Nine notable dyes, ancient and modern
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Tag Archives: Chemistry
Chemistry can be beautiful: the classic flame test
The flame test occasionally comes up in classic detective fiction: “He snapped off the lights, and we were left with only the sodium flame. In that green, sick glare a face floated close to mine – a corpse-face – livid, waxen, stamped with decay…” (Dorothy L. Sayers & Robert Eustace, The Documents in the Case)
Spectral lines in the image are taken from Kramida, A., Ralchenko, Yu., Reader, J., and NIST ASD Team (2019). NIST Atomic Spectra Database (ver. 5.7.1), [Online]. National Institute of Standards and Technology, Gaithersburg, MD. Photographs in the image are public domain, from Wikimedia Commons.
Alchemy
Sometimes the model is just wrong. Alchemists linked the metals to the planets (for example, because copper was mined on Cyprus, and that’s where Venus was born). They were incorrect.
Elements in the Human Body
Starting an element collection
In the spirit of the wonderful photobook The Elements by Theodore Gray (which I have previously blogged about), starting a collection of elements is a great way of introducing yourself (or your children) to basic chemistry. Here are some suggestions, and a list of 24 elements to start with….
2: Helium (He)
Helium is lighter than air, so balloons are often filled with helium.
6: Carbon (C)
Carbon is most easily added to your collection in the form of charcoal. Zinc–carbon batteries have a carbon rod at the centre.
7: Nitrogen (N)
Air is about 78% nitrogen. To add nitrogen to your collection, just fill a small bottle with air.
8: Oxygen (O)
Air is about 21% oxygen. To add oxygen to your collection, just fill a small bottle with air.
9: Fluorine (F)
Fluorine is a toxic gas. But octahedral fluorite crystals (calcium fluoride, CaF2) make a great addition to a collection.
11: Sodium (Na)
Sodium is a reactive metal which will spontaneously catch fire when in contact with water. But sodium chloride (ordinary table salt, NaCl) is perfectly safe.
12: Magnesium (Mg)
Magnesium is a flammable metal, but you can substitute crystals of Epsom salts (magnesium sulfate, MgSO4), which can be obtained from a pharmacy.
13: Aluminium (Al)
Aluminium (aluminum in the USA) is most easily available as aluminium foil.
14: Silicon (Si)
Silicon is widely used in transistors and integrated circuits (chips).
15: Phosphorus (P)
The side of a box of matches is largely composed of phosphorus.
16: Sulfur (S)
Sulfur powder, also called “flowers of sulfur,” is available from pharmacies.
17: Chlorine (Cl)
Chlorine is a toxic yellowish-green gas. But sodium chloride (ordinary table salt, NaCl) is perfectly safe.
20: Calcium (Ca)
Calcium is a reactive metal, but you can substitute crystals of calcite (calcium carbonate, CaCO3) or gypsum (calcium sulfate, CaSO4).
24: Chromium (Cr)
Chromium is used for plating (“chrome plating”) to prevent rusting. Also, “stainless steel” is between about 16% and 25% chromium.
26: Iron (Fe)
Iron is one of the most widely used metals. Iron nails are easy to add to your collection. Like nickel and cobalt, iron is attracted by a magnet.
28: Nickel (Ni)
The United States “nickel” coin is actually only 25% nickel (and 75% copper), but objects made of pure nickel can be found. Indeed, Canadian “nickel” coins from 1955–1981 are almost pure nickel.
29: Copper (Cu)
Copper pipes are widely used in plumbing. You can buy copper plumbing fittings, or get offcuts of pipe from a plumber. Copper electrical wire is also easy to find.
30: Zinc (Zn)
Galvanised iron is coated with zinc to prevent rusting. Also, filing off the copper coating on a US penny reveals a coin made mostly of zinc.
47: Silver (Ag)
A silver coin, or a piece of silver jewellery, would make a fine addition to your collection.
53: Iodine (I)
Iodine is a dark solid, but is sold in pharmacies as a brown solution in alcohol, called “tincture of iodine.”
60: Neodymium (Nd)
Neodymium is one of the “rare earth” elements. Neodymium magnets are the most common form of strong magnet. They are made of an alloy of neodymium, iron and boron (Nd2Fe14B).
74: Tungsten (W )
The filament in an incandescent light bulb is made from tungsten (but because of the danger of broken glass, only an adult should attempt to remove the filament, and then only with very great care).
79: Gold (Au)
A gold coin, or a piece of gold jewellery, would make a truly wonderful addition to your collection. Alternatively, for under $10, science museums will sell impressive-looking bottles of gold leaf floating in liquid.
82: Lead (Pb)
A fishing sinker is probably the easiest lead object to find.
So there you are. Those could be the first 24 elements in your collection!
