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Last-modified: 22 October 1999
Version: 1.17
Subject: 11. Traditional Specialist Chemical Information Sources
11.1 Where can I find spectral libraries/databases?
The most likely place is near to an instrument. These are not usually
in general technical libraries, but are kept near the instruments.
A polite request to the person in charge of the instrument should identify
who to contact for permission to use the library or database. There is
some spectral information in reference texts, such as the Rubber Handbook
and the Merck Index, but most compilations are now so large that they cover
several volumes. There are several compilations that are available
commercially, either in hard copy (HC) or CD-ROM (CD) - which is usually
more expensive because of the included searching software. Chemical
manufacturers, such as Aldrich, may also sell spectral libraries, eg
IR $495(HC) [1], FT-IR $875(HC) or $1578(CD) [2], 60MHz H1 NMR $495(HC) [3],
and 300MHz H1 + 75MHz C13 NMR $1072(HC) [4], as well as offering
compilations from government agencies, eg the NIST/EPA/NIH Mass Spectral
database $1320(CD)[5]. The databases are also sold by several instrument
manufacturers. One commercial supplier of spectral information ( Fiveash
Data Management, Inc. ) may be accessible via the Internet [6].
11.2 Where can I find polymer chemistry information?
The first stop should be the multi-volume Encyclopedia of Polymer Science
and Engineering [7], which should be in most technical libraries. Specific
polymers are covered in much less detail in Kirk Othmer. There are
several journals devoted to polymer science and chemistry, including the
Journal of Polymer Science.
11.3 Where can I find analytical chemistry information?
There is a sci.chem.analytical group where specific questions can be
posted after you have attempted to find the information in the following
sources. For qualitative information, the spot test books by Fiegl [8,9]
and "Semi-micro Vogel"[10], are good starting points. For introductory
quantitative analysis, "Quantitative Inorganic" [11],"Practical Organic
Chemistry"[12] by Vogel are good introductions to non-instrumental
techniques. The multi-volume "Treatise on Analytical Chemistry" by
Kolthoff and Elving [13] comprehensively discusses most techniques, and
several volumes of the ACS Series "Techniques in Chemistry" [14] also cover
analytical procedures. " Instrumental Methods of Analysis" by Willard,
Merritt, Dean and Settle [15], and "Analytical Instrumentation Handbook" by
Ewing [16] provide a good introduction to chemical instrumentation. Most
educational institutions will have equivalent texts if they are not using the
above.
For specific analyses it is often desirable to use standard procedures,
especially if your laboratory is seeking ISO 9001 accreditation, or if the
results are likely to be disputed. Some well known compilations of standard
methods include:-
Laboratory Reagents
- usually specified by manufacturers or chemical societies
BDH 'Analar' Standards for Laboratory Chemicals [17]
ACS Reagent Chemicals [18]
Materials, Industrial Chemicals, and Finished Products.
- usually the monographs in the following volumes also specify assay and
impurity limits, as well as detailing the analytical procedure.
ASTM - Issued annually, cover physical and chemical testing of a wide range
of industrial products. Often require specialised test equipment.
ISO - International standards, usually derived from US(ASTM), UK(BSI) or
FRG(DIN) standards. Similar to above.
Pharmaceuticals
- usually the pharmacopoeia have monographs and methods, but some methods
are also specified in National Formulary or Pharmaceutical Codex volumes,
which may be separate from the pharmacopoeia.
- common pharmacopoeia are USP, BP, and EP - with Martindale [19] often used
to ascertain where and when a specific monograph appeared.
Food
- often the procedures specified in Government legislation.
- The Official Methods of the AOAC [20] covers many routine US methods.
Environmental Pollution
- the procedures are usually specified in the relevant legislation, and
frequently US EPA procedures are used. Several common EPA procedures are
now available on computer disk [21,22].
Petroleum
- usually covered by ASTM, ISO or DIN, but there are some unique IP
( Institute of Petroleum - UK ) procedures that are also used.
