Chemistry in the Marketplace

By Ben Selinger and Russell Barrow

Chemicals are everywhere. Many are natural and safe, others synthetic and dangerous. Or is it the other way around? Walking through the supermarket, you might ask yourself: Should I be eating organic food? Is that anti-wrinkle cream a gimmick? Is it worth buying BPA-free plastics?

This new edition of Chemistry in the Marketplace provides fresh explanations, fascinating facts and funny anecdotes about the serious science in the products we buy and the resources we use. It might even save you some money.

With chapters on the chemistry found in different parts of our home, in the backyard and in the world around us, Ben Selinger and Russell Barrow explain how things work, where marketing can be deceptive and what risks you should really be concerned about.

Chemistry in the Marketplace is a valuable resource for university lecturers, high school teachers and students of chemistry and chemistry related subjects and disciplines, such as biochemistry, microbiology and science in society.

• Language: English
• Publisher: CSIRO PUBLISHING
• Release date: Jun 1, 2017
• ISBN: 9781486303342

Book preview

Sixth Edition

CHEMISTRY IN THE

MARKETPLACE

BEN SELINGER AND RUSSELL BARROW

Sixth edition

CHEMISTRY IN THE

MARKETPLACE

BEN SELINGER AND RUSSELL BARROW

This edition is dedicated to five grandchildren, Jasper, Hannah, Elke, David and Flynn and their cohorts for whom life will depend even more on understanding science and technology than has ours.

Source: Adam Selinger.

© Ben Selinger and Russell Barrow 2017

All rights reserved. Except under the conditions described in the Australian Copyright Act 1968 and subsequent amendments, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, duplicating or otherwise, without the prior permission of the copyright owner. Contact CSIRO Publishing for all permission requests.

The moral rights of the author(s) have been asserted.

National Library of Australia Cataloguing-in-Publication entry

Selinger, Ben, 1939– author.

Chemistry in the marketplace / Ben Selinger and Russell Barrow.

Sixth edition.

9781486303328 (paperback)

9781486303335 (epdf)

9781486303342 (epub)

Includes bibliographical references and index.

Chemistry.

Chemistry – Popular works.

Barrow, Russell, author.

Published by

CSIRO Publishing

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Australia

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Front cover (top to bottom): face scrub (Steve Cordory/Shutterstock); blue paint (rangizz/Shutterstock); electric car (Nerthuz/Shutterstock); water bottle (Mariyana M/Shutterstock)

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Contents

Preface

Acknowledgements

About the authors

1     Molecular musings

2     Chemistry of health and risk

3     Chemistry of surfaces

4     Chemistry in the laundry

5     Chemistry in the kitchen

6     Chemistry in the dining room

7     Biochemistry of metabolism and sport

8     Chemistry of cosmetics

9     Chemistry in the medicine cabinet

10   Chemistry of plastics and glass

11   Chemistry of fibres, fabrics and other yarns

12   Chemistry in the garden

13   Chemistry of hardware and stationery

14   Chemistry in the swimming pool

15   Chemistry at the beach

16   Biological effects of metals and metalloids

17   Chemistry in the energy sector

18   Chemistry of ionising radiation

19   Experiments

Appendix 1: Nomenclature in chemistry

Appendix 2: Reporting amounts of material (units)

Appendix 3: Prevalence of logarithmic scales

Appendix 4: How much is safe?

Appendix 5: Phase diagrams

Appendix 6: Metal foils

Appendix 7: Metal alloys

Appendix 8: Maillard reaction

Appendix 9: Refractive index

Appendix 10: Glass transition temperature (Tg)

Appendix 11: The entropy game

Glossary

Index

Preface

It was over three glasses of cold, artificially coloured, artificially foam-stabilised, enzyme-clarified, preserved, gassed amber fluid in 1973 that Mal Rasmussen, Derry Scott and I (Ben Selinger) came to the realisation that we ought to be teaching consumers some real chemistry relevant to our lives, so that they could hope to make some sense of the arguments that rage in the media. The course that we developed accordingly ran under the auspices of the Australian National University Centre for Continuing Education with the alliterative title ‘Chemical Consciousness for Concerned Consumers’. The notes and title for that 1973–1975 course evolved into a book. The first commercial edition of Chemistry in the Marketplace was published by ANU Press and John Murrays (UK) in 1975.

The need for this type of reference is shown by the fact that in 1988 new national guidelines came into effect for chemistry teaching in the UK that took into account the approach used in Chemistry in the Marketplace. Across the Atlantic in the same year, the American Chemical Society produced their own book for schools, with the same philosophy, called Chemistry in the Community (ChemCom), under the project management of Sylvia A. Ware. A tertiary version, Chemistry in Context: Applying Chemistry to Society, followed in 1994.

The problem faced in the first few editions of Chemistry in the Marketplace was that of obtaining any information at all ‘off the beaten track’. In the following decades, both industry and government have become more open and user friendly. (The set of earlier editions provide a nice social history of how the issues in the marketplace have changed over 40 years. Don’t throw them out!) There has been an international explosion in popular books dealing with chemistry for consumers, and a tsunami on information on the world wide web. But it takes time and experience to assess the glut, and separate the wheat from the chaff.

During a sabbatical in Europe in 1991, I toured with a lecture called ‘Chemistry for tourists’. I was struck that what I wanted as a tourist in Europe was for someone else to use their experience to sift through all the information about what to do and see, and present me with a sample of what might be of most use and interest. I took this approach for the later editions of Chemistry in the Marketplace – to be a tourist guide to chemistry. We are taking you through a foreign country, pointing out and explaining landmarks we hope will interest you, giving the cultural setting, telling a few funny stories, helping you with the shopping, and explaining that the natives (in the chemical industry) can often be reasonably friendly. We will also warn you against salespeople who will try to strip your wallets with pseudoscience. Tour guides work in a very difficult profession. When describing culture and interpreting language, cultural differences continuously make life difficult. We know that in this book the original language, chemistry, is not always captured in all its glory. Forgive us.

