ISO863:2008(E) 7.5 Vacuumflask,250ml. 7.6 Beakers,250 ml and400 ml. 7.7 Pipettes,50mland100ml,classAinaccordancewithIsO835:2007. 7.8 Burette,50ml,classAin accordancewithISO 385:2005. 7.9 Uniform temperature enclosure, controlled thermostatically at (40+1)°C. 7.10 Volumetric flasks, 500ml and 1000ml. 7.11 Conical flask, 250 ml. 7.12 Balance, capable of weighing to an accuracy of± 0,000 5 g 7.13Apparatusformeasuringtheabsorbance,at520nmand620 nmofasolutioncontained ina titration beaker, while stirring. 7.14 Stirrer, e.g. magnetic stirrer, with inert, e.g. PTFE, covered bar. 7.15 pHmeter, capable of measuring to an accuracy of ±0,05. 8 Standardization of solutions 8.1 Standardizationof theEDTAsolution beaker (7.6) with approximately 100 ml of water. Cover the beaker with a watch glass and carefully introduce solution and make up to 1 000 ml with water. this solution to (12,5 ± 0,2) with the sodium hydroxide solution (6.8). Determine the end-point using one of the following two methods a) Photometric determination of the end-point (reference method): the beaker in the apparatus (7.13)set at 620 nm when using murexide or at 520 nm when using the mixed indicator and, while stirring continuously, titrate with 0,03 mol/I EDTA solution (6.14). In the vicinity of the colour change, construct a curve giving the absorbance values as a function of the volume of EDTA colour change and the line of almost constant absorbance after the colour change. Calculate the factor,fi, of the EDTA solution from Equation (1): m1 ×16,652 mg×50 (1) f1= 100,09×0.03×V1 4 @ISO 2008-All rights reserved ISO863:2008(E) where m1 is the mass of calcium carbonate, expressed in grams; V1 is the volume of EDTA solution used for the titration, expressed in millilitres; 100,09 is themolecularmass of calcium carbonate b) Visualdeterminationoftheend-point(alternativemethod) Add, without weighing, about 0,1 g of the calcon indicator (6.17), or Patton and Reeders reagent mixture (6.18). Stir and titrate with the 0,03 mol/l EDTA solution (6.14) until the colour changes from pink to blue standardization factorf; using Equation (1). 8.2Standardization of the 0,1mol/l solution of hydrochloric acid (6.6) to the solution and titrate with the 0,1 mol/l dilute hydrochloric acid (6.3) until the colour changes from yellowto orange. Calculate the factor,2, of the hydrochloric acid solution from Equation (2): 2×m2 1000 = m2×188,70 f2 = (2) 105,9890,1×V2 where m2 is the mass of sodium carbonate, expressed in grams; V2 is the volume of hydrochloric acid used for the titration, expressed in millilitres; 105,989 is the molecularmass of sodiumcarbonate 9 Procedure 9.1 Storage and filtration Pipette 100 ml of freshly boiled water into the polyethylene container (7.1), seal and place in the uniform (7.2).Immediatelysealthecontainerhermetically. Shake vigorouslyforabout 20 s to avoid formation of cement lumps. Use a horizontal rotary motion toprevent any part of the sample or liquid from being thrown up and remaining separated from the rest of the solution enclosure as quickly as possible (in 1 min maximum) to avoid any appreciable lowering in temperature of the contents of the container. @ Is02008All rights reserved 5 ISO863:2008(E) After a period of 8 d or 15 d in the uniform-temperature enclosure, remove the container and filter the solution immediately under vacuum through the Buchner funnel (7.3) into the vacuum flask (7.5) using dry, double filter in temperature of the solution). Seal the vacuum flask immediately and let the filtrate cool to room temperature Ifthecementsatisfiesthetestat8d(see10.2),itisnotnecessarytocontinueto15d 9.2Determinationofthehydroxylionconcentration Shake the vacuum flask (7.5) to homogenize the filtrate and pipette 50 ml of the solution into the 250 ml beaker (7.6). Add five drops of methyl orange indicator (6.6) and determine the total alkalinity with the orange. Keep the titrated solution, A, for the determination of calcium oxide concentration (9.3). 1000×0