EXPERIMENTS 323 



1) Oxygen manufacture: 



Put a /2 teaspoonf ul each of chlorate of potash and manganese 

 dioxide into test tube. Mix and close tightly with stopper 

 (Carrying bent glass tube. Have ready pneumatic trough filled 

 vvith water, in which several wide-mouthed bottles also filled 

 with water are standing inverted over holes of perforated shelf. 

 Place lighted lamp near trough. Gently heat lower end of test 

 tube containing mixed chemicals over flame until gas begins to 

 be given off. Insert open end of delivery tube under shelf of 

 trough so that bubbles of gas will pass up into bottles and dis- 

 place water in them. In this way, fill several bottles. 



Caution : The heating must be continued uniformly, and when 

 the gas begins to come very slowly the tube must be withdrawn 

 from the trough quickly enough to prevent the cold water from 

 being sucked back into the test tube. The test tube should then 

 be laid carefully upon something which it will not burn until it 

 is cold enough to be washed out. 



2) Combustion in oxygen: 



a) Thrust end of a burning splinter of pine wood into one 

 of bottles of oxygen covered with a piece of tin. Remove 

 quickly, blow out flame and reintroduce wood with a live coal 

 on its tip. Continue until wood will no longer burn. Test 

 contents of bottle with lime water as in Exp. 3, a), part 1, and 

 compare results with those previously obtained. 



b) Heat end of iron wire and melt on it a drop of sulphur. 

 Light sulphur and thrust it into a bottle of oxygen. Note 

 rust (iron oxide) on sides of bottle. 



c) Continue experiment by demonstrating combustion of 

 small bits of magnesium, copper, zinc, etc. 



3 ) Nit rogen separatio n : 1 



Make a wood float 1 in. by 1 in. by V 2 in. thick. Upon this, 

 place a sq. in. of sheet tin, on centre of which rest a piece of 

 phosphorus the size of a pea. ( The phosphorus should be cut 

 under water and not handled.) Float phosphorus boat on 

 surface of water in pneumatic trough. Light phosphorus and 

 immediately place over it upon tin shelf of trough an inverted 



1 This is really a method of oxygen elimination by phosphorus 

 absorption. The oxygen combines with the phosphorus and the 

 resulting oxide is absorbed by the water. The nitrogen is conse- 

 quently left pure. 



