leather testing

1. sampling
2. fat content in raw
3. fat content and free fatty acid in pickle & wet blue
4. chrome content Cr2O3 in leather and in liquor
5. Ash content
6. precipitation resistance
7.fluxing endurance
8.ball burst test
9. rub fastness (wet)
10. rub fastness dry Leather testing method
Determination of water content
Water content in % = G1 – G2 /G1 *100
G1 = weight of sample before drying
G2 = weight of sample after drying
Determination of substance extractable with dichloromethane
Fats and other soluble substances
Extractable substance in %= g extract *100/g weight of sample
Determination of soluble substances removable by washing
Total loss by washing in %= g solid *100/ g weight of sample
Sulfate ash removable by washing in % =g sulfated residue on ignition *100/ g weight of sample
Organic substances removable by washing in % = difference between total loss by washing and sulfated ash removable by washing
Determination of ash
Total ash in % g total sulfated ash */ g weight of sample
Water- insoluble ash in % (determination by calculation) = % total sulfated ash minus % sulfated ash removable by washing.

Determination of chrome

a. Iodometric determination of chrome

1. ml 0.1 N Na-thiosulfate solution =^ 1.734 mg Cr

1. ml 0.1 N Na-thiosulfate solution =^ 2.534 mg Cr₂O₃

Titration with iron sulfate solution

1. ml 0.1 N Iron (II)sulfate solution =^ 1.734 mg Cr

2. 1. ml 0.1 N Iron (II)sulfate solution =^ 2.534 mg Cr₂O₃

Determination of water-soluble magnesium salts

(Epsom salt)% MgSo4 * 7 H₂O = ml 0.01 m komplexonIII solution / g weight of sample ^*0.2465

Determination of total nitrogen content, content of ammonium salts, calculation of skin substance

a. % Total nitrogen

1ml 0.5 N H₂ So₄ =^ 7 mg nitrogen

b. Ammonium nitrogen

1ml 0.5 N H₂ So₄ =^ 1.4 mg nitrogen

Ammonium sulfate content in mg (NH4)₂SO4= mgN* 4.71

Difference value
The difference value is the difference between pH of a solution and that of its 1:10 dilution.
Fixed tannin (vegetable)
% fixed tannin =100 minus the sum of moisture, fat, ash organic loss by washing and skin substance.
Degree of tanning (vegetable)
The degree of tanning indicates the number of parts of tannin fixed by 100 parts of skin substance.
Degree of tannin = % fixed tannin /% skin substance*100