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New way of washing up

The Young Reporter (2005, December), 38(03), pp. 9.
Author: Kit Hung Kit-sum. Editor: Karie Lo Ka-wai.
Permanent URL - https://sys01.lib.hkbu.edu.hk/bujspa/purl.php?&did=bujspa0015563

Kit Hung Kit-sum

Dishwashing detergents can cause foaming and death of marine life. To help keep the Victoria Harbour nice and clean, a replacement product is being experimented.

Bile detergent was invented by three secondary students from South Tuen Mun Government Secondary School.

One of them, Chiu King-kei, said they were inspired by their Biology teacher who taught them animal bile emulsifies oil into small droplets.

It then occurred to the trio that bile could substitute regular detergents from supermarket shelves for washing dishes. They took fish bile as the key ingredient, then added lemon juice and water to remove the fishy smell and dilute the bile.

“The cost of bile detergent was cheaper than the normal one, as fish bile was obtained free from fish stalls,” said Chu Lai-ming, another member of the team.

The students conducted experiments to test their product's cleaning ability. “We put oil-soluble pigments on glass rods to act as oily dirt, then used ordinary cleansers and bile detergent to wash the glass rods respectively. We found they both had similar cleaning ability,” Mr Chiu said.

But as the product contains no preservatives, it would start to smell after three days of the storage.

The invention won the 2nd runner-up of the Hong Kong Student Science Project Competition 2000 organised by The Innovation and Technology Commission of the government. It was also one of the exhibits in the APEC Youth Science Festival International Science Exhibition 2000 held in Singapore.

Professor Chan Kin-shing from the Department of Chemistry of Chinese University of Hong Kong was impressed by the creativity and effort of the students, “no one has ever thought of using such natural materials (in this regard).”

Prof Chan noted, however, “chemical synthesized detergents are sulphate-based while bile detergent is carbonate-based. When coming across ‘hard water' which contains calcium or magnesium cations, carbonate-based products will form precipitates.”

The students said their experiments were limited by high school-standard equipment.

“We could neither extract bile salt from bile, nor kill the bacteria, which are the main source of the disgusting smell,” Chu Lai-ming said.

Edited by Karie Lo Ka-wai

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