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The silicates in chemistry and commerce asch asch



















DR. W. A S C H


A L F R E D B, S E A R L E
. "






All rights r&»erved


The Chemistry of Carbon and Silicon








Historical Eeview of Existing Theories concerning the Constitution of
the ATinninosilica/tes and other Silicates
. . .
The theories of Beizelius, Smithson, and JDo"bereiner. The theories of
Wartha, Haushofer, Safarik. Tscherrnak's Felspar Theory. The conception of the acid nature of aluminosilicates by Bonsdorff, Scheerer, Berzelius, Badecker, Odling, Wartha, and Bratms. The acid nature of alumina
in aluminosilicates according to Vernadsky and the attempts made by
him to devise a general Chemical System of aluminosilicates. Modern
theories of alurninosilicates, including those of RarnrnelRberg, Groth,
Clarke, Tschermak, Sawtschenko, Goldschrnidt, Bombicci, Brauns, Mellor
and Holdcroft, "Vernadsky, Pukall, Morozewiez and Dalkuhara.



Critical Eraminaxion of Existing Theories concerning Alumina-silicates
Are the aluminosilicates salts of the silicic acids ? Are the aluininosilieates double salts ? Are the aluminosilicates molecular combinations 1
Are the aluminosilicates isomorphous mixtures 1 Are the aluminoeilieates complex acids or the salts of such acids ? The chemical nature
of the complex acids and their salts as shown by chemical and physiochemical investigations. Ostwald's definition of double salts and complexes and the behaviour of silico-molybdates and siilpho-rnolybdates in
aqueous solutions. The course of reaction in the formation of complex
acids according to Blomstrand and Friedheim. The disadvantages of Blomstrand and Friedheim's theories. The facts for and against the complex
nature of the alurninosilicates. The results which follow from the various
theories concerning alumiaosilicates. Clarke's formulae for aluminosilicates. The constitution of Phakelite according to Groth, Rarnmelsherg, Thugutt, and Vemadsky. The constitution of .Potash Felspar
according to Tschermak, Groth, Clarke, Thugutt, Bammotoberg, Wartha,
Yemadsky, Zulkowski, Haushofer and Mellor and Holdcroft. The results
of the foregoing critical examination and the possibility that the opposition of some hypotheses to the complex nature of the aluminosilicafces is
only superficial.

A Hypothesis concerning the Bonding of the Atoms in Aluminosilicates
and Allied Compounds

Two new radicals—He^rite and Pentite. A structural chemical representation of the complex aluminosilicic acids arm' their anhydrides based on
the use of hexite and pentite radicals of silicon and aluminium.




The Consequences of the "Hexite-Pentite Theory," and the Facts
X The Reactions during Double Decomposition
Lemberg's researches.
II. The Genetic Relationship between the various Aluminosilicates
The researches of Lemberg, Thugutt, and Friedel. The Pseudomorphons processes. Table showing the changes observable in alumiriosilieates in nature.
III. The Possibility of a Chemical System of Aluminosilicates
The Clintonite group. The Mica group. The Scapolite group. The
Orthochlorite group. The Tourmaline group. The Felspars.
IV. The Variable Chemical Behaviour of part of the Aluminium in
Kaolin, Nepheline, and in the Epidotes
The variable chemical behaviour of part of the hydroxyl in the Topazes
and of the aluminium in the Granites.
"V. The Minimum Molecular Weight of Aluminosilicates
The minimum molecular weight of aluminosilicat© in connection with
Lemberg's researches. The minimum moleeulai weight in connection
with Thugutfc's work on potash, felspar, the mesolites, and the socialites.
VI. The Constitution of Andesite






VII. The Possibility of Isomerism
. . .
Basic Isomerism. Ring Isomerism. Isomerism in potash and soda
felspars. Two isomeric sodalites.
VIII. Water of Crystallisation and of Constitution; Basic and Acid
Water .
. . .
The structural formulae of the Zeolites : Xaumontite, Thomsonite,
Hydronephelite, Heulandite, Episfcilbite, Stilbite, Faujasite, Scoleszites,
JToresite and Natrolite, etc., according to Clarke, Friedel, Mallard,
Binne, Damour, Sommerfeldt, van Bemmelen, Doelter, Henry, and







IX. Prognoses
Base Prognoses. Ring Prognoses. The theoretically possible Ardennites. The theoretically possible Sapphirines, The structure of Howlite, Avasite, Milarite, Ptiolite, and Mordennite.


X. The Constitution of the Complexes of Molybdenum and Tungsten
a- and jS-Complexes of Molybdenum and Tungsten. Evidence in support of the structural chemicaJ. representation of rnolybdic and tungstic
complexes. The results of researches by Friedheim and his associates.
The action of rnolybdic acid on various vanadates and of vanadates on
molybdates. The action of molybdie acid on various phosphates.
The action of molyfcdic aoid on arsenates. The genetic relationship
between the various vanadinomolybdatefl. Tiie most stable types of
vanadinomolybdates and aluminosilicates. The genetic relationship
between a- and /S-phospho-molybdo complexes. The genetic relationship between the arseno-molybdates. The different behaviour of the
compounds 2 R20 • V2O5 • 4 WO3 and 4 R2O • 3 V2O6 • 12 WO8 towards acids in the light of IViedheim's and the Hexite-Pentite theories.
The- constitution of the Silicotungstates. The isorneric silicotungstio
acids and silicotungstates. The dimorphism of the potash salt K20 •
2 HaO • SiOa • 12 WO a - 7 HaO in the light of the Hexite-Pentite theory.




Systematic Review of a Series of /^-Complexes of Molybdenum. and
Tungsten .
. . .
Aluminornolybd&tes H2O-AI2C>3- 10 Mo03, Borotungstates 2 R,2O •
B2O3 • 10 WO8« Silicotuiigfltfttes 4 R2O • SiO2 • 10 "WO3. Platinomolybdates 4 E 2 0 • PtO2 • 10 MCoO3. Platinotungstates 4- R,2O - PtO2 •
10 WOs. Aluminoniolyhdates 3 H2O • A12O3. 12 Mo03. Chromoxnolybdates 3 R 2 0 • Cr-2O3 • 12 MoOa. Borotungstates 4 E2O • B2O3. 12 WOS
Silicon) olybrlates 2 R2O • SiO2 • 12 MoO3. Silicomolybdates 4 R20 •
SiO2 • 12 MoO8. Silicotungstates 4 R2O • SiO2 • 12 WO3. Zirkonomolybdatos 2 E 2 0 • ZrO* • i'2 MoO3. Titanomolyb dates 2 RoO • TiO«> •
12 MoO3. Phosphotungstates 2 R2O • P2O5 • 12 WO3. Iodoniolybdates
5 RoO • I2O7 • 12 MoO8. Phosphomolybdates H2O - P2O5 • 15 Mo03.
Manganomolybdates 5 R2O • Mn2O3 • 16 M0O3." Phosphomolybdates
3 RoO • PoOB • 16 MoCV Phosphotungstates (> R 2 0 • P2O5 • 10 WOa.
Phosphomolybdates 3 R.2O • P2O 5 • 18 MoO 2. Phospho tun states 6 R a O
T2Ob • 18 WO,. Arsenomolybdatos 6 R2O • As2O"5 • 18 MoO3. Phosphoiaolybdates 7 R2O • P2O5 • 20 Mo03. Phoephotungstatce 6 R2O •
P2O5 • 20 WO2. Arsenomolybdates 3 R2O • As,O6 • 20 MoO3. Phosphomolybdates 7 R2O • P2O""5 • 22 WO3. Phosphomolybdates G K2O •
P2O6 • 24 HoO3. Phosphotungstates 3 B2O • P2Ofi • 24 WO3.

