The production from this district greatly increased in 1913 as compared with 1912, the increase amounting to more than 40 per cent. Much of the pyrite from this region is high grade and averages 45 per cent sulphur. UTILIZATION OF PYRITE RESIDUES. In 1913, 3,538,980 short tons of sulphuric acid of 50° Baumé, valued at $22,366,482, were made in the United States. Of this production, 790,296 short tons, valued at $4,346,272, represents byproduct acid, that is, acid made in connection with copper and zinc smelting. The difference, amounting to 2,748,684 tons, valued at $18,020,210, represents acid made from both domestic and imported pyrite. This acid is used in various ways, such as in the manufacture of superphosphates and explosives, in the refining of crude oil, and in making a host of chemical substances enumerated on a subsequent page. Practically all the last-mentioned quantity of acid is made from pyrite, marcasite, or pyrrhotite, the different sulphides of iron, which are roasted in various types of roasting furnaces, the product, sulphur dioxide, being subsequently oxidized and treated with water vapor or steam to form the final product. Pyrite contains 53.4 per cent sulphur and 46.6 per cent iron. Pyrrhotite, the other important iron sulphide and the mineral used at Pulaski, Va., contains usually from 38.4 to 39.6 per cent sulphur and from 60.4 to 61.6 per cent iron. Though the commercial pyrite now placed on the market does not contain the theoretical percentages of sulphur and iron given above, the figures approach near enough to the theoretical to make them of very practical interest. The average in sulphur content of the pyrite shipped from the Virginia pyrite mines ranges from 43 to 45 per cent. The following analyses show the general character of the Louisa County (Va.) pyrite, the fourth analysis being that of pyrrhotite from the southwestern part of the same State: Composition of Virginia pyrite and pyrrhotite. The residual material, after the sulphur is removed by burning, as will be observed from the analyses given above and from the domestic production of pyrite plus the imports, is large in quantity and for the most part constitutes the equivalent of a good grade of iron ore. Most of the calcined residue contains approximately 2 per cent of sul phur, and some contains enough copper to make its removal profitable either by leaching or by other means. The material which is sometimes called "blue billy" resembles a reddish-brown iron ore, and except for its comparatively high sulphur content, its occasional copper content, and its finely divided condition, would pass for an ordinary red iron ore. The problem, before utilizing the iron residues in the furnace, is to get rid of the comparatively large amount of sulphur which remains in the "blue billy" after as much sulphur as possible has been burned away as sulphur dioxide in the manufacture of the acid. This sulphur content is ordinarily much too high to permit the direct use of the residue in the manufacture of pig iron. The claim that many acid plants burn pyrite until the sulphur amounts to only 0.5 to 1 per cent is scarcely ever realized in practice and the pyrite cinder on the market contains, as a rule, 2 per cent or more of sulphur. "Blue billy" is therefore regarded as an undesirable iron ore and consequently brings a low price. Still another objection is the finely divided condition in which it comes from the acid factory, making it especially unsatisfactory where heavy blasts are used. This objection does not obtain where lump pyrite is used in the manufacture of acid, but here again such pyrite is apt to contain a larger content of sulphur than the fines. During recent years several attempts or installations have been reported using one process or another for desulphurizing these residues and smelting them for iron. With the eventual depletion of our iron ore reserves (although far removed), it seems quite probable that this tendency will increase and that in time pyrite cinder will not be wasted, as has been so long the case, but will constitute an important source of iron. A few of these installations have been described in this chapter in previous years. At the mines of the Pulaski Mining Co. in southwestern Virginia the procedure which obtained a few years ago, and which is presumably still in use, is as follows: The pyrrhotite is dead roasted; sulphuric acid is made, and the resulting cinder is used as part of the charge in an iron blast furnace. The ore is mined from open cuts; it is crushed and then conveyed to Herreshoff roasters. The cinder from these roasters is then clinkered in a 100-foot rotary cement kiln into which powdered coal is blown at the end opposite the feed. The pyrite cinder when fed to the kiln contains from 4 to 7 per cent sulphur; after going through the clinking process the sulphur content