Welcome to the NMMU Chemistry Department's Blog Site. May You learn from this blog and be inspired by it, after all 2011 is the International Year of Chemistry





Wednesday, February 23, 2011

Your elemental composition and a few interesting facts

Your body consists of about the following:
  • 65% Oxygen
  • 18% Carbon
  • 10% Hydrogen
  • 3% Nitrogen
  • 1.5% Calcium
  • 1% Phosphorous
  • 0.35% Potassium
  • 0.25% Sulfur
  • 0.15% Sodium
  • 0.15% Chlorine
  • 0.05% Magnesium
  • 0.0004% Iron
  • 0.00004% Iodine

There are obviously considerable variations from person to person. Ladies differ from men - for instance men are true iron men in that they contain 1.65 times as much iron as ladies.

Also, there are traces of other elements but the above list covers the major components.
The elements are combined in many, many forms.
That's what chemistry and biochemistry are about.

What would happen if you took this amount of each of these elements and mixed them - enough to simulate a 70 kg person?
Reactions would begin right away - quite likely causing heat. If you added a spark to this combination it would explode, then burn and smaller violent reactions would be seen.

Would it validate the "Big Bang Theory"?

Well, maybe on a smaller scale.
You certainly would not end up with a human! If you were patient and could wait a few million or billion years perhaps those mixed elements would evolve into some lifeforms. A nice thought, but I do not have the time. Still it would be fun to look at combining many of those elements and studying the reactions - putting equations to them - a topic that can be covered in future posts.

Now let's get back to the composition of humans:
Our bodies are a more delicate combination of these elements - lots of water, a good bit of protein, fat and bone. Sugars can be found  in our blood, as well as oxygen, carbon dioxide and many more compounds, all made of systematically arranged elements, or molecules, which are arranged in bigger groups such as cells, which again are arranged to create organs, which make up the physical form of mankind and other lifeforms.

Even the air in our lungs is part of our make-up - nitrogen and oxygen for the most part.
How much air do you contain? We would need to know your lung volume - if it is 5 liters then you have about 6 g of air (1.2g per liter x 5 liters) .

Of that about 21% or 1.26 g is oxygen. It seems so little. Think of the freedive world record holder, Herbert Nisch, who descended an incredible 214 m strait down into the ocean on a lung volume of about 12 liters (~3 g of oxygen). That is a 428 m round trip on 3 grams of oxygen - rather efficient, I would say. Yet we humans are terribly inefficient oxygen conservers compared to seals and other marine mammals.

So, physically, humans and animals, are complex combinations of elements. All the elements in the above list can be analysed for and many of their combinations (or molecules) can also be analysed using analytical instruments and other chemical means.
In recent years many simple instruments used to analyse such molecules have been developed - for example we could analyse Herbert Nisch's blood using a pulse oximiter (oxygen meter) just before he dives by clamping a small noninvasive device to his fingertip or earlobe - it reads the colour of his blood in time with his heartbeat - the redder the more oxygen, when he surfaces he is definitely close to passing out because he depleted a lot of that 3 g of oxygen that he took down with him. Now the clip-on oxygen meter would read a much lower level. The red colour readings must be made at a consistent time in his pulse cycle because with each heartbeat because the little capillaries in the fingertip or earlobe actually expand with each heartbeat and would give more red at the time of a pulse rather than after the pulse when they shrink.

On the topic of blood, the red colouration comes about from haemoglobin, the oxygen carrier that transports oxygen from the air to our bodies. If you train hard for an event, perhaps the Iron Man, or deep freediving as in Mr Nisch's case, the haemoglobin levels in your blood will change. They must, so as to cope with the hard work (oxygen starvation). Your body builds up more haemoglobin in the blood - that is one of the key parts of training for such an event. I do some freediving as a hobby. After extensive long duration dive sessions I find running to be extremely easy as compared to normal - it is surely related to the boost in my haemoglobin levels thus making oxygen transport efficient and the run becomes easy.

So chemistry is involved in getting fit too. So why not go do some chemistry on the sports field after work or school - you cannot escape it even if you try, so rather become more aware of how you do it...

One of my former Lecturers, Prof Peter Loyson, regularly suggested that we imagine that we have been shrunk down to molecular size and imagine what the molecules look like and how they interact with each other - we often used to laugh at this concept, yet strangely enough I find myself doing exactly that - trying to picture what is going on. You even see it shown in some movies these days - the film simulates an activity in the blood or muscles.

Hey! It is The International Year of Chemistry so why no try it out...

Imagine you are an observer in you blood stream, lung surface, or even inside an egg you are cooking.

What is going on in your internal organs and "plumbing"?


p.s. If you wish to see a lot more detail of what blood consists of click on the link.

Sunday, February 13, 2011

Elemental Analyses - Video Clip Showing Flame Colours

In the previous post promised I would explain how one can use flame colours for analysing elements.

Just as we all have finger prints, DNA, irises etc. that can be used to identify us, or to catch criminals, so each element has its own characteristics that we can use to track it down.
You saw the flame colours in the previous post - those are specific characteristics we can use to find out if an element is in a sample, be it beer, metal, or a carrot.

