392 



SCIENTIFIC RECREATIONS. 



spirits, but in ordinary water it is not so greatly soluble, and produces a 

 lather, owing to the lime in the water being present in more or less quantity, 



to make the water more or less " hard." 



SODIUM is not unlike potassium, not 

 only in" appearance, but in its attributes ; 

 it can be obtained from the carbonate, as 

 potassium is obtained from its carbonate. 

 Soda is the oxide of sodium, but the most 

 common and useful compound of sodium is 

 the chloride, or common salt, which is found 

 in mines in England, Poland, and elsewhere. 

 Salt may also be obtained by the evaporation 

 of sea water. Rock salt is got at Salzburg, 

 and the German salt mines and works produce a large quantity. The 



Fig. 398. Machine for cutting soap in bars. 



Fig. 399. Soap-boiling house. 



Carbonate of Soda is manufactured from the chloride of sodium, although 

 it can be procured from the salsoda plants by burning. The chloride of 

 sodium is converted into sulphate, and then ignited with carbonate of lime 

 and charcoal. The soluble carbonate is extracted in warm water, and sold 

 in crystals as soda, or (anhydrous) "soda ash." The large quantity of 

 hydrochloric acid produced in the first part of the process is used in the 

 process of making chloride of lime. A few years back, soda was got from 

 Hungary and various other countries where it exists as a natural efflorescence 

 on the shores of some lakes, also by burning sea-weeds, especially the com- 

 mon bladder wrack (Fucus vesicidosus], the ashes of which were melted into 

 masses, and came to market in various states of purity. The bi-carbonate 

 of soda is obtained by passing carbonic acid gas over the carbonate crystals. 

 Soda does not attract moisture from the air. It is used in washing, in glass 

 manufactories, in dyeing, soap-making, etc. 



