INTRODUCTION 15 



flame, turning it round and seeing that it is gradually 

 heated. When the tube shows signs of softening, slowly 

 bend it as desired. Larger sizes of tubing cannot be 

 bent in the flame of a spirit lamp. 



Care of Apparatus and Chemicals. Special precau- 

 tions have to be taken by teachers who undertake work 

 of this nature. Some of the reagents are highly corro- 

 sive, e.g. nitric acid, sulphuric acid; phosphorus takes 

 fire when exposed to the air; sodium is highly dangerous 

 if put into water in too large quantities; and hydrogen 

 and oxygen make an explosive mixture. Further, many 

 chemicals are poisonous, and the greatest care has to be 

 exercised in storing them. Children should never be 

 allowed to handle them by themselves, and they are 

 best kept under lock and key. Glassware should be 

 gently handled to avoid breakage. 



Cost. If full use be made of such substitutes as can 

 be obtained, the cost of this work will amount to very 

 little. Five shillings, it is estimated, will enable the 

 teacher to buy sufficient apparatus to keep the work 

 going, while for ten shillings he can be thoroughly 

 equipped. If there were a regular demand for appa- 

 ratus some local firm of importers would doubtless be 

 willing to make arrangements to keep a stock of just 

 what teachers might require. 