In revising new editions of this book, my philosophy has always been to follow the aphorism of the Queen of Hearts in Alice in Wonderland, ‘Sentence first – verdict afterwards’. That is, give me a reason for wanting to learn chemistry and then I might deign to consider spending time and effort on it. Traditional approaches tackle chemical concepts in a systematic manner and may follow on with some illustrative examples. Chemistry in the Marketplace reverses the process by starting with relevant consumer experiences and providing the associated chemical concepts. This acknowledges the power of informal learning, as seen in the way children learn a game such as chess or using a smart phone.

Chemistry in the Marketplace also draws on the philosophy of Richard Feynman who said ‘the same equations have the same solutions’. (His was the inspiration for my book, MacFourier, Oxford University Press, 1991.) We show how the same chemical concepts keep on popping up in diverse consumer-interesting areas, often disguised by different names. Recognising these not only makes explaining more efficient, but also increases the incentive to make the effort to understand something that has multiple applications. These concepts are given a succinct exposure in Chapter 1 and are pointed out by cross-referencing in the individual chapters, where the same concept may be discussed with a different slant. Thus, surfactants are essential in the laundry and kitchen, important in cosmetics, and dominate modern paints. Logarithmic scales have their own appendix (Appendix 3) because they are relevant to so many facets of life and are touched on throughout the book.

So what does this book aim to achieve? One response is to stimulate curiosity and develop a deeper commitment to learning. Learning chemistry properly is hard, but so is sport, acting, music and writing literature … Start with fun and, in many cases, enthusiasm and dedication will follow. Another aim is to explain the less digestible basic sciences through everyday examples. For chemists, consumer aspects make the subject more relevant. For consumers, gaining some understanding for the chemistry deepens their appreciation of what they are using.

Chemistry in the Marketplace is not a textbook and follows no chemistry syllabus; rather it is a reference for students, teachers and the general reader. It provides material over a large spread of levels and caters for the cover-to-cover reader, as well as for those who just pop-in. Skip as you feel comfortable.

The further reading lists at the end of each chapter suggest only a small opening gambit. Stable URLs are likely to be more accessible than books, so we have focussed on those. Most learned society journal publications require payment for access, although a few offer a very limited amount of free material. Official government, quasi-government (e.g. CSIRO, ABC) and university sites tend to be free and reliable, but may not be regularly updated. Blogs are great fun, but can be of questionable quality. A major skill need for the 21st century is the ability to judge quality on the internet. Books like this one go through a drawn-out peer review process and hawkeyed editing. You have made a good choice!

While many authors might write six books, this author has written the same book six times. This Sixth Edition has been consolidated by directing the reader to selected stable and reliable web references for further information. It is fully updated throughout, with completely redrawn illustrations, new appendices and new chapters on biochemistry (Chapter 7), the beach (Chapter 15) and the biological effects of metals and metalloids (Chapter 16). It also contains a chapter dedicated to experiments (Chapter 19) that illustrate concepts found within the text. Some simple experiments are also included with the chapters. My writing has, of course, been influenced through my training as a physical chemist. Luckily for this edition, it is balanced by Dr Russell Barrow who is a chemical chemist.

Ben Selinger

Chemistry in the Marketplace was a book I (Russell Barrow) grew up with. As a generation X’er, when I was at school and then in my early years of university, the internet wasn’t there and this book was often my first stop when I needed to know something about chemistry in a practical context. For example, it taught me that swimming pools don’t have too much chlorine when they have that familiar pool smell, but too little. It taught me that it is too little chlorine that makes your eyes red, not too much! Now we have the internet, a lot of our questions can be answered by going there. This newest edition of the book doesn’t try to replace the internet. Instead we use it to complement the book. As already mentioned, many of the references will direct you to websites. So the problem now isn’t finding the information to answer a question but rather knowing what question to ask. This book will start you down the path of asking questions. Hopefully you’ll find this book whets your appetite and many more questions will result from reading it.

So how did I find myself involved with this book? As an academic in chemistry at the Australian National University (ANU) my days are full of teaching and research. I have been incredibly lucky to have been able to explore the world around me, discovering molecules and their roles in nature. As a natural product chemist, my current research looks at the molecules contained in mushrooms that are used by indigenous communities in Papua New Guinea or tries to understand the relationships that allow a plant to trick a male wasp into thinking it is a female wasp, with this seduction achieving its goal of pollination. Chemistry really is amazing! During my time at the ANU I also had the good fortune to meet Ben Selinger. On many occasions, often over a cup of coffee, I would listen with interest as he would talk about his latest article in the science section of The Canberra Times (our daily newspaper here in the ACT) or in a popular magazine. Finding a sympathetic ear, I would talk about the way I liked to introduce tangents into my lectures by bringing in aspects of chemistry that were relevant to the real world. I joked about giving a lecture course called ‘The Chemistry of Tangents’. When I was asked to be involved with writing this edition, it came with the warning from Ben that it was a lot of work and would take a lot of time. I was to find out he lied. It took a tonne of work and all of my time! I have written parts of this book in five continents, from the comfort of my desk at home in Canberra to admiring the views of the Incan ruins of Machu Picchu in Peru. It has been an exhausting and rewarding experience that I hope you, the reader, find a useful addition to your library.

Russell Barrow

Acknowledgements

This 6th edition was initiated by Julia Stuthe at CSIRO Publishing and only eventuated because I was joined by a co-author and erstwhile colleague at ANU, Russel Barrow, who has provided a much needed extra specialist chemical input.

Lauren Webb took on the task of being the developmental editor of a book that was now living in the age of the internet and was virtually being rewritten. She bridged the gap between technical and readable with a skill exceeding those in earlier editions. Thanks also go to Tracey Millen, who dealt with the nitty gritty of the editorial and production processes. Copy editor Peter Storer took on the difficult task of melding the content and styles of two authors, disparate chapters and a very wide range of complexity in the material covered. As well, he added considered views on the material itself. Authors need reminding of the importance of the editorial and production team.

I am also grateful to those who edited previous editions of the book including Patricia Croft (ANU Press, 1st and 2nd editions), Dallas Cox and Carol Natsis (Harcourt Brace Jovanovich, 3rd and 4th editions, respectively), and Penny Martin and Ken Tate (Harcourt Brace, 5th edition). There cannot be enough thanks to Judy Bahar for her fast and dedicated efforts in punctiliously checking drafts of all the chapters and appendices at an early stage and suggesting many corrections and improvements.

