So those who have done the experiment, what did you find out?

When you bent the bone each day, did you realise that the bone is getting more and more flexible? This is because there is less calcium in the bone each day..

After 5 days -->

Titration Results and Explanation

What did you find out when doing the titration? Well, just in case you have not done it, we have gathered our results together for you to see. Here they are!

Day 1

Before the experiment

• Mass of bones: 23.59g
• All tissues and meat were removed as much as possible, so as not to interfere with the end results.
• Found out that only 20.20 cm³ of sodium hydroxide was needed to neutralize the ethanoic acid (through titration) before it was contaminated with calcium compound.

Beginning the experiment...

• Bones were soaked in ethanoic acid (4 mol/dm³)

Day 2

Experiment

• A fixed amount of ethanoic acid was taken out, and titrated to find out its concentration.
• Amount of sodium hydroxide needed to neutralize sample: 19.30 cm³

Day 3

Experiment

• The same amount of ethanoic acid was taken out, and titrated to find out its concentration.
  

  

• Amount of sodium hydroxide needed to neutralize sample: 19.40 cm³

Day 4

Experiment

• The same amount of ethanoic acid was taken out, and titrated to find out its concentration.
• Amount of sodium hydroxide needed to neutralize sample: 19.20 cm³

Day 5

Experiment

• The same amount of ethanoic acid was taken out, and titrated to find out its concentration.
• Amount of sodium hydroxide needed to neutralize sample: 19.40 cm³

End of experiment

Mass of bones: 20.92 g
Decrease in mass: 2.67 g
% of calcium compound: 11.318% (approx)

Conclusion and Explanation

• Titration done from the 2nd day onwards fluctuated between 19.20cm³ and 19.40cm³.
• 
• The calcium compound in the bone reacts with the ethanoic acid. On the second day, the concentration of the ethanoic acid is decreased.
• Hence, we can tell that after the second day, all the dissolvable matter in the bones has been dissolved.
• Conclusion was reached as the concentration of the ethanoic acid remained roughly the same after the second day.
  

Do you understand why we reached this conclusion? Let us explain a little.

From the graph, you can see that the amount of sodium hydroxide (which is an alkaline) used decreases after the first day and fluctuates between 19.20cm³ and 19.40cm³ for the next few days. (Fluctuating means that it goes up and down.)

This means that between the first and second day, the concentration of ethanoic acid (which is vinegar) has gone down. Why can we tell this? This is because we need less alkaline is needed to neutralise the ethanoic acid on the second day as compared to the first day.

Why does the concentration of ethanoic acid goes down? This is because the calcium compound in the bone reacts with the ethanoic acid, producing a new product (which is less acidic). Hence, as time goes on, the concentration of the acid goes down.

Then why does the graph fluctuates between 19.20cm³ and 19.40cm³ after the second day? Our theory is that all the calcium compound in the bone has already reacted with the acid by the second day. Hence, after the second day, there is no more reaction between the bone and the acid.

As a result, the concentration of the ethanoic acid remained roughly the same after the second day. This means that the concentration of the sodium hydroxide needed to neutralise the acid remained roughly the same after the second day. (Although the graph does goes up and down, the range 19.20cm³ and 19.40cm³ is actually quite a small range..) So, this is how we can tell that after the second day, all the dissolvable matter in the bones has been dissolved.

Hope you understand..

Now what if we try to put the bone in a solution containing calcium? Will the bone absorb calcium?? Why not try it out? Click on the 'right' button now!!

Decalcification - Objectives and Materials needed | Procedure | Results and Explanation

Calcification - Objectives, Materials needed and Procedure | Results and Explanation