LECTURE AND LABORATORY PRACTICE. 



167 



23.— NOTES ON LECTURE AND LABORATORY APPARATUS. 

 By FROFEiii>OR J. A. SCHOFIELD, Universiti/ of Sydney. 



I. — Apparatus for Showing the Composition of Nitrous and Nitric 



Oxides. 

 This apparatus was devised foi- showing the relation between 



the volume of nitrous or nitric oxide, and the volume of the nitrogen 



left after the removal of the oxygen by heating sodium in the gas 



according to Sir Humphrey Dav}'^s original method. 



Attempts to carry out the decomposition in a bent glass tube, 



accordinp- to the text-book illustrations, alwaj's ended in a violent 



explosion; no explosion has occurred with the apparatus described, 



although it has been used for several years. 



A (Fig. 1) is a glass tube 

 1| in. in diameter and about 

 12 in. long, drawn off at the 

 bottom and connected by I.R. 

 tubing to the levelling tube 

 D. A is closed at the top by an 

 I.R. cork through w^hich pass 

 two narrow glass tubes B 

 and C. The gas is introduced 

 through B and escapes 

 through C; each tube can 

 be closed by a screw clip on 

 a piece of pressure tubing. 

 Through the cork also pass 

 the stem of a deflagrating 

 spoon (E) and a piece of 

 stout copper wire (F) ; these 

 are joined at the bottom, 

 just above the level of the 

 spoon, by a piece of platinum 

 wire soldered to E and F 

 about I in. above the spoon. 

 In the apparatus the plane of 

 these two wires is at right 

 angles to that of the tubes, 

 but for purposes of illustra- 

 tion they are shown in the 

 same plane. On attaching 

 the terminals of a battery to 

 the binding screws at E and 

 F the platinum wire can be 

 made red hot. The sodium 

 is placed in the deflagrating 

 spoon H. In the case of 

 nitrous oxide the platinum 

 wire is wound in the form of 

 a spiral of about four turns, 

 the diameter being about 

 that of the inside of the 



