Procedure

PROCEDURE

  • Place the balance on flat surface. Rotate the knob upon which the analytical balance rests to manipulate the mercury movement. Ensure that the mercury drop is within the circle, which indicates that balance is placed at symmetry. view video View Video
  • Weight the soxhlet receiving flask view video
  • Set the Soxhlet apparatus in position. view video
  • Weighing procedure view video
  • Take thimble and find out its weight. view video
  • Transfer about 5g of sample into the thimble and find out the correct weight of the sample by weighing the thimble with the sample.  View Video
  • Plug the mouth of the thimble with cotton wool, to avoid the escape of material from the thimble during extraction.
  • Slide the thimble with the contents into the Soxhlet extractor.  View Video
  • Fix the lower end of the Soxhlet extractor to the receiving flask underneath.  View Video
  • Fix the condenser above the soxhlet extractor. Take care to fix the ground surface suitable for easy removal after extraction. View Video
  • Adjust the water circulation for efficient and uniform cooling of the condensing unit. View Video 
  • The Soxhlet apparatus is placed over an electrical mandle/heater. From the top end of the apparatus pour about 100ml of petroleum ether and plug the mouth with cotton.  View Video
  • Run the extraction for 6 hours till the collecting ether in the extractor is clean.  View Video
  • Dismantle the apparatus on the completion of extraction. Remove the extractor with the flask from the condenser. ViewVideo
  • Remove the thimble with its contents. Place it in the oven for drying. When dried, find out the weight of the thimble with the extracted residue. View Video
  • Remove the Soxhlet receiving flask with the extract.  View Video
  • Transfer it to a hot air oven (80 ° C) for evaporating the petroleum ether.  View Video
  • Weighing procedure View Video
  • Weigh the flask with the dried residue.  View Video

Calculation

  • Weigh the ether extract either directly from weighing the flask with and without ether extract or indirectly by weighing the thimble with the substance before and after extraction.
  • The loss of weight in this case will give the value for ether extract.

Direct

  • Weight of empty flask = X
  • Weight of flask + Ether extract = Y
  • Weight of Ether extract = Y-X
  • W - Weight of feed sample

Direct- formula

Indirect

  • Weight of thimble + feed sample before extraction = X
  • Weight of thimble after extraction = Y
  • Weight of the Ether extract = X-Y
  • (Loss of weight represents the ether extract)
  • W - Weight of sample taken

Indirect - formula

Precaution

  • While placing the thimble-containing sample in the soxhlet flask, make sure that the top of the thimble is above the siphon tube.
  • Put a cotton swab on the mouth of the condenser to avoid the loss of ether vapour.

Note:

  • Preserve the ether-extracted material for crude fibre estimation.
  • Extraction period may vary from 4 hr at condensation rate of 5-6 drops/sec to 16 hr at 2-3 drops/sec.

Recently developed equipment for Ether extract

  • An equipment capable of extracting ether solubles in two stages has been developed recently.
  • The Samples to be analysed are weighed into thimbles and inserted into the Extraction Unit.
  • After solvent addition to the extraction cups, the soluble material is extracted first while the sample is submerged in the solvent, this is followed by a solvent recovery cycle. Because of the two stage of extraction, efficient heater and condenser unit, the extraction time is reduced.

Soxtec
Last modified: Saturday, 27 August 2011, 11:57 AM