Verde Heritage 1924: OPENING OF THE CAMP VERDE SULPHATE MILL
"Steady shipments of salt-cake are being made from the sulphate of soda plant at Camp Verde and returns from the first cars indicate that the product is of higher grade than the paper and glass manufacturers have ever been able to secure before."
"As has been stated more than once in the 'Verde Copper News,' the Camp Verde deposit is unique in that it contains nothing but sodium sulphate, sodium chloride, and a small percentage of mechanical impurities such as clay and gypsum, these later amounting to approximately 3 per cent of the total and the chloride of sodium to 8 or 9 percent, leaving a residue of 88 per cent sulphate of soda."
"INDUSTRIAL USES: Sulphate of soda is familiar to almost everyone in the form of Glauber salt, largely used in medicine, cattle foods and other preparations. The Glauber salt, however, is crystallized and contains almost one-half its weight of water. To drive off this water of crystallization and so produce the pure sulphate would require a long and complicated process. The natural thenardite (the technical name for the mineral as deposited at Camp Verde) would have to be dissolved in pure water and the Glauber salt crystallized out. This would then have to be calcined to drive out the water of crystallization, after which the calcines would have to be ground to size. It is evident to the non-technical reader that this would prove a costly process and would involve several handlings of the product and a series of different processes, each of which would cost money. There would be no profit in the operation, at the present price of salt-cake, which is between $25 and $30 per ton, delivered."
"CAMP VERDE DEPOSIT: By a curious freak of nature, the deposit at Camp Verde is the only one known in which similar conditions exist. There are millions of tons of sodium sulphate in many parts of the world, but the salts are so mixed that their separation is possible only at prohibitive cost, just as if it were necessary to put the Camp Verde thenardite through the process described in the last paragraph."
"Taking the first illustration at hand, the famous Searles Lake in California is estimated to contain about as much sodium sulphate as has been developed at Camp Verde, but it is mixed with borax, potassium chloride, sodium carbonate and common salt and can be recovered only by a crystallization process. There are numerous other deposits similar to the one at Searles Lake, but all are in the same category --- a mixture of many salts that can be separated only with difficulty and at large expense."
"LE BLANC PROCESS: The salt-cake now on the market is produced by the famous Le Blanc process which starts with common salt and sulphuric acid. All the sodium sulphate produced on a commercial scale is made by this process and it has several defects, chief of which is that it simply can not be made completely acid-free, and this is one of the absolute requirements of glass makers. The sulphate produced artificially can not be made to show a purity of more than 96 or 97 per cent, and, unfortunately, the impurities are injurious in the highest degree, principally on account of the residue of acid."
"The local sulphate is absolutely anhydrous, that is, free from water, and it shows not the faintest trace of acid, this for the very simple reason that Dame Nature did not work by the Le Blanc process, but laid down the Camp Verde deposit from an ancient alkaline lake or possibly an arm of the prehistoric sea that at one time covered this section."
"CAN BE WASHED: The only question that required experimental solution was as to whether the salt and clay could be washed from the sulphate."
"A long series of laboratory experiments showed that it could, and a plant was designed to duplicate on a commercial scale the tests made in the laboratories. The company was fortunate in securing the services of Milton Staples as superintendent. He had designed and operated in California a plant to wash clay from rock salt which proved an immense success after several other engineers had failed. The same simple washing process is used at Camp Verde and has been even a greater success than was anticipated by Mr. Staples himself. Both the salt (sodium chloride) and the clay and other insolubles are so completely removed from the sulphate that the resulting product is better than 98 per cent pure --- from 2 to 3 per cent above the most stringent specifications for salt-cake."
"AMPLE MARKET: It may be added that there is a tremendous market for this product both here and abroad and the local plant is assured of steady capacity operation; in fact, plans are now being drawn for doubling the capacity of the plant which is designed to wash 300 tons per day although the crushing and drying plants can handle twice that amount."
"OTHER NON-METALICS: Arizona is literally full of other non-metallic minerals, none of which have been put to commercial use as yet. Vast deposits of pure gypsum have been located and are lying untouched and useless. Red and yellow ochers are known to exist in commercial quantities. Vast deposits of fullers' earth and argillaceous clays are known. Feldspar occurs freely in Mohave County and it is claimed to be one of the greatest deposits in the United States. An untouched treasure chest lies open to the scientific prospector and explorer. It is hoped and believed that the development of the Camp Verde sulphate deposit is but the beginning of a new era in the mineral history of the state."
(Verde Copper News; Tuesday, March 18, 1924; page 7.)