118 Walker—Some Uses of the Alternating Current. 
usual method of laboratory preparation from illuminating gas 
burning at the base of a Bunsen burner. This method is more 
expensive as it requires both hydrogen and an electric current. 
But the acetylene may be removed by ammoniacal silver oxide 
solution and the hydrogen collected in a gas holder and used 
again. 
Racine , Wis. 
