2D NOTICES OF THE MEETINGS [May 27, 
in these combinations, certain groups of elements had the same 
persistent character and fulfilled the same chemical function as the 
simple elements themselves in other bodies. These constant 
groups have been named radicals. Among these those hydro- 
carbons termed the homologues of hydrogen are of special interest. 
Ethyl, a groupe consisting of two atoms of carbon and five of 
hydrogen, C, H,,'is one of these bodies. Assuming water as two 
atoms of hydrogen and one of oxygen, H H QO, alcohol is com- 
posed of one atom of ethyl, one of hydrogen, and one atom of 
oxygen, (C, H,) HO. Hydriodic acid, the iodide of hydrogen, 
consists of an atom of hydrogen combined with an atom of iodine, 
H I. The iodide of ethyl consists of an atom of ethyl combined 
with an atom of iodine, (C, H,) I. It is from these and other 
like analogies between hydrogen and ethyl, that the idea arose of 
the similarity in their chemical function. 
Certain chemists however conceived these views to be mere 
fanciful speculations. Their principal objection, reasonable or not, 
was that this ethyl was a purely ideal substance. From hydro- 
chloric acid, or from water, we readily procure hydrogen. We 
separate metals from their combinations ; but ethyl could not thus 
be obtained, and there was a point where it seemed that this analogy 
failed. Frankland however has silenced this objection in the most 
satisfactory manner, namely by procuring and isolating this ethyl. 
He prepared it by a modification of the form of experiment by 
which hydrogen itself is prepared. He placed together zinc and 
iodide of ethyl in tubes hermetically sealed, and heated them 
considerably above the boiling point of water. On opening the 
tubes the ethyl escapes as a colourless combustible gas. There is 
only one property of ethyl on which I need dwell, its weight —it is 
about twice the weight of air. 
Ethyl, however, when procured, did not realize all the anticipa- 
tions formed of it, and there was one very important difference 
between the actual and the anticipated ethyl. It was supposed 
that when zinc acts upon iodide of hydrogen it takes away 
(so to say) the iodine, and the hydrogen becomes, what is termed, 
free, and the same with ethyl. On this view ethyl would have 
a certain atomic constitution, C, H;. Now there is much reason 
to believe, that in the gaseous form the molecules of all bodies 
occupy the same space, whether this molecule consist of two only, 
or, as may be the case, of one hundred atoms. Hence to ascertain 
of how many atoms the molecule of a substance consists, we 
have simply to compare its weight in the gaseous form, with that of 
some other gas of which the molecule is already determined. 
When this experiment was made with ethyl, it was found to be 
just twice as heavy as it should be; that is to say, the space which 
should have contained two atoms of carbon and five of hydrogen, 
was found to contain just twice that quantity, or C, H,,. 
Some chemists considered that ethyl was an exception to the 
