Yellow Square pH 4.01 calibration powder makes a reference buffer solution for adjusting a pH meter. Dissolve it in 250 ml of distilled or deionised water at 25 °C to get a calibration point in the acidic part of the scale.
Specifications
| Parameter | Value |
|---|---|
| Buffer solution pH | 4.01 pH |
| Water volume | 250 ml |
| Water temperature | 25 °C |
| Water type | distilled or deionised |
| Purpose | calibration of pH meters at home and in the lab |
| Powders in the range | pH 4.01, pH 6.86, pH 9.18 |
What you get
- Acidic check point — a pH 4.01 buffer verifies the meter in the acidic range.
- Clear recipe — powder plus 250 ml of distilled or deionised water at 25 °C.
- Fresh reference — the solution is mixed right before calibration.
- Home and lab use — intended for calibrating pH meters in both settings.
- Room for multi-point calibration — pH 6.86 and pH 9.18 powders are also available.
Who it is for
Anyone who owns a pH meter and checks its accuracy regularly, from aquarium and hydroponics hobbyists to pool owners, school labs and technicians, especially when an acidic buffer is part of the calibration routine.
Who it is not for
People who want a ready-to-use liquid buffer, or who have no distilled or deionised water on hand. If your meter's manual asks for different buffer values, check it before ordering.
Uses and compatibility
Calibration of pH meters at home and in the lab: dissolve the powder in 250 ml of distilled or deionised water at 25 °C, immerse the electrode and set the meter to pH 4.01 following its manual.
What's in the box
pH 4.01 calibration powder; the supplier does not state the amount per pack.
Questions and answers
How much water do I need?
250 ml of distilled or deionised water at 25 °C.
Why not just calibrate in distilled water?
Distilled water absorbs CO₂ and its pH drifts to around 6, so it is not a reliable reference.
When is an acidic buffer useful?
When you mostly measure acidic liquids, a pH 4.01 point keeps the calibration close to your working range.
Are other values available?
Yes, pH 6.86 and pH 9.18 powders are also in the range.
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