832 



Notes on Manures for December. [Dec, 



strengthened and the quality of the grain improved. Leys 

 will generally do better with slag than with other phosphates. 



Lime and its various Forms. — Much confusion exists as to 

 the forms in which lime is offered to the farmer. Among the 

 various terms used are: lime, quicklime, ground lime, burnt 

 lime, agricultural lime, limestone, pulverised or ground lime- 

 stone, chalk, hydrate of lime, hydrated lime, etc. All of these 

 serve as sources of lime, and under proper conditions all of 

 them could equally be used for treatment of sour soil, whether 

 of grass or of arable land. They differ very much, however, 

 in the amount of true lime they contain; one product may be 

 practically all pure lime, and another, even when free from 

 any admixture or impurity, natural or artificial, contains at 

 the best only 56 per cent, of pure lime. It is imperative that 

 the farmer should know exactly what he is buying. All the 

 various substances fall into 3 groups : — 

 Pure lime or calcium oxide, 

 Carbonate of lime, or calcium carbonate, 

 Hydrate of lime, or calcium hydroxide. 



All consignments purchased at more than a few shillings 

 per ton should be analysed and the results stated in terms of 

 calcium oxide (CaO) which is a perfectly clear and un- 

 ambiguous term, denoting pure lime. The following show6 

 the relationships between them : — 



1 cwt. (112 lb.) of calcium oxide (CaO) has same agricultural 



value as 1 cwt. 36 lb. of calcium hydroxide (Ca(OH)^) or 



1 cw r t. 88 lb. of calcium carbonate (CaC0 3 ); 

 or, put in reverse order and in another way : — 



100 lb. of calcium carbonate has the same agricultural value 



as 74 lb. of calcium hydroxide or 56 lb. of calcium oxide. 



On this basis it should not prove difficult to compare 

 quotations. The materials in common use are as follows: — 



Calcium oxide (CaO) : Burnt lime, ground lime, lump lime, 

 cob lime. The composition varies according to the rock from 

 which these are produced, but a good sample may contain about 

 85 per cent, calcium oxide (CaO), though higher figures are 

 also obtained. 



Calcium hydroxide or calcium hydrate (Ca(OH) 2 ) : Hydrated 

 lime, hydrate of lime. Composition depends on quality and 

 nature of the rock. We have seen a sample made from the 

 Somerset limestone which contained 96.6 per cent, of calcium 

 hydrate, which as shown above has the same value as 73 per 

 cent, of calcium oxide (CaO). 



