A recent television program here in the UK explained quite a few things about soapbar.
The authorities refer to it as 'formula', and this stems from the amount of 'stuff' mixed with it.
For those that still smoke it, it was also explained that the average piece of soapbar has, wait for it, 5%, yes, 5% of anything that will actually get you high!!! The rest is made up from a wide variety of things and here is a little list i found:- Beeswax, turpentine, milk powder, ketamine, boot polish, henna, pine resin, aspirin, animal turds (camel shit), ground coffee, barbiturates, glues and dyes plus carcinogenic solvents such as Toluene and Benzene.

It is called soap because a 250 gram (9oz) is soap bar shaped.

Personally, id give up if soap was all i could get..