Determination of Viscosity: Ostwald Viscometer Practical & PDF

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  1. Ostwald’s viscometer
  2. pyknometer
  3. stop watch
  4. pipette
  5. conical flask


  1. Distilled water
  2. Given liquid


The coefficient of viscosity of given liquid and water te and tw are time required to flow same volume of given liquid are water through capillary tube of same Oswald’s viscometer. dl and dw are there relative densities. They are determined by using pyknometer.

 nl         =  dl × t1

nw             dw ×tw

where, n1 = viscosity of liquid

            nw = viscosity of water

             tl  = time of flow of liquid

             tw = time flow of water

             d1 = density of liquid

             dw = density of water


    First of all, viscometer was taken and rinsed with water. It was filled with water from lower end of the tube but hot completely. The liquid was taken sucked up to upper bulb of tube; the level was kept stationary by holding with finger. The time taken by water to drop down from upper marked level to lower marked level was observed. The process was continued two or more times. The same process was carried out for given liquid and reading was noted.


S.N.SampleTime taken(sec)Mean time(sec)
  1.      water25     
water25   25.33
  2.      liquid26        

 Weight of empty pyknometer (w1) = 23.8057 g

Weight of pyknometer’s liquid (w2) = 34.0264 g

Weight of pyknometer’s water (w3) = 34.0647 g

Weight of liquid (m1)            = w2 – w1

                                               = 10.207 g

Weight of water (m2)             = w3 – w1

                                               = 10.259 g



     density of liquid = weight of liquid

                                     Weight of water

            dl   =    ml    10.227       = 0.9962  

                     dw        m2    10.259

The coefficient of viscosity of liquid

 nl = dl×tl   × nw

         dw × tw

      = 0.9926 × 26       × 9.03


      = 1.02 × 9.03

      9.2331 milliposes.                               


                          Thus the coefficient of viscosity of given liquid by using viscometer was determined to be 9.2331 milliposes. Hence, the coefficient of viscosity of given liquid can be determined by using viscometer.


  1. Reading should be noted carefully.
  2. The apparatus should be rinsed with water.
  3. After sucking the liquid up to upper bulb of tube, the level should be kept stationary by holding with fingers.
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