An introduction to practical chemistry : including analysis . the ring of a retort stand (Fig. 85)(for which the form shown at a is very convenient), oron a perforated block of wood placed on the glass in-tended to catch the filtered solution (169), the hole beingmade to fit the funnel, as shown in the section (Fig. 86).636. The solution to be filtered should be pouredgently down a glass rod (Fig. 85), so as to fall on one ofthe slanting sides of the filter, and not into the apex, asthat would endanger the bursting of the paper, andcause splashing. When the whole of the mixture hasbeen poured
An introduction to practical chemistry : including analysis . the ring of a retort stand (Fig. 85)(for which the form shown at a is very convenient), oron a perforated block of wood placed on the glass in-tended to catch the filtered solution (169), the hole beingmade to fit the funnel, as shown in the section (Fig. 86).636. The solution to be filtered should be pouredgently down a glass rod (Fig. 85), so as to fall on one ofthe slanting sides of the filter, and not into the apex, asthat would endanger the bursting of the paper, andcause splashing. When the whole of the mixture hasbeen poured on the filter, fresh water should not beadded for the purpose of washing, until the whole ofthe solution has passed through ; then, by means of awashing-bottle (94), the precipitate left on the filter iswell washed; the current of water being applied firsttowards the upper part of the filter, and directed gra- 18* 210 OPERATIONS IN ANALYSIS. dually downwards (Fig. 87). When the filter has beenthus nearly filled up with water, allow the whole to run Fig. Fig. 88. through before adding any more, and then repeat thewashing, until a drop of the filtered liquid leaves nofixed residue when evaporated and ignited on platinumfoil. If the precipitate, while standing in the filter,cakes together into lumps, these must be broken up bydirecting upon them a strong current of water from thewashing-bottle, as otherwise the water would not pene-trate them, and some of the soluble matter would escape removal. 637. It is sometimes neces-sary to keep the mixture hotduring filtration, to preventany of the soluble ingredientssolidifying: this may be donevery conveniently, by placingthe funnel in a zinc or copperbox of the form shown in , which may be kept full ofhot water, andboiling, if neces-sary, over a lamp. 638. The liquid is generallyfiltered into a beaker glass, and
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectchemistry, bookyear18
