I try to use a mantle when I can, however a bath is sometimes needed. When high constant temps ~ 250C - 300C are needed I have used Corning 710R, although quite expensive, it maintains a very constant high temperature bath IMO. As Rhodi points out, watch your ass in the lab with this stuff, we had to pay extra for the professional cleaning crew to come in and de silcone-ize our lab after a few days of reckless usage.
This link
http://www.sas.org/E-Bulletin/2003-04-18/labNotes2/body.html
states that "The safest bath material is
sand since it doesn't present a spatter danger, is non-flammable, is non-toxic, is non-conducting and doesn't degrade. It is a great choice when you have an odd-shaped apparatus and don't want to use a fluid. As an added bonus, you can use a heating mantle as your container (don't try that with liquids!). The drawbacks are that sand is not as versatile and doesn't transfer heat as quickly as fluids."
I think I may have to try using sand in a mantle.
Related:
Post 422858 (missing)
(runne: "What to use as a heating (oil) bath.", Newbee Forum) summarizes above link....
Post 379174 (missing)
(Rhodium: "PEG 400 Oil Bath", Newbee Forum)