4 Stansfield, Preparation of Barium. 



The charge (described below) is fired by the following 

 contrivance : through the sides of the crucible, and near 

 the bottom, were drilled two holes opposite to each other ; 

 two aluminium wires were passed through these and 

 joined inside by a bridge of fine platinum wire, which 

 passed through the centre of the starting charge. The 

 aluminium wires were connected by binding screws to two 

 lengths of insulated copper wire, which passed airtight 

 through the stopper of the desiccator. To fire the charge, 

 an electric current of 2-3 amperes was passed through the 

 wires, the platinum wire becoming hot enough to start the 

 reaction. 



In the earlier experiments the charge consisted of 

 barium oxide and aluminium, together with a starting 

 charge of barium peroxide and aluminium. It was after- 

 wards found to be more satisfactory to use nothing but the 

 peroxide and aluminium ; for not only can the peroxide 

 be obtained in a purer condition, but, the heat of the 

 reaction being greater, a better-fused mass is obtained. 

 The aluminium used was in fine granules, except round 

 the platinum wire, where the flake aluminium was used ; 

 it is necessary to strongly heat both sorts before use, in 

 order to drive off the fatty matter with which they are 

 always contaminated. 



In an actual experiment, all the chemicals to be used 

 and the crucible are strongly heated, and allowed to cool 

 in a desiccator, the charge is then weighed out, and the 

 apparatus fitted up as rapidly as possible to prevent 

 absorption of moisture. The bell-jar desiccator containing 

 the apparatus is then exhausted by means of a water 

 pump, and the charge fired. 



After the apparatus has cooled, there remains a grey 

 mass, at the bottom of the crucible, which usually contains 

 crystalline flakes of a silver-white metal. 



