94 The N.Z. Journal of Science and Technology. [Mar. 
Table 4 : Cost of producing calcium carbide at the rate of 1,000 tons 
per annum. 
Table 5 : Cost of producing carbide at the rate of 1,500 tons per 
annum. 
Table 6 : Cost of production for large outputs from European 
factories. 
Referring to Table 1, this shows the declared value and total imports 
into New Zealand during each year from 1910 to 1917 inclusive, together 
with the quantity discharged yearly at the different New Zealand ports from 
1914 to 1917 inclusive. It will be seen that the whole quantity imported 
in 1914 was 2,956 tons, and that the declared value was on the average 
£14 2s. per ton. The largest quantity imported at any one port was 858 
tons, at Wellington ; and in view of the results of this investigation there 
does not seem to be at the present time sufficient local demand in any one 
centre to justify the establishment of a large calcium-carbide factory on a 
scale sufficient to make the manufacture a profitable undertaking. The 
whole requirements of the Dominion are, however, big enough to enable 
a single factory, and possibly two factories, to manufacture at a profit, 
provided that railage and shipping do not prove to be too much of an 
obstacle. This consideration must be left to those who are versed in such 
matters. 
Referring to Table 2, this shows the chemical reactions, and also the 
standard of quality to be sought in the raw material in order to produce 
a satisfactory product, of which the quality is also shown in the same 
table.. 
The chemical equations call for no comment beyond the fact that they 
only represent the final reaction in its simplest form, without any attempt 
at refinement. 
Regarding the quality of the raw material generally, the following 
summarizes the action of the impurities present in either the coke or the 
limestone, or both. Magnesia is objectionable because it interferes with 
the working of the furnace and tends to cause a deposit in the pipes. 
Alumina also tends to interfere with the working, and promotes the forma¬ 
tion of ammonia in the acetylene. Silica, whilst it facilitates the working of 
the furnace, combines with the iron, which is always present, to form ferro- 
silicon, which interferes with the tapping of the carbide, and is otherwise 
objectionable. The presence of sulphur in excessive quantities forms 
sulphur compounds which pass into the carbide, forming sulphuretted 
hydrogen ; whilst phosphorus gives rise to a haze on burning, and even 
small quantities of the oxide are objectionable. The presence of ash leads 
to difficulties in operating the furnace. 
The following are the limits beyond which, according to Mr. Bingham, 
the authority already quoted, the impurities present in coal and limestone 
will cause either interference with the working of the furnace or will have 
deleterious effect upon the carbide. As regards the coke, the ash should 
not exceed 7 per cent., phosphoric acid 0-04 per cent., sulphur 1-5 per cent., 
iron 0-6 per cent. ; and as regards the limestone, phosphoric acid should not 
exceed 0-01 per cent., silica 1-25 per cent., sulphur a trace, magnesia 0-5 per 
cent. ; with the proviso that if sulphur or phosphorus be low in one a higher 
proportion may be allowed in the other. 
Analyses of typical samples of coke and limestone used in the manu¬ 
facture of the best carbide are given in Table 2. These undoubtedly 
represent material of a very high grade. All the same, it should be borne 
