Adsorption cryostats

Figure 3.24. Gas adsorption gravimetry temperature difference between sample and cryostat (at 77 K) as the vacuum around the sample is progressively reduced (after Rouquerol and Davy, 1978).

The nitrogen adsorption - desorption isotherms were obtained with a commercial manometric device (ASAP 2010, Micromeritics) using a point by point procedure of adsorptive introduction. The experiments were obtained at 77 K in a liquid nitrogen cryostat. The adsorptive was obtained from Air Liquide (Alphagaz, purity greater than 99.999 %). 

A second criticism that can be levelled at the use of nitrogen adsorption manometry is the measurement of porosity in the upper mesopore range. Indeed, accurate pressure measurements in the region close to the saturation pressure are difficult and can be influenced by small variations in temperature (e.g. due to a decrease in level of liquid nitrogen in the cryostat). In such cases, the use of a constant level cryostat can be useful. Errors made in this pressure region greatly affect the calculation of pore size as the BJH calculation introduces a log pressure term. 

Reduction of background staining due to nonspecific adsorption by pretreatment with normal serum by hypertonic buffers by addition of detergents (Triton X-100 Tween 20) to buffers by inhibition of endogenous enzyme activity (may be particularly prominent in cryostat sections). 

Also in 1950 a paper was published describing adsorption isobars for hydrogen on nickel films from 20 K to room temperature ( ). These results were achieved with the aid of the newly developed Collins helium cryostat. 

The Cryostat in Industrial Research (1) 274 A Circulating Air-bath Cryostat and Its Use in Dynamic Adsorption (2) 209 A Cryostat for Liquid Nitrogen Cooling of Rocket-bome Photomultiplier Tubes (3) 226... 

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