Lime occurs very extensively distributed in nature, principally in combination with nitric, carbonic, and sulphuric acids—as in limestone, marble, chalk, gympsum, &c. Lime is looked upon by most chemists as being characteristic of the animal, rather than the mineral kingdom of nature. Thus, the skeletons of the vertebrated animals,—those animals the bony frame-work of which is uncased in the soft structures of the body—are composed mainly of the phosphate of lime, whilst the testaceous skeletons of the invertebrated animals are composed of the carbonate of lime, as is instanced in shell-fish—as the nautilus, sepia, &c The fluoride of calcium is also found in the bones and teeth of animals, both recent and extinct, and it is supposed by some chemists that the bones of fossil or extinct ani-malscontain more of this salt than those of animals now existing on the earth. All limestone rocks consist of nothing but the aggregated skeletons of myriads of microscopic animals, which have lived and died in countless numbers, long before the historic period. So true is this, that there is probably not a particle of limestone, marble, or chalk, that has not, at some period of the history of the world formed a part of the skeleton of some form of animated existence. All of the lime that forms a constituent part of the human skeleton has before performed the same office in the lower orders of animal life. Plants take it up rom the soil and hold it in solution in their juices, andthey in turn are consumed by animals, and after the death of the animal it is again returned to the mineral kingdom, to be, in course of time, the subject of similar mutations. The Sphinx and Pyramids of Egypt consist of a congeries of animal remains, being composed of the so-called nummulitic limestone ; this name is given to it on account of its containing millions of uni-valve shells, termed nummulites, from their resemblance to small pieces of money. Orfila, the great lecturer on poisons, supposed that the phosphoric acid which forms a constituent ot the bones of human beings, might be replaced by the arsenic acid, without injury to the health of the individual containing this poisonous skeleton, and warned medical men in making chemical examinations of the dead bodies of persons supposed to have been poisoned, to bear this fact in mind in conducting their analyses. The manner in which this might take place is best expressed by means of chemical symbols, thus 2 Ca.O., H.O.P.O5., 3Ca.O., P.O5., are the symbols for ordinary bone earth, but that containing the arsenic acid, in place of the phosphoric, would be written thus, 2Ca.O., H.O.As.O5, 3 Ca.O., As.O5. The nitrate of lime does not occur in the unstratified and metamorphic rocks, but is generally found where there has been, or is, animal matter in a state of decomposition, as in caves where bats and other animals congregate and die, as is instanced in the Mammoth Cave, Kentucky. This salt is also found in the sun-flower, tobacco, and other plants. The suits of lime occur in solution in almost all waters : thus the river, spring, and well water, in this vicinity, contained the sulphate of lime, as well as the carbonate, and when the season is dry, or there is a drought, the amount of lime salt is relatively much greater than at other times, from the concentration of the water. The presence of the salts of lime render water hard, as the phrase is, and this is particularly the case where the carbonate of lime is in solution. This so-called hardness of water can be very easily got rid of by a simple though interesting chemical process. Thus it requires two equivalents of carbonic aeid to render lime soluble in water, the proto-carbonate of lime, as it is called, being insoluble in that fluid, and if we add lime water to hard water, the extra equivalent of carbonic acid is removed in combination with the added lime, converting the whole into the proto-carbonate of lime, which I is precipitated, carrying along with it any co-I loring or organic matter that may be present, j This re-action is best stated in chemical sym-I bols, thus : Ca.0.2C.02+Ca.O.=2 Ca.O.C.O*.; j that is, one equivalent of the bi-carbonate of Llime, and one equivalent of lime, are resolved jnto two equivalents of the proto-carbonate of lime, which are thrown down as a precipitate. This process is found to be entirely successful when practiced on a large scale, and a knowledge of it, therefore, is of great importance in the arts and manufactures. Mus. Julia A. COOK. Cincinnati, 0.,May 30,1853.
This article was originally published with the title "Lime and Its Compounds" in Scientific American 8, 39, 307 (June 1853)