Elementary qualitative chemical analysis - Tapa blanda

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1895 Excerpt: ...compound sodium hydrogen arsenate (Na2HAs04.12H2O), dissolved in water. The tests described in the following paragraphs, except 162, give the same ultimate result with both arseniows and arsenic compounds. As a rule, however, the reactions proceed slowly with arsenic compounds, since the first stage consists in their conversion into arseniotts compounds. Arsenic compounds are converted into arsenic-Ms by boiling them with H2S03, strong HCI, or some other reducing agent. Arseniows compounds are oxidised into arsenic compounds by being heated with HN03, or with other oxidising agents. 156. Hydrogen sulphide (H2S) produces in neutral solutions of arsenious compounds only a yellow coloration; but on the addition of hydrochloric acid (HCI) to this cold liquid, a light-yellow flocculent precipitate (As2S3) forms immediately. Filter off some of the As2S3, and show that it is insoluble in boiling strong HCI, but soluble in potassium hydrate (KHO) and in ammonium sulphide (Am2S); from these F solutions it is reprecipitated on the addition of HC1 in In cold acidified solutions of arsenic compounds H2S produces no precipitate. But if strong HC1 is added and the solution is boiled, H2S causes in the boiling solution first a precipitate of white S and then of yellow As2S3. The complete precipitation of arsenic solutions by H2S is most rapidly effected by first adding sulphurous acid (H2S03) to the solution until it smells of S02, and then boiling the liquid until S02 is no longer smelt. The arsenious compound thus produced is readily and completely precipitated by H2S in the cold solution. 157. Beinsch's test.--Several narrow strips of sheet copper are cleansed with sand-paper. They are then boiled in the arsenious solution, which has been previously acidified by dilute...