SOLID SOLUTION PHENOMENA IN THE VARIOUS FORMS OF CALCIUM ORTHOSILICATE

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THE PEM'JSYLVANIA STATE COLLEGE The Graduate School Department of ceramics

SOLID SOLUTION PHENOMENA IN THE VARIOUS FORMS OF CALCIUM ORTHO SILICATE

■ A Thesis By Samuel :Zerfoss

Submitted in Partial ■BxlfillBient of the Requirements: for the Degree of Doctor of Philosophy

August 1942

TABLE OF CONTENTS

Page

ACKNOWLEDGMENT X* II.

XHTRO-DIICTxOM

.. ... .

THE COMPOUNDj Ca2SI04

1

. . . . . . . . . . . . . . .

(a) The History., in Brief of the Research on the Calcium Silicates . . . . . . . . . . . . .

5

(b) Natural Occurrence and Petrology

6

.. ...

(c) General Chemical and physical Properties . . 1*

Composition 'andPolymorphic

2»

Densxty

3.

X*>ray Proroerties and Crystal Structure of

. . *

OgS and- x t s

4»

5.

Forma . . .

» # :. . . .. . . .

i^oxTns -

« » .

. . .

. «

« .

. .

8

3 .3

16

Table i . » « »

♦ *

16

The Heat of Inversion and- Other Thermal » « • : Constants .of Its Ftorms * «

20

. * » « . ». # . »

GzS Figures' ! and. II • Table XI . . . . .

»

. . » .

i%« General The Inversions of C 2S

* .. .. ... . . • * » •

The Alpha to. Beta Inversion

. . . .

• ®

20 . 22

;y3 0 *-* •-■ t» © © »

24 31a 34

♦ *

0 ®

36

♦ •

• .•

36

• • ©

0 ©

45

.

THE-SOLID-SOLID'.CHANGE

E.

8

The Grystallographic -and Optical Proper™ ties o.f .the..Forms' of -C3S . *.. . . . . .

and. Si02

XII.

5

. • «

0 * ■ 45 o-rt'o* i. ,tbi >:> 1

ii

igo The Beta to Gamma In-version IV.

CsS IN INDUSTRIAL PRODUCTS &• G^S in Cement Clinicer

.*•

B* C'3S in Industrial Slags

*

55 55

« ®

57

V® EXPERIMENTAL P A R T .......... . Preliminary Melts

48

• • • • > « • • »

C® Calcium Orthosilicate in ■Refractori es

A®

♦

»»»•

* » • » ®

........

.®

64 .

• • . * . • • •

R cdv Materm i s

» ® « * * »

»®

Prepara‘la.on

*•»«»»»

» ®

70 70 70

® « « ® « ®

»

9

70

■ The Various Compositions, their-Treatment and'-some Observations cn their Behavior ® .® » »® . . 71 B»

Equipment and Technique >

. .*'

Figure III and IV

• . . .

xcLgare V

® » * « ®

®»®»®

C* The S^miples

• ® ®

.« •

• •

75

. .. .

®.

® .

78a"

« *? ®

*•

® «

32a.

® ® « ® ®

Preparation of -Samples Table III

®

• .®. •

• ® ®

84

* « •

® » © ®

D.» Thermal'. Study of Samples

» . , » . » . »

®

86

® « © * ® * »

®

36 87

Procedure for.Making- Heating Curve of the Aloha oO J3etu Xnversxpn © ® ® ® * ® « *» ®

37

Results of Heating Curves - t h e

o

a

i n

p

l e

s

C

o

n

. b

a

x n

x n

g

Samples Containing GaFa

p

^

• 0

~

• #

.

.

®

».

» .■

©

*

. ®

»

A

.

88

®

*

0

.

0

103

Description of a Keating and Cooling Curve of Sam­ ple L29-6, 17 Per Cent CaF2 . 105

Page

Figure V and VI • Data on OaP ^ Melts plutti X * ® * » ©

® * ®© ® »

®

®®

»®

«» ®

® »

©®

♦®

* a*

® * < s © © ® ® ® © ® ®

® ® * ®

105 109 115a

The Influence oX Various Oxides on the Dusting Benavi,or of G^S ® © ® ® ® ® ® ® * ® ® ® « ® ® ® © US

VI®

Attempts' to Cause In-version of Inhibited Prepar­ ations * ® * ® * » ® * » « ® » ® w © » 4>»«0

123

The Thermal Decomposition of Certain Silicates

•

127

* ® .

