GEOLOGICA CARPATHICA, 53, 2, BRATISLAVA, APRIL 2002
133 — 136
CLAY SCIENCE FROM THE PUBLICATION AND CITATION
KAROL JESENÁK, UBOMÍR KUCHTA and VLADIMÍR HLAVATÝ
Department of Inorganic Chemistry, Faculty of Science, Comenius University,
842 15 Bratislava, Slovak Republic; firstname.lastname@example.org
(Manuscript received October 4, 2001; accepted in revised form December 13, 2001)
Abstract: The publication production of clay minerals is analysed on the basis of the works registered in the SCI
database in 1980—2001. A continuous increase of the annual number of works in this period is registered while the
proportion of the number of works devoted to individual clay minerals remains almost unchanged throughout the whole
period. The subject of publication production is substantially dependent on the type of mineral followed; material re-
search oriented papers, catalysis and organo/clay interactions research prevail among the papers with a chemical charac-
ter. The average citation response to the set of analysed papers is about 10—15 citations/paper and uncited papers repre-
sent 9—35 % of the total number of papers. The most cited papers (in individual years) are cited on average 109-times
annually and half-time of the citations count per paper exceeds 20 years. The average time between appearing and the
greatest citation response can be estimated at 5 years.
Key words: citation analysis, publication production, clay minerals.
Clay minerals research covers, due to its interdisciplinary
character, the scientific fields of geology, pedology, chemistry,
environmental sciences and even astronomy. The use of clay
minerals is wide and includes not only basic research method-
ologies, but also a large spectrum of industrial and technical
applications. Subject diversity of papers and the wide variety
of journals in which the papers are published show the hetero-
geneity of clay research. Though this character of clay re-
search is well known there are no reliable statistical data to
prove this statement. One possible way to tackle this problem
is evaluation of the number of journals where works on clays
appear. Such an attempt was made in 1998 (Jesenák & Kuchta
1998). The results show that chemical works dealing with
clays appear in approximately 800 scientific journals. This fact
can be quite surprising for a major part of the community
working in this scientific field. It is mainly due to the great
popularity of periodicals selecting only a small part of the total
publication production in this field. A detailed description of
the situation in the clay science publication activity was pub-
lished in (Jesenák & Kuchta 1998; Jesenák & Kuchta 1993)
aiming not only at quantification of the known facts about the
character of scientific production, but also at documentation of
long term trends in this field. However, some of the data were
outdated already at the time of appearance of the work (Je-
senák & Kuchta 1998).
The objective of this work is to provide an up-to-date survey
of publication production in clay science. A pronounced dif-
ference between papers mentioned above and the present work
is that the present survey is not limited to the works of chemi-
cal character, but involves all fields of natural sciences.
An electronic database of the SCI periodical, which was
freely available on the Internet (web page of Institute for Sci-
entific Information, Philadelphia, USA) in May 2001, was
used for analysis. Concerning the philosophy of the SCI data-
base architecture, the analysed set comprises quite narrow, but
important groups of works from all scientific fields.
The analysed set included bibliographic data from all works
registered in the SCI in 1980—2001 where the name of any
clay mineral was found as a key word. A program associated
with the SCI database was applied for selection of relevant
data; some MS DOS programs were created by the authors and
applied for special tasks.
Results and discussion
The trend in the number of the papers with the key word
“montmorillonite” in the last 20 years is shown in Fig. 1. A
stabilized situation in 1980—1990 is followed by a period of
continuous growth. Considering the trend in 1930—1997
worked out from the Chemical Abstracts (CA) database (Je-
senák & Kuchta 1998), which shows an almost stabilized situ-
ation since the late 1980s, the increase of registered publica-
tion count in the early 1990s can be explained by a change of
the SCI database processing conception and possibly by some
changes in the organizational system and technical equipment
rather than by a real growth of the published papers. This opin-
ion is supported by the fact that the turning point goes back to
the period of revolutionary changes of technical equipment
and information services. It is assumed that ascendant charac-
134 JESENÁK, KUCHTA and HLAVATÝ
Fig. 1. Number of works (y-axis) with the key word “montmorillo-
nite”, registered in the SCI in 1980—2000.
ter of the curve for the late 1990s is an expression of a real
trend in the development of publication activity. Fig. 1 sug-
gests that the SCI database could hardly be considered a reli-
able basis for literature review in clay science until the end of
1980s. But the situation improved dramatically in the early
1990s and currently the annual number of registered papers
approaches the number of papers registered in CA. It should
be emphasised that in spite of the large overlap of both sets
(SCI—CA), these sets are not identical.
