33 



tube. After once beginning to make the oxygen, the lamp flame must 

 not be taken away from the test tube while the delivery tube is under 

 water. The cooling of the tube will contract the gas, and water will 

 rush back and break the hot tube. 



All the apparatus may be held with the hands. One pupil may attend 

 to the bottles; one hold the test tube, using a thick handle of paper as a 

 holder; another may manage the lamp. A stand and other conveniences 

 may be used. For descriptions and figures see any elementary text book 

 in chemistry. 



Note. — Every single operation of the above should be questioned 

 about, and explained by the pupil, as every step is a good lesson. 



Now that we have five or more bottles of oxygen, they may be tested 

 as follows: 



In one bottle, have one of the children insert a lighted splinter. Let 

 the fire be extinguished except a small glow at the end. Also have a 

 small piece of lighted candle attached to a wire, thrust down into the 

 jar. 



A piece of sulphur may be burned in the next jar. A little cup made 

 from a piece of crayon, fastened to a wire can be used to hold the lighted 

 piece of sulphur while inserting it into the jar. 



A fine iron or steel wire may be burned. The wire may be bent into 

 a spiral form by wrapping it about a round lead pencil. To one end of 

 the wire attach a very small splinter, or bit of sulphur to serve as a 

 lighter. The wood or sulphur is lighted, and the wire thrust into the 

 jar of oxygen. 



To burn charcoal, a charred splinter, or a glowing coal fastened to a 

 wire may be used. 



A brilliant effect is produced by beating a teaspoonful of finely pow- 

 dered charcoal to a glow, and then letting it fall into a jar of oxj'^gen. 



The burning of phosphorous gives the brightest light. Phosphorous 

 must be handled with care. It is best to use a pair of forceps, and cut 

 the piece to be used under water. Dry the water off with blotting paper. 

 It lights easily by friction, and a small piece of burning phosphorous on 

 the hand makes a painful and bad wound. It is poisonous. Handled 

 carefully there is no danger. All small pieces must be picked up and 

 put back into a bottle of water where it is best kept. The phosphorus is 

 burned in the crayon cup as was the sulphur. 



Now questions will arise as to what are the results ot the burning in 

 each case. The white smoke in the last is a combination of oxygen and 

 phosphorus, so in each of the other cases an oxide is formed e. g. of 

 carbon, of iron, and of sulphur. Each of the above should be repeated 

 until it is clearly seen just what has taken place. 



These experiments are so interesting to children, that they will not 

 mind having them repeated many times. This is good in giving them 

 clearer notions, better command of handling apparatus, and a familiar- 

 ity with the facts. 