XI. The Constitution of Clays
. 102
The theoretically possible aluminosilicic acids. Hydrates and Anhydrides. Isomeric aluminosilicic acids. Water of crystallisation and
of constitution. The minerals of the Allophane group as examples of
hydro-aluminosilicates. The water of crystallisation and of constitution in the minerals of the Allophane group. The maximum of water
of constitution in minerals of the Allophane group. Formulation of a
series of analyses of washed clays. The acid character of the clays shown
"by their chemical properties. The unitary nature of clays according to
C. Mene. The behaviour of clays towards concentrated sulphuric acid.
" Clay substance." The constitution, of clays according to ForchhammeT. Tho value of " rational analyses " according to Mellor and
Holdcroft, Seger, Brongniart, and Malaguti. Definition of "disdynaxnised " and " dynamised " substances. Vitri6cation of clays. Seoondary valencies of oxygen in clays. Effect of heat on clay, according to
Hieke, and Mellor and Holdcroft. Polymerisation of Alumina. The
chemical changes occurring in the burning of clays. Isornerism and
JPolymerisni of Kaolin. The H.P. theory and the Facts. Pukall's researches on 2£aolin. The hohaviour of Pukall's sodium *~kaolin.ates towards carbonic acid and towards hydrochloric acid. Mellor and Holdcroft's researches on Kaolin. The melting point of clays and other
jalurninosilicates. Helation between Melting Point and Composition
of Clays. Mineralisers. Plasticity. A new theory of plasticity. Th©
Colour of Bricks.
XII. TTltiamarines
. . .
Historical Review. A new theory of the ultramarines. Two kinds of
hydroxyls in hydro-aluminosilieates of the type H 12 H 4 (Si • Al •
Al' Si), viz. a and ^-hydroxyls. The roplaceability of hydrogen fa the
c-hydroxyls by acid residues. The curious property of the compounds
!Na8 M4 (&i • Al • Al • Si) discovered by Silber^ The ultramarines as
A- and 2-aluminosilic6,tes. The r61o of tlie group 8207 in ultramarines. Sulphonatee. The Sulphonates as Chrom@phor©«. The
changes in the intensity of colour (Soliiltz). The relationship between,
colour and constitution (E. Kietzki and others). The Hexiter-Pentite
Theory of Ultramarines and the facts. Theoretically possibly ultramarines. New formulte calculated from analyses of ultramarines.
Aluminosilicates from which ultramarine cannot be mad©. Ultramarines of different colours, and their constitutions, ^somerio ultraxnarines. The behaviour of ultraDaarinee towards salt solutions. Tjfte»
behaviour of uJtramarines at high temperatures. The Sxilphonate groups

and the colour of ultramarines. The behaviour of ultramarine towards
acids!* The maximum contents of base in ultramarines. The minimum
molecular weight of -ultramarine compounds. The minimum molecular
weight of "Ultramarine blue," according to G-uckelberger. The ultramarines as definite, single chemical compounds. Analogy between
ultramarines and sodalites.
XIII. A ITew Theory of Hydraulic Binding Materials and particularly
©f Portland Cements .
and Historical review of existing theories. Vieat's theory.
Fucks theory. Winkler's theory. Feichtinger's theory. The hypotheses respecting free lime in Portland Cement. The influence of
Fuchs' theory on Heldt, on Chatoney and Rivot, and on the investigations made in order to ascertain the constitution of the Portland cements.
The theories of Le Chatelier, Newherry Bros., Kosmann, Jex, Erdmenger, Hardt, Sch6naieh-Carolath, Schott, 2sigmondy, MeyerMahlstatt, and Rohland. The microscopical examination of clinker.
Portland cements as definite, single chemical compounds. The chemical
constitution of Portland cements. The role of the s-hydroxyls in the
compound H20 (§i • Al • Al • Si) in the synthesis of Portland cements.
Hydro- and anhydro-basic side-chains. The course of reaction in the
formation of Portland cements and the influence of the time and temperature of the burning. Sintered and fused cements. The changes
which take place during the granulation of slags and the production of
slag-cements. Lunge's research on granulated and non-granulated
Blags. Allen and Shepherd's criticisms. The constitution of slags. A
theory of hardening. The new theory and the facts. The r61e of
soluble " silica in the hardening of cements. The causes of hardening
of Portland cements. Zulkowski's theory of hardening. The consequences of the. new theory of Portland cements and the facts. Isrew
formulae calculated from analyses of Portland cements. Stoichiornetric
representation, of the absorption of water by cement. Regular increase
of water-content on Jiydration of cements. The results of Peichtinger's
researches on certain hydraulites: silicate-water, calcium hydroxide
water, and water of crystallisation. Feichtinger's researches as evidence
for the non-existence of free lime in Portland cements. The possibility
of regenerating certain hardened cements and Feichtinger's researches
thereon. Hydration and evolution of heat. Ostwald's thenno-chemicai
investigations on cements. The transition of primary types into
secondary ones in Portland cements and Feichtinger's researches thereon.
The separation of lime in. hydraulites in accordance with certain stoichiometrical laws. The hardening power of hydraulites after removal of
definite proportions of the lime. The maximum contents of silicatewater and calcium hydroxide water. The second setting of previously
hardened masses which have been re-ground. The cause of " soluble
silica " in hydjcaulites. The behaviour of hydraulites towards strong
acids, The possibility of isomerism in cements. Prognoses of the proportion of chalk and clay in the raw mixture. A new solution of the
Sea water problem. The value of cements which contain no a-hydroxyls,
especially lor maritime work. Prognoses of ultramarine cements.
Theory of the Porcelain Cements as used for Dental
The.first porcelain cement (Fletcher's). The use of porcelain cements
in aeptisinr (HorgeustdTa). The chemical composition of porcelain
cements. The properties of an ideal dental stopping (Miller). The
yajuft of 4 scieniafically-foiLnded theory of porcelain cements for the production of_ demtal stoppings. Laboratory tests on porcelain cements.
The mperiDri% of porcelain cements, over rvory and natural dental
enamel so ,iax as resistance to acids is concerned, and the use of this in
solving t3ia^^gl€GPQs of, the course of reaction in the hardening of such
cements. .Wfflfol xtmew of the various theories of hardening of porcelain o«m«im.. The chief cause of failure of porcelain cements, according



