At that time, the petroleum industry had a waste product, the compound propylene CH3-CH=CH2 that was burnt off. So, four propylene molecules were joined to form propylene tetramer that was further modified to produce the sodium salt of the sulfonic acid, called an alkylbenzene sulfonate (ABS).Alkyl is a generic term for a carbon chain of unspecified length (Fig. 4.2). Although the new substance is closely related to an ordinary soap, such as sodium palmitate, these surfactants and their calcium and magnesium salts are much more soluble than soap, so that a scum is not formed in hard water.