- "Chromatography in Petroleum Analysis"[23], summarises popular techniques.
Gases
- instrument manufacturers have fairly detailed procedures for process gases.
- "The Analysis of Gases by Chromatography"[24], provides useful examples.
Water and Wastewater
- the APHA/WWA/WPCF standard methods are most often used [25]
- many tests are also covered by ASTM, ISO, and DIN procedures
- alternative techniques are described in "Water Analysis" [26]
- organics in water are covered by Crompton [27]
- most aspects of water chemistry are detailed in Franks [28]
Sample Preparation
- consumable and instrument manufacturers often provide detailed manuals
and guides free.
- "Methods of Decomposition in Inorganic Analysis" [29] covers a wide range
of preparations for spectroscopy.
- The "Handbook of Analytical Derivatization Reactions" [30] and the
" Handbook of Derivatives for Chromatography" [31] cover many of the
techniques for gas and liquid chromatography.
Obviously there are several journals devoted to various aspects of
analytical chemistry. The April issue of Analytical Chemistry publishes
a review of papers published during the previous two years. The review
alternates between Fundamental and Application Reviews and is a quick means
of catching current trends if you are unable to locate an expert.
11.4 Where can I find environmental chemistry information?
There are several standard texts used by environmental chemistry classes
that provide good general introductions, eg "Environmental Chemistry" [32]
"Fundamentals of Environmental Chemistry [33], and "Environmental Organic
Chemistry" [34]. They should be available in most technical libraries. The
monthly journal "Environmental Science and Technology" covers most aspects
of environment chemistry. "Chemosphere" concentrates on toxins such as PCBs
and Dioxin, and " Science of the Total Environment also covers many aspects.
Government agencies such as the EPA also publish large amounts of
information, and many environmental groups also provide significant amounts
of technical information. There are a range of specialist texts that cover
specific pollutants, eg "Metals and their Compounds in the Environment:
Occurrence, Analysis and Biological Relevance" [35].
The sci.environment Usenet group may well be a better place to request
environmental chemistry information than sci.chem, but please remember
to move discussions to talk.environment.
11.5 Where can I find physical chemistry information?
General introductory information will be available in any technical library
where chemistry is taught, and one of the more popular modern texts is
"Physical Chemistry" by P.W.Atkins [36], and a classical text is
"Textbook of Physical Chemistry" by S.Glasstone [37]. The multi-volume ACS
series "Physical Methods of Chemistry"[38] also covers many physical
chemistry techniques. There are also the Journal of Chemical Physics and the
Journal of Physical Chemistry. Frankly, I would not have a clue where else
to go.
11.6 Where can I find inorganic chemistry information?
General introductory information will be available in any technical library
where chemistry is taught. One popular text is "Inorganic Chemistry" by
D.F.Shriver, P.W.Atkins, and C.H.Langford [39], which also has the answers
available as a separate book. "Inorganic Vogel"[40], also discusses the theory
of the analyses. There are three major multi-volume inorganic encyclopedias.
Mellor is frequently found in public libraries, and provides a broad cover
of the field, however the more comprehensive is Gmelin [41], which will be
available in most institution libraries. The more recent developments and
mechanisms are covered in the multi-volume "Encyclopedia of Inorganic
Chemistry" [42], which may be difficult to find due to its $2500 price.
"Advanced Inorganic Chemistry" [43] by F.A.Cotton and G.Wilkinson provides a
good base to start. There are several journals that cover aspects of
inorganic chemistry.
11.7 Where can I find organic chemistry information?
General introductory information will be available in any technical library
where chemistry is taught. One popular modern text is " Organic Chemistry "
by T.W.G.Solomons [44], but my favourite is "Organic Chemistry"[45] by Fieser
and Fieser - a much more practical discussion of organic molecules.
Once you are familiar with organic chemistry mechanisms then "Advanced
Organic Chemistry" by Carey and Sandberg [46] is a good overview.
