Scott’s tap water substitute is an alkaline solution which is used to ‘blue’ hematoxilin.
The solution removes an H+ group from aluminum hematein (which is the staining chemical of the hematoxylin solution), and changes it to a -OH group.
This changes the color of aluminum hematein from red to blue.
The more alkaline the bluing agent is, the quicker the reaction and color change will occur, and the less time it takes to use it.
This reagent is employed as a substitute for tap water to speed up the bluishing hematoxylin reaction.
The pH of tap water is typically around 7, and it may take 5-10 minutes for the hematoxylin to turn blue. If the tap water is more acidic (pH 5 or below), the nuclus of the cells may not turn “blue”.
Scott’s Tap Water substitute recipe
| Sodium bicarbonate | 2 g |
| Magnesium sulphate (anhydrous) | 10 g |
| Water | 1 L |
Weight sodium bicarbonate and magnesium sulphate with a laboratory scale.
Put the two salts in a beaker, add 900 ml of water, and stir with a magnetic stirrer until the salts are dissolved.
Use a volumetric flask to achieve the correct volume.
Bibliography
- Kiernan J. A. (2008) Histological and histochemical methods, 4th ed. Bloxham: Scion Publishing Ltd.