In addition to the standard quality control system here at Grotech Production, we offer an analytical service to our customers as a troubleshooting service. This is a way of checking that the finished manufactured product falls within desired parameters and why it hasn’t if any issues are found. As part of this service, we can analyse solutions, emulsions or suspensions for their pH value.
What is pH?
The pH scale generally runs from 0 – 14 and tells us how acidic or alkaline (basic) a liquid is. pH stands for ‘potential hydrogen’ and is actually a measurement of the concentration of hydrogen ions (H+, or more properly hydronium ions (H3O+)) and Hydroxide ions (OH-) in a solution.
Because pure water has an equal number of both ions, it has a neutral pH of 7. A pH of less than 7 is acidic (more hydrogen ions), whilst a pH of above 7 is alkaline (less hydrogen ions).
pH values are usually associated with liquids. However, solid materials can also be acidic or alkaline – the pH of a solid becomes apparent once it is dissolved into water.
Mixing Solutions with Different pH
Mixing 2 or more solutions with different pH values will affect the pH value of the final solution. In practice, this means that an acid with a pH value of 1, when mixed with water with a pH value of 7 will have a different pH value as a mixture.
Calculating the final pH of a mixture is beyond the scope of this guide. One thing to remember however, is that the pH scale is logarithmic – a simple way to explain this is that every time you dilute a material with neutral water by a factor of 10, the pH of the resulting mixture will change by 1 pH value. For example –
Since the acid has been diluted x 10.
pH And Safety
Acids and alkalis (bases) can react with various substances and each other – and these reactions can generate heat and sometimes hazardous gases. Acids and alkalis can also directly react with other chemicals, surfaces and skin. Skin can be become badly burned by contact with strong acids such as sulphuric acid and strong bases such as sodium hydroxide. Weaker acids such as phosphoric acid and citric acid and weak bases such as sodium carbonate can also cause irritation. A material with a pH value less than 2.0 is considered to have an extreme acid pH, whilst materials with a pH value greater than 11.5 are considered to have an extreme alkaline pH. Note that the pH isn’t always a good indicator of the “strength” of an acid or base – all acids and alkalis should be treated with respect regardless of their pH value.
Contact with strong acids and alkalis can actually go unnoticed for several minutes and can cause itching and soreness before causing burns. It isn’t quite like it is in films where contact causes you to immediately dissolve, but they are still very dangerous. It is therefore important to stay vigilant if working in the vicinity of a liquid or solid with an extreme pH value and to wear the appropriate PPE.
Things to Note About pH
- pH can often be associated with colours, this does not mean that all red liquids are acidic, all purple are alkaline and green are neutral. A pH change can cause a colour change, but this will be dependent on the material.
- pH cannot be seen and must be tested to determine a value.
- Bleach should never be mixed with any acids, as this will release toxic chlorine gas.
- Diammonium phosphate should never be mixed with bleach or strong bases, as this will release harmful ammonia vapours.
- Metals such as steel and aluminium may be corroded by strong bases.
- Metals such as steel and aluminium may be etched and pitted by strong acids, flammable hydrogen gas may also be released.
- Fats are “saponified” by bases, so a triglyceride as found in vegetable oil would be broken down into the salt of a fatty acid and glycerol, this is how soaps are made and are why your fingers feel soapy when you come into contact with a base.
If you have a product that requires manufacturing to specific pH values and you’d like to discuss this with one of our Helpful Manufacturing People, give us a call on 01405 761746 or contact us here.
