Hydrochloric acid gravimetric analysis

Caution. Heating, especially to dryness, may result in a violent explosion. For analysis the sample is dissolved in excess 1 N nitric acid at room temperature. Then silver is determined gravimetrically as silver chloride by precipitation with hydrochloric acid. Anal. Calcd. for [Ag(C6H6N)2]C104 Ag, 29.52. Found Ag, 29.39. ... 

Section 12 of ASTM Chemical Analysis of Gypsum and Gypsum Products (C 471) deals with the determination of sulfur trioxide in gypsum gravimetrically. Basically, gypsum is dissolved in dilute hydrochloric acid, and sulfate is precipitated as barium sulfate by addition of hot/boiling barium chloride solution. 

For the analysis of rhenium, the sample is fused with sodium peroxide and rhenium precipitated from hydrochloric acid solution as Re2S7 by hydrogen sulfide. The precipitate is dissolved in aqueous sodium peroxide and from dilute sulfuric acid solution, rhenium is determined by electrodeposition.8 Chlorine is determined gravimetrically by fusion of the sample with a sodium carbonate/ sodium nitrate mixture (95 5) in a platinum crucible and then precipitating as silver chloride. 

Actual electrolyte compositions were measured b gravimetric analysis of total sulfur species present after oxidation with hydrogen peroxide. A sample of membrane material was weighed and then dissolved in water. The insoluble matrix materials were filtered and the filtrate treated with excess hydrogen peroxide which oxidizes all sulfur species to sulfate. It was assumed t t oidy sulfur in the form of sulfide was present in the membrane under run conditions. This solution was then acidified with hydrochloric acid to decompose the carbonate to carbon dioxide and water. The solution was then boiled to de-gas the mixture... 

The deterrnination of the soluble or available sodium aluminate presents difficulties because sodium aluminate begins to hydrolyze to the insoluble alumina trihydrate in water. The degree of hydrolysis depends on concentration, temperature, and time. It is therefore necessary to use a method of analysis that simultaneously affords control of the hydrolysis and gives the amount of available sodium aluminate encoimtered. This is best done by extracting the soluble alumina using sodium hydroxide solutions and subsequently deterniining the alumina content by gravimetric methods or titration with EDTA or hydrochloric acid (16). 

For classes (a)-(c) and for SiC, the main analysis solution is prepared via a low flux/sample ratio fusion or, in the case of alumina, a sinter at 1200°C. The flux used is a mixture of fusion mixture (NaKCOs) and boric acid a lower flux/sample ratio is used for aluminous materials, and a larger flux/ sample ratio is used for zircons. The melt is dissolved and the silica is dehydrated in a mixture of hydrochloric and sulfuric acids with the assistance of polyethylene oxide. The main silica is then determined gravimetrically. Other constituents, including residual silica, are determined on the filtrate combined with the residue remaining after the gravimetric silica determination. 

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