THE deterioration in mechanical strength experienced by copper containing disseminated oxide after he~fing in contact with reducing gases is marked ; a copper strap, initially ductile and resistant to repeated bending, after exposure of this kind becomes weak and friable, breaking when an attempt is made to bend it. .Copper straps heated in atmospheres of th.ydrogen, carbon monoxide and natural gas all developed this defect, the severity of this action depending on ~Vhe nature of the reducing gas. In the case of hydrogen the first mechanical effects of the deterioration appear between 400 and 5ooΒ°C, and at temperatures above 7ooΒ°C the action is very rapid, a few minutes' exposure being sufficient to ruin the strap.
Deoxidation alone cannot account for ~he weakness developed, for it is hard ;to see why the substitution of a small void for a small particle of very brittle cuprous oxide would weaken the surrounding copper: The action taking place appears to be that hydrogen, if physically soluble in the copper, would diffuse into the metal, a~ack a.nd reduce the grains of cuprous oxide wi,th the formation of steam. If steam is physically less soluble in solid copper, the net result of the reaction would be the formation of a quantity of steam free within the voids lef, t by the reduction of the cuprous oxide and at some considerable pressure. The combination of this pressure wkh the known intercrystallineweakness o.f copper at high temperatures would force the individual grains apart until relief is obtained, and the resultant weakness ,be due simply to the lack of mechanical coherence within the " puffed" copper. Microscopic examination of copper after this treatment disclosed *Communicated by the Director.