836 Transactions of the American Institute. 



maxufactuke of carbonate and bicarbonate of soda. 



For this purpose 1 eq. of crj'olite and 6 eq. of limestone, both 

 finely pulverized, are mixed intimately together, and exposed to 

 the bright red heat of a reverberatory furnace. The process then 

 going on may be expressed by the following formula: 3 Na Fl-f- 

 AI2 Fl,+6 Ca O, C0,=6 Ca Fl+3 (Na O, \ Al, 0.3)4-6 CO2; the 

 carbonic acid evolved being gathered in a gas holder. The result- 

 ing salt-cake is racked out, placed in proper vessels and treated 

 'w ith water, in the same way as is done in the preparation of soda- 

 ash. A lye is thereby obtained of aluminate of soda, and a residue 

 of fluoride of calcium. The lye is then drawn off into a cistern and 

 carbonic acid gas conducted into it. 



The latter in combining with the soda, forms the carbonate of 

 soda, which remains in the liquid, while hydrate of alumina is pre- 

 cipitated. In evaporating the liquid, the soda of commerce may 

 be obtained; the abovementioned company, however, is now con- 

 verting it almost wholly into the bi carbonate, by simply passing 

 a larger amount of carbonic acid gjxs into the same. 



MANUFACTURE OF CAUSTIC SODA. 



To this end, after having been finely ground, one eq. of cryolite 

 and six eq. of slacked lime, or equal parts of both, are intimately 

 mixed together. The mixture is then exposed to heat, the resulting 

 mass treated with water, and the lye thus obtained, allowed to boil 

 Avith a surplus of cryolite. Fluoride of sodium and hydrate of 

 alumina are thus formed, as is shown by the following equation: 

 3 (Na O, \ AI2 0,)+(3 Na Fl+Ala Fl3)=6 Na Fl-f 2 (Al, O3). 



The lye of fluoride of sodium is drawn off from the insoluble 

 alumina and boiled with caustic lime. Fluoride of calcium and 

 caustic soda are thereby obtained. The latter having been decanted 

 from the former, and submitted to evaporation, constitutes the con- 

 centrated lye of commerce. 



It is very desirable that the lime employed be free from oxide 

 of iron, in order that pure sulphate of alumina may be obtained, as 

 the smallest percentage of that oxide diminishes the brilliancy of 

 the colors formed by the alumina compound. 



ALUMINATE OF SODA. 



This compound is sold by the Pennsylvania Salt Manufacturing 

 Company, in a concentrated state, under the denomination "Natrona 

 Refined Saponifier," for the making of soap. It forms, further, an 

 excellent mordant for imparting aniline red and violet colors to 



