is approximately 3 5 inches wide at its widest part and extends approximately 2 inches along the upwardly inclined lowermost portion thereof stiffening bead 20 can be roughly semicylindrical with a diameter of about 1 inch cover slat 50 can be about 3 5 inches at its widest and 1 5 inches at its narrowest front to back dimensions first and second orifices 38 and 68 can both be circular with a diameter of about 1 inch first and second stoppers 40 and 72 can be size 5 rubber stoppers of the type ordinarily used in chemical laboratory work the inwardly projecting ledges in first set of ledges 32 and second set of ledges 34 can have an inwardly projection dimension of about 0 25 inch and lateral dimension of about 1 inch first removable platform 76 is conveniently made of a stiff plastic material 3 16 inch thick and have dimensions 6 875 by 14 inches with a central through hole that is circular with a diameter of 0 75 inch second removable platform 36 is similar but with dimensions 7 25 by 14 inches so as to rest on second set of inwardly projecting ledges 34 first and second rack portions 60 and 62 can have a front to back extent of about.