is reduced to 0.05 per cent. The cinder is sold to the Pulaski Iron Co., whose furnace is only a short distance away. At the plant of the Pyrites Co. (Ltd.), which is engaged in the manufacture of sulphuric acid from Rio Tinto pyrite, there has just been put into operation a 150-ton Dwight-Lloyd sintering machine for sintering the cinder. About 8 per cent of coke dust is mixed with the cinder; the cost of the operation is considerably less than in nodulizing in kilns, the sulphur being reduced from 2 to 0.04 per cent. There is a tendency at present to use copper-bearing steel for rails for railway service, and if the use of steel containing copper should increase it is not at all improbable that the burning of copper-bearing pyrite for the manufacture of sulphuric acid, nodulizing the residue, and smelting in the blast furnace to yield a copper-bearing pig iron will become an important phase of future practice.1 1 Min. and Sci. Press, July 26, 1913, p. 153. SULPHURIC-ACID INDUSTRY IN THE UNITED STATES. INTRODUCTORY NOTE. The year 1913 is the third for which statistics of sulphuric acid have been collected by the United States Geological Survey. As stated in the report for 1911, the first year during which such statistics were published, one of the reasons for adding the subject of sulphuric acid to the chapter on sulphur and pyrite is because it is a commodity so extensively used in the manufacture of other chemicals that it has come to be regarded as a criterion or gage of the activity of the country in chemical manufactures in general. Another reason of recent importance since the beginning of the manufacture of by-product acid in the copper and zinc smelting industry is that through sulphuric acid is offered the only means of expressing the value of the sulphur in those sulphides now used in making by-product acid-that sulphur which formerly went to waste in the air in the form of sulphur dioxide and sulphur trioxide. GENERAL USES. Sulphuric acid is probably used in a greater variety of ways in the chemical arts than is any other substance. According to Lunge1 the principal applications of the acid are as follows: 1. In a more or less dilute state (say from 144° Twad. downward).-For making sulphate of soda (salt cake) and hydrochloric acid, and therefore ultimately for soda ash, bleaching powder, soap, glass, and innumerable other products. Further, for superphosphates and other artificial manures. These two applications probably consume nine-tenths of all the sulphuric acid produced. Further applications are for preparing sulphurous, nitric, phosphoric, hydrofluoric, boric, carbonic, chromic, oxalic, tartaric, citric, acetic, and stearic acids; in preparing phosphorus, iodine, bromine, the sulphates of potassium, ammonium, barium (blanc fixe), calcium (pearl-hardening); especially also for precipitating baryta or lime as sulphates for chemical processes; sulphates of magnesium, aluminum, iron, zinc, copper, mercury (as intermediate stage for calomel and corrosive sublimate); in the metallurgy of copper, cobalt, nickel, platinum, silver; for cleaning (pickling) sheet iron to be tinned or galvanized; for cleaning copper, silver, etc.; for manufacturing potassium bichromate; for working galvanic cells, such as are used in telegraphy, in electroplating, etc.; for manufacturing ordinary ether and the composite ethers; for making or purifying many organic coloring matters, especially in the oxidizing mixture of potassium bichromate and sulphuric acid; for parchment paper; for purifying many mineral oils, and sometimes coal gas; for manufacturing starch, sirup, and sugar; for the saccharification of corn; for neutralizing the alkaline reaction of fermenting liquors, such as molasses; for effervescent drinks; for preparing tallow previously to melting it; for recovering the fatty acids from soapsuds; for destroying vegetable fibers in mixed fabrics; generally, in dyeing, calico printing, tanning, as a chemical reagent in innumerable cases; in medicine against lead poisoning, and in many other cases. 2. In a concentrated state. For manufacturing the fatty acids by distillation; purifying colza oil; for purifying benzene, petroleum, paraffin oil, and other mineral oils; for drying air, especially for laboratory purposes, but also for drying gases for manufacturing processes (for this, weaker acid also, of 140° Twad., can be used); for the production of ice by the rapid evaporation of water in a vacuum; for refining gold and silver, desilvering copper, etc.; for making organo-sulphonic acids; manufacturing indigo; preparing many nitro compounds and nitric ethers, especially in manufacturing nitroglycerin, pyroxylin, nitrobenzene, picric acid, and so forth. 3. As Nordhausen fuming oil of vitriol (anhydride).