Many hours spent with my mate from university student days, the late Dennis Leonard, are remembered for our stimulating discussions and his help with chemistry, computing, consumerism and industrial archaeology, during our travels and walks throughout the Sydney basin. We rode every train line in Sydney and most bus routes before he died after a very short illness. There are a number of statistical arguments in this book. It is to the late Professor Peter Gavin Hall AO, FRS, who was my colleague at ANU, that I am indebted for decades of explanation of matters statistical to a slow mathematical learner. We grew up, unknowingly, within a kilometre of each other in the (then) last metropolitan southern suburb of Sydney. Professor Ian Rae FTSE is thanked for cultural, historical, philosophical and of course, chemical discussions covering many editions of this book.

Ms Jenny Selinger, Head of Science at Emanuel College, in Randwick NSW, brought ideas and a reality check to some of the material aimed at students. Son Adam Selinger of Children’s Discovery Museum helped with discussions on suitable experiments for children. Michael has also drawn cartoons for this and earlier editions.

Don and Marea Burke, producers, and the presenter of that most popular TV series, Burke’s Backyard, not only encouraged me to write features for their magazine, but allowed the reuse of that material in this book.

As an author I am conscious of the debt one owes to other writers and hope that I have dealt with this issue fairly. In over 40 years of activity in consumer chemistry, I have become a ‘gatekeeper’ for interesting snippets and extensions, many of which came from a regular radio talk-back show, ‘Dial-a-Scientist’, that I ran for several years on the ABC (Canberra), as well as the feedback from a regular column and features in the Canberra Times over many decades and from features in Burke’s Backyard magazine.

As a reader of New Scientist for around 50 years, I have enjoyed Daedalus and Last Word. Many titbits have entered this text over the years and I make a general acknowledgement where these are not individually recorded.

Acknowledgments for particular assistance and permissions are listed below.

CHAPTER 1

Dr Wal Stern suggested the content for the section on arson.

CHAPTER 3

Professor Ric Pashley, then of ANU currently at ADFA (UNSW) shared with me his common interest in surface chemistry, which helped to shape this chapter.

CHAPTER 4

The late Dr Peter Strasser was a mentor for the early editions of the book and provided the source material of the very first chapter ever written, ‘Chemistry in the laundry’.

The poem ‘Foam’ by A.P. Herbert, is reproduced by kind permission of A.P. Watt Ltd on behalf of Crystal Hale and Jocelyn Herbert.

CHAPTER 5

Professor Barbara Santich suggested items for inclusion in this chapter.

CHAPTER 6

Items suggested by Professor Barbara Santich and Dr David Topping also ended up in this chapter.

CHAPTER 8

Elizabeth Finkel AM PhD, Editor-In-Chief, Cosmos Magazine, gave permission for the extensive use I made of her article ‘Science skin-deep’ in Cosmos 19, 2008, pp. 64–69.

Particular thanks are due to Mr John Lambeth of Dragoco and Michael Edwards for their help with perfumes.

Ric Williams of the Australian Society of Cosmetic Chemists is thanked for access to some of his unpublished material.

CHAPTER 9

I am thankful for the efforts of Dr Jacqueline Poldy for discussion and comments on the contents of this chapter.

CHAPTER 10

Professor Tom Spurling gave me a succinct summary of the story of the Australian polypropylene polymer banknote– a story that needs wider exposure.

CHAPTER 11

Mikey Huson patiently took me through some of the intricacies of this vast and expanding field.

CHAPTER 12

Don Burke of Burke’s Backyard allowed use of material from that magazine.

Graham Stirling pointed me towards effective composting.

Raj Bhula from the APVMA is thanked for his comments on the use of agricultural chemicals in Australia, including comments for Appendix 4, MRL and ADI.

The interview with Mrs Willison on the discovery in Australia of fruit fly pheromones was done by Dr Tom Bellas.

CHAPTER 14

A number people made suggestions about the swimming pool including Dr Rod McDonald and Bob Selinger. Judy Bahar picked up a major chemical error from earlier editions.

CHAPTER 15

John Staton CEO of Dermatest Pty, Ltd, Australia spent many hours with me discussing the quite difficult topic of sunscreen performance measurements and meeting standards.

David Evans helped me with swimwear materials.

CHAPTER 17

Many useful discussions pertaining to the contents of this chapter were had with countless friends and colleagues. I am especially thankful for the attention given to this chapter by Frances Sargeant – a teacher at St Mary MacKillop College in Canberra.

CHAPTER 18

I am hugely appreciative of the time and effort offered by Mark Sonter, who was also the tutor for my earlier education on industrial radiochemistry.

Thanks to Robert Guilfoyle, ARPANSA, for mediating input comment from appropriate staff.

Thanks to Dr Chris Boreham, Geoscience Australia, for input on this chapter.

CHAPTER 19

Many decades of taking part in science teachers’ workshops has allowed me to obtain an appreciation to meet the needs of science teachers with their innovative spirits. Now lacking a laboratory meant adapting instructions for anyone with a kitchen.

About the authors

Ben Selinger AM is Emeritus Professor of Chemistry at the Australian National University and a Member of the Academy of Forensic Science, Fellow of the Royal Australian Chemical Institute and the Australian Academy of Technological Sciences and Engineering (retired). He has long been a powerful advocate of consumer awareness, protection and education. He has been a government chemical regulator, an expert court witness, and has set Australian standards for consumer products – all in the interests of making chemistry more accessible to discerning consumers. His roles have included:

•   Consumer representative on the Food Standards Committee, NHMRC, Commonwealth Department of Health, (1973–75).

•   Consumer standards committees of Standards Australia, chairing committees for the following standards: CS/11 (soaps), CS/2 (detergents), CS/42 (sunscreen agents), and served on CS/53 (sunglasses), CS/64 (solaria), CH/3 (paints) and FT/8 (plastics for food contact) (1973–1986).

•   Executive of Canberra Consumers Inc. (1974–79).

•   Board member, Council of the Australian Consumers’ Association (1980–86), (2000-2006).

•   Editorial panel member, Australian Academy of Science School Chemistry Project, Elements of chemistry: earth, air, fire and water (1980–81).

•   Advisory Council of CSIRO, observer (1983–84).

