But "constant washing wears away stones" and the potash that the metallurgist finds too hard to extract in his hottest furnace is washed out in the course of time through the dropping of the gentle rain from heaven. "All rivers run to the sea" and so the sea gets salt, all sorts of salts, principally sodium chloride (our table salt) and next magnesium, calcium and potassium chlorides or sulfates in this order of abundance. But if we evaporate sea-water down to dryness all these are left in a mix together and it is hard to sort them out. Only patient Nature has time for it and she only did on a large scale in one place, that is at Stassfurt, Germany. It seems that in the days when northwestern Prussia was undetermined whether it should be sea or land it was flooded annually by sea-water. As this slowly evaporated the dissolved salts crystallized out at the critical points, leaving beds of various combinations. Each year there would be deposited three to five inches of salts with a thin layer of calcium sulfate or gypsum on top. Counting these annual layers, like the rings on a stump, we find that the Stassfurt beds were ten thousand years in the making. They were first worked for their salt, common salt, alone, but in 1837 the Prussian Government began prospecting for new and deeper deposits and found, not the clean rock salt that they wanted, but bittern, largely magnesium sulfate or Epsom salt, which is not at all nice for table use. This stuff was first thrown away until it was realized that it was much more valuable for the potash it contains than was the rock salt they were after. Then the Germans began to purify the Stassfurt salts and market them throughout the world. They contain from fifteen to twenty-five per cent. of magnesium chloride mixed with magnesium chloride in "carnallite," with magnesium sulfate in "kainite" and sodium chloride in "sylvinite." More than thirty thousand miners and workmen are employed in the Stassfurt works. There are some seventy distinct establishments engaged in the business, but they are in combination. In fact they are compelled to be, for the German Government is as anxious to promote trusts as the American Government is to prevent them. Once the Stassfurt firms had a falling out and began a cutthroat competition. But the German Government objects to its people cutting each other's throats. American dealers were getting unheard of bargains when the German Government stepped in and compelled the competing corporations to recombine under threat of putting on an export duty that would eat up their profits.
The advantages of such business coöperation are specially shown in opening up a new market for an unknown product as in the case of the introduction of the Stassfurt salts into American agriculture. The farmer in any country is apt to be set in his ways and when it comes to inducing him to spend his hard-earned money for chemicals that he never heard of and could not pronounce he—quite rightly—has to be shown. Well, he was shown. It was, if I remember right, early in the nineties that the German Kali Syndikat began operations in America and the United States Government became its chief advertising agent. In every state there was an agricultural experiment station and these were provided liberally with illustrated literature on Stassfurt salts with colored wall charts and sets of samples and free sacks of salts for field experiments. The station men, finding that they could rely upon the scientific accuracy of the information supplied by Kali and that the experiments worked out well, became enthusiastic advocates of potash fertilizers. The station bulletins—which Uncle Sam was kind enough to carry free to all the farmers of the state—sometimes were worded so like the Kali Company advertising that the company might have raised a complaint of plagiarizing, but they never did. The Chilean nitrates, which are under British control, were later introduced by similar methods through the agency of the state agricultural experiment stations.
As a result of all this missionary work, which cost the Kali Company $50,000 a year, the attention of a large proportion of American farmers was turned toward intensive farming and they began to realize the necessity of feeding the soil that was feeding them. They grew dependent upon these two foreign and widely separated sources of supply. In the year before the war the United States imported a million tons of Stassfurt salts, for which the farmers paid more than $20,000,000. Then a declaration of American independence—the German embargo of 1915—cut us off from Stassfurt and for five years we had to rely upon our own resources. We have seen how Germany—shut off from Chile—solved the nitrogen problem for her fields and munition plants. It was not so easy for us—shut off from Germany—to solve the potash problem.
There is no more lack of potash in the rocks than there is of nitrogen in the air, but the nitrogen is free and has only to be caught and combined, while the potash is shut up in a granite prison from which it is hard to get it free. It is not the percentage in the soil but the percentage in the soil water that counts. A farmer with his potash locked up in silicates is like the merchant who has left the key of his safe at home in his other trousers. He may be solvent, but he cannot meet a sight draft. It is only solvent potash that passes current.
