114] Nitrogen in Nitrates 8 1 



communication is made between the calibrated tube and the 

 air. Raise the tube b until the mercury entirely fills a. Close 

 the tap. Return b to its position, clamping the tubes in a retort 

 stand as shown in fig. 33. Weigh out about '3 gram of sodium 

 nitrate, and introduce the powder into the funnel. Add about 

 1 c.c. of water. As soon as the nitrate is dissolved, draw it 

 into the measuring tube. Wash the cup with another c.c. of 

 water, and draw that into the measuring tube. Finally, add 

 15 c.c. of pure strong sulphuric acid, and draw that in. 



Now unclamp the tube containing the acid mixture, and 

 incline it once or twice so as to place the mercury in contact 

 with the liquid ; gas will commence to come off and collect at 

 the top. When this ceases shake more violently, so that the mer- 

 cury at the surface of contact gets broken up into a number of 

 globules, thus coming into thorough contact with the nitric acid. 

 By this means the whole of the nitrogen will be transformed 

 into nitric oxide, and if the tubes be clamped so that the mer- 

 cury stands at the same level in both tubes,' the volume may 

 be read off. It may be assumed, for measuring purposes, that 

 mercury has 6*5 times the specific gravity of sulphuric acid. 

 This must be allowed for in adjusting the heights of the 

 columns in the two tubes. Allow the whole apparatus to cool 

 down for half-an-hour. Readjust the height of the mercury 

 column. Note volume of gas, temperature of air, and height 

 of barometer in millimetres. 



The calculation is exactly the same as that used for Schloe- 

 sing's apparatus (see paragraph 108). 