to Jung and Morgenstern. Kulka's, Rawitzer and Apfelstadfc's theories
of hardening. Are porcelain cements single, definite chemical compounds ? The composition of porcelain cements as shown "by Patent
Specifications. A physio-chemical theory of the hardening of porcelain
cements. The chemical constitution of porcelain cements. The r61e of
the a-hydrogen in hydro-alurninosilicates in the synthesis of porcelain
cements. The difference between Portland and porcelain cements.
The acido- and baso-philism of alurninosilicates. The acidophilism of
the a- and 5-hydrogen. The different binding power offluorinein topazes.
The acido- and baso-philism of the artificial zeolites studied by Gans.
The arnphochromatophilism of Kaolin (Hundeshagen). The acido- and
basophilism of kaolin in the production of colour lakes. The acidoand baso-philism of kaolin as deduced from the constitution of the ultramarines. The physico-chemical reactions during the hardening of
porcelain cements. The A- and 2-porcelain cements. The course of
hydration. The course of condensation. The constitution of the
hardened A- and 2-cernents. The lamellar hardening of dental cements.
The consequences of the theory and the facts. Calculation of formulae
from analyses of porcelain cements. The absorption of water during
hardening must be in stoichiometric proportions. Prognoses of silicate,
basic and crystallisation -water in porcelain cements. The progressive
hydration of porcelain cements. Factors which affect the time of
hardening of porcelain cements. The high resistance of porcelain
cements to acids explained by the new theory of hardening. The toxic
action of A-cements on the dental nerve-substance (pulpa). The nonseparation of base from A-cemente by the cement acid. Two kinds of
zinc phosphate cements: A- and 2-zinc phosphate cements. Miller's and
Black's physiologico-chemical experiences with A- and 2-zinc phosphate
cements and the consequence deducible therefrom. The hardened Acements as '* slumbering volcanoes." Cause of neurotropy found in
alumino-phosphoric acids and Ehrlich's theory. Definition of neurotropy. The facts in favour of Ehrlich's theory of the* chemical nature
of toxines. The chemical relationship between nerve-fibres and aluminophosphoric acids. Mordanting animal fibres. Siem's and Dftllken's
researches on aluminous poisons. Does the acid reaction of an aqueous
solution of a metallic salt imply hydrolysis, i.e. the presence of a free
acid ? The proof of non-hydrolysis of a series of solutions with metallic
salts with an acid reaction by means of conductivity determinations
and spectrum analysis. Practical experiences of the physiologico-chemical action of A-cements. Kesearches made with a view to reducing the
poisonous nature of A-porcelain cements by empirical rules and the
value of such rules. Pawels' direct proof of the poisonous action of
strong acids on the pulpa by means of experiments on animals. Technical demand for improvements in A-cements. Dental decay as the
cause of diseases of other organs. The proper method of reducing the
poisonous action of the porcelain cemonts oontaining strong acids.
Practical physiologico-ehernical experience of 2-cements.

XV. A New Theory of Glass, G-lazes, and Porcelain
. 236
The chemical constitution of glasses. Isorncrism in glasses. Explanation
of cause of variable depression of the zero point in thermometers naa.de
of certain glasses. 7-comploxes as glasses and their useful properties.
The behaviour of glasses towards water and acids. Devitrification.
Tho chemical constitution, of coloured glasses- Witt's theory. The
H.P. theory and the facts. Calculation of formulae from a series of
analyses of glasses, glazes, and porcelains.
XVI. The Hexite-Pentite Theory as a General Theory of Chemical
Compounds .
. . .
A. The H.P. Theory and the Composition of the Metal-ammonias and
allied Chemical Compounds
. 256
The disadvantages of existing structural formulas of the metal-ammonias,
cyanides, etc., according to Kohlschiltter. Werner's theory of molecular



B. The H.P. Theory and " Water of Crystallisation "
. 25&
The valency of oxygen. The molecular weight of water. Water-hexite
and pentitiB. Hydro-ahimmosilicates. Hydro-ferrosulphates.'. The
wateT of crystallisationinalums. The water of crystallisation in chromosulphuric acids.
C. The H.P. Theory and the Dissociation Hypothesis of Arrhenius , 266
D. The H.P. Theory and the Constitution of Simple Acids
. 268
Salts ofjfthejacids H 2 • H4(PO3)0, H • H4(PO8)6, and Ul2- H4(PO8)ie. 8
Salts of the general formula 2 R"O • 3Na2O • & P2O5 • aq. Hexite formation of niobic and tautalic acid. Hexite and Pentite formation of
tungstic acid. Hexite and Pentite formation of the oxygea free acids.
E. The H.P. Theory and the Carbon Compounds .
. 271
Carbon and Silicon Hexites and. Pentites devoid of oxygon. Chromium
F. The H.P. Theory and the Constitution of the Chemical Atoms:
The Archid Hypothesis
. . .
The consequences of the Archid Hypothesis and the Facts.
(a) The Valencies of the chemical atoms. Atoms with constant and
variable valencies. The *<#alency of nitrogen. The valency of
carbon. The minor valencies of c&rbon.
{b) Homologous series of atoms.

(c) The cause of radio-activity and the work of the alchemists.

The Conversion of tlie H.P. Theory into a Stereo-clemical Theory and
the Comtinartion of the latter with the Modern Theory of the Structure
of Crystals .
(a) Critical Review of Existing Stereo-chemical Theories .
The Hypotheses of van't Hoff and Le Bel. The stereo-chemical theories
of Wernftrfand Hantzsch, Schrauf, Fock, Croth, Hunt, Txitton., Herz,
Doelter and Vufinik, Vogt, van't Hoff, and Becke.
(6) The Modern Theory of the Structure of Crystals and the Possibility of Combinations of the same -with Structural Chemical
Theories .
. . .
(o) Stereo-hexates and pentites, or a Stereo-chemical Theory
. . .
(e) Combination of tke Stereo-Hexite^Pentite Theory with Modern
Theory of Structure of Crystals
(f) The Stereo-Heiite-Pentite, Theory and t i e Pacts



A. Dimorphism and Polymorphism and Hauy's Law
. 2 SO
The cause of dimorphism in compounds with the empirical formula FeS 2.
Difioussioa between Berthollet and Baiiy. Jtitscherlich on Hauy's law.
Qeuther'fl representation of the dimorphism of CaC03. Lelimarin on
Hauy's law.
B. Isomorpliifiin in the Light of the S,H.P. TJieoty
"The geometric constants of isomorplous compounds. The isomorphism
of minerals of tie Felspar group and Tscherma-k's theory. Schiister's
optical examination of plagioclas©. The structure of albite and aaorthito

according to Clarke and Groth. Isomorphism and the theories of Jannasch
and Clarke. The structure of felspars in the light of the H.P. theory.
The cause of isomorphism in various groups of silicates according to
Betgers. The influence of Tschermak's felspar theory on the structural
representation of chemical compounds. Fock's mixed crystals of the
ammonium salt (NH4)2O • S2O5 • 1JH2O with salts of the general formula
WO * SaO5 • h H 2 0. Rammelsherg's protest against the general application of Tschermak's felspar theory.. The theories of isomorphous mixtures
and the facts opposed to it. Betgers' attempt to produce mixed crystals
from the salts fcH2PO4 and (NH4)H2PO4. Tainmann's researches on
hexa- penta- and the 16-phosphoric acids. Isomorphism of minerals of
the epidote group. Schultze's research on. the production of mixed crystals
from PbMx>04 and PbCrO4. Berthollet's views and the theory of isomoTphous mixtures. The discussion between Proust and Beithollet and the
result of modern work.


