1832
JOURNALOF' CHEMICAL EDUCATION
AUGUST.
1930
THE RELATION OF COTTON TO EXPLOSIVES*
The Discovery of Guncotton in 1846 Attributed to Schonbein The discovery of guncotton by Schonbein (1)in 1846 is an historical fact of interest to both the Division of Cellulose Chemistry and the Division of Chemical Education of the American Chemical Society. Schonbein was professor of chemistry at Basel (French, Bale), Switzerland. He announced his discovery of guncotton on May 7, 1846, a t a meeting of the Society of Scientific Research at Base1 ( 2 ) . While Pelonze, who had reported the action of nitric acid on paper, linen, and cotton fibers in 1838 (3), disputed Schonbein's claims to discovery, the explosives industry generdlly regards the latter as the discoverer because Schonbein was the first to ni* Contribution to the symposium on "The Relation of Cotton to Chemistry,'' held jointly by the Division of Cellulose Chemistry and the Division of Chemical Education. at the 79th Meeting of the A. C. S., at Atlanta, Georgia, April 9, 1930.
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RELATION OF COTTON TO CHEMISTRY
1R33
1834
JOURNAL OF CHEMICAL EDUCATION
Aucusr, 1930
trate cotton in a mixture of sulfuric and nitric acids and the first to actually use guncotton both as a propellant in guns and as an explosive in mines. Schonbein did not realize the hazard involved in the manufacture and storage of guncotton. He wrote to Dumas of France about his discovery in part as follows: The manufacture is not attended with the least danger, and d w s not require any costly installat~ons.
Work of Walter Crum, Scotland, 1847 Reference should be made to the work of Walter Crum of Scotland (4) who showed that guncotton was quite different from the nitrostarch discovered by Braconnot and further investigated by Pelouze. Crum's work is of particular interest because he devised the method which is now in universal use for the analysis of nitrates, nitric acid, and nitrocellulosethe decomposition of the nitrate by sulfuric acid in the presence of mercury to give nitric oxide, the volume of which Crum measured, as is done today in the nitrometer. In the above-mentioned article Cmm stated: The cotton I used was fine Sea Island. It w a s first thoroughly carded and then bleached by boilidg in caustic soda and put in a solution of bleaching powder; then caustic soda again md afterwards weak nitric acid. When burnt 10,000 parts left 9 of ash. The cotton was exposed in parcels of 10 grains each for several hours t o the heat of a steam-bath, and each parcel was immersed, while hot, into a 1-ounce measure of the following mixture: sulphuric acid (1 84) 1 measure and 3 measures of pale lemon colored nitric acid (1.517).
. ..
...
It is hardly necessary to mention before an Atlanta audience that the best "Sea Island" cotton that is raised anywhere in the world is a product of the State of Georgia. Early Manufacture of Guncotton in England and on the Continent Schijnbein entered into an arrangement with Bottger, who in August of 1846 independently discovered guncotton, so that the latter would also share in the profits of the invention. He visited England where, assisted by the able engineer, Richard Taylor, numerous tests of guncotton were made in the mines of Cornwall and in small arms and guns. Negotiations were concluded with Messrs. John Hall and Son of Faversham, for the manufacture and sale of guncotton in England. The guncotton factory erected was destroyed by a disastrous explosion on July 14, 1847, and never rebuilt (5). Two explosions in France the following year stopped the manufacture in that country. A German commission, of which Liebig was a member, reported unfavorably, pronouncing guncotton unstable, of uncertain force, and too expensive.
VUL.7, No. 8
RELATION OF COTTON TO CHEMISTRY
1835
All investigations were discontinued except that of Baron Von Lenk, of the Austrian Artillery, who worked out the production of guncotton on a manufacturing scale in a factory erected a t Hirtenberg, Austria. Von Lenk nitrated hanks of loose cotton yarn for 48 hours in stoneware pots. The excess acid was then wrung out in a centrifugal machine, the guncotton drawned and then washed for a period of three weeks. The skeins were centrifuged to remove bulk of water, boiled for 15 minutes in dilute potassium carbonate solution, and finally washed for several days. The guncotton magazine a t Hirtenberg exploded July 30, 1862, on account of spontaneous decomposition, and after another serious explosion on October 11, 1865, the manufacture of guncotton was officially prohibited in Austria (5). Furthermore, the attempts to use the uncolloided guncotton as the propellant in guns were disastrous, the barrels bursting from the too rapid rise in pressure. Frederick Abel of England Introduces Pulping Treatment The unfortunate experiences cited above did not deter the English chemists from developing the industry. Early in 1863 Frederick Abel was requested by the British Government to take up the study of guncotton and its manufacture ( 6 ) . The manufacture of guncotton was commenced a t Waltham Abbey, England, in 1863 on a small scale, but i t was not until 1872 that a factory capable of producing 250 tons a year was established there. Abel concluded that the instability of guncotton was due t o the difficulty of washing out the acid and introduced the pulping process by which the guncotton was pulped in a beater and then given a prolonged washing treatment. Simple as it may seem, this was an important discovery, making the nitrocellulose safer to handle and store. Also the wet pulp could be compressed into blocks which were convenient for transportation and use. In 1872 E. A. Brown, who was Abel's assistant, discovered that these wet guncotton blocks could be fired by a small primer of dry guncotton and the dry guncotton by a fulminate detonator (7). These slabs of wet compressed guncotton for many years were the standard explosive for military demolition and for mines and torpedoes until largely replaced by T N T and other high explosives. Stabilization of Nitrocellulose by Boiling In 1873 boiling vats were installed a t Waltham Abbey and in 1878 the guncotton received two boilings by steam in wooden vats for eight hours each with change of water (6). I n April, 1894, this system was replaced by a boiling cycle of 78 hours, characterized by short boilings a t the commencement of the process, the time of successive boilings being gradually increased.
