151-158] TESTS FOR THE METALS 55 



Metal vessels are best cleaned with a little moistened sea- 

 sand. 



151. When using a reagent bottle the bottle should be 

 grasped by the right hand, and the stopper taken out by the 

 left hand. After use replace the stopper and put back the 

 bottle on the shelf. In this way the bottle is not placed on 

 the bench at all, and much time is saved. 



152. Brass crucible tongs must not be used for holding 

 vessels containing acid liquids, or the brass may be dissolved 

 and introduced into the liquid. Platinum crucibles must 

 not be handled by brass tongs when red-hot. 



153. When heating liquids in porcelain or glass the 

 flame should never reach higher than the level of the liquid, 

 or the vessel will break. 



154. Liquids only are to be poured down the sink ; 

 solids and filter-papers should be placed in boxes or baskets. 



155. Crucibles or vessels containing solids are best 

 heated on pipeclay supports, flasks containing liquids on 

 wire gauze. 



156. When an operation is unfinished the vessels con- 

 taining the substances should be labelled before putting 

 them away. Never trust to memory in these matters. 



157. Before commencing any operation read carefully 

 through the whole of the description. 



REACTIONS FOR THE METALS 



ALUMINIUM (Al).— Use alum, AlK(S0 4 ) 2 .i2H 2 0, or 

 ammonia-alum, AlNH 4 (S0 4 ) 2 .i2H 2 0, solution. 



158. Ammonium Hydrate (NH 4 OH) gives a white 

 gelatinous precipitate of aluminium hydrate, Al(OH) 3 . 

 This precipitate is somewhat soluble in a larger excess of 