C. The Dependence of the Geometric Constants on the Side-chains . 305
The influence of the water of crystallisation in the form of crystals. The
crystalline forms of uxano-acetate according to Rammelsberg and to the
S.H.P. Theory. Muthmann and Beoke's topical parameter and the distance of molecules from eafch other in- a crystal. The influence of the sidechains on the crystalline form of benzene derivatives, according to Groth.
The Structural Formula of Benzene according to the S.H.P. Theory . 309
The unequal values of the six hydrogen atoms in benzene. Ladenburg's
vie-ws on the disadvantages of Kekule's formula for benzene. Claus'
formula for benzene. Armstrong's and von Baeyer's centric formula for
benzene. The stability of benzene* and hydrated benzenes in the light of
the H.P. theory. The relationship "between the compounds of the aromatic
and aliphatic series.
D. The Opttea.1 Properties of Crystals and the S.H.P. Theory
The relationship "between crystalline forms and physical properties.
Enantiornorphic crystals. Abnormal optical behaviour of the alums. The
cause of circular polarisation in some crystals according to Groth. The
production of circular polarisation by means of sheets of mica (Eeusch).
The dependence of ciroular polarisation on chemical constitution. The
circular polarisation of organic compounds with asymmetric carbon atoms
according to van't Hofl! and He Bel. The optical "behaviour of pure and
mixed alums according to Braans. Sohneke's explanation of the cause of
circular polarisation. The cause of circular polarisation in the light of the
S.H.P. Theory.
E. The Dependence of the Geometrical Constants on the Temperature 316
Formation of calcite from aragonite, according to* Hose and Klein. The
change in crystalline form on increase of temperature, according to* Lehm&nn.
F. Molecular Volumes and the S.H.P. Theory



. 317

Summary and Conclusions
. . .
The H.P. Theory ajid its critics. The value of the H.P. Theory. The
value of the S.H.P. Theory. The aim of Science.
Bibliography of references mentioned in text






. . .
Formulas and Analyses
. ui
Formulae calculated from Lemherg's experiments. Calculation of TommIse of the Topazes. Calculation of Formulae of the Epidotes. Calculation of



Formulae of the Granites. Calculation of Formulae of the JMesolites. Calculation of Formulae of the Clintonites. Calculation of Formulae of the
Micas. Calculation of Formulae of the Scapolites. Calculation of Formulae of the Orthochlorites. Calculation of Formulae of the Tourmalines.
Calculation of Formulas of the Felspars. Calculation of Formulae of Clays.
Behaviour of a Series of Dried Clays towards Sulphuric acid (Bischof).
Calculation of Formulas from, analyses of Ultramarines. Calculation of
Formulae from analyses of Portland cements.
Bibliography of references in Appendix
. . .



N the year 1903, the f a c u l t y of Philosophy in the University of
Gottingen proposed the following thesis in connection with t h e
Benek Bequest :
A critical examination, based on experimental evidence, is to be made
of such chemical compounds as cannot be satisfactorily explained by the
usual means. This examination should also take into special consideration the extent to which the introduction of molecular additions is of
importance in the formation of such compounds, and whether it is possible
to devise a complete systematic arrangement of such compounds.
Under the m o t t o :
"HOPTCL (Oeo?) fierpio KQU aptdjuia) KOL (rra^/utx) SUrafe"
t h e authors submitted a thesis which forms part of the present volume,
"viz. p p . 1 to 102 and t h e Appendix.
The solution of the problem was
admittedly incomplete, inasmuch as only a single branch of t h e subject
— t h e silicates—"was taken into consideration. For this reason the
^Faculty did n o t grant t h e first prize t o this thesis, but readily granted
t h e second prize " in recognition of fruitful labours leading to a single
theory covering a very important group of complex compounds.''
I n this w a y a n established theory—the Hexite-Pentite Theory—
was devised for one highly important group of complex compounds—
t h e silicates.
With this theory in mind, it was only natural to apply it t o a series
of silicates of technical and commercial value, such as the ultramarines,
P o r t l a n d , slag, dental a n d other siliceous cements, glass, glazes, porcelain, etc., in order, if possible, to elucidate their constitution. This
h a s been effected since t h e original thesis was first written, and t h e
results a r e published i n the following pages.
Commencing with the assumption t h a t Nature has formed all substances in accordance with monistic laws, t h e Hexite-Pentite Theory
h a s also been applied to the study of the structure of other complexes
as well as t o t h a t of solutions of t h e simpler acids, etc., and it has also
been employed, in connection with the constitution of organic compounds, t o form a bridge between organic and inorganic chemistry.



I n ordex to take into consideration the positions which atoms occupy
in space (a factor which is omitted from most theories of chemical
structure) the Hexite-Pentite Theory has also been developed, in
combination with the modern theory of the structure of crystals, into
a stereo-chemical theory.
The German edition of this work was published late in 1911, but for
some unexplained reason almost every reviewer of that edition failed
to appreciate the advantages which may be derived from this theory,
and with a few exceptions they have overlooked the fact t h a t the
Hexite-Pentite Theory—as distinct from, older ones—is concerned
especially "with inorganic chemistry, and that it has the following
characteristics :
The Hexite-Pentite Theory is a general and unitary theory ; it is
based on a single truth—Le. on a natural law found by inductive
reasoning ; it leads par excellence to prognoses, and therefore permits
of deductive reasoning—the combination being a clear sign of a true
theory—and it is, in addition, based on the methods of the most
famous classical chemists. Moreover, it comprehends the best of the
existing theories or explains their deficiencies, and is, above all, a
definitely stereo-chemical theory.
To enter into a complete reply to the various critics would occupy
too much space in the present volume, and as the publication of t h e
present edition has occupied more than a year on account of the
additional matter required—much of which is due to the kind suggestions of the translator—the authors have decided to publish t h e
greater p a r t of their reply t o critics in a separate volume to be issued
shortly under the title " The Structure of Matter." At the same time it
will be noted that the chief criticisms have been met in the present
edition, though the following are conveniently noted in the Preface
rather t h a n in the text.
A number of critics adopt the remaik&ble view that the comprehensiveness and unitary nature of t h e Hexite-Pentite Theory are a
disadvantage ! This is specially t h e case with C. H . Desch 736 ,
Allen and Shepherd 7 3 7 , C. Doelter ( " H a n d b . d . Mineralchemie''). Yet
comprehensiveness and unitary nature are essential characteristics of
any general theory. No less an authority than Beithollet has declared
t h a t the advantage of a general over a special theory is that the former
has certain characteristics, which are precisely the ones possessed by
t h e Hexite-Pentite Theory. InGmellm-Kraut's "Handbuch " and other
classical text-books it is admitted t h a t the object of investigation is
to produce a complete theory of chemistry from Tvhich all natural laws
affecting chemical reactions can be predicted or explained. I n short,



