Notably it incorporated a vaporiser inside the circle. There were serial modifications culminating in the Mark III apparatus of 1951, which continued in use through the 1960s. A partir de 1955, se hizo realidad la eficiencia superior en la absorción de dióxido de carbono de un aparato de círculo verdadero sobre el absorbedor de "círculo" rival de Coxeter-Mushin.
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