There are several compilations of organic synthesis techniques to assist
researchers. The multi-volume sets "Organic Reactions" [47], and "Reagents
for Organic Synthesis" [48], are examples of sets that will be available from
institution libraries. There are some good theoretical texts available, eg
"The Logic of Chemical Synthesis" [49]. For specific preparation and
properties of individual compounds, then Heilbron [50] and Beilstein [51],
are the initial resources of choice. There are several journals devoted to
organic chemistry in general, including Journal of Organic Chemistry,
Tetrahedron, etc.. Specific branches of organic chemistry, such as
Carbohydrates, Lipids, or Proteins have their own journals, as do
applications such as pharmaceuticals and pesticides.
11.8 Where can I find industrial chemistry information?
The best single volume remains Shreve's "Chemical Process Industries" [52].
There are three major multi-volume encyclopedias, Kirk Othmer, Ullmann,
and McKetta, that cover many aspects of industrial chemistry and at
least one is usually available in a public library. There are also several
journals that provide good overviews of industrial chemistry, the easiest
to read being C&EN, and Chemtech. Research is usually published
in Industrial and Engineering Chemistry ( which is an excellent source
for historical research ), and specialist chemical engineering journals.
11.9 Where can I find pharmaceutical chemistry information?
Pharmaceutical research often is initially reported in patent literature,
consequently patent searching is a good place to start. The Merck Index is
focused on pharmaceuticals, and also provides excellent leads to the
research literature. There are several pharmaceutical chemistry books, such
as Goodman and Gilman [53], and "Essentials of Medicinal Chemistry" [54],
that provide overviews of the field. The Journal of Pharmaceutical Chemistry
is a good source for research articles. Details of chemicals appearing in
formulated products can be found in the "Handbook of Pharmaceutical
Excipients" [55].
------------------------------
Subject: 12. Nomenclature
12.1 What are CAS Registry Numbers?
When chemicals are first encountered by the Chemical Abstracts Service, they
are assigned a unique number when they are registered. These numbers are not
related to any structure or property of the molecule, they are arbitrarily
assigned. It should be remembered that occasionally a compound may be
accidentally assigned two or more numbers - especially industrial products
that have not been completely characterised. When this is discovered, one of
the numbers is no longer used. The numbers usually take the form of
[xx-yy-z to xxxxxx-yy-z] and square brackets are often used in monographs to
identify the CAS Registry Number [RN]. The easiest way to locate the CAS RN
for commercially-available chemicals is to look in suppliers catalogues
( eg Aldrich) or compilations ( eg Merck or Hawley ), almost all chemical
texts now list the RN, and several ( eg Merck Index and Aldrich ) have a
cross-reference Index. The RN is extremely useful for on-line searching of
Chemical Abstracts and several other popular chemistry-related databases,
but is not particularly useful for the hardcopy version, except to confirm
compound identity.
12.2 What are the correct names of recently-discovered elements?
The Transfermium Working Group was established in 1986 by the International
Union of Pure and Applied Chemistry (IUPAC) and the International Union of
Pure and Applied Physics (IUPAP). The working group published several
reports, and then recommended that elements should not be named after living
persons [1]. This greatly upset the USA - who wanted to name an element after
G. Seaborg. After protracted negotiations, a compromise selection of names
was finally approved by the IUPAC Commission on Nomenclature in Inorganic
Chemistry, the IUPAC Inorganic Division, the IUPAC Bureau, and the selection
was eventually ratified by the IUPAC Council meeting in Geneva during August
1997 [2].
101 Mendelevium Md D. Mendeleev (Russia)
102 Nobelium No Nobel Institute (Sweden)
103 Lawrencium Lr E. Lawrence (USA)
104 Rutherfordium Rf E. Rutherford (NZ)
105 Dubnium Db Dubna = Russian Research Centre
106 Seaborgium Sg G. Seaborg (USA)
107 Bohrium Bh N. Bohr (Denmark)
108 Hassium Hs Latin name for German state of Hesse
109 Meitnerium Mt L. Meitner (Austria)
Note that Hesse is where the German heavy-element laboratory is based.