t h e comprehensiveness of the Hexite-Pentite Theory is a positive
advantage a n d a n indication of its t r u t h .
The earliest opponents t o a unitary nature or monism in chemistry
were the French investigators Laurent and Gerhardt. Mendelejeff and
Ms associates, on the contrary, are in favour of a monistic theory.
Blomstrand, Ostwald, Nernst, Markownikoff and many other wellknown chemists h a v e often pointed out the fallacy of the conception
of t h e existence of molecular compounds, and these scientists are
therefore in favour of a unitary view. One of the reasons why a portion
of t h e present w o r t was granted a prize "by the Faculty of the University of Gottingen was t h a t in it the investigation leads to a unitary
conception of t h e silicates.
One of the most valuable features of the Hexite-Pentite Theory is
t h a t it effectively disposes of the necessity for a n y dualistic conception
of m a t t e r .
The classification of matter into chemical compounds and the socalled isomoryhous mixtures or solid solutions, as is so commonly done
a t t h e present time, leads to t h e conclusion t h a t there are some exceptions t o n a t u r a l laws. Yet when an exception is found to a natural
law this is only a n indication t h a t the terms in which the law is expressed must be altered so t h a t it may include the apparent exception.
W h e r e this cannot "be done the " law " must be regarded as imperfectly
understood. As Spinoza has remarked, " N o sane man will believe
t h a t N a t u r e is limited in her powers a n d t h a t natural laws are of limited
a n d n o t of general application." The correctness of Spinoza's teaching
is clearly shown b y t h e small results which have been obtained from
t h e application of t h e dualistic or pluralistic theory of matter, i.e. by
regarding certain complex compounds as mixtures. Thus, W. J .
MiUler and J*. ELonigsherger 779 , in studying the work of Day a n d his
associates in Washington a n d of Doelter in Yienna, point out that
notwithstanding t h e skill and expense involved, " the results of these
investigations do n o t appear to be commensurate with t h e labour
involved.'* Miiller a n d Konigsberger attribute this to the absence of
analogy "between t h e materials investigated and those used in other
branches of chemistry, "but the Hexite-Pentite Theory shows t h a t there
is an abundance of analogies, and t h a t t h e t r u e reason for the paucity
of results of theoretical value from the Washington and Vienna Instit u t e s is to be found in the erroneous pluralistic view of matter which
is held b y those in charge.
The constitution of Portland cement has been the subject of investigation for nearly a century, without any definitely satisfactory result.
This is due to precisely the same cause—the persistent maintenance



of a pluratisticj>r paixture theory and the neglect or repression of all
information or suggestions to the contrary. The attitude of many
supporters of the mixture theories of Portland cements is far from
scientific, and notwithstanding the abundance of proof of a chemical
nature in favour of the Hexite-Pentite Theory, those in favour of a
pluralistic conception of chemical substances still pin their faith to the
very slender microscopical evidence on which their theories are based.
One extraordinary " r e s u l t " of following out the mixture theory in
the case of Portland cement is in the experience of two French engineers
—Ohatony and Rivot (see p. 156 in the text)—at "whose instance
extensive maritime works were constructed. The panic amongst
French a n d other constructional engineers which resulted from the
destruction of these structures can "better be imagined than described !
The pluralistic conception of chemical substances has also been t h e
cause of a number of serious accidents and bad results in medical
chemistry. Thus, in the opinion of the authors, the pathology of many
diseases such as diabetes, cancer, tuberculosis, etc., must remain very
incomplete, and the nature and causes of these complaints must be
completely misunderstood, so long as the pluralistic conception of
matter is maintained. An interesting example of this is found in the
toxic action of certain dental stoppings which are fully described ia
the following pages. ^So firmly has the mixture theory been held that
t h e opposition to these toxic cements was almost devoid of results, and
this theory still exerts a considerable amount of influence, notwithstanding the fact that the authors have not merely shown the causes
of the toxic action, "but th§ way to prevent it, and have placed perfectly
satisfactory and non-poisonous dental cements, made in accordance
with the Hexite-Pentite Theory, on the market. The continued
maintenance cf the pluralistic conception of matter in medicine
is, therefore, even moTe dangerous than it is in industry.
Among the various critics, it is pleasing to turn from those who have
reviewed the first edition of this book in a careless or partial manner
to greater scientists like Wilhelin Ostwald 780 , who states, " The
authors commenced with an explanation of the constitution of the
clays and allied substances, b u t passed on from one branch of chemistry
to another until they have eventually been able to illuminate an
astonishingly large number of different facts, all of which are regarded
from the same point of view. 5 ' That so able a chemist as Ostwald should
describe t h e present work in such glowing terms is particularly gratifying to the authors, more especially as Ostwald h a d the opportunity, as
a student of Lemberg's, of knowing the remarkable plains which
Lemberg took in t h e prosecution of his investigations—studies which



x % r o [ p r o v e d invalu&ble as a source of experimental evidence with
* l o t * , t^hie Hexite-Pentite Theoxy is in complete agreement. Ostwald
«-£n g o ^ s so far as to state t h a t " as a n observer for many years of the
i f r j > c i i x c " t i o n and development of m a n y scientific theories and works I
**i i r x o t a-Yoid declaring the present one as m o s t unusual. Let us give
* *4 e a r t y welcome to these young a n d energetic investigators and assure
i :rr
* * " t l a s i t the further results of their work will be watched with t h e
interest.' 7
"fcliis connection it is interesting t o recall the regret which Landolt
t h a t his friend Kefcule* did not live long enough to see this
»*«"\%r t o c l i x i m p h of his Benzene Theory, for t h e Hexite-Pentite Theory
f n u j j r fc>e -very definitely regarded as an extension and development of
* **«• 3 Q « 3 a l t o n - K e k u l e teaching. I n a letter, Landolt also expressed his
* *•*f 1 1 * i t : e o p i n i o n that, sooner or later, the Hexite-Pentite Theory must
*** * "fti^kiexx up b y chemists in every branch of the subject. The remark*"* I *lmj r o s i a l t s which followed the synthesis of various scents, anaesthetics,
* I v i s H , e t c .-—all of which are primarily due to the Kekul6 Theory—are
^ * ***.*ra|g; e v i d e n c e in favour of the Hexite-Pentite Theory, for Kekul6's
* i*f**j>r*;y- i s essentially a part of the Hexite-Pentite Theory.
K f a t r l i o h ' s Side-chain Theory is, in a similar manner, another p a r t
* *i f l i e H e x i t e - P e n t i t e Theory, a n d t h e enormous value of Ehrlich's* I * C ! e > i r y £ x x physiological chemistry is already recognised by specialists*
* t* t h L » s i x t j e c t .
11* i s a^lso interesting to observe t h a t the facts which have led to the
* # * i t c l fecsrg-Waage Theory are also direct consequences of the Hexite1 *««r*tl'fc*e T h e o r y .
JtS\r«*r » t f i tJho
Hexite-Pentite Theory.
s u b j e c t of colloids, "which is attracting a large amount of
*» t t c r a r m t r i o i x a»t the present time, is exceptionally well illuminated b y the
t f n ^ ^ i t ^ e r - O P ^ n t i t e J h e o r y , and the authors had intended to include a
* *# mmith^TT&tTbls
amount of information on this sufcject in the preseat work.
i r f i t * a ^ t i o . o i a . a t of space occupied would "be so great as to make the present
%-«*l«jixi3L%m m m ^ u i t o l i o a t i o n t h a t this subject m u s t "be dealt with in a subsequent
The reader's attention is, however, called t o t h e subjects of
a r n d coloured glasses—discussed somewhat fully in the present
hitherto the constitution of these has usually l e e n exixiL terms of colloids. Such a a explanation is highly indiyidual%%
cannot be applied to cements Or glasses as a whole, so t h a t
* €*m^t%T%ot> be regarded a*s a. really scientific hypothesis. By means of
I f 4#5 J H E e x i t ^ - P e n t i t e Theory, on t h e contrary, the cause of the colour of



