170 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 



soda or soda lye for use in soap, soda ash or carbonate, for washing 

 or glassmaking, and into chlorine bleaching materials. Chemical 

 works operating these rather complicated chemical processes exist 

 on an immense scale in all civilized countries; it is estimated that 

 $50,000,000 is thus invested in Great Britain alone. The electrolytic 

 alkali industry is barely 20 years old, yet it is already more than 

 holding its own with the older chemical process, and advancing 

 rapidly; 20 years more will probably see the older processes entirely 

 superseded — they are at present fighting for their existence. As 

 for the electrolytic process, the salt is simply dissolved in water 

 and by the action of the current converted into caustic soda at one 

 electrode and chlorine gas at the other. By some special devices 

 these are kept separate and collected by themselves, and the work 

 is done. The principles involved are simplicity itself as compared 

 with the older chemical processes, the only agent consumed is electric 

 energy, and the products are clean and pure. 



Chlorates. — These are salts used on matches and in gunpowder. 

 Chlorate of potassium is a valuable salt with important uses. It is 

 made from common cheap potassium chloride, in solution in water, 

 by simply electrolyzing the solution without trying to separate the 

 products forming at the electrodes. It is a simpler operation than 

 the production of electrolytic alkali. Chlorate thus forms in the 

 warm solution, and is obtained by letting the solution cool and the 

 chlorate crystallize out. The ordinary chemical manufacture of this 

 salt was tedious and dangerous; the electrolytic method has practi- 

 cally entirely superseded it. 



Per chlorates. — These salts have more limited uses, but are made by 

 expensive chemical methods. The electrolysis of a chlorate solution 

 at a low temperature, without separating the products formed at the 

 two electrodes, results in the direct and easy production of perchlo- 

 rates. I cite this more to illustrate what I might call the versatility 

 of the electrochemical methods, rather than because of its commercial 

 importance. 



Metallic sodium,. — The caustic soda produced from salt can itself be 

 electrolytically decomposed; this is the easiest way of producing 

 metallic sodium. Sir Humphry Davy discovered sodium by electro- 

 lyzing melted caustic soda, and at this moment several large works 

 are working his method on an immense scale. The caustic contains 

 sodium, hydrogen, and oxygen, and the current simply liberates the 

 sodium as a molten metal and frees the other two as gases which 

 escape into the air. The process is simplicity itself — when the exact 

 conditions are known and rigidly adhered to. Metallic sodium is a 

 very useful material to the chemist, and the electrolytic method 

 produces it at probably one-fourth the cost of making it in any purely 

 chemical way. 



