He next assures himself that the strength or weakness of his dilute acid does not interfere with this law.

Sending the same current through a series of cells containing mixtures of sulphuric acid and water of different strengths, he finds, however the proportion of acid to water might vary, the same amount of gas to be collected in all the cells.
A crowd of facts of this character forced upon Faraday's mind the conclusion that the amount of electro-chemical decomposition depends, not upon the size of the electrodes, not upon the intensity of the current, not upon the strength of the solution, but solely upon the quantity of electricity which passes through the cell.

The quantity of electricity he concludes is proportional to the amount of chemical action.

On this law Faraday based the construction of his celebrated Voltameter, or Measure of Voltaic electricity.
But before he can apply this measure he must clear his ground of numerous possible sources of error.

The decomposition of his acidulated water is certainly a direct result of the current; but as the varied and important researches of MM.