certain glasses is explained in a manner precisely analogous to t h a t in
certain coloured organic compounds, wherein the colour is known t o
be due to the arrangement of the atoms.
In preparing this English edition, t h e authors have had the inestimable advantage of the assistance of a well-known authority on clays
and other silicates, and they hereby wish t o express their indebtedness
to him, not only for the manner in which he has executed the translation, but also for his kindness in making numerous and valuable
suggestions and criticisms and for the various additions (printed in
smaller type for their better distinction) due to his special knowledge
of the subject.
July, 1913.











The Chemistry of Carbon a n d Silicon
f T l H E remark has frequently been made t h a t , "whilst the study of
X carbon compounds has reached a high state of development,
comparatively little attention has been paid t o t h a t of other elements.
A large number of chemists are engaged in studying the chemistry of
carbon because the methods of investigation have been worked out
more thoroughly t h a n those for other e l e m e n t s ; because t h e interpretation of t i e results is clearer, and because many carbon compounds, such as the organic dyestufls a n d more recently t h e artificial
scents, l a v e proved t o be of enormous technical value.
The majority of chemical theories p u t forward in recent years are
based on the characteristics of carbon compounds and are modified,
abandoned, or again become generally recognised, "without the chemistry of other elements having any appreciable influence upon them.
There can b e little douht t h a t if the study of other elements had
reached as high a state of development as t h a t of carbon, not a few
facts would have "been discovered which would lead to other constitutional formula a n d to fresh hypotheses a n d theories; it is, indeed,
probable t h a t a t least as many new laws would "be formulated as have
resulted from t i e widespread investigation of t h e chemistry of carton.
These additional laws a n d generalisations should be of even greater
value, inasmuch as they would b e "based upon a wider knowledge.
Many industries should derive considerable benefit from the results
of a, more thorough study of inorganic chemistry, and newproducts—
or even new industries—"would probably result. The carMde industry
and tha,t of t h e rare earths owe their existence to an increased study
of this branch of chemistry. Other industries such as those concerned
in the production of artificial gems, inorg&nfc colours, t i e manufacture or employment of cement, clay, tdtramarine, glass, etc. are
capable of extensive development through the application of scientific
investigation to t h e materials used in them.
Whilst carbon has a special interest on account of its being the



essential constituent of all organic substances, its analogue, silicon,
should be no less interesting as it forms the chief material i n the earth's
crust. I t probably plays a fax mofeTimportant p a r t in t h e n a t u r a l
processes of the inorganic world than carbon does in t h e realm of
organic substances. A moment's thought will show the immense
variety of chemical reactions and the enormous scale on which t h e y
occur in the upper layers of our planet. The form of t h e e a r t h ' s
surface, the character of the mountain ranges, volcanic eruptions and
the phenomena of solution and decomposition are all related to such
characteristics of the widely distributed aluminosilicates as their
hardness, fusibility, heat-conductivity, resistance t o pressure, etc.
These characteristics are closely related to the composition and the
chemical nature of the elements concerned, particularly silicon. How
great an interest a knowledge of the structure of these compounds
possesses, is shown by the manner in which mineralogists a n d chemists
study the crystallographic, physical a n d chemical properties of rocks
and by the great variety of theories which have been formulated in
order to give some idea of the constitution of these remarkable compounds.
In spite of great intellectual effort and innumerable experiments—
only a small proportion of which have been published—which have
been made t o draw this subject from its obscurity, little progress has
been made, and the silicon compounds, in spite of t h e fact t h a t t h e y
occur in enormous quantities and are most widely distributed, m u s t
be included amongst those substances of whose constitution very
little is known.
For this reason it is thought t h a t a fresh a t t e m p t to illuminate
this subject by investigating it in a purely experimental manner, a s
distinct from the more theoretical considerations of other scientists,
may not be without value.


Section I
Historical Survey of the various Theories regarding the Constitution
of the Aluminosilicates and other Silicon Compounds


HE scientific study of the constitution of the silicates commenced
in the first decade of the nineteenth century when Berzelius 1 *
Smithson 2 and Dobereiner3 simultaneously (1811) regarded the
silicates as salts of silicic acid or silica. Previous to this, the role played
by silica was, in spite of the researches by Bergemann, Klaproth,
etc., far from clearly understood. The silicates were regarded as
complex mixtures of various oxides and as peculiar substances quite
distinct from other salts. Very few suggestions as to their true character
can be found in the earlier literature; they remained outside the general
development of scientific knowledge, as Tachenius—who regarded the
silicates as salts of silicic acid—endeavoured to show in the seventeenth
century. 4
Although the suggestion that the silicates are salts of silicic acid or
silica was made simultaneously and independently by Berzelius,
Smithson and Dobereiner, as already mentioned, the chief credit
must be given to Berzelius; Smithson contented himself with stating
that minerals do not differ from artificially prepared compounds,
and that the composition of the silicates can only be understood by
regarding them as salts, and quartz as an acid.
Dobereiner5 worked on purely speculative lines, and argued that
as silica forms salts with bases, the oxide of silicon, SiO 2 , should be
termed " silicic acid." f
Berzelius expressed himself much less decidedly, though his meaning
was equally clear.6 He stated that when two oxides combined, one
must be regarded as electro-negative, and suggested that the nomenclature of such oxides could be distinguished from that of the salts.
Several years later he classified silica compounds into bi-silicatee, trisilicates, etc. according to the proportion of oxygen in the silica and
the base, and made some very clear suggestions regarding the formation
* References to authorities axe given in the Bibliography at the end of this volume.
t The term suggested by P&bereiner, viz. " Kiesels&ure," is that used in
Germany at the present day, there being no exact equivalent in German to the English
word " silica." The word " Kieselsaure " thus represents both " silica " and " silicic
acid," the latter term expressing its meaning exactly, though seldom used exopet where
the acid nattixe of the substance is specially under consideration.—A. B. S.