—For manufacturing certain organo-sulphonic acids (in the manufacture of alizarin, eosin, indigo, etc.); for purifying ozokerite; for making shoe blacking; for bringing ordinary concentrated acid up to the highest strength as required in the manufacture of pyroxylin; and for other purposes. 1 Manufacture of sulphuric acid and alkali, vol. 1, pt. 2, pp. 1169–1170, ed. 1903. The most important of the classes of manufacture enumerated above, so far as the consumption of the acid is involved, are in (1) the manufacture of fertilizer; (2) the refining of petroleum products; (3) the iron, steel and coke industries; (4) the manufacture of nitrocellulose, nitroglycerin, celluloid, etc.; and (5) in general metallurgical and chemical practice. PRODUCTION. The statistics of sulphuric acid have previously been collected at each census, beginning with the census of 1870; and at the censuses of 1889, 1899, and 1904, the quantity and value of each of the important grades were ascertained. The statistics of production in the tables which follow for the years prior to 1911 have been taken from the census reports for 1899 and 1904.1 In the production reported to the Survey for 1911, 1912, and 1913 all sulphuric acid is given regardless of whether it was sold as such or consumed in the factories where it was made. It is well known that nearly all the sulphuric acid made at fertilizer works is there consumed in the manufacture of superphosphates, that in factories where explosives are manufactured the sulphuric acid is combined with nitric acid and is used in making nitroglycerin and guncotton, and that, finally, in petroleum refineries much of the acid is consumed in refining the crude oil. In the earlier census reports the sulphuric acid consumed in establishments where manufactured and that produced by establishments engaged primarily in the manufacture of other products was listed separately, which is not done in the Survey's figures for 1911, 1912 and 1913, except in the case of the sulphuric acid manufactured at smelters as a by-product. Sulphuric acid is produced in several grades: (1) 50° Baumé acid, also known as chamber acid, containing an average of 50.76 per cent SO,, or 62.18 per cent H2SO1; (2) 60° Baumé acid, containing an average of 63.41 per cent SO,, or 77.67 per cent H2SO,; (3) 66° Baumé acid, known as oil of vitriol, containing approximately 76 per cent SO,, or approximately 93.19 per cent H2SO. Higher strengths of acid usually contain SO, dissolved in sulphuric acid; for example, pyrosulphuric acid and fuming or Nordhausen acid. Oleum is a grade which contains 30 to 60 per cent of free SO,, or a total of 87 to 92 per cent of free and combined SO,. It is essentially a solution of SO, dissolved in sulphuric acid.2 The production of sulphuric acid published by the Survey represents bona fide returns from producers, and the figures in the following tables are not estimates. For this reason the figures may be either equal to or less than the actual production. It is obvious that they can not exceed it so long as the returns are correct. In the following table the quantity, value, and price per ton are given of the three main grades of acid, and also similar data for other strengths of acid combined. With the exception of the quantity of acid indicated in the footnote the output is also expressed in terms of 50° Baumé acid for the sake of comparison. 1 Census of manufactures, 1905, Bull. 92, pp. 15 and following, 1907. Production of sulphuric acid in the United States in 1899, 1904, 1909, 1911, 1912, and 1913, by grades, in short tons. • Includes 764,355 tons, with an assigned value of $7,032,066, consumed in establishments where manufactured; and also sulphuric acid produced by establishments engaged primarily in the manufacture of other products. Reported as oleum by the census. Includes 968,445 tons, with an assigned value of $7,232,675, consumed in establishments where manufactured; and also sulphuric acid produced by establishments engaged primarily in the manufacture of other products. Includes 1,271,535 tons, with an assigned value of $6,694,436 consumed in establishments where manufactured; and also sulphuric acid produced by establishments engaged primarily in the manufacture of other products. Exclusive of acids of strength greater than 66° Baumé. Exclusive of electrolyte and acids of strength greater than 66° Baumé. • Exclusive of 22,947 short tons of fuming acid, not convertible, valued at $318,044. NOTES ON SULPHURIC ACID FIGURES. The pyrite imported for consumption during the calendar year 1913 (which must not be confused with the total imports for that year), amounted to 850,592 long tons, according to the Bureau of Foreign and Domestic Commerce. If to this figure of imports the domestic production of pyrite given in a preceding table, namely, 341,338 long tons, be added there results a total available for 1913 of 1,191,930 long tons of pyrite. On the basis of an average content |