Introduction
This manual provides instructions for the Hach Hardness Total Reagent Set, Model 2437800. This set is designed for use with the HA-71A Test Kit to accurately determine total hardness in water samples using the drop count titration method. The reagents allow for measurements in the range of 0-20 mg/L (0-20 gpg) as CaCO3.
Image 1: Hach Hardness Total Reagent Set (Model 2437800) containing Buffer Solution (Hardness 1), Hardness 2, and Hardness 3 Test Solutions.
Safety Information
Always read and understand the Safety Data Sheets (SDS) for all reagents before use. SDS are available on the Hach website. Follow all local, state, and federal regulations for chemical handling and disposal.
- Wear appropriate personal protective equipment (PPE), including safety glasses and gloves, when handling reagents.
- Avoid contact with skin and eyes. In case of contact, rinse immediately with plenty of water and seek medical advice.
- Do not ingest reagents. If ingested, seek immediate medical attention.
- Keep reagents out of reach of children and pets.
- Store reagents in a cool, dry, well-ventilated area, away from incompatible materials.
Product Components
The Hach Hardness Total Reagent Set (Model 2437800) includes the following solutions:
- Buffer Solution (Hardness 1): Used to adjust the pH of the sample.
- Hardness Indicator Solution (Hardness 2): Changes color in the presence of hardness ions.
- EDTA Titrant Solution (Hardness 3): Used to titrate the sample until the endpoint is reached.
Note: This product contains only the reagent solutions. Other components of the HA-71A Test Kit, such as sample cells, mixing bottles, or a titrator, are sold separately.
Setup and Preparation
Before beginning the hardness test, ensure you have the following items ready:
- Hach Hardness Total Reagent Set (Model 2437800)
- HA-71A Test Kit components (e.g., sample cell, mixing bottle, titrator, if applicable)
- Clean, deionized water for rinsing
- The water sample to be tested
- Appropriate personal protective equipment (PPE)
Sample Collection
Collect a representative water sample in a clean container. For best results, test samples as soon as possible after collection. Avoid collecting samples that contain excessive air bubbles or suspended solids.
Operating Instructions: Total Hardness (Drop Count Titration)
This procedure outlines the steps for determining total hardness using the Hach Hardness Total Reagent Set (Model 2437800) and the drop count titration method. Refer to your HA-71A Test Kit manual for specific sample volumes and equipment usage.
- Prepare the Sample: Measure the specified volume of water sample (e.g., 25 mL or 50 mL, as per HA-71A kit instructions) into a clean sample cell or mixing bottle.
- Add Buffer Solution: Add 2 drops of Buffer Solution (Hardness 1) to the sample. Swirl gently to mix.
- Add Indicator Solution: Add 2 drops of Hardness Indicator Solution (Hardness 2) to the sample. Swirl gently to mix. The sample should turn red if hardness is present. If the sample turns blue, it indicates zero hardness, and no further titration is needed.
- Titrate with EDTA: Add EDTA Titrant Solution (Hardness 3) drop by drop to the sample, swirling after each drop. Count the number of drops added.
- Observe Color Change: Continue adding drops until the color of the sample changes from red to a clear blue. This is the endpoint of the titration.
- Record Results: The number of drops of EDTA Titrant Solution (Hardness 3) required to reach the blue endpoint directly corresponds to the total hardness of the sample. Refer to your HA-71A Test Kit instructions for the conversion factor (e.g., 1 drop = 1 mg/L or 1 gpg as CaCO3).
- Rinse Equipment: Thoroughly rinse all glassware and equipment with deionized water after each test.
For precise results, ensure consistent drop size and careful observation of the color change.
Maintenance and Storage
- Storage: Store the reagent bottles tightly capped in their original packaging, in a cool, dry place, away from direct sunlight and extreme temperatures. Refer to the reagent labels for specific storage temperature ranges.
- Shelf Life: Observe the expiration dates printed on the reagent labels. Using expired reagents may lead to inaccurate results.
- Handling: Avoid contamination of reagents. Do not return unused reagent to the original bottle.
- Disposal: Dispose of used reagents and samples according to local environmental regulations. Consult the Safety Data Sheets (SDS) for specific disposal instructions.
Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| Sample does not turn red after adding Hardness Indicator (Hardness 2). | Sample has zero hardness, or pH is incorrect. | If blue, hardness is zero. Ensure Buffer Solution (Hardness 1) was added correctly. Re-test with a known hard water sample to verify reagents. |
| Color change is unclear or difficult to determine. | Insufficient lighting, turbid sample, or expired reagents. | Perform test in good lighting. Filter turbid samples if possible. Check reagent expiration dates. Use a white background for better visibility. |
| Inconsistent results. | Inconsistent drop size, improper mixing, or contaminated glassware. | Ensure consistent drop delivery. Swirl gently after each drop. Thoroughly clean and rinse all glassware with deionized water before use. |
| Titration requires too many drops (high hardness). | Sample hardness exceeds the recommended range, or sample volume is too large. | For very hard water, consider diluting the sample with deionized water and multiplying the final result by the dilution factor, or use a smaller sample volume if your kit allows. |
Specifications
- Product Name: Hach Hardness Total Reagent Set
- Model Number: 2437800
- Measurement Method: Drop Count Titration
- Measurement Range: 0-20 mg/L (0-20 gpg) as CaCO3
- Manufacturer: HACH COMPANY
- Components: Buffer Solution (Hardness 1), Hardness Indicator Solution (Hardness 2), EDTA Titrant Solution (Hardness 3)
Support and Contact Information
For technical assistance, product inquiries, or to access Safety Data Sheets (SDS), please visit the official Hach website or contact Hach customer support.
Hach Official Website: www.hach.com
Please have your product model number (2437800) available when contacting support.