AUGUST, 1930
JOURNAL OF CHEMICAL EDUCATION
1836
Stabilization by Acid Hydrolysis This system of boiling was continued until 1905, when Robertson showed that the unstable sulfuric esters are decomposed more rapidly by boiling in acid water than by boiling in alkaline water (8). So today the stabilizing of nitrocellulose is characterized by long boilings in acidulated water, followed after pulping by alkaline and fresh water boils and numerous washings with fresh water. Nitrocellulose for smokeless powder manufacture receives a total boiling treatment of 52 hours and upward, requiring large expenditure for plant installation, steam, water, and labor. A more economical process for the stabilization of nitrocellulose is very much desired, particularly by manufacturers of smokeless powders, who give nitrocellulose a longer stabilization treatment than other users of nitrocellulose. Nobel Invents Blasting Gelatin, 1875 The success which attended Sir Frederick Abel's work on the purification of guncotton led to renewed interest and a few years later there were discoveries of great importance to the explosives industry, one of great importance to the development of high explosives and the other of vital importance to the smokeless powder industry. Nobel (9) in 1875 found that nitroglycerin could be gelatinized by dissolving in it nitrocellulose of the soluble or collodion type. The explosive compound became more and more gelatinous in proportion to the quantity of nitrocellulose dissolved in the nitroglycerin and when from 7 to 8 per cent was present, a solid jelly was formed which was found to he highly suitable as a powerful explosive. This type of explosive came to be known as blasting gelatin, a typical composition being Nitroglycerin Nitrocellulose Chalk
91 parts 8 parts 1 part
The gelatinizing property of nitroglycerin for soluble nitrocellulose was later made use of in the type of explosive commonly called gelatin dynamite. In view of the brisant properties of blasting gelatin, attempts were early made to modify the same by the addition of other materials. These additions consisted of potassium, sodium or other nitrate, wood meal or other absorbent, with a small amount of chalk added to neutralize any traces of acid. A typical composition given by Naoum (10)is
Dope
{ {
Nitroglycerin Soluble Nitrocellulose Saltpeter Wood Meal
63.25 to 61.5% 1.75 to 3.5% 27.0 to 28.0% 8.00 to 7.0%
65%
1
35%
The manufacture of blasting gelatin and gelatin dynamite requires a special type of nitrocellulose. This is similar in $om? respects as regards nitrogen
VOL.7, NO.8
RELATION OF COTTON TO CHEMISTRY
1837
content and solubility in various solvents to nitrocellulose used for lacquers, but differs from the latter largely in that the viscosity is very high, while that for lacquers is very low. This high viscosity and other desirable properties have to date been only attainable using cotton linters of the best grade, in fact no other source of cellulose has been seriously considered for making nitrocellulose for use in blasting gelatin and gelatin dynamite. Invention of Colloided Smokeless Powder The second important discovery which has led to the extensive use of cotton was the invention of smokeless powder. The attempt to use uncolloided guncotton as the propulsive force in large guns led to disaster; the guns burst, due to the explosive action of the guncotton. The first smokeless powder after Von Lenk's guncotton batteries was introduced by Schultze in England in 1865. It consisted at first of pellets of wood which were nitrated and then impregnated with barium and potassium nitrate, but later wood pulp was nitrated. Volkman five years later partly gelatinized the nitrated wood pulp by treatment with a mixture of ether and alcohol. The gelatinization of the nitrocotton by ether and alcohol controlled the rate of burning of the guncotton or, in other words, caused the gelatinized nitrocotton to bum more progressively. Fist
Mi-
Smokeless Powder by Vieille
The first smokeless military powder was Poudre B, named after General Boulanger, invented by the French chemist Vieille in 1886 while working in the laboratories of the French Government. This powder was made by forming a dough of nitrocotton colloided by a mixture of ether and alcohol, which was then rolled into sheets, cut up into strips, and dried. Later the dough was pressed through dies into strips which were cut up and dried. The abandonment of black powder and the substitution therefore by the French Govemment of a new and efficient smokeless powder attracted the attention of all civilized powers. Efforts to achieve similar results were at once inaugurated in other countries and the period of inactivity which followed the abandonment of efforts to employ guncotton as a propellant gave way to one of marked activity in all that related to the study of explosives. "Pyrocollodion Powder" of MendelBeff, Adopted by Russia The Russian Govemment commissioned Prof. Mendel&&, of Periodic Law fame, to conduct a series of researches with a view to the production of an efficient smokeless powder for Russia. As a result Prof. Mendel&& developed a powder called by him "pyrocollodion" which proved satisfactory, and which was adopted in Russia. The nitrocellulose had a nitrogen content of 12.40% and was completely soluble in ether-alcohol.
