BS ISO 125-2020 pdf free download – Natural rubber latex concentrate — Determination of alkalinity.
This document specifies a method for the determination of the alkalinity of natural rubber latexconcentrate.
The method is not necessarily suitable for latices from natural sources other than Hevea brasiliensis orfor synthetic rubber latices, compounded latex, vulcanized latex or artificial dispersions of rubber.
NOTE A method for the determination of the alkalinity of polychloroprene latex is specified in IS0 13773.
2Normative references
The following documents are referred to in the text in such a way that some or all of their contentconstitutes requirements of this document. For dated references, only the edition cited applies.Forundated references, the latest edition of the referenced document(including any amendments) applies.
ISO 123,Rubber latex —Sampling
ISO 976,Rubber and plastics — Polymer dispersions and rubber latices — Determination of pH
3 Terms and definitions
No terms and definitions are listed in this document.
lSO and IEC maintain terminological databases for use in standardization at the following addresses:-ISo online browsing platform: available at https://www.iso.org/obp
—IECElectropedia: available at http://www.electropedia.org/
4 Principle
A test portion of latex concentrate is titrated with acid to pH 6 in the presence of a stabilizer to preventcoagulation, either electrometrically or with methylred as a visual indicator.The alkalinity is calculatedfrom the quantity of acid required.
5 Reagents
Use distilled water or water of equivalent purity， wherever water is specified, and reagents ofrecognized analytical quality.
5.1 Stabilizer solution: 5 % (by mass) solution of a non-ionic stabilizer of the alkyl phenolpolyethylene oxide condensate type. Before use, the pH of the solution shall be adjusted to a value of6,0 ± 0,05.
5.2 Sulfuric acid, c(H,SO4) = 0,05 mol/dm3, or hydrochloric acid, c(HCIl) = 0,1 mol/dm3, standardvolumetric solution.
5.2.1 Standardization of sulfuric acid, standardize 0,05 mol/dm3 H,SOg by pipetting 10 cm3 of0,05 mol/dm3 Na,COg solution (5.5) into a flask and titrating with 0,05 mol/dm3 HlySo , using methylorange (5.4) as indicator.
5.2.2 Standardization of hydrochloric acid, standardize 0,1 mol/dm3 HCl by pipetting 10 cm3 of0,05 mol/dm3 NazCO3 solution(5.5) into a flask and titrating with 0,1 mol/dm3 HCl,using methyl orange(5.4) as indicator.
5.3Methyl red,0,1 % solution in ethanol of minimum purity 95 % (by volume).
5.4 Methyl orange,0,1 % solution in ethanol of minimum purity 95 % (by volume).
5.5Sodium carbonate solution, c(NazCo3) = 0,05 mol/dm3.
Dry the NazCO3 used to prepare this solution at 120 °C± 5 °C for 2 h before preparing the solution.
6Apparatus
Standard laboratory equipment together with:
6.1 Electrical stirrer, with earthed (grounded) motor and non-metallic propeller-type blade,ormagnetic stirrer.
6.2pH-meter, equipped with a combined electrode suitable for use in solutions up to pH 12, a5specified in Iso 976, and capable of being read to 0,02 pH-units.
6.3Balance, capable of being read to 0,01 g.
7Sampling
Carry out sampling in accordance with one of the methods specified in ISO 123.
Procedure
8.1General
Carry out the determination in duplicate.
Add, while stirring,10 cm3 of stabilizer solution (5.1) to about 200 cm3 of water in a 400 cm3beaker.Weighing to the nearest 10 mg, add between 5 g and 10 g of the latex concentrate by difference from aweighing bottle and stir until thoroughly mixed.
Ensure that the latex is added so that none runs down the side of the beaker (which could result in lossof ammonia) or down the side of the weighing bottle.BS ISO 125 pdf download.