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# pH Buffer Solution Mixing Tutorial
pH Meters require calibration with Buffer Solutions, follow this tutorial to mix the required solutions.
Prepare the following items:
* 250mL Bottle \*3
* Buffer Solution Powder(pH 4.00, pH 6.86, pH 9.18 each)
* Buffer Solution Labels
pH 6.86 Buffer Solution is shown as an example here.
### Mixing the Solution
Clean the plastic bottle with water and wipe dry completely.
Pour the powder into the bottle.
Add 250mL of distilled water into the bottle, also wash the packet with a little bit of distilled water to dissolve all the remaining powder and then pour it into the bottle.
Close the bottle cap tightly and shake thoroughly, make sure all powder is dissolved. Put on a label to identify.
### Usage Guide for Buffer Solution
* In order to maintain the quality of the solution, avoid leaving the cap open and expose the solution in the air for long periods of time.
* It is recommended to simply pour out some solution and discard after using, rather than use the entire bottle for calibration.
### Safety Precautions
Although the powder in the packets are not toxic and harmful to humans, it is still recommended to handle with care.
* Avoid ingesting: The powders are non-toxic, but ingestion may lead to diarrhea.
* Avoid touching: The powders are non-toxic, but touching may lead to skin irritation.