1838
JOURNAL OF CHEMICAL EDUCATION
Aucusr, 1930
EARLY POTSYSTEM OF NITRATING COTTON AT CARNEY'S POINT,DU PONT'SN. J. PLANT Pot nitrating house.
Ballistite and Cordite In 1888 Nobel introduced Ballistite, made by gelatinizing soluble nitrocellulose of low nitration with nitroglycerin, and in the same year the British Government introduced Cordite, made by gelatinizing insoluble nitrocotton of high nitration with nitroglycerin and acetone. Adoption of Smokeless Powder by United States, 1899 The United States adopted smokeless powder for military use in 1800 shortly after the Spanish-American War. The powder adopted by both the United States Army and the United States Navy was of the nitrocellulose type, the nitrocellulose having a nitrogen content between 12.5G 12.70% and commonly referred to by those manufacturing it as Pyro. In 1908,0.4% of diphenylamine was added as a stabilizing agent. Cotton, the Basis of Nitrocellulose for All Military Powders For all of the above various kinds of smokeless powder, cotton was initially used and up to the World War continued t o be the accepted source of cellulose for nitrating purposes. This was also true in general of various
VOL.7, NO.8
RELATION OF COTTON TO CHEMISTRY
1839
EARLY POTSYSTEM OF NITRATING COTTON AT CARNEY'S POINT, DU PONT'S N. J. PLANT Old-type boiling tubs.
smokeless powders developed primarily for sporting purposes. It is of interest to note that the Schultze Gunpowder Company of England, which made the first shotgun powder in 1868, continued for over fifty years to nitrate wood cellulose for this purpose. At one time or another the explosives industry, either in this country or abroad, has studied almost every kind of fiber containing cellulose and has prepared nitrocellulose from many of them. Wood cellulose received considerable attention particularly by those nations whose supply of cotton might he cut off in time of war and its use during the war will be discussed later. In the early days of the manufacture of guncotton and smokeless powder in the United States dating back thirty and more years ago, many kinds of cotton and different sources of cellulose were investigated. Long staple cotton, linters, and hull fiber were all studied in turn, the linters being favored because of satisfactory quality, lower initial price, and less pulping required. At one plant cotton clippings from the manufacture of underwear were for a time nitrated and made into smokeless powder. Cornpith cellulose was used in the manufacture of smokeless powder during the early days (1900) of the International Smokeless Powder & Dynamite Company (later the International Smokeless Powder & Chemical Co.), now the Parlin plant of the du Font Company and devoted a t present to the manufacture of lacquers and solvents (11).
1840
JOURNAL OF CHEMICAL EDUCATION
AUGUST,1930
E ~ m POT s SYSTEMO F NITRATING COTTON AT CARNEY'S POINT,DU PONT'S N. J. PLANT Centrifugal wringer for removing spent acid from the nitrated cotton.
Specifications for Purified Cotton for Smokeless Powder The explosives industry has had specifications for more than 20 years covering the quality of purified cotton used in the manufacture of smokeless powder. These specifications are familiar to many of you. During the past year these specifications have been revised, the important changes being as follows: Revised specifications Less than 5% unless lower Less than 7% figure specified in contract Less than 0.8% Less than 0.5% Less than 0.4% Same Nospecification. Viscosity Definite specification on of cotton controlled by each contract manufacturers Former specificelions
Solubility in 10% KOH, or 7.14% NaOH Solution Ash content Ether content Viscosity
Viscosity Control The early years of the manufacture of smokeless powder in this country gave the explosives industry a keen appreciation of the desirability of controlling the viscosity of nitrocellulose used in the manufacture of smokeless powder, especially of powder for military purposes. Nitrocellulose of
HOPEWELL, VIRGINIA,"A" PLANT,FOR THE MANUPACTURE OF GUNCOTTON DURING E. I. du Pout de Nemours & Company.
THE
WORLD WAR
VoL. 7, No. 8
TOP l i I . O O ~
RELATION OF COTTON TO CHEMISTRY
U F i%EC"ANrCAL
1843
D I P P ~ XITRATING R HOUSE SHUWIN
