There must be a loss, it's just a matter of how much. There will be a slight loss when gold melts at high temperature. If black-hearted merchants intercept gold and mix other substances, the weight will remain the same, but the purity will decrease. At the same time, the use of "aqua regia" by some merchants will also cause slight losses. There are also some "black-hearted" merchants who make a fuss about "Wang Shui" and purify it afterwards.