The viscosity of a liquid

The viscosity of a liquid (coefficient of internal friction of fluids) - a measure of resistance to fluid flow under the action of external forces, such as gravity).
Viscosity is the inverse yield of liquid depends on the nature of the liquid and decreases with increasing temperature. Usually in practice determine the ratio of viscosity of the liquid ETA to the viscosity of the water ETAon at the same temperature. The value of this ratio is called the relative viscosity and is denoted by nfrom.
The measurement of viscosity are produced by devices called viscometers. The simplest of them is viscometer Ostwald (Fig. 1) is U-shaped glass tube with two spherical extensions and capillary, soldered in one of the tribes. With the help of this device measures the time t, leak volume of the investigated liquid, concluded between labels 1 and 2, and time to leak the same volume of water. Relative viscosity of the liquid is calculated by the formula non=dt/do to where d and do- density investigated liquid and water at a temperature of experience.
In clinical laboratories determination of the relative viscosity of blood is produced using a special device (Fig. 2), comparing the distances that are promoted for the same time in two capillary tubes when creating weak vacuum identical on size the columns of blood and water, which occupies a similar starting position in the tubes. Promotion of liquids cease when the blood reaches the label i; on the label, which will move the water, determine the value of the relative viscosity of blood.
Relative viscosity of blood in norm fluctuates from 4 to 5.
Blood viscosity increases with hypertension, myocardial infarction, polycythemia , and others; viscosity decreases with anemia and of polyplasmia.