In this study, we tried to synthesis iron hydroxide suitable for longitudinal magnetic recording media from waste acid, which is a by-product of an iron works factory. Effects of initial pH of reactants, reaction temperature, reaction time for the synthesis of acicular iron hydroxide were studied in relation to particle properties of iron hydroxide and magnetic properties of maghemite powders. As the pH in reactant solution increased, $eta$-FeOOH(pH=4.5), mixture of $eta$-FeOOH and $alpha$-FeOOH(4.5<pH<5.5), mixture of $alpha$-FeOOH and Fe3O4(6.4<pH<12), $alpha$-FeOOH (pH>13) was found to from in order. Especially, $alpha$-FeOOH formed above pH 13 was single phase with superior acicularity. The temperature range over which the single-phase goethite can be formed increased as the initial pH of reactants increased (pH 13:10~5$0^{circ}C$, pH 13.2:10~7$0^{circ}C$, pH 13.5:0~8$0^{circ}C$). The goethite formed between 40~6$0^{circ}C$ has superior characteristics because the acicularity increased with increasing temperature but at high temperature (>6$0^{circ}C$) Fe3O4 (pH=13) was found to start to form. Generally, single phase of goethite was found to form after one hour when an optimized condition. The particle size of goethite did not change as the reaction time increased over one hour. Accordingly, the magnetic properties of ${gamma}$-Fe2O3 produced from goethite were not altered.