A short manual of analytical chemistry, qualitative and quantitative,--inorganic and organic . It is usually carried out in a vesselcalled a crucible, made of fire-clay. On the small scale, or for the purposesof analysis, fusion is generally conducted in porcelain crucibles; or, where thesubstances are such as would attack porcelain, in vessels of platinum or should be fused only in crucibles made of the latter metal. Apeculiar kind of fusion, called cupellation, is resorted to in the assay of goldand silver. The alloy to be assayed is wrapped in a piece of lead foil, andthe wh
A short manual of analytical chemistry, qualitative and quantitative,--inorganic and organic . It is usually carried out in a vesselcalled a crucible, made of fire-clay. On the small scale, or for the purposesof analysis, fusion is generally conducted in porcelain crucibles; or, where thesubstances are such as would attack porcelain, in vessels of platinum or should be fused only in crucibles made of the latter metal. Apeculiar kind of fusion, called cupellation, is resorted to in the assay of goldand silver. The alloy to be assayed is wrapped in a piece of lead foil, andthe whole is then heated in a little cup made of bone ash, called a cupel,when the lead and all impurities fuse and sink into the substance of the EVAPORATION—CRYSTALLISATION AND DIALYSIS. porous vessel, leaving the pure metal as a metallic button, which may thenbe weighed. The illustration (fig. n) shows a set of crucibles for fusion—a,being of fire-clay ; b, a platinum crucible; c, one of porcelain; and D, whatis called Rosis crucible, for heating substances in a current of hydrogen when. Fig. II. it is desired to prevent access of air, or to produce rapid reduction to themetallic state. IX. EVAPORATION consists in heating a fluid until the whole, or as much of it as may berequired, passes off in vapor. A solution thus treated until it has whollypassed into vapor is said to be evaporated to dryness, and the solidsubstance remaining is called the residue. Solutions containing any organic or volatile matter ought always to beevaporated on a water bath; that is, in a vessel exposed only to the heat ofboiling water, in which the temperature must always be below 212° Fahr.(100° C). With ordinary non-volatile or metallic substances in solutionthis precaution is unnecessary, and of no practical advantage. Evaporationmay be conducted slowly, without raising the fluid to its boiling point, whenit is called simple vaporisation; but when sufficient heat is applied, theevaporation takes
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Keywords: ., bo, bookcentury1800, bookdecade1890, booksubjectchemistryanalytic
