In this work, a first stage of synthesis to obtain reduced graphene oxide (rGO) using an efficient chemical exfoliation method from graphite was studied. An ammonium hydroxide and a nitric-sulfuric acid mixture were used for in situ oxidation and partial-reduction of graphite. Flakes with a thickness of 3 nm were observed by using AFM, suggesting the presence of ten or less graphene layers. The average C/O atomic percentage ratio obtained was 4.27, which is similar to those results obtained by conventional reduction processes associated with using hydrazine. In addition, a graphitic nitrogen functionalization was observed during the proposed process. Besides that, the precursor of rGO suspension obtained remained stable for six months. Therefore, the present study showed a less aggressive and dangerous chemistry route in order to rGO production than others previously reported works.