A plant composed of multi-functional apparatus for delivering substances for the treatment of roadways or the land, characterised by comprising a tank divided by a wall into two separate chambers each accessible through a manhole, and which can be connected together by opening valves provided in the wall, one of said chambers comprising agitator means for a liquid and a solute contained in said chamber so as to form a complete solution of the solute in the liquid, motor means being provided for withdrawing and delivering the solution, the second chamber comprising second agitator means for solid material contained in the chamber, and means for withdrawing it and feeding it to distributor means therefor, said second agitator and withdrawal means being extractable from the chamber through an aperture which can be closed by means of a suitable cover;
- the tank being supported by a rigid quadrilateral frame provided with legs which can extend under hydraulic control and are each provided with orthogonal shafts which are inserted into the cross members of the frame in order to define, by the use of locking means, respective horizontal and vertical positions of the legs in which they lie against or are distant from the frame, each shaft having a length greater than one half the length of the cross member into which it is inserted, and a diameter different from the shaft opposite which is also inserted into the cross member, so that one shaft can be inserted into the other when the legs lie against the frame.