Viscosity of di-isodecylphthalate: a potential standard of moderate viscosity

The paper reports our first measurements of the viscosity of di-isodecylphthalate, which is a candidate for a reference material. At the same time it has a viscosity, which, at room temperature, is around 120 mPa · s, so that it can fulfill the need for a reference material more nearly matched to the needs of industry. The present measurements were carried out with a specially designed vibrating-wire viscometer over the temperature range 288–308 K and have an estimated uncertainty smaller than ±1.5%, following calibration against the viscosity of toluene. The instrument and results are presented here to encourage other measurements on the same material, by different techniques, which will lead eventually to the establishment of di-isodecylphthalate as a suitable reference material, as well as reference values for its viscosity

Viscosity measurements of liquid toluene at low temperatures using a dual vibrating-wire technique

A recently developed dual vibrating-wire technique has been used to perform viscosity measurements of liquid toluene in the temperature range 213 ?T?298 K, and at pressures up to approximately 20 MPa. The results were obtained by operating the vibrating-wire sensor in both forced and free decay modes. The estimated precision of the viscosity measurements, in either mode of operation, is ±0.5%, for temperatures above or equal to 273 K, increasing with decreasing temperature up to ±1% at 213 K. The corresponding overall uncertainty is estimated to be within ±1% and ±1.5%, respectively

Thermophysical property measurements: the journey from accuracy to fitness for purpose

Until the 1960s much of the experimental work on the thermophysical properties of fluids was devoted to the development of methods for the measurement of the properties of simple fluids under moderate temperatures and pressures. By the end of the 1960s a few methods had emerged that had both a rigorous mathematical description of the experimental method and technical innovation to render measurements precise enough to rigorously test theories of fluids for both gas and liquid phases. These studies demonstrated that, for the gas phase at least, the theories were exceedingly reliable and led to physical insight into simple molecular interactions. The thesis of this paper is, after those early successes, there has been a divergence of experimental effort from the earlier thrust and, in the future, there needs to be focus on in situ measurement of properties for process fluids. These arguments are based upon the balance between the uncertainty of the results and their utility and economic value as well as upon technical developments, which have provided reliable and robust sensors of properties. The benefits accrued from accurate measurements on a few materials to validate predictions of the physical properties, for a much wider set of mixtures over a wide range of conditions, are much less relevant for most engineering purposes. However, there remain some special areas of science where high accuracy measurements are an important goal