John Dalton (1776-1844) was a Quaker schoolmaster. In 1805 he presented a paper to the Manchester Society in which he reasoned that the solubility of each component of a gaseous mixture was independent of the other components. Appended to this paper was the first table of relative weights or molar masses (M).
Dalton's Law states that the total pressure of a mixture of ideal gases (for example A and B) is the sum of their partial pressures.
The images below show an interpretation of Dalton's Law in terms of the particles of which the gases are composed. The particles may be single atoms or molecules consisting of more than one atom.
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= 
| ptotal = p(A) + p(B) |
The partial pressure of each gas is the pressure that a gas would exert if it alone occupied the volume.
Therefore if both the total pressure and the partial pressure of gas A is known, the partial pressure of gas B can be calculated.
Therefore if both the total pressure and the partial pressure of gas A is known, the partial pressure of gas B can be calculated.
The images below show an interpretation of Dalton's Law in terms of the particles of which the gases are composed. The particles may be single atoms or molecules consisting of more than one atom.
+ =