•   ACT Asbestos Advisory Committee, Chair (1983–86).

•   Commissioner for the ACT, National Health and Safety Commission, then Worksafe Australia, now Safework Australia, (1984–85).

•   Member, Advisory Committee to the Australian Government Analytical Laboratories (1986–1994).

•   Chair, ANZECC Independent Panel on Intractable Waste (1991–92).

•   Chair, ANZECC Scheduled Waste Working Group (1992–93).

•   Consultancy with Roger Randerson, Report to the Commonwealth Department of Health ‘Illicit Drug Manufacture in Australia’, 1993.

•   Consultancy, Report to ANZECC Hexachlorobenzene Waste (Orica at Botany, Sydney): Background and Issues paper, 1995.

•   Deputy Chair, ANZAAS, 1995–96.

•   Talk-back radio presenter, ‘Dial-a-Scientist’, ABC radio stations countrywide.

•   Foundation Chair, National Registration Authority for Agricultural and Veterinary Chemicals, now APVMA, (1993–1997).

•   Chair, Advisory Committee Australian Science Festival Ltd (2001–4).

•   Chair, Olympic Co-ordination Authority, community consultation committee, re: Homebush Bay Remediation of Contaminated Site for the Olympics, (1998-2000).

Russell Barrow holds an appointment as an Associate Professor at the Australian National University where he is a group leader in the Research School of Chemistry studying the organic chemistry of natural systems. He is a member of the American Chemical Society, the International Society of Chemical Ecology and the International Society for Ethnopharmacology. He also holds an adjunct position at the University of Goroka in Papua New Guinea. In addition to a PhD in organic chemistry, he is passionate about education and completed a Masters degree specialising in open and distance education. Russell has published over 60 scholarly articles and has 14 patents pertaining to his research.

His roles have included:

•   International Reader for the Australian Research Council (since 2004)

•   Assessor for the European Science Foundation (2012–2016)

•   Assessor for the World Academy of sciences (2011–2013)

•   Reviewer for International Journals including: Australian Journal of Chemistry, Journal of Agricultural and Food Chemistry, Journal of Ethnopharmacology, Journal of Natural Products, Organic Letters, Journal of Organic Chemistry and Bioorganic and Medicinal Chemistry Letters

•   Member of the Board of Senior Secondary Studies for Chemistry in the ACT (since 2004)

•   External PhD Assessor for: University of Auckland, New Zealand; University of Goroka, Papua New Guinea; University of Melbourne; University of Queensland; HuaZhong Agricultural University, China; Universidad Nacional Colombia, Colombia; Griffith University and Newcastle University

•   Director, 5th and 6th National Science Teachers Summer School (2003–2006)

•   ANU Director–Science Education Centre (Green Machine) (2003–2006)

•   Associate Dean (Faculty of Science) Marketing and Development (2005–2007)

In cross-referencing the chapters that follow, it became clear that a number of chemical concepts kept re-occurring. So for the consumer tourist, we believe that coming to grips with some of these is well worthwhile. We start by introducing the language of chemicals and their social life. Topics follow fast and furious: nomenclature, phases, solubility, hard and soft acids and bases, chemical speciation, chemical accountancy, chemical activity and free radicals.

The meaning of the word ‘chemistry’ has changed many times over the centuries. In the 3rd century of our common era, it referred to the fraudulent practice of imitating precious metals and stones (Greek khemeia). By the Middle Ages (~410–1453 CE), this practice had evolved into the quest for a substance that would actually transmute base metals into gold, and into the study of matter associated with this process, known as alchemy (from Arabic alkimia). In the 16th century, following the redirection of alchemy towards medicine by Paracelsus, the word came to mean the making of medicines. A dealer in medicinal drugs became a chemist. With Boyle’s critique of alchemical theory in his The Sceptical Chymist of 1661, ‘chemistry’, came to mean also the study of matter in a scientific manner.

Whereas sciences such as astronomy, biology, geology and physics continued to study the natural world, chemistry quickly went out to change it. While there are industrial offshoots from physical, biological and geological sciences, that is not their dominant theme.

Chemistry is involved in every aspect of our lives. In this book, we show how it keeps us safe. We see it in the laundry and the kitchen. Chemistry improves our sporting ability, makes eating safe and fun, provides cosmetics and keeps us safe in the sun. It helps us to improve our gardens and allows us to swim in our pools without getting infections. Chemistry provides plastics and metals to make all sorts of great consumer products, giving us a terrific range of fabrics and easy care clothes. We use chemistry when painting our house, building our homes, running our cars more efficiently and sustainably. It also provides the medicines to keep us healthy and living longer, productive lives.

Admittedly, it is not always positive news and there have been serious mistakes along the way. We do not avoid discussing these and hope your better understanding of the chemistry involved (by reading this book) will reduce them in the future.

Because of its dependence on raw materials and its provision of materials that are essential to other industries, the chemical industry plays a major part in world trade and a significant part in world politics. The various environmental debates have made chemistry even more central to political science.

SOCIAL AND CHEMICAL INTERACTIONS

If you were to define the social structure of a community, you would start by categorising the social interactions. Starting with the strong interactions, you find that they are fewer in number than the weak ones. A (nuclear) family unit has strong interactions, in the sense that the members of a family interact over long periods of time and the individuals influence each other mutually to a large degree. Families are generally relatively small units (2–12 members) and, initially at least, are highly localised. The next step up gives a choice of categories. For example, circles of close family, friends or the people at work. Then there is the club or the church group. The larger the group, the weaker the interactions. The categories are arbitrary, but some are more obvious and useful than others. They are never clear-cut and there are always questions at the edges. Is Uncle Joe, three times removed, family or close friend? Anyone who has made out a wedding invitation list knows the problem!

With chemical bonding, the same problem arises. With extreme examples (i.e. the ones always chosen to illustrate the point) everything is clear-cut. An isolated gaseous molecule of hydrogen chloride is like a couple on their honeymoon: a unique, unperturbed bond between a hydrogen and chlorine atom, oblivious to all other interaction. But when the molecule dissolves in water, the honeymoon is over and all the interactions change.

