During the negative pressure portion of the sound wave, the liquid is lacerated and the cavitation bubbles begin to form. When the negative pressure develops inside the bubbles, the gases dissolved in the liquid begin to spread outside the limits of the bubble. When the negative pressure is reduced due to the passage of the rarefaction portion of the sound wave and atmospheric pressure is reached, the cavitation bubbles begin to collapse because of their surface pressure. During the compression portion of the sound wave, all the gases diffused in the bubbles are compressed and then begin to spread again through the edges of the bubble, re-entering the liquid. However, this process is never complete since the bubbles contain gas from when the diffusion outside the bubble begins to until the bubble is compressed. Once the bubble is compressed, the bubble surface area is reduced. As a result, the cavitation bubbles formed in the liquid contain gas that does not always collapse in an implosion, but actually results in small pockets of compressed gas in the liquid. This phenomenon can be useful in degassing liquids. The small gas bubbles come together until they float sufficiently to reach the surface of the liquid.