V. MANUFAOTUBES. 651 



2459. Spence's Process for the Manufacture of Alum. 



Specimens to illustrate the process, consisting of : 



(1.) Shale of the coal measures before calcination (source of 



alumina). 



(la.) Shale after calcination. 

 (2.) Pyrites or bi-sulphide of iron (source of sulphur for the 



manufacture of sulphuric acid). 



(2a.) Nitrate of soda, for oxidising the sulphurous acid pro- 

 duced from the pyrites into sulphuric acid. 

 (26.) Sulphuric acid, specific gravity 1'6, as used in the manu- 

 facture of alum. 



(3.) Gas liquor (source of ammonia). 

 (3#.) Sulphate of ammonia. 

 Sulphate of alumina. 

 First crystals of ammonia alum (a double salt or compound 



of sulphate of ammonia and sulphate of alumina). 

 (6.) Ammonia alum. Second and final crystallisation. 



Peter Spence. 



2473. Specimens of Alum Crystals. 



3 Crystals of potash-alum. 



3 >J 



10 



4 Crystals of chrome-alum. 



2 ,, ,, covered with potash-alum. 



1 Crystal of potash-alum of o kilo. 

 1 31 kilo. 



H. B. J. van Rijn, Venlo, Netherlands. 



2679. Chlorate of Potash. Muriate of potash containing about 

 90 per cent, chloride of potassium, and some impurities consisting 

 of chloride of sodium, sulphates of potash, soda, lime, and magnesia. 



James Muspratt fy Sons. 



2680. Chlorate of Potash. Milk of lime of about 1-08 

 specific gravity, made by well stirring up about 18 ctr. slacked 

 lime in about 6,800 litres water in a cast-iron vessel. The sample 

 contains a small quantity of chlorate and of chloride of calcium 

 from the previous solution made in the same vessel. 



James Muspratt $ Sons. 



2681. Chlorate of Potash. Solution of chlorate of lime of 

 about 1*15 specific gravity, containing at the same time chloride 

 of calcium in the molecular proportion of about 1 5. Obtained 

 by saturating milk of lime with chlorine gas. Towards the end 

 of the process the temperature rises, when permanganate of lime 

 is formed owing to the small quantity of manganese contained in 