1-32

DISCUSSION AND SJivSvI&RY The Alpha—Beta Inversion . . . The Beta to Gamma Inversion BIBLIOGRAPHY

® «* ® ® ®

® ® ® ©

• - 132

•

137 ® © « « © © * ® «

IAS

ACKNOWLEDGEMENT

This ysseai'eh was carried out under the immediate direction of ]}r»

h»

-M* Davis®

The writer is..especially indebted "to this close

friend for his excellent advice and assistance* The writer wishes to express his appreciation to Dr. N. Tf® Taylor, Dr® W» -.Wsyl, and Dr. N* J® Kreidl for the suggestions they offered concerning the fundamental problems involved in this work .and for assistance in analyzing the data® The writer wishes to acknowledge the excellent work done by Fr* Sheoder and his machine shop staff in building the furnace used in this .work*, Mr® M*. A® Knight supplied certain details of construci ion of the furnace and its .equipment*

The writer had the pleasure of discussing the thesis problems T\l3 OVi3 f with Dr. R. II. Bogue end his staff at the/bureau of Standards® His discussions at this institution with Dr® H® Insley, Dr® Q. w* Hard and Dr® W» G® Taylor were most helpful*

I.

INTRODUCTION'

This research has as its purpose the extension of our knowledge of the properties of calcium orthosilicate especially with reference to the solid solution relations shown by this compound and the effect of such solid solution upon the various inversionsThe polymorphism of calcium orthosilicate has been known since the last half of the 19th century and while there is essential agree­ ment, among investigators, on the properties of the various forms and on the stability ranges of these forms, not too much is known regard­ ing the characteristics of the various inversions and the manner which they respond to changes in external conditions®

Any additional infor­

mation about the inversions and their modification would be of interest in the study of the theory of changes in the solid state® From a practical viewpoint, since calcium orthosilicate is an im­ portant constituent of cement clinker, various industrial slags and of the recently developed lime-magnesia-silica refractory series, new in­ formation concerning the inversions would be of benefit to the future research in these three fields. The original plan of this research was simple®

It was proposed

to study the effect of addition of P 2O5 on the alpha to beta Inversion and thus extend the data previously published by Flint and Wells (40) on B3 03 additions and Burdick (24) on Fe2 C>3 additions®

These authors

found that such additions lowered the inversion temperature (as detect-

2

ed by heating curves) and attributed the lowering bo solid solubion of bhe added oxide in calcium orthosolicate*

The similar!by in bhe

behavior of B2 03 and Ps^g in inhibibing bhe inversion of bhe beta to gamma form led bhe present writer to believe that P 2 0g should have some effect on bhe higher temperature, alpha bo beta, in.version® Thus it was planned to study bhe inversion temperature (alpha­ bets) of calcium orthosilicate in the presence of various concentra­ tions of PsOg®

Such a study should provide a curve wherein tempera­

ture would be plotted against P^Og, dissolved presumably in the sili­ cate*

An extension of this data would include & study of the P 2 O5 dis­

solved in a calcium orthosilicate that crystallized from a simple slag melt (calcium orthosilicate-melilite, etc. )»

Thus one could, study the

distribution of P 20 c within a slag mineral assemblage. As will later be recorded, this study was not successful*

Numer—

our difficulties were encountered in establishing the calibration curve and in fact detecting the inversion, even in pure preparations.

As a

result of the numerous trials and failures throughout his study many pieces of data, concerning the two inversions were recorded.

This data

has been supplemented with other observations with a view to assembling a possible mechanism of the inversions and their response to chemical and physical influences.

Thus, although the original plan was not com­

pleted, the writer believes that the various minutiae assembled herein vail be of interest with reference to the unanswered problems of solid— phase inversion phenomena.

3

Definitions and Symbols* The compound Ca2 Si0 4 is here referred to as calcium ortho­ silicate.

