Limited Magic Item Creation Feats: An arcanist may not count his arcanist levels against the level requirements of item creation feats. As an example, a wiz 3/clr3/arcanist 5 cannot learn any item creation feats requiring a caster level over three to learn, despite the fact that his caster level as either a cleric or wizard is eight.
Prohibited Metamagic: An arcanist cannot use or learn any metamagic feats with spellcasting classes improved by his arcanist class. Any metamagic feats he knows become useless to him unless he has a third spellcasting class not affected by his arcanist spellcasting abilities.
Prohibited Spell Research: Arcanists cannot research new spells for spellcasting classes improved by his arcanist class. Arcanists fill their minds by rote learning to prepare the maximum possible number of spells. This rigid training inhibits the creativity required to research new spells. This does not prohibit an arcanist with a spellbook from scribing or copying spells, and such a character still gets the two free spells with each level of advancement.