EXPERIMENT STATION BULLETINS. 317 



"quick lime" and "caustic lime." It is produced from the raw lime rock 

 by bumino;. One h.undred pounds of limestone will produce 56 pounds 

 of burned lime. This is the most active form of lime and may be used 

 at the rate of 1,000 to 1.200 pounds per acre. INluch larger quantities 

 are sometimes used but the above amounts should be sufficient in most 

 cases. 



This form of lime is usually put upon the markets in lumps and be- 

 fore being- applied to the soil must be reduced to powder form. This is 

 conveniently done by placing the lime in small piles about the field 

 and covering it with three or four inches of moist soil. The lime will 

 absorb the moisture from the soil and gradually break down into a fine 

 powder, when it may be spread with a shovel. 



Ground burned lime may be purchased at a slightly advanced price. 



Eydratcd Lime.- — When burned lime is treated with water or steam it 

 enters into combination with the water and forms what is chemically 

 termed calcium hydrate or hydrated lime. This form, like burned lime, 

 is caustic but it is always in the powder form and may be readily ap- 

 plied to the soil. Fifty-six pounds of burned lime are equivalent to 

 74 pounds of hydrated lime. This form of lime is also known as slaked 

 (slacked) lime. 



Air flaked Lime. — When burned lime is exposed to the action of the 

 air for any considerable length of time it gradually takes up moisture and 

 carbon dioxide and changes to the hydrate and carbonate forms. If ex- 

 posed for a sufficiently long time it will all change to the carbonate form 

 or the state in which it was before burning. Its value lies somewhere 

 between that of hydrated lime and ground lime-stone. 



Refuse Lime from Sugar Factories. — Burned lime is used in the pro- 

 cess of recovering sugar from the sugar beet and this waste lime is 

 partly hydrated and partly carbonated and is consequently very similar 

 to air slaked lime and should be used in about the same amounts. This 

 lime also contains small amounts of nitrogen, phosphoric acid and 

 potash absorbed from the beet juices. 



3Iorl is found quite extensively throughout the state and many of the 

 deposits are very pure calcium carbonate. When the cost of laying 

 down marl on the farm in a dry powder form does not exceed |1.50 per 

 ton it may profitably be used as a substitute for commercial lime. 



Leached Eardioood Ashes, contain from 65 to 70 per cent calcium car- 

 bonate and under favorable conditions may be used as a substitute for 

 commercial lime. Unleached ashes are more valuable for the potash 

 they contain and should not be used as a source of lime except in cases 

 where this element is also needed. 



Burned lime, hydrated lime and air slaked lime are caustic, diminish- 

 ing in degree, however, in the order named. The fine powder is irritating 

 to the skin and nostrils and its application to the soil is usually attend- 

 ed with more or less discomfort by the persons doing the work. Ground 

 limestone is not caustic and consequently is not irritating to the skin. 



When the lime is to be used on heavy clay soils to correct the physical 

 condition, the burned lime or hydrated lime are recommended as these 

 forms act more rapidly than the ground limiestone. For use on light 

 sandy soils the ground limestone or marl is recommended. 