Of the two possible names, dicalcium silicate and calcium

orthosilicate, the latter is justified on the grounds of both the chemical and the more recent X-ray basis since the crystal chemists have shown that the ortho silicates have a distinctive lattice with Si04 as a discrete unit. As mentioned before, calcium orthosilicate when contaminated with sma.ll amounts of P 20 5 or B2 03 will not invert to the low tempera­ ture (gamma) form on cooling.

This inhibition of the inversion has

long been attributed to solid o-lution of the respective oxide in the silicate lattice although no explanation has been given of the mechan­ ism of the inhibition. In the literature such inhibited preparations are said to be "stabilized. "

The use of this word raises a fundamental questions

Are such impure preparations existing below the stability range of the pure compound in true thermo dynamic equilibrium or are they in a state of metastable equilibrium wherein the rate processes are so slew that the establishment of equilibrium is impossible within our time? The word is used frequently in this thesis with the understanding that the question of the stability of such preparations has not yet been satisfactorily answered. It is coiranonpractice in the cement and ceramic literature to simplify the writing of silicate and other oxide compounds by the use

4

of symbols.

The-following symbols are used in this thesis: s

for

Si02

H

for

Fe2 03

M

for

MgO

W

for

FeO

C

for

CaO

A

for

ai 2 o3

B

for

bso3

P

for

p*°5

Thus tricalcium alumin— ate is written CsA* etc.

These symbols are identical with those used in the literature with the exception of the symbols for the iron oxides. ture Fe20s is F and no symbol is used for FeO.

In the litera­

The symbols listed

above make both oxides translatable into the abbreviations* using the first letters of the mineral names of the respective oxides.

5

II.

(a).

THE COMPOUND, Ca2 Si04

The History, in brief, of the research on the calcium

silicates* Berthier was the first investigator to study the composition of the calcium silicates.

In 1822 he made preparations in the Ca0~Si02

system snd tested the fired products for free lime as a means of fixing the composition of the compound. CaO SiOs*

His compound had the formula

Natural calcium metasilicate, wollastonite, was reported

as early as 1793. Later investigators gave various formulas but it was not until 1890 that Le Chatelier, in his thesis, announced the preparation and established the identity of another member of the series, namely, cal­ cium orthosilicate.

He states in his book (82) ~

"The compound bearing this formula ought to belong to the family •of p er idotes; it d.ws not exist in nature, and has not until now been obtained in the laboratory.

I have produced it by the direct fusion

of silica and lime In suitable proportions.

The temperature necessary

to obtain the fusion is near the melting point of wrought iron." Le Chatelier also described the dusting or inversion of this com­ pound and was one of the first to give a microscopic characterization of the compound as it occurred in cement clinker. He reviewed the observations on the spontaneous pulverization of slags and clinker and satisfied himself that the dusting could be at­ tributed to C 2 S.

To reach this conclusion he varied the MgO content of

6

a mixture of CaO, MgO and Si02 in orthosilicate proportions and noted that the maximum dusting effect occurred for the pure C2S

and

he re­

peated the experiment under Hg to eliminate the previously suggested hydration theory of dusting* Bogue has listed other details of the history of this compound

(11). In 1905, Eoudouard (27) reported that the freezing point curve in the C-S system as determined by a cone study, consisted of four eutectics and three maxima (compounds)*

The maxima corresponded to

the metasilicate, the orthosilicate and the trisilicate. In 1906, the members of the Geophysical Laboratory published their first study on this system (27) and the data on the eleven solid phases they found in the C-S system are in use today with minor modi­ fications.

This paper vfas followed by others and these will be discuss­

ed in detail in a later part of this review. Robson and Vvlthrow (99) have summarized the history of the re­ search on lime-containing refractories. In 1929, Tilley (119) reported the first natural occurrence of calcium orthosilicate as the mineral, lamite. Recently Seil has given an excellent bibliography on the calcium and related orthosilicates (107). (b).

Natural Occurrence and Petrology.

A mineral, lamite, whose composition is C2S was found by Tilley (119), in 1929, in a limestone-dolerite contact at Scawt Hill near Larne, County..

7

Antrim, Ireland.

It was found associated with spurrite., merwinite,

spinel, gehlenite, wollastonite and the recently reported rankinite (C3 S2 ).

The optical properties, listed in Table I, show it to be

alpha CsS but the indices are lower than those of either beta or alpha C2S from, artificial prepare tion s.

