BS ISO 127:2018 pdf download.Rubber, natural latex concentrate — Determination of KOH number
1 Scope
This document specifies a method for the determination of the KOH number of natural rubber latex concentrate which is preserved wholly or in part with ammonia.
The method is applicable to latices containing boric acid.
The method is not applicable to latices preserved with potassium hydroxide. It is not necessarily suitable for latices from natural sources other than Hevea brasiliensis, or for latices of synthetic rubber,compounded latex, vulcanized latex or artificial dispersions of rubber.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 123, Rubber latex — Sampling
ISO 124, Latex, rubber — Determination of total solids content
ISO 125, Natural rubber latex concentrate — Determination of alkalinity
ISO 976, Rubber and plastics — Polymer dispersions and rubber latices — Determination of pH
ISO 1802, Natural rubber latex concentrate — Determination of boric acid content
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1 KOH number
<rubber latex> number of grams of potassium hydroxide equivalent to the acid radicals combined with ammonia in latex containing 100 g of total solids
[SOURCE: ISO 1382:2012, 2.249, modified — Note 1 to entry has been deleted. ]
4 Reagents
During the analysis, use only reagents of recognized analytical grade and only distilled water free of dissolved carbon dioxide, or water of equivalent purity.
4.1 Potassium hydroxide, standard volumetric solution, c(KOH) = 0,1 mol/dm 3 , carbonate-free.
4.2 Potassium hydroxide, standard volumetric solution, c(KOH) = 0,5 mol/dm 3 , carbonate-free.
4.3 Formaldehyde, 45 g to 50 g in 1 dm 3 of solution [c(HCHO) = 1,5 mol/dm 3 to 1,67 mol/dm 3 ], acid-free, prepared by diluting concentrated formaldehyde with water and neutralizing with 0,1 mol/dm 3 potassium hydroxide solution (4.1), using as indicator the faint pink colour of phenolphthalein.
Annex A describes the method to determine the concentration of the formaldehyde solution.
5 Apparatus
Standard laboratory glassware, plus the following.
5.1 pH-meter, in accordance with ISO 976 but capable of being read to 0,01 units.
5.2 Glass electrode, of a type suitable for use in solutions of pH up to 12,0.
5.3 Mechanical stirrer, with earthed motor and glass paddle, or magnetic stirrer.
An automatic titrator may be used provided that it has been proven to give the same result as the standard method.
BS ISO 127:2018 pdf download
