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Measurement of factor of viscosity

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Device by means of which define viscosity is called viscositymeter. Set of methods of measurement of viscosity name viscositymetry. For movement of a liquid or gas through a tube some difference of pressure is required. Dependence between volume V of the liquid (gas) proceeding in time t through a tube in length L, and a difference of pressure on the ends of a tube is expressed by formula Puazal

Where r - radius of a tube, η - viscosity of a liquid or gas.

For definition of viscosity under the formula (1) it is necessary, that current was laminar, i.e. such at which layers of a liquid (gas) flow, not mixing up. For vortical (turbulent) current formula Puasal is wrong. That at usual speeds whirlwinds have not appeared, the tube should be enough thin.

The method is applied to liquids with low viscosity capillary viscositymeter, based on measurement of speed of current of a liquid in a capillary tube. This method is based on formula Puazal. From formula Puazal follows, that volumes of the liquids preceding for equal time intervals on identical capillaries, inversely proportional viscosity these liquids. Hence,

∆V/V = πr2L0/(πr2L) = L0/L=η/η0.

Now for definition of viscosity of blood Gess's viscositymeter with two capillaries is used. The device for definition of relative viscosity of blood consists of two graduated pipettes 1 and 2 with two identical capillaries 3 and 4 in the average part, strengthened on the general support 5. The ends of pipettes are connected by a tee 6 from which there is a rubber tube 7 with a glass tip 8. The pipette 2 has the crane 9. At measurements, having opened the crane 9 and involving a mouth air through a tip 8, fill a pipette 2 with water on a label 0. Then, having closed the crane, fill a pipette 1 with investigated blood up to the same level (all research should be made quickly that blood was not curtailed). Then open the crane 9 and, vigorously involving a mouth air, soak up liquids from both pipettes so that blood has reached a label 1. Thus water as less viscous liquid, will reach higher label which will specify relative viscosity of blood. The attitude of viscosity of blood and viscosity of water at the same temperature name relative viscosity of blood:

ηr= η/η0

 
Viscosity of blood of the person in norm of 4-5 m Pа sec, at a pathology viscosity is changed from 1,7-22,9 m Pа sec, that affects speed of subsidence erythrocyte. Change of viscosity of blood - one of the reasons of change of speed of subsidence erythrocyte. Viscosity of blood has diagnostic value. Some infectious diseases increase viscosity, others, for example a belly typhus and a tuberculosis, - reduce.

 
 
 
 
 
 
 
 

 


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