Technical Terms. The practical man uses a great number of technical terms in his own field of labor, and often fails to recognize the fact that they are technical, and may be puzzling to many other people. He uses such terms for the sake of accuracy, desiring to express to his fellow-workmen exactly what he means. The farmer, stockman, carpenter, banker—all have command of such terms, and need them, but the chemist who, in a way, must come even nearer to accuracy in expression, finds that many people who want his assistance do not care to master and use any of his terms. Failure to do so compels misunderstanding. Anyone who is interested in the right use of lime should be willing to add a few of the chemists' technical terms to the scores in his own line of work that he uses constantly, and thus let the whole matter of liming land come to appear more simple to him. Acquaintance with a few terms is necessary to any understanding of statements of analyses upon which purchase should be made.

An Element is a substance that cannot be divided into simpler substances. The number of elements necessary to the growth of plants is small, and of this number calcium is one and magnesium is another.

Compounds. We do not find these elements merely mixed with other elements to form a soil. They unite in definite proportions by weight to form chemical compounds. As conditions change, many of these compounds undergo change, giving up one element, or group of elements, and uniting with another element or group from a different compound. Heat, moisture and the action of bacteria are factors in promoting the changes. There is no more restless activity than may be found among the elements composing a productive soil.

Calcium is an element which will unite with oxygen and carbon dioxide to form a compound known as calcium carbonate. The chemist's symbol for calcium is Ca.

Calcium Oxide is a compound left after the burning of limestone, and is known as fresh burned lime, or quick lime. Its formula is CaO. It contains, when pure, 40 parts of calcium and 16 parts oxygen by weight.

Carbon Dioxide is a compound whose formula is CO₂.

Calcium Carbonate, known also as carbonate of lime, has a definite composition, containing, when pure, 56 parts CaO and 44 parts CO₂. It is known to the chemist as CaCO₃, and forms practically all of very pure limestones. Impure limestones contain some earthy materials that became mixed with the lime carbonate when the rock was being formed.

Calcium Hydroxide is a compound made by permitting calcium oxide to combine with water, and is known as lime hydrate. It contains 56 parts by weight CaO and 18 parts water, and has the formula Ca(OH)2.

Magnesium is an element, and is found in magnesium carbonate, a compound that is effective in correcting soil acidity.

Magnesian Limestone. Magnesium carbonate is usually found in combination with calcium carbonate, and when about 47 per cent of the total carbonates is magnesium carbonate, the limestone is known as dolomite.

Ground Limestone is the stone pulverized so that it can be distributed. It is carbonate of lime (CaCO₃), or a combination of calcium and magnesium carbonate, and in a way has a right to be designated as "lime," but such use leads to confusion.

Fresh Burned Lime. Calcium oxide (CaO) formerly was accurately designated as "lime," but the words "fresh burned" are often prefixed to prevent confusion with lime carbonate or the hydrate. It is known as "lump lime," "caustic lime" and "stone lime."

Ground or Pulverized Lime. Fresh burned lime may be ground fine, so that it can be spread on land without slaking. This product should not be confused with ground limestone or hydrated lime. Fresh ground lime is worth nearly twice as much per ton as ground limestone, but some of the product on the market is far from pure. There is opportunity to grind up unburned and waste material with the caustic lime, and this form of lime usually contains some hydrated material.

Hydrated Lime is the compound formed by the action of water or steam on fresh burned lime.

Air-Slaked Lime is a compound formed by the action of carbon dioxide from the air on hydrated lime, and its formula is CaCO₃, which is that of pure limestone.