The Action of metallic Magnesium, etc. 
385 
The Action of metallic Magnesium on certain aliphatic acids, 
and the detection of Formic acid. By H. J. H. Fenton, Sc.D., 
F.R.S., Christ’s College, and H. A. Sisson, B.A., Clare College. 
(Read 25 November 1907.] 
In a previous communication (Trans. Chem. Soc. 1907, G87) 
it was shewn that both carbonic and formic acids may be reduced 
to formaldehyde by means of metallic magnesium. Experiments 
have since been undertaken with the object of ascertaining whether 
an analogous reduction can be effected in other acids ; the results, 
as far as they go, appear to indicate that such a reduction only 
occurs in the lower members of a series. With formic acid the 
reduction is easily recognisable even in very dilute solutions, but 
in the cases of acetic, propionic and butyric acids the formation 
of aldehydes is only apparent when strong solutions are employed 
and the temperature is allowed to rise. Oxalic acid yields, even 
in cold dilute solutions, notable quantities of an aldehydic product 
which presumably is glyoxylic acid. Negative results were ob- 
tained with malonic, succinic, glycollic, lactic, tartronic, tartaric, 
malic and many other acids. 
The reduction by means of metallic magnesium may be 
employed as a specific test for formic acid ; the usual methods 
of detecting formic acid depend, for the most part, only upon 
its reducing properties, whereas the reactions of formaldehyde 
are of a far more positive character. 
The solution to be examined is digested with the metal, in 
the form of ribbon or powder, at the ordinary temperature for 
some minutes, and the resulting product is tested for formaldehyde 
by any of the usual colour tests or, if the quantity is sufficient, 
by means of phenylbydruzine. Soluble metallic formates give a 
similar result, but the reaction is much more delicate when the 
free acid is employed. 
