Alkaline fusion

It is used for the preparation of indigo into which it is readily converted on alkaline fusion. 

Hydrolysis. The lactone is easily hydroly2ed by alkaUes to the corresponding salts of coumarinic acid or o-hydroxy-i j -cinnamic acid [495-79 ]. Coumarinic acid salts are odorless. Coumarinic acid and salts revert to coumarin upon acidification with inorganic acids. Alkaline fusion of coumarin yields salts of sahcyhc and acetic acids. 

In a process said to be operated in Britain castor oil is subjected to alkaline fusion under critically controlled conditions to produce a mixture of methyl hexyl ketone and w-hydroxydecanoic acid. Interaction of these two materials at higher... 

Kiss [8] examined various techniques for the efficient separation and preconcentration of boron from marine sediments. Alkaline fusion with potassium carbonate was used to render boron reactive, even in the most resistant silicate minerals. Fusion cakes were extracted with water and borate was isolated by Amberlite XE-243 boron-selective resin. Borate was determined spectrophotometrically, following elution with 2 mol L 1 hydrochloric acid. Either the carminic acid complex (620nm), formed in sulphuric acid (94%) or sulphuric acetic acid (1 4), or the azomethine hydrogen ion association complex (415nm) formed at pH5.2, were used for borate measurement. 

The synthesis of indigo by means of alkaline fusion of phenylglycine... 

M acid ORG chem NH2CioH5(OH)S03H A sulfonic acid formed by alkaline fusion of a disulfonic acid of a-naphthylamine used as a dye intermediate. em, as-3d Macquer s salt See potassium arsenate. mo kerz, s6lt ... 

Hydrothermal synthesis of the non-uniform silica gel used for preparative chromatography proceeds in a different fashion. Sodium silicate (IMa2Si03),1 obtained by alkaline fusion of very pure sand, is acidified to yield orthosilicic acid (Si(0H)4). This unstable acid initially dimerises then condenses further to yield a gel with a hydroxylated surface. Under conditions of controlled polymerisation, a hydrogel is obtained which is further calcinated to yield a very dense silica gel (xerogel). Some of the processes involved here are of the same type as those used to produce microspheres for analytical chromatography. 

Dihydroxybenzoic acid is most conveniently prepared by alkaline fusion of the disulfonic acid obtained by sulfonation of benzoic acid.1,2,3 It has also been prepared by alkaline fusion... 

Detection.—Apart from naturally occurring ores of vanadium, vanadium steels, and ferrovanadium, the commonest compounds of vanadium are those which contain the element in the pentavalent state, viz. the pentoxide and the various vanadates. The analytical reactions usually employed are, therefore, those which apply to vanadates. Most vanadium ores can be prepared for the application of these reactions by digesting with mineral acids or by alkaline fusion with the addition of an oxidising agent. When the silica content is high, preliminary treatment with hydrofluoric acid is recommended. Vanadium steels and bronzes, and ferrovanadium, are decomposed by the methods used for other steels the drillings are, for instance, dissolved in sulphuric acid and any insoluble carbides then taken up in nitric acid, or they are filtered off and submitted to an alkaline fusion. Compounds of lower valency are readily converted into vanadates by oxidation with bromine water, sodium peroxide, or potassium permanganate. 

The first important step is that of putting the sample (unknown) into solution. For metals and alloys, strong acids, such as HCI, HNCE, or aqua regia may be used. If the material is not fully dissolved by these adds, it should be fused, either with sodinin carbonate (alkaline fusion) or potassium add sulfate (acid fusion). Care should be exercised to make certain that no portion of the unknown is volatilized and thus lost during these procedures. 

The preparation of phenols by the hydrolysis of diazonium salts with hot aqueous acid, and by a recent milder procedure suitable for diazonium salts having additional acid-sensitive groups, is discussed in Section 6.7.1, p. 922, and illustrated in Expt 6.69. Although these methods enable an aromatic hydrocarbon system to be converted in good yield into a phenol via the corresponding nitro and amino derivatives, the shorter route involving the alkaline fusion of the sulphonic acid discussed above may often be preferred. 

A fully alkaline procedure for the determination of total Se in biological samples was described [17], that includes alkaline fusion, prereduction of Se(VI) to Se(IV) in alkaline medium, and H2Se generation in an alkaline solution, and ICP-AES determination. Alkaline fusion coupled with alkaline mode HG... 

Phloroglucinol is formed by alkaline fusion of many vegetable products, for instance, maclurin 1 or kino.2 It is also formed to a small extent by the fusion of phenol with sodium hydroxide,3 and to a larger extent by fusing resorcinol with sodium hydroxide.4 It has been produced by fusing 1,3,5-benzenetrisulfonic add with sodium hydroxide 5 and 3,5-dibromophenol with potassium hydroxide. The best yields, however, are obtained by boiling a dilute solution of triaminobenzene hydrochloride 7 or triamino-benzoic acid hydrochloride 8 with water. 

