Dilute Triton X-100 in water as a reference liquid for hydrometer calibration using Cuckow’s method

• New fluid for use as reference liquid for hydrometer calibration using Cuckow’s method.
• Advantages over traditional hydrocarbon fluids such as nonane and tridecane.
• Safer and less expensive.
• Density can be determined with sufficient accuracy from the mixing ratio.

We propose a 200 parts in 106 by volume solution of the surfactant Triton X-100 in water as a reference liquid for hydrometer calibration using Cuckow’s method. This liquid has advantages over traditional hydrocarbon fluids such as nonane and tridecane; it is safer, less expensive, and the density can be determined with sufficient accuracy from the mixing ratio. Previous researchers have used about 70 parts in 106 by volume Triton X-100 in water. Here we report measurements on the surface tension behaviour of aqueous Triton X-100 solutions with concentrations in the range (39–301) parts in 106 by volume. These measurements indicate that a 200 parts in 106 mixture is a suitable compromise between surface tension behaviour and accuracy of calculation of the liquid density from the mixing ratio of Triton X-100 to water. Performance tests to confirm the suitability of this liquid are given.