276 Domestic Science 



Fig. 90. The filter-paper thus prepared will exactly 

 fit a funnel, if the sloping sides of the latter make an 

 angle of 60 with each other at all points. Common 

 funnels are not usually so well made as this, hence, 

 to make the conical filter fit the funnel, it is frequently 

 necessary to make the second fold in such a way that 

 the semi-circle is not exactly bisected. The paper is 

 then opened out so that a cone with broader apex or 

 otherwise, as required, may be obtained, according to 

 the bluntness or sharpness of the angle of the funnel. 

 Wet the filter with a few drops of distilled water and 

 press it firmly against the interior of the funnel. Pour 

 the warm liquid from the beaker through the funnel, 

 supporting the latter on the ring of a retort stand, and 

 allowing the liquid which passes through the filtrate 

 to run into a clean beaker placed underneath the funnel. 

 The filtrate should be quite clear. When almost all 

 the water has been poured through the filter add about 

 20 c.c. of distilled water to the residue left in the beaker, 

 heat it to boiling and again filter. Repeat the addition 

 of water and filtering at least twice. Test whether any 

 soluble matter is left in the filtrate passing through by 

 evaporating a drop to dryness on a watch-glass and 

 observing whether any residue remains. When the 

 production of no appreciable quantity of residue as a 

 result of evaporation occurs, complete the draining, 

 allowing the liquid adhering to the filter-paper to 

 drain into the beaker, and then transfer the contents of 

 the latter to a weighed porcelain dish. This transfer- 

 ence may be done in two or more operations, if the 

 quantity of filtrate is more than enough to fill the dish. 

 Wash out the beaker with small quantities of distilled 

 water and add the washings to the solution in the 

 porcelain dish. Evaporate the contents of the dish 



