S

^ 2 . . . =

>0 ^ ^ o

Ui

a

z

^

^•i

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tf>

a

y

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a: to

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— 1M -O ^ vo t, to

6

S. to l^ -O * -^ fvl

— (vj K) + in ^ ^

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r-

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Ail9 0y Od "/o

70 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGES

TRANS. AM. CER. SOC

-. VOLX.

BLEININGER AND MOORE

45

FIG62.

80% CANTON SHALE

POROSITY.

NCI = 16%CaC0, 4%Fe.O,

z

40

4

2 . 10 "10 ■> 3 ' 12 » 8

^ . O . l->

^

z^

^

'^^

5« 6 '

6 " 14 • 2 " 18 <

3 35.

z^**^

="

;<^

^

( '

iOO*?

-o SHALE

1

\

M

7

30

^

w

IV

\

S,

\

V

lb

^

X,

I

A

5,5 3

^

V

/ #

20

>- h-

o

a:

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1

i

y

1

o 0-

0

1

^

>^

P

^ ^

r

5

I

/

6

\

y

09 06

CONES

03 01

IJV THE POROSITY ANU THE SPECIFIC GRAVITY OF SOME CLAYS. (1

ity which api)t'ars in cvciy curve, the cause of which must be soujiht iu the production of vesicular structure. It is pos- sible that vitriticatiou had set in at Coue 1, in which case it was niis.sed, since no burn was made at this tenii)ei-ature.

From the data presented in this paper the writers be- lieve that the method of determining the rate of the porosity changes affords a practical meaus of examining the vitriticatiou phenomeiui not only of natural elays, but also of body mixtures. The porosity method is essentially a practical one, and where it is desirable to know the niolc- ciilar changes, either physical or chemical, taking place, it must be supplemented by specific gravity curves represent- ing the true specific gravities as determined by the pycno- nieter, under the special precautions advised in this paper. Unless these determinations are made with great care they are of little value, since the changes involved are frequentl\ only of small magnitudes. The specific gravity curves eniplo3'ed in this paper, hence, are not close enough to admit of exact conclusions.

From the scientific standpoint, therefore, wherever the discussion of the molecular structure is involved, the true specific gravity curves are the main criteria of these -changes. At the same time it must be remembered that the true specific gravity is in itself the resultant of the physical and chemical phenomena clearly indicated in the first part of this contribution, and cases might occur where the rate change becomes zero, owing to neutralizing factors- These, however, seem to be the exception. The poi-osify curves are sul>ject to grave errors under certain conditions.

The maximum or minimum points, so important in the stu«ly of all fusion phenomena, niay frequently be detected by the porosity curves. Their determination is more exact if fixed by the specific gravity curve, since practically all physical or chemical phenomena are accompanied by a change in specific volume, and since nearly all silicates (not containing any borates) on the application of heat, as far as known, increase in volume.

The use of reagents such as have been employed in this

72 THE INFLUENCE OF FLUXES AND NON-FLUXES UPON THE CHANGES

paper seems to the writers to be of considerable value in bringing out and studying tlie differences in the chemical and physical structure of clays. Different clays will re- spond differently to the same reagent under the same heat treatment. To illustrate, every potter knows that there is a great difference between the behavior of English china clay and American kaolins. By heating each of these clays with, say, a mixture of 20^ flint and 15% feldspar to several temperatures, different porosity curves Avill be ob- tained, showing the distinct characteristi'" of each type of material. It goes without saying that the reagent, what- ever it may be, must be kept the same, both as to composi- tion and fineness, just as the cement manufacturers and testers employ a standard sand for their purposes. This would mean the storing of a considerable amount of such a material. The preparation of the test pieces also should be done under uniform conditions.

Another extremely important factor is the heat treat- ment, which should be continued long enough to establish conditions of equilibrium and should be noted as closely as possible with reference to cone temperatures. That the heating should be the same in each case is self-evident, since we know that we are dealing with incomplete reac- tions which differ for different heat treatments.

In this connection the need of a really satisfactory small laboratory test kiln becomes very apparent, and this problem awaits solution.