Under shock or during thin-section

grinding the lamite dusted to a fine powder, identified as gamma C 2 S* Since the lamite occurred as fine grained material that was intimately associated with other minerals its durability was probable due to the environmental, restraint.

No P 2 0g, B2O3 or Cr2 C>3 was reported in the

analysis of the lamite or the spinel and no apatite was reported In the rock® Shannonite, first described by Paul as a natural mineral of C2S composition, was later shown to be monticellite (1 2 0 )® Bowen (14) has discussed the formation of larnite as a step in the metamorphism of siliceous limestones and dolomites.

He outlines

thirteen steps in the progressive metamorphism or decarbonation of a. siliceous limestone taking place at successively higher temperatures for a given pres sire®

For any one temperature Interval there is a def­

inite mineral assemblage and above that Interval the assemblage is changed to omit one miners! and include one characteristic of the higher temperature®

Lamite and spurrite are present in phase assemblages charac­

teristic of the highest temperatures found In nature®

That lamite is

rare merely Indicates that such temperatures arenot common in nature, while spurrite, also occurring at a lower temperature interval is more

8

common*

In the case of dolomite, merwinite is added to the list of

the high temperature minerals*

The easy hydratibility and the dust­

ing behavior of C2S may in part account for its rare occurrence. (c}» 1.

General Chemical and Physical. Properties. Composition and Polymorphic forms*

Calcium orthosilieate contains 54.88 per cent Si02 and 65*12 per cent CaO®

It is knov/n to possess three low symmetry polymorphic forms:

alpha C2S is stable from 1420°C to the melting point, 2130°C^ beta C2S is stable from 67 5°C to 1420°C while gamma C2S is stable below 67 5°C. (27, 96). 2®

Density.

The densities of the various forms are given by Day et al (27) and checked by Sundius (112). Density Alpha Beta Gamma

3*28 2.974

The Inversion of alpha or beta to gamma C2S involves a consider­ able change irx density.

On the volume basis there is a 10*3 per cent

increase In volume*

3.

The X-ray properties and Crystal Structure of C2S and its Forms*

Brownmiller and Eogue (20), Harrington (53), Hansen (50), Kondo et al (71) and Brandenberger (16) have presented data on the powder patterns of

9

the various modifications of C 2 S» Browmniller and Bogue applied the X-ray method to the study of cement clinicer as a means of identifying the various phases.

They

pointed out that not less than 15 per cent beta C 2 S could be detected in a mixture since it had so few intense lines.

Rait and Green (95)

confirmed this conclusion and pointed out that C3 S had several lines that are close to those of beta C 3 S« Kondo et al (71) gave the data for pure C2S as well as C2S con­ taining 3 per cent CrzQz and C2S containing 4 per cent H3 BO3 .

Small

differences in the spacings were shown| the Cr2 0s increased the dis­ tances and the B2 O3 decreased them. Examination of Brandenbergerfs powder pattern data on alpha and beta shows that there is some difference in the interplanar spacings of the two forms (»Q1~£-S A) and that there is a difference in the intensity of certain corresponding lines.

The difference however is not large

and might be attributed to the impurities in the sample since to get alpha he added some AI3 O3 and Cr2 03 to his preparation* No complete picture is available on the crystal structure of C2S and its forms because no one has been able to grow single crystals of C2S and one cannot precisely determine the structure of orthorhoinic crystals from powder patterns.

Herein will be recorded the various specu­

lations concerning the structure based upon the comparison of C2S with other silicates. The characteristic tetrahedral arrangements of four oxygens around

10

a central silicon atom is preserved throughout all of the silicate lattices.

Variations in structure are obtained by the various com­

binations and linkings of these tetrahedral units. cates the tetrahedral unit is isolated^

In the orthosili—

that is* the four oxygens around

a silicon are not linked to any other silicon,, the silicon oxygen ratio is 1-4 and the cation silicon ratio is 2-1*

Thus the structure Is com­

posed of these tetrahedral units and cation-oxygen units* The orthosili cate type is generally character! zed by the lack of a pronounced tendency to a fibrous or platy structure and hence the crys­ tals usually assume an equidimensional habit. (Berman 7).

