Gum Arabic Mountants
Gum arabic is obtained from two species of acacia tree, and is also known as gum acacia for that reason. It is water soluble and forms a thick, syrupy solution that is suitable as the basis for aqueous mounting media. It is a mixture of compounds, mostly carbohydrates, and is not chemically pure so its composition may vary from sample to sample. Since it is a natural product, it may also contain dirt. If so, it may be dissolved in water and filtered through glass wool. Quite commonly, mounting media made from gum arabic also contain high concentrations of a sugar, often glucose, fructose or sucrose.
Both Apathy’s and Farrants’ mounting media are commonly used. Both are suitable for coverslipping lipid stains, and are recommended. Both are available commercially, and most laboratories purchase premade solutions rather than make their own. There is also a variant of Apathy’s suitable for mounting metachromatic stains (Highman – see list below), usually not advised with sugar gum mixtures due to leaching of the dye.
The list of media below is not exhaustive. Due to the sugar and gum content they should contain a preservative, and a small crystal of thymol is probably the most convenient. In the list, all numbers refer to grams if a solid and milliliters if a fluid.
Formula
Material | Amount | |
---|---|---|
Water | 30 | mL |
Gum arabic | 30 | g |
Fructose | 30 | g |
Procedure
- Dissolve gum arabic in water with gentle heat.
- Add fructose and mix well.
- Avoid vigorous agitation to avoid bubbles.
Notes
- A small crystal of thymol may be added as a preservative.
- Gray replaces fructose crystals with fructose syrup and reduces the water to 20 mL.
- Drury & Wallington use sucrose instead of fructose.
Material | Amount | |
---|---|---|
Water | 40 | mL |
Glycerol | 20 | mL |
Gum arabic | 40 | g |
Procedure
- Dissolve the gum arabic in warm water.
- Add the glycerol and mix well.
- Avoid vigorous agitation to avoid bubbles.
Notes
- Preserve with a little camphor, phenol or thymol.
The list of media below is not exhaustive. Due to the sugar and gum content they should contain a preservative, and a small crystal of thymol is probably the most convenient. In the list all numbers refer to grams if a solid and millilitres if a fluid.
Variant | Material | ||||
---|---|---|---|---|---|
Distilled water | Gum arabic | 99.5% glycerol | Other | ||
Chevalier | 60 mL | 20 g | 20 mL | – | |
Davies | 30 mL | 30 g | 30 mL | Arsenic trioxide 0.1 g (or thymol crystal) | |
Hogg | 75 mL | 25 g | – | Phenol 5 g | |
Langerhaus | 20 mL | 60 g | 25 mL | Phenol 1 g | |
Martin | 50 mL | 50 g | 25 mL | Camphor 0.2 g (or thymol crystal) | |
Robin I | 45 mL | 15 g | 30 mL | – | |
Robin II | 100 mL | 50 g | 50 mL | – |
Variant | Material | ||||
---|---|---|---|---|---|
Distilled water | Gum arabic | Sugar | Other | ||
Highman | 50 mL | 25 g | Sucrose 25 g | Potassium acetate 25 g or sodium chloride 10 g | |
Landau | 30 mL | 30 g | Glucose 35 g | – | |
Lillie & Ashburn | 100 mL | 50 g | Sucrose 50 g | Thymol 0.1 g |
Safety Note
Prior to handling any chemical, consult the Safety Data Sheet (SDS) for proper handling and safety precautions.
References
- Gray, Peter. (1954)
The Microtomist’s Formulary and Guide. pp. 631.
Originally published by:– The Blakiston Co.
Republished by:– Robert E. Krieger Publishing Co - Carleton, H M, and Leach, E H, (1938)
Histological Technique, 2nd ed.
Oxford University Press, London, England