# What are the volumetric thermal expansion coefficients for butyl acrylate and methyl methacrylate monomers?

We have some tanks of butyl acrylate and methyl methacrylate monomers, and the level indicators are giving incorrect readings. The control systems engineer who set up that system suspects that the density values used in programming the level indicators were wrong, so I measured the density of the monomers by hand today. However, the monomer samples I had were at around 70-72 Fahrenheit, whereas the tanks are usually closer to 52 Fahrenheit. I'm trying to find the volumetric thermal expansion coefficients for these liquids so I can correct my measurements, but I'm unable to find them. I've checked online and in the CRC Handbook of Chemistry and Physics (which lists coefficients for some organics, but not these).

I know that the expansion coefficients are temperature dependent, but if I can get even a single value (at, say, 20 Celsius, which seems to be a fairly standard place to measure this for organics) I should be able to get my estimate close enough to be able to judge if this is the source of error in the level indicators or not.

• At what temperature did you measure the density? The CRC Handbook gives a density of 0.8936 at 68F for butyl methacrylate. Over such a small temperature range like this you could just extrapolate/interpolate the density based on 2 values, so long as they are at least several degrees or so apart. For example, the density of methyl methacrylate is 0.945 at 68F, and 0.934 at 77F. If we just did a linear extrapolation to 53F, we would calculate a density at that temperature of 0.965. Extrapolation can get you in trouble though. Do you have a density measurement at a lower temperature? – airhuff Feb 19 '17 at 22:13
• I should have measured density at a lower temperature, yeah. It would have been easy enough to measure the density in a cool water bath or something (or heck, just using the literature values for the density at a different temperature) and interpolate in that range to get a rough estimate. These were early days in my career though, so my first instinct was to use one of the things I learned in school and I ended up over-complicating it. I can't remember now how this issue ended up getting solved. – realityChemist Jul 25 '18 at 19:10