The members

are generally hard, have a high density and a high refractive index be­ cause of the close packing* TVe are Interested in the olivine group of orthosilicates since C2S corresponds more nearly to this family.

According to Tilley (119) C2S

Is not a member of this family although Winchell (128) points out that gamma C2S has indices, and density in the proper range for an olivine mineral.

The limited irascibility of Ca In this series Is significant.

The ionic size of Ca is larger than that of Fe, Ivlg or Mi and apparently so much larger that the Ca cannot be accommodated in the structures that permit such extensive mutual replacement of Fe, Mg and iv'n. It is of interest to consider the replacibility of 'the cations in the orthosilicates, metasilicates and oxides of Fe, Ivin, Mg, and Ca.

As

far as is known from the literature complete solid solutions exists be­ tween the binary and ternary mixtures of Fe2 Si04 with Mg2 Si04 or Mn 2 Si04

11

and FeSiOa with MgSi03 or MnSi03 and for the binary and ternary mixture of the oxides of Mn, Mg, and Fe. pounds is definitely limited.

The solubility of Ga in these com­

In the case of the orthosilicates Ca

forms intermediate compounds of definite composition - CaFeSi04, MgCaSIG4 and GaMnSi04*

In the case of the metasilicates similar inter­

mediates are formed — Calvin (Si03 )2, CaMg (Si03 )2 *

In the case of the

oxid.es, no solid solution of Ga in FeO, MnO oi' MgO e x i s t i n s t e a d there are intermediate compounds of Ca with Fe and Mn in a higher state of val­ ence and a eutectic relation with MgO* It was found by Goldschmidt (44) that the volumes of the Individual ions are practically constant and can be represented by the content of spheres of action*

Yjhen two elements are considered as in the case of

Mg and 0, the number of one kind of atom - 0, that can surround or be in contact with another kind of atom is fixed by the geometrical relations of the radii and by the relative order of magnitude of the charges on the respective atoms.

Charge enters into the picture only when the dif­

ference in charge density of the two elements is great. The number of surrounding atoms or the coordination number, C.N., is thus fixed by the ratio of the radix* In the case of atoms surrounded by oxygen the coordination number depends

on the radius of the other atoin«

For atoms of the size up to

*2 A° (C,B) the C.N. is 3; for atoms of size *3 -

.6

C.N. is 4| in the case of Mg, Fe and Ti (radius .6 -

A° (Be, Si, Al) the 8

4°) the C*M. is

and finally Ca having a. radius of 1.06 A° has a C.N. of

8

or more*

6

;

12

The transition from one radius range to another is not marked and atoms on the borderline often show either type of coordination, e. g® , Mg and Al* As the coordination number gets larger the coordinating force gets less since the atom is more isolated and assumes a more inactive role® At higher temperatures the C.N* should be less because of the in— creased vibration of the atom and because the atom can assume a more active role in the structure* We can recognize two types of cations.

Those of the "first

category” (Bussem 115A) have small size, high charge density, low C.N® and play an important role in the network of the skeleton of the structure^ that is, they are "active" cations (Brandenberger 17).

Those cations of

the "second category" have large siae, low charge density; high C.N® and serve to fill holes in the structure*

These are referred to by Branden­

berger as "inactive cations." Brandenberger (17) in an effort to explain the difference in physical and chemical properties &f the various forms of C2S proposes that there is a difference in coordination number of the calcium in the high and low temperature forms® Calcium is normally embedded, as a cation of the second category, C*N* 6-3, and plays a rather inactive role in the holes of the structure. At higher temperatures besides this inactive interstratification, an active role of Ca, as a cation of the "first category" is possible (Bussem)*

15

That Ca can have a lower C.N* is shown by the unusual compound (Ca*Si04)~ Ma2 wherein Ca has a C.N* of 4. At higher temperatures the ionic radius is larger because of the increased vibrations of the atom and the atom p r o b a b l y shifts from its shell to a more prominent place in the network.

