When your mom is going to a party, you'll have seen her spray on some expensive perfume. Why does she do this? What's the secret in the bottle?
What exactly is a perfume?
Let's take this in two parts. First we'll talk about what goes into a perfume. And then we'll see what effect it has on us.
What women put on is called a perfume, while men put on fragrances. What's the difference? Well, perfumes are mixtures of many chemicals (called notes), while fragrances are much simpler.
The chemicals used in a perfume or fragrance are called essential oils (better known as essence). All of these can evaporate very quickly when left open, and are generally gotten from the leaves or flowers of plants. For example, limonene is an essential oil that comes from lemon leaves and gives the familiar 'lemon' smell.
Essential oils for making perfumes are extremely expensive, and were among the things for which traders would go any length. They form a big part of Sinbad the Sailor's adventures. Of the three gifts the Magi gave the infant Christ, two were essential oils - myrrh and frankincense.
So how is a perfume made?
Most perfumes are made by mixing three kinds of essential oils. Scents that fade quickly are called top notes. They are light scents that fade quickly and give the first impression, like bergamot and citronella. Middle notes last for a few hours and provide the dominant scent of the perfume. Like rose, juniper or marjoram. Finally come the base notes, made of exotic material like anise, myrrh and frankincense. The last is a thick, gum like material extracted from Boswellia trees that grow in Yemen. The dried gum when powdered and mixed with charcoal is often used in incense and dhoop sticks.
Today, we know the chemical nature of these essential oils, and therefore they can be made in a chemical factory. When you mix up different oils, you can make a perfume that resembles the natural one. For example, a mixture that has geraniol, citronellol, phenylethyl alcohol and linalool in a ratio of 30:25:25:5 will smell just like roses!
Right. So what makes a perfume so great?
That's got to do with our sense of smell. This is the sense that makes us aware of the chemicals in our environment, and the brain marks them as good or bad smells. Chemicals that are bad for us (like ammonia or hydrogen sulphide) smell bad, so we avoid them. Chemicals that are good for us (like the natural chemicals of food) smell nice. That's why we walk away from a gutter and walk towards a nice smelling cup of coffee!
Our brains treat the smells from flowers and fruits as attractive, because it often implies that there is good food to be found with them. The brains of bees and butterflies think like that too, which is why they love being near flowers.
Long ago, someone (perhaps a lady) figured out that if you rubbed these leaves and flowers on yourself, other people would be attracted to you too. Later on, Arab chemists like Jabir ibn Hayyan and al-Kindi found that you could extract the essential oils from these flowers and leaves using alcohol or ether. And that started the perfume industry!
Let's make our own!
You'll need some pure alcohol (get your teacher to give you some), water and a few drops of lemon and orange essence. Mix alcohol and water in the ratio 70:30 and add five drops of lemon essence and five drops of orange essence. Pour the mix into an empty scent bottle, and spray some on yourself. You just made for yourself a light fragrance called eau-de-Cologne!