“Blueberries indicator” experiment

How to make pH indicator from blueberries

You’ve all heard of the in­di­ca­tors phe­nolph­thalein, lit­mus and methyl-or­ange, but un­less you’re a chemist, they’re not easy to ob­tain. But there’s a wor­thy al­ter­na­tive to them – juicy blue­ber­ries! In this ex­per­i­ment you’ll learn how to ex­tract col­or­ing agents from blue­ber­ries, and use them to de­ter­mine the acid­i­ty of so­lu­tions.

Safe­ty pre­cau­tions

Ob­serve safe­ty mea­sures when work­ing with heat­ing de­vices and hot liq­uids.

Reagents and equip­ment:

  • blue­ber­ries (200 g);
  • hot wa­ter (150 ml);
  • 9% ta­ble vine­gar (100 ml);
  • lemon juice (100 ml);
  • fizzy wa­ter (car­bon­ic acid so­lu­tion, 100 ml);
  • wa­ter (100 ml);
  • 2% bak­ing soda so­lu­tion (100 ml);
  • pipe-clean­ing liq­uid (10% sodi­um hy­drox­ide so­lu­tion, 100 ml);
  • spat­u­la;
  • 15 glass­es;
  • glass con­tain­er;
  • pipette;
  • fun­nel;
  • cot­ton wool.

Step-by-step in­struc­tions

In a glass con­tain­er, crush blue­ber­ries and pour hot wa­ter over them. Fil­ter the re­sult­ing mix­ture through a fun­nel with cot­ton wool. Us­ing a pipette, drip sev­er­al drops of fil­trate into the glass­es and grad­u­al­ly fill with the fol­low­ing so­lu­tions: lemon juice, acetic acid, fizzy wa­ter, plain wa­ter, bak­ing soda so­lu­tion and pipe-clean­ing liq­uid. Watch the in­di­ca­tor change col­or from red to yel­low through blue.

Pro­cess­es de­scrip­tion

The po­ten­tial of hy­dro­gen (acid­i­ty) of pH is a mea­sure­ment of the ac­tiv­i­ty of hy­dro­gen so­lu­tions in a so­lu­tion. If pH>7, the medi­um is al­ka­line, if pH<7, it is acidic. If pH=7, the medi­um is neu­tral. House­hold clean­ing agents with a strong acidic or al­ka­line pH may be harm­ful to the body. The in­di­ca­tor does not make a sub­stance less dan­ger­ous and does not pro­vide pro­tec­tion from it – it sim­ply warns of dan­ger.

The ”caus­tic­i­ty” of sub­stances can be de­ter­mine in the home us­ing a blue­ber­ry in­di­ca­tor. Blue­ber­ries con­tain col­or­ing agents – an­tho­cyanins. De­pend­ing on the acid­i­ty of al­ka­lin­i­ty of the medi­um, an­tho­cyanins turn dif­fer­ent col­ors. In a strong acidic medi­um (lemon juice, vine­gar) they turn red, in a weak acidic and neu­tral medi­um they turn pur­ple, in a weak al­ka­line medi­um they turn blue, and in a strong al­ka­line medi­um they turn yel­low.