Chile today and tomorrow

by L. E. Elliott Joyce

Two North American firms own nitrate oficinas. The Dupont Nitrate Company operates two properties in Taltal from which about 30,000 tons are annually shipped, but since all this product goes directly to the Dupont explosives works in the United States, the market is not interested in the output. W. R. Grace and Company, doing a general export and import trade and employing their own steamers, operate nitrate works in Tarapacá, with a production of about 45,000 tons.

A few years ago pessimists prophesied that the Chilean nitrate fields would be exhausted by the year 1923. Careful examinations carried out by the national authorities as well as by individual companies have definitely allayed any fear of this kind. Surveys made under the auspices of the Chilean Government by the distinguished engineer Francisco Castillo showed that nitrate fields properly tested, owned and in operation, cover some 2244 square miles, while outside that area there are at least 75,000 square miles of undeveloped nitrate-bearing lands—chiefly in the hands of the Government of Chile. With, thus, over 95 per cent of the deposits untouched it is reasonable to expect a long life for this industry.

From the fields of Tarapacá and Antofagasta 60,000,000 tons of the chemical have been taken since the beginning of overseas exports, and it is estimated that in the comparatively small surveyed and operating area there are about 240,000,000 tons in sight, a quantity sufficient to fill the world’s needs for at least another century at the present rate of supply. This is without taking into consideration the huge body of less readily accessible nitrate lands referred to in Dr. Castillo’s conservative report, which included no deposits containing less than 17 per cent of nitrate, nor layers of less than twelve inches in thickness unless exceptionally rich.

The Caliche

Into the highly controversial question of the origin of the nitrate-bearing deposits it is unprofitable to go deeply, since, as in the case of petroleum, scientists have not agreed upon a theory. Several have been put forward, and a good deal of study and research has been devoted to the problem, but with no final result, a definite objection tripping up even the most likely suggestions. The most generally supported theory is that which was expounded in its original form by Darwin, postulating the long submergence of this part of the West Coast under the sea, its gradual rise through volcanic action, and the slow drainage and drying of masses upheaved from the Pacific floor. Remains of shell-fish are occasionally found imbedded in the caliche, and the presence of iodine is also adduced as contributory evidence; but bromine is curiously absent, and the question is complicated by other geological displays, some of which certainly seem to prove that before the subsidence of this belt in the Pacific the land was high and dry, clothed with thick forests.

I listened once upon a burning afternoon in the nitrate pampas to the seriously held theory that the caliche drained down, under the soil, from the mountains, and that the particular beds upon which my good friend was operating owed their origin to Lake Poopó, a turquoise gem near the railway line leading to Bolivia; the beds, it was insisted, seeped slowly from the lake and were being pushed up from underneath by subterranean pressure. Another theory credits the volcanos of the Andes with the production of sufficient ammoniated steam to create chemical changes upon the pampas; others suggest the union of oxygen and nitrogen in the air during electric storms, forming nitric acid which, in contact with lime, might produce nitrate of lime; this, if coming into touch with sulphate of soda, might form nitrate of soda, releasing the sulphate of lime.

He who prefers a less technical theory may agree that nitrogen deposits are derived from the guano of sea-birds, found along the Pacific coast.

The terminology of the nitrate pampas is a proof of its old recognition. The chuca is the loose, often friable, decomposed top layer, from two to twelve inches thick. Below it comes the costra, a hard, rocky agglomeration of cemented clay, porphyry and feldspar amalgamated with sulphates of calcium, potash and soda, often also containing traces of nitrate of soda and common salt. Third comes the tapa, the immediate shield of the nitrate of soda beds, composed of fragments of nitrate, of salt, sand and clay. These three layers form mattresses from a few inches to three or even six feet in depth, and owing to the hardness of the costra must be blasted away from the precious fourth layer, the caliche proper.

The caliche bed varies remarkably in thickness and in position, sometimes offering a thin, sand-mixed, layer of little value, and at other times revealing itself as a beautiful shining snow-white bed several feet in thickness; its hue varies from pure white to grey, sandy, and even violet, and its consistency may be sometimes loose and porous, while in other regions it is as hard as marble. The best caliche contains as much as 70 per cent of nitrate, and by the present methods of extraction it is not considered worth while to operate deposits containing less than 14 to 15 per cent. The average in Tarapacá and Antofagasta runs to about 20 per cent. Below the caliche is the conjelo, another fairly loose layer of sand and clay, salts, selenite crystals and traces of nitrate; still farther down is another plainly differentiated stratum, called the coba, with a comparatively high percentage of water, a heavy proportion of clay, calcium sulphate, and other minor components. The nitrate is often carried through several of the protecting layers, and foreign matter is frequently found mixed with the caliche, yet the different strata almost invariably exist in readily distinguishable and undisturbed beds.

The process of preparation for the market is simple. The caliche, thoroughly crushed by heavy machinery, is tipped into immense tanks and covered with water: coils of pipes fixed in these vats heat the mass to a high temperature and the nitrate of sodium, readily soluble in boiling water, dissolves. The other ingredients of the caliche fortunately are not so easily dissolved, and settle to the bottom of the tanks, so that when the water is drawn off and cooled the nitrate crystallises in a high grade of purity. There is a moment to be watched for in drawing off the liquor, however; common salt (sodium chloride) is frequently present in the caliche in unwanted quantities, dissolving with the same readiness as the nitrate. But it begins to precipitate before the nitrate, and the right time for withdrawing the liquor is when the salt has settled and the nitrate is immediately following it. The nitrate-charged water crystallises on the floor and sides of the shallow bateas (vats, generally of wood) into which it is passed, the process of cooling and crystallisation taking from 20 to 40 hours. The liquor is then pumped away, part being used for the manufacture of iodine according to the amount permitted to the oficina by the central Association, while the nitrate crystals are gathered in large pans for a few days for draining, and afterwards spread upon the cemented open planes, the canchas, for two weeks until thoroughly dry; it is then ready for bagging. It is during the drying stage on the cancha that nitrate in large quantities, all over the pampas, would be spoiled by dissolution if heavy rain should fall—a phenomenon of such rare and unlikely occurrence that it is not taken into consideration. The belt is not absolutely rainless, Iquique claiming a rainfall of half an inch per annum, while the Antofagasta Pampa has received showers four times in the last fifteen years; heavy fogs, too, not infrequently invade the pampas. But it would take a series of terrific deluges for moisture to filter through the protecting crusts above the caliche, and this sometimes suggested danger is not in sight.