A chemical cell with sorption and turbomolecular pumps was attached to an ultrahigh vacuum (UHV) scanning tunneling microscopy (STM) chamber to study the structure of surfaces etched or passivated by various chemicals. This system allows us to study various liquid-solid interfaces with little or no contamination that usually occurs in ambient pressure STM or during transportation of a sample in the air. Silicon surfaces treated by dilute HF, mixed solution of HF with NH4F and KOH were imaged by a UHV STM, revealing different surface structures. This system can be used as a new device for characterization of liquid-solid interfaces.