Experiment 1 - Notes

Experiment 1

I. PURPOSE: To identify the composition of the most abundant elements of protein II. Apparatus: Test Tube, Funnel, Filter Paper, Bunsen Burner, Clay Shield, Dropper, Thong, Mortar and Pestle, Porcelain crucible, Wire gauze III. MATERIALS: Red and Blue Litmus Paper, IV. PROCEDURE AND OBSERVATIONS:

1. Carbon and Hydrogen Place a small amount of casein in a test tube. Heat it gently over a low flame. Observe the two substances formed within the tube. When the experiment is completed, there is a charring of casein in the test tube, indicating the presence of carbon, and the creation of moisture in the test tube, indicating the presence of hydrogen.
2. Nitrogen Mix 1 gram of soda lime and a piece of casein (mongo bean size) in a mortar and mix. Transfer the mixture to a dry test tube and heat slowly and cautiously. Expose a piece of moist red litmus paper to the vapors. What gas turned the moistened litmus paper to blue? The presence of nitrogen is indicated by the presence of ammonia (NH3), which has a urine- like stench.

FUSION: Perform the tests for sulfur and phosphorus on the fused mixture prepared as follows: Place about 2 grams of solid fusion mixture (2 parts Na2CO3: 1 part KNO3) in a porcelain crucible. Add a small amount of powdered casein and mix thoroughly. Heat slowly at the start and the strongly, until a clear mixture is formed. Cool and dissolve with a small amount of warm water and filter. Divide the filtrate into two parts.

3. Sulfur Add dilute HCl to the first portion of the above filtrate until acidic. Heat the solution to boiling and add several drops of 0 N BaCl2 solutions.

Observation: The solution was hazy at first, but as it rested, it progressively grew clearer. In addition, a white precipitate is forming. The presence of sulfur was determined using the fusion technique filtrate and HCl. It required 17 drops of HCl to make it acidic. (Acidic circumstances cause blue litmus paper to turn red.) It was heated to boiling. BaCl2 was then added. The result was a white precipitate. This is BaSO4, also known as barium sulfate. 4. Phosphorus Take a second portion of the filtrate and add concentrated nitric acid drop wise until acidic. Add a few drops of ammonium molybdate solution and heat nearly to boiling. Q1. What is the precipitate formed? Ammonium phosphomolybdate (NH4)3PO4*12MoO3) Q2. Write the equation involved: PO43-+ 3NH4 + 12MoO4 2-+ 24H+ → (NH4)3PO4(MoO3)12 + 12H2O

V. EXPLANATION OF RESULTS

1. Carbon and Hydrogen

In coagulated milk, casein is the main protein. It is an important source of organic matter. Charring is a chemical reaction that occurs when some substances are exposed to intense heat and undergo incomplete combustion. Water vapor and volatile organic chemicals (syngas) are removed from the matrix by heat distillation. As opposed to the lighter-colored ash, the leftover black carbon residue is char. Charring removes hydrogen and oxygen from the solid through the action of heat, resulting in char that is mostly constituted of carbon.

2. Nitrogen

Nitrogen can be detected in casein by combining it with soda lime and heating it. A gas is present inside the test tube while it is being heated. The confirmatory product is NH3, which changes the color of red litmus paper to blue. Because NH3 is basic, the red litmus paper turns blue.

Soda lime is a white or grayish-white granular calcium hydroxide mixed with sodium hydroxide or potassium hydroxide. Soda lime collects carbon dioxide and water vapor and degrades quickly if not stored in airtight containers.

FUSION: Fusion is the process of converting chemicals into ions, which are more readily active when tested. Its function is to convert sulfur to sulfate as well as phosphorus to phosphate.

Heat the casein and fusion mixture in a porcelain crucible until the substance turns black and then white.

3. Sulfur Barium reacts with hydrochloric acid and form a barium chloride: Ba (s) + 2 HCl (aq) → BaCl2 (aq) + H2 (g)

H2SO4 + BaCl2 BaSO4 + 2HCl Barium Chloride interacts with Sulfuric Acid in the presence of H2SO4. [H2SO4] to generate an insoluble white precipitate of BaSO4 is an abbreviation for barium sulphate.

HCl acid has no active function in this reaction. Because both have the same negative radical (Cl-), barium chloride does not react with hydrochloric acid. In HCl, BaSO4 is insoluble. But why is HCl used to precipitate BaSO4 but not H2SO4? Barium salts can react with water to form Ba(OH)2, which is not very soluble and may remove some of the Ba2+ ions prior to precipitation with SO4. To prevent this, HCl can be used to remove any Ba(OH)2 and reverting to BaCl2. An overabundance of Na2SO4 will result in total precipitation of BaSO4. The leftover HCl can be evaporated, however, the H2SO4 cannot.

4. Phosphorus

The presence of phosphorus was determined using the fusion method of filtrate and nitric acid. Nitric acid was added until the solution became acidic. (Blue litmus paper becomes red in acidic conditions.)