Determination of Rubber Hydrocarbon Content in Rubber Sole

This SOPs is intended for the determination of rubber hydrocarbon percent in all types of leather.


A weighed quantity of the material is extracted with acetone and alcohol and dried. It is then oxidized with oxidizing mixture and steam distilled. The distillate is titrated with standard sodium hydroxide.


  • Desiccators.
  • Oven  – 70 to 100°C
  • Distillation assembly with heating arrangement
  • Conical flask – 500 ml
  • Measuring cylinder 100 ml


  • Extraction solvent of acetone and methanol (1:1)
  • Chromic acid oxidation mixture – 250 ml
  • Sodium Hydroxide 0.1 N



  • Extract the test specimen approximately about 10 gm in a Soxhlet apparatus with extraction solvent of acetone and methanol for 2 hour at a rate of 6 cycles per hour.
  • Dry the extracted rubber specimen in an oven at a temperature of 70 to 100°C for one hour.
  • Pour 75 ml of chromic acid oxidation mixture in distillation flask and mark the outside of flask to indicate the liquid level.
  • Stopper the flask with cork fitted with a entry tube for steam, so that the acid mixture covers the end of the entry tube.
  • Lift the steam entry tube and insert approximately 1.0 g of extracted sample
  • Replace the steam tube and surround the distillation flask with by a boiling water bath and continue boiling for one hour.
  • At the end of this period, remove the water bath and start the flow of steam, heating the flask.
  • Continue distillation until about 500 ml of liquid is condensed in the receiver flask.
  • At the completion of distillation, remove the steam entry and stop heating.
  • Wash the delivery tube with water into the receiver.
  • If the temperature of the liquid in receiver flask is above 30°C, bring down the temperature below 30°C by using aeration assembly or cooling bath.
  • Finally titrate the contents with 0.1N sodium hydroxide using phenolphthalein indicator.

Make a blank determination using the same quantities of reagents and conditions of test.


  • Add neutral potassium iodide to the distillate after aeration and titrate any iodine liberated with neutral sodium thiosulphate.
  • Then continue the titration with 0.1 N sodium hydroxide solution.


Rubber Hydrocarbon, percent by mass =   0.908 x (V1 – V2) / M

V1 = volume in ml of sodium hydroxide consumed in titration.
V2 = volume in ml of sodium hydroxide consumed for blank determination.
M = mass in g of the test specimen taken

REFERANCE: – IS 6110:1983 appendix B – specification for double texture rubberized water proof fabrics.

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