Physical Properties of Water 275 



of similar shapes to those illustrated in Fig. 89 may be 

 obtained. 



190. Matter in suspension in water, i.e. not dis- 

 solved, but merely floating about, may be removed by 

 nitration, a much simpler process than that of distilla- 

 tion. Porous materials, such as blotting-paper, filter- 

 paper, unglazed porcelain, and layers of sand, are among 

 the filtering materials in common use. To show the 

 applicability of the process to a simple case, try 



Fig. 90. 



EXPERIMENT 126. Weigh out 10 g. of whiting and 

 10 g. of common salt. Thoroughly mix these by grind- 

 ing them together in a mortar. Test the efficiency of 

 your mixing as follows : Weigh out 5 g. of the mixture 

 and put this weight into a beaker with about 100 c.c. 

 of distilled water. Heat this till the water reaches 

 boiling-point. While the heating is proceeding fold 

 a circular sheet of filter-paper exactly in half, fold the 

 doubled paper again into half, and then open out the 

 quarter- circle of paper into the shape of a cone by 

 inserting the finger so that three thicknesses of the 

 paper are on one side of the finger and one thickness 

 on the other. The stages of folding are illustrated in 



182 



