VietNamNet Bridge – Two ninth-grade students in the Cuu Long (Mekong) Delta province of Hau Giang have invented an affordable device to assess the level of salt in water.

Illustrative image (Source: VNA)

Le Thi Hong Gam and Le Phuc Hung, students at Phan Van Tri High School, say they applied Archimedes’ principle by using plastic balls pumped with a salt solution.

Based on the principle, when a solid is fully immersed in a liquid, it loses weight, which is equal to the weight of the liquid it displaces.

Experiments in labs showed that the plastic balls sank in pure water and floated on salt water.

After conducting experiments in rivers, the students developed a tool-kit of nine balls.

Lu Thi Hue, a physics teacher who helped them make the tool, said the device sells for a price of VND180,000 (US$8) and can be used for three years.

Tran Hoang Anh, a farmer in Tu Sang Village of Tan Tien Commune, said that he has used the device for six months.

“With this device, I can see if the balls sink or float, and then I know if there is salt. It helps me know when I can water plants,” Anh said.

Nguyen Van Dong, director of the provincial Department of Agriculture and Rural Development, said that salt meters that sell for VND1.3-20 million (US$ 58-890) are too expensive for farmers.

“The department highly appreciates the device, which is cheap and useful for farmers, especially now as there is high salinity in the Mekong Delta,” Dong said.

“We plan to apply to the provincial Department of Science and Technology for a patent,” Hue said.

VNS