At last count, there are 118 elements known, but systematic chemistry deals with the family life of the 90-plus individual elements that have lifetimes long enough to allow them to be studied and used. The most basic categorisation in chemistry is the periodic table of the chemical elements. It is an icon of chemistry, credited to the Russian chemist Dmitri Mendeleev (1834–1907). The version shown in Fig. 1.1 is an alternative form of the table.

The chemical elements, in order of increasing relative atomic mass (much later corrected to atomic number), were found to exhibit periodic behaviour. This was one of early chemistry’s major achievements. In the periodic table, these systematic variations in the properties of the elements change slowly down a column and also along a row. We are no longer dealing with 90-plus individuals but with a system that allows extrapolation of the properties of one element from those of others.

Missing elements were defined according to their predicted properties, which were later confirmed when they were found. Additional elements at the end of the table had their properties extrapolated from within the table before their artificial production. The Periodic Table was a change as dramatic as switching from doing arithmetic with Roman numerals to doing it with Arabic numbers. Only much later was a rational basis for the periodic table provided by an understanding of the structure of the atom in terms of protons, neutrons and electrons. Now is a good time to listen to Tom Lehrer’s Song of the Elements.¹

Fig. 1.1. The periodic table of elements.

Source: https://en.wikipedia.org/wiki/Theodor_Benfey.

A chemical name must be unambiguous

The naming of chemicals can be confusing. Where purist chemists say ‘ethyne’, welders say ‘acetylene’. Linnaeus introduced the two-part nomenclature into Botany, such as Bellis perennis to describe a common daisy, and this approach was in turn adopted into systematic inorganic chemistry, thus magnesium sulfate for Epsom salts. In this book, we’ll stick to mainly talking about daisies but include a section on chemical nomenclature to aid those interested (see Appendix 1). Treat chemistry and its associated nomenclature like another language and recognise that it will take time to develop and master.

In order to have an unambiguous precise name for a chemical substance, a system has been devised to provide a systematic name that will allow us to describe any substance. These names are built up according to strict rules. Each compound has only one correct systematic name, but there is more than one system! The name conveys the complete information about the detailed structure of the compound: it is a stylised written description of the chemical structure. For example, ‘Aspro’, is a brand name; ‘aspirin’ or ‘acetylsalicylic acid’ is the generic term, and ‘2-(acetyloxy)benzoic acid’ is the IUPAC systematic name. To ensure that the chemical can be tracked down when required, each one is also given a sort of ‘tax file or social security number’ called a Chemical Abstract Service number CAS. The CAS number that number corresponds to 2-(acetyloxy)benzoic acid is 50–78–2. This is particularly important because chemicals appear under a variety of aliases – some more logical than others – but the CAS number links them all. The correct naming of chemicals is very complex and difficult even for professional chemists.

Chemical formulae and diagrams

Chemical formulae and diagrams are symbolic representations of the composition and structure of molecules and compounds. There are a variety of conventions for them, depending on the sort of information to be conveyed.

Level 1 information – empirical formula

At the lowest level of information is the empirical formula, which lists only the ratio of the different atoms present in the molecule and tells us nothing about the structure. For example, for acetic (ethanoic) acid, commonly known as vinegar when diluted with water, has the empirical formula CH2O.

Level 2 information – molecular formula

The molecular formula for acetic acid lists the actual number of different atoms in one molecule, rather than the empirical ratio. For acetic acid this is C2H4O2.

Level 3 information – group formula

The group formula places atoms together in groups that correspond to the grouping in the actual molecule and gives some indication (using prefix symbols) of how the groups fit together. For example, the group formula for acetic acid is CH3COOH. As you become more familiar with them, these group formulae can give a fairly complete (marginally ambiguous) description of the structure.

Level 4 information – condensed structural diagram

The condensed structural diagram, the most common form of line diagram, gives a two-dimensional representation of a three-dimensional structure. It leaves out a lot of the atoms, but their presence is implied by the shorthand conventions. For acetic acid, the condensed structural diagram is as shown in Fig. 1.2.

Fig. 1.2. Condensed structural diagram for acetic acid.

Level 5 information

The full structural diagram for acetic acid is shown in Fig. 1.3.

Fig. 1.3. Full structural diagram for acetic acid.

Note that each carbon atom, C, and hydrogen atom, H, is specifically depicted, whereas in the more usual, condensed version the carbon atoms are implied to be at the end and intersections of the bond lines and the hydrogen atoms are implied to fill positions so that the valence, which is 4 for carbon, is satisfied. Throughout the text, condensed structural diagrams will be used, but extra information will be included when required to emphasise a particular feature.

Level 6 information

The ball and stick model is useful to indicate the geometry and 3-dimensional nature of a molecule. This may be essential for explaining its biological activity. The ball and stick model for aspirin and benzoic acid are shown in Fig. 1.4.

Fig. 1.4. Ball and stick diagrams of benzoic acid and 2-(acetyloxy)benzoic acid.

MATTER UNDER INVESTIGATION

Matter is traditionally described as occurring in the solid, liquid and gaseous phases, but these three categories are not exclusive. Liquid crystals are materials that have ordered structure in one or two dimensions, in contrast to solids that are structured in three dimensions, and liquids, in none. Actually, this last statement is not strictly true either. Liquids do show some ordering and solids invariably have some disorder. Solids resist change in shape and volume, liquids resist change in volume but not shape, and gases resist change neither in shape nor volume.

When two phases of matter are in contact, the thing that separates them is a surface. Two liquid phases of oil and water will be separated by such a surface. This surface can be disrupted by a surfactant, allowing a form of mixing of the two liquids called an emulsion, with droplets of one liquid suspended in the other. The total surface separating the two liquids is now enormous. The shape of a solid is defined by the solid–air surface (see Chapter 3).

A fundamental question is, ‘What is matter and what holds it together?’ There are things we call atoms and molecules, elements and compounds. The elements are like letters representing different atoms. Just as letters form words, the atoms form molecules. Only certain orderings of letters form sensible words and only certain orderings of atoms form sensible molecules. What are the rules of sensibleness? Words are those combinations of letters that stay in the language long enough to be given a defined meaning.

Molecules are those combinations of atoms that stay around long enough to be worth defining a meaning for. Most molecules, like most words, are around for a long time. But aren’t molecules real? Are they just categories for sensibly dividing the world of matter into chunks suitable for human discourse, like words? If you have a molecule isolated in space, as, say, a gas molecule, then it is a very real category. But when it is part of a liquid or a solid, its isolated existence is often more a convenience than a reality.

