salt

electrolysis of brine gives hydrogen, chlorine and NaOH 

cocentrated brine( sodium chloride solution) is electrolysed industrially using a set-up like this : 

the electrodes are made of an inert material - they won't react with electrolyte or the products of the product of the electrolysis 

there are three useful products;

1) hydrogen gas is given off at the (-ve) cathods 

2) chlorine  gas is given off at the (+ve) anode 

3) sodium hydroxide (NaOH) is formed from and ions left in solution