A study has been made to show the effect on growth of common molds when substances both fat and water soluble are introduced into the culture medium. Materials of this type were studied because of the well-known fact that many molds and particularly the spores contain considerable quantities of fat. Eutyric acid, among the first of the substances tried, showed remarkable fungistatic properties. Substitution of salt in place of the acid indicated that the p H of the medium was an important factor to be considered.A study of the fungistatic properties, over a wide ~€ 3 . range, of the following acids has been completed: all of the normal saturated fatty acids containing from one to 14 carbon atoms; isomeric forms, such as iso-butyric; the three isomeric forms of n-Valerie; some of the unsaturated acids, such as crotonic and hendecenoic; and some of the substituted acids, such as p-iodopropionic. Kiesel (1913) investigated the effect of a large number of organic acids on mold growth using Raulin's Solution as the nutrient medium. Since Raiilin's Solution contains tartaric acid and has a pH of 2.8, his work applied only to conditions existing in highly acidic media. Rideal (1921) reported that formic acid is an effective mold inhibitor although this present study showed that formic acid has very limited fungistatic properties. Kirby, Atkin, and Frey (1937) described the fungistatic properties of acetic and other organic acids. On the other hand, Walker and Coppock (1928) showed that calcium propionate was utilized by mold as a source of carbon. The uncertainties, and in many cases contradictions, existing in this field have been excellently summarized by I31111 (193'7). EXPERIMENTAL PROCEDUREThe fungistatic properties of the fatty acids were studied on an agar medium in Petri dishes, the medium being buffered at the desired pH with a suitable buffer mixture. The medium consisted of standard nutrient agar of one and one-half times normal strength with one per cent added sucrose. It was necessary, obviously, to use buffers which were non-toxic to molds. The buffers of McIlvaine (1921) were found satisfactory as neither citric acid nor disodinm 539

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INDUSTRIALAND ENGINEERING CHEMISTRY 749 crawling are different from those which give rise to the defects produced upon baking. A change in the balance of the simple mechanical forces involved in the equilibrium between adhesion and cohesion probably accounts for these differences.Changes in polarity of the materials during baking which, in turn, would affect the interfacial tension at varnish-metal interfaces, also probably play an important part. This work is being continued.

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