ph paper

[amit]

how to make ph paper from common kitchen vegitables. actually i read some where that they can be made from onion peel. how that can be?

[John Cuthber]

I doubt that you can make vegetable dyes into the same sort of indicator paper that is made commercially. However you can use a number of comonly available materials to indicate acidity and alkalinity. Lots of berry like fruits have juices that change colour with pH. Grapes and blackberries work quite well. So does red cabbage. If I remember rightly onion skins go green in alkaline conditions. Turmeric contains curcumin which goes from yellowish to red when you add alkali.

I think the best advice I can give is to try things.

[hermanntrude]

it's very easy to make a pH indicator with various vegetables. I've never heard of the onion peel one... perhaps the red onions would work. The one that is most commonly used is red cabbage. Many coloured substances in vegetables are sensitive to pH changes. I'm not really sure how you'd make the papers... perhaps just soak the papers in a solution of whatever it is you've extracted.

 

here are a couple of links:

 

LINK

 

LINK

[frosch45]

I came across this a few months ago, its not just pH paper, but also useful indicators for other substances.

 

Test papers

From "The Household Cyclopedia" (1881):

http://www.publicbookshelf.com/public_html/The_Household_

Cyclopedia_of_General_Information/phtestpa_bjd.html

 

Distilled water only should be used in these preparations. In preparing the papers the liquid should be placed in an earthenware plate or dish, and the paper carefully immersed in it so as to be uniformly wetted then dried out of the reach of acid, ammoniacal, or other vapors likely to affect it; and afterwards kept in bottles, jars, or cases.

 

 

Cabbage Paper

Make a strong infusion of red cabbage leaves, strain it, and evaporate it by a gentle heat till considerably reduced. Then dip the paper in it and dry it in the air. [This paper is of a grayish color; alkalies change it to green, acids to red. It is a very delicate test; if rendered slightly green by an alkali, carbonic acid will restore the color.]

 

 

Full Red , pH = 2

 

Red-violet , pH = 4

 

Full violet , pH = 6

 

Blue-violet, 7 (neutral)

 

Full blue , pH = 7.5

 

Green-blue , pH = 9

 

Blue-green , pH = 10

 

Full Green , pH = 12

 

 

Dahlia Paper

From the petals of violet-dahlias, as cabbage paper.

 

Elderberry Paper

This is merely paper stained with the juice of the berries. Its blue color is changed to red by acids, and to green by alkalies.

 

Indigo Paper

Immerse paper in sulphate of indigo, wash it with water rendered slightly alkaline, then with pure water, and dry it in the air.

 

Iodide of Potassium and Starch Paper

Mix starch paste with solution of iodide of potassium, and moisten bibulous paper with it. [it becomes blue when exposed to ozone. Chlorine has the same effect.]

 

Lead Paper

Paper dipped in a solution of acetate of lead. [When moistened it detects sulphuretted hydrogen, which renders it black.

 

Blue Litmus Paper

Bruise 1 oz. of litmus in a mortar, and add boiling water; triturate together, put them in a flask and add boiling water to make up to half a pint; when cool strain it, and dip paper in it. More color may be extracted from the litmus by hot water, but the liquid will require to be concentrated by evaporation. [Acids change the color to red, but it does not become green with alkalies.]

 

Red Litmus Paper

As the last, adding to the strained infusion few drops of nitric acid, or of pure acetic acid.

 

Rose Paper

Make a strong infusion of the petals of the red rose, and dip unsized paper in it. [Dipped in an alkaline solution so weak as not to affect turmeric paper, it assumes a bright green color.]

 

Manganese Paper

Dip paper in a solution of sulphate of manganese. [it becomes black in an ozonized atmosphere.]

 

Rhubarb Paper

Dip paper in a strong infusion of rhubarb, and dry it. [Alkalies render it brown. It is not, like turmeric paper, affected by boracic acid.]

 

Starch Paper

This is merely paper imbued with starch paste. Cotton cord is sometimes used instead of paper. [As a test for iodine, which turns it blue.]

 

Turmeric Paper

Boil 1 oz. of coarsely powdered turmeric-root in 1/2 a pint of water for 1/2 an hour, and strain; dip paper in the liquid and dry it. [it is rendered brown by alkalies, and also by boracic acid and borates.]

[amit]

thanks a lot u guys. my problem is solved