Fig. 2 shows the subject orientation of the publication pro-
duction in 1998—2000. Compared with a similar histogram
from CA for almost 70 years (1931—1997) no significant
changes are found, but exchange of neighbouring positions.
Montmorillonite can be evaluated as the long term most cited
clay mineral. From the subject point of view, sets of papers on
individual clay minerals differ significantly. A special position
belongs to the papers on montmorillonite due to their high de-
gree of heterogeneity (Fig. 3). In the papers on montmorillo-
nite a chemical character prevails in contrast to the predomi-
nantly geological orientation of papers dealing with other clay
minerals. Besides the classical montmorillonite topics “sorp-
tion” and “catalysis”, a great part of the papers can be classi-
fied as material science. The proportion of papers on montmo-
rillonite-organic interaction is higher than that on montmo-
rillonite-inorganic interaction. However, considering the vast
prevalence of numbers of existing organic over inorganic com-
pounds, montmorillonite-inorganic interactions appear of
Fig. 3. Subject orientation of current publication production on
montmorillonite and mutual proportion of works in group “sorp-
tion” (works registered in the SCI in 1998—2000).
greater importance. The proportion of papers dealing with
sorption of radionuclides is currently much lower than 20
years ago. Papers with the subject “vermiculite” represent a
certain transition between papers on montmorillonite and oth-
er clay minerals, with a rather high proportion of chemical
The evaluation of scientific importance of publication activ-
ity is often derived from the citation response. Though this
work should not be looked at as a support for this opinion, it
provides necessary data for such considerations. For this pur-
pose, only papers with the key word “montmorillonite” pub-
lished in 1980—2000 were used since the number of hits in the
whole analysed set is too large and processing would be un-
comfortable. If citations from 1998—2000 are not taken into ac-
count (they represent only a small proportion of the total num-
Fig. 2. Number of papers dealing with individual clay minerals
registered in the SCI in period from 1980 to 2000.
CLAY SCIENCE FROM THE PUBLICATION AND CITATION PERSPECTIVE 135
Fig. 4. Citation counts in individual years (y-axis) registered in
the SCI for the 6 most cited papers on montmorillonite.
Corma 1997: From microporous to mesoporous molecular sieve materials and their use in catalysis. Chemical Reviews
Lvov et al. 1995: Assembly of multycomponent protein films by means of electrostatic layer-by-layer adsorption. Journal
of American Chemical Society
Occelli & Tindwa 1983: Physicochemical properties of montmorillonite interlayered with cationic oxyaluminum pillars.
Clays and Clay Minerals
Sterte 1986: Synthesis and properties of titanium-oxide cross-linked montmorillonite. Clays and Clay Minerals
Usuki et al. 1993: Synthesis of nylon 6-clay hybrid. Journal of Materials Research
Gu et al. 1994: Adsorption and desorption of natural organic-matter on iron-oxide — mechanisms and models.
Environmental Science & Technology
Clark et al. 1989: Montmorillonite supported transition-metal salts as Friedel-Crafts alkylation catalysts. Journal of
Chemical Society – Chemical communications
Ege et al. 1985: Clay modified electrodes. 3. Electrochemical and electron-spin resonance studies of montmorillonite
layers. Journal of American Chemical Society
Xing et al. 1996: Competitive sorption between atrazine and other organic compounds in soils and model sorbents.
Environmental Science & Technology
Aranda & Ruizhitzky 1992: Poly(ethylen oxide)-silicate intercalation materials. Chemistry of Materials
Yamanaka et al. 1984: High surface-area solids obtained by intercalation of iron-oxide pillars in montmorillonite.
Materials Research Bulletin
Koide 1991: Nutrient supply, nutrient demand and plant-response to mycorrhizal infection. New Phytologist
White & Bard 1986: Clay modified electrodes. 4. The electrochemistry and electron-spin-resonance of methyl viologen
incorporated into montmorillonite films. Journal of Electroanalytical Chemistry
Oster et al. 1980: Flocculation value and gel structure of sodium-calcium montmorillonite and illite suspensions. Soil
Science Society of America Journal
Plenchette et al. 1982: Effects of different endomycorrhizal fungi on 5 host plants grown on calcined montmorillonite clay.
