Sintesis dan Karakterisasi Carboxymethyl Cellulose (CMC) dari Selulosa Eceng Gondok (Eichhornia crassipes) dengan Media Reaksi Isopropanol-Ethanol = Synthesis and Characterization of Carboxymethyl Cellulose (CMC) from Water Hyacinth (Eichhornia crassipes) Cellulose Using Isopropanol-Ethanol as Reaction Media