Rasayan Viscometer Cannon-Fenske, Size 50 - 400

The Cannon-Fenske viscometer is a widely used device for measuring the viscosity of liquids. The size you mentioned, 50-400, likely refers to the range of viscosities that this particular viscometer is designed to measure. In this case, it would be suitable for measuring viscosities ranging from 50 to 400 centistokes (cSt), which is a common unit for viscosity measurement. This range covers a variety of fluids, from relatively low viscosity liquids like water to more viscous substances like oils and polymers.