PASSAGE OF OXYGEN THROUGH THE BODY 115 



Ignite the sulphur in the flame of an alcohol lamp or Bunsen burner, 

 and lower it into a bottle of oxygen. Observe the change in the rate 

 of burning, the color of the flame, and the material formed in the bottle 

 by the burning. The gas remaining in the bottle is sulphur dioxide 

 (SO 2 ), formed by the uniting of the sulphur and the oxygen. 



4. Bend a small loop on* the end of a piece of picture wire. Heat the 

 loop in a flame and insert it in some powdered sulphur. Ignite the 

 melted sulphur which adheres, and insert it quickly in a bottle of oxygen. 

 Observe the dark, brittle material which is formed by the burning of the 

 iron. It is a compound of the iron with oxygen, similar to iron rust, and 

 formed by their uniting. 



Preparation and Properties of Carbon Dioxide. I. (a) Attach a 

 piece of carbon (charcoal) no larger than the end of the thumb to a piece 

 of wire. Ignite the charcoal in a hot flame and lower it into a vessel of 

 oxygen. Observe its combustion, letting it remain in the bottle until it 

 ceases to burn. Note that the burning has consumed a part of the car- 

 bon and has used up the free oxygen. Has anything been formed in 

 their stead? 



(b) Remove the charcoal and add a little limewater. Cover the 

 bottle with a piece of cardboard, and bring the gas and the limewater 

 in contact by shaking. Note any change in the color of the limewater. 

 If it turns white, the presence of carbon dioxide is proved. 



2.. Burn a splinter in a large vessel of air, keeping the top covered. 

 Add limewater and shake. Note and account for the result. 



3. Place several pieces of marble (limestone) in a jar holding at least 

 half a gallon. Barely cover the marble with water, and then add hydro- 

 chloric acid until a gas is rapidly evolved. This gas is carbon dioxide. 



() Does it possess color? 



(V) Insert a burning splinter to see if it supports combustion. 



(c) Place a bottle of oxygen by the side of the vessel of carbon di- 

 oxide. Light a splinter and extinguish the flame by lowering it into 

 the vessel of carbon dioxide. Withdraw immediately, and if a spark 

 remains on the splinter, thrust it into the bottle of oxygen. Then in- 

 sert the relighted splinter into the carbon dioxide. Repeat several 

 times, kindling the flame in one gas and extinguishing it in the other. 

 Finally show that the spark also may be extinguished by holding the 

 splinter a little longer in the carbon dioxide. 



(</) Tip the jar containing the carbon dioxide over the mouth of a 

 tumbler, as in pouring water, though not far enough to spill the acid, and 



