FERTILIZERS 



9 



(C) Metallic copper.— Granulated copper, or fine copper gauze, heated and cooled 

 in a current of hydrogen or by dropping the heated copper into a test tube containing 

 a few cc. of methyl alcohol. 



(d) Sodium hicarhonate. — Free from organic matter. 



(e) Caustic potash solution. — A supersaturated solution of caustic potash in hot 

 water. 



30 APPARATUS. 



(a) Combustion tube. — Hard Bohemian glass, about 65 cm. long, 12.7 mm. internal 

 diameter and sealed at one end. 



(b) Azotometer. — Capacity 100 cc, accurately calibrated. 

 (C) Sprengel mercury air pump. 



(d) Small paper scoop. — Made from stiff writing paper. 



31 DETERMINATION. 



Use 1-2 grams of ordinary commercial fertilizers. In the case of highly nitrogen- 

 ized substances, the amount to be used is governed by the amount of nitrogen esti- 

 mated to be present. Fill the tube (Fig. 1) as follows: (1) about 5 cm. of coarse 



y/. 



^SiE 



n^ 



I \E \m 



sg8ffl®®»3SgS8Bas&a@{^^^sg(ss 



>LJLiiJ 



5 CM. 10 CM. 



CQAR5E SUBSTANCe 



OX IV. ANO firiE onto. 



T CM. 6 cn 

 MSTAUic capiat 



COPPER. OMD. 



2.5 cn 



FRSE e NO- 



SODIUM 

 BICARBONATB. 



THE ROMAN NUMERALS REFER TO THE ORDER IN WHICH THE DIFFERENT 

 PORTIONS ARE TO BE HEATED. 



cupric oxid; (2) place on the small paper scoop a sufficient amount of the fine cupric 

 oxid which, when mixed with the substance to be analyzed, will fill about 10 cm. of 

 the tube; pour on this the substance, rinsing the watch glass with a little of the fine 

 oxid, and mix thoroughly with a spatula, pour into the tube, rinsing the scoop with 

 a little fine oxid; (3) about 30 cm. of coarse cupric oxid; (4) about 7 cm. of metallic 

 copper; (5) about 6 cm. of coarse cupric oxid; (6) a small plug of asbestos; (7) 0.8-1 

 gram of sodium bicarbonate; (8) a large loose plug of asbestos. 



After the tube is filled hold in a horizontal position and tap gently on the table 

 in order that a canal may be formed in the upper portion of the fine cupric oxid. 

 Place the tube in the combustion furnace, leave about 2.5 cm. of it projecting and 

 connect with the pump by a rubber stopper smeared with glycerol, taking care to 

 make the connection perfectly tight. In order to protect the latter from the heat, 

 place an asbestos plate, having a circular opening in the center, over the projecting 

 end of the tube. 



Exhaust the air from the tube by means of the pump. When a vacuum has been 

 obtained, allow the flow of mercury to continue; light the gas under that part of the 



