brittain] CHEMISTR Y IN NA TURE-STUD V 2 i 



mouth of the bottle. Then quickly cover the mouth of the bottle 

 with a wet piece of glass. 



Heat the prepared charcoal till part of it is glowing in the lamp 

 flame; hold it for a moment in the air, then lower it into the bottle 

 of oxygen, allowing a piece of card-board through which the handle 

 of the wire passes, to close loosely the bottle's mouth. Note whether 

 charcoal becomes hotter or colder when put into the oxygen, and 

 whether it glows more or less brightly than before. 



Remove from the bottle the charcoal remaining in the wire, and 

 before the gas in the bottle has had time to mingle with the air out- 

 side, shake a little clear lime-water through it. The lime-water should 

 become quite milky in appearance. 



Try the charcoal in another bottle of oxygen if necessary, and 

 make sure, either by balancing the residue against the original weight 

 of the charcoal, or by the change in size, whether the charcoal is dis- 

 appearing. 



Rinse the bottle, collect oxygen in it again, and try whether the 

 oxygen will whiten the lime-water. 



After the teacher has performed these experiments before the class, 

 all the children, working in couples, should go through the work and 

 try to obtain results as decided as the teacher did. If delivery tubes 

 are available, the oxygen may be collected in small bottles over water 

 in a bowl or basin. 



The facts having been observed and verified by the class, a 

 thorough discussion of the meaning and explanation of the facts by 

 the pupils should follow, the teacher merely directing the discussion. 

 The argument may follow such a course as this: Since oxygen will 

 not turn lime-water white, a gas different from oxygen must have 

 been formed in the bottle when the charcoal (carbon) was burning 

 there. This new gas was not carbon changed into a gas else when 

 the bottle cooled it would have become solid charcoal again just as 

 water-gas (steam) will solidify into ice or frost as soon as it is cooled 

 down to the temperature at which water remains solid. So this gas 

 which whitens lime-water is neither oxygen nor carbon gas. Nor did 

 it come out of either of them, for they are simple substances. Since 

 this gas is neither carbon nor oxygen, nor a part of either, it must 

 have been formed by the carbon which disappeared uniting chemi- 

 cally with the oxygen around it. So we find that the carbon and 

 oxygen disappeared by uniting together to form a new substance quite 

 different from either. 



This compound gas, composed of carbon and oxygen, is commonly 



