Mr. J. Brown on the Products of the Soda Manufacture. 21 



the carbonate of lime, with the formation of sulphuret of cal- 

 cium and carbonate of soda — 



NaS + CaO, CO^sNaO, COa+CaS. 



But if this compound were digested in water, a reverse 

 action would immediately take place, sulphuret of sodium and 

 carbonate of lime being again formed. To obviate this diffi- 

 culty, a large excess of lime is used in the process, nearl}' 

 twice as much as would otherwise be absolutely necessary. 

 This excess of lime causes the formation of a compound inso- 

 luble in water, the composition of which is SCaS, CaO. This 

 substance has no effect on a solution of carbonate or caustic 

 soda. 



Analy&is of Soda Ball, or Crude Carbonate of Soda. 



An average sample was obtained by pounding a large quan- 

 tity of the soda ball, and from this the specimens analysed 

 were taken. 



1. To estimate the amount of soluble and insoluble salts. — 

 A portion of the substance was thrown on a weighed filter and 

 washed with water at about 120° F., until a portion of the 

 filtered liquor left no residue on evaporation ; the filter and 

 insoluble matter were then dried in a water-bath and weighed. 



Soda ball. Insoluble matter. Soluble matter. 



100 gave . . 59-87 4.0-13 



58-92 41-08 



' ... 59-90 40-10 



Average 59*56 40-43 



2. Sulphate of soda. — After saturating the soda ball with 

 pure muriatic acid, and separating the insoluble matter by 

 filtration, the sulphuric acid was precipitated by chloride of 

 barium. 



Soda ball. BaO, SO3. BaO, SO3 per cent. NaO, SO3 per cent. 



245-20 gave 8*50 3*466 2-147 



110-00 ... 1-30 1-181 0-733 



78*36 ... 0*76 0*969 0*601 



Average 1*872 1*160 



3. Chloride of sodium. — The soda ball was digested with 

 nitric acid and filtered, and from the filtered solution the chlo- 

 rine was precipitated by nitrate of silver. 



Soda ball. AgCI. CI. Na CI. Na CI percent 



98 gave 5*400 1-350 2*250 2*295 



100 ... 3-679 0-912 1-532 1*532 



Average 1*913 



