The invention of gunpowder afforded man a means of utilizing the energy of chemical separation in effecting propulsion and of more efficiently applying this form of energy in mining and quarrying. Through the discovery or invention of mercuric fulminate, the cellulose nitrates, the glyceryl nitrates, the nitro-substitution compounds, and the various explosive compositions made from these nitrates and nitro-compounds, man was enabled also to utilize the energy stored up in unstable molecules. History indicates that the invention of gunpowder was made where saltpeter, which is its chief ingredient, was naturally most abundant and most easily obtained, but that, owing to the great value of gunpowder to man, its use and manufacture spread to the cooler and more humid countries and it is in these countries that it, and the other explosives enumerated, have come to be most extensively used. Statistics are not at hand by which to show the increase in the use of powder throughout the world, but some relative idea of this growth in recent years may be gained from Table 1, which sets forth the quantity, or value, or both, of the gunpowder, including, since 1860, blasting powder also, produced in the United States in each census year beginning with 1840.
The statistics for the world's production of the modern explosives are also not accessible but an item contributing towards the assembling of this valuable information regarding the world's progress was given for dynamite as sold from the several factories with which Alfred Nobel, the inventor of dynamite, was associated, though as there were, during the period covered, independent factories in Germany, in America, and, probably, in other countries, these figures, as set forth in Table 2, give only a relative idea of the growth of this industry.
TABLE I.—POWDER PRODUCED IN THE UNITED STATES.*
Census. Quantity
(pounds). Value.
1840 8,977,348 ……….
1850 (1) $1,590,332
1860 (1) $3,223,090
1870 (1) $4,011,839
1880 (1) $3,348,941
1890 95,019,174 $6,740,099
1900 124,824,473 $5,395,193
1905 215,820,144 $8,919,460
*Bulletin 92, Census of Manufactures, 1905, by Charles E. Munroe.
1 Not reports.
TABLE 2.—ANNUAL SALES OF DYNAMITE FROM NOBEL FACTORIES.*
Year. Tons. Year. Tons.
1867 11 1875 3,500
1868 78 1876 4,300
1869 184 1877 5,500
1870 424 1878 6,200
1871 785 1879 7,000
1872 1,350 1880 7,500
1873 2,050 1881 8,500
1874 3,120 1882 9,500
*Notes on Nitro-glycerine, Dynamite and Blasting Gelatine, by George McRoberts, Phil. Soc. Glasgow, Apr. 25, 1883.
TABLE 3.—QUANTITIES AND VALUES OF EXPLOSIVES PRODUCED IN THE UNITED STATES IN THE CENSUS YEARS 1900 AND 1905.*
1900 1905
Quantity. Value. Quantity. Value.
Gunpowder, pounds 5,450,773 $614,290 10,383,944 $1,541,483
Blasting powder, kegs1 4,774,948 $4,780,903 8,217,448 $7,377,977
Nitroglycerin, pounds 2 35,280,498 $5,532,570 3 51,579,270 $7,730,175
Dynamite, pounds 85,846,456 $8,247,223 130,920,829 $12,900,193
Guncotton, pounds 4 2,988, 176 $1,473,619 5 5,905,958 $2,435,805
Smokeless powder, pounds 3,053,126 $1,716,101 7,009,720 $4,406,477
All other explosives ….. $6,493 ….. $190,948
*Chemicals & Allied Products, by Charles E. Munroe.
1 A keg contains 25 pounds of blasting powder.
2 Including 31,661,806 pounds, produced and consumed, valued at $4,749,271.
3 Including 43,643,270 pounds, produced and consumed, valued at $6,110,058.
4 Including 2,139,834 pounds, produced and consumed, valued at $1,069,97.
5 Including 5,522,796 pounds, produced and consumed, valued at $2,209,118.
The most complete and detailed figures relative to the production of explosives to be found anywhere are those presented in the reports on the census of manufactures of the United States for 1900 and 1905, which are as follows, the gunpowder and blasting powder, which were combined in Table 1, being presented separately in Table 3.