To analyze we would have to get some of the sample into a flame to free up the elements and allow them to emit their specific colour of light. In simple mixtures and pure compounds this method gives us a way to ID a few elements. In more complex cases we need the help of instruments.

When heated sufficiently most elements actually produce a range of colours and some colourless ultraviolet light. We can use devices such as prisms to separate the light and then use a very sensitive device to measure how much of each specific colour (or wavelength) of light there is in the flame(an the original sample).

There are many different types of instruments that use flames, microwaves, or even arcs, sparks or plasmas to make a cloud of atoms. In the iron and steel industry, for instance, there are arc instruments that make a continuous arc (similar to electrical welders). The arc vaporises some of the metal being analysed and it emits light according to its elemental makeup. In a short space of time the instrument separates the light using prisms or gratings and measures how much light there is of each colour or wavelength - from this information we can get a report of the amount of each metal or other elements that are in the sample being analysed. Its really quick - back in the old days it took perhaps a few days to get the same result using other chemical methods.

In our Analytical Chemistry Course students make use of many simple and complex instruments for analysing elements. Some of these instrument may cost as much as 1.5 million rands or even more depending on complexity and technology.
I asked my 3rd year analytical students to give a brief demo of how these flame colours can be used in analyses on a flame instrument. Its their first filmshow, Take #1
Let's see what they have to say...






Thanks for that Ludwe and Luzuko - not bad for the first attempt.

That instrument was a flame spectrometer with an air acetylene flame at about 2400 DegC into which they fed copper and strontium dissolved in water.

Next post I want to talk about Your elemental make-up.

Till next time,

Gletwyn

Friday, February 11, 2011

The International Year of Chemistry, and You

Welcome to this blog.
It is an honour as well as an exciting moment for me to type these words as this is the international year of chemistry. I have been formally in chemistry since the day I left school back in 1986, however, that spark which ignited this passion for chemistry flashed many years earlier, in about 1974.

Let me quickly tell a little story.

At the age of six my family gathered around the fire one November night under the Karoo sky. My dad ignited some fireworks, while we qualified to hold sparklers.
For myself and my twin brother this was pure delight. 
Soon the last firework was spent and my hopes dimmed from the exciting flashes and bangs.
From that moment on, the desire to see of these spectacular flashes once more burned with ever increasing brilliance and I turned excitedly to Encyclopaedia Britannica, my twin brother alongside. Farmer dad and ballet teacher mom could not help us much so we had to do it on our own. We did, the slow way. Many years, and hundreds of experiments later I created my own fireworks, rockets and tremendous bangs which far exceeded the normal home fireworks - this was in my seconds year of studies in Analytical Chemistry at the then PE Technikon in 1987.

Seemingly small events made big changes in my life and steered my interest. This happens to You too. I was fortunate to be taught by Padre Dixon at Union High school in Graaff Reinet - he was tremendously enthusiastic and was always doing chemistry and physics demos for us.

Unfortunately many schools are crippled by budgets that do not permit young potential scientists the opportunity to learn by seeing the thing they are learning about. I find this all the time when lecturing students and it saddens me.
What can be done about it? Occasional visits by university staff to schools are possible but there are many schools and time does not permit.

Being the International Year of Chemistry I thought it fit to begin to use the tools we have in this modern world to bring chemistry to you in the form of this blog site. It is called Chemistry and You for a good reason. Chemistry affects you and everyone else far more that we may realize.
My fellow staff and I am going to bring you a lot of chemistry in the form of short posts, pictures, video clips on Youtube (yes, you can see what we do in the labs). Also we will use social media such as Twitter and Facebook.

I am Dr Gletwyn Rubidge of the Nelson Mandela Metropolitan University, I look forward to making regular contact with you.


Now let us waste no time and get on with it...

I spoke about fireworks kindling my interest in chemistry.

You have surely all seen fireworks.

Ever wondered what makes them work - what makes the colours, the bangs, the smoke?

Colour in Fireworks:
I set off three 1000 foot flares at a new years party - as you can expect my 7 year old son loved it. One question he asked me was how does it get to be so bright red.
I explained that it is a type of gunpowder inside the flare that burns very hot (about 3000degC) and it has an element called strontium in it. The heat causes the atoms to become free - kind of floating about. Normally the atoms are bound to some other atom but at this temperature they are mostly separated from one another. In this free state the outer electron in the atoms can get excited and moves to a higher energy state. Kind of like you climbing up to a branch in a tree. When it calms down or relaxes it can release energy as light. Strontium can release red light as it relaxes back to the lower energy state.
Yes, you guessed it, that red light you see is from strontium added to the gunpowder in the flare.

Here I put some strontium into an air acetylene flame at about 2400 deg C - normally light blue like a gas stoves blue flame - the strontium makes the flame a strong red colour.




How do they make green?


Barium gives a light apple green colour.



Sodium gives an orange-yellow - the same colour you see in some of the street lamps such as in Target Kloof, PE.
Have you ever seen some water boil over from a pot onto a gas stove - the blue flame goes yellow. It is mostly sodium light you see in that flame.

Potassium yields a lilac colour.




Calcium forms a brick red colour





Copper forms a blue-green



In my next post I will cover how we can use these colours for analysing these elements and many more.