Photoisohumulone has been isolated as a crystalline solid, m.p. 62–63° C. and [α]10D = − 7.6° and as such distributes as a pure compound. It is shown to be a normal component of the reaction products obtained by refluxing humulone with aqueous alkali, and examination of the literature suggests that it is present in beer.

Hop wax has been found to occur in beer and is present in concentrations of 0-5-0-6 p.p.m. The wax occurs in the non-steam volatile fraction of the neutral ether solubles of beer. A number of acids produced by saponiflcation of hop wax have been shown also to occur as volatile constituents of beer. The particular sample of hop wax used is shown to have very little effect on the rate of deterioration of a acids. Certain aspects of the photoisomerization of humulone and humulone-hop wax combinations are discussed.

The sesquiterpenes caryophyilene, humulene, isocaryophyilene and “farnesene” have been found to occur in beer. These sesquiterpenes occur in conjunction with myrcene, methylnonyl ketone and other unidentified hop oil constituents.

The effect of heat (1 hour at 110°C) on a range of solid metal salts of humulone has been examined. Some salts, e.g. those of calcium, magnesium, cobalt (II) and nickel (II) undergo isomerization to the corresponding salt of isohumulone without any significant degradation. Other metal salts undergo partial isomerization without apparent degradation and some form both isohumulone and uncharacterized degradation products. The salts of aluminium, chromium (III), copper (II), lead (II) and mercury (II) show no formation of isohumulone. Under the same conditions the lead (II) salt of tsohumulone was unique in converting completely into the lead (II) salt of humulone.

Pure samples of 4‐methylpent‐2‐enoic acid, 4‐methylpent‐3‐enoic acid, γ,γ‐dimethyl‐γ‐butyrolactone and 3‐methylcyclopent‐2‐enone have been prepared and their physical constants and spectral characteristics determined.