Hydrochloric or acetic acid

For binder preparation, dilute hydrochloric or acetic acids are preferred, because these faciUtate formation of stable silanol condensation products. When more complete condensation or gelation is preferred, a wider range of catalysts, including moderately basic ones, is employed. These materials, which are often called hardeners or accelerators, include aqueous ammonia, ammonium carbonate, triethanolamine, calcium hydroxide, magnesium oxide, dicyclohexylamine, alcohoHc ammonium acetate, and tributyltin oxide (11,12). 

The mechanism of cyclization of diaminopyrimidines by nitrous acid appears not to have been studied in detail. For the preparative procedure an aqueous solution of alkaline nitrite is treated with the diaminopyrimidine either in the form of a salt or with simultaneous addition of hydrochloric or acetic acid. The first phase of the reaction is usually carried out at 0°C, in some cases the reaction being terminated by heating to 50-60°C. With diaminopyrimidines which are sparingly soluble in water, the reaction was carried out in an organic solvent using amylnitrite. Excess nitrous acid can possibly attack the amino groups present. This was employed in some cases for the preparation of the hydroxy derivatives. ... 

The atmospheric pollution prevailing in special industrial or laboratory locations may induce more severe corrosion, e.g. the vapours from concentrated hydrochloric or acetic acid will etch tin, and moist sulphur dioxide will produce a sulphide tarnish, as will hydrogen sulphide at temperatures above about 100°C. The halogens attack tin readily. The commonly used volatile corrosion inhibitors are without adverse action although the benefit derived from their use is doubtful. 

Milder reductions with hydriodic acid can be accomplished by using more dilute hydriodic acid, or solutions of hydrogen iodide prepared from alkaline iodides and hydrochloric or acetic acid in organic solvents [22S],... 

Marsden78 did not attempt to separate mixtures of monosaccharides by gel chromatography the small differences in Ka among the different sugars indicate that separation could be achieved only on very large columns by use of the eluants used by this author, namely, deionized water and buffers of ionic strength 0.05 (pH 7-8) composed of 2-amino-2-(hydroxymethyl)-l,3-propanediol (Tris) and hydrochloric or acetic acid. 

Arsenic trisulphide is not dissolved by dry liquid hydrogen sulphide.8 The precipitated sulphide obtained by the action of hydrogen sulphide on solutions of arsenious oxide in aqueous hydrochloric or acetic acid is found to contain an amount of sulphur in excess of that required by the formula As2S3, but which cannot be extracted with carbon disulphide. This has been attributed to the formation of a hydrosulphide since, if the precipitate is dried in a vacuum and then heated at 115° C., hydrogen sulphide is evolved. The products vary in composition, but that produced in presence of hydrochloric acid approximates to 16As2S3.H2S and that from acetic acid solutions to 8As2S3.H,S.9... 

A convenient method of preparing arsenic pentasulphide is to boil arsenic pentoxide with piperazine, when a solution is obtained which, by the prolonged action of hydrogen sulphide, yields the compound As2S5.3C4H10N2.3H2S if this is treated with cold dilute hydrochloric or acetic acid, crystals of arsenic pentasulphide are formed.6... 

Roots of Scopolia atropoides Hydrochloric or acetic acid Potassium carbonate... 

Alkaloids fraction was obtained from roots by extraction with benzene. First of all the atropine was isolated. Then after isolation of the atropine, the extract containing the scopolamin and other alkaloids was washed by slightly acidic solution (this solution was acidified with the hydrochloric or acetic acid). To the acidic solution the potassium carbonate was added, then scopolamin was extracted with chloroform, ether or their mixture. The organic extracts were combined and evaporated under reduce presser. Concentrated residue was washed with water, filtered and dried. 