It is an interesting and important fact that, as with gunpowder so with all of the other explosives enumerated, a nitrogen-containing compound is employed in the manufacture of each and nitrogen remains as a component or constituent of each product. The quantity of nitrogen in one hundred parts of these explosives, together with its equivalent in real nitric acid and in sodium nitrate, is shown, together with other data relative to these explosives, in the following table:
TABLE 4.-PER CENT OF NITRCGEN IN CERTAIN OF THE MORE IMPORTANT EXPLOSIVES.
1 Factory yields.
2 Using artificial refrigeration, vide Census Bull. No. 92 of 1905.
3 Nitrating in pots.
4 Nitrating in centrifugals.
In calculating the data for Table 4 the gunpowder is assumed to be composed of KNO3, 75 per cent; C, 15 per cent; S, 10 per cent and the blasting powder of NaN03, 74 per cent; C, 16 per cent; S, I0 per cent, but variations from these compositions will be found in practice. However, it is believed that they represent, very closely, the averages of all commerical compositions so styled. Although a most important explosive, dynamite is omitted from the table because the wide variations in the character and quantities of the components of this mixture as it occurs in .commerce render it impossible to properly represent it by an average formula.
It is true that it is usually admitted that on the average dynamite contains 40 per cent of nitroglycerol. The wide variation in nitrogen contents occurs in the dope or absorbent, which may contain from no nitrogen-containing component whatever, as in the kiesel-guhr dynamites, to 60 per cent of sodium nitrate in straight wood-pulp dynamites; and this last material may be partly or wholly replaced by ammonium or potassium or cellulose nitrates in other dopes and compositions. Because of a similar wide variation in their components the compositions made from picric acid, its salts, and other nitro-substitution compounds are also omitted. Notwithstanding these omissions, it is believed that the data set forth in the table may prove useful in the development and checking of the statistics of manufacture. But, unfortunately, owing to the different manners in which the nitrogen atoms are grouped, as regards the other atoms, in the molecules of the different kinds of explosives, no direct relation is to be observed between the properties and behavior of these different bodies and the percentages of nitrogen they contain, and this want of relation becomes the more marked the larger the number of different nitrogen-containing substances that we consider. What, however, is emphasized by this presentation of data, is that the element nitrogen is a characteristic and important component of all explosives that have been accepted and used for military purposes.
From the time of the invention of gunpowder, until the middle of the last century, the only recognized available source of this nitrogen was India saltpeter, which is the potassium nitrate, and which was obtained from the niter found or formed in soil or rocks. The production of nitrates in the soil or rocks is brought about usually through the agency of nitrifying bacteria. In order that the process of nitrification may go on there is required a supply of nitrogenous organic matter, a slightly alkaline medium, a temperature range between definite limits, a limited amount of moisture, a supply of oxygen or air, complete or semi darkness, and the presence of the nitrifying organisms. The nitrification proceeds most rapidly at I00°F. and within a few inches of the surface of soil or rock which is well aerated and moderately moist. When potash salts are present in sufficient quantity the potassium nitrate is produced, but the native niter usually consists largely of calcium nitrate with some magnesium nitrate and other salts. All of these nitrates are readily soluble in water and may therefore, after formation, be to a great extent washed away by frequent rainfalls, but where there is only a moderate amount of water present the solution may be brought to the surface by capillarity and as the water evaporates the nitrates will be left as an efflorescence on the surface of the soil or rock. It is evident, therefore, that accumulations of niter will be largest in those localities where not only the best conditions for its production obtain, but where also it is least likely to be washed away after being formed. The native sources of supply are therefore found as efflorescences on the soil in semi-arid countries; in limestone caverns, where the remains and excreta of bats are the chief source of the organic matter; and about stables.