As consumers, we are generally interested in the bulk properties of chemical substances, not their intimate microstructure and relationships.

SOLUBILITY

Ordinarily, when we say a substance is soluble, we mean that it dissolves to an appreciable extent in a solvent, which we usually assume to be water. However, we make everyday use of other solvents: dry-cleaning spirit to dissolve grease stains or turpentine to dissolve paints. The question of solubility in oils and fats is of great importance to the physiological action of, for example, pesticides and drugs, and the cleaning action of detergents. There is a simple rule that works well in predicting solubilities of substances in various solvents: like dissolves like. This means that ionic and highly polar covalent substances are usually soluble in polar solvents such as water, whereas covalent non-polar substances are soluble in non-polar solvents such as toluene, petrol and dry cleaning fluid.

Isopropanol, often called rubbing alcohol for its use in washing/disinfecting hands, is good at mixing with both water and grease and so it makes a handy additive in water for cleaning windows.

Although many substances do not dissolve in water or other solvents, it is often possible to produce a stable to semi-stable mixture or dispersion of solute and solvent. This process is called solubilisation. (The solute is what is dissolved; the solvent is what does the dissolving.) The resulting dispersion may be stabilised by the addition of another substance, such as a surfactant. Emulsions are an important group of these dispersions (see Chapter 4).

Solubility and sabotage

Have you ever heard that if you want to disable your enemy’s car, you should put sugar in the petrol tank? The legend goes that the sugar will dissolve in the petrol and when burnt, deposit carbon in the cylinders, wrecking the engine. However, chemistry busts this myth! Sugar is not soluble in petrol and will only dissolve harmlessly in the water at the bottom of the tank. Better find another method of sabotage!

WHAT KEEPS THINGS TOGETHER?

The manner in which atoms bond to each other in a molecule and the way they interact with other molecules determines in what solvent, and to what extent the substance will dissolve. This also influences which parts of the molecule stay together in the solvent and which separate. Some types of bonds that affect the solubility of molecules are ionic bonds, covalent bonds, polar molecules and non-polar molecules.

Ionic bonds

Common table salt consists of positive sodium ions and negative chlorine ions in a crystal lattice. When dissolved in water, the ions separate – the salt dissociates (ionises). There is not really an isolated molecule of sodium chloride (except perhaps in the vapour) but we tend to use this language loosely.

Covalent bonds

Acetic acid (a component of vinegar) is a covalent molecule where there are different bonds between atoms. In water, the acetic acid molecule partly dissociates (ionises) to release some hydrogen atoms as hydrogen ions (protons) into the water. With acetic acid, only ~4% of all the acetic acid molecules do this.

Polar molecules

A polar molecule has positive and negative sections; it is analogous to the north and south poles of a magnet. Water is a polar molecule and hence dissolves other polar molecules such as ionic solids (e.g. table salt).

Non-polar molecules

A non-polar molecule is uncharged. It will, therefore, dissolve in non-polar solvents. Oils are non-polar molecules and hence will dissolve other non-polar molecules

Liver makes toxins soluble

The liver converts many toxins that enter the blood into water-soluble forms so that the kidney can excrete them via the urine. One way it does this is by a process called glucuronidation, which simply means it joins a sugar called glucuronic acid on to the toxic molecule, which makes it polar enough to dissolve in water and be transported out of the body. For example, paracetamol is metabolised in the liver where an enzyme attaches a molecule of glucuronic acid, deactivating the pharmacological activity and allowing the new molecule to be excreted (Fig. 1.5).

Fig. 1.5. Glucuronidation of paracetamol.

Solubility at the sea

When you see a rock pool at the sea drying out, you probably think the white stuff crystallising out at the edge is the salt, sodium chloride. After all, the solids in sea water are ~96.5% NaCl, so it is not an unreasonable assumption. You just happen to be wrong!

If all the sea water is allowed to evaporate completely, the final solid will be ~0.5% carbonates, 3% gypsum (calcium sulfate) and the rest mostly sodium chloride. Sodium chloride constitutes 27.3 g/L of sea water while calcium sulfate is only 1.4 g/L (Fig. 1.6).

Fig. 1.6. The concentration of metal ions (Na, Mg, Ca, K) in sea water, as if they were salts.

Pretty in pink

What makes the new, fashionable pink salt so pretty? A little iron oxide rust (Fe2O3)? Or could it be from a cyanobacterium (blue-green algae) called Trichodesmium erythraeum found in strongly saline solutions? These algae produce a red pigment called haematochrome. The Red Sea is red for this reason.²

Source: Mara Zemgaliete/Adobe Stock.

EXPERIMENT

At the beach, try dropping some vinegar (which is also useful for treating jellyfish stings) on a sample of the white precipitate at the edge of a rock pool that still has lots of water. If you see gas bubbles being released into the water then the white precipitate is a carbonate. The gas bubbles contain carbon dioxide, a product of the reaction between the carbonate and vinegar. However, the amount of carbonate overall is very low so you may not get this result.

The solar evaporation industry uses the empirical Baume scale (Be°) as a measure of salt concentration. This is the general unit of measure for the density of industrial liquids. According to this scale, the salinity of sea water is ≈ 3.5 Be°, the crystallisation of CaCO3 begins at 4.6 Be° and that of CaSO4 at 13.2 Be°. NaCl crystallises at 25.7 Be° and the more soluble magnesium salts at 30 Be°.

Although magnesium is more abundant than calcium, it is also more soluble. In sea water, calcium is the only cation near saturation. Marine life would have difficulty in extracting calcium carbonate for shells if this were not the case.

As the Be scale suggests, when water evaporates from the sea water, the order of precipitation of salts is:

1. Carbonate: mainly calcium carbonate (calcite), but also calcium magnesium carbonate (dolomite).

2. Sulfate: calcium sulfate dihydrate (gypsum).

3. Sodium chloride: only when the volume of the sea water is down to ~10% of the original, will sodium chloride crystallise out.

4. Potassium and magnesium salts.

This process is called fractional crystallisation.

