2) Test tubes and test tube holder
3) Methylene Blue indicator
4) Water bath
8) Conc. H2SO4
9) Ferric chloride
10) 2% Sodium Hydroxide
11) 2% Sodium Hypochlorite
12) 5% Phenol
13) Phenolphthalein indicator
1) Detection of microorganism in milk:
Measure out 10ml milk into a test tube and 1 ml of methylene blue indicator is added to it. Mix the contents of the test tube well. A blue color is observed. The test tube is now kept in an incubator at 37oC for 30 minutes. After incubation, if the color changes from blue to white in a short period of time, indicates the presence of larger count of bacteria in the milk.
2) Detection of Table sugar:
Measure out 10ml milk into a test tube and 5ml of Conc.HCl is added to the test tube with milk. The contents in the test tube are mixed well and 0.1g of resorcinol powder is added to the test tube. Mix the contents in the test tube is gently mixed. Now the test tube is placed in a boiling water bath for 5 minutes. the tube in a boiling water bath for 5 min. After the incubation, if a red color is observed, indicates the presence of table sugar.
3) Detection of Starch:
Measure out 3ml milk into a test tube. The test tube is then kept for incubation in boiling water bath for 5 minutes. After incubation, the test tube is then cooled and few drops of 1% iodine solution and mix the contents well. Appearance of blue black color indicates presence starch in milk.
4) Detection of Acids:
Measure out 5ml milk into a test tube. Add few drops of Conc. Sulphuric acid and gently shake the test tube. Add 0.5% ferric chloride solution drop wise into the test tube. Mix the contents well. Development of buff color is indicative of the presence of benzoic acid and if violet color is observed shows the presence of salicylic acid.
5) Detection of Soap:
Measure out 10ml milk into a test tube. Add 10ml of hot water into the test tube containing milk. Now add 1-2 drops of phenolphthalein indicator solution into the test tube. Gently mix the contents of the test tube. Development of pink color on addition of phenolphthalein indicator confirms the presence of soap in milk.
6) Detection of Formalin:
Measure out 2ml milk into a test tube. Gently add 2ml of 90% Sulphuric acid and ferric chloride mixture into the test tube. Formation of purple color ring at the interface of two layers indicates that the milk is adulterated with formalin.
7) Detection of Ammonium sulphate:
Measure out 2ml of milk into the test tube. Add 500ul of 2% sodium hydroxide into the test tube. Mix the contents in the test tube well. Add 500 ul of 2% sodium hypochlorite into the test tube and mix well. Finally add 500ul of 5% phenol into the test tube. Mix the contents thoroughly. A light bluish color will be observed on mixing the contents. Keep the test tubes in a boiling water bath for 20 seconds. Presence of Ammonium sulphate is indicated by the formation of deep blue color in the milk after taking out from the water bath.
Differences Encountered In a Real Laboratory:
In an actual laboratory setting, there are certain important steps that are not necessarily applicable in a virtual lab.
- Always wear lab coat and gloves when you are in the lab. When you enter the lab, switch on the exhaust fan and make sure that all the reagents required for the experiment are available. If it is not available, prepare the reagents using the components shown in the reagent preparation.
- Care should be taken while handling reagents like Conc. Sulphuric acid and hydrochloric acid. These concentrated acids should be opened and used only in a FUMEHOOD. Reagents like 5% phenol and 2% sodium hypochlorite should also be handled with care. Accidental spill of these reagent will cause severe burns and itches. Wash the spilled area with cold water and inform the lab assistant immediately.
- Make sure that the waterbath is set to 100 degree celsius before starting with the experiment.
- The development of colors will depend upon the quality of the reagents prepared.
- Wipe the lab bench after the experiment is completed.
- Make sure to switch off the waterbath and the exhaust fans before leaving the lab.