Unformatted text preview: w known to be
compounds, not elements (e.g., lime,
soda, and potash). Some of Dalton’s
atomic masses were in error because A s we shall see, some of these postulates were later modiﬁed, but the main features of Dalton’s atomic theory still are accepted today.
The law of conservation of mass in chemical reactions follows directly from
Dalton’s postulate that atoms are neither created nor destroyed in chemical re actions; rather, they are simply rearranged to form new substances. The law of
constant composition follows from Dalton’s postulate that atoms are indivisible
and that compounds are formed by joining together different types of atoms.
That is, compounds have constant composition because they contain ﬁxed ratios
of the different types of atoms. For example, suppose it is found that calcium
sulﬁde is formed when calcium and sulfur are combined in a one-to-one ratio.
In such a case, the ratio of calcium atoms to sulfur atoms is one-to-one, no matter how the sample is prepared. The law of multiple proportions follows from
the fact that some elements can combine to form more than one compound,
such as in the case of CO and CO2. Although Dalton’s application of his theory
was marred by several incorrect guesses about the relative numbers of atoms in
compounds (Figure 2.14), these errors were eventually resolved. Meanwhile,
the atomic theory gained wide recognition and is now universally accepted.
Dalton’s atomic theory enables us to set up a scale of relative atomic masses.
Consider calcium sulﬁde, which we know consists of 55.6% calcium and 44.4%
sulfur by mass. Suppose there is one calcium atom for each sulfur atom in calcium sulﬁde. Because we know that the mass of a calcium atom relative to that
of a sulfur atom must be the same as the mass percentages in calcium sulﬁde,
we know that the ratio of the mass of a calcium atom to that of a sulfur atom is Occult Chemistry:
Annie Besant & C. W. Leadbeater (Theosophists)!
O ccult Chemistry p roposes that the
structure of chemical elements can be
assessed through clairvoyant observation
with the microscopic vision of the third
e ye. Observations were carried out
b etween 1895 and 1933. "The book
consists both of coordinated and
i llustrated descriptions of presumed
etheric counterparts of the atoms of the
then known chemical elements, and of
other expositions of occult physics.” Occult Chemistry:
Annie Besant & C. W. Leadbeater (Theosophists)!...
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