ANN 111: Principles of Animal Nutrition and Feed Technology (2+1)

PROCEDURE

• Step-1. The total ash obtained in the preceding experiment is placed over the heater. Click  here to view video
• With the use of water from wash bottle, gently wet the ash. (Take care not to blow out the ash while using the jet of water.)
• Dilute acids are added to dissolve all the minerals.For this purpose Hcl (1+ 3) and HNO₃ (1+ 3) are used.
• Step-2. Add first, drop-by-drop Hcl (1+3) with the help of a glass tube. The soluble ash will get dissolved with effervescence. Continue addition till effervescence stops. Click here to view video
• Step-3. Now add few drops (5 to 10 drops) of HNO₃ (1+ 3). This completes the solubility of the minerals and brings all the minerals into soluble form.  Click here to view video
• Warm the content, taking care to avoid spurting of the contents due to excessive boiling. Let the contents boil for few minutes and allow it to cool.
• By the time, get a clean volumetric flask (100 ml) fitted with a clean funnel.
• Step-4. Fix a Whatman (No 42) filter paper.

 

 Click here to view video

• Carefully transfer the contents in the crucible without any spurting to the volumetric flask fitted with funnel and filter paper.
• After the entire liquid portion is transferred, wait for complete filtration.
• Now the crucible is held with tongs and with help of glass rod, force a jet of water to wash down the entire residue into the filter paper.
• Wash the crucible with distilled water and transfer the contents into the filter paper.
• Step 5. After complete filtration, the filter paper with the residue is carefully taken, folded into a compact form and placed in the original crucible. This contains the insoluble ash along with filter paper. Click here to view video

Making up the volume of soluble ash:

• Step 6. Carefully wash the funnel with distilled water and remove the funnel. Click here to video    
• Step 7. Hold the volumetric flask parallel to your eye to avoid parallax error. Now, distilled water is added to make up the solution to the mark. Click here to view video 
• The volumetric flask is then stoppered and labeled with particulars of date, name of material, etc. This soluble fraction will be used for determination of calcium and phosphorus content of the feed.

Determination of insoluble ash:

• Step 8. The crucible with filter paper is placed on the electrical burner and the filter paper with its contents is ashed. Take all precautions as in case of total ash and continue ashing till there is whitish ash. At times, a platinum loop may be used to turn the charred filter paper for complete ashing. Click here to view video
• Cool the crucible and weigh. Heat again for few minutes, cool and reweigh. If the two weights are almost same, it indicates ashing is complete. Otherwise repeat the process of heating, cooling and weighing till two consecutive weighings agree.

Calculation:

• Weight of crucible + insoluble ash = Z
• Weight of empty crucible = X
• Weight of insoluble ash = Z-X
• Weight of feed taken for ashing = Y-X (Previous exercise)

Significance of insoluble portion of the ash:

• The insoluble fraction mainly consists of silica and other impurities.
• The presence of high insoluble fraction is measure of impurity and adulteration.
• In case of certain feed like rice bran, the high value of total ash is due to the large fraction of insoluble ash, mainly due to the presence of sand.