Journal of the American Society for Horticultural Science
Clark & Macquarrie 1998: Catalysis of liquid phase organic reactions using chemically modified mesoporous inorganic
solids. Chemical Communications
Johnson et al. 1999: Ordered mesoporous polymers of tunable pore size from colloidal silica templates. Science
Keren et al. 1981: pH-dependent boron adsorption by Na-montmorillonite. Soil Science Society of America Journal
Kawai et al.1988: New application of solid acid to carbon-carbon bond formation reactios — clay montmorillonite-
catalyzed aldol reactions of silyl enol ethers with aldehydes and acetals. Bulletin of the Chemical Society of Japan
Barloy et al. 1990: Manganese porphyrins supported on montmorillonite as hydrocarbon monooxygenation catalysts –
particular efficiency for linear alkane hydroxylation. Journal of Chemical Society – Chemical communications
Table 1: 20 papers with highest citation index registered in the SCI database in 1980—2001 (C. C. – citation counts).
ber of citations), citation counts per one paper in this set varies
in a narrow range from 21 to 56 citations with an average of 36
citations/paper. It is quite interesting that almost exclusively
the two most cited works are responsible for the extent of the
range (minimum and maximum citations) while the values for
other papers are near the average. The average value for the 10
most cited works within the whole set is 109 citations/hit. The
subject orientation of a given set of papers with the greatest ci-
tation response represents approximately the whole publication
production in this research field (Table 1). Fig. 5 shows the av-
erage citation count per work of the 10 most significant works
published in the year 1980. Provided that we ignore an initial
part of the curve (1980), the average citation count/paper var-
ies around 18 citations/paper. The half-time of citation count/
paper in this group of papers far exceeds 20 years which is
considered a very high value in natural sciences. If the whole
group of all published papers is considered, the average time
between appearance of a paper in a journal and its citation “re-
action” is approximately 5 years. Fig. 4 shows the citation
counts for the 6 most cited papers in a given year.
An average number of citations per paper in the whole anal-
ysed set varies in a narrow range of 10 to 15 citations/paper.
Uncited publications comprise some 10 to 35 % of the total
number of published works. We assume that the average cita-
tion counts/paper of the whole publication production in clay
research would be significantly lower. This situation is partly
caused by lasting difficulties with finding relevant informa-
tion – these troubles are obviously of a general character and
not confined to clay research. This situation is, of course, in-
consistent with present possibilities of information services. It
could be explained by unattainable prices for complete infor-
136 JESENÁK, KUCHTA and HLAVATÝ
mation, at least in Central and Eastern European countries. In
this respect, the high degree of diversification of journals on
clays plays an important role, which has a very negative effect,
particularly on compilation of retrospective literature reviews.
It is just this fact, which is crucial in the unnatural outdating of
information. It is questionable whether the present major ori-
entation to review periodicals, such as Current Contents (and
also SCI) is, from the statistical point of view, an inevitable
consequence of present possibilities or a manifestation of a
free research philosophy.
The analysis of publication production in clay science field
offers possibilities for its objective evaluation and comparison
with production in other scientific fields. It is well known that
such evaluation is often used as a reason for justification of the
meaningfulness of research programs as well as their back-
ward evaluation. Opening of discussion about the philosophy,
strategy and organization of research information services at
academic workplaces in Slovakia can be considered as a by-
product of this analysis.
Acknowledgments: The authors would like to thank the com-
pany I.T.S. Slovakia, the Ministry of Education of the Slovak
Republic and ISI, Philadelphia for enabling us to access the
SCI database and for an inspiring example how to approach
problems in information services of academic workplaces.
Aranda P. & Ruizhitzky E. 1992: Poly(ethylen oxide)-silicate inter-
calation materials. Chemistry of Materials 4, 1395—1403.
Barloy L., Battioni P. & Mansuy D. 1990: Manganese porphyrins
supported on montmorillonite as hydrocarbon monooxygen-
ation catalysts – particular efficiency for linear alkane hy-
droxylation. Journal of Chemical Society – Chemical
communications 19, 1365—1367.
Clark J.H., Kybett A.P., MacQuarrie D.J., Barlow S.J. & Landon P.
