var t1 = test_tube_svg.selectAll(".test_tube1").transition(t).style("fill-opacity", 1)
        test_tube_svg.selectAll(".test_tube0").transition(t).style("fill-opacity", 0)
        var t2 = test_tube_svg.selectAll(".test_tube2").transition(t).style("fill-opacity", 1)
        t1.transition(t).style("fill-opacity", 0)
        var t3 = test_tube_svg.selectAll(".test_tube3").transition(t).style("fill-opacity", 1)
        t2.transition(t).style("fill-opacity", 0)
        var t4 = test_tube_svg.selectAll(".test_tube4").transition(t).style("fill-opacity", 1)
        t3.transition(t).style("fill-opacity", 0)
        var t5 = test_tube_svg.selectAll(".test_tube5").transition(t).style("fill-opacity", 1)
        t4.transition(t).style("fill-opacity", 0)
        var t6 = test_tube_svg.selectAll(".test_tube6").transition(t).style("fill-opacity", 1)
        t5.transition(t).style("fill-opacity", 0)
        var t7 = test_tube_svg.selectAll(".test_tube7").transition(t).style("fill-opacity", 1)
        t6.transition(t).style("fill-opacity", 0)