The leather disk had been soaked in a mild acid solution of lemon juice.

皮板由于柠檬汁酸性溶液的浸泡而浸透。

youdao

Whenever this thought occurs to me, my heart would feel acid, just like the taste of lemon juice, which then drops on the raw wounds, and causes slight pains.

想到这里，我的心总会有一些酸酸的，仿佛涩涩的柠檬汁的味道，滴在伤口上，又会微微有些痛楚。

youdao

Drink lemon juice: lemon essentially contains good amounts of citric acid, which is a part of AHAs group that has amazing properties to reduce acne scars.

喝柠檬汁：柠檬其实含有大量的柠檬酸。柠檬酸是果酸的一种，其具有惊人的减轻疤痕作用。

youdao

The acid from the lime, lemon or orange juice changes the structure of the proteins in the fish much in the same way that heat does. (If you make it at home, you can observe the flesh turning from translucent to opaque.) Therein lay my answer.

NPR: Cool and Comforting Ceviche