168 PROCEEDINGS OF SECTION B. 



cup. To cany out the experiment mercury is poured into D until 

 it is at the level of the lower end of the tube B in both A and D. 

 A piece of freshly cut sodium (cube of about | in. edge) is then placed 

 in the deflagrating spoon, and arranged in the case of nitric oxide so 

 that the platinum wire touches it, but in the case of nitrous oxide 

 in the centre of the spiral. The cork is then introduced and the gas 

 passed in through B, both clips being open, until it issues in a pure 

 form from C ; in the case of nitrous oxide this can be tested by a 

 glowing splint, and in the case of nitric oxide by the absence of red 

 fumes in the tube A. The clips on B and C are then closed, and 

 wires from a battery connected to E and F. On increasing the 

 current until the platinum wire is red or white hot, the sodium takes 

 tire and burns. After the tube has cooled, in the case of nitrous 

 oxide, the volume of the gas will be the same as at first, but in the 

 case of nitric oxide it will be half the original volume. 



In the latter case H must be kept above half the distance 

 between the original level of the mercury and the cork. In this case 

 also mercury must be poured into D to keep the level in both tubes 

 tJie same, or else D must be lowered when starting until its open end 

 is about level with the spoon in A, it being then about half full of 

 mercury; as the combustion proceeds, the tube D can be raised to 

 keep the mercuiy at the same level in both tubes. 



The sodium ignites rery readily in the nitric oxide, and once 

 it has started continues to burn until the end of the experiment, but 

 in the case of nitrous oxide ignition does not take place so readily, 

 and it sometimes requires the application of further heat from the 

 spiral to keep the combustion going. 



Instead of an ordinary I.R. cork to close the tube A, it would 

 be better to use an ebonite cork surrounded by a rubber ring, in 

 order that the wires E and F may not shift when introducing the 

 cork into the. tube. 



II. — Apparatus for thp Preparation of Ammonium Hydrate 

 Solution, Concentratbd and Dilute, from Liquid Ammonia. 

 Having experienced some difficulty in obtaining ammonium 



hydrate of sufficient purity in Sydney, the following apparatus, Fig. 



2, was devised for preparing it from liquid ammonia, largely used for 



refrigerating purposes. 



The ammonia cylinder is, of course, placed with the valve at 

 the top. The gas is led through the |- in. glass tube A into the 

 wash-bottle B. At L is a side tube closed at the bottom with a piece 

 of LB. tubing and a screw clip. Ammonia gas can be drawn off from 

 this tube for lecture purposes. It is also advisable to leave the 

 clip open if the apparatus is unused for a considerable period. 



The water in the wash-bottle B soon becomes saturated with 

 the gas, and hence there is little tendency for the water to be drawn 

 into the tube A. 



From B' the gas passes into the bottle in which the saturated 

 solution of NH4OH is made. At the beginning this bottle should 

 not be more than one-half full, since the solution increases consider- 

 ably in bulk as the NH3 is absorbed. Fresh water is introduced into 



