598 AGRICULTURAL ANALYSIS 



quick action in neutralizing a free acid or aiding in decomposi- 

 tion is the object in view. In a soil rich in ammonia compounds 

 the powdered lime carbonate is preferable in order to avoid loss 

 of the nitrogen compounds. Burned lime also exists in a finer 

 state of subdivision than is usually found in the ground rock 

 or shells. If the final effect desired is the amelioration of the phys- 

 ical state of the soil and the promotion of nitrification there is 

 little difference in value between the burned and unburned lime. 



503. Analysis of Lime. Lime, which is prepared for use as 

 a fertilizer is rarely submitted to a chemical examination. It 

 it is easy to see, however, that such an examination is of some im- 

 portance. If the real value of a sample be dependent on the con- 

 tent of lime, the actual quantity present as determined by analy- 

 sis, must fix the value for agricultural purposes. The more im- 

 portant things to be determined are the quantities of lime, and of 

 slaked lime, of undecomposed calcium carbonate, and of insoluble 

 matter. It will be also of interest to determine the respective 

 quantities of lime present as oxid, hydrate, and carbonate. If any 

 question be raised in the case of slaked lime in respect of its 

 origin, it can usually be answered by an examination of the un- 

 burned or unslaked residues. In perfectly slaked lime containing 

 no debris, the analyst will be unable to discover whether it has 

 been made from limestone, marble or shells. The lime used for 

 agricultural purposes should be reasonably free of magnesia, and 

 should not be air-slaked before transportation to the field. In 

 <lry air-slaking, a considerable quantity of carbonate may be 

 formed. 



504. The Analytical Process, (i) Insoluble and Soluble Con- 

 stituents. A representative sample of the lime having been se- 

 cured, it is reduced to a powder and passed through a half milli- 

 meter mesh sieve or ground to a fine powder in an agate mortar. 

 Two grams of this sample are digested with an excess of hydro- 

 chloric acid, for two hours with frequent stirring, filtered, the 

 residue washed with hot distilled water until chlorin is all re- 

 moved, and dried to constant weight. The lime, magnesia, silica, 