The Gesellschaft fur Schwerionenforschung (GSI) was responsible for the
first man-made creation of elements 107-110. The compromise will now move
attention to the naming the recently-discovered elements 110-112.
12.3 What is the nomenclature system for CFCs/HCFCs/HFCs?
The CFC naming system was developed by T.Midgley,Jr. and A.L.Henne in 1929,
and further refined by J.D.Park. Originally, organic molecules that contained
Chlorine and Fluorine were all referred to as CFCs. Today, the group is
subdivided into CFCs, HCFCs, and HFCs. The naming system consists of:-
CFC-01234a where 0 = number of double bonds ( omitted if zero )
1 = Carbon atoms - 1 ( omitted if 0 )
2 = Hydrogen atoms + 1
3 = Fluorine atoms
4 = Chlorine atoms replaced by Bromine ("B" prefix added )
a = letter added to identify isomers, the "normal" isomer
in any number has the smallest mass difference on each
carbon, and a, b, or c are added as the masses diverge
from normal.
If the compound is cyclic, then the number is prefixed with "C". There are
several other refrigerants, some of which are hydrocarbons, hydrocarbon
blends, or CFC blends. Full details of the nomenclature system are specified
in ANSI/ASHRAE Standard 34-1992 with additional annual supplements. Chemical
names are frequently used in place of the numbers for common materials
- such as trichloroethylene and chloroform. The specified ANSI/ASHRAE
prefixes were FC ( FluoroCarbon ), or R ( Refrigerant ), but today most are
prefixed by more specific classifications - such as CFC, HCFC, and HFC.
CFC-11 CCl3F trichlorofluoromethane [75-69-4]
CFC-12 CCl2F2 dichlorodifluoromethane [75-71-8]
CFC-113 CCl2F-CClF2 1,1,2-trichlorotrifluoroethane [76-13-1]
HCFC-22 CHClF2 chlorodifluoromethane [75-45-6]
HCFC-123 CHCl2-CF3 2,2-dichloro-1,1,1-trifluoroethane [306-83-2]
HCFC-123a CHClF-CClF2 1,2-dichloro-1,1,2-trifluoroethane [354-23-4]
HFC-23 CHF3 trifluoromethane [75-46-7]
HFC-134 CHF2-CHF2 1,1,2,2-tetrafluoroethane [359-35-3]
HFC-134a CH2F-CF3 1,2,2,2-tetrafluoroethane [811-97-2]
R-20 CHCl3 chloroform [67-66-3]
R-22B1 CHBrF2 bromodifluoromethane [1511-62-2]
R-1120 CHCl=CCl2 trichloroethylene [79-01-6]
R-1150 CH2=CH2 ethylene [74-85-1]
R-C316 C4Cl2F6 1,2-dichlorohexafluorocyclobutane
Another technique for naming CFCs uses the addition of 90 to the CFC number
to produce a "def" number which corresponds to the CHF composition. If
(e + f) < (2d + 2), then additional atoms are required for saturation. This
technique has been described in detail in the Journal of Chemical Education
[3].
ASHRAE +90 Empirical Composition Formula
C H F (+Cl)
CFC-11 101 1 - 1 3 CCl3F
CFC-12 102 1 - 2 2 CCl2F2
HCFC-22 112 1 1 2 1 CHClF2
HCFC-123 213 2 1 3 2 CHCl2-CF3
HFC-134a 224 2 2 4 - CH2F-CF3
Halons are numbered according to a totally different system developed by
the US Army Corps of Engineers, and the prefix term is always "Halon".
Hydrogen is not numbered, and terminal zeros are not expressed.
