4 CONTROL SERIES No. 46 



shortage of the combined oxides was only .80 per cent. The Pownal Limestone 

 showed a deficiency of 1.74 per cent of calcium oxide, which was more than 

 balanced by an overrun of 2.77 per cent of magnesium oxide. In general it may 

 be said that some liming materials are known to fluctuate in composition, some- 

 times running low in one element and high in the other. This is not a serious 

 matter provided the sum of the calcium and magnesium oxides found is equal to 

 the combined oxides guaranteed. 



With reference to degree of fineness with which limestones are ground, it may be 

 said that, in order to compare favorably with the hydrated or slaked products 

 when used in amounts to supply a like quantity of calcium and magnesium oxides 

 per acre, they should be ground so that about 80 per cent will pass a 100-mesh 

 sieve. Two of the products listed, the Producto Limestone and Oyster Shell 

 Lime, are subjects for criticism as to their mechanical condition. 



Purchase of Lime Products. 



In the purchase of lime the principal factors which determine the most econom- 

 ical selection are: the effective oxides in one ton (see analj'sis tables for these 

 data); cost of lime at plant, and freight charges from plant to destination (data 

 furnished by the producer) ; and hauling cost from depot to farm. The sum of the 

 different costs enumerated, divided by the effective oxides per ton, will show 

 the most economical lime to pm"chase. Quotations should always be secured 

 from plants in position to furnish favorable freight charges, as not infrequently 

 the froiglit rate is an important factor in making a selection. 



Explanation of Tables of Analyses. 



Table I, "Proportion of total oxides as carbonates." The data furnished in this 

 column are calculated from an actual determination of carbon dioxide (C02). 

 Calcium or magnesium not in the form of carbonate is present either as hydrated 

 (water- or air-slaked) or as burned lime (caustic or unslaked). It should be under- 

 stood that all of the products listed in this table have at .some time been burned, 

 and the proportion of oxides present as carbonates indicates to what extent the 

 product has absorbed carbonic acid from the air. 



"Pounds of effective oxides in one ton" represents the sum of the calcium and 

 magnesium oxides in one ton of the lime product, assuming that both ingredients 

 from this source will become readily available. 



The calculations found in column "Cost of 100 pounds of effective oxides" 

 are based on prices furnished by the producers. 



Table II, "Pounds of effective oxides in one ton." In securing these data the 

 degree of fineness to which the hmestone has been ground is taken into considera- 

 tion. On those products which are finely ground so that all of the material will 

 pass through a 20-mesh sieve, it is assumed that all of the calcium and magnesium 

 oxides will become available in the soil within a five-year period. On those 

 products which will not wholly pass a 20-mesh sieve, it is assumed that the oxides 

 in that portion which is coarser than 20-mesh will be only 50 per cent effective 

 during the same period. 



Under "Mechanical analysis" the figures represent in round numbers the 

 percentage of product that would pass the various meshed sieves mentioned. 



In both tables the figures in parenthesis following the brand name show the 

 number of samples collected and analyzed. 