EXTRACTING MAGNESIUM

The concentration of magnesium ion in sea water is = 1.3 mg/L = 5.4 × 10−8 M.

The solubility product for Mg(OH)2 is Ksp = 1 × 10−11. It is much less soluble than Ca(OH)2 (Ksp = 4 × 10−6). Lime is, therefore, is added to (concentrated) sea water to ‘mine’ magnesium. Can you do the calculations?

Equilibrium and solubilities

Chemical equilibrium is an important concept. A consumer equivalent would be the way prices of houses move up and down in response to supply and demand. If demand increases prices go up; increase supply and prices go down. Chemical reactions with arrows going in both directions behave analogously (Eqn 1). You add a component on one side and this causes movement to the other side to reduce the effect of what you have done (Eqn 2). You take away a component from one side and the movement is to provide more to that side (Eqn 3). This concept is known as Le Chatelier’s principle.

A substance dissolving in a solvent is one example of a reaction moving towards equilibrium and that is reached when the solution becomes saturated (meaning it cannot dissolve any more substance). The solvent can take more or less substance depending on several factors, such as pH and temperature. It does get complicated!

Beware of stumbling over logs

pH is a measure of acidity (values usually range from 0 to 14). The more acidic, the lower the pH. A pH of 7 is neutral. The pH scale is one of many logarithmic scales used in science (see Appendix 3). It allows a huge range in a parameter– in this case, hydrogen ion concentration – to be compressed by expanding low values and compressing high values. pH can have negative values. All this is convenient, but can be misleading. You will find log scales and distortion in many sections of this book.

Back to the beach

If we now apply this equilibrium approach to carbon dioxide dissolving in water (including sea water), life becomes even more complicated. The reason is that, as well as the equilibrium between carbon dioxide gas in the air and carbon dioxide gas dissolved in the water, there are further equilibria between dissolved carbon dioxide and carbonic acid, between carbonic acid and bicarbonate, and between bicarbonate and carbonate (Fig. 1.7).

Fig. 1.7. Equilibria between carbon dioxide, carbonic acid, bicarbonate and carbonate.

Fig. 1.8. Components of universal indicator.

Source: James Kennedy, http://jameskennedymonash.wordpress.com/.

The pH of sea water varies from around 7.5 to 8.4 and ~ 90% of the dissolved carbon dioxide is present as bicarbonate (HCO3−). When more carbon dioxide is dissolved in the sea water, it initially generates more carbonic acid, thus lowering the pH and the equilibrium shifts converting more carbonate to bicarbonate. This can threaten marine organisms because their shells, which are composed of calcium carbonate, start to dissolve. In deep water, the pH drops to 7.5 and this increases the amount of solid carbonate dissolving. The pH of a solution such as sea water can be tested using, for example, universal indicator (Fig. 1.8).

Disappearing in the deep

Calcium carbonate shells tend to redissolve as they sink deeper into the ocean where it is cooler and the pH is lower, and this means we don’t find as many fossils in the raised sea beds of deep ancient oceans as expected.

On the other hand, at the surface, the pH of sea water can rise to as high as 8.4. This occurs because carbon dioxide is less soluble in warmer water and because carbon dioxide is also removed from surface water by photosynthesis of organisms living there. There is then a shift in equilibrium to carbonate. Even though the total carbon dioxide concentration in the water has dropped, the concentration of carbonate has increased and will be close to saturation if the pH is high.

This equilibrium is applicable to a wide range of situations. It is of direct relevance when discussing the effect of increasing carbon dioxide in the atmosphere in Chapter 17. It is found in Chapter 14 when discussing cloudiness caused by the precipitation of calcium carbonate. It is also involved in buffering the pH of blood in the body.

Henry’s Law is often mentioned in conjunction with this equilibrium but it is not applicable. Henry’s Law only applies if there are no further equilibria except for the gas/dissolved gas. Henry’s Law is applicable in Chapter 4 in regard to POPs circulating the globe.

Fizzy drinks

As a minimum, carbonated water has carbon dioxide dissolved in water and a pH of around 4.3–5.5. It is called soda water. It may be buffered with sodium bicarbonate. Or it might have potassium bicarbonate (mineral salt in which case it should be called potash water!). It might just have a bit of acid added, say citric acid (acidity regulator, food additive code 330) to keep the pH right. In each case, the same equilibrium diagram applies.

Figure 1.7 shows the equilibria involved when carbon dioxide is dissolved in water. Figure 1.9 shows how these equilibria shift when the pH is changed and how that affects the amount of each of the species present.

Fig. 1.9. For optimum carbonation, set the pH between 4.3 and 4.5.

Source: http://www.wetnewf.org/pdfs/measuring-alkalinity.html.

HARD AND SOFT CHEMISTRY

Would you believe, chemical elements choose some partners with whom they prefer to be combined? The theoretical justification of this chemical observation followed a long and painful path. Early important contributions can be seen in the 1940s. These advanced in the 1950s, and some aspects were publicised in the 1960s by double Nobel laureate Linus Pauling (Chemistry and Peace) in the 1960s. The ‘hard’ and ‘soft’ concept we are now going to explore was suggested by Pearson in 1963. It has been refined ever since, but, for a basic understanding, a time warp to 1963 works best.

The theory goes something like this. If the atom is large then its outer electrons can be easily pushed around and the label ‘soft’ is given to it. It helps if there aren’t too many electrons in the outside orbits. If the atom is small then the pushing around of outer electrons is more difficult. The label ‘hard’ is given. It helps if there are several electrons in the outside orbits.

Simplistically, hard atoms react with hard and form polar ionic bonds. Some electron transfer takes place between the atoms, which then take on positive and negative charges. The resulting compound is often water-soluble. Soft atoms react with soft and form non-polar covalent bonds. The positive and negative charges are separated by only a short distance. The resulting compound is often water insoluble.

Hard

By this definition, most of the common light metals such as sodium, calcium, magnesium, aluminium and titanium are hard. Non-metals such as oxygen and fluorine are hard. And by saying oxygen, we include groups in which the oxygen is the atom that touches the metal, so-called oxy-anions such as sulfate, carbonate, silicate, acetate and other organics. It is the oxygen atom that is actually doing the bonding with the metal.

