Mr. J. Brown on the Products of the Soda Manufacture. 27 



which are usually worked together. They are so contrived 

 that the water which runs into the first pan passes through 

 the whole six in succession. In this way a very saturated 

 solution is obtained. From the last digester the liquor is run 

 into a large iron vessel, where it is allowed to settle : the in- 

 soluble matter which remains in the pans is of no use and is 

 therefore thrown away. It is a source of great annoyance to 

 the manufacturer, as also to the whole neighbourhood of the 

 place where it is deposited, large quantities of sulphuretted 

 hydrogen being evolved from it. Numerous attempts have 

 been made to recover the sulphur from it, but without success. 



Atialysis of Soda Waste. 



The following analysis of fresh soda waste was made in the 

 same way as that of the ball soda. 



1. Sulphuric acid. — The waste was digested in pure mu- 

 riatic acid, and after separating the insoluble matter by filtra- 

 tion, the sulphuric acid was precipitated by chloride of barium, 



BaO, SO3 per cent. CaO, SO3 per cent. 

 7-500 4.-396 



7-108 4-166 



Average 4-281 



2. Sulphur. — The sulphur was oxidized by chlorate of 



potash and muriatic acid, and the sulphuric acid thus formed 

 precipitated by chloride of barium. 



Waste. BaO, SO . BaO, SO3 p. c. Sulphur p. c. 



27-75 gave 27-56 99-315 — 7-304 = 92-011 12-689 



30-90 ... 32-40 104-854 — 7-304 = 97-550 13-455 



26-95 ... 27-80 103-154 — 7-304 = 95-850 13*220 



13-182 



3. Silica and sand. — By dissolving the waste in strong mu- 

 riatic acid, evaporating to dryness, and dissolving the residue, 

 the silica, sand and carbon remained as insoluble matter, the 

 last of which was destroyed by ignition. The silica and sand 

 were then separated by caustic potash. 



Waste. SiO&sand. SiO. Sand. SiOp. c. Sandp.c. 



50-00 gave 5-513 containing 2-640 and 2-873 5-280 5*746 



4. Peroxide of iron. — After separating the silica and sand, 

 the iron was precipitated by caustic ammonia. It contained 

 a very small quantity of alumina. 