This means an extension

of the network since more ions are taking part. Brandenberger (17) divides the calcium silicate series into several groups with the following properties* 1,

Alpha and beta - C2S Ca as an active coordinating center — C*N« *“4 Refractive index above 1.7, close packing, high density Molecular volume is smaller than the sum of the volumes of constitute oxides

2®

Gamma - C 2 S, C3 S2, CS Ca as a secondary embedded cation — C«N. 6-3 Refractive index less than 1.7, lower density Molecular volume greater than the sum

of the volumes of

the constituent oxides On the basis of these considerations Brandenberger explains the ability of the high temperature forms of C2S to hydrate and the inability of the other silicates to take on water.

The act of hydration in beta

or alpha C2S is the same as the act of inversion of these forms to the stable gamma farm since both operations involve an increase in C*M. of the Ca in the orthosilicate.

In alpha and bets-. C2S the Ca can play an

important role in the lattice and is thus able to attach itself to K 2 0

14

groups and attain the stable higher coordination.

Gamma CsS, stable of

itself does not possess this property, of ready hydration* The possibility of several types of coordination lends itself to the explanation of the numerous Ga compounds found in the various sys­ tems and the strong tendency of these compounds to exhibit polymorphism as compared with the other cations® Examination of the published data on the various compounds of the alkaline earths together with Mg shows that Ca-compounds exhibit polymorphism more frequently than do any other element in this group.

The

following data have been prepared from Mellor (87) and the recent Tables of Birch et al (8 ).

In some cases the data are probably unreliable. The

table includes both the enantiotropic and monotropic inversions but omits reference to all hydrated compounds* LIST OF SOLID PHASES IN SINGLE COMPONENT SYSTEMS

One Phase BaO, SrO, MgO

Two phases

Three Phases

CaO ?

Ca, Ba, Sr» Mg fluorides hydroxides nitrates Ca, Mg, Sr, chlorides

BaCl2 ?

Ca, Mg, borates Sr, Ba, silicates

C s , MS

C2s

BaS04 SrSQ4

CaS04

Ca, Ba, Sr, Mg sulphides bromides

15

List of Solid Phases in Single Component Systems (Continued)

One Phase

Two Phases

Three Phases

Barium aluminates

CgAa, C3 A 5

MgC03

C3P SrC03

? CaC03 (4) BaCOs

It is also of interest to tabulate the number of intermediate solid phases occurring in the various binary systems of the alkaline earths and other oxides.

These data were taken from Hall and Insley (49)

and includes the other divalent oxides, Mg and Zn. Alkaline earth oxide

MgO

CaO

SrO

BaO

ZnO

Si02

5

7

4

2

1

Fe30 3

1

2

1

AI2 O3

1

4

3

2

1

B 20 3

3

4

■?

?

?

8

17

P? Oi

5?

3?

?

1

?

1

Again it is seen that Ca is unusual in that it has the largest number of intermediate compounds in this divalent group. There are several observations in the literature on the substi­ tution of P for Si atoms.

In .1941 Bredig (19a) suggested a new group

of isomorphous compounds AsXQi4.

According to him the alkali sulphates

le 2 S04 constitute with the alkaline earth phosphates (Me,MeMP04) and with Caf>i0 4 (modified by phosphate as in slag) a new group of compounds

IS

■with a simple hexagonal unit cell containing two molecules.

He pre­

sented lattice data on the high temperature modifications of these compounds and demonstrated a marked

similarity

of structure.

He also

stated that the high temperature forms can be stabilized by substances which are insoluble in the low temperature phase and must be precip­ itated for transformation.

Klement (69) has presented evidence along

similar lines* 4.

The Crystallographic and Optical Properties of the Forms of C 2 S*

Table I contains some of the original determinations of the opti­ cal properties of the forms of C2S found in pare preparations or in in­ dustrial products.

Several other crystallographic observations m i l be

listed here. One of 'die most interesting properties of alpha and beta C2S is the polysynthetic twinning exhibited by these forms. Le Chatelier and Tomebohm (11) were the first to notice this property and later Wright used it as a diagnostic px'operty to distinguish alpha and beta..

Dyckerhoff (31) could not check Wright’s observation

that alpha could be distinguished from beta on the basis of the lack of complex twinning although, as other criteria, he found that alpha had a higher double refraction and that beta possessed some hairlike striations and a cleavage parallel to the prism axis® According to Sunclius (112) the alpha form is characterized by several cross sets of fine polysynthetic bands meeting at a steep angle® In oeta C2S there is but one set of such bands sometimes seen in sections

TABLE

Phase

A lp h a

i

OF

THE

Compo sition

System

A

C '-a s

>7?o r t r .

