indicator paper for determination of nitrate content in fruits and vegetables. To date, two methods are known for determining nitrates and nitrites. The first is considered strictly specific. It is based on the diazocomposition reaction, but it uses rather rare and, moreover, very carcinogenic substances (there is a high probability of cancer). The second - is considered not specific, but in the case of food analysis - strict specificity is guaranteed! The method is well known to most from school, only we were not taught to use knowledge ... It is called - "iodine starch reaction"
To make indicator paper you will need:
-strips of filtering white paper.
liter liter saucepan.
- shallow bowl
-necessary and sufficient number of clothespins.
half a liter of water
-starch (any, you can even "fruit and berry jelly")
potassium iodide (in a pharmacy - 200 ml of a 3% solution - eye drops)
Getting down. In a saucepan, bring to a boil 0.5 l of water and a thin stream with stirring, pour in a suspension of starch. Boil another five minutes. When the liquid brightens, we stop heating. Dissolve 1-3 g of potassium iodide in a hot liquid or just pour a bottle of eye drops with stirring. After the liquid cools with it, we impregnate the paper. If the saucepan is not deep, you can do without a bowl. Remove the excess solution from the impregnated strip with a subsequent strip. Dry using a clothespin. The indicated amount of reagent is quite enough for the manufacture of hundreds of strips of 250 * 100 mm.
Paper in the absence of light has been stored for decades without changing its properties, but if it is still darkened, you should not despair. It can go bad for a banal reason: pipes with cold water leak, and the water is chlorinated. In this case, you must invite the dignity. technique, eliminate the malfunction, and treat the indicator paper with gaseous sulfur dioxide. In a few seconds, the display will return.
In conclusion, and for the sake of completeness, I will give some more information. Type "World" where they draw, find all the shades of blue.
So (with a 10% margin of error):
BLACK - nitrate concentration is higher than 1000 mg / kg of product.
it is very dangerous (unfortunately I watched this) - severe poisoning is guaranteed
BLACK-BLUE - 1000 mg / kg - severe poisoning.
BLUE 750 mg / kg --........
LIGHT BLUE - 500 mg / kg - nausea, chills ... ("hangover")
COLOR - 250 mg / kg - malaise, weakness.
BLUE - 100 mg / kg - valid
SV. BLUE - 50 mg / kg - safe.
WHITE missing - ideal.
Perhaps this is all. The method is not ideal (there are also spots on the Sun) colored juices will have to be compared with a control (simple) piece of paper.
All good health and bon appetit!