Question: what is a pH scale

Marisol Collins answered on 14 Nov 2016:

Another great question Arora! Measuring pH is something which is important to many areas of science. We know that chemical solutions can be an acid or an alkali and anywhere in between. An alkali is a base chemical that dissolves in water, and it can neutralise an acid. We are surrounded in our lives by solutions that are acids, for example vinegar, lemon juice (and our own stomachs contains one of the strongest acids of all!), and alkalis, like ammonia and bleach. The pH scale is a way of helping us measure how acidic or alkaline a solution is. The scale has both numbers and colours, depending on how we are testing it. The number scale goes from 1 (the most acidic) to 14 (the most alkaline). Slap bang is in the middle at 7 is water, which we say is neutral. The colour scale tends to show acids as red, changing to green, blue and black as you go to the most alkaline.

As a vet, I use the pH scale very often in my work. One test that is very important when we are looking at diseases of the urinary system (the kidneys, bladder and the tubes that link them to each other and the outside world) is to look at the pH of urine. I have a little paper strip called a Uristix that I dip into a urine sample, and it will change colour to tell me the pH. Normal urine in cats and dogs should be at around pH6, making it slightly acidic. In cases where there is a bacterial infection, the pH of the urine can go up, to pH 8 or 9. At higher pH, the environment in the bladder is not very healthy and certain bladder stones are more likely to form too. We use food and medication to help reduce the pH of the urine to keep the bladder happy and healthy 🙂