Colloidal Iron Suspensions
Colloidal iron suspensions are available commercially, and these may be found quite satisfactory. The working solution is usually given as an equal parts mixture of the suspension and 12% acetic acid.
For those who wish to make their own suspension, any of those below will be found suitable for use in Hale type procedures for the demonstration of acid mucopolysaccharides. Once made up, the suspensions are stable for several months, perhaps years, although proper control sections should always be used to ensure they are still suitable for use.
It should be noted that colloidal iron may also react with nuclear phosphate, so nuclear chromatin will often be stained.
Solution
| Material | Amount | |
|---|---|---|
| Distilled water | 250 | mL |
| Ferric chloride, 29% aqu. | 4.4 | mL |
Preparation
- Bring the water to a boil.
- Slowly add the ferric chloride while stirring.
- Continue boiling until the solution changes to clear, dark red.
- Cool.
Working Solution
- Stock colloidal iron – 20 mL
- Distilled water – 15 mL
- Glacial acetic acid – 5 mL
| Material | Amount | |
|---|---|---|
| Distilled water | 250 | mL |
| Ferric chloride, 29% aqu. | 4.4 | mL |
Preparation
- Bring the water to a boil.
- Slowly add the ferric chloride while stirring.
- Continue boiling until the solution changes to clear, dark red.
- Cool.
- Dialyse against 2 litres distilled water, changing 3 times over 24 hours.
Working Solution
- Stock colloidal iron – 10 mL
- Distilled water – 18 mL
- Glacial acetic acid – 12 mL
| Material | Amount | |
|---|---|---|
| Ferric chloride | 75 | g |
| Glycerol | 100 | mL |
| Strong Ammonia | 55 | mL |
| Distilled water | as needed | |
Preparation
- Dissolve the ferric chloride in 250 mL water.
- Add the glycerol, then slowly add the ammonia, stirring all the time.
- Place into dialysis tubing, allowing for quadrupling of the volume.
- Dialyse against distilled water for 72 hours, changing twice daily.
Working Solution
- Stock colloidal iron – 20 mL
- 2M (12%) acetic acid – 20 mL
| Material | Amount | |
|---|---|---|
| Ferric chloride | 100 | g |
| Glycerol | 130 | mL |
| Strong Ammonia | 110 | mL |
| Distilled water | 230 | mL |
Preparation
- Dissolve the ferric chloride in the water. Add the glycerol.
- To ¾ of the solution, while stirring, slowly add ammonia until pasty (±110 mL).
- Slowly add the other ¼ until clear, dark red-brown.
- Allowing for quadrupling of the volume, dialyse against distilled water, changed daily, until it reverts to the original volume (±2 weeks).
Working Solution
- Stock colloidal iron – 10 mL
- Distilled water – 10 mL
- 2M (12%) acetic acid – 20 mL
Safety Note
Prior to handling any chemical, consult the Safety Data Sheet (SDS) for proper handling and safety precautions.
References
- Humason, G. L., (1967)
Animal tissue techniques, Ed. 2
W. H. Freeman and Company, San Francisco, Ca, USA - Culling C.F.A., (1974)
Handbook of histopathological and histochemical techniques Ed. 3
Butterworth, London, UK. - Lillie, R.D., (1954)
Histopathologic technique and practical histochemistry Ed.2
Blakiston, New York, USA.
