[3dem] Ethane - propane mix

[Bob Grassucci]

On 5/1/2012 4:02 PM, William Rice wrote:
> Dear all,
>
> Have many of you had experience using a mix of 37% ethane / 63% 
> propane as a cryogen? It has the advantage that it stays liquid at 
> liquid nitrogen temperature. We had thought it would be easier to 
> handle, but we found that it seems to leave a thin layer of liquid 
> cryogen on the surface of the grid. Putting a freshly frozen grid into 
> the microscope seemed to cause problems with the IGP as this liquid 
> seemed to evaporate only in the high vacuum of the microscope. Solid 
> ethane frozen on the grid usually cracks and breaks off or sublimes in 
> the airlock during pumping before insertion. Has anyone else seen this 
> effect?
>
> Thanks,
> Bill
>
Hi Bill,
We saw the oil slick on our mixture as well but did not see the vacuum 
problem.  We did notice a great deal of high contrast dark blobs all 
over the grid we generally attribute to contaminants on the bottom of 
the ethane tank.  We were using a high purity ethane and a high purity 
propane but still got this effect.  We decided just to stick with the 
ethane.
Bob

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