CALDUR® pH 2-5 – Colorimetric
pH determination in the acidic range using a color chart (pH 2-5)

Private customers can also find our range in our partner store Ampha-Analyse.
Reagent for CALDUR® pH 2-5 – Colorimetric:
See also:
CALDUR® pH 2-5 test set – Colorimetric
What is the pH value 2-5 measured for?
The pH value is one of the most fundamental parameters in water analysis. It describes the acidic or basic character of a solution. The pH 2-5 range covers the strongly acidic to slightly acidic range, which is relevant in many industrial applications.
In water treatment, the low pH range is monitored in regeneration processes of ion exchangers, in the neutralization of acidic wastewater and in metal processing (pickling baths).
In cooling water systems, a pH value that is too low can lead to massive corrosion of metallic materials. Regular monitoring is therefore essential for system protection.
How does the test set work?
The CALDUR® pH 2-5 Test Set – Colorimetric uses a mixing indicator that takes on a characteristic color depending on the pH value of the sample. After adding a reagent to the water sample, the color is compared with the color chart provided within 1 minute.
Advantages of the CALDUR® test set
- Optimized for the acidic pH range 2-5
Higher resolution in the acidic range than universal pH test sets
- 300 provisions per set
Very economical for continuous use
- Fastest analysis in just 1 minute
Immediate results on site
- Only 1 reagent required
Particularly quick and easy handling
- Robust plastic housing with hinged lid
Safe transportation and protection of reagents
Areas of application
Carrying out the measurement:
- Fill water sample into test tubes up to the 10 ml mark
- Add 5 drops of mixing indicator and mix
- Wait 1 minute
- Perform color comparison with color chart
Tip for best results
The sample should have a temperature between 15 and 25°C, as the pH value is temperature-dependent. Strongly buffered samples provide more reliable results. With very weakly buffered samples, the Reagent itself can have a slight influence on the pH value.
Important notes
- Take care when handling strongly acidic samples – wear protective gloves
- Heavily colored samples can make reading difficult
- Oxidizing agents can decolorize the Reagent
- Thoroughly rinse the test tube with the sample before each measurement
- Perform color comparison in daylight
Measuring range
| Measuring level | Description |
|---|---|
| pH 2.0 | Strongly acidic (red) |
| pH 2.5 | Acidic (red-orange) |
| pH 3.0 | Acidic (orange) |
| pH 3.5 | Acidic (orange-yellow) |
| pH 4.0 | Slightly acidic (yellow) |
| pH 5.0 | Slightly acidic (light yellow) |
If the color lies between two fields, you can form the mean value
(e.g. between pH 3.0 and 3.5 = approx. pH 3.2-3.3).
Number of possible destinations
With a CALDUR® test set pH 2-5 you can carry out 300 measurements.
This refers to the quantity of reagents contained.
Measuring accuracy and reproducibility
Readability: ± 0.5 pH units
Reproducibility: Very good if the application instructions are followed
Interference: Heavily colored or true samples can make color readings difficult. The Reagent may deviate slightly at very high salt concentrations. Oxidizing agents (chlorine, ozone) can decolorize the Reagent.
What to do if measured values are out of range?
Measured value > pH 5
Use the CALDUR® pH 5-8 test set for the next higher range.
Measured value < pH 2
The sample is extremely acidic. Dilute the sample 1:10 with distilled water and measure again. The actual pH value is then correspondingly lower than the value read.
Specifications at a glance
Reagents (1 reagent)
| Property | Value |
|---|---|
| Parameters | pH value (acidic) |
| Item number | 31-072380 |
| Method | Colorimetric (mixing indicator) |
| Measuring principle | Color comparison with 6-stage color chart |
| Measuring range | pH 2 to 5 |
| Color scale | 6 measuring levels (2.0 / 2.5 / 3.0 / 3.5 / 4.0 / 5.0) |
| Analysis duration | 1 minute |
| Number of provisions | 300 |
| Number of reagents | 1 |
| Packaging | Hinged lid box |
| Packaging size | 103 x 91 x 36 mm |
| weight | approx. 120 g |
| Scope of delivery |
|---|
| 1 reagent bottle (mixing indicator) with detailed labeling |
| 1 test tube with 10 ml scale |
| 1 color card with 6 measuring levels |
| Detailed operating instructions (DE/EN) |
| Safety data sheets for all reagents |
| Robust hinged lid box (103 x 91 x 36 mm) |
Reagent details
| Reagent | Volume | Shelf life | Notes |
|---|---|---|---|
| Mixing indicator (pH 2-5) | 30 ml | 24 months (24M) | Indicator solution, shake before use |
Shelf life: The shelf life starts from the date of manufacture (printed on the bottle).
After opening, the reagents should be used within 12 months.
Store the test kit in a dry, cool place (10-25°C) and protected from direct sunlight.
Additional information
| Packaging | Hinged lid box, Refill pack |
|---|---|
| Product category | Testset |
Flyer
Operating instructions
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