398 



THE AGRICULTURAL NEWS. 



December 12, 1908'. 



ATMOSPHERIC NITROGEN AND THE 



MANUFACTURE OF CALCIUM 



CYANAMIDE. 



Nitrogen is the nio.st impoitant anil costly nian- 

 urial constituent that has to be supplied to the soil in 

 the cultivation of crops, and the increasing need of 

 a supply in large quantity, and in a form suitable for 

 fertilizing purposes, is being generally recognized by 

 asrriculturists. The ever-extending demand for nitro- 

 genous manures, and the fact that available sources 

 jire being depleted, have caused in v'cstigators to give 

 more and more attention to the question of the fixation 

 of nitrogen from the atmosphere, in a suit.ible form, by 

 electrical methods. 



Two such methods, wliich are iiou fuiily well known 

 and have been put into practice on a cunnncicial .scale, are 

 the Frank proce.ss of nianufacturini; calcium cyaiiamide m' 

 lime nitrogen, and the Birkcland-Ey<lc system of producini; 

 calcium nitrate. Notes and shert aitidc^ lelatiiig lidtli to the 

 Erank and the Birkeland-Eydc proce.sses hav^ appeared in 

 past numbers of the jli/rini/tiirn/ i\V»'.< (Vol. IV, ]>. 70 ; 

 Vol. V, pp. 191, 21G, and 3.51 : and Vol. Vli. p. Vii,), but an 

 article cm the subject which appeared in a late niuiiber of 

 Xdfiiit contains a few additicmal particulars. 



In the Hirkeland-Eyde process, ordinary atmospheric air 

 is forced through aii electric furnace under considerable 

 pressure, lender the infltiencu of tlio electric arc, the introgen 

 and oxygen unite chenncally, forming nitric oxide. The 

 fumes are collected, and, after further oxidation, are absorbed 

 in water towers, with the consequent formation of nitric acid, 

 ('alcium nitrate is produce<l when pnwdcrcd (piirkHmc is used 

 for absdrbing the oxide of nitrngcn. 



The Frank process of nianulacturing calcium cyauamide 

 represents the first method adopted on a conunercial scale 

 for producing an artificial niMiiurc containing nitrogen 

 tlerivcd from the air. 



( 'alcium carbide, whicli is so generally used as a genera- 

 tor of acetylene for lighting purposes, forms with atmospheric 

 nitrogen, the basis of the manufacture <if calcinni cyanamide. 

 The calcium carbide, wliich is produced by heating a mixture 

 of chalk and coke in an electrical furnace, is powdered, ami 

 heated to a temperature of fron\ SOO°t". to l.OOO'C. in an 

 enclo.sed vessel, while a current of nitrogen gas is led over it 

 until ('Ombination ceases. The nitrogen which is utili/.eil in 

 this process is obtained by passing a current of air flirough 

 a tube filled with copper turnings. These turnings ab.sorb 

 the oxygen of the air, forming copjier oxide, while the nitro- 

 gen is ietl throngh to the calcium c-arbide. The copper oxide 

 can be readily reduce<l to the metallic state, and used again. 

 The following chemicaltvpiation represents the reaction that 

 takes place between the cahium carbide and the nitrogen 

 gas :— 



VaV., + 2N = t'at'X., -I- V. 



("alcium Nitrogen C.-ilcinni Ciirlmn. 



carl)ide cy.inaniidc 



(The .syinl)ofs Ca, (', and N indicate the clcnicnls I '.dciuni. 

 ('avbou and Nitrogen rfs]iectivcly ; the siii.'dl linnrc li l)y flic 

 (' indicati's that two atoms of carbon condiine with one of 

 calciinn to forni c;diiuni carliide. Similarly, two .-itonis of 

 nitrom'U c\ist in .-i niciln nlc .4' calcinin c'y.in.iniide. ) 



The calcium cyanamide that has been fornu'd is extracted 

 in llie form of a hard cake, and is cooled in vessels from 

 which air is excluded. AVhen cool, it is ground into a fine 

 l)owder, and is ready for Use. 