VARIOUS

H a b it^

FORMS

C leavage

OF

CALCIUM

C olor

n oC

H

S

'fctsrrvC %.-rro~to/ —

it

A

Ctn&y

H

A

it

C

C%S

ytt

B e ta

A

l
3

1-7i f

7

ZtxSiP

o /7

l.h 3

Few data are available on this system.

Several calcium

chromites are known but no ternary compound has been reported.

The

limited solid solution of Cr 2 0 3 in silicates has been suspected tryseveral investigators.

Budnikoff and Feijin (21) reported an high

index ”aliten (C3 S) phase (n—1.745—60) in a dolomite—chromite-quartz brick.

Phillips (94) reported a C2S phase in a similar product that

was green colored and according to him contained Cr 2 0s in solid solu­ tion.

According to Dana’s System (42) natural diopside may contain up

to 2.8 per cent Cr2 0 3 but this datum is old and the possibility of picotite contamination of the sample must not be overlooked.

In 1913,

Doelter (29) attempted to reproduce natural chrome diopside by firing an artificial preparation to high temperatures and cooling slowly.

He

reported one such preparation containing a homogeneous diopside that analyzed 2.95 per cent Cr^Oa*

It must be concluded frcm these fragments

33

that the solubility of Cr 2 C> 3 in silicates is quite lovr.

Hess (55)

examined natural pyroxenes and reported that all examples of diopside thus far examined contained substantial amounts (near

1

per cent) of

Cr 2 0 3 « Kondo and MotekL (72) reported that Cr 2 0

3

forms a solid solu­

tion -with C 3 S as indicated by microscopic examination. k.

The System C-S-MnO

Wo complete data are available on this system.

Kallenberg (64),

Tokody (14) and Greer (45) reported a complete series of solid solutions between tephroite and C 2 S»

Kallenberg, on the basis of extrapolated

density measurements concluded that gamma C 2S was the end member of the series while Tokody found a minimum in the system at 90 per cent Mn 2 S-

Greer agreed with KallenbergBowen et al, by comparison with the C-VV-S system suggested that

there must be a beta as well as a gamma series of solid solutions. In none of these.investigations did glaucochroite appear as a phase-

Schoenlaub (103) was able to synthesize this mineral and the

writer has confirmed this synthesis-

Much additional work is required

to establish relations in this system. 1.

The System C-S-Alkalies

The binary join C 2 S—IdSi04 was worked out by Schwarz (48) in a rather qualitative fashion. 3—2.

Two ternary compounds were reported 2—3

Taylor (117) has investigated part of the orthosilicate join in

the system K 2 0—C—S.

He reports a compound K 2 0g3Ca0 12Si0 2 between C2S

34

and KCS.

The compound has an X-ray pattern distinct from C 2S, opti­

cal properties slightly lower than beta C 2S, forms overgrowths on it and appears to be pseudomorphous after it.

One gram of K 20 can react

with 21.9 grams of C2S to form 22.9 g. of this compound. concludes that this compound is a solid solution.

Bredig (19a)

Xn the same system

Morey et al (88) reported a lowering of the indices of C2S by solid solution. m.

The Systems C-S-Other Oxides

Several minor observations are available concerning other oxides and their relation to C2S»

Torpov and Konovalov (122) have studied

the ortho silicate join in the system C—S-Ba but no data were available (56) to the writer. Eitel states that ZnO has no effect on the dusting of beta C2S. Spurrite, 202803003, has been synthesized by ELtel (55) at tem­ peratures in excess of 1300°C and pressures of 120 atm. spurrite melts incongruently at 1380 °C.

The synthetic

The natural mineral inverts to

the synthetic form at 1200°C. n.

The System G-S-H20

Since this system is the fundamental one involved in the setting of the cement minerals it has been given considerable study.

Flint,

McMurdie and Wells (41) have made a careful study of the phases in this system, their synthesis and stability under various conditions of tem­ perature and pressure.

A long list of hydrated calcium silicate minerals

can be found in the mineral handbooks.

Since most of these minerals were

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