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Chlorine Test Kits

Visual Kits

Range MDL Method Type Kit Refill
0.00 - 0.20 ppm 0.04 ppm DDPD (free & total) ULR CHEMets K-2511 R-2511
0.1 - 2.0 ppm 0.1 ppm DPD (free & total) CHEMets K-2500 R-2500
0.0 - 1.0 & 0 - 5 ppm 0.05 ppm DPD (free & total) CHEMets K-2504 R-2500
0.0 - 1.0 & 1 - 5 ppm 0.05 ppm DDPD (free & total) CHEMets K-2505 R-2505
0 - 25 ppm 2.5 ppm DPD (free & total) HR CHEMets K-2520D R-2500
0 - 125 ppm 5 ppm DPD (free & total) HR CHEMets K-2520A R-2500
0 - 500 ppm 10 ppm DPD (free & total) HR CHEMets K-2520B R-2500 + A-0171
0 - 2,000 ppm 40 ppm DPD (free & total) HR CHEMets K-2520C R-2500 + A-0171
0.0 - 1.55 % as NaOCl 0.3% DPD (hypochlorite) HR CHEMets K-5808 R-2500 + A-0171
0 - 12.5 % as NaOCl 2.5% DPD (hypochlorite) HR CHEMets K-5816 R-2500 + A-0171

Instrumental Kits

Range Method Type Kit
0 - 5.00 ppm DPD (free & total) Vacu-vials K-2513*
0 - 5.00 ppm DPD (free & total) SAM Photometer + Vacu-vials I-2001*

The CHEMetrics test kits for the determination of Chlorine in aqueous solutions are based on patented Self-Filling Reagent Ampoule technology, reducing the user’s exposure to chemicals, and employ the DPD and DDPD methods, delivering sensitivity and accuracy within two minutes or less. Premixed. Premeasured. Precise. Each kit contains 30 tests. Visual and instrumental chlorine testing kit formats span low and high measurement ranges. CHEMets® and HR CHEMets® visual test kits use colour comparators for analysis while Vacu-vials® instrumental kits rely on CHEMetrics direct-readout photometers or spectrophotometers capable of accepting a 13-mm diameter round cell. Suitable for potable water, municipal wastewater, water distribution systems, cooling tower water and swimming pool testing.

The Chlorine Vacu-vials test kit K-2513 can be used with a Hach DR900 Colorimeter in conjunction with the CHEMetrics DR900 Vacu-vials® Adapter, Cat. No. A-0215. No endorsement by Hach Company is implied or intended.

The DPD Method

Diethyl-p-phenylene diamine (DPD) is an industry standard methodology for the determination of Chlorine and is USEPA-accepted. In the DPD method, free chlorine reacts with DPD in the ampoule to form a pink product. When ammonia or amines are present, some of the chlorine may exist as combined chlorine. Combined chlorine will not interfere with the free chlorine results, provided the readings are taken after one minute of colour development in accordance with the test instructions. To determine total chlorine (the sum of free and combined), use the A-2500 Activator Solution (potassium iodide) included in the kit. Results are expressed as ppm (mg/l) Cl2.

The DPD method is also applicable to the direct determination of hypochlorite concentrations in various cleaning preparations and disinfectants prior to their dilution. DPD reacts with hypochlorite ions to form a pink colour. Results are expressed as percent (%) NaOCl.

USEPA Methods for Chemical Analysis of Water and Wastes, Method 330.5 (1983).
APHA Standard Methods, 22nd ed., Method 4500-Cl G- 2000.

USEPA Acceptance Letter for CHEMetrics Instrumental DPD Chlorine Kits for drinking and wastewater testing
Technical Data Sheet

The DDPD™ Method

The DDPD™ method is derived from the DPD chemistry, and is a dimethyl-substituted form of DPD. Test kits that employ this chemistry are well suited for use where biocides and chromate corrosion inhibitors are used simultaneously. DDPD reacts with free chlorine to form a purple product. When ammonia or amines are present in the sample, some of the chlorine may exist as combined chlorine. To determine total chlorine (the sum of free and combined), use the A-2500 Activator Solution (potassium iodide) included in the kit. Results are expressed as ppm (mg/l) Cl2.

Developed by CHEMetrics.

Technical Data Sheet


Because of its strong oxidising properties, free chlorine is routinely added to water as a disinfectant or biocide (chlorination). Disinfection with monochloramine (chloramination) is an alternative or a supplement to chlorination to maintain longer-lived but weaker residuals in water distribution pipelines. See our article Monochloramine As A Disinfectant In Water for more information. Chlorine was one of the first chemicals ever used in water treatment and has been in use since the 19th century to treat drinking water.

Chlorine is used to treat potable waters, municipal wastes and wastewater, water distribution systems, supply reservoirs, cooling tower water, swimming pools and spas. When used to treat potable water, chlorine helps alleviate the adverse effects of iron, manganese, ammonia, and sulphide.

Owing to the formation of harmful disinfectant by-products (DPB) it is imperative to closely monitor the residual concentration of chlorine. The World Health Organisation has set a guideline maximum value of 5mg/l residual Cl2, although UK water companies typically keep levels to 0.5mg/l or less. In the US, the Maximum Residual Disinfectant Level in drinking water is 4 mg/l.

Some residual chlorine may be in present in surface waters from water treatment effluent. Total water chlorination tests can also be used to determine the total residual oxidizer (TRO) concentration of seawater.

What is Chlorine?

Chlorine is a halogen and strong oxidising agent that is used by many industries as a disinfectant in water. Total chlorine is the sum of free chlorine (hypochlorite ion and hypochlorous acid) and chloramines (also known as combined chlorine) which are formed by the reaction of free chlorine with ammonia.