Abstract
A modified Wilhelmy balance which was commonly used to measure the pulmonary surface activity was made in our laboratory and some basic studies on the operation of this apparatus were performed. Conclusions obtained as follows:
1. DPL and normal lung extract showed low minimal surface tension when area was compressed to 20% of initial area. The tension-area diagrams of them showed fat hysteresis loop. Minimal surface tension of albumin combined DPL was 8.5 dynes/cm ±0.7 lynes/cm.
2. When area was compressed less than 20% of initial area and under 10 cm2, the surface tension of albumin combined DPL reached under 10 dynes/cm, and that of normal lung extract under 5 dynes/cm.
3. There was no significant difference between sinusoid drive and triangular drive of barrier moving on maximal and minimal surface tension.
4. It is adequate to operate this apparatus in the following conditions:
1) Area change: between 45 cm2 and 0 cm2.
2) Barrier drive: sinusoid or triangular.
3) Time for one cycle: 5 minutes.
