ISO 7780 pdf download.Rubber and rubber latices — Determination of manganese content — Sodium periodate photometric methods
1 Scope
This International Standard specifies photometric methods for the determination of manganese, after oxidation with sodium periodate, in rubbers and rubber latices. Both methods contain provisions for analysis of chlorine-containing rubber. Clause 3 specifies a method for compounded or vulcanized rubbers which is not affected by heavy loadings of fillers such as synthetic and natural silicates or calcium carbonates in various forms, or by the presence of compounding ingredients which form an insoluble phosphate under the conditions of the test. Clause 4 specifies a method for raw and compounded natural and synthetic rubbers and latices which do not contain heavy loadings (more than about 1 0 %) of inert silicate fillers or any ingredient such as titanium dioxide which under the conditions of test will form an insoluble phosphate.
2 Normative references
The following standards contains provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 1 23:— 1 ) , Rubber latex — Sampling. ISO 1 24:1 997, Latex, rubber — Determination of total solids content. ISO 1 795:1 992, Rubber, raw, natural and synthetic — Sampling and further preparative procedures. ISO 4793:1 980, Laboratory sintered (fritted) filters — Porosity grading, classification and designation.
3 General method (for samples not affected by heavy loadings of fillers)
3.1 Principle In the presence of chlorine, digestion with sulfuric acid is required, followed by reaction with nitric acid. This procedure is carried out in a Kjeldahl flask. If silicates are present, the digested test portion is treated with sulfuric and hydrofluoric acids to volatilize any silicon as silicon tetrafluoride. In the absence of chlorine, the rubber is ashed in a platinum crucible and treated with sodium fluoroborate. After either procedure, the manganese is oxidized to permanganate by boiling with sodium periodate. The manganese concentration is determined by spectro- photometric measurement at 525 nm. 3.2 Reagents During the analysis, wherever possible, use only reagents of recognized analytical grade, suitable for use in trace-metal analysis, and only stabilized water (see 3.2.5). 3.2.1 Sodium fluoroborate. If analytical grade is not available, prepare this reagent as follows. Dissolve 1 1 0 g of technical-grade sodium fluoroborate in 1 00 cm 3 of water warmed to about 35 °C. After filtering through a filter paper, cool the solution to room temperature and add 1 00 cm 3 of 96 % ( V / V ) ethanol whilst stirring. Filter off the crystalline precipitate on to a filter paper in a Buchner funnel and drain thoroughly under slight vacuum, then transfer to a shallow porcelain or glass dish and dry at about 50 °C under vacuum.
3.5.2.1 Ashing the test portion in the absence of chlorine
Transfer the test portion to a weighed platinum crucible (3.3.2) which is supported in the hole in the heat-resistant, thermally insulating board (3.3.3). Start the preparation of a blank solution at the same time, using a similar crucible but omitting the test portion, and continue by treating the test portion and the blank in an identical manner. Heat the crucible and contents with a gentle gas flame until a dry carbonaceous residue remains and then transfer the crucible to the muffle furnace (3.3.4) maintained at a temperature of 550 °C ± 25 °C and heat until all carbon has been oxidized. Allow the crucible to cool in a desiccator, weigh it to determine the mass of ash and then, from a fine pipette, add an amount of sulfuric acid (3.2.3) drop by drop round the walls of the crucible just sufficient to moisten the ash. Heat gently until fuming ceases and then again at about 550 °C for a few minutes. Repeat the treatment of the ash with the sulfuric acid, adding the acid as before from a fine pipette, heating gently until fuming ceases, and then again at about 550 °C for a few minutes. After cooling again to room temperature, add to the crucible 8 parts by mass of sodium fluoroborate (3.2.1 ), up to a maximum of 8 g, to 1 part by mass of the ash. Gently heat the crucible in a fume cupboard until fusion is complete, and then more strongly until the molten material becomes clear, or until no further reaction takes place and any insoluble matter is dispersed in the melt.