Since the amount of niter procurable from these sources was limited it became necessary, as the demand for saltpeter increased, to resort to other sources of supply and consequently niter plantations were established in many countries, where, following the principles set forth above, the niter was formed and protected from the weather. Desortiaux1 describes in detail the saltpeter plantations of Hungary, Switzerland, France and Sweden. Such farms have been carried on in this country, especially in the Southern States during the Civil War, and the means resorted to by John Harrolson, of Selma, Alabama, to secure the necessary nitrogenous organic matter for these farms became particularly widely known. In emergencies, as in Sweden in 1520, the earth of cemeteries has been lixiviated to obtain niter and in this last mentioned country a tax was imposed in 1642 which had to be paid in saltpeter.2
About 1821 the naturalist, Mariano de Rivero, found on the Pacific coast of South America, in the province of Tarapaca, immense deposits of sodium nitrate.3 As this salt had prior to this been known only as a laboratory product the discovery was of marked scientific interest, which became an economic one when in 1830 the material was mined for exportation and 8348 tons were shipped in that year. Investigation has shown that this deposit extends for some 450 miles north and south in the arid plains which lie between the western slope of the Andes Mountains and the coastal range on the Pacific, at altitudes of from 3600 to 13,000 feet and at distances of from 15 to 93 miles from the sea. The exploitation of this deposit has been pushed to such an extent that in the year ending December 31, 1908, there were shipped from the various South American ports contiguous to this field 1,993,000 tons of the nitrate of soda, and because of the export taxes levied upon this material and the payments required for concessions to operate in this desert tract, this industry has been, and still is, a rich source of revenue to the Chilean government. The extent to which this industry has grown and its rate of growth are clearly set forth in the following table prepared by F. V. Vergara,4 collector of customs at the port of Valparaiso:
TABLE 5.—SODIUM NITRATE EXPORTED FROM CHILE 1840-1903.
Period. Exports Tons.* Annual Av. Tons.*
1840-1844 73,232 14,646
1845-1849 94,806 18,961
1850-1854 149,960 29,922
1855-1859 259,394 51,879
1850-1864 327,034 65,407
1865-1869 487,324 97,465
1870-1874 1,095,628 219,083
1875-1879 1,365,418 273,083
1880-1884 2,220,926 444,185
1885-1889 3,318,520 6663,704
1890-1894 4,813,670 962,734
1895-1899 6,204,636 1,240,927
1900-1903 5,537,396 1,384,349
* Metric tons of 2204 pounds.
1Traité sur la poudre, les corps explosifs et la pyrotechnic, Vol. I, 15-117,
1878.
2The Manufacture of Explosives, 0. Guttmann, Vol. I, p. 24, 1895.
3Principles and Practice of Agricultural Analysis, H. W. Wiley, Vol. I,
P. 16, 1894.
4Monthly Bulletin International Bureau of American Republics, Nov.,
1903, p. 1290.
This material was not only cheap and relatively abundant, but, as previously shown,5 the richest known source of oxygen for use in explosives. It is not surprising, therfore, that its use for this purpose has rapidly grown. Nitrate of soda was first used in blasting powder in 1856 and a patent for such a powder was issued to La Motte Dupont in 1857. During the census year 1905, there was produced in the United States 205,436,200 pounds of blasting powder, most of which was nitrate of soda powder, and large quantities of this powder were manufactured and consumed in Chile and other countries.
5Lectures on Chemistry and Explosives, p. 2, 1888, by Charles E. Munroe
As nitrate of soda is quite deliquescent it is not suitable for direct use in the compounding of gunpowder, but early after becoming available in commerce it was made a source of manufacture of saltpeter. It was during the Crimean War (1854-55) that this industry was established in Germany, the sodium nitrate being converted into potassium nitrate by means of potassium carbonate obtained from the residues of sugar beets, and this assisted in the promotion of the beet-root sugar industry which Germany was seeking to foster.