As has been said before, for practical purposes the porosity curves are amply sufficient.

There can be no doubt but that we must approach the study of our clay bodies and mixtures along this line, and before definite laws can be laid down a great deal of work must yet be done. This field has been barely opened, but it is hoped that the function of the several substances stud- ied will be indicated. What is needed most is the study of the simpler combinations.

In conclusion, the writers wish to express their in- debtedness to Professor C. W. Rolfe for having granted

IN THE POROSITY AND THE SPECIFIC GRAVITY OF SOME CLAYS. 73

the fiiiuls and facilities necessary for caiiyin*^ out this work.

DISCUSSION.*

.1//-. I'linit/: This jtaper cannot be discusserl af all a(le(|uately because of the mass of data presented. The curve form is probably the most lucid wa\ of preseiitiui;' data, but the mass of data is so confouudiuj:: that you oau not e.xpect one to follow il in the short time which lias been i»iven it.

There were a few points thoug;h that I noticed as lie went along; for instance, ])erhaps that iron did not seem to have acted as a flux, as we supposed it did, except in the role of a catalyzer. We noted the same thine: last year in the study of the microsco])ic sli<h's of burned shales, the iron separated out into definite crystals instead of com- bining with the silica. If iron combines with silica to any great extent it certainly would in a shale burned to a very dark chocolate color under both reducing conditions and great heat. Under ea<li of these conditions the iron sep- arated out into definite crystals. We have had data pre- sented here today showing that the iron, instead of fluxing the clay, seems to have acted as a refractory agent, prevent- ing the closing of the pores. The effect of iron on the specific gi-avify seems to be that to some extent, it holds it nj), if if does not iin-i'ease if. The same ju-oxcd to l»e tiMie with lime in lai-ge (|uantity. Lime in small (pianfifi<'s fends to deci-ease the density of clay by fusion, and hence a moleculai- arrangement of the fused constituent, and also by develojunenf of vesicular structure, but in excess of seven percent, it temls to increase the density of the mass. This is new to me, but T have no doubt it will be fruitful of new posfnlations when wo como to study the curves.

It has been noted that sand added to shale increased

*1 his paper was not read nor presented in its entirety: such portion that was presented was given e.xtemporaneously by Mr. Moore. Those whose discussed the paper have not had opportunity to see it as it appears above. — (Editor.)

(4 THE INFLUENCE OF FLUXES AND NON-FLUXES UION THE CHANGES

its tou<];liuess wheu made into the form of brick and used as a paver. Sand}' clays are as a rule better paving- matei-- ials than those containino- no sand ; and sand — not pure quartz — added to clay increases its toughness. You cannot, however, add lake or glass sand and expect this constancy in specific gravity; nor can you expect this constancy in the porosity changes with increasing heat treatment, indicated by the curves just shown to us. Von must have sand which is more or less combined, more or less in solid solution, as the chemists say, in order to have this steadiness of be- havior in regard to fusion. The behavior of silica in de- creasing the specific gravity without causing definite flux- ing action is interesting. When a quartz crystal expands on heating it breaks, molecularly, and, at the same time, the molecules increase in volume. Notwithstanding the increased contact surface that follows as a consequence of this increase in volume, silica did not appear, in these ex- periments, to act as a flux.

I noticed that Cone 2 seemed to be the critical point in all mixtures, the point at which fusion begins to progress most rapidly. So Cones 2 and 3 can be said to be quite critical temperatures for most clays, if not for all clays and mixtures.

The behavior of kaolin when added to shale is most interesting. It seems to cause a fluxing action in small amounts and a refractory action in lai'ger amounts. What is a flux? We have been used to classifying the bases, lime, magnesia, etc., as fluxes. We classify Cornwall stone and feldspar as fluxes, and clay and sand as refractories. We have an instance here of clay, a very refractory material, acting as a flux Avhen mixed with shale. How can we harmonize this with our definition of a flux? It seems we ought to have a different definition from that we have been using.

r ^.:.i ■■if; *,

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UNIVERSITY OF ILLIN0I9-URBANA

I 3 0112 052567101

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