Page:Popular Science Monthly Volume 21.djvu/369

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357
BORAX IN AMERICA.

were entirely satisfactory, but in working large quantities the case was found very different. Concentrated to 20° B., a crop of crystals was deposited which were pure borax, but they were scarcely more than fifty per cent of the borax originally held by the lye thus formed. When, now, this mother-liquor was still further concentrated, no more pure borax separated, but a combined mass of borate and carbonate.

And here was manifested another feature. The amount of borax available depended very largely on the bulk of the solution in which it was allowed to cool. Very small quantities were of course useless in practical working, though the crop from them was satisfactory. Patiently continued trials showed that pans of two to three gallons gave economically the best results. But even here the borax clung so closely to the carbonate as to occasion much difficulty, until the plan was devised of crystallizing them together, and then washing away the carbonate by means of its greater solubility.

This was the plan adopted, and by its use about eighty per cent of the borax originally contained in the Hachinhama water, as pumped into the evaporating-pans, was secured. The extent of the works may be estimated from the fact that about 4,000 of the pans mentioned were in daily use.

But the unassisted lake-water was not long used. Hachinhama, from its shallowness, becomes nearly or quite dry at the close of each summer. As it dries away, the exposed mud is thickly covered with the salts deposited. These were carefully removed for use. The surface thus cleared of its salts began at once to renew its coating, the deposit being speedily replaced by capillary attraction from the stores beneath. In a week, or perhaps more, the surface was ready for sweeping again. The second crop was abundant, it was replaced by a third, and by others in succession, till the advent of the rains (never occurring in that climate till October, or perhaps November) put a stop to their formation.

This process was repeated each year during the occupation of Hachinhama, and, when the lake filled in turn with the winter rains, the alkaline-water bore the same degree of strength consecutively, showing that the stores of supply in the mud beneath gave no evidence of exhaustion.

The salts thus gathered were used by lixiviation to strengthen the lake-water in the evaporating-pans, and thus increase the yield of borax.

The work of refining the borax thus obtained differed in nothing from that employed with the green crystals of Borax Lake—hot solution and crystallization in lead-lined tanks. Hachinhama borax, as placed in the market, was of a grade of excellence never surpassed.

The works were conducted in this manner until the spring of 1872, when a change was introduced in consequence of the discovery that immense deposits of borates existed in Nevada. It was determined to