4l6 AGRICULTURAL ANALYSIS 



through the side tube, carrying the rubber tube and clamp. The 

 three-way cock is closed, and the solution containing the nitrate 

 placed in the cup. By lowering the tube b and opening the cock 

 the liquid is carefully passed into a, being careful to close the 

 cock before all the liquid has passed out of the cup. By repeated 

 rinsings with pure concentrated sulfuric acid, every particle of the 

 nitric compound is finally introduced into a, together with a large 

 excess of sulfuric acid. The total volume of the introduced liquid 

 should not exceed 10 cubic centimeters. The mixture of the mer- 

 cury, nitric compound, and sulfuric acid is effected by detaching 

 a from its support, compressing the rubber connection between a 

 and b, placing a nearly in a horizontal position, and quickly bring- 

 ing it into a vertical position with vigorous shaking. 



After about five minutes the reaction is complete, and the level 

 of the liquids in the two tubes is so adjusted as to compensate 

 for the difference in specific gravity between the acid mixture in 

 a and the mercury in b ; in other words, the mercury column in b 

 should stand above the mercury column in a one-seventh of the 

 length of the acid mixture in a. This secures atmospheric pres- 

 sure on the nitric oxid which has been collected in a. The meas- 

 ured volume of nitric oxid should be reduced to o and 760 milli- 

 meters barometric pressure. Each cubic centimeter of nitric oxid 

 thus obtained corresponds to 1.343 milligrams NO; 2.417 milli- 

 grams N 2 O 5 ; 1.701 milligrams N 2 O 3 ; 2.820 milligrams HNO S ; 

 4.521 milligrams KNO 3 , and 3.805 milligrams NaNO 3 . 



362. Lunge's Improved Apparatus. Lunge has improved his 

 apparatus for generating and measuring gases and extended its 

 applicability. 60 The part of it designed to measure the volume of 

 a gas is the same in all cases. For generating the gas, the ap- 

 paratus varies according to the character of the substance under 

 examination. 



The measuring apparatus is shown in Fig. 29. It is composed 

 essentially of three tubes, conveniently mounted on a wooden 

 holder with a box base for saving any spilled mercury. The 

 support is not shown in the illustration. 



The tubes A, B, C, are mutually connected by means of a 

 80 Bulletin de la Socit chimique de Paris, 1894, [3], 1 1 : 625. 



