54 



A YEAR IN SCIENCE 



substances retains its own peculiar properties. The 

 particles of salt and the particles of iron can be easily 

 detected. A magnet held over the mixture draws out 

 the iron just as if the salt were not there. On the 

 other hand, the salt can be separated from the iron. 

 If the mixture is covered with water and then poured 

 through a filter, the particles of iron will remain on the 



paper in the filter. The 

 liquid which passes through 

 the filter is known as the 

 filtrate. By boiling this 

 filtrate, the water will 

 evaporate, and the salt will 

 remain in its original form. 

 Both substances have been 

 recovered in their original 

 form and no new substance 

 has been formed. If two 

 or more substances are 

 is placed together, and each 



paper 

 the funnel. 



Fig. 25. A filter 

 folded and placed in tl 



be e ak"fr' d T hTmtrltT" retains its original prop- 

 erties, the resulting sub- 

 stance is called a mechanical mixture. 



Chemical compounds. If iron filings and powdered 

 sulphur are thoroughly ground together in a mortar, 

 a yellowish green substance results. As in the case of 

 the salt and the iron this is again a mechanical mixture, 

 from which the sulphur and the iron can easily be 

 separated. 



