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Inorganic salts used in Tanning of Hides or skin

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Inorganic salts used in Tanning of Hides or skin

  1. 1. A story that began long time ago…..
  2. 2. A story that began long time ago…..
  3. 3. A story that began long time ago…..
  4. 4. A story that began long time ago…..
  5. 5. PRESENTATION ON INORGANIC SALTS USED FOR TANNING CHROMIUM SALT, IT’S BEHAVIOUR IN SOLUTION, OXIDATION RATE AND COMPLEX FORM OF TRI VALENT TITANIUM
  6. 6. INORGANIC SALTS USED FOR:  Tanning  Curing  Soaking  Liming and Un-hairing  Washing  Deliming Pickling Chrome Tanning
  7. 7.  What is Chromium?  Chromium Salts  Oxidation Rate  Behaviour of Chromium Salts in Different Solutions  Complex Form of Tri Valent Titanium  Question and Answer Session
  8. 8. I C E B R E A K I N G . . . . . . . . . A BRIEF IN BANGALI....
  9. 9. Phase -1
  10. 10. Tanning The process of making leather from raw h/s. The word “Tanning” derives from “Tannin” an acidic chemical compound. It includes some primary and intermediate stages. In the stages different inorganic salts are used.
  11. 11. Curing  Curing means short time conservation of raw h/s as the decay of hides quality start as soon as flay completed.  It’s required to preserve the raw skin for short period.  In curing process we may follow one of these steps: Wet-salting Dry salting Drying Brining Freezing
  12. 12. Curing  The salts are used in curing is might be these types:  Vacuum salt: 99.9% pure and size less than 1 mm.  Granular salt: 99.9% pure and size is 2-4 mm.  Rock salt: Mined and crushed to the needed crystal dimensions.  Marine salt: Artificially prepared by evaporation process.  Khari salt: Strictly this material cannot be said as salt.
  13. 13. Curing Salt list is given below:  Sodium Chloride – NaCl  Sodium Carbonate - Na2CO3  Sodium penta chlorophenate - C6H5Cl5ONa  Sodium silicofluorides - Na2SiF6  Sodium sulfite - Na2SO3 Beside Naphthalene is also used in curing.
  14. 14. Soaking Restoration of natural swollen condition of hides and removal of dirt, soluble protein and curing agent is known as soaking. Actually it’s a process of rehydration. In soaking salts are used given below: Sodium carbonate - Na2CO3 Sodium Sulfide - Na2S Sodium Tetra-sulfide – Na2SO4 Amonia Containing salts Enzymes and detergent are also used in soaking process.
  15. 15. Soaking Sodium carbonate
  16. 16. Liming & Unhairing Treatment of soaked hides and skins with the milk of lime with or without addition of salts. In this process the liming chemicals also destroy the hair and epidermis layer completely. Thus the unhairing process end. Salts are used listed following:  Sodium Sulfide - Na2S  Sodium Hydrosulfide – NaHS
  17. 17. Washing Washing is the step to wash the half processed raw skins for the next method. For washing Sodium Meta-bisulphate is only used. As example: Sodium meta bisulfate - Na2S2O5
  18. 18. De-liming After liming the unhaired and fleshed hides and skins known as pelts, are taken for De-liming. During this step huge chemicals are used. Both salts and acids are frequently used in the step: Ammonium Chloride - NH4Cl Ammonium Sulfate - (NH4)2SO4 Ammonium Sulfa mate - (NH3)2SO3 Sodium Bisulfate - NaHSO4 Sodium bisalfite - NaHSO3 Calcium Borate - Ca3 (Bo3)2 Calcium Lactate - Ca(CH3CHOHCOO)2 Calcium Sulfate - CaSO4
  19. 19. De-liming Ammonium chloride
  20. 20. De-liming sAumlfmatoenium
  21. 21. Bating & Drenching No salts have used in this step. Dung is used in this steps.
  22. 22. Pickling & Degreasing The treatment of de-limed or bated pelts with a solution of acid and salt. It has done both in chrome and vegetable tanning. Salts for pickling is, Common salt – NaCl Sodium Sulfate – NaSO4 Sodium Formate - HCOONa Sodium Acetate – CH3COONa ** Degreasing doesn’t need any salt.
  23. 23. Pickling & Degreasing Sodium sulfate
  24. 24. Chrome Tanning This is the final status of a pelt when it becomes a leather. In chrome tanning following salts are used: * Tri-valent chromium salts * Sodium chloride –NaCl * Sodium sulfate - – NaSO4 * Chromium hydroxyl Sulfate * Chromium sulfate – CrSO4 * Sodium bicarbonate After tanning Sodium bicarbonate is used.
  25. 25. Chrome Tanning Chromium sulfate
  26. 26. Phase - 2
  27. 27. Chromium: * Symbol- Cr * Atomic number- 24 * First Identified in 1797 in France * Chromium exhibits a wide range of OS
  28. 28. Chromium Salts @ Most effective and efficient tanning agent. @ Mostly used safe III Chromium salts. @ Chromium salts used for tanning are: # Chromium sulfate # Chromium hydroxy sulfate # Chrome alum # Chromium acetate # Chromium chloride # Potassium dichromate # Sodium dichromate
  29. 29. Chromium Salts Chromium acetate
  30. 30. Chromium Salts Sodium dichromate
  31. 31. Chromium Salts dPioctharsosmiuamte
  32. 32. Oxidation Rate of Chromium Chromium is a D-Block metallic element and a reducing agent. The electronic configuration of Cr is: Cr(24) : Ar 3d5 4s1 Oxidation state of Chromium is: Cr(24) : -II –I 0 +I +II +III +IV +V +VI
  33. 33. Oxidation Rate of Chromium Chromium only shows negative electronic states, when it reacts with highly electro positive elements. The most stable states are +II +III and +VI. In this three oxidation states Chromium’s rate of reaction is higher than other oxidation states. Chromium forms compound in oxidation state +IV but as this stage is not stable, the compounds quickly deform and reform new compounds using it’s +II oxidation state.
  34. 34. Behaviour of Cr Salt in Different Solutions
  35. 35. Behaviour of Cr Salt in Acid Solution ACID SOLUTION OXIDATION STATE +VI +V +IV +III +II +I 0 2- +1.33 3+ 2+ Cr O 2 7 -0.91 Cr Cr Cr -0.41 +0.295 -0.74
  36. 36. Behaviour of Cr Salt in Basic Solution BASIC SOLUTION OXIDATION STATE +VI +V +IV +III +II +I 0 2- 3 Cr O 4 2 Cr(OH) Cr(OH) Cr -1.3
  37. 37. Complex Form of Tri Valent Titanium The +4 oxidation state dominates Ti chemistry but +3 state complex compound are also common. Such as: K2NaTiF6 K3 TiF6 – Potassium hexafluorotitanate NaTiF6 – Sodium hexafluorotitanate

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