deeply interested in lime

[holbytla]

Could someone explain what "lime" is being talked about at the end of chapter 12?
fruit, lime-light or other?

You can't do better than be interested in
some lime works anywhere down about Northfleet, and doubtful
whether some of your lime don't get into bad company as it comes
up in barges.'

'You hear Eugene?' said Lightwood, over his shoulder. 'You are
deeply interested in lime.'

'Without lime,' returned that unmoved barrister-at-law, 'my
existence would be unilluminated by a ray of hope.'

[wllittle]

This would be lime as in the group of minerals mostly inclusive of carbonates and oxides of calcium. The lime "industry" is a very old one, and these minerals can be extracted from limestone or chalk, which are crushed and "burned" in a lime-kiln. (The Limehouse oft referenced in Our Mutual Friend is such a facility, and a famous/notorious one.) The hydrated lime that is carried up the river in the mentioned barges will probably find its use in concrete, and what starts as Lightwood's comment on the rather unsavory character of Riderhood (who lives in "Lime'us Hole") is here parried with the typical mildly sarcastic remark from Wrayburn.

[JSchinnerer2]

Alternatively, lime was also used as a fertilizer (it speeds up the process of bio-degradation). Wrayburn is asserting that, without "fertilizer", no barrister can be successful. This is another of Dickens's jabs at the law and at the courts. Put in modern American terms, no lawyer has any hope of advancing in his career unless he's capable of slinging a lot of "bull".
I suspect Dickens's original readers would have read the first paragraph with memories of large quantities of lime having been dumped in the Thames to hasten the breakdown of the human feces in the water -- contact with "bad company" indeed!