A number of other authors have also nitrated aromatic amines, acting with sodium nitrite on the amine dissolved in hydrochloric or acetic acid. Thus, tri-phenylamine and its methyl derivative in acetic acid were nitrated by Haussermann and Bauer [159], and Rupe, Braun and Zembruski [160] and Tsuruta and Oda [161] nitrated derivatives of dimethylaniline in hydrochloric acid to yield mononitro products. 

The precipitate is insoluble in dilute hydrochloric or acetic acids (though precipitation does not take place from such media). Hot, concentrated nitric acid or aqua regia dissolve the precipitate, when white sulphur remains ... 

Mercaptopyrazine in aqueous hydrochloric or acetic acids was chlorinated to give the sulfonyl chloride which with excess liquid ammonia gave 2-sulfamoyl-pyrazine (1006, 1153). Direct sulfonation of the pyrazine ring has never been reported (819) but 2-sulfopyrazine (17) has been prepared from 2-chloropyrazine and aqueous sodium sulfite at 150° (819), and from 2-fluoropyrazine and aqueous sodium sulfite at reflux for 2 hours (882, 884). 2-Amino-3-mercaptopyrazine in aqueous sodium hydroxide with concentrated ammonia and sodium hypochlorite has been shown to give 2-amino-3-sulfamoylpyrazine (1101). 

The corresponding iodide is prepared in a similar manner to the bromide. It may be crystallised from benzene or acetone and melts at about 80° C. It is more readily decomposed than the bromide, and hydrochloric or acetic acids break it down to allyl alcohol and mercuric salts. The presence of the two hydroxyl groups has been shown by the fact that the iodide yields a dibenzoyl derivative, M.pt. 100° C. When the iodide is treated with iodine at 40° C. a liquid iodohydrine is obtained. 

For performing a Traube synthesis, two methods have been found best. In the first, the selected pyrimidine (60) was dissolved in water as its hydrochloride (or in dilute hydrochloric or acetic acid) and stirred with sodium nitrite at 0 ° C, after which it was often (but not necessarily) heated at 60 -100° ... 

Nuclear iodination is generally carried out by using iodine in the presence of Hl-acceptors (or of H202) or by using IC1 in hydrochloric or acetic acid. 

The rearrangement of a-acetylenic alcohols into a-p ethylenic carbonyl derivates has been extensively studied. Different catalysts have been proposed acid catalysts such as sulfuric, hydrochloric or acetic acids which give rise to unselective rearrangements [1,2] and more recently, oxo derivatives of vanadium, molybdenum or tungsten in liquid phase [3]. 

Because shellac articles are frequently not fully cured, finished products of this kind may be tested as follows place a cut up sample of about 1 g in approximately 15 ml of boiling alcohol for a period of about one hour, and allow the sample to cool. Then boil down the extractive and test for shellac by adding diluted hydrochloric or acetic acid to the alcoholic extract in a test tube then heat until the sample becomes clear. Upon addition of ammonia, shellac turns dark violet, and if it was chlorine-bleached, it turns brown. 

So far their use has been confined to the synthesis of peptides [208, 210, 211] and penicillins [212, 213]. The derivatives with a-amino acids are stable, h hly crystalline compounds, well suited for use in conventional or soUd-phase [214] peptide synthesis. Removal of these groups is brought about by hydrolysis with dilute hydrochloric or acetic acid. 

H. is produced by - alkoxylation of alkali-cellulose suspended in solvents, such as acetone, isopropanol or tcrt.butanol 0.8-1.5 moles of alkali per AGU are necessary. To decrease viscosity, the alkali-cellulose is degraded by aging (- cellulose) before reaction or by adding hydrogen peroxide to the alkaline reaction mixture. For better efficiency, the addition of ethylene oxide is carried out in two stages. After the first reaction step, only catalytic amounts of alkali are necessary. Reaction takes place in 1-4 h at 30-80 °C and is stopped by neutralization with hydrochloric or acetic acid. Salts are removed by washing with alcohol/water mixtures. If retarded dissolution in water is desired, the wet product is treated with glyoxal. 

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