Fog drip

A variety of chemicals may be leached from the aerial portions of plants by rainwater or by fog-drip (16) including organic acids, sugars, amino acids, pectic substances, gibberellic acids, terpenoids, alkaloids, and phenolic compounds. Colton and Einhellig (17) suggested that leaf leachates of velvetleaf (Abutilon theophrasti) may be inhibitory to soybean (Glycine maxT We have recently discovered specialized hairs on the stems of velvetleaf plants which exude toxic chemicals. 

Fogging is formation of small water droplets (visible condensation) on the surface of a polymer film. Undesirable effects may result from fog formation, such as reduction of clarity and dripping. Incorporation of antifogging agents eliminates the reduction of transparency by migration to the surface and increases the polymer surface critical wetting tension. This results in... 

Fuming sulphuric acid. Used as a smoke producer in WWI. Dripped onto a bed of quick lime much heat generated evaporation of the acid condensation into tine droplets, the acid is hygroscopic. Dense fog produced. 

Experiments of McPherson and Muller (1969), McPherson et al. (1971), and Muller and Chou (1972) have shown that substances responsible for the observed allelopathic effects are water soluble and waterborne with both species. One of the major climatic features of this vegetation is coastal fog even in the summer months and although rainfall is only moderate, there is a constant drip of moisture on to the leaves of these shrubs and, hence, onto the surrounding soil. This dripping is sufficient to carry a regular supply of water-soluble inhibitors from leaves to the soil where they remain in sufficient concentration to prevent growth or seed germination of any annual species near these shrubs (McPherson and Muller, 1969). 

Unless otherwise agreed upon, the samples are placed at a 15-30 angle from vertical. (Automotive components, however, are often tested in in-car position.) This orientation allows the condensation to run down the specimens and minimize condensation pooling. Overcrowding should be avoided. An important aspect of the test is utilization of a free-falhng mist, which uniformly setdes on the test samples. Samples should be placed in the chamber so that condensation does not drip from one to another. Test durations are typically in 24-h increments and can range from 24-5000 h. (Where salt fog exposure is a part of a more complex test method, exposure time can be as little as 15 min.) Except for sample rotation and daily monitoring of collection rates, the cabinet should remain closed for the duration of the test. 

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