A YEAR IN SCIENCE 47 



by instructor only : Rub together in the mortar a few 

 crystals of potassium iodide with a few of mercuric 

 chloride. What evidence appears that a new substance 

 is formed ? 



Dissolve a few crystals of potassium iodide in water 

 in a test tube. In another dissolve about an equal 

 quantity of mercuric chloride. Warm water will hasten 

 solution. Pour a little of the potassium iodide solu- 

 tion into a third test tube, and gradually add mercuric 

 chloride solution to it. The red precipitate is the 

 same substance as was formed when the different kinds 

 of crystals were rubbed together. 



CHAPTER VII 



CHEMICAL PHENOMENA 



Exercise 24. Mechanical Mixture. 



Object: To demonstrate a mechanical mixture. 



Iron filings Wire gauze 



Salt Ring stand 



Magnet Glass stirring rod 



Beaker Mortar and pestle 



Evaporating dish Funnel 



Bunsen burner Filter paper 



Directions: Mix together in a mortar 2 grams of 

 salt and 2 grams of iron filings. By means of a magnet, 

 try to separate the iron from the salt. What is the 

 result? Now pour the contents of the mortar into a 

 beaker. Add 20 c.c. of water to the mixture, and with 



