NITROGENOUS MANURES. 



221 



3. Vessels heated by a closed tubular bundle (? steam coil). 

 which have been introduced by the British and German companies. 

 These vessels measure 11 metres (86 feet), 1-85 metre (6 ft.) wide by 

 1-85 metre (6 ft.) high, into which the mother hquor and the wash 

 water are run and heated to boihng, then six trucks of perforated 

 wrought-iron containing about 1 tons of caliche. The nitrate dissolves 

 in the water whilst the residue remains in the trucks. To hasten 

 solution the liquid is agitated by injection of steam and of hot air 

 under each truck by means of a Eoerting's injector. This plant 

 works more economically than the preceding. At the same time 

 the solutions so obtained are more pure and more concentrated. 

 To get a ton of nitrate requires 3 tons of caliche. The crystallized 

 nitrate is left to drain, then it is dried in the open air. Nevertheless 

 it always remains slightly moist owing to the presence of chlorides 

 of calcium, of magnesium, and possibly also of nitrates of calcium 

 and magnesium. It crystallizes in rhombohedra, and has a dirty 

 reddish-grey appearance, due to its oxide of iron content and to 

 bituminous substances. The residue left by the solution {rijyio) still 

 contains from 15 to 35 per cent of NaNOg. It is boiled with water 

 and a weak solution of 43 to 45° B. obtained, which is utilized to 

 dissolve a fresh charge of crude salt. The muds from the clarifica- 

 tion are treated in the same way. According to Dr. Langbein, 

 they contain 67'1 of common salt and 27-3 of nitrate of soda. 



Chilian nitrate of soda, such as dispatched from the spot of pro^ 

 duction, has the following composition : — 



TABLE LXV.— ANALYSIS OF CHILIAN NITKATE OF SODA. 



Nitrate of soda 

 Common salt 

 Potassimn chloride 

 Sodium sulphate 

 Sodium iodide 

 Magnesium chloride 

 Water 

 Boric acid . 



Per cent. 

 94-0 

 l-o'2 

 0-64 

 0-92 

 0-29 

 0-93 

 1-36 



traces 



Per cent. 

 15-31 N. 



99-60 



Better equipped factories supply nitrate of the following average 

 composition : — 



TABLE LXVL— ANALYSIS OF BETTEK QUALITY NITRATE OF SODA.. 



Nitrate of soda . 



Common salt 



Soluble sulphate of soda 



Insoluble 



Water 



Per cent. 

 96-00 

 1-00 

 O-oO 

 0-25 

 2-25 



100-00 