In the days of our grandfathers we had not only national independence but household independence. Every homestead had its own potash plant and soap factory. The frugal housewife dumped the maple wood ashes of the fireplace into a hollow log set up on end in the backyard. Water poured over the ashes leached out the lye, which drained into a bucket beneath. This gave her a solution of pearl ash or potassium carbonate whose concentration she tested with an egg as a hydrometer. In the meantime she had been saving up all the waste grease from the frying pan and pork rinds from the plate and by trying out these she got her soap fat. Then on a day set apart for this disagreeable process in chemical technology she boiled the fat and the lye together and got "soft soap," or as the chemist would call it, potassium stearate. If she wanted hard soap she "salted it out" with brine. The sodium stearate being less soluble was precipitated to the top and cooled into a solid cake that could be cut into bars by pack thread. But the frugal housewife threw away in the waste water what we now consider the most valuable ingredients, the potash and the glycerin.
But the old lye-leach is only to be found in ruins on an abandoned farm and we no longer burn wood at the rate of a log a night. In 1916 even under the stimulus of tenfold prices the amount of potash produced as pearl ash was only 412 tons—and we need 300,000 tons in some form. It would, of course, be very desirable as a conservation measure if all the sawdust and waste wood were utilized by charring it in retorts. The gas makes a handy fuel. The tar washed from the gas contains a lot of valuable products. And potash can be leached out of the charcoal or from its ashes whenever it is burned. But this at best would not go far toward solving the problem of our national supply.
There are other potash-bearing wastes that might be utilized. The cement mills which use feldspar in combination with limestone give off a potash dust, very much to the annoyance of their neighbors. This can be collected by running the furnace clouds into large settling chambers or long flues, where the dust may be caught in bags, or washed out by water sprays or thrown down by electricity. The blast furnaces for iron also throw off potash-bearing fumes.
Our six-million-ton crop of sugar beets contains some 12,000 tons of nitrogen, 4000 tons of phosphoric acid and 18,000 tons of potash, all of which is lost except where the waste liquors from the sugar factory are used in irrigating the beet land. The beet molasses, after extracting all the sugar possible by means of lime, leaves a waste liquor from which the potash can be recovered by evaporation and charring and leaching the residue. The Germans get 5000 tons of potassium cyanide and as much ammonium sulfate annually from the waste liquor of their beet sugar factories and if it pays them to save this it ought to pay us where potash is dearer. Various other industries can put in a bit when Uncle Sam passes around the contribution basket marked "Potash for the Poor." Wool wastes and fish refuse make valuable fertilizers, although they will not go far toward solving the problem. If we saved all our potash by-products they would not supply more than fifteen per cent. of our needs.
Though no potash beds comparable to those of Stassfurt have yet been discovered in the United States, yet in Nebraska, Utah, California and other western states there are a number of alkali lakes, wet or dry, containing a considerable amount of potash mixed with soda salts. Of these deposits the largest is Searles Lake, California. Here there are some twelve square miles of salt crust some seventy feet deep and the brine as pumped out contains about four per cent. of potassium chloride. The quantity is sufficient to supply the country for over twenty years, but it is not an easy or cheap job to separate the potassium from the sodium salts which are five times more abundant. These being less soluble than the potassium salts crystallize out first when the brine is evaporated. The final crystallization is done in vacuum pans as in getting sugar from the cane juice. In this way the American Trona Corporation is producing some 4500 tons of potash salts a month besides a thousand tons of borax. The borax which is contained in the brine to the extent of 1-1/2 per cent. is removed from the fertilizer for a double reason. It is salable by itself and it is detrimental to plant life.
Another mineral source of potash is alunite, which is a sort of natural alum, or double sulfate of potassium and aluminum, with about ten per cent. of potash. It contains a lot of extra alumina, but after roasting in a kiln the potassium sulfate can be leached out. The alunite beds near Marysville, Utah, were worked for all they were worth during the war, but the process does not give potash cheap enough for our needs in ordinary times.