Magnetite can be synthesized from several different paths, for
example oxidation of Fe(OH)2 precipitate via green rust [13] or
through the reduction of hematite with hydrogen [14]. However, in
order to obtain nanoparticles, only specific methods have been
proven: iron complexes decomposition [15,16], mechanical alloying
[17], water/oil (w/o) microemulsion [18,19] and the Massart
method [20]. Some of the reported difficulties are the wide particle
size distribution and the large amount of solvent to spend [21]. The
last two methods above are the most frequently employed and
include Fe(II)/Fe(III) fast hydrolysis. In the original preparation
reported by Massart, an aqueous mixture of ferric and ferrous
chloride in hydrochloric acid is added to ammonia solution. The
gelatinous precipitate is then isolated from the solution by
centrifugation or magnetic decantation without washing with
water. The synthesis of magnetite nanoparticles by this way has
the advantages of operation simplicity, the use of economic
reagents and it is still useful to study the influence of solution
conditions in the size of the precipitated particles [22].