[synthon]

So, I've sort of just accepted that my method for controlling the temperature for rxns in the range of 50-90 °C is terrible and frustratingly inconsistent.  The problem is that all hot plates in my lab reach 100 °C at the lowest setting, unless a copious amount of oil is heated - and then the oil is not consistently heated throughout.

I've managed to work through this inconvenience by using water baths which seem to require a bit more heating than oil, but the steam is often annoying for reactions which I'd prefer to be dry, approaching all of them.  A post-doc I trained under used to heat the flask directly on the hot plate, but that means fine tuning the temperature of the rxn flask during the rxn, instead of before and can vary wildly if the distance between the plate and flask is changed slightly. I've resorted to trying to hit the sweet spot on the dial, before the lowest setting, but still engaging the heating element and have been able to get temps around 60 °C with ~1L of oil.

But clearly this is all tedious, ridiculous and unnecessary right?  I suppose I need to just order a new hot plate with a wider range of temperatures?  Or maybe I can use a power supply to limit the power to the plate?

[AlphaScent]

Use a heating mantle that is atleast twice the size too big for your vessel.  Then fill in sand around the vessel and use the variak to slowly heat your material.  I do this on a daily basis.  Oil baths and such are much better for distillations.

[synthon]

I've found sand baths maddening for a couple reasons:

1) The range of temperatures achieved seem very dependent on the amount of sand present, meaning that slight variations will cause major disturbances; which
2) makes it difficult to equilibrate the temperature of a sand bath efficiently and consistently; and
3) any knock to the sand bath while adjusting the rxn flask spills sand; and
4) the presence of sand between glassware and hoodtop is worse than fingernails on a chalkboard

The only thing I use sand baths for is temps higher than oil baths are capable, which is practically never.

[orgopete]

Just use a Variac. Temperature control has been done by many companies and in many different ways. One of the reasonably common ways is with a "Thermowatch". If you are short of funds, you may borrow one or get one used on eBay or from someone selling used lab equipment. Just put your thermometer in the oil bath plugged into the thermowatch set to the max temp. When it reaches that temperature, it will cut the heat.

[TheUnassuming]

Good god synthon that sounds tedious.  Get a new stirring hot plate with a thermal controller you actually insert into the oil bath unless you are that tight on funds.  My favorite right now are IKA's, but they are also a bit more spendy.  If you are super tight on funds then borrow a voltage regulator (veriac) and go that route, though if its a stirring hotplate you will also be messing with its ability to stir so using a mantle and being patient is a better call in that case. 

[synthon]

Thanks, new stir plate it is, maybe even two.  I tried a variac and it seemed to work, but it started making noises and I got scared. I'll go back to using that until the new toys get here.