determining sulphur given in the B.P. gave low results and tecourse was made to a wet oxidation using bromine in nitric acid. This accords with the U.S. National Formulary and it is suggested that such a method should be introduced into the B.P. owing to the presence of volatile oils in ichthammol.
The results (Table 111) support the view that sulphonation reduces the organic sulphidic sulphur and that the greater the degree of sulphonation the greater is the amount lost.
Bacteribstatic action of ichthammol
The bacteriostatic activity of various samples of ichthammol and ichthyol oil was investigated by the agar plate method to see if there was any relation between the chemical composition and potency. The cultures used were Staph. arcreus, Strep. jaecalis and Bact. srrbtilis. The tests were complicated by the fact that ichthammol, being water-soluble, diffuses into the agar whereas the unsulphonated oil does not. The unsulphonated oil showed little inhibition but there was some inhibition in the zones into which ichthammol diffused, except with Bact. coli. Dispersing agents, by giving better contact between the unstdphonated oil and bacteria, might produce better results but we have not investigated this point, nor have tests siluilar to' the Rideal-Walker test beencarried out.
In spite of differences in chemical composition, no differences in action of various samples of ichthammol on any given bacterium could be detected.
Conclusions
(I) The production of ichthammol requires more careful control than has been exercised in the past.
(2) Water-soluble ichthammol is not miscible with fixed oil and the B.P. requires amendment.
(3) In view of the doubt that exists about the merits of the sulphonated or the unsulphonated oil, it is suggested that pharmacologists should consider whether the unsulphonated oil should not be 'cmployed, as it is soluble in an oily or fatty base ; also, with the aid of modem emulsifying agents, it can readily be mixed in to any ointment or emulsion base.