1989: Montmorillonite supported transition-metal salts as
Friedel-Crafts alkylation catalysts. Journal of Chemical Soci-
Fig. 5. Illustration of citation count change of the 10 most impor-
tant papers (average value) published in 1980, assessed on the ba-
sis of the SCI citation counts per paper.
ety – Chemical communications 18, 1353—1354.
Clark J.H. & Macquarrie D.J. 1998: Catalysis of liquid phase organ-
ic reactions using chemically modified mesoporous inorganic
solids. Chemical Communications 8, 853—860.
Corma A., 1997: From microporous to mesoporous molecular sieve
materials and their use in catalysis. Chemical Reviews 97,
Ege D., Ghosh P.K., White J.R., Equey J.F. & Bard A.J. 1985: Clay
modified electrodes. 3. Electrochemical and electron-spin reso-
nance studies of montmorillonite layers. Journal of American
Chemical Society 107, 5644—5652.
Gu B.H., Schmitt J., CHen Z.H., Liang L.Y. & McCarthy J.F. 1994:
Adsorption and desorption of natural organic-matter on iron-
oxide – mechanisms and models. Environmental Science &
Technology 28, 38—46.
Jesenák K. & Kuchta . 1993: Analysis of publishing in montmoril-
lonite research. Proc.11th Conference on Clay Mineralogy and
Petrology, České Budějovice (1990), 315—320.
Jesenák K. & Kuchta . 1998: Selected attributes of publishing ac-
tivity in montmorillonite research. Scripta Fac. SCI. Nat Univ
Masarik. Brun., Geology 28—29, 143—148 (appeared in 2000).
Johnson S.A., Ollivier P.J. & Mallouk T. 1999: Ordered mesoporous
polymers of tunable pore size from colloidal silica templates.
Science 283, 963—965.
Kawai M., Onaka M. & Izumi Y. 1988: New application of solid
acid to carbon-carbon bond formation reactions – clay mont-
morillonite-catalyzed aldol reactions of silyl enol ethers with
aldehydes and acetals. Bulletin of the Chemical Society of Ja-
pan 61, 1237—1245.
Keren R., Gast R.G. & Baryosef B. 1981: pH-dependent boron ad-
sorption by Na-montmorillonite. Soil Science Society of Ameri-
ca Journal 45, 45—46.
Koide R.T. 1991: Nutrient supply, nutrient demand and plant-re-
sponse to mycorrhizal infection. New Phytologist 117, 365—386.
Lvov Y., Ariga K., Ichinose I. & Kunitake T. 1995: Assembly of
multycomponent protein films by means of electrostatic layer-
by-layer adsorption. Journal of American Chemical Society
Occelli M. I. & Tindwa R. M. 1983: Physicochemical properties of
montmorillonite interlayered with cationic oxyaluminum pil-
lars. Clays and Clay Minerals 31, 22—28.
Oster J.D., Shainberg I. & Wood J.D. 1980: Flocculation value and
gel structure of sodium-calcium montmorillonite and illite
suspensions. Soil Science Society of America Journal 44,
Plenchette C., Furlan V. & Fortin J.A. 1982: Effects of different en-
domycorrhizal fungi on 5 host plants grown on calcined mont-
morillonite clay. Journal of the American Society for
Horticultural Science 107, 535—538.
Sterte J. 1986: Synthesis and properties of titanium-oxide cross-
linked montmorillonite. Clays and Clay Minerals 34, 658— 664.
Usuki A., Kojima Y., Kawasumi M., Okada A., Fukushima Y.,
Kurauchi T. & Kamigaito O. 1993: Synthesis of nylon 6-clay
hybrid. Journal of Materials research 8, 1179—1184.
White J.R. & Bard A.J. 1986: Clay modified electrodes. 4. The elec-
trochemistry and electron-spin-resonance of methyl viologen
incorporated into montmorillonite films. Journal of Electroan-
alytical Chemistry 197, 233—244.
Xing B.S., Pignatello J.J. & Gigliotti B. 1996: Competitive sorption
between atrazine and other organic compounds in soils and
model sorbents. Environmental Science & Technology 30,
Yamanaka S., Doi T., Sako S. & Hattori M. 1984: High surface-area
solids obtained by intercalation of iron-oxide pillars in mont-
morillonite. Materials Research Bulletin 19, 161—168.