Qualitative chemical analysis and laboratory practice / by T.E. Thorpe and M.M. Pattison Muir.

  • Thorpe, T. E. (Thomas Edward), 1845-1925.
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: Qualitative chemical analysis and laboratory practice / by T.E. Thorpe and M.M. Pattison Muir. Source: Wellcome Collection.

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    ^32 yjppendicss. dioxide added, and the dish again heated nearly to boiling with constant stilling ; the arsenious oxide is thus converted into arsenic pentoxide The acid is again allowed to cool and transferred to a retort of looo c.c. capacity and distilled, a few platinum-clippings being added to moderate the violent succussivc character of the ebullition. The retort must be supported over the naked flame ; this should be so arranged as to heat the sides of the retort more than the bottom, whereby the tendency to ‘ bump ’ is diminished. The neck of the retort may dip directly into the condensing flask ; the latent heat of sulphuric acid vapour IS so small that no water is needed to assist the condensation. 4. Potassium hydrate. Caustic potash is not readily obtained inire. The commercial substance may be partially purified by dis- .solving it in strong alcohol in a stoppered bottle, allowing the insoluble matters to subside, drawing off the clear .supernatant dark-brown liquid by means of a .syphon, and evaporating it in a silver basin until dense u hite vapours make their appearance. The resinous matter formed by the action of the alcohol should be skimmed off the surface by a silver spatula or .spoon, after which the oily liquid is poured on to plates, where it solidifies ; it is quickly broken up and preserved in well- smppered bottles. Its solution should be kept in bottles free from lead, since the alkali rapidly attacks flint-gla.ss, dissolving out the lead oxide. 1 he purest form of the hydrate is obtained by igniting a mixture of one part of jrure nitre with two parts of thin copper foil cut in small pieces ; the mixture is arranged in alternate layers in a covered copper crucible and heated for half an hour to a moderate red heat. When cold the mass is dissolved out by boiling water, and the turbid solution poured into a long stoppered cylinder, in order that the copper oxide may subside. The clear solution is removed by a syphon and rapidly boiled down in a silver basin to the state of the oily hydrate. Instead of metallic copper ferric oxide may be employed. This is prepared by igniting ferrous oxalate ; it is mixed with the nitre in the same proportion as the copper. Through the lid of the crucible runs a tube passing nearly to the bottom, through which a stream of hydrogen is delivered. The crucible is exposed to a low red heat for about an hour; when cold the mass is boiled out with water, and the iron oxide allowed to settle. The clear solution of the hydrate is then evaporated in a silver basin as above described. The ferric oxide may be used repeatedly for the same operation. 5. Sodium hydrate. Very pure caustic soda may be obtained by the action of the metal on water. The solution is prepared by floating a silver dish containing a small quantity of water in a basin of cold