Molecules: a book review
Molecules by Theodore Gray
I recently purchased Molecules: The Elements and the Architecture of Everything by Theodore Gray of periodictable.com (this is the sequel to his superb The Elements, which I have previously reviewed). The book is packed with interesting facts about chemistry as it relates to daily life, and the photographs are absolutely beautiful, as this two-page spread shows:
The structure of the book is necessarily a little ad-hoc, lacking the obvious pattern of The Elements. However, it is still well-organised, informative, and compelling. Everyone interested in science should probably have this one on the coffee table too.
I would give this book five stars, except that nothing could be quite as good as The Elements. I should also note that Theodore Gray’s Reactions is coming out soon. I expect that to be worthwhile as well.
Molecules by Theodore Gray: 4 stars
The wash bottle
Washbottles, old (left, photo: Hannes Grobe) and new (right).
Wash bottles, in one form or another, have been a long-term feature of the chemistry lab. Once they were made of glass, and were operated by blowing. In more recent times, plastic squeeze bottles have been used.
See here for more posts on scientific equipment.
Blue Jeans and Culture
An earlier post touched on the concept of “cultural appropriation.” This label is often applied inappropriately, because the world is more interconnected than most people realise. It has been that way for longer than most people realise (for example, some 4,000 years ago, tin from England was being traded across the Mediterranean sea for use in making bronze). And ideas go back further than most people realise.
As Michael Crichton says in his excellent novel Timeline, “Yet the truth was that the modern world was invented in the Middle Ages. Everything from the legal system, to nation-states, to reliance on technology, to the concept of romantic love had first been established in medieval times. These stockbrokers owed the very notion of the market economy to the Middle Ages. And if they didn’t know that, then they didn’t know the basic facts of who they were. Why they did what they did. Where they had come from.”
Consider blue jeans, for example.
Blue jeans are dyed with indigotin, a chemical derived from the indigo plant, which has long been grown in India. But before someone says “cultural appropriation from India,” indigotin was traditionally derived in Europe from the woad plant (northern Britons painted their skins blue with woad). In China, a different plant was used. Essentially, the use of indigotin was a cultural universal. In Germany, where a culture of excellence in organic chemistry grew up during the 19th century, a practical method for making synthetic indigotin was developed at the BASF company in 1897, and the choice of plant became moot.
A cake of indigo dye (photo: David Stroe)
Blue jeans are made from denim, a fabric named after Nîmes in France. During the California gold rush, Levi Strauss, a Jewish-American businessman of German origin, teamed up with Jacob Davis, a Jewish-American tailor of Latvian origin, to make denim work clothing for miners. These blue jeans were strengthened by metal rivets – an idea due to Davis, patented in 1873.
So which culture produced blue jeans – Indian? French? German? Latvian? Jewish? American? One can only say that blue jeans were produced by human culture.
Illustration from the patent application
A sample of elements
- Helium (He, element 2) – used in balloons, because it is lighter than air
- Carbon (C, element 6) – one of the key elements in living things
- Nitrogen (N, element 7) – makes up 78% of the atmosphere
- Oxygen (O, element 8) – makes up 21% of the atmosphere
- Aluminium (Al, element 13) – a light metal used to make saucepans and aeroplanes
- Silicon (Si, element 14) – used to make electronics
- Phosphorus (P, element 15) – used in elemental form on the side of matchboxes
- Sulfur (S, element 16) – a widely used element which occurs naturally in elemental form
- Titanium (Ti, element 22) – a light, strong metal
- Iron (Fe, element 26) – the most widely used metal (mixed with other elements it becomes steel)
- Copper (Cu, element 29) – a metal that has been used for about 10,000 years, named after the island of Cyprus
- Zinc (Zn, element 30) – used in batteries and to prevent corrosion
- Silver (Ag, element 47) – widely used in jewellery since ancient times (the symbol is from the Latin argentum)
- Tin (Sn, element 50) – about 5,000 years ago, tin (Latin stannum) was mixed with copper to produce bronze
- Iodine (I, element 53) – dissolved in alcohol, it is used as a disinfectant
- Gold (Au, element 79) – widely used in jewellery since ancient times (the symbol is from the Latin aurum)
For more on the elements, see the fantastic book The Elements by Theodore Gray of periodictable.com, which I have previously reviewed.
Chemical Compounds: the board game!
I have previously mentioned my strong interest in science / technology / engineering / mathematics education and in networks and in board games. This has prompted me to start designing educational games, such as the World Solar Challenge game. Joining the collection is my new Chemical Compounds game, which looks like this:
The online game store (faciliated by the wonderful people at The Game Crafter) has a free download link for the rules, should anyone wish to take a look. I also have a few other educational games there.
Scientific Gems 