Halon-0123 where 0 = number of carbon atoms
1 = number of fluorine atoms
2 = number of chlorine atoms
3 = number of bromine atoms
Halon-1211 CBrClF2 bromochlorodifluoromethane [353-59-3]
Halon-1301 CBrF3 bromotrifluoromethane [75-63-8]
Halon-2402 CBrF2-CBrF2 1,2-dibromo-1,1,2,2-tetrafluoroethane [124-73-2]
12.4 How can I get the IUPAC chemical name from traditional names?
It depends. Usually the quickest way is to look the name up in a chemical
supplier's catalog, MSDS, or a standard text like Merck or Hawley. You can
also often find the correct name if you refer to an old chemistry text that
lists both the traditional and IUPAC naming conventions. Some traditional
or common names also refer to mixtures of chemicals, eg aqua regia, piranha
solution.
One reason why traditional names have been replaced is because the same name
could be used for different compounds. An example is the use of caprylic to
describe 1-Octanol and 2-Octanol, and attempts to qualify the name with
"primary" and "secondary" were less than successful. Octyl alcohol has been
used to describe both 1-octanol and 2-ethylhexanol, thus explaining why the
well known dioctyl phthalate (DOP) is actually bis(2-ethylhexyl) phthalate.
The following examples highlight the diversity of names often encountered.
Carbon Alkane Alcohol Aldehyde Acid
1 methane methanol form- formic
carbinol
2 ethane ethyl acet- acetic
methyl carbinol
3 n-propane n-propyl propion- propionic
ethyl carbinol
4 n-butane n-butyl n-butyr- n-butyric
propyl carbinol
5 n-pentane n-amyl n-valer- n-valeric
butyl carbinol
6 n-hexane hexyl capro- caproic
amyl carbinol caproic
7 n-heptane enanthyl enanth- enanthic
enanthic
hexyl carbinol
8a n-octane capryl capryl- caprylic
primary caprylic caprylic
heptyl carbinol
1-octanol
8b capryl
secondary caprylic
methyl hexyl carbinol
2-octanol
9 n-nonane pelargonic pelargonic pelargonic
octyl carbinol
10 n-decane capric capr- capric
nonyl carbinol capric
12 n-dodecane lauryl laur- lauric
lauric lauryl
14 n-tetradecane myristyl myrist- myristic
16 n-hexadecane cetyl palmit- palmitic
cetane
18 n-octadecane stearyl stearic
20 n-eicosane arachidyl arachidic
Primary
- alcohol R1CH2OH
- amine R1NH2
eg normal straight chain normal octane n-octane
normal butanol 1-butanol
iso branched chain iso-butane 2-methylpropane
iso-butanol 2-methyl-1-propanol
iso-octane 2,2,4-trimethylpentane
Secondary
- alcohol R1R2CHOH
- amine R1R2NH
eg sec-butanol 2-butanol
iso-propanol 2-propanol
Tertiary
- alcohol R1R2R3COH
- amine R1R2R3N
eg tert-butanol 2-methyl-2-propanol
- substitution onto the benzene ring
1,2 = ortho ortho-xylene
1,3 = meta meta-xylene
1,4 = para para-xylene
However other names get more tricky, especially historical names, where
several names may be used for the same chemical and, even worse, different
chemicals can be described by the same name. Examples include:-
- calcium carbonate = limestone, chalk, calcite.
- calcium hydroxide = slaked lime, hydrated lime, caustic lime.
- calcium oxide = calx, lime, quicklime, unslaked lime, burnt lime.
- hydrochloric acid = muriatic acid, spirits of salts.
- nitric acid = aqua fortis.
- potassium carbonate = potash, artificial alkali, vegetable alkali.
- potassium hydroxide = caustic potash, lye.
- sodium carbonate - any form = soda, natural alkali, mineral alkali.
- anhydrous = soda ash.
- dodecahydrate = sal soda, washing soda.
- monohydrate = soda crystals.
- sodium chloride = rock salt.
