48 THOMAS MACFARLANE: REDUCTION OF SULPHATE, Ere. 
3. Even with four atoms of carbon and at a bright red heat the reduction was im- 
perfect. Unconsumed charcoal floated on the fused product, and the latter was found to 
contain sulphate and carbonate besides the sulphides. 
4. The experiment with three atoms carbon repeated at a high temperature in a clay 
crucible gave the following results: 15°38 per cent. of the sulphate remained undecom- 
posed. The remaining 8462 parts yielded 
8°76 parts Carbonate of Soda, 
28°28 parts Sulphide of Sodium, 
16°34 parts Bisulphide of Sodium. 
From these experiments it seems that the product obtained on fusing sulphate of soda 
with charcoal is not a pure sulphide but almost invariably a mixture of sulphides with 
carbonate and undecomposed sulphate. 
5. When the ignition is made in a plumbago crucible perfect fusion does not take 
place. The mass becomes soft and a part seems to sweat out of it, attacking and destroy- 
ing the crucible. The remainder, when ignited at a much higher temperature than re- 
quired for the fusion in clay crucibles, becomes quite soft but does not fuse. 
It, therefore, seems plain that the preparation of sulphide of sodium uncontaminated 
with sulphate or carbonate is a matter of considerable difficulty, and that the processes for 
manufacturing carbonate of soda or soda ash, which are based upon the decomposition of 
solution of sulphide of sodium by various agents are not likely to prove successful. 
