Benedict's solution tests for aldehyde which is present in reducing sugars. If the solution remained blue than no reducing sugar's are present in corn oil.
To test for protein. Biuret or solutions of sodium hydroxide and copper sulfate. Tested with a dropper a + result will be purple or something
Both cows milk and water-buffalo's milk produce a violet colour when tested with biuret solution because they both contain protein.
When being tested with biuret reagent, protein turns a blue to lilac color. However, starches when tested do change to a blackish blue color.
That the unknown sample is not a monosaccharide and is does not contain peptide bonds (is not a protein). This is because they both produced negative results because Biuret tests positive in solutions that contain peptide bonds and will turn a violet color. Benedict reagent reacts to monosaccharides and will turn green-reddish orange when a monosaccharide is present. Neither of these things happened so the results are negative.
Proteins are made of peptide bonds which is the target of reaction for biuret test. It's not truly specific for proteins; biuret itself also gives a positive result (hence the name of the test). However, proteins are fairly common and biuret (and similar peptide-containing compounds) are relatively rare.
A reference solution was used in order to see what reaction happens between a test reagent and a solution with a high value of the ions being tested. A blank was used to show that there is no reaction when the ion being tested for is not present in the solution.
Sugar in blood and urine is tested with Benedict's solution.
Iodine-KI reagent. Add to the substance being tested directly. Result: If positive, Turns Blue/Black If negative, (absence of starch) Solution remains orange/yellow.
How to test for protein - The Biuret test1. Add Sodium hydroxide to a 1% solution of albumen (the protein in egg white) or the ground food you want to be tested for protein2. Then add 1% copper sulphate solution3. If protein is present the solution will go purple
positive result for when buiret is added to protein is blue or violet/pale lilac colour. (not pink). positive result for when iodine is added to starch is blue or black colour (not pink).
BaSO4 is insolubel AND it contains sulfate, the ion of which the absence or existance should be tested for. (This doesn't sound quite logic)
1) Add 2cm3 of solution to be tested to a test-tube. 2) Add an equal volume of 5% potassium hydroxide* solution and mix. 3) Add 2 drops of 1% copper sulphate solution and mix. A mauve or purple colour develops if protein is present. *Sodium hydroxide solution can be used instead of potassium hydroxide solution.