Perform a colorful reaction with lactose!

15 minutes



  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
  • Observe safety precautions when working with boiling water.
General safety rules
  • Do not allow chemicals to come into contact with the eyes or mouth.
  • Keep young children, animals and those not wearing eye protection away from the experimental area.
  • Store this experimental set out of reach of children under 12 years of age.
  • Clean all equipment after use.
  • Make sure that all containers are fully closed and properly stored after use.
  • Ensure that all empty containers are disposed of properly.
  • Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
  • Do not replace foodstuffs in original container. Dispose of immediately.
General first aid information
  • In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
  • If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
  • In case of inhalation: Remove person to fresh air.
  • In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
  • In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
  • In case of injury always seek medical advice.
Advice for supervising adults
  • The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
  • This experimental set is for use only by children over 12 years.
  • Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
  • The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
  • The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
  • Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.

FAQ and troubleshooting

I did not get the orange color in the end. What is wrong?

It is very important that the water you use in the first stage be boiling hot. Try repeating the experiment with hotter water and the extra reagents provided in your set.

Why do we need boiling water?

Heat facilitates or speeds up many reactions. Sometimes, a lot of heat is needed to obtain the desired result. To learn more, please read the scientific description of this experiment.

What else instead of lactose can I try for this experiment?

You can use this method to detect some sugars, such as lactose and fructose. Try dissolving a few spoonfuls of honey in water. You can also use dry fructose or lactose.

Step-by-step instructions

To perform this test, you’ll need a hot solution of a reducing sugar such as lactose.


Add sodium carbonate Na2CO3 to create a basic medium for the reaction.


When these conditions are met, add some copper sulfate CuSO4, which is what will react with the reducing sugar.


Sugar reduces copper sulfate to produce a beautiful orange precipitate.



Dispose of solid waste together with household garbage. Pour solutions down the sink. Wash with an excess of water.

Scientific description

There are two types of sugars: reducing (such as lactose or glucose) and nonreducing (such as sucrose). Both types can be sweet and both types can be found in foods. Reducing sugars get their name from the fact that they tend to reduce other compounds, i. e., give said compounds some electrons. Copper ions Cu2+ from CuSO4, in turn, tend to take electrons when offered, so they are a good match for reducing sugars. Their interaction is easy to observe, manifesting as a dramatic color change from colorless or blue CuSO4 sugar solutions to yellow-orange or even red. Are there any reducing sugars in honey or corn syrup? Test them to find out !