An introduction to practical chemistry : including analysis . iently effected in Berlin porcelain evaporatingbasins, either on a sand-bath or over a lanp, a loosecover of filtering-paper being placed over it, if neces-sary, to prevent particles of dust falling into the must be taken, in quantitative experiments, thatno loss is occasioned by spurting, and on this account,it is safer not to allow the liquid absolutely to a saline solution has to be evaporated to dryness,it often becomes covered, when concentrated, with apellicle of solid matter, preventing the escape of the
An introduction to practical chemistry : including analysis . iently effected in Berlin porcelain evaporatingbasins, either on a sand-bath or over a lanp, a loosecover of filtering-paper being placed over it, if neces-sary, to prevent particles of dust falling into the must be taken, in quantitative experiments, thatno loss is occasioned by spurting, and on this account,it is safer not to allow the liquid absolutely to a saline solution has to be evaporated to dryness,it often becomes covered, when concentrated, with apellicle of solid matter, preventing the escape of thesteam, which, being thus confined, occasionally causessome of the mixture to be projected violently from thebasin. The best way of avoiding this is to stir the mix-ture constantly with a glass rod, from the time whenthe pellicle begins to form, until it is evaporated todryness. Fig. 91. 644. It is oftenadvisable, and inthe case of manyliquids, as thosecontaining organicmatter, necessary,to evaporate overa water-bath; bythis means the heatis never allowed to. raise higher than 212°. For thispurpose, a common saucepan, or almost any vessel used 214 OPERATIONS IN ANALYSIS. for boiling water in, maybe employed, placing the dishcontaining the solution over the top, as shown in Figure91, so as to expose it to the action of the steam. Forthe laboratory, a convenient form of water-bath is shownin Figure 92 ; it may be made of copper or zinc plate, Fig. 92. 0800 oooo
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectchemistry, bookyear18
