144 



NATURE 



[July 29, 1909 



are led under boilers or through a distilling apparatus, 

 and, finall)-, at a temperature of about 50°, into an oxida- 

 tion chamber, where further oxj-gen is taken up, form- 

 ing nitrogen dioxide, which in turn is absorbed by water, 

 and thus converted into nitric acid. 



To facilitate shipment, not a pure calcium product, 

 but a basic nitrate less hygroscopic was obtained. By 

 a new process (German patent 206,949) the nitrous gases 

 are absorbed by calcium cynamide, forming a mixture of 

 nitrate of ammonia and nitrate of calcium. When this 

 .solution is tested with sulphate of ammonia (Norwegian 

 patent 18,029 of Birkeland) calcium sulphate is deposited, 

 leaving a solution of an ammonium product. By testing 

 this again with sulphuric acid, and distilling, nitric acid 

 is given off, and sulphate of ammonia remains. Bv this 

 means, therefore, concentrated nitric acid is also obtained 

 from the nitrous gases. The furnaces, used in the Nor- 

 wegian plants (the first at Notodden) for the production 

 of nitric acid from the air, work with 500 to 700 kilo- 

 watts at a pressure of 5000 volts. The coefficient of re- 

 duction of these furnaces is 07 to 075. 



The method of Schbnherr (Badische .\nilin- und Soda- 

 Fabrik) is said to be much more economical in the use of 

 electric energy. In this process a perpendicular tube is 

 employed having at the lower end an electrode, between 

 which and the walls of the tube or an upper electrode a 

 long arc is maintained. The air rushes whirling through 

 the tube, filling it throughout its length, which may 'be 

 several metres, with a steadily burning arc. There are 

 now three furnaces, each employing "about 600 horse- 

 power, and using an arc about 5 metres long. Single- 

 phase current is used at high pressure. 

 _ Recently Birkeland has lengthened his furnace and con- 

 siderably increased the distance between the electrodes. 

 By means of the magnetic field a long arc is produced 

 which takes the shape of a screw and rotates in the 

 furnace ; by this means the air, which enters in the direc- 

 tion of the arc, is set in violent motion (.American patent 

 906.682, dated December 15, iqoS). 



Mention should also be made of the method of Haber 

 and Konig (French patent 392,670), which may be re- 

 garded as a great step in the development of the pro- 

 cesses just mentioned. Here the mixture of nitrogen and 

 oxygen .s led under a low pressure into the narrow tube 

 in which the flaming arc burns, the tube beino- well 

 cooled on the outside. By this means, it is stated o-aseous 

 niixtures are obtained from the air which contain from 

 9i per cent, to loj per cent, of nitrous oxide, whereas 

 in the older Birkeland-Eyde furnace only i per cent, was 

 obtained. ' 



In a paper read at the recent International Congress 

 of -Applied Chemistry Mr. Bagley directed attention to 

 the production of nitric acid and nitrate of ammonia direct 

 from ammonia gas. .\ plant is working successfully in 

 connection with a battery of coke ovens in Germany 

 .'\mrnonia gas mixed with air is forced rapidly through 

 a plug of platinum. Every seventeen parts by \vei<rht of 

 ammonia produces sixty-three parts by weight of nitric 

 acid of 36 Be. Nitrate of ammonia is also produced 

 by neutralising the nitric acid with a further supply of 

 ammonia obtained from crude gas liauor. By a modifica- 

 tion of the Mond process ammonia is also obtained from 

 ine gasification of peat. 



rMPROVEMEXrS IN PRODICTION AND 



APPLICATION OF GUNCOTTON AND 



NITROGLYCERINE.' 



