APPENDIX. 



93 



caused by its union with the acid. Caution should be ob- 

 served in pouring this acid into water, and care be taken 

 not to pour the water into the acid. 



(16.) Exhibit a piece of phosphorus, and show how 

 easily it can be set on fire. 



(17.) Rub a match, and show how the friction causes it 

 to inflame. 



(18.) Place a little phosphorus on a dry plate, set it on 

 fire, and quickly place over it a receiver, or wide-mouthed 

 bottle. The white fumes that rise are phosphorus pent- 

 oxide. Water unites with this oxide to form phosphoric 

 acid. 



(19.) Place some manganese dioxide (black oxide of 

 manganese) in a glass flask or test-tube, pour over it some 

 strong hydrochloric acid, and apply a gentle heat. Chlo- 

 rine, a yellowish-green gas, will be disengaged. By means 

 of a properly bent glass tube reaching to the bottom of a 

 bottle, this gas may be collected by displacement. Im- 

 merse in it a lighted taper or splinter, and the light will be 

 extinguished. A red rose moistened and placed in a bot- 

 tle of chlorine will be bleached in a short time. 



(20.) Heat in a test-tube, or small flask, a little potas- 

 sium iodide, manganese dioxide, and sulphuric acid. The 

 beautiful violet-colored vapor of iodine will be disengaged. 

 Substitute potassium bromide for the potassium iodide, and 

 the deep-red vapor of bromine will be given off. 



(21.) Drop a small piece of potassium on the surface of 

 water. The metal will burn with a violet flame. Place a 

 small piece of potassium on the wick of an alcohol-lamp, 

 touch it with a piece of ice, and the lamp will be lighted. 



(22.) Drop a piece of sodium on the surface of water. 

 It will move around, decomposing the water with the dis- 

 engagement of hydrogen. Place a piece in a few drops of 