of the complicated salts of silica. At that time he was so convinced of
the acid nature of silica that he believed that no mineralogist
acquainted with the chemistry of the period could have the slightest
doubt that silica was a true acid. He maintained—as SmithStm h a d
done before him—that double salts existed in silicates containing
A12OS and Fe*O 3 , and pointed out the analogous nature of the alums
in which silica is replaced by sulphuric acid. He also regarded t h e
spinels as salts in which A12O3 plays the part of an acid. These suggestions were at once accepted by scientists.
By great industry, Berzelius largely extended our knowledge
of silicates. The discovery of isomorphism by Mitscherlich a n d t h e
investigations of Bonsdorff and Rose—two pupils of Berzelius—confirmed their master's theories and made it possible to provide simple
formulae for a number of silicates.
Through the use of a formula—which for silica was written as
SiO8, SiO 2 , or SiO—a great simplification occurred, though for t h e
silicates as a whole the expression of the results of chemical analyses
by formula did not fulfil expectations. 7
In 1846 Laurent 8 suggested that the silicates are not salts of a
single, but of several silicates. He had proved the existence of several
tungstic acids and presumed the existence of several silicic acids of
different chemical compositions analogous to ortho- and meta-phosphoric acid. This hypothesis was accepted by scientists as soon as t h e
value of the " Type theory " had become generally recognised. Between 1855 and 1865 it was in great favour, and it is still held by some
chemists. About the time mentioned, Fremy's work on tin-acids was
published, and from this arose the idea of poly-silicic acids a n d anhydrides, which was readily adopted. This hypothesis has been published at various times and from various points of view b y Fremy 9 , St.
Hunt 10 , and Wurtz 11 , its clearest and most accurate form being due
to Wurtz. Various modifications of it have been used in theoretical
investigations by several scientific writers with greater or less effect,
and there is in existence a long series of treatises, each more or less
independent of the others, forming complex combinations of old and
new work, by Woltzien 12 , GolowMnski13, Odling 14 , Streng 1 5 , Lawrow 1 6 ,
Schiff17, Bodecker18, Stadeler 19 , and others. The chief result of all
these researches is to indicate that the theories put forward do not
de facto suffice to render the constitution of the silicates clear. So
far as they are concerned, the problem remains unsolved in spite of
the large amount of work done in connection with it.
A great advance was made by Damours 20 , who was the first to
suggest that the water in many silicates is of the nature of " water of
constitution/' i.e. it is an integral ingredient of the salt (silieate)
itself. The importance of this observation was pointed out b y Laurent 2 1 , Bodecker 22 , and Rammelsberg 23 , and its application has greatly
increased the significance of the formulae of many silicates. More
recently, Clarke 24 has endeavoured to explain the behaviour of a



series of hydrous aluminosilicates—the zeolites—at high temperatures
by m e a n s of structural formulae.
M a n y silicate formulae have been further simplified b y the employment of microscopical analysis. 25
T h e r e still remained, however, a very large number of silicates
whose constitution cannot be ascertained b y means of t h e numerous
investigations and exact analytical methods previously mentioned.
This state of affairs naturally led to further a t t e m p t s t o ascertain
the constitution of the silicates, and numerous new theories were
formulated. Thus, Wartha 2 6 , Haushofer 27 , and Safafik 28 endeavoured
in 1873-^4 to explain the chemical nature of the silicates b y m e a n s of
s t r u c t u r a l formulae. These attempts, which were based on theories of
the s t r u c t u r e of carbon compounds, did not lead to any definite result
and h a d no appreciable influence on the development of theories
relating t o silicates.
The felspar-theory published by Tschermak 2 9 in t h e " Transactions
of the V i e n n a Academy," in 1865, on the contrary, was of great importance, but was only accepted by scientists after it had been discussed f o r several years.* This theory, which assumes t h a t some of the
felspars are formed by the mixture of two substances—albite and
anorthite—is well supported by a large number of analyses, and was
undoubtedly of great value a t the time it was introduced. I t not
only facilitated the systematisation of a large number of analyses,
but explained t h e relationship between certain physical characters
and t h e chemical composition of several silicates.
I n Tschermak's theory the purely chemical functions of the
silicates are not considered; this is its great weakness, and for this
reason t h i s theory was only accepted by scientists for want of a b e t t e r
interpretation of t h e results of innumerable analyses of felspars. This
difficulty existed until quite recently, for in Mineralogy there a r e a
number of similar theories in which the chemical characteristics of the
compounds concerned are entirely disregarded, as in t h e ordinary
theories of the chemical nature of Scapolite 30 , Mica 3 1 ' 3 2 , Tourmaline 33 , e t c .
T o w a r d s the end of the " 'seventies " very few ideas on the constitution of silicates were promulgated, the work done at t h a t t i m e
being chiefly in the direction of increasing the number of observed
facts a n d improving the c< observation m a t e r i a l " from which conclusions m i g h t be drawn with greater accuracy and safety t h a n hitherto.
Such researches as these made it possible for Vernadsky 3 4 to
publish h i s interesting treatise on " T h e Sillimanite Group and t h e
role of Aluminium in Silicates." A considerable time before Vernadsky,
sevepd. authorities had agreed t h a t aluminium in silicates has t h e
characteristics of an acid; some presuming the existence of complex
• Special attention is directed to Reference"No.29 in the Bibliography at the end
of this volume.



silicoaluminic acids whilst others believed that aluminium in the
aluminosilicates plays the same role as silicon. Bonndorf", AH the risult of investigations on hornblendes containing alumina in wliirii
the proportions of SiO 2 and A12O3 vary, reached the wndiwion that
silicon and aluminium each play the same rule. Sehetwr 1 * roniirmwi
this view of Bonsdorffs. The view that aluminium in th« natural
silicates has an acid character was also held by Berzelitm17, Ifckifrkfr " ,
and Odling30.
Wartha40 was the first to publish this hypothesw in i* rlwir t w i n ,
but he afterwards paid more attention to structural formula n ml rvwtl
to develop this theory. About the same time, Bratinn** attribute*! an
acid character to aluminium in natural silicates, but iiiHtrm! of tlw
ordinary formula, A12O3, he preferred AIO*.
Vernadsky endeavoured to show that aluminium play* th«* mum
role as silicon in the aluminosilicates and that from the liittrr r»mpl<«x
acids (silicoaluminic acids) may be produced. Earlier obwrvattutt*
and experiments on aluminosilicates and the chemical obrnigi^ urmrring in Nature completely confirmed this view. At fir*tf \Vrna*l*ky
sought to base a chemical classification of the alwnimwdliriitr* uti hi*
theory, but this could be applied to only 11 small number of rrmi
pounds. Most of the aluminosilicates, such an febtpar, mira, M e ,
could not be brought within any scheme ho could dewiw, Atifl thotigh
he repeatedly declared that the so-called " mixture tliwrtf* M IIIIVP
little real value from a chemical point of view, hi* hdirved thut it w&#
unwise to abandon them.
Vernadsky's42 structural formulae have consequently dont* littli*
towards solving the problem of the constitution of thi? **iiicn.U?M.
The present theories as to the constitution of ulumtnoKilirnUNi
appear, with the exception of that of Vernadiky t to fees rombituttion*
of older theories. The existence of various ortho*, metn- v nml uiimt
silicic and poly-silicic acids, and of simple and double* *§&]!« of \hm*\ w
generally accepted, and to some extent structural formula? havts bi*t*n
allocated. The theories of Rammelsberg4*, Groth**f Clurki*14, Tmrlwrmak46, and others are of this kind. Those of 8&wtncht«nkcm" And.
more recently, of Goldschmidt4*, differ somewhat, m thi*y am hmml
on the idea that the above-mentioned silicates cannot b& v%phhnmi
by the foregoing theories. The researches of Bombtcri"and Brmutm***
which are based on purely hypothetical considerations, an? <$t*i!a
different from those previously mentioned.
The recognition of the acid nature of clays is rapidly Raining
general acceptance. Kaolin behaves in many way* pn&ferty like an
acid, displacing carbon dioxide in carbonates, chlorino in rhforidt*.
etc., and Mellor and Holdcroft708 consider it to be atatninositfrk mid
(kaolinic acid). These writers, like Vernadsky, claitsify the altsminosihcates according to the ratio of Al a O 8 to 8 i O t and dktingiiinh thmn
as alumino-Tnow-, aluxnino-rft-, aluraino-frf-, alumino-l«lro-f aiumtnopenta- and alumino-Aea;a-siUcates. For instance, they regard n#phdint f



