Called Lewisian gneiss, it’s the oldest rock in the UK. It’s found in the northwest extremity of the Scottish mainland and the Western Isles. The gneiss’s new home is in our gardens, where it forms ...

Sodium carbonate, Na 2 CO 3, is also known as washing soda. It can soften water that has temporary hardness and it can soften water that has permanent hardness. It is an inexpensive method of ...

Put a known volume of water into a boiling tube. Add soap solution, one drop at a time, and shake the mixture for 10 seconds. Record the number of drops of soap needed to make a lather. The ...