386 Dr Fenton and Mr Barr, Some colour-reactions of 
Some colour -reactions of organic acids with Phenols. By 
13. J. H. Fenton, Sc.D., F.R.S., Christ’s College, and G. Barr, B.A., 
Christ’s College. 
[Read 25 November, 1907.] 
It is well known that certain organic acids give rise to re- 
markably brilliant colour-reactions when they are acted upon 
by phenolic compounds in presence of dehydrating agents. With 
the object of ascertaining to what extent these reactions might 
be applicable to the preliminary identification of acids, the 
authors have tabulated the results obtained when a few of the 
less common acids are treated with phenols, at the ordinary 
temperature, in presence of strong sulphuric acid. By com- 
paring the colours obtained in this way with two or more phenols, 
information of a positive character may often be obtained. The 
method has the advantage of being applicable not only to the 
acids but also to their salts or esters, and it may be employed 
for provisional identification when only minute quantities of the 
substance are available. 
3’he following table shews the results of preliminary observa- 
tions made in a rough qualitative manner. In a few cases the 
effects are modified if considerable excess of one or other reagent 
is employed. When dry metallic salts are used it is sometimes 
necessary to add a drop of water to the mixture in order to obtain 
the characteristic colour mentioned. 
