i8 PLANT PRODUCTS 



advantage that there is nothing in it of an objectionable 

 character. 



Ammonium Carbonate. — Ammonium carbonate itself 

 is too volatile, but ammonitmi hydrogen carbonate is a 

 light, dry powdery substance, which only slightly smells 

 of ammonia. At present no serious attempt has been made 

 to produce ammonium bi-carbonate for use as a fertilizer, 

 but since the gas works have already prepared directly a 

 strong liquid ammonia there does not seem any reason why 

 they should not manufacture ammonium hydrogen carbonate, 

 as, of course, it is obvious that they produce carbonic acid 

 in quantities many thousands of times more than is needed 

 for this purpose. At present, however, this also is not a 

 practicable fertilizer. 



Nitrate of Soda. — Nitrate of soda chiefly occurs as 

 a deposit in Chili, is mined, extracted with water, and re- 

 crystallized. The composition is fairly constant, containing 

 rarely less than 93 per cent, pure nitrate of soda, or more than 

 97 per cent. pure. Of a large number of samples examined, 

 over one half had between 96 and 97 per cent, pure nitrate 

 of soda. As it is obtained exclusively from foreign sources 

 it is imported by ship, and as a rule the shipments are of 

 a definite known composition. Nitrate of soda does not 

 lend itself very particularly well to mixtures. It can be 

 mixed with basic slag, but such a mixture is not particularly 

 useful, because nitrate of soda is very quick acting, and basic 

 slag is very slow. It cannot be mixed at all satisfactorily 

 with super-phosphates, since this mixture becomes somewhat 

 heated and produces free nitric acid, which then distils 

 out of the mass and condenses on the outer surface and thus 

 rots the bags or sacks which may have been used for transport. 

 The chief method of application of nitrate of soda to the soil 

 is for a top dressing, as it need not undergo any chemical 

 change in the soil before absorption by the plant. It is 

 applied as a top dressing in the same way as sulphate of 

 ammonia, and is among the quickest of all fertilizers. 

 Nitrate of soda as sent to the farmer is not infrequently in 

 large lumps, and requires to be broken up. Owing to its 