Singularly, about this time the now famous deposit of potassium salts was discovered at Stassfurt, Germany. This town was noted for its salt works in the beginning of the 19th century, the source of supply being the natural brine from driven salt wells. With the utilization of rock salt deposits in various localities, the price of salt was reduced to such a point that the Stassfurt works ceased to yield their former large revenue to the Prussian government, and, with a view of making them again valuable, the government began boring for rock salt in this locality in 1839. In 1857 a shaft, which began in 1852, reached, at a depth of 1080 feet, a stratum of rock salt, but in doing so it passed through a heavy deposit of so-called "Abraum-salze" or refuse salts, which were then considered worthless. The "Abraum-salze" were found to consist largely of the minerals carnallite, which is a magnesium-potassium chloride; sylvite, which is potassium chloride; and kainite, which is a mixture of carnallite and magnesium chloride, and these refuse salts are to-day the chief source of the world's supply of potashes and potassium salts. Numerous uses have been found for them, not the least interesting of which is the production of saltpeter from the metathesis of the Chile nitrate with the Stassfurt sylvite or carnallite. In the United States alone there were produced 14,468,000 pounds of potassium nitrate by this means during the census year 1905, and this operation has been conducted here for many years. It is by such means that the Chile deposits have been made to render the saltpeter essential for use in sporting and military powders.
It has already been shown that the manufacture of dynamite consumes large quantities of nitrate of soda, and it has been also shown that the modern explosives, pyroxylin, gun cotton, picric acid and nitroglycerol, require for their manufacture a larger quantity of sodium nitrate, or of any other nitrate, as a source of the required nitrogen, than gunpowder does, while mercuric fulminate requires nearly as much. It may, therefore, be safely asserted that but for the discovery and exploitation of the nitrate fields of Chile the explosives industry, as it is known to-day, would have been impossible, and the developments in mining and transportation, which have characterized the last half-century, could not have been made. That is, the condition of civilization amid which we now live could not have been attained.
Yet the explosives industry is but one of several in which nitrate of soda is used. The relative quantities used in various countries differ. Unfortunately no detailed and accurate statistics can be had except for the United States. Omitting the minor industries of enamelling, fluxing in metallurgy, pickling of meats and fish, and the manufacture of subordinate chemicals in which approximately 23,926 short tons were used during the census year 1900, and 67,937 short tons in 1905, the quantities consumed in various industries were as follows:6
TABLE 6.—NITRATE OF SODA CONSUMED IN THE UNITED STATES BY ESTABLISHMENTS CLASSED AS FOLLOWS :
Class 1900. 1905.
Short tons. Short tons.
Fertilizer industry 19,518 42,213
Dyestuffs industry 223 261
General chemicals industry 35,990 38,048
Glass industry 10,770 11,915
Explosives industry 88,524 133,034
Sulphuric, nitric and mixed acids industry 27,406 29,301
182,431 254,772
It thus appears that of the total available supply of nitrate of soda in the United States but 42.90 per cent was used at the census of 1900, and 41.22 per cent at the census of 1905, in explosives factories and of this a notable portion was used in the manufacture of saltpeter which was sold for other uses in the arts. While all the industries enumerated show a growing demand the largest increase in any single industry is found in the fertilizer industry, where 22,695 tons, or 116.2 per cent, more of nitrate were used at the census of 1905 than were used at that of 1900.
6Journal of Industrial and Chemical Engineering, 1, 298, 1909, by Charles E. Munroe.
While no detailed statement of the consumption of nitrate of soda elsewhere is available, there is issued semi-annually by W. Montgomery & Co., Ltd., of 63 Mark Lane, London, a statement of the total shipments, consumption, stocks and prices of this article during a considerable period and the following data are derived from their circular statement for December 31, 1908:
TABLE 7.—CONSUMPTION OF NITRATE OF SODA IN 1908.
Locality. Tons.
United Kingdom 104,000
Continent of Europe 1,272,000
United States 309,000
Other countries 45,000
Total 1,730,000
From this it appears that of the total consumption of the year but 17.8 per cent was consumed in the United States. Analyzing the statement for the previous eight years, it appears that of the total, that consumed in the United States was, in 1900, 12.6 per cent; 1901, 14.1 per cent; 1902, 16.9 per cent; 1903, 18.76 per cent; 1904, 19 per cent; 1905, 19.9 per cent; 1906, 21.7 per cent; 1907, 21.1 per cent, so that there was a steady increase in the proportion of the total consumed in the United States up to 1906, but that for the next two years there was a drop such that in 1908 our proportionate consumption was less than for any year since 1902.