The ring contraction of bridged a-bromo ketone 581 1has been the subject of considerable synthetic application.112) The somewhat related behavior of lactam 59113) under conditions of alkaline fusion is also interesting.114) Diene 60 forms a crystalline maleic anhydride adduct, a dark purple picrate, and a brick red adduct with 1,3,5-trinitrobenzene. 

Heuser was also a pioneer in certain of his researches. He was one of the first to show that some types of oxidized cellulose, when treated with mineral acids, give carbon dioxide, thus indicating that carboxyl groups are present. In his studies on lignin, he educed evidence that this system might contain aromatic groups alkaline fusion of sprucewood lignin yielded protocatechuic acid and pyrocatechol, and Heuser and his coworkers obtained extensive (juantitative data in this area. Another early piece of work involved the preparation of purified xylan from straw. 

The hydroxylation of phenol to catechol and hydroquinone with H2O2, introduced in the 1970s, represented a major advance over earlier methods of production, which utilized the alkaline fusion of o-chlorophenol (catechol) and the stoichiometric oxidation of aniline with manganese dioxide (hydroquinone). The inorganic and organic wastes in both processes were of the order of several kg per kg of product. However, the hydroxylation of phenol too is not free of drawbacks one is the co-production of two chemicals, destined for two... 

Alkaline oxidizing fusion is an effective way of dissolution of metallic powders, particularly of metals resistant to direct wet acid treatment (Ru, Os, and Ir), but is rarely used for decomposition of complex noble metal samples because of low recoveries (e.g., 34—84 % Pt, Pd, and Au from silicate materials) [64]. Low stability of the complexes formed under dissolution (water, HCl) of the melt and difficulties with quantitative conversion of analytes into complexes of strictly defined composition (suitable for subsequent separation) limit the applicability of the alkaline fusion method. Hydroxocomplexes easily formed in the solutions can cause problems with quantitative separation and preconcentration of the metals, particularly when using ion-exchange chromatography. 

Although compounds of the platinum metals are commercially available, many workers, for reasons of economy, prefer to prepare them from the elements. Rhodium, one of the rarest and most expensive of the platinum metals, is not attacked by acids (even aqua regia), and its dissolution in alkaline fusion mixtures (e.g., fused sodium carbonate and potassium nitrate mixtures) or in molten salts (e.g., molten potassium hydrogen sulfate) is inefficient and tedious. Chlorination during heating yields a mixture of water-insoluble chlorides, but in the presence of sodium... 

ICP emission spectrometry (acid digestion or alkaline fusion prior to solubilisation). In flame-based atomic absorption, the most favourable medium is hydrochloric acid, generally leading to easily atomisabic salts. 

The sample submitted for measurement is introduced into the equipment in liquid form. Consequently, solid samples such as catalysts must be converted into liquids, via acid digestion, or alkaline fusion dissolved in acid solution. 

The preparation of the sample consists of dissolving the solid sample, adding the internal standard and diluting so as to create a suitable salt level in the solution to be introduced into the plasma. The time required for this preparation will depend on the complexity of the composition and the physical and chemical characteristics of the catalyst. Conversion into solution form using the alkaline fusion method can be carried out in 30 minutes, whereas solubilisation via acid attack with heating on a hot plate may require a period of several days. The choice of method to achieve a solution depends not only on the chemical nature of the sample but also on the elements to be ascertained and above all the detection limit sought. 

Hydrogen peroxide is an efficient oxidizing agent (Section 16-3), particularly in alkaline solution. The excess peroxide is usually decomposed by boiling the alkaline solution the process is hastened by a number of catalysts, including nickel salts, iodide, and platinum black. Schulek and Szakacs removed the excess with chlorine water and then added potassium cyanide to destroy the excess chlorine. Examples of oxidation reactions are the oxidation of Cr(III) to chromate in 2Af sodium hydroxide, Co(II) to Co(III) in bicarbonate solution, Mn(II) to Mn(IV) in the presence of tellurate, and Fe(II) to Fe(III) followed by titration with ascorbic acid. Sodium peroxide, an even more vigorous oxidant, is applied in alkaline fusions. The fusion of chromite ore to form chromate has been critically studied, ... 

Tuckerman and collaborators state that chloric acid is to be preferred to the more widely used sulphuric acid or sulphuric-nitric acid digestions or alkaline fusions recommended for the determination of arsenic in organic compounds. Excess chloric acid is easily removed by boiling to leave a perchloric acid solution of inorganic As(V). Rapid micro and semi-micro methods for the determination of arsenic based on chloric acid digestion are described. 

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