( 144 ) 
aldehyde, was more fully studied. The results of this study led Wurtz 
to propose a formula for dialdane according to which it still contains 
one aldehyde group, exhibits the properties of an alcohol twice and 
contains two carbon atoms united by a double bond. From two mo- 
lecules of aldole 
CH; CHOH CH, COH 
dialdane 
CH; CHOH CH, CH: CH CHOH CH, COH 
is therefore formed by the separation of water from the methylgroup 
of the one molecule and the aldehyde group of the other. 
The second condensation product, which Wurtz called isodial- 
dane, was only obtained by him in very small quantities, and was 
not further examined. He obtained it, along with other substances, 
by heating aldole to 125°; it melted at 112°. 
In an attempt which one of us made long ago !) to combine aldole 
with hydroeyanie acid, pure hydroeyanie acid was mixed with aldole 
and the mixture left to itself for some months. It was found that 
the hydroeyanie acid had not combined with the aldole, or only to 
a very small extent; it had, however, acted as a dehydrating agent 
so that two molecules of aidole had formed one molecule of isodialdane. 
As a result of this observation isodialdane was readily obtainable 
and a proper study of it was taken in hand. The result of the investi- 
gation possesses a more general interest because it leads to the con- 
clusion, that isodialdane is to be regarded as a substance in some 
measure analogous to ordinary cane sugar, in the sense that the 
relation between isodialdane and the two aldole molecules, from which 
it is formed, is the same as that between cane sugar and glucose 
and fructose (laevulose). 
It is known that cane sugar does not possess reducing powers 
and therefore does not contain an aldehyde group, but that under 
the influence of dilute acids, it very readily takes up a molecule of 
water, being converted into the two above mentioned reducing hexoses ; 
the aldehyde group of glucose and the carbonyl group of fructose 
are therefore absent in the saccharose molecule. At the same time 
two of the ten hydroxyl groups of the two hexoses disappear, for 
saccharose only gives an octo-acetate. Let us now turn to the results 
of the study of isodialdane. It has no reducing power, but with 
dilute acids it at once obtains this; it is thus very readily inverted. 
) Bull. Soc. Ch. (1884) 42. 161 
