What Are Some Alternative Fixed Temperature Baths for Accurate Calibration Data?

[Physt]

I'm familiar with cooling baths to attain exact temperatures at intervals starting around 13 C and going down from there, but does anyone know of a list of baths that are reasonably safe and effective to attain exact temperatures in a higher range? So far my best idea would be to use liquid and solid parts of Gallium roughly centered around it's 29.7646 C melting point (each part starting ~3-4 degrees off that center point) since it has a heat of fusion of 5.59 kJ·mol−1 it should provide for an accurate fixed temperature bath for a decent amount of time. Does anyone know of some others (with readily obtained materials)? I'd prefer to avoid things like Sodium, Phosphorus and Potassium since they are so reactive.

The purpose of this would be to get calibration data on some individual off the shelf thermistors in the -20 - 105 C range and hit accuracies below 0.1 C (preferably down to the 0.01 C range) as opposed to the typical off the shelf tolerances of 1%.

 

[Doug Huffman]

Depends on the expense you are allowed and the accuracy required. I made a half-dozen custom temperature compensating diodes, for nuclear reactor neutron power indication, that my metrologists calibrated in a water bath.

 

[Quantum Defect]

I'm familiar with cooling baths to attain exact temperatures at intervals starting around 13 C and going down from there, but does anyone know of a list of baths that are reasonably safe and effective to attain exact temperatures in a higher range? So far my best idea would be to use liquid and solid parts of Gallium roughly centered around it's 29.7646 C melting point (each part starting ~3-4 degrees off that center point) since it has a heat of fusion of 5.59 kJ·mol−1 it should provide for an accurate fixed temperature bath for a decent amount of time. Does anyone know of some others (with readily obtained materials)? I'd prefer to avoid things like Sodium, Phosphorus and Potassium since they are so reactive.

The purpose of this would be to get calibration data on some individual off the shelf thermistors in the -20 - 105 C range and hit accuracies below 0.1 C (preferably down to the 0.01 C range) as opposed to the typical off the shelf tolerances of 1%.

Organic solids might have melting points useful to you. The CRC handbook will list melting points of organic solids. Purity is always an issue, with these though. You are in the range where there are a lot of standards.

e.g. http://www.thinksrs.com/downloads/PDFs/ApplicationNotes/MP_Protocols.pdf
http://www.sigmaaldrich.com/analytical-chromatography/analytical-products.html?TablePage=9639990
http://www.al-labor.at/cms/images/stories/docs/Melting%20Point%20%20Standards.pdf