“Chromatography at home” experiment

How to separate mixtures with the help of paper and alcohol

Ev­ery­one knows about dog races, and even cock­roach races. But have you ever seen dyes com­pet­ing for speed? Get some pop­corn and in­vite your friends around – it’s time to place your bets!

Safe­ty pre­cau­tions

Work in a well-ven­ti­lat­ed room and in pro­tec­tive glass­es. Ob­serve safe­ty rules when work­ing with con­cen­trat­ed ethanol.

Warn­ing! Only un­der adults su­per­vi­sion.

Reagents and equip­ment:

  • black and blue mark­ers;
  • 96% ethanol;
  • sheet of thick pa­per;
  • beaker;
  • lid.

Step-by-step in­struc­tions

Take a small sheet of thick pa­per which can fit in a beaker. Make three dots on the pa­per with mark­ers: black, blue, and a mix­ture of col­ors (black + blue). To make the dots on the same lev­el, draw a start­ing line with a pen­cil first. Now low­er the pa­per in the beaker with ethanol, about half a cen­time­ter from the bot­tom. Then seal the beaker, so the ethanol doesn’t evap­o­rate. Af­ter half an hour, ob­serve the move­ment and sep­a­ra­tion of col­ors on the pa­per.

Pro­cess­es de­scrip­tion

Chro­matog­ra­phy is a method for an­a­lyz­ing sub­stances by their sep­a­ra­tion into com­po­nents. The method was dis­cov­ered by Mikhail Tsvet, who sep­a­rat­ed col­or pig­ments of plants. In our ex­per­i­ment, we must se­lect the sol­vent which is con­tained the mark­ers. This is usu­al­ly ethanol.

Due to the cap­il­lary ef­fect, the ethanol soaks the pa­per even­ly, tak­ing the dyes with it. The dyes in the mix­ture re­act dif­fer­ent­ly with the al­co­hol, so they rise at dif­fer­ent speeds.

Sep­a­ra­tion is based on this dif­fer­ence in speed.