User:Nadiezda Fernandez-Oropeza/Notebook/Notebook/2010/10/21

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Dilution of Casein

 * This entry shows the difference when trying to dilute casein purchased from two different companies.

Important and related concepts

 * Solubility

“Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a liquid solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on temperature and pressure. The extent of the solubility of a substance in a specific solvent is measured as the saturation concentration where adding more solute does not increase the concentration of the solution.” Solubility


 * Colloidal suspension

Colloids are mixtures whose particles are larger than the size of a molecule but smaller than particles that can be seen with the naked eye. Every colloid consists of two parts: colloidal particles and the dispersing medium. The dispersing medium is the substance in which the colloidal particles are distributed. Colloid

Observations

 * Casein from Bovine Milk, Technical Grade |BRAND_KEY&N4=C7078|SIGMA&N25=0&QS=ON&F=SPEC

We tried diluting 0.2001 g of the compound in 18.5 ml of distilled water. After vortexing the solution we noticed that the compound does not go into solution. The particles are still visible while floating in the liquid and most of the compound precipitates almost immediately after done vortexing.

One might think that adding more and more distilled water might help to the solution process. Unfortunately, it does not. In order to have the compound dilute into the water, one has to change the pH of the solution to a more basic value (NEED REFERECE). In this case, adding one pellet of NaOH did the job.

After vortexing the solution with the NaOH pellet on it, one observes that the caseins starts to dissolve and does not eventually precipitate.


 * Non-fat Dry Milk, Blotting Grade Blocker

We tried diluting 0.2000 g of the compound into 20 ml of distilled water. After vortexing the solution we noticed that a colloidal suspension is formed. This is caused by the large sizes of the proteins in the milk.

Conclusions
The clear difference in solubility and appearance of these two compounds, suggest that they are different indeed. Although a high percent of milk is casein, the other elements on it might make it soluble in distill water.


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