Abstract: A method for inhibiting or retarding gas hydrate formation comprises adding a solution of a compound of formula: ##STR1## wherein R=OH, OCH.sub.3, OC.sub.2 H.sub.5, NHNH.sub.2 or HR'=NH.sub.2 or NH.sub.3.sup.+X,Y,Z=H or OH, andn=a number in the range 0 to 6,or a polymer thereof when R'=NH.sub.2, the compound or polymer thereof being added in an amount effective to inhibit or retard hydrate formation, to a medium susceptible to gas hydrate formation, e.g. fluids produced from an oil well, particularly an offshore oil well.

Abstract: An apparatus for removing contaminants from a liquid comprises a casing and a tubular filter dividing the casing into two compartments. The tubular filter is formed of fibers attached at each end to end supports which are movable axially relative to one another and rotable relative to one another about the longitudinal axis of the filter. A helical spring is disposed within the tubular filter and is so dimensioned that it does not close when the end supports are in their closest operational position. The spring resists inward movement of the fibers when the end supports are moved axially towards each other and rotated to twist the fiber, thereby preventing the compartment defined by the interior of the tubular filter from tending to close.