All posts by jongngee01pd2014

What do fertilisers and gunpowder have in common?

During the summer holiday, my family and I visited a large cave in the Malaysia. The cave was a famous tourist attraction as there were thousands of bats living in the cave. As we walked along the elevated walkway in the cave, the guide began to talk about the history of the cave. He said that in the past, people used to collect guano in the cave. As he said that, the guide shined his flashlight on the cave floor, and I realised that I could not see it at all, as it was covered in a thick layer of bat feces. The guide then explained that people collected guano for fertiliser and even used it to make fireworks. After he said that, I thought why would people want to go all the way to a cave just to collect bat droppings for fertiliser, and how can bat droppings be used to make fireworks. When I returned to Shanghai, I decided to do some research to find out what chemical properties of guano made it such a valuable fertiliser and how could it be used to make fireworks.

Based on my research, I found that the reason why guano could be both a fertiliser and a component in explosive is because of the rich amounts of various nitrates (NO3)in it. Nitrates are polyatomic ions that have a trigonal planar structure, with the nitrogen atom as the central atom.
As mentioned earlier, guano was valued as an extremely efficient fertiliser because of the high amounts of nitrates in it. (Wikipedia). Nitrates contain nitrogen, which is an extremely important element for not only plant life but also other organisms as well because it is the main component of amino acids and nucleic acids, which is used to make DNA and other essential proteins. However, the element nitrogen itself cannot be broken down and used by plants as nitrogen molecules are held together by extremely strong triple bonds. Therefore, nitrogen has to be reduced into various nitrates. This is why nitrates have a negative charge to indicate a gain of electrons. Plants get these nitrates naturally from the soil. By adding fertilisers such as guano, the nitrate concentration of the soil increases, therefore increasing plant growth. These nitrates include potassium nitrate  KNO3   , sodium nitrate NaNO3 and others. However, though guano used to be mined and collected in the past, today these nitrates are produced synthetically. For example, potassium nitrate is produced when sodium nitrate and potassium chloride are reacted together in a decomposition reaction.

NaNO3 (aq) + KCl (aq) → NaCl (aq) + KNO3 (aq)

Sodium nitrate is produced in a acid-base reaction with nitric acid and soda ash

2 HNO3 + Na2CO3 → 2 NaNO3 + H2O + CO2

However, while fertilisers containing nitrates greatly promote agricultural growth, the excessive use of them has a negative impact on the environment. When the excess fertilsers get washed away into freshwater lakes and rivers, eutrophication occurs, in which there is an excessive growth of algae. The algae deplete the surrounding waters of oxygen, killing the marine life in it (Schindler, David, Vallentyne, Joh R, 2004).

As to the reason why guano is used to make fireworks, the answer is because nitrates are powerful oxidisers (Earl, 1978). Oxidisers are essential in explosives as it provides the oxygen needed to fuel the explosion (Earl, 1978). This is because as mentioned earlier nitrates are reduced fro nitrogen. As we have recently learnt, oxidizing agents are often the ones that had been reduced. Nitrates are often used as oxidisers because of the energy released from the triple bonds of nitrogen.

From my research on guano I realised how chemistry can be used to benefit and harm society. Using chemistry to isolate and mass produce nitrates in synthetic fertilsers from guano boosts agricultural production. However, these fertisers pollute the environment. Understanding the chemical properties of nitrates lead to the development of powerful explosives that can be used for peaceful purposes such as mining or harmful purposes such as terrorism. In conclusion, knowledge in chemistry can be used to benefit our lives and also identify potential threats.

Reference

Earl, Brian (1978), Cornish Explosives, Cornwall: The Trevithick Society

Schindler, David and Vallentyne, John R. (2004) Over fertilization of the World’s Freshwaters and Estuaries, University of Alberta Press

http://en.wikipedia.org/wiki/Guano

Ionised water = The new snake oil

During Chinese New Year, my family and I went back to Malaysia to visit my relatives. We visited one of my aunts had undergone surgery to remove a small cancerous growth. Besides ensuring us that she would make a complete recovery soon, my aunt also told her plan of improving her health. Part of that plan involved the purchase of a water-ionizer machine. When we asked her what was the function of the water-ionizer, my aunt told us that she purchased the machine after seeing it on a television advertisement. The advertisement claimed that when the body becomes “too acidic”, it encourages the growth of cancer cells and other diseases such as obesity. The solution to this problem would be the water-ionizer. The advertisement claimed that the water-ionizer would ionize drinking water using electrolysis, producing “alkaline water” and “acidic water”. By drinking the alkaline water, the advertisement claims that the alkalinity would reduce the acidity of the body. The advertisement also claimed that the water acts as an anti-oxidant. (Snyder et al., 2008)

Convinced by my aunt, my parents bought a water-ionizer to ring back to Shanghai. At first, I myself had no doubts about the “benefits” of the water-ionizer. When we started our unit on acids and bases, I decided to see if the water-ionizer was really beneficial. To my dismay, the many claims that the water-ionizer company made were scientifically wrong.

