Alkali Fusion Methods

Sodium peroxide is a useful reagent for the fusion of polymer samples preparatory to analysis for chlorine [8, 9] and bromine. The polymer is intimately mixed with sodium peroxide in an open crucible or with a mixture of sodium peroxide and sucrose in a micro-Parr bomb. Chlorine can be determined after acidification with nitric acid [9]. In a method for the determination of traces of bromine in polystyrene in amounts down to 100 ppm bromine, a known weight of polymer is mixed with pure sodium peroxide and sucrose in a micro-Parr bomb, which is then ignited. The sodium bromate produced is converted to sodium bromide by the addition of hydrazine as the sulfate  

The combustion mixture is dissolved in water and acidified with nitric acid. Bromine 

Fusion with sodium carbonate is a very useful method for the fusion of polymers that, upon ignition, release acidic vapours, e.g., PE containing traces of chlorine or PVC, both of which, upon ignition, release anhydrous hydrogen chloride. To determine chlorine accurately in the polymer in amounts down to 5 ppm, hydrogen chloride must be trapped in a solid alkaline reagent (e.g., sodium carbonate). In this method, PE is mixed with pure sodium carbonate and ashed in a muffle furnace at 500 C. The residual ash is dissolved in aqueous nitric acid, and then diluted with acetone. This solution is titrated potentiometrically with standard silver nitrate. 

The combustion mixture is dissolved in water and acidified with nitric acid. The bromine content of this solution is determined by potentiometric titration with standard silver nitrate solution. 

X-ray on discs Chemical methods on same discs as used for X-ray analysis Chemical method on powder  

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Both the direct and the alcoholic alkali fusion methods gave recoveries of 90% or better with phenyl-containing silicones, the results obtained by the alcoholic alkali modification being generally higher. 

Halogen in organosilicon compounds may be either directly linked to silicon or may be part of a substituent group. Total halogen is usually determined by alkali fusion methods. Halogen attached directly to silicon is easily hydrolysable by aqueous alcohols and the halogen acid so produced can be estimated by direct alkali titration or by indirect procedures. 

Colson has described an alkali fusion method for the determination of down to 500 ppm of sulfur in polymers [13] (See Method 2.6 at the end of this chapter) in which the sulfate in the digest is determined by titration either with O.OIN sodium hydroxide or by photometric titration with 0.01 barium perchlorate. 

This is 8-hydroxy-5,7-di-iodoquinoline. The easiest method of assay is by the flask-combustion technique, using about 12 mg, 1 ml 0-02N thiosulphate = 0-0006616 g C9H5ONI2. It can also be determined by the general alkali-fusion method for organically combined iodine given under Chiniofon Sodium using 0-1 g of sample, 1 ml 0-lN thiosulphate = 0-003308 g. The U.S.P. uses the method for Chiniofon after heating the assay sample first with 1 ml of 95 per cent ethanol and then 15 ml of sodium hydroxide solution until the ethanol has been expelled, 1 ml O-OSN silver nitrate 0-009924 g. 

This is ethyl 10-(/>-iodophenyl)undecanoate. It can be assayed by the flask-combustion method using 30 mg, 1 ml 0-02N thiosulphate = 0 001388 g or the alkali-fusion method given under Chiniofon Sodium. 1 ml 0 1 N thiosulphate == 0-006939 g. In the U.S.P. the iodine is assayed as under Injection of Iodised Oil using 300 mg. 

Sophisticated instrumental techniques are continually being developed and gradually replace the classical wet chemistry analytical methods. Wet chemical analysis is destructive the sample is dissolved or altered. Nowadays the analyst is highly focused on instrumental methods and chemometrics. Yet, chemical work-up methods (e.g. hydrolysis with alcoholic alkali, alkali fusion, aminolysis, and transesterification, etc.) and other wet laboratory skills should not be forgotten. 

A different route proceeds by alkali fusion of the corrspondingly substituted naphthalic acid imide. This pathway parallels the synthesis of perylene tetracarboxylic acid diimide 70 (Sec. 3.4.1.1). The method is particularly suited to aliphatic amines. 

The method described above is essentially the same as that of Thiele,1 which has been patented by F. Bayer and Company.2 Hydroxyhydroquinone triacetate has also been obtained by acetylating hydroxyhydroquinone formed by the alkali fusion of hydroquinone.3... 

Abbasi [234] has described a spectrophotometric method employing N-p-methoxyphenyl-2,-furohydroxic acid for the determination of titanium in soils. In this method, the soil sample was subjected to alkali fusion. The ash was treated with nitric acid to adjust it to pH 2.0 and filtered prior to adjustment to 10 pM with respect to hydrochloric acid. Stannous chloride (5M) was added to the filtrate, and the chromogenic reagent was dissolved in chloroform. The chloroform extract was evaluated spectrophotometrically at 385 nm against the reagent solution as blank. Approximately 61 ppm of titanium was found in a soil sample by this method. 

The introduction of hydroxy groups is important in dye chemistry because it opens the door to azo dye formation, using phenols and naphthols, and provides an important aux-ochrome. Hydroxylation methods include alkali fusion, replacement of labile groups,... 

Typically, these will be alloys, rocks, fertilisers, ceramics, etc. These materials are taken into solution using suitable aqueous/acid media, according to solubility hot water, dilute acid, acid mixtures, concentrated acids, prolonged acid digestion using hydrofluoric acid if necessary, alkali fusion (e.g. using lithium metaborate), Teflon bomb dissolution. Fusion and bomb methods are usually reserved for complex siliceous materials, traditionally reluctant to yield to solubilisation. 

Hydroxylation. The main general method for the hydroxylation of aromatic compounds is the alkali fusion of sulfonic acids ... 

Sodium Tungstates.—The anhydrous normal tungstate, NajWOi, is prepared by the fusion method described for potassium tungstate (see p. 222), or by complete dehydration of the hydrates at 100° C. or over sulphuric acid. It may be obtained from the mineral wolframite by fusion with alkali as already described (see p. 202). 

Methods available for the dissolution of ruthenium metal involve alkali fusion under oxidizing conditions. The absence of complete experimental details makes repetition of these methods difficult. The following procedure is a modification of those of Antony and Lucchesi and of Charonnat and, excluding the period of overnight evaporation, takes about 3 hours. The precise stoichiometry of the fused-salt reaction is not known. All procedures must be carried out in a fume hood since chlorine and some ruthenium tetraoxide are produced. 

From Sulpho Benzoic Acid.— The most common method of preparing phenols is by the alkali fusion of the sulphonic acids, Sulpho benzoic acids will thus yield hydroxy benzoic acids. In case the sulpho benzoic acid has been made by direct sulphonation of benzoic acid the meta compound will result. If, however, we start with tolmne and sulphonate it we will obtain the ortho and para compounds. 

Graebe and Kraft showed that the methyl group of a methylated phenol can be transformed into carboxyl by a process describable as an oxidative alkali fusion, the oxidant being lead dioxide. They applied the method successfully to the three cresols, the three toluic acids, 2,4-dimethylphenol, and o-cresotinic acid (1, available from Eastman). A preparative procedure for the conversion of (1) into 2-hydroxyiso-phthalic acid (2) is as follows. A mush of 240 g. of potassium hydroxide pellets and... 

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