The ornamental design for a reactiontube, as shown and described.
FIG. 1 is a front, top and left side perspective view of a reaction tube showing our new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a left side elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a rear elevational view thereof;
FIG. 8 is a cross sectional view taken along line 8-8 in FIG. 2 thereof; and,
FIG. 9 is an enlarged view of area 9 indicated in FIG. 3 thereof.
The broken lines in the drawings are for the purpose of illustrating the boundaries of the portions shown enlarged in the views and form no part of the claimed design.