1920.] Parry.—Nitrogenous Manures in New Zealand. 133 
Electro-chemical Methods of Fixing Atmospheric Nitrogen. 
Excluding the Haber, the Hauser, and the Serpek processes, which only 
use electricity in a subsidiary manner, either for firing an explosive mixture 
or else for heating a catalyser, the two principal methods which are 
primarily dependent on electrical energy are the electric-arc method and 
the calcium-carbide method. In the case of the latter, calcium and carbon 
are brought into combination in an electric furnace. The resulting product 
is calcium carbide, for which there is a large market. A part of the 
product is converted into calcium cyanamide- by passing atmospheric 
nitrogen over the heated carbide, which is an economical process, as the 
reaction is exothermic. The calcium cyanamide serves in turn for the 
production of ammonia by passing steam over the cyanamide, whereby 
ammonia is obtained in an exceptionally pure form as compared with by¬ 
product ammonia. The ammonia can in turn be oxidized by the Ostwald 
or similar process into nitric acid, and although this latter process has 
been conducted on a commercial scale it is doubtful whether it is a com¬ 
mercially successful process. A point to be observed is that the primary 
product, calcium carbide, is a marketable commodity and practically com¬ 
mands the market ; also that by a secondary process calcium cyanamide 
is formed, which yields a fertilizer of exceptional value ; nevertheless the 
price of cyanamide is entirely regulated bv the price of Chile nitrate, and 
the whole process is not by any means to be regarded as primarily a 
process for manufacturing a nitrogenous fertilizer. The measure of success 
is due to the fact that several products are obtainable which command 
high prices, and that the fertilizer only serves to regulate production and 
to neutralize the effect of market fluctuations in the price of the staple 
products. A plant for the manufacture of calcium carbide requiring 5,000 
horse-power is in course of erection in North-west Bay, near Hobart, 
Tasmania, which is intended to supply the whole of the Australian market. 
As regards the fixation of atmospheric nitrogen by the electric arc, 
there are three well-known types — namely, the Birkland-Eyde, the 
Schonherr, and the Pauline types. These are operating on a very large 
scale, amounting to about 200,000 horse-power under pre-war conditions, 
to which may be added about 100,000 horse-power erected in Germany 
for the purpose of obtaining material for explosives and to make up for 
the deficiency of Chile nitrates caused by the blockade. These processes 
fix atmospheric nitrogen in the form of nitric oxide under the influence 
of the high temperature of the electric arc, possibly aided by the formation 
of ozone. The nitric oxide is in turn oxidized into peroxide, which in 
turn, on the addition of water, is converted into nitric acid, which latter 
is concentrated by being passed through a series of concentration-towers. 
Apparently it is an economical method of manufacturing pure nitric acid, 
which commands a remunerative price. Moreover, the process is well 
adapted for the formation of sodium nitrite, which is in great demand in 
connection with the aniline-dye industry. These two form staple products 
at remunerative prices. Consequently, if the demand for these and other 
products of a similar character were a steady one there would be no object 
in transforming the nitric acid into a fertilizer, because the nitrate in the 
form of a fertilizer has to compete with a natural product — namely, Chile 
saltpetre. Owing, however, to market fluctuations a certain amount of 
the acid is converted into calcium nitrate by reaction between the nitric 
acid formed in the towers and limestone. It is important to notice in 
this case also that although fertilizers are produced they are a secondary 
