524 PRINCIPLES OF CHEMISTRY 



Of all other industrial processes for manufacturing sodium carbonate, 

 the ammonia process is the most worthy of mention. 16 In this the 

 vapours of ammonia, and then an excess of carbonic anhydride, are 

 directly introduced into a concentrated solution of sodium chloride in 

 order to form the acid ammonium carbonate, NH 4 HCO 3 . Then, by 

 means of the double saline decomposition of this salt, sodium chloride is 

 decomposed, and in virtue of its slight solubility acid sodium carbonate, 

 NaHCO 3 , is precipitated and ammonium chloride, NH 4 C1, is obtained 

 in solution (with a portion of the sodium chloride and acid sodium 

 carbonate). The reaction proceeds in the solution owing to the sparing 

 solubility of the NaHC0 3 according to the equation NaCl + NH 4 HCO 3 

 c= NH 4 C1 + NaHCO 3 . The ammonia is recovered from the solution 

 by heating with lime or magnesia, 16 bis and the precipitated acid sodium 

 carbonate is converted into the normal salt by heating. It is thus 

 obtained in a very pure state. 17 



for the manufacture of sulphuric acid, and ferric oxide which is ogam used in the 

 process. In Grant's method sodium sulphate is transformed into sodium sulphide, and 

 the latter is decomposed by a stream of carbonic anhydride and steam, when hydrogen 

 sulphide is disengaged and sodium carbonate formed. Gossage prepares Na^S from 

 NasSO 4 (by heating it with carbon), dissolves it in water and subjects the solution to the 

 action of an excess of CO 2 in coke towers, thus obtaining H 2 S (a gas which gives SO 2 

 under perfect combustion, or sulphur when incompletely burnt, Chapter XX., Note 6) and 

 bicarbonate of sodium ; Na-jS + 2CO 2 + 2H 2 O = H 2 S + 2HNaCO 3 . The latter gives soda and 

 CO 2 when ignited. This process quite eliminates the formation of soda-waste (see Note 8) 

 and should in my opinion be suitable for the treatment of native Na 2 SO 4 , like that 

 which is found in the Caucasus, all the more since H 2 S gives sulphur as a bye-product. 



Repeated efforts have been made in recent times to obtain soda (and chlorine, see 

 Chapter II., Note 1) from strong solutions of salt (Chapter X., Note 28 bis) by the action 

 of an electric current, but until now these methods have not been worked out sufficiently 

 for practical use, probably partly owing to the complicated apparatus needed, and the 

 fact that the chlorine given ofTat the anode corrodes the electrodes and vessels and has 

 but a limited industrial application. We may mention that according to Hempel (1890) 

 soda in crystals is deposited when an electric current and a stream of carbonic acid gas 

 are passed through a saturated solution of NaCl. 



Sodium carbonate may likewise be obtained from cryolite (Chapter XVII., Note 23) 

 the method of treating this will be mentioned under Aluminium. 



16 This process (Chapter XVII.) was first pointed out by Turck, worked out by 

 Schloesing, and finally applied industrially by Solvay. The first (1883) large soda factories 

 erected in Russia for working this process are on the banks of the Kama at Berezniak, 

 near Ousolia, and belong to Lubimoff. But Russia, which still imports from abroad a 

 large quantity of bleaching powder and exports a large amount of manganese ore, most 

 of all requires works carrying t>n the Leblanc process. In 1890 a factory of this kind was 

 erected by P. K. Oushkoff, on the Kama, near Elagoubi. 



16 bis Mond (see Chapter XI., Note 8 bis) separates the NH 4 C1 from the residual solu- 

 tions by cooling (Chapter X., Note 44) ; ignites the sal-ammoniac and passes the vapour 

 over MgO, and so re-obtains the NHs and forms MgCl : the former goes back for the 

 manufacture of soda, while the latter is employed either for making HC1 or C1 2 . 



17 Commercial soda ash (calcined, anhydrous) is rarely pure ; the crystallised soda is 

 generally purer. In order to purify it further, it is best to boil a concentrated solution of 

 eoda ash until two-thirds of the liquid remain, collect the soda which settles, wash with 



