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The Chemistry of the Smell of Toilets & Human Waste. Click to enlarge Today’s post marks a slight detour for the aroma chemistry series.

The Chemistry of the Smell of Toilets & Human Waste

So far, we’ve look mainly at pleasant aromas, but today we turn to a major malodour: that of toilets, and, more specifically, human waste. It might seem like something of a childish subject, but there are some interesting chemical compounds present in the materials we expel from our bodies. There are are also reasons to examine these compounds, as we’ll discover. First, we should briefly discuss what makes up faeces and urine. What is it, then, that makes human waste smell? A variety of fatty acids have been detected in the odour of human faeces; the major one of these is ethanoic (acetic) acid, which of course is more commonly known as vinegar.

Whilst the fatty acids may have the higher concentrations, what’s more important when it comes to smell is a compound’s ‘odour threshold’. Other nitrogen-containing compounds are found in urine. Enjoyed this post & graphic? References & Further Reading Like this: The Chemical Compounds Behind the Smell of Flowers. Click to enlarge With Valentine’s Day upcoming, part of your Valentine’s plan may well involve sending flowers.

The Chemical Compounds Behind the Smell of Flowers

These come in an array of different colours, and also have a range of different scents. What are the chemical compounds behind these scents? That’s the question that this graphic tries to answer, with a more detailed discussion of each below. Firstly, it’s important to realise that aroma chemistry is complex, and the smell of any flower is never really the consequence of a single chemical compound. Roses Roses are by far and away the most popular choice of flower for Valentine’s Day – and by association, the most expensive! Another compound that contributes to the scent of roses is beta-damascenone. Other compounds that make minor contributions to the aroma include geraniol, nerol, (-)-citronellol, farnesol, and linalool. Carnations Carnations, too, are a common component of floral bouquets. Violets Lilies Lilies are flowers more commonly associated with funerals in some countries. The Chemical Compounds Behind the Aroma of Coffee.

Click to enlarge Whether you’re a coffee connoisseur or completely unfussy about the manner in which you get your caffeine fix, there’s no denying that the smell of freshly-brewed coffee in the morning is an invigorating one.

The Chemical Compounds Behind the Aroma of Coffee

The chemistry behind this aroma, though, is far from simple; a complex collection of chemical compounds are responsible, and this graphic takes a look at a selection of these. We’ve taken a look at chemical compounds found in coffee beans previously, but then we were primarily concerned with what causes the bitter notes in the flavour of coffee, as well as looking at some of the more obvious compounds present, such as caffeine. The Aroma of Christmas Trees.

Click to enlarge The aroma of pine trees is one that’s evocative of Christmas; one of the responsible molecules, alpha-pinene, has already been featured on the Chemistry Advent Calendar, but here we take a more detailed look at the chemical constituents of the aroma.

The Aroma of Christmas Trees

One of the most important contributors to the Christmas tree aroma is pinene. Pinene is a compound which occurs naturally as two different isomers: Alpha-pinene, and beta-pinene. The Chemistry of the Odour of Decomposition. Click to Enlarge.

The Chemistry of the Odour of Decomposition

The Chemical Compounds Behind The Smell Of Rain. The Chemical Compounds Behind the Scent of the Sea. The summer holidays are here, which means there’ll soon be crowds flocking to the coast to spend the day at the beach.

The Chemical Compounds Behind the Scent of the Sea

The supposed benefits of ‘fresh sea air’ are commonly extolled, but its origins might not be what you think: it’s the chemical compounds produced by algae and seaweed that contribute towards its characteristic smell. Seaweed is one of the more obvious sources of malodorous compounds. It’s commonly seen washed up on the fringes of the sea, and as it decomposes, it can produce gases that contribute to the ‘sea smell’. The principle gas produced is hydrogen sulfide, which is generated via the bacterial breakdown of organic compounds in the seaweed.

Hydrogen sulfide has an odour commonly described as akin to rotting eggs, and is actually a toxic gas in high concentrations. However, before you start sprinting in terror from seaweed on all future vacations, it’s worth pointing out that, at low concentrations, hydrogen sulfide is harmless. Finally, is sea air good for you? The Chemicals Behind the ‘New Car Smell’ Click to enlarge This graphic comes off the back of a number of requests for it to be added to the ‘Aroma Chemistry’ series.

The Chemicals Behind the ‘New Car Smell’

What Causes the Smell of New & Old Books? Everyone’s familiar with the smell of old books, the weirdly intoxicating scent that haunts libraries and second-hand book stores.

What Causes the Smell of New & Old Books?

Similarly, who doesn’t enjoy riffling through the pages of a newly purchased book and breathing in the crisp aroma of new paper and freshly printed ink? As with all aromas, the origins can be traced back to a number of chemical constituents, so we can examine the processes and compounds that can contribute to both. As far as the smell of new books goes, it’s actually quite difficult to pinpoint specific compounds, for a number of reasons. Firstly, there seems to be a scarcity of scientific research that’s been carried out on the subject – to be fair, it’s understandable why it might not exactly be high up on the priority list.

Secondly, the variation in the chemicals used to manufacture books also means that it’s an aroma that will vary from book to book. What Causes The Smell of Fresh-Cut Grass? The second in the ‘Aroma Chemistry’ series, this graphic examines the smell of fresh-cut grass.

What Causes The Smell of Fresh-Cut Grass?

This is oft-mentioned when discussions of favourite smells come up, so what are the chemical compounds behind it? Grass emits volatile organic compounds normally, even without being cut. Research has shown that the amount of the compounds emitted can vary depending on light intensity and temperature.