TECHNICAL CHEMISTRY. 



343 



ture of bleaching powder is the main, that of alkali the 

 subsidiary end. Until therefore we can find a cheap mode 

 of extracting the chlorine from the chloride of calcium this 

 method will hardly be much used, unless indeed Mr. Weldon's 

 proposal for employing magnesia instead of lime and for decom- 

 posing the chloride of magnesium by steam and thus getting 

 hydrochloric acid, turns out to be practically successful. 

 The advantage of the process is, that the product obtained 

 is practically pure, and the soda-ash thus prepared tests up 

 to 5 8 '5 per cent. 



11 I might further enlarge upon two most important branches 

 of the alkali trade, namely, the manufacture of bleaching 

 powder and the manufacture of soap. The description of 

 these is, however, rendered impossible by the limited time 

 at my disposal, and I must conclude by referring you to some 

 statistics of the manufacture. In the first place you have 

 here a synoptical statement of the raw materials, products, 

 and bye-products of an alkali works working 100 tons of 

 pyrites from the estimates of Mr. Mactear. 



100 Pyrites. 



1-88 Nitrate of silver. 



70 Burnt Ore. 

 (Sold to Copper Extracting Co.) 



186-3 Sulphuric Acid. 



I 



160-35 Common Salt. 



176-38 Sulphate of Soda. 



47-45 Manganese Dioxide. 



274 Hydrochloric Acid 



at 1 -16 sp. gr. 

 36-81 Lime. 

 I 



65'45 Bleaching Powder. 



42-75 Recovered Manganese. 



67-02 Coal. 



123-46 Limestone. 



17-63 Lime. 



134-05 Soda ash at 48 per cent, alkali, 

 or 91-63 Caustic Soda at 60 per cent, alkali, 

 or 242'8 Soda crystals. 



Ill -12 waste. 