During the (lasl year a new electric furnace has been 

 flcvi.sed for heating the carbide while it is absorbing the 



nitrogen, and thi^i has proved cheaper, and so .satisfactorj- 

 that all the older retorts have been replaced-'by the electri- 

 cally heated ones. 



Calcium cyanamide decoTnpo.ses rapidly when heated 

 with water under j)ress»re, and slowly with water at ordinary 

 teni])eraturcs, ammonia and calcium carbonate being formed,, 

 according to the equation : — 



CaCX, + :mj) = CaCO.j + iNH.;. 



Calcium Water. C.dciuni Anunoui.a. 



cyanamide. carlionate. 



Probably the decomposition of tlie manure in the soil 

 takes place in part as represented by the aljove equation,, 

 while other reactions also go on. Urea is believed to be one 

 of the early prodncls of decomposition. 



Experiments referrerl to in the A'/ririi/tiini/ Stirs 

 (Vol. V, p. L'H)) have shown that calcinni cyanamide has 

 a fertilizing value but slightly inferior to that of nitrate of 

 soda, and somewhat superior to that of sulphate of ammonia. 

 The cyiinaniidc, as placed on the market, frequently contains 

 a small proportion of free lime. It .should not be mi.xed 

 with su])erphosphate before application to the soil, as the 

 free phosphoric acid of the latter combines with the lime of 

 the cyanamide. It has been pointed out that calcium 

 cyanamide should never be a^iplied to .soil deficient in lime, 

 as unihr such circumstances its action tencs to be distinctly 

 harmful. A dressing of lime should always be given prcviou.sly 

 in such cases. 



The first plant for the production, on an industrial scale, 

 of lime nitrogen was started in Italy nearly three years ago. 

 This factory has .so far turned out 4,000 tons of cyananude 

 i)er year, and the works are now being increa.sed to an annual 

 capacity of 10,000 tons. Works ha\e also been erected in 

 other parts of Italy, as well as in Austria-Hungary, France, 

 Germany, etc. In the United Stat3s the American ('yananiide 

 Company are constructing works on the Canadian side of 

 Niagara Falls, will a capacity of from .').()00 to 0,000 tons 

 per annum. .\ Hiitisli enter]ii-ise is in o]ieration at Odda in 

 Norway. 



In the |iroiluction of calcium cj-anamide an amount of 

 energy equal to about :! iioise-iio\,-er per year is required to 

 tix each ton of nitiogen, including the grinding and other 

 mechanical operations. It may be mentioned that the 

 amount of Chili .saltpetre (nitrate of soda) exported in 1907 

 was 1,740,000 ton.s, ami in order to rejilace this by the 

 fixation of atmospheric nitrogen, it is neces.sary to employ 

 280,000 tons i)f the gas, and this is the amount which, 

 it is calculated, is contained in the atmosphere over every 

 9 acres of the globe. On the basis of the above estimate, jilant 

 developing no less than SOO.OOO luirse-iiowcr would be 

 required to |iroduce calcium cyanamide in quantity sutticient 

 to take the place of all the Chili saltpetre at present 

 consumed each year. 



Beet Sugar Production in Europe. The 



output of beet sugar in l-',nro|ic has shown a steady, 

 if .somewhat small, decline in recent years. The total 

 European .sugar ciop was t;.932.0O0 tons in 190.")-fi, (;,7I0,000 

 tons in 190()-7, and G,r).-)2,000 tons in 1907-S. In 1905-6^ 

 dennuny produced 2,418,000 tons ; the crop fell to 2,239,000 

 Ions in" 190(;-7, and to 2,13.5,000 tons in 1907-8. The 

 Austro-Hungarian beet sugar crop of 1907-8 was 1,440,000- 

 tons, as comparc.d with l,."ilO,000 tons in ,190-5-6. France 

 produced only 72.5,000 tons in 1907-8, as again.st 1,090,000 

 Ions in 190.5 (i. lielginm and Holland show a sinular decline. 

 The Ku.ssiancrop was 9(iS.000 tons in 1905-() ; 1,4 10.000 tons 

 in 1906-7, and 1,410,000 tons in 1907-8 