NftjO • AJj(>» • 2 KtO, H« ii salt of An Altmiino»etc. They alno nugget constitutional fnrmuh*< fur the*e Huhnt ancen,
but without contributing timteriAlly to nay underNtamiinK of the
rnxmtitiitinn of tbe Alumifi"»ilicjif«\V. FtikfilF^*'**0 HIHO refer* to tbi« iui*l nutur^ of kaolin wbicb,
when tligf.*4t<»fl on n \vnff?r4*nth f**r H«'Vt*niI tbiyn with a nolution of
rauittic1 .Htidii» ftxrH 11 l**rn** cjunntity «*f thr» f*o*In. !}•• ban alno obwrvcd
that kaolin at n t**m|t**n*t«rrhiorim* from rf»mnit»n **ait anfl libi-rat^H a rottifxiuntl forr^Hponiling
to XA|C> • A!|O S * 2 SiO t . Arming uthvr writer** who bavo rt*n*ntly
rcfcTri'd to th«« arid nattm* of abunina in thf alttmiuoHttirati'H may !w
r»f«ticjit«»fl .f, Morowwiry,'* 1 , t%b*i AI»*O rt*garfU ka


An obwrvAtMni by l>iilknbnrii TtI in highly confirmatory fl^ ^ lf * ** *f"
if aiumifiA in thr1 »luinino.*»ilical«»t«, H in wull known that silica
which IIIIM b«en firr* ij*ifi*f**4 from **ohition ntid iiffi*rwiirtlH well wished
in neutral to lit mil*. l>l>arttf*u)ArIy <• !»%•«, whi«'b nrr no*/ to litrniw nut} obwervee! that, noii h l
4 h }
|l !y
their iKtility, no a*-it I |iii.«uttnK iut.*i tin* t^A^h^wati^r. ff, bowi*vt*r, a neutral Milt- .niii-b /*•* fi*#tn-fw*itMii t-htoritl*% iimifionium Mslphiitu
or Ainmonitim rblorid*11 i« iidrl**4 to t h* rln,y a n*ifutil#* acW m immHltntulypunUm-tlt ftp? pot.a*lii*ri*mmrmiA l*tnngab**f*rbf*iliind hydroettlorin
or Hiiljthtiri*' iM*id lilw-r«ite*I, Thi^ t*» tmfmrtAiit in connect ion with
miother fm^t r«tiibli»«h«''d by llnlknhArA, vm* that finely divided febjiar
—which he rcgnrdU a# A r$mttrattN«itl kiuiltn- on pridfingerl treiifmi^ni
with an iit|*ie«:iii» wiliifinn t4 rntbt»ndtili
which behnv«* in A ttniutier «imifi*r to the rlnyn juiit menttotted.

Section If
Critical Bm^§f

of the tx\nun:

Tbcorien of Alumino*ilicaUii

fllHK U
$ «*< t|u* jfttufmnM*iii«*ii,tr>jf:
The iiiu?niii*»^ih^ ftfr# nrn HAIIM of nilirtin hydmtit fn which thit
i*» (lAttly rrjtlnu *ft| by Altimitiium and tiArtly by other
l l l
f J
mnd othrr met#K u.'i AIMI $jtf»mnr}thoitn fninturei 4 tfitMtt
3. Thff mhmnni
chemical *.mitp«»fifitl* whi^h hmvn nothtfig in rwmmtm m



regards their chemical nature. The mode of combination between
the various components is very labile.
4. The aluminosilicates are isomorphous mixtures of salts of silicic
and aluminic acids.
5. The aluminosilicates are double salts of silicic and aluminic acids,
or amorphous mixtures of these double salts.
6. The aluminosilicates are, in part, silicoaluminic acids and, in
part, the salts of these acids.
Before we criticise these theories in the light of the facts, it appears
desirable t o make the following statement: The aluminosilicates
constitute a single, well-defined class of compounds, the members of
which agree in the numerous observable chemical changes which they
undergo in Nature (the so-called pseudomorphic processes) and in
those of their characteristics which are best studied in the laboratory,
such as their synthesis and their behaviour towards reagents and at
high temperatures. I n these ways the aluminosilicates differ considerably from silicates which are free from aluminium and other
sesquioxides. No reaction is known which makes it necessary to place
any of these compounds in a special class or to give them a special
place in a separate class. They pass into each other or form the same
compounds ; they all change slowly under the influence of geological
processes into one and the same compounds of the kaolin group. In
considering these hypotheses we must take special notice of this
phenomenon ; and in explaining the chemical nature of the compounds under consideration, only those hypotheses or theories should
be employed which make it possible to indicate the composition of
these compounds in a uniform manner and to exclude those silicates
which show important differences of character. That hypothesis or
theory which agrees most closely with the facts and is free from
obvious disadvantages must be regarded as the one which approaches
nearest to the truth.
(a) Critical Examination of the Pirst Hypothesis
According to the first hypothesis the aluminosilicates are silicohydrates in which one part of the hydrogen is replaced by aluminium
and another part by other metals.
This theory contradicts the following facts :
1. The relation between aluminium and the other metals contained
in these compounds remains constant no matter how soon the reaction
of the double decomposition is interrupted.
2. N o reaction is known whereby it is possible to produce a hydrate
of silicic acid from the aluminosilicates and from this hydrate to
reproduce the original substance, i.e. the aluminosilicate. The separation of silica b y means of strong acids is always accompanied by a
complete destruction of the whole compound. The replacement of
the metal b y hydrogen usually occurs in such a manner t h a t only
those metals can be substituted which are capable of forming oxides of

AUK A l . r M I N O S l L l c r A T K S



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