Manual wanted for Gilmont closed-end McLeod gage

[Rich Feldman]

I couldn't pass up an opportunity to get a unique McLeod gauge. Mercury and documentation are not included.
Glass configuration is practically identical to these figures from Roger Gilmont's US patent 3,122,923.

Operating procedure can probably be figured out from the patent text. (Google's online version is full of common OCR typography errors.)

Still, I would welcome a look at the original manual if anyone around here has a copy. It probably gives practical details such as how to install the mercury. Also, would anyone care to admit having first-hand experience with distilling mercury?

Thanks.
-RIch

[Dennis P Brown]

I filled a closed end mercury vacuum gauge by taking the glass gauge to above 10^-6 torr and then admitting mercury from a supply that had one side open to atmosphere, thus forcing the Hg into the glass tubing that was under high vac - rather simple and it worked great. AS for distilling Hg, never done that but have distilled organics and it isn't fun. Still, I would guess that the impure Hg distillation would be done in a similar manner (that is, a similar setup of glassware) except one would first place the Hg and chiller/collector under high vacuum. Then heat the Hg allowing it to then condense along a chilled condenser line and fill a container. I would strongly suggest that the holding container & condenser be first cleaned with organics (solvents such as TCE, acetone, and alcohol in that order); also, consider an acid heated (HCl) bath if a high degree of purity is desired - that is, the glassware is acid etched removing many/most metals/inorganic's contaminates in the glass's first few mircons; also a base etch (such as NaOH) would be a good idea to remove all possible organic contaminates (i.e. this is just the standard RCA cleaning process) so the Hg remains ultra clean - of course, the level of purity determines how far one wants to clean glassware - whether one wants 99% pure or 99.99998 purity.

Don't know about your specific Mcleod gauge but most need to be rotated from vertical by 90 degree's to "sample" the current vacuum environment and then rotated back to vertical to read this pressure.