The analysis of the chemical composition of tissue samples from living organisms and samples taken from Earth’s crust reveals that all elements present in both these samples have a great similarity. The only striking difference can be observed in their relative abundance in both these samples. For example, the living tissue contains a very high amount of carbon, oxygen and nitrogen in compare to Earth crust. On the other hand, Earth’s crust possesses a very high amount of sodium, calcium, magnesium and silicon. This difference might be due to the type or nature of chemical reactions suitable under the environment of a living being or the environment of Earth’s crust.
Further, the elemental analysis of living tissue gives the composition of inorganic elements in the form of oxygen, hydrogen, carbon etc. to do this experiment, first, the small amount of living tissues is isolated for the study. The tissues are living; hence they contain a large amount of water. This called fresh weight. The water is evaporated by using a higher temperature. This gives the dry weight of tissue. This dry tissue is now burnt completely using very high temperature. This results in the oxidation of organic compounds (released in the atmosphere in gaseous form) and the formation of ‘ash’. The ash contains many inorganic elements like magnesium, calcium, sodium, potassium, chlorine etc.
Percent weight of human body formed by various elements are as follows; - Oxygen (65%)
- Carbon (18.5%)
- Nitrogen (3.3%)
- Calcium (1.5%)
- Hydrogen (0.5%)
- Sulphur (0.3%)
- Sodium (0.2%)
- Magnesium (0.1%).