I believe what that is, PP is made from 25% sodium hydroxide which is then diluted to the 3-4% concentration. Just like Roundup which is 45% when manufactured but is sold to the general public at 2 - 3%. The Ag industry buys Roundup at the 45% concentration and then reduces it to the % it needs to work on the vegetation it wishes to control which is usually ounces per acre. I hope I made some sense here.
kk