3 

 per ton f.o.b. plant; the freight to point of destination is $2.75; and the product 

 contains about 1,100 pounds of effective oxides per ton, as shown by analysis. 

 $4.25 + $2.75 = $7.00 - 11.00 = 63.6 cents, which is the cost of 100 pounds 

 of effective oxides. 



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 

 (CO2). Calcium or magnesium not in the form of carbonate is present either 

 as hydrated lime (water- or air-slaked) or as burned lime (caustic or unslaked). 

 It should be understood 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. 



"Calcium oxide equivalent" represents the acid neutralizing value of both 

 the magnesium and calcium, expressed in terms of calcium oxide. The figures 

 in the "per cent" column are obtained by multiplying the magnesium oxide 

 by the factor 1.39 and adding the calcium oxide; or they may be obtained by 

 a direct titration with standard acid. All samples are checked by both methods 

 in this laboratory. The "pounds in one ton" are secured by multiplying the 

 figures in the "per cent" column by 20. The "cost of 100 pounds" is based 

 on prices furnished by the producers. 



Table II, "Calcium oxide equivalent: per cent and pounds in one ton." In 

 securing these data the degree of fineness to which the limestone has been 

 ground is taken into consideration. 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. The magnesium 

 oxide found is multiplied by the factor 1.39 and added to the calcium oxide in 

 estimating the calcium oxide equivalent. 



In the column headed "Carbonates of calcium and magnesium" the calcula- 

 tion allows for the small amounts ot calcium and magnesium combined as basic 

 silicates; these are readily soluble in mineral acid solutions but obviously 

 should not be classed as carbonates. 



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. 



