SECTION III. 1883. ee | Trans. Roy. Soc. CANADA. 
On the Reduction of Sulphate of Soda by Carbon. 
By THomMas MACFARLANE. 
(Read May 22nd, 1883.) 
This reaction which forms the fundamental process of the soda manufacture is, by 
most authorities, supposed to be correctly described by the following equation :— 
Na, SO, + 2 C= Na, S + 2 Co, 
That the decomposition does not take place in this simple way appears from the fol- 
lowing experiments :— 
1. Anhydrous sulphate of soda and powdered charcoal in the proportions indicated in 
the above formula were melted at a red heat for thirty-five minutes ina hessian crucible and 
then poured out. The product was weighed and dissolved in cold water. It gave a solu- 
tion, greenish colored from dissolved sulphide of iron, which was, however, deposited 
on standing, the solution becoming yellow. This solution gives a voluminous precipitate 
with barium chloride which, after being washed and dried, dissolves to the extent of 41 
per cent. in dilute hydrochloric acid. Effervescence takes place at the same time, the 
evolved gas smelling very slightly of sulphurous acid. This indicated the presence of 
traces of sulphite or hyposulphite of baryta besides sulphate and carbonate. When satu- 
rated with hydrochloric acid, the original yellow solution gives abundance of sulphuretted 
hydrogen, while sulphur is precipitated. The latter phenomenon indicated the presence of 
bisulphide of sodium besides the monosulphide. Calculated from the quantities obtained 
of the various products in this experiment, it appears that 30°33 per cent. of the sulphate 
of soda used remained undecomposed, while the remaining 69°67 parts were converted into 
11:94 parts Carbonate of Soda, 
8°88 parts Sulphide of Sodium, 
28°62 parts Bisulphide of Sodium. 
2. In a second fusion the quantity of charcoal was increased to three atoms as against 
one of sulphate of soda. The product gave the same reactions as in the preceding experi- 
ment, with the following results as regards quantities : 19°58 per cent. of the sulphate of 
soda was left undecomposed. The remaining 80:42 parts yielded 
11:94 parts Carbonate of Soda, 
18:47 parts Sulphide of Sodium, 
23°89 parts Bisulphide of Sodium. 
Here the reduction to sulphide of sodium was still incomplete. Some of the charcoal 
used was not consumed but floated on the surface of the melted product when poured out 
of the crucible. 
