• Chemistry 15.05.2013 No Comments

    A few years ago I saw a video about ferrofluid on YouTube. A ferrofluid or magnetic fluid is a stable suspension of magnetite nanoparticles which reacts to magnetic fields in interesting ways. Naturally, I wanted to make some ferrofluid myself.

    There are three easy ways to produce Magnetite (Iron(II,III)-oxide, Fe3O4), at least that I know of. Both are based on the precipitation of an iron salt in an ammonia solution. The first [1] uses Iron(II)-chloride and Iron(III)-chloride as precursors whereas the second[2] uses Iron(II)-sulfate. The third, the one I tried, is explained in this YouTube Video.

    Synthesizing the Precursors

    All three iron precursors are easy to manufacture by dissolving iron wool in hydrochlorid acid and sulfuric acid, respectively.

    Fe+HCl

    Solutions of Iron(III)chloride and Iron(II)chloride

    Solutions of Iron(III)chloride and Iron(II)chloride

    Iron(II)chloride turns to Iron(III)chloride when left in contact with air for some time. The conversion from Iron(II)- to Iron(III)-chloride can be greatly accelerated by adding the oxygen in the form of hydrogenperoxide. The iron wool and the acid is weighed to produce an approximately known concentration of the products.

    Producing the Magnetite

    After the iron has completely dissolved, the solutions are filtered and then then mixed together in a 2:1 ratio of Iron(III)chloride to Iron(II)chloride. This mixtured is then added to a 25% solution of ammonia. The magnetice particles will start to fall out immediately and colour the solution a dark brown or black.

    Preparing the Suspension

    The video instructions said to boil the excess ammonia off and then add oleic acid which should act as a surfactant for the magnetite particles. Unfortunately, this step did not work for me. The particles did not bind to the oleic acid and repeatedly settled on the bottom of the flask when trying to dissolve the resulting black goo in kerosene.

    Perhaps one of the other to methods or using a different surfactant will produce better results in the future.


    [1] : Synthesis and Some Physical Properties of Magnetite(Fe3O4) Nanoparticles (Int. J. Electrochem. Sci.,7 (2012)5734 – 5745)

     

    [2]: Room Temperature Synthesis of Magnetite (Fe3-δO4) Nanoparticles by a Simple Reverse Co-Precipitation Method (IOP Conf. Series: Materials Science and Engineering18(2011) 032020)

     

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  • Chemistry 30.04.2011 No Comments
    Molecular Structure of Umbelliferone

    Molecular Structure of Umbelliferone

    And once again the quest for easily synthesizable fluorescent dyes was successful: Umbelliferone. (Notice the similarity of the molecule to Aesculine. It is just missing the glycosidically bound glucose.)This substance is a naturally occurring dye of the courmarin family, but it can also be manufactured by a simple reaction. Only two reactants are needed, Resorcinol and Malic Acid. Sulfuric Acid is added as a hygroscopic catalyst to produce Formylacetic Acid from the Malic Acid in situ.

    The empirical reaction equation is as follows:

    C4H6O5 + C6H6O2 ————> CO + 3 H2O + C9H6O3

    Resorcinol has a molar mass of  110.10 g/mol, Malic Acid 134.09 g/mol.
    This equates to a 1:0.82 weight ratio.
    I used 1 gram of Malic Acid and 0.82 gram of Resorcinol and added a few drops of Sulfuric Acid. The whole mixture was heated with hot air until both educts were solved in the acid and bubbling started.
    After a short while, the solution began to change color to a dark orange. Upon further heating, the color got darker until it was deep red and had the viscosity of honey.

    Umbelliferon in Water

    Umbelliferon in Water

    A drop of the cooled product was added to a 600ml beaker of cold water and observed under ultraviolet light. Instantly, a bright green plume descending from the surface was visible, changing color to a bright blue while getting more diluted.

    Umbelliferon in Water

    Umbelliferon in Water

    A small concentration in water fluoresces blue under UV light and green in sunlight. In ethanol the concentration shows no influence on the color, as it is always a bright yellowish green.

    Umbelliferon in Ethanol

    Umbelliferon in Ethanol

    EDIT: On a second thought, the green color might come from fluorescein that was formed by a side reaction during synthesis of the umbelliferone. I will try to record absorption and emission spectra to figure out which substances are present.

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