Chemistry / [Michael Donovan].

  • Donovan, Michael, -1876
Date:
1834
Catalogue details

Licence: Public Domain Mark

Credit: Chemistry / [Michael Donovan]. Source: Wellcome Collection.

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    to the equivalent numbers of all the bodies known, with but very few exceptions. The singular circumstance, that the first adopted unit* should exactly measure the atoms of all the substances which were afterwards re- duced under the law of multiple ratios, might be ex- plained by supposing that the atom of” hydrogen i is the natural and real unit of all matter ; or, more probably, that fractions have been removed by the corrections made in the analysis of bodies, according to a practice now almost invariably adopted and allowed by chemists. Notwithstanding this coincidence, it has been considered by the majority of good judges, that there are countervail- ing advantages in assuming oxygen as unity, in place of representing it by the number 8. If oxygen be con- sidered 1, we must then reduce the whole scale of equivalent ’ numbers to {th of what they would be were hydrogen 1. Thus, sulphuric acid, which in the table is 40, would then be 5; and nitric acid, instead of being 54, would be 6-75: lime, instead of 28 would be 3°5: carbonic acid, from 22, would change to 2°75 ; and hydrogen would be 0°125. In this case, almost one half of all the ascertained numbers would be fractional ; but they are almost always those fractions which are easily remembered, such as } = 0°25, or 4 = 0°5, or #= 0°75. Dr. Thomson, in advocating the oxygen scale, says, “‘ Surely it will not be said that the frac- tional numbers are more unwieldy or unmanageable than the whole numbers ; while, in all cases of whole numbers, the advantage on the side of the latter method is very great. Thus, if hydrogen be unity, the atom of uranium is 208 ; while, if oxygen be unity, it is only 26.”—(First Princ.i. 17.) On the other hand, Dr. Ure observes, “ It has been objected by some, to our assuming hydrogen as the unit, that the numbers re- presenting the metals would become inconveniently large. But this could never be urged by any one ac- quainted with the theory of numbers. For in what respect is it more convenient to reckon barium 8°75 on * Hydrogen was the unit chosen by Mr, Dalton.