Soft

Many heavy metals such as silver, lead, mercury and gold are soft. So are non-metals such as carbon, phosphorus, sulfur, bromine and iodine. And the electron on its own is considered to be the ultimate in softness.

Borderline

The metals iron, cobalt, nickel and copper are borderline. Iron(III), stripped of its outer electrons is hard but leaving one electron behind, to form iron(II), makes it softer.

The non-metals nitrogen and chlorine are borderline.

So, in nature and in preferred corrosion products, you tend to find sodium and calcium carbonates (but not sulfides), and silver and lead sulfides (but not carbonates) and all can form chlorides. You find iron(II) sulfide and iron(III) oxide. In fact, in soil, the conversion of the iron(II) sulfide to the iron(III) oxide when exposed to air releases sulfuric acid resulting in the environmental disaster called ‘acid sulfate soil’ (see below and Chapter 12).

CHEMICAL RELATIONSHIPS

Silver and sulfur are lovers

Silver metal is bright and shiny. It sits around in clean air and is unaffected by oxygen. However, even a whiff of sulfur, either in the air (from burnt fuels) or in a trace of protein in the sweat of the fingers or white of an egg, turns silver black. Silver sulfide has formed. Black silver sulfide is the bane of the host of a formal dinner party (Fig. 1.10).

Fig. 1.10. Tarnished cutlery.

Source: Jodie Johnson/Adobe Stock.

Gold is unreactive, right?

If silver tarnishes, why not gold? Gold is often found as the free metal that made it an object of value from the earliest of societies. Well, gold does react with sulfur just like silver, but it forms a single layer of tarnish invisible to the eye, which protects it from further attack (like aluminium oxide does for aluminium). The layer of sulfur on gold is actually very difficult to remove: it is held so tenaciously that it needs to be roasted off. The gold sulfur bond is actually due to van der Waals force and the compound is Au°S.

There is a tradition to paint liquid gold on porcelain and fire the decorated piece.³ How is the liquid gold prepared? Vegetable oils treated with sulfur act as a solvent for gold.⁴

Streets paved with gold

Interestingly, in the gold mining town of Kalgoorlie in Western Australia, mine waste was used for road building until it was realised that it contained significant quantities of a natural grey gold compound, gold telluride (AuTe2, calaverite). Gold had chosen tellurium, the relatively rare, big brother of sulfur, as its major chemical partner in nature. And it had done so enough to make the locals dig up the roads again to extract it.

And why do gold miners use cyanide to extract gold metal from crushed ore? Well, cyanide is a real softie and, as the rule predicts, reacts readily with metal softies, particularly gold.

Australia is one of the world’s biggest producers of sodium cyanide, NaCN, producing 160 000 tonnes per year, of which one-third is used locally for gold extraction. NaCN can extract as little as 1–2 g of gold per tonne of ore. It is transported as a 30% solution and the pH must be kept alkaline (pH 13) to prevent the release of hydrogen cyanide with a spill on acid soil. Sodium cyanide is very biodegradable, luckily. It is acutely poisonous, but without any long-term effects if you survive. Accidents are rare.⁵

Restoring old masters and their mistresses

The old masters – European painters from the 17th century or earlier – used a lead pigment in the paint used to create their pictures.⁶ Over the centuries, some of this has tarnished to black due to the formation of lead sulfide. Although lead prefers sulfur to oxygen, an overdose of oxygen in the form of hydrogen peroxide can restore old masters (as well as their pseudo-blonde mistresses), but not to the original pigment. The white regained is lead sulfate not carbonate, but both are white. In nature, lead is found mainly as a sulfide ore called galena.

Copper, on the other hand, attaches itself to oxygen to form an attractive green patina that is a mixture of copper oxide, hydroxide and carbonate. Copper also likes sulfur, but if oxygen is around it will react with this first. Common copper ores can be either sulfides such as chalcopyrite or carbonate related (e.g. the green mineral malachite). Iron(III) also prefers oxygen when it rusts to form several iron oxides. Iron (when valence II) is found as the sulfide, iron pyrite, or fool’s gold (Fig. 1.11). We can also make fool’s gold (or in this case, cook’s gold) in an experiment where vegetables high in sulfur are boiled to make soup and are covered with aluminium foil (see experiment ‘Preparing cook’s gold’ on p. 430).

Fig. 1.11. (Left) Malachite (CuCO3(OH)2) and (right) iron pyrite (FeS2).

Source: (left) michal812/Adobe Stock; (right) goldenangel/Adobe Stock.

The Earth’s geology – in one paragraph

When the Earth formed it was a bit like a modern steel blast furnace. Molten metals mixed and sunk to the bottom (centre of the Earth) and a slag floated to the top and solidified. Uplift formed mountains, and erosion then mucked the slag around. It is in that ‘slag’ that we find and mine our minerals.

Certain metals that liked sulfur ended up as sulfide ores. Others are found as oxides, carbonates, silicates and sulfates because in all of these it is the oxygen atom that is bonded to the metal.

SPECIATION AND OXIDATION NUMBER

We tend to stereotype cultures, nations and people, because classifying makes it easier to organise our feelings and responses. Meeting someone reminds us of someone else and they go into a preselected slot until otherwise proven. Chemicals are dealt with in much the same way. Practitioners are more careful in their judgments than the layperson, but we all tend to jump to conclusions. We both say things such as ‘chromium is carcinogenic’, but this statement needs further clarification. If ‘Mercury is a toxic heavy metal’, then what is all that mercury amalgam in our mouths doing to us? Amalgam is rarely used for dental fillings today and has been replaced by a range of plastic materials (see Chapter 16).

Before deciding whether a chemical has harmful properties, it is crucial to define exactly, to what degree the chemical has ‘access’ to an organism; in other words, how available is it, biologically?

Let us use an analogy – wealth. Assets come in a variety of forms that differ in their degree of availability: their liquidity. Cash, savings accounts and overdrafts are readily available. Term deposits are less so. Credit cards are perhaps too available. Listed shares are more available than unlisted instruments, and real estate lacks liquidity.

Chemicals are like money. In some forms and situations, they are easily mobilised, while in others they are not:

•   Sometimes copper comes out of water pipes and give you blue rings on the bathtub, causes diarrhoea and kills the goldfish. This can happen when pipes are new, without the protection