HANNA PHOTOMETER REAGENTS · HI93720
Resolve low-level calcium hardness, not dissolved calcium.
Keep the HI97720 calcium-hardness method supplied with the matched three-liquid reagent set. Choose 100 or 300 determinations for low-hardness water monitoring without changing the chemistry or reporting basis.
Official Hanna calcium-hardness reagent-set reference photo. Printed lot and expiry markings are illustrative, not supplied-stock dates.
Match the method, not just the element name
HI97720: 0.00 to 2.70 mg/L as CaCO₃. Calmagite chemistry measures calcium hardness as calcium carbonate over 0.00 to 2.70 mg/L as CaCO₃ on the HI97720. This is not direct dissolved calcium as Ca²⁺, not HI937521 oxalate reagents, and not an undiluted swimming-pool hardness range.
What the selected pack supplies
A complete calcium-hardness A/B/C liquid reagent set for the selected 100 or 300 tests. This is reagent replenishment, not a photometer or CAL Check kit.
Where this method fits
The HI97720 is intended for low hardness levels such as those found in water-purification systems. For a documented 100-fold dilution, add 0.5 mL of sample to a clean, dry 50 mL beaker and bring to the 50 mL mark with hardness-free water. Account for dilution when interpreting the original sample; do not treat the native range as a pool-water range.
The HI97720 workflow at a glance
Rinse a graduated beaker with unreacted sample and fill it to 50 mL. Add 0.5 mL of reagent A, swirl, then add 0.5 mL of reagent B and swirl. Fill two cuvettes with 10 mL of this treated sample. Add one drop of reagent C to the first cuvette only, stopper, cap and invert to mix: this is the blank. Align its cap notch with the holder groove and zero the HI97720. Replace it with the second cuvette, aligned in the same way, and press Read for calcium hardness as CaCO₃.
Check the sample matrix
Excessive heavy metals can interfere. Calcium contamination in the beaker, syringes or cuvettes affects this low-level test; repeat cleanliness checks until results are consistent. Dilutions require hardness-free water, not ordinary tap water.
Choose a pack around your workload
HI93720-01 supplies 100 tests; HI93720-03 supplies 300 tests. The larger pack supplies three times the determinations, not a different measuring range. One order quantity means one complete selected pack. Choose by testing frequency and the lot/expiry markings on supplied stock.
What to have beside the reagent set
Supply the compatible photometer, cuvettes with stoppers and caps, and the measuring/dispensing accessories required by the method separately. Use hardness-free water for calcium-hardness dilution. CAL Check standards are separate instrument-verification materials, not replacements for sample reagents.
Handling before you begin
Review all three US component SDS. Reagent B may corrode metals and causes severe skin burns and eye damage; use the specified protection and handling controls. Hanna flags both complete pack sizes as Dangerous Goods for ground shipment only.
Use the linked HI97720 instrument manual as the method reference for the complete procedure, precautions and instrument operation. This is not a separate reagent instruction manual.
Frequently Asked Questions
Should I choose 100 or 300 tests?
HI93720-01 supplies 100 tests; HI93720-03 supplies 300 tests. Both are complete reagent sets for the same method. Choose by expected workload and marked expiry dates, not by a different analytical range.
Is this calcium hardness or dissolved calcium?
It is calcium hardness, reported as mg/L CaCO₃. HI97720 uses calmagite chemistry over 0.00 to 2.70 mg/L as CaCO₃. HI937521 measures calcium directly with different chemistry and is not a substitute.
Why does the method need two cuvettes?
Both receive 10 mL of the sample treated with A and B. Add one drop of C to only the first cuvette and use that as the blank. Zero with the blank, then read the second cuvette. Do not add C to both.
Can I measure pool water without dilution?
Do not assume that. The native HI97720 range is low-level hardness. The manual documents a 100-fold dilution using 0.5 mL sample brought to 50 mL with hardness-free water; follow it and account for dilution when interpreting results.
Why is clean glassware especially important?
This low-range method detects calcium contamination from the beaker, syringes and sample cells. Repeat the cleanliness test until results are consistent and use hardness-free water for dilution.
Which photometers are documented for HI93720?
Both packs are documented for HI97720. The procedure and range on this page use HI97720 as the primary reference; follow the exact instrument method when using another model.
Which sample conditions should I check first?
Excessive heavy metals can interfere. Calcium contamination in the beaker, syringes or cuvettes affects this low-level test; repeat cleanliness checks until results are consistent. Dilutions require hardness-free water, not ordinary tap water.
Are the instrument, cuvettes and CAL Check standards included?
No. These are reagent-only packs. Provide the photometer, cuvettes with stoppers and caps, and the method-required sampling and dispensing accessories separately. CAL Check standards are separate instrument-validation materials, not test reagents.
