1918.] The N.Z. Journal of Science and Technology. 
25 
merit of the same industry will yield an iron-oxide paint previously imported. 
Other scientific developments are in hand, which will produce in the near- 
future commercial results of the utmost importance in making a self- 
reliant community of New Zealand. 
Caustic soda cost £12 per ton before the war. It is now costing £45 
per ton, and will probably shortly be unprocurable. Arrangements are 
being completed for the local manufacture of caustic soda and hydro¬ 
chloric acid by the electrolysis of common salt by means of Lake Coleridge 
power. 
This again draws attention to the necessity of developing the produc¬ 
tion of common salt in New Zealand. The imports of common salt for the 
past five years have averaged 24,000 tons per year, worth about £72,000. 
Of this a substantial portion used to come from Germany. That it is 
possible to produce salt by evaporation of sea-water is demonstrated by 
the success of the venture at Geelong, Victoria, where 20,000 to 30,000 
tons per year have been produced for some years past at a very low cost. 
The sea-water of Cook Strait contains 3-33 per cent, of sodium chloride— 
that is, 40 tons per acre-foot. It would thus require the evaporation of only 
600 acre-feet per year to supply the whole of the Dominion’s requirements, 
and in this hydro-electric power will take an essential part. 
But in addition to 24,000 tons of common salt we import over 5,000 
tons per annum of other salts of sodium, worth before the war over £100,000 
per annum. The development of the salt and caustic-soda industry is 
the first step in the production of the whole of these more valuable sodium 
salts. 
Another direction in which hydro-electric power will take an essential 
part is in the manufacture of calcium carbide, and thence calcium cyanamide 
or nitrolim—a most valuable nitrogenous fertilizer—and thence ammonia 
and all the important group of nitrogenous products, including explosives. 
The imports of carbide alone exceed 2,400 tons, worth before the war 
over £32,000 per annum. Owing to high freights there is a natural pro¬ 
tection that will render the manufacture of carbide a very remunerative 
business, in addition to the possibility of converting it into nitrogenous 
manure, &c., with compressed oxygen as a valuable product. 
Already preliminary work is being done on the direct electrolysis of 
water on the large scale, to yield oxygen for acetylene welding and 
hydrogen for the hardening of fats. 
Electric Steel-smelting. 
Another industry in which Germany has made special advance is the 
electric smelting of steel, and in this hydro-electric power promises to 
give us in New Zealand an opportunity of which full advantage must be 
taken. The ordinary 1-ton to 2-ton electric steel-furnace requires 500 to 
1,000 kilowatts, and the Lake Coleridge plant will thus be large enough 
ultimately to supply several such furnaces. Already definite proposals 
are in hand. In Australia it is found profitable to smelt steel by means 
of the electric furnace even with electricity generated from steam at a cost 
of |d. per unit. The product is of such high grade that it is used largely 
for purposes for which brass and gun-metal were previously required. 
This opens up an enormous field of utility, limited only by the amount 
of raw material procurable. Such furnaces can be conveniently operated at 
night, the moulding being done in daylight. This makes it possible to 
supply the power for them at a very cheap rate-—less than one-third the 
