mH3PO4=3*1u+31u+4*16u=98 u
mP:mO=31:64
mH:mO=3:64
mP:mH=31:3
64u---x%
98u---100%
x=65,31%O
31u---x%
x=31,63%P
3u---x%
x=3,06%H