It is commonly understood that a much larger percentage of the Chilean nitrate is used in agriculture in Europe than is used in this industry in the United States, and that the proportion is steadily increasing. This use of nitrogenous fertilizers is in conformity with the teaching of Baron von Liebig, whose views have become gradually disseminated among the farmers. A marked impetus was given to this use of the Chilean nitrate by the remarkable address made by Sir William Crookes before the British Association for the Advancement of Science in 1898, when, in dealing with the problem of meeting the rapidly increasing demand for food, he pointed out that while the average yield of wheat was but 12.7 bushels per acre it had been demonstrated that the yield could be increased to 20 bushels by the use of 1½ cwt. of nitrate of soda on each acre annually.
This increasing use, however, tends to exhaust the supply. Crookes estimated that if the nitrate were used over the whole area under cultivation at the rate he proposed, the Chilean deposits would be exhausted in four years. Vergara7 estimated that at the rate that the nitrate had been mined and exported between 1840 and 1903, as shown in Table 5, the Chilean deposits would be exhausted by 1938. Albert Hale, however, in a more recent review of the situation,8 points out that these estimates were based on the contents of the deposits then known in the province of Tarapaca, and the extent to which they could be profitably worked, and states that deposits of such magnitude have since been discovered in the provinces of Antofogasta and Atacama, and the processes of recovery of the nitrate from low-grade ore (caliche) have been so improved that, at a rate of consumption of 5,000,000 tons annually, which he expects will be the normal demand in a few years, there is enough nitrate in these deposits to last three hundred years.
This is a more encouraging outlook, but, nevertheless, from what has been said it is evident that the world has for long been largely dependent on these Chilean deposits for the greater part of its supply of nitrate and the substances derived from it. In time of prolonged war, in case nitrate has become contraband, most countries have been obliged to resort to the vicious policy of niter farming, or, as our Navy Department has done since 1863, have accumulated in advance considerable stores of niter, and this condition would have continued to hold but for important advances recently made in the production of nitrate from atmospheric nitrogen, and through other developments in chemistry.
We have in our atmosphere an abundant supply of this element. It is estimated that the air over each acre of ground contains 33,880 gross tons of nitrogen. It is, however, free, and to be available for use it must be combined. The methods for effecting the fixation of this nitrogen have proceeded along three lines: (1) The production of nitric acid and nitrates, (2) The production of cyanides, and (3) The production of amids, and the first and last have now been brought to commercial success.
7Loc. cit.
8Bull. International Bureau of American Republics, p. 27, July, 1908.
As early as 1755 Priestly had noted that nitrogen compounds were formed when electric sparks were passed through air, and not long after Cavendish produced saltpeter by absorbing air, so treated, in caustic potash solution. Repeated attempts have been made since high potential currents have become readily available to utilize this method and an establishment was erected at Niagara Falls, by the Atmospheric Products Co., to operate the Bradley and Lovejoy process. This method, for which a U. S. patent was granted September 30, 1902, consisted in producing in the air a flaming electric arc of minimum volume by the rapid rotation of electrodes carrying high tension currents, but while it yielded nitric acid the method proved too costly.
A more successful device was shortly after put into operation by Birkeland and Eyde9 at Nottoden, Norway, and it has been in operation ever since. In this the flaming arcs produced by high tension currents were made to move to and fro through the air within the apparatus by exposure to powerful magnets. This apparatus was characterized by a narrow chamber through which the air was passed and within which the electrodes, placed near together, were arranged between the poles of a strong magnet and at right angles to these poles. A disk-shaped or deflected electric arc was thus obtained perpendicular to the lines of force of the magnetic field. Three such furnaces at Nottoden, using 500 kilowatts and 5000 volts, gave deflected arcs about 3 feet in diameter. The nitrogen oxides formed were quite dilute and they were carried to absorption towers where, by contact with milk of lime, calcium nitrate was formed, the product being eventually converted into basic calcium nitrate for use as a fertilizer. According to O. N. Witt,10 with this apparatus an output of 500 to 600 kilos of nitric acid per kilowatt year can be regularly maintained.
