260 Domestic Science 



means of the fine iron wire used for tying up flowers. 

 Wire the other end of the spring to a cork, which fits 

 the neck of a bell- jar. Fill the bell- jar with oxygen, 

 and stand it over water in a shallow plate. (The filling 

 may be done well enough for all practical purposes if 

 a rubber tube, attached to the end of the delivery tube 

 of an apparatus in which oxygen is being generated, 

 is allowed to dip to the bottom of the jar, while the 

 latter is standing in position on the plate, and the gas 

 passed in for about three minutes in a steady stream.) 

 When the apparatus has been prepared as above, light 

 the taper, and while it is still well alight, plunge taper 

 and spring into the bell- jar. The great heat produced 

 by the burning of the taper in oxygen will be sufficient 

 to start the combustion of the iron. Vivid glowing of 

 the molten ball of metal formed at the end of the spring, 

 accompanied by showers of bright sparks, will be ob- 

 served as the iron burns away. The sparks consist of 

 a black oxide of iron, and they may be found at the 

 bottom of the water after the completion of the burning. 

 Pour the water from the plate into a jar and see that 

 as much of the iron oxide as possible is transferred to 

 the same jar. Shake the jar and its contents well and 

 test whether the liquid left in the jar has any effect 

 on either red or blue litmus. (Should any positive 

 result of these tests be obtained, repeat the experiment 

 with water previously tested with regard to its action 

 on litmus and found to be neutral, i.e. neither acid nor 

 alkaline.) 



178. We have now learnt enough of the qualities 

 of oxides to be able to classify them into certain groups. 

 Thus we have acidic oxides those which form acids 

 when combined with the elements of water. Con- 

 trasted with these are the basic oxides of which we have 