- sodium hydroxide = caustic soda, lye, soda lye.
- sulfuric acid = oil of vitriol
Some old chemical terms are seldom encountered these days, but have very
specific meanings, eg
" flowers " described any product of sublimation, hence "flowers of sulfur".
" specific " in front of any quantity means " divided by mass ", hence
"specific gravity".
" ether " described a volatile liquid, not only compounds with the Cx-O--Cy
structure, and also often known today as "spirit".
" aromatic " described a liquid that had an aroma, not only those derived
from benzene, or which benzene ring structure.
" oil " described a liquid that was not miscible with water, thus it
described different products in different chemical industries :-
- Essential oils = volatile and odoriferous liquid plant extracts.
Essential oils can be obtained by extraction or distillation ( steam ),
often contain terpenes ( based on the isoprene structure ), are usually
smelly ( aromatic ), and are used for perfumes, flavours and aromas, eg
lemon oil and pine oil.
- Triglyceride oils = fats and oils based on the glycerol molecule that
can be obtained from plant and animal material, frequently by melting or
cold pressing. They are a significant, and important, component in our
diet, eg soya oil, lard, fish oils, and anhydrous milk fat.
- Petroleum oil = a mixture of a large number of hydrocarbons that are
usually derived from 0.1 to 3 billion-year-old organic matter. Crude oil
can contain hundreds of hydrocarbons with one to sixty carbon atoms, and
the hydrocarbons are usually grouped and reported by type, eg alkane
( paraffin ), alkene ( olefin ), or arene ( aromatic ).
Almost all old industries had easy-to-remember names for chemicals they
commonly encountered, but today many of those names can cause confusion
if used outside the industry. Some common examples, just from the petroleum
industry alone are:-
- " ether " is a volatile hydrocarbon fraction that does not contain the
Cx-O-Cy structure, eg petroleum ether ( aka petroleum spirit ).
- " naphthene " is a cyclic paraffin, does not contain naphthalene, and is
not a major component of naphtha ( refer Section 27.5 ).
- Benzene, toluene and xylene are often called benzol, toluol, and xylol,
even though they do not contain an -OH group.
- Benzine ( ligroin ) was a saturated hydrocarbon fraction that boiled
between 20C and 135C. Gasoline/petrol fractions are still called benzine
by some older people.
- Diesel fuel is often called "gas oil", which is a historical term for
hydrocarbon distillate fractions. Atmospheric gas oil has a boiling
range between 220C - 450C, and vacuum gas oil boils from 350C to 550C.
12.5 What does "omega-3 fatty acids" mean?
Chemists recognise that they should always number carbon chains from the
end with the functional group, so the location of double bonds in
unsaturated fatty acids are numbered from the carboxylic acid end, and
are usually designated by "delta" in their abbreviated names.
Biochemists are more interested in the actual role that chemicals play,
consequently they will consider the position from the end that is important.
In the case of natural fatty acids the double bonds are usually cis
configured, and it is the distance of the first double bond from the
terminal end of the carbon chain that is important. They use "omega" to
signify that the double bond is cis, and they are counting from the other
end. The great advantage is that chain length can be ignored, and compounds
that are subjected to the same biochemical processes are grouped together.
In 1967, the IUPAC/IUB commission responsible for lipid nomenclature
recommended that for unsaturated fatty acids with cis double bonds, that
the "omega" symbol be replaced with "n-x", where n = the length of the
carbon chain, and x is the distance from the terminal end.
