Benedicts solution (Qualitative)
qualitative detection of sugar in urine
| Code | Pack Size | Price | |
|---|---|---|---|
| 503M1 | 100ml | £7.19 | Out of Stock |
Benedicts Solution (Qualitative)
SPECIFICATION
- Physical State: Liquid
- Appearance: Clear blue
- Specific Gravity/Density: 1.21
- Solubility in water: Soluble
- Stability: Stable. May crystallise in cold weather.
Benedicts solution is a reagent used to test for the presence of glucose and other reducing sugars. When heated with reducing sugars it is reduced and a red precipitate of cuprous oxide is formed which is insoluble in water. There are separate formulations for qualitative and quantitative analysis.
HOW TO USE QUALITATIVE BENEDICTS REAGENT
Some of the solution to be tested (this could be a juice, blood, or any other liquid) is mixed with Benedict's test reagent (by volume, usually about 2–4 solution to 1 reagent) and heated almost to boiling. A color change from the blue of the reagent to almost any other color – green, yellow, orange, red, brown – is an indication of the presence of what are called “reducing” sugars. For practical purposes, reducing sugars are monosaccharides (simple sugars) like glucose and fructose. It is important to note the most disaccharides (like sucrose, which is the sugar most often used at the table) will not give a positive Benedict's reaction.
For testing for Diabetes by determining the presence of sugar in urine: 5.0ml of Benedict's qualitative solution is mixed with 0.5ml of urine and the mixture is put in a boiling water bath for 5 minutes. The results are recorded thus;
no precipitate – Green a trace yellow + orange ++ red +++
Once sugar is detected in urine, further tests have to be undergone in order to ascertain which sugar is present. Only glucose is indicative of diabetes.
HOW TO MAKE YOUR OWN QUALITATIVE BENEDICTS REAGENT
To make 1000mls:
Heat 800mls of deionised water. Add 173g of sodium citrate and dissolve. Add 100g anhydrous sodium carbonate and dissolve. Separately dissolve 17.3g of copper sulphate pentahydrate in 100mls of water. Add the copper sulphate solution to the first solution. Add deionised water until total volume is 1000mls.
HOW TO MAKE YOUR OWN QUANTITATIVE BENEDICTS REAGENT
In about 600ml of hot water dissolve
200g of sodium citrate
75g sodium carbonate
125g potassium thiocyanate
In about 100ml of water dissolve
18g of copper sulphate.6H2O .
When the solutions have cooled mix them together stirring constantly.Add
5ml of 5% potassium ferrocyanide then make up to 1L.
HOW TO USE QUANTITATIVE BENEDICTS REAGENT
Benedict's quantitative reagent is used to determine how much sugar is present. This solution form as white precipitate rather than a red one and so can be used in a titration.
Accurately measure 25ml of Benedict's qualitative reagent and pour into a 100ml conical flask. Add 6g of anhydrous sodium carbonate, to keep the solution alkaline. Add a few anti bumping granules and bring the solution to a gentle simmer. Pour the sample into a burette and allow the sample to run from the burette into the conical flask until all the blue colour has disappeared. Repeat twice more but this time allow the bulk of the sample to run into the conical flask all at once; then when the end point is near let it drip in one drop at a time, and boil for 30 seconds between each addition. Average the results.
The titration should be repeated with 1% glucose solution instead of the sample in order to calibrate the Benedict's.
The concentration of glucose in the sample can be worked out by comparing the volume needed to discolour the Benedict's with the volume of 1% glucose solution that is needed to discolour the Benedict's.
