IO PRACTICAL AGRICULTURAL CHEMISTRY [20-22 



20. Washing on the Filter-paper. — The precipi- 

 tate on the filter-paper (17) can be readily washed by pouring 

 into the filter distilled water, allowing it to drain away, and 

 repeating the operation four or five times. Hot water is 

 best for this purpose, since it filters more rapidly than cold. 

 The stream of water from the jet of the wash-bottle should 

 be used for this purpose. 



21. In order to ascertain whether a precipitate is 

 thoroughly washed, it is necessary either to evaporate a 

 few drops of the water which- has passed through the filter, 

 or to test for some constituent present in the liquid which is 

 to be separated. In the present case, since the liquid will 

 be alkaline, the washing should therefore be continued 

 until the wash-water ceases to turn turmeric paper brown 

 (paragraph 28). 



22. Drying Precipitates. — Precipitates are usually 

 dried in a steam-oven (fig. 14), />. a copper oven hollow- 