pOR centuries the only explosive known to the world 



was that mechanical mixture of saltpetre, charcoal, 



and siilphur called gunpowder. Chemical explosives may 



be said_ to date from the discovery of guncotton by 



Schonbein, and it is a fact worth noting on this occasion 



that the first sample of guncotton in "this country was 



one which accompanied a letter of .Schonbein from Basle, 



dated March iS, 1846, and addressed to Michael Faraday 



at the Royal Institution. Schonbein referred to guncotton 



in Jhis letter as follows :— 



" There is another point about which I take the liberty 



1 Biscoiirse delivered at the Royal Institution on Frid.iy, January 20, by 



Sir Frederic L. Nathan, R. A. > V' y 



NO. 2074, ■^'OL. Si] 



to ask your kind advice. I am enabled to prepare in any 

 quantity a matter which, next to gunpowder, must be 

 regarded as the most combustible substance known. So 

 intlammable is that matter that on being brought in con- 

 tact with the slightest spark, it will instantly be set on 

 fire, leaving hardly any trace of ashes, and if the com- 

 bustion be caused within closed vessels a violent explosion 

 takes place. That combustible substance is, as I will 

 confidently tell you, raw cotton, prepared in a simple 

 manner, which I shall describe you hereafter. I must 

 not omit to mention that water has not the least action 

 upon my matter, that is, that it may be immersed ever 

 so long in that fluid without losing its inflammability 

 after having been dried again. A substance of that de- 

 scription seems to be applicable to many purposes of daily 

 life, and I should think that it might advantageously be 

 used as a powerful means of defence and attack. Indeed, 

 the Congreveian rockets can hardly be more combustible 

 than my prepared cotton is. What shall I do with that 

 matter? Shall I offer it to your Government? I have 

 enclosed a little bit of that really frightful body, and you 

 may easily convince yourself of the correctness of my 

 statements regarding its properties." 



In a subsequent letter he gave this body the name of 

 guncotton. 



.Attempts to manufacture guncotton in accordance with 

 the method devised by Schonbein were made both in this 

 country and abroad. .Accidents which occurred, however, 

 both in Great Britain and France in the early days of 

 manufacture, led to the abandonment of attempts to pro- 

 duce it in these countries ; it was only in Austria that 

 its production was persevered with, and a system of manu- 

 facture worked out there by Baron von Lenk. Having 

 succeeded in producing guncotton on the manufacturing 

 scale, von Lenk turned his attention to adapting it for 

 propulsive purposes, and although at one time his efforts 

 appeared to have met with a certain amount of success, 

 and batteries of field artillery in Austria were actually 

 equipped with guncotton cartridges, the difiiculty of 

 moderating its rate of combustion was never satisfactorily 

 overcome. While this question was still the subject of 

 experiments, serious accidents, due to the spontaneous 

 combustion of guncotton in store, led to its production 

 being given up even in .Austria. 



In 1S63 Sir Frederick .Abel took up the study of the 

 manufacture of guncotton in this country with the view 

 of adapting it for propulsive purposes, and, at the same 

 time, of improving its stability, so that its spontaneous 

 combustion in store might be prevented. 



He was not successful in the first object, but, as regards 

 the production of guncotlon of good stability, the modifi- 

 cations that he introduced into the von Lenk system of 

 manufacture resulted in the production of stable gun- 

 cotton. 



The process of manufacture devised by von Lenk was 

 briefly as follows : — 



Skeins of long staple cotton yarn were immersed in a 

 mixture of strong nitric acid of 1-52 sp. gr., one part, 

 and sulphuric acid of 1-84 sp. gr., three parts, contained 

 in iron pans. The skeins were stirred about in the acid 

 bath for a few minutes, removed to a grating above it, 

 and some of the acid squeezed out with a suitable iron 

 tool. The cotton, while still thoroughly wetted with acid, 

 was transferred to earthenware pots, in which it remained 

 for forty-eight hours. The pots stood in cold water to 

 prevent decomposition of their contents. -At the end of 

 two days the conversion of the cotton into guncotton was 

 complete ; the skeins were removed from the pots, and 

 as much as possible of the acid removed in centrifugal 

 wringing machines. After centrifugalling the skeins were 

 drowned as rapidly as possible in a cascade of water, the 

 object being to remove the rest of the free acid. The 

 final purification was effected by immersing the skeins for 

 about three weeks in running water, boiling for a few 

 minutes in an alkaline solution, and finally washing for 

 u few days in flowing water. 



In all that concerned the actual process of nitration Abel 

 followed von Lenk. but instead of using skeins of long 

 staple cotton he introduced the use of cotton waste from 

 the spinning mills, suitably cleaned, and after the free 

 acid had been removed in the preliminary drowning the 



