From Command and Conquer Wiki

The V2 chem sprayer^[1] was a relatively simple weapon employed by the Brotherhood of Nod in the First Tiberium War, designed for chem troopers, derived from the non-combat sprayer used to spread special Tiberium fertilizer onto the fields by Nod.

Just like it's bais, the weapon was designed to spray Tiberium particulate from a can of pressurized Tiberium waste through a nozzle. The design was extremely simple but also safe, allowing for the use of the weapon even by unshielded personnel. The chemical sprayer was later phased out after Nod's defeat. These weapons were often given to Initiates, due to their tiberium immunity.

[edit] TW3

The Marked of Kane subfaction revived the Chemical sprayer in a more powerful form. Instead of marginaly effective tiberium particulate, the new form sprays corrosive liquid tiberium, which solidifies in enemy transmissions, slowing down the vehicle. It also uses modified back-pack type flamethrowers to project the stream farther.