Sodium dichloroisocyanurate

Description and assay

Specification history

SODIUM DICHLOROISOCYANURATE (ANHYDROUS and DIHYDRATE) New specifications prepared at the 61st JECFA (2003), published in FNP 52 Add 11 (2003). An ADI of 2.0 mg/kg bw for the anhydrous form was established at the 61 st JECFA (2003).

Chemical names

1,3-dichloro-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, sodium salt Triazine, 2,4,6(1H,3H,5H)-trione, 1,3-dichloro-, sodium salt 1,3-dichloro-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, sodium salt, dihydrate Triazine, 2,4,6(1H,3H,5H)-trione, 1,3-dichloro-, sodium salt, dihydrate

C.A.S. number

Anhydrous: 2893-78-9 Dihydrate: 51580-86-0

Chemical formula

Anhydrous: NaC3N3O3Cl2 Dihydrate: NaC3N3O3Cl2•2H2O

Structural formula

(anhydrous form)

Formula weight

Anhydrous: 219.95 Dihydrate: 255.98

Assay

Available chlorine: not less than 62.0% (anhydrous) and 55.0% - 57.0% (dihydrate) Not less than 98% of NaDCC on the dried basis for both anhydrous and the dihydrate

DESCRIPTION

Hygroscopic white crystalline powder or granules with a slight chlorine odour

FUNCTIONAL USES

Antimicrobial agent for use in drinking water systems

METHOD OF ASSAY

Principle: The sample is dissolved in a solution of potassium iodide. The chlorine of the sample oxidizes iodide to free iodine, which is titrated against sodium thiosulfate. “Available chlorine” is calculated from the titration result. The sample purity on the dried basis is calculated from the available chlorine and the loss on drying. Procedure : Add 200 ml of freshly boiled and cooled distilled water to a 500 ml iodine flask with stirring bar. Add 25 ml of potassium iodide TS. Accurately weigh about 0.23 g - 0.26 g of sample. Transfer to the flask; stir until dissolved. Add either 10 ml of a 1:3 sulfuric acid solution or 10 ml of glacial acetic acid. Titrate with standardized 0.1 N sodium thiosulfate solution (FNP 5) until the solution turns yellow. Add 1 ml of starch TS and continue with the titration until the blue colour just disappears. Record the volume (ml) of titrant used (V). The percent available chlorine (%AvCl) is: %AvCl = 100 × V × N × 0.03546 / W. where N = normality of the titrant W = weight of the sample (g) 0.03546 = molecular weight of chlorine divided by 1000 (Note: For the dihydrate, to ensure the absence of free water, the material is normally dried to slightly less than the theoretical water content, i.e., to < 2:1 water:NaDCC. In this case, the %AvCl can be slightly higher than the theoretical available chlorine, TAC, of 55.40 %.) The content of sodium dichloroisocyanurate is: % NaDCC (dried basis) = 100 × [ %AvCl /64.47] × [100 /(100 - LOD] where 64.47 = percent TAC for anhydrous NaDCC LOD is the percent loss on drying previously determined. IR Spectrum of NaDCC in Diamond Cell

Identification

Solubility (Vol. 4)

Soluble in water, slightly soluble in acetone

Melting range (Vol. 4)

240 o (decomposes)

Infrared spectrum

The infrared spectra of anhydrous NaDCC and NaDCC dihydrate obtained using a diamond anvil compression cell are given in the Appendix.

Sodium (Vol. 4)

Passes test

Purity criteria

pH (FNP 5)

6.0 - 7.0 (1 % soln)

Sodium chloride

Not more than 2 % See description under TESTS

Loss on drying (Vol. 4)

Anhydrous: not more than 3.0% (127 o , 1.5 h) Dihydrate: between 11.0% and 14.0% (127 o , 1.5 h)

Lead (Vol. 4)

Not more than 2 mg/kg Determine using an atomic absorption technique appropriate to the specified level. The selection of sample size and method of sample preparation may be based on the principles of the methods described in Volume 4, “Instrumental Methods.”

Test: Sodium chloride

Principle: Chloride ion is determined using a chloride-specific electrode. Apparatus: − Ion-selective electrode meter − Chloride ion electrode − Reference electrode Reagents: (Note: Use only distilled water. Do not use de-ionized water.) Sodium nitrate, 5 M: Dissolve 42.5 g of reagent-grade material in 100 ml of water. Chloride standards for calibration of the ion-selective electrode meter: − Stock solution (1000 mg/l): Transfer 1.650 g of reagent grade sodium chloride to a 1-litre volumetric flask. Add ca. 500 ml of water to dissolve the salt and dilute to volume. Mix well. − Chloride standard (20 mg/l): Pipette 10 ml of the stock solution into a 500-ml volumetric flask, dilute to volume and mix. − Chloride standard (2 mg/l): Pipette 10 ml of the 20 mg/l chloride standard into a 100-ml volumetric flask, dilute to volume and mix. Procedure: Calibrate the ion-selective electrode meter according to the manufacturer’s instructions. Weigh 0.30 g of the sample. Quantitatively transfer the sample to a 500-ml volumetric flask. Add about 300 ml of water and shake the flask until the sample has completely dissolved. Dilute to volume and mix. Transfer 100 ml of the solution to a 150-ml beaker and, via pipette, add 2 ml of 5 M sodium nitrate. Stir the solution slowly. Introduce the electrodes into the solution. Record the concentration of chloride ion, C (mg/l), directly from the meter display. (Note: If the concentration reading is above 20 mg/l (i.e., 20 ppm), repeat the analysis, decreasing the sample weight as necessary.) Remove the electrodes from the solution, rinse them with water and blot dry. Store the electrodes in a beaker of water until needed. Calculations: % sodium chloride = C × 0.0824/W where W = sample weight (g) 0.0824 = 500/(10000 × FWCl/FWNaCl), and FWCl/FWNaCl is the ratio of the formula weight of chlorine to that of sodium chloride

Test: 4000

3500 3000 2500 2000 1500 1000 500 cm-1 IR Spectrum of NaDCC Dihydrate in Diamond Cell:

Test: 4000

3500 3000 2500 2000 1500 1000 500 cm-1