Mr. Brown on th> ProdmU of the Soda Manvf 



80* 



About cut, of this salt if iokodnoeci into the iron p<.t, A; and 

 upon this is run, by the pipe, 15, about 5i cwt. of sulphuric acid, of 

 about 1-750 specific gra- 

 vity, (150° Twaddell). A 

 violent action immediately 

 plaoe, and large 

 (quantities of muriatic acid 

 gas are evolved, which pass 

 off by the chimney, D. If, 

 however, the muriatic acid 

 can bo made use of, the 

 gas is absorbed either by 

 passing it through water contained in large cylindrical vessels, or through 

 a n»lnnin of coke, which retains the gas until a considerable quantity of 

 it is collected ; a stream of water is then allowed to trickle through the 

 coke, and in this manner all the gas is absorbed. At the expiration of 

 about two hours, the evolution of gas ceases, and the sulphate, which is 

 in a semifluid state, is removed to C, where it is strongly heated, in 

 order to drive off the whole of the acid. The whole operation takes about 

 four hours. 



The foreign matters contained in the sulphate of soda thus obtained 

 are, sand, iron peroxide, magnesia, and undecomposed salt. 



To estimate the sand. This remained as insoluble matter when the 

 sulphate was digested in water containing muriatic acid, and was separ- 

 ated by filtration : — 



1000 grains of sulphate of soda gave, 2'82 grains of sand. 

 _ _ 3.38 — 



1000 



Average, 3*10 — 



From the solution filtered from the sand, the peroxide of iron was pre- 

 cipitated by ammonia ; muriate of ammonia having been previously added, 

 to retain the magnesia in solution : — 



1000 grains of sulphate of soda gave 2-15 grains peroxide of iron. 



1000 — — 2-45 — 



Average, 2*30 — 



After separating the sand and peroxide of iron as mentioned above, the 

 lime was precipitated by oxalic acid and caustic ammonia : — 



Ca O CO, Ca O S0 3 



1000 grains of sulphate of soda gave, 7-100 9*656 



1000 — — 7-367 10019 



1000 — — 7000 9-520 



Average, 9731 



The solution thus freed from lime, \c. was treated with ammonia and 