Many water-ionization companies claim that by drinking alkaline water, it will neutralize the acidity of the body. Firstly, the intake of alkaline water does not affect the ph of the body. If alkaline water is drunk, the acids in the stomach will neutralize the basic nature of the alkaline water. The body has its own system of regulating the ph levels of the various parts of the body, such as blood and urine. For example, in the blood, the bicarbonate buffering system keep’s the blood’s ph at a constant level.

CO2 (g) + H20 (l) <=> H2CO3 (aq) <=> H+ (aq) + HCO3- (aq) (Frey et al., 2008)

The CO2 in the blood , when mixed with water, produces carbonic acid. The carbonic acid in turn can disintegrate into hydrogen ions and the basic bicarbonate. Hence, drinking alkaline water has no effect in changing the body’s ph level.

“Ionized water” is a misleading term. In chemistry, pure water has a neutral ph of 7, meaning that there are no ions in pure water. Water that is not pure water, such as rainwater, is already ionic, since they contain ions present in it, such as Sodium. Therefore, the term “ionized water” does not describe anything.

Secondly, the water-ionizer is supposed to turn water into alkaline water by “ionizing” the water through electrolysis. However, significant electrolysis cannot occur in pure water due to the lack of ions. The water-ionizer is a machine with 2 metal plates that are normally made out of inert metals such as stainless steel, separated by a membrane. They serve as electrodes, which are electrical conductors that conduct electricity to a non-metallic part of a circuit, in this case, the water. When connected to the power source, one of the plates becomes negatively charged while the other becomes positively charged. (Lower et al., 2008)

The negatively charged plate releases electrons. Hydrogen ions than bond to these electrons to produce hydrogen gas and OH-

2 H2O(l) + 2e → H2(g) + 2 OH(aq)

Based on Bronsted-lowry theory, the excess OH- ions make that side of the machine alkaline.

and the positively charged plate, oxidation takes place, producing oxygen gas.

2 H2O(l) → O2(g) + 4 H+(aq) + 4e-

Based on Bronsted-lowry theory, the excess H+ ions make that side of the machine acidic.

However, the H+ and OH- ions eventually recombine to form water, and the final equation reveals that the final product is hydrogen and oxygen gas, which does not affect ph.

2 H2O(l) → 2 H2(g) + O2(g)

Therefore, significant electrolysis can only occur when the water is ionic. However, most tap water is alkaline in order to prevent the disintegration of water pipes. Slightly acidic water, such as water from mountain glaciers and streams, is safe to drink. (Dunning et al., 2009)

Lastly, I also found out that the claim that cancer cells grow better in acidic environment is actually a misinterpretation of the fact that cancer cells release acids.  (Mathani et al., 2010)

So, what were the implications of this research? I believed that this research was very important. By understanding the complete process of the electrolysis of water, I was able to see that the water-ionizer’s claim of being able to raise the ph of pure water was false. I was also able to realise that the misuse of Bronstend-Lewis law could be used as convincing ways to trick people. Most importantly, this research shows that many health products will not only misinterpret and misuse scientific data to give their claims false credibility. This research also highlights the practicality of studying chemistry, since a basic understanding of chemistry can helps us deduce whether these claims are false. In conclusion, I feel that this research warned me to guard myself against false scientific claims and to apply my previous knowledge in chemistry to real world settings.

References:

Dunning, B. (2009). Kangen Water: Change Your Water, Change Your Life. Skeptoid: Critical Analysis Podcast. Retrieved March 14, 2013, from http://skeptoid.com/episodes/4139

Lower, S. (2012, November 20). “Ionized” and alkaline water: snake oil on tap. “Ionized” and alkaline water. Retrieved March 14, 2013, from http://www.chem1.com/CQ/ionbunk.html

Mahtani, R. L. (2010, August 15). Acid Balance in the Body and Cancer – Caring4Cancer. caring4cancer. Retrieved March 14, 2013, from https://www.caring4cancer.com/go/cancer/nutrition/questions/acid-balance-in-the-body-and-cancer.htm

Snyderhealth (n.d.). cannotParse. snyderhealth. Retrieved March 14, 2013, from http://www.snyderhealth.com/water_ionizers/how_does_a_water_ionizer_work.html

University of Washington (n.d.). pH Buffers in the Blood. Department of Chemistry | Washington University in St. Louis. Retrieved March 14, 2013, from http://www.chemistry.wustl.edu/~edudev/LabTutorials/Buf