Map Showing Distribution of Plants in New York State Producing Ground Limestone. COMPARATIVE VALUE OF GROUND LIMESTONES. Limestones are made up of calcium carbonate or calcium and magnesium carbonates and a varying amount of clay-like material. The better grades run about 90 per ct. total carbonates. All limestones contain a higher percentage of calcium carbonate (CaCO3) than magnesium carbonate (MgCO3), the latter varying in different stones from nothing to a maximum of about 45 per ct. Those containing ten per ct. or more magnesium carbonate are usually referred to as magnesium limestone and if they carry near the maximum amount they are also called dolomites. So far as any study has been made of the subject, magnesium limestones have been found to be fully as effective as straight calcium stones for practical use in soil improvement. In fact, a given weight of magnesium carbonate is capable of neutralizing somewhat more acidity than the same weight of calcium carbonate, 100 pounds of the former being equal to 119 pounds of the latter in this respect. Also, it is to be remembered that magnesium as well as calcium is one of the ten essential elements of plant food and that a part of the benefit from an application of limestone often may be due to the more liberal supply of these two elements of fertility. The comparative value of different limestones for use on the soil is conveniently expressed in terms of their calcium carbonate equivalents. This figure is obtained by adding to the percentage of calcium carbonate the percentage of magnesium carbonate multiplied by 1.19, since one pound of magnesium carbonate is chemically equivalent to 1.19 pounds of calcium carbonate. Thus, a stone containing 76 per ct. calcium carbonate and 20 per ct. magnesium carbonate (equal to 23.8 per ct. calcium carbonate) would have a calcium carbonate equivalent of 99.8. This figure will usually be but little. different from that for the percentage of total carbonate. The buyer of ground limestone is often confused by long and varied statements of analyses and by claims to special merit made for particular products. He should note the figure for calcium carbonate equivalent and bear in mind that, assuming reasonable fineness, this gives the comparative value of the product. If a stone showing a calcium carbonate equivalent of 90 can be delivered to the buyer's railway station for $1.80 per ton, then one having an equivalent of 100 is worth scarcely more than $2.00 per ton; the two are valuable in the proportion of 90 to 100, allowing only |