[Quay]

Hello,
I am doing a lab in a couple of days on titrating sodium hydroxide solution (0.1M) with sulfuric acid (concentration to be found, we were told it could be quite concentrated). I was just wondering whether the resulting titrated solution of NaOH and H2SO4 could be disposed of down the drain? I saw one source saying it's alright since it's neutral, but another one saying that it needed loads of water to accompany it, and another one saying it wasn't safe and just to use a waste disposal container. These are the answer choices I get by the way for this lab question:

At the end of this practical you will have completed the titration of a sulphuric acid solution with sodium hydroxide. How do you suppose you will dispose of the mixture at the end?
      
a. the solution must be neutralised with acid before rinsing down the drain
      
b. the solution must be neutralised with base before rinsing down the drain
      
c. the solution can be washed down the drain as it would be neutral
      
d. the solution must be put in flammable solvent waste bottle for disposal

I've ruled out A and B since it's neutral, but am unsure of the choices between C and D.

Thank you very much in advance for any help you guys might be able to offer!

[Borek]

It is not flammable, so D is out.

It is pretty close to neutral, so in general there is no need to additionally neutralize it.

It should either go down the drain - just flush it generously with a tap water, or to the waste - and the details depend on your local regulations, there is no good answer that will be accepted everywhere.

[Arkcon]

Its very likely you were told specifically what to do in class, or in the laboratory rules handout, or a sign posted in your lab.  The best answer is likely C, but its not an absolute everywhere that the solution wouldn't be disposed of in a solvent can that's been designated "Lab Waste."  Your institution's drain system may be very old, or faulty in some other way, or they may want to get you in the habit of not disposing lab waste down the train.  This time it may be perfectly all right to dispose of neutralized acid-base titration waste, but what about the ammonia-acetic acid titration, that will be slightly smelly, even if nearly perfectly neutralized.  What about a barium sulfate precipitation, barium is as toxic as arsenic.