The possibility of warming the flood water in paddy rice land by suppressing evaporation from the water surface was previously confirmed by one of the authers and his colleagues.
In response to our request, n-docosanol (C22H45OH) has been synthesized by M. Suzuki from, first, octadecanol (C18H37OH) and next from the rape oil. However, having scarecely surface activity, Docosanol was combined with oxyethylene (CH2CH2O) at various rates of amount to get high spreading power. A lot of samples were made and supplied to the tests of spreading power and suppressing ability of evaporation.
In this paper, best two kinds of oxyethylene glycol, C22H45OCH2CH2OH and the mixture of C22H45 OCH2CH2OH and C18H37OCH2CH2OH, are compared with two alcohols, C18H37OH and C16H33OH, in regard to the surface pressure and suppressing power of evaporation. The formers show 30-70% higher suppressing power than each of later two when they cover the water surface with their mono-moleculer films.
In particular, C22H45OCH2CH2OH shows extremely high ability in the temperature range of 20 to 30 °C, reducing evaporation to blow 10% of that of free surface water. The mixture of two glycols indicates high ability of suppression even in the range of low temperature in which C22H45OCH2CH2OH hardly suppresses the evaporation. So called OED, made of the mixture glycols above mentioned, is now being put in practical use by rice growers for the purpose of warming the cold standing water and of advancing the growth of rice.