Some examples:-
Common Chemical Chemical Biochemical
Name Name d = delta o = omega
Oleic cis-9-octadecenoic c-C18:1d9 C18:1o9
Elaidic trans-9-octadecenoic t-C18:1d9 -
Ricinoleic D-(+)-12-hydroxy-octadec-cis-9-enoic c-C18:1d9-12OH -
Linoleic cis-9,12-octadecadienoic c-C18:2d9 C18:2o6
alpha Linolenic cis-9,12,15-octadecatrienoic c-C18:3d9 C18:3o3
gamma Linolenic cis-6,9,12-octadecatrienoic c-C18:3d6 C18:3o6
Arachidonic cis-5,8,11,14-eicosatetraenoic c-C20:4d5 C20:4o6
EPA cis-5,8,11,14,17-eicosapentaenoic c-C20:5d5 C20:5o3
Erucic cis-13-docosenoic c-C22:1d13 C22:1o9
DHA cis-4,7,10,13,16,19-docosahexaenoic c-C22:6d4 C22:6o3
EPA and DHA are widely known as the omega-3 fatty acids present in high
concentrations in marine lipids, and are considered beneficial in diet,
although research is not complete [4,5].
12.6 What is Conjugated Linoleic Acid?
Conjugated linoleic acid describes the group of positional and geometric
isomers of linoleic acid ( cis-9,12-octadecadienoic acid ) that have a
conjugated double bond system starting at carbon 9, 10, or 11. They can be
either cis or trans, or various combinations of them. The more abundant
isomers in food are believed to be the cis-9, trans-11, and the trans-10,
cis-12 isomers. It's very difficult to separate the cis-9, trans-11 and
trans-9, cis-11 isomers, however the cis-9, trans-11 form is usually
considered the important and usually dominant isomer.
They are typically produced by bacteria in the rumen of ruminants because
the hydrolysis of fats in the rumen produces more unesterified linoleic
acid than is available to bacteria in other digestive systems. Plants
also contain conjugated linoleic acid, but there is much less of the
cis-9, trans-11 isomer, which is believed to be the biologically active
isomer. Foods that contain CLA are lamb, beef, turkey and dairy fat products,
ranging from 2.5 - 11 mg/g of fat - of which 75% or more is the cis-9,
trans-11 ( or trans-9, cis-11 ) isomer. CLA is of interest because it has
displayed antimutagenic activity in animals and human cell tests [6,7].
12.7 What are "heavy" metals?
There appears to be no standard definition, however the general consensus
appears to be all metals with a density greater than 4 or 5 [8,9,10]. If
you also consider the conventional analytical chemistry definition of "heavy
metals" ( precipitation of sulfides from acidic solutions ), you obtain
quite a diverse mixture of possible candidates. Moving the density limit
from 4 to 5 really only just impacts on Ti, Y and Se. Some other texts use
more complex definitions that may also include accepted "light" metals with
densities less than 4, eg Hawley uses "A metal of atomic weight greater
than sodium (22.9) that forms soaps on reaction with fatty acids. e.g.,
aluminum, lead, cobalt". The term " heavy-element " is commonly used to
describe the transfermium elements, - elements with an atomic number
greater than 100.
12.8 What is the difference between Molarity and Normality?.
A Molar solution contains one gram molecular weight ( aka mole ) of the
reagent in one litre of solution, and is represented by " M ". In modern
usage, "molar" is intended to only mean " divided by amount of substance",
and is not supposed to be used to describe 1M solutions. There are already
exceptions to the rule ( molar conductivity, molar extinction coefficient ),
so I would only worry about correct usage in exams, as in the real world
most chemists use Molar to describe 1M solutions.
A Molal solution is one gram molecular weight of the reagent in 1 kilogram
of solvent, and is usually represented by "m". This concentration unit is
relatively uncommon in the real world, so it's worth checking that the "m"
is not a "M" typo.
A Normal solution contains one gram equivalent weight ( aka equivalent )
of the reagent in one litre of solution, and is represented by " N ".
The equivalent weight of a reagent may vary according to the reaction, but
if considering just acid and base moles and equivalents, then:-
1M H2SO4 + 2M NaOH -> 2H2O + Na2SO4
1N H2SO4 + 1N NaOH -> H20 + 0.5Na2SO4
1N HCl + 1N NaOH -> H2O + NaCl
So you can see that the equivalent weight of an acid is that which contains
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