Abstract: A process for etching aluminum in caustic solution capable of providing a consistently uniform matte finish like that of the never dump process, but with little waste like the regeneration process. Etching is performed in a solution containing free sodium hydroxide and dissolved aluminum in a ratio between about 0.6 and 2.1 g/l and also containing an etch equalizing agent at a temperature above about 70.degree. C. Preferably, the etch solution is regenerated through a crystallization loop.

Abstract: A simplified and effective trap for small animals is illustrated utilizing positive linkage means for dislodging or actuating a trip mechanism to permit a cage door to fall by gravity and utilizing a gravity actuated latch for locking the door in lowered closed position.

Abstract: A process and apparatus for obtaining a more concentrated solution of components such as chromium containing anions by the use of ion exchange beds. A solution containing the component to be concentrated is passed through a first bed in which the component is taken up. A second solution containing a component of opposite charge from the first component is passed through the first bed to take up the component from the first bed and then through a second bed capable of taking up the second component from the solution. The second solution is passed from the first bed directly to and through the second bed, and both beds are rinsed following passage of the second solution therethrough by passing a rinse solution through the second bed and then directly to and through the first bed in a direction opposite to the direction in which said second solution passed through the beds.

Abstract: A lever is pivotally mounted in the back of a cage at the center of the lever and is balanced therein. The lever has a first end in the cage with a tray thereon for bait and a spaced opposite second end movably positioned between a first pair of spaced parallel posts supported a predetermined distance from the back of the cage. A trip rod has a length longer than the distance between the posts and rests on the lever between the posts and the cage. A cord has a first end affixed to the front bottom edge of a trap door hingedly affixed to the top of the cage at the front thereof and a spaced opposite second end affixed to the center of the trip rod. The cord is guided along the top of the cage and around the cross bar in a manner whereby the trap door is held open and when an animal depresses the front end of the lever by taking the bait, the second end of the lever moves upward and knocks the trip rod free thereby slackening the cord so that the trap door is released and closed.

Abstract: This invention provides a method and apparatus for transferring heat to a cooler gas from a hotter gas which contains tri-atomic molecules with good infra-red energy absorption characteristics, for example CO.sub.2. The hotter gas is passed in a first direction along a conduit, and simultaneously the cooler gas is jetted through and across the hotter gas in a direction transverse to the hotter gas direction. This allows the tri-atomic molecules minimally entrained in the cooler gas jets to provide heat to the cooler gas firstly through transferring their initial kinetic energy to the cooler gas molecules by way of collision, and secondly by absorbing infra-red energy radiated from the hotter gas and passing this absorbed energy to the cooler gas molecules also through collision.

Abstract: Mild steel strip is galvanized in selected areas only, typically on one side only of the strip, by pretreating the areas selected for absence of galvanizing to form thereon a readily chemically strippable coating of chemically hydrated compounds non-wetting in molten zinc. Preferably, the pretreatment is carried out using phosphoric acid solution to form thereon a thin coating of a composite of hydrated iron phosphates and iron hydroxides. After passing the thus-treated steel strip through the molten zinc bath and solidification of the zinc coating, the composite coating is removed by dilute mineral acid. Mild steel strip galvanized on one side using this procedure has particular utility in the automotive industry.