before the ce Institut Egyptiens on 3 May, i8()5, wherein he discussed the 
probable cost of extracting Sodium Nitrate from the shale : 
L.E. MILI,. 
Cost of transport to works per (on of sluile o.5oo 
Washing- per Ion of shale o.o5o 
Total o.55o 
Total cost of 7 tons of shale 3.85o 
Separation of Sodium Mlrate from other salts, per ton of Nitrate o.ioo 
His experiments were made on 60 tons of shale, which furnished 18 tons 
of total salts, of which /i5 0/0 was Sodium Nitrate, equivalent to about 
i3.6 0/0 of the original shale. It should, however, be remarked that in the 
hills near Mualla there appear to be three grades costing respectively 7, i5 
and 38 piastres per cubic metre. The material obtained by Mr. Floyer was of 
the best kind, being purchased as containing 5o 0/0 of soluble salts at 5o 
piastres per ton'^l The three washings gave the following percentages of salt: 
FROM GOOD FROM INFERIOR FROM MEDIUM 
TAFLA. TAFLA. TAFLA. 
ojo ojn 0/0 
So(hum Sulphate 12. 5 16.0 18.9 
Sotlium Chloride 36.8 .38.1 ^O-^ 
Sodium Nitrate 66.1 61.0 /i.').5 
Mr. Hughes caiTied this study further, and by systematic lixiviation in the 
cold, obtained a salt solution which on evaporation yielded a mixture of salts 
with 5/1 0/0 of Sodium Nitrate, lie gives the proportions of injurious salts in 
the Tafia and crude salts per 100 of Nitrate obtained by the above method as 
follows : 
AVERAGE OF TAFLAS. CRUDE SALTS. 
Sodium Chloride i5o 79 
Sodium Sulphate 76 5 
Total injurious Salts 2rj6 8 A 
Mr. Hughes further by evaporating a solution at a temperature of too" C. 
obtained a mixture of salts containing as much as (S8 0/0 of Nitrate of Soda. 
Professor Dunstan (^lov. cit., p. 90) also examined the question from the 
point of view of amount of water required to secure the maximum amount of 
nitrate from the shales. It was found that by percolating water through a 
Judging from the context, the actual amount obtained seems to have been 35 0/0. 
