cellophane, thin, transparent sheet or tube of regenerated cellulose. Cellophane is used in packaging and as a membrane for dialysis. It is sometimes dyed and can be moisture-proofed by a thin coating of pyroxylin. There are several steps in the preparation of cellophane from raw cellulose. The cellulose is first treated with an alkali, e.g., sodium hydroxide, and mixed with carbon disulfide to form viscose (see viscose process). The viscose is aged for several days and then forced through a straight or circular slit into a dilute acid solution. The dissolved cellulose precipitates, and this regenerated cellulose has a lower molecular weight and a less orderly structure than the cellulose from which it is formed.