How to Find out the Rheochor value of the given organic liquid?

 

Experiment:

 

Find out the Rheochor value of the given organic liquid. Molar mass (or Molecular weight) of the given liquid is 46.


 

Theory:

Newton Friend showed that if molecular volume (or molar volume) of a liquid be multiplied by the eighth root of the coefficient of viscosity, it leads to a constant called rheochor., denoted by r.

 

                        R = (M/D ) h1/8

D is density of the liquid and M its molar volume

Rheochor may be regarded as the molar volume of a liquid at the temperature at which its viscosity is unit.

 

Apparatus:

 

Ostwald’s viscometer, stop-watch, specific gravity bottle, rubber tube, screw type pinch cock, iron stand etc.

 

Procedure:

 

·         Take an Ostwald’s viscometer and fix it in a stand in upright position.

·         Fix a small rubber tube to the limb with capillary tube to suck the liquid in.

·         Use the crew type pinch cock with rubber tube to control flow rate of the liquid.

·         Fill the viscometer with water to a level a bit lower than the mark B at the upper end of the capillary tube.

·         Suck the water through the rubber tube and allow the water to come above the mark A.

·         Allow the liquid to flow slowly and note the time to flow of water from mark A to mark B using a stop watch.

·         Repeat the experiment with the given liquid in the same way as for water.

·         Find the density of given liquid by using a specific gravity bottle.

It is advisable to take three readings of flow time for each liquid and then taking mean time to flow.

 

Observations:

Room temperature =      oC

 

Liquid

Time of flow (s)

Density (g.cm-3)

Water

 

 

Organic liquid

 

 

 

Weight of empty specific gravity bottle = W1 g

Weight of empty specific gravity bottle + water = W2 g

Weight of water = W2 - W1 = W3 g

Weight of specific gravity bottle + liquid 1 = W4 g

Weight of liquid = W4 – W1 = W5 g

 

Calculations:

 

Viscosity of given organic liquid can be calculated using following relationship:

 

h/hw  = (t1 / tw) x (dl / dw            and

R = (M/D) h1/8

  

 

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