Talk:BET theory

Plese clarify on v_m
It's not very clear what is v_m. Is the capacity of absorption of a single monolayer?

Statement removal
This statement is being removed:

the mostly popular principle is V-Sorb 2800 static volumetric nitrogen adsorption principle

The V-Sorb 2800 is a commercial instrument. The neutrality of this statement is disputed.

Agriculturist50 (talk) 20:02, 10 February 2015 (UTC)

equation on page
I am fairly sure the equation on this page is incorrect.

I use a BET surface area measuring instrument and sought to explain it to myself using this equation, but was unable to. Reordering the equation from the Peter Atkins, Julio de Paula Physical Chemistry text (seventh edition, p.992) yielded a different equation, one that matched the information I am receiving from the instrument. The difference is in the first half of the right side of the equation.

It should read:

1/(((Po/P)-1)V) =((c-1)/(cVm))*(P/Po) + 1/(cVm)

I am not fluent in Wikipedia etiquette or code, and will wait a few days before changing anything. Please advise.

T. Nelson

one-point method
Has anyone thought about including the one-point-measuring method on the page? It saves conducting several experiments to determine Va for a single sample. Instead, the following approximation is used: Vm = Va * (1-(p/p0))

This approximation may be used if the constant C is much larger than 1.

Source: European Pharmacopoeia 4th edition, 2002, vol. 1 p.277ff (Monograph # 4.00/2.09.26.00)

Doublespeed 14:32, 2 July 2007 (UTC)


 * i am sure that this equation is wrong. —Preceding unsigned comment added by 59.93.179.201 (talk) 05:42, 7 September 2007 (UTC)

Reported Activated Carbon Surface Area
The value of specific surface area listed in the section about activated carbon (3000 m^2/g) seems much larger than the typical values I am familiar with of 750 - 1500 m^2/g. Is this value correct and typical, or ought it to be revised? --128.101.142.157 (talk) 14:11, 27 April 2010 (UTC)


 * In table 1 in DOI: 10.1016/j.jcis.2004.08.092 specific surface areas of up to 2772 m^2/g are listed, and this was just the first relevant paper I found, so I'd say 3000 m^2/g is pretty OK, although maybe "up to" and a citation should be added. Prostetnik42 (talk) 14:35, 11 September 2014 (UTC)

Equilibrium pressure
The current definition of "P and P0 are the equilibrium and the saturation pressure of adsorbates at the temperature of adsorption,..." seems to be inverse of what it should be, i.e. P - saturation pressure, P0 - eq. pressure. Also, P could be renamed Ps, and both terms should be defined. Adacus12 (talk) 23:22, 12 June 2010 (UTC)

Why would you people have article about a concept and not even bother to define it? You are all retarded jerks!! —Preceding unsigned comment added by 74.105.96.102 (talk) 13:58, 5 October 2010 (UTC)

Stuff about cement is certainly incorrect
Feldman and Sereda showed in the 1970ties that even in the low humidity range the sorption of water is irreversible due to its exchange with the interlayer space. The straight forward application of BET towards cement it, thus, incorrect. May find time to rewrite the section later... - MAE --131.111.65.5 (talk) 13:55, 26 October 2014 (UTC)

Furthermore, the calculation refers to hardened cement paste, and the next comment "However, the article on Portland cement states..." states values for cement (i.e. the powder) rather than the hardened cement paste which is formed by reacting water with cement. Thus, it is irrelevant. --Tomphills (talk) 14:11, 26 September 2016 (UTC)

Improvements 2022
How Reproducible are Surface Areas Calculated from the BET Equation? describes a procedure that "expands on the well-known Rouquerol criteria and makes an unambiguous BET area assignment possible." and addresses some of the issues mentioned in the WP article. - Rod57 (talk) 13:57, 1 June 2022 (UTC)