This is about the inorganic salts used in tanning

2. A story that began long time
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3. A story that began long time
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7. PRESENTATION ON
INORGANIC SALTS USED FOR TANNING
CHROMIUM SALT, IT’S BEHAVIOUR IN
SOLUTION, OXIDATION RATE AND
COMPLEX FORM OF TRI VALENT TITANIUM

8. INORGANIC SALTS USED FOR:
 Tanning
 Curing
 Soaking
 Liming and Un-hairing
 Washing
 Deliming
Pickling
Chrome Tanning

9.  What is Chromium?
 Chromium Salts
 Oxidation Rate
 Behaviour of Chromium Salts in Different
Solutions
 Complex Form of Tri Valent Titanium
 Question and Answer Session

10. I C E B R E A K I N G . . . . . . . . .
A BRIEF IN BANGALI....

11. Phase -1

12. 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.

13. 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

14. 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.

15. 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.

16. 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.

17. Soaking
Sodium carbonate

18. 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

19. 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

20. 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

21. De-liming
Ammonium chloride

22. De-liming
sAumlfmatoenium

23. Bating & Drenching
No salts have used in this step. Dung is used in
this steps.

24. 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.

25. Pickling &
Degreasing
Sodium sulfate

26. 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.

27. Chrome
Tanning
Chromium sulfate

28. Phase - 2

29. Chromium:
* Symbol- Cr
* Atomic number- 24
* First Identified in 1797 in France
* Chromium exhibits a wide range of OS

30. 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

31. Chromium
Salts
Chromium acetate

32. Chromium
Salts
Sodium dichromate

33. Chromium
Salts
dPioctharsosmiuamte

34. 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

35. 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.

36. Behaviour of Cr Salt in Different
Solutions

37. 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

38. 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

39. 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