HÀ NỘI — Two ninth-grade students in the Cửu Long (Mekong) Delta province of Hậu Giang have invented an affordable device to assess the level of salt in water.
Lê Thị Hồng Gấm and Lê Phúc Hưng, students at Phan Văn Trị 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.
Lư Thị Huệ, a physics teacher who helped them make the tool, said the device sells for a price of VNĐ180,000 (US$8) and can be used for three years.
Trần Hoàng Anh, a farmer in Tư Sáng village of Tân Tiến Commune, said that he has used the device for six months.
“With this device, I can see if the balls sink or float, and then I know if there is salt. It helps me know when I can water plants,” Anh said.
Nguyễn Văn Đồng, director of the provincial Department of Agriculture and Rural Development, said that salt meters that sell for VNĐ1.3-20 million (US$ 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,” Đồng said.
“We plan to apply to the provincial Department of Science and Technology for a patent,” Huệ said. — VNS