A still more efficient form of furnace is that devised by Dr. Otto Schoenherr for the Badische Anilin and Soda Fabrik. From his lecture, delivered June 11, I908, before the Verein Deutscher Chemiker at Jena, it appears that what is sought in these processes is to burn the nitrogen with the oxygen of the air. To accomplish this to any satisfactory degree the gases must be exposed to a temperature of 3000°C. and upward. To prevent the decomposition of the product formed it must be immediately removed to a cooler region. This Birkeland and Eyde accomplish through moving the arc to and fro by the aid of magnets, while Schoenherr effects it by imparting to his air a gyratory motion about his elongated arc. His apparatus consists of a long iron tube in which an arc 5 meters in length, produced by an alternating current, is maintained constantly, the energy required being about 600 H. P. and the alternations being 50 per second. Air, which has been heated to 500°C. by the hot discharge gases, is blown tangentially into this tube so that it surrounds the arc spirally in its passage through the tube. This prevents the deflection of the arc, permits of the maximum exposure of the air to the heat from the arc and promptly sweeps the heated and reacting air to the cooler portion of the tube and beyond. A 2000 H. P. plant of this character has been in operation at Christianssand. Norway, since the autumn of 1907, and its success has been such that the building of a 120,000 H. P. plant of this character has been undertaken at Rukwan Falls, Norway. The advantage claimed for this process is that it gives a good yield of concentrated gas.
9The Electrochemical Problem of the Fixation of Nitrogen, Phillippe A. Guye, J. Soc. Chem. Incl., 25, 567, 1905.
10Chemiker Industrie, 28, 699, 1905.
The third method for the fixation of atmospheric nitrogen referred to above has been brought to a successful realization by Frank and Caro in their production of calcium cyanamid mixed with carbon or lime nitrogen, or nitrolim, as it is more recently called. This is produced "by heating calcium carbide in vertical iron retorts in an atmosphere of nitrogen, when the calcium cyanamid, mixed with carbon, is formed according to the following equation:
CaC2+N2 à CaCN2+C.
The nitrogen is obtained by liquefying the air and separating its constituents by fractional distillation, or by passing the air over heated copper, by which the oxygen is removed from it and the nitrogen separated. A plant with a capacity of nearly 4000 tons per year was started at Piano d'Orta, Italy, in 1906, and with such success that the production was carried in 1908 to over 40,000 tons per annum in five plants, with others building. The material as produced is used directly as a fertilizer, but it is a simple matter to obtain ammonia from it and by a contact process this may be directly converted into nitric acid.
11Report on Calcium Cyanamid, Charles E. Munroe, Washington, April 27, 1907.
Yet another indirect source of supply of nitric acid and, therefore, of saltpeter is found in the manufacture of coke, for an important product of the by-product coke industry is ammonia, which is obtained usually nowadays as ammonium sulphate. I have elsewhere shown12 that 15,773 tons of ammonium sulphate were produced in this country in 1905. But as only 3,317,585 tons of the 37,376,251 tons of coal coked in the census year were coked in by-product ovens it was possible, had all been so treated, to have obtained 359,560 tons of ammonium sulphate, all of which if desired could have been converted into nitric acid for use in the manufacture of saltpeter or of any desired variety of explosive.
From this account of recent chemical progress it is evident that it is possible to conduct a prolonged war without robbing the soil on which the people depend for food of its fertility, and further that, notwithstanding the enormous and constantly increasing demand for nitrogen compounds in agriculture and manufacture, this country has reached a degree of independence, as regards its supply of nitrogen compounds for military uses, such as it never before enjoyed, so that it needs hereafter to consider foreign sources of supply only from the economic standpoint However, I desire to say regarding the plants for the fixation of nitrogen what I have repeatedly advised regarding plants for the manufacture of explosives, viz.: that it is a wise policy for our government to foster, and in a measure supervise, these manufacturing operations, and to look to it that plants for these purposes are so strategically located throughout the country as to be reasonably well protected from attack, so that they may serve the military establishment in case of foreign invasion from any quarter, or of internal uprisings in any locality.
12Bulletin No. 65, Census of Manufactures, 1905, Coke, p. 18, by Charles E. Munroe.