Introduction:
The aldehydes in reducing sugars will reduce silver ion from Tollen's reagent to metallic silver, leaving a reflective mirror on the inside of a flask.
To conduct demonstration:
1. Add 5mL 10% AgNO3 to a florence flask.
2. Add 1mL 10% NaOH. NOTE: The first two steps may be carried out immediately before lecture.
3. Add 15M NH3 (ammonia) until the brownish silver oxide has just dissolved. (The solution may still appear dark.)
4. Add 7mL of 1% glucose solution and swirl for a few minutes. A silver mirror will coat the inside of the flask.
Safety and Disposal:
Silver nitrate will stain skin and clothing on contact. Gloves should be worn. Avoid breathing ammonia vapors.
Prior to lecture:
1. Prepare the following chemicals:
a. 10% AgNO3 (silver nitrate) - 10g AgNO3/100mL
b. 10% NaOH (sodium hydroxide) - dilute 50% NaOH to 1/5
c. 15M NH3 (ammonia) in dropper bottle
d. 0.1% glucose - 0.2g glucose/200mL
2. Assemble the following equipment:
a. premarked 10mL graduated cylinders for NaOH, AgNO3, and glucose
b. clean 500mL florence (or other desired size and type) flask rinse with dilute nitric acid and distilled water before using
c. gloves
d. goggles
Acknowledgement:
Margaret Asirvatham, Spring 1988; Tom Cech, Fall 1995.