Solid Deposit In Glass Bottle

[derrynoose]

I have found an old (wide- necked) glass milk bottle which has a dirty white solid lump of matter at the bottom. I can't shake this lump out of the bottle, nor can I manage to break it up. I suspect that it is solidified milk. I have the idea that steeping the mass in a mild solution of acid might work. Any advice, please.

[Tilly2]

Have you tried really hot water?

[bhg481]

Using really hot water could be pushing your luck with glass - liable to shatter. I'd go for soaking with washing-up liquid for 24 hours.

[theprof]

You're on the right track but it depends what you can get hold of. Try 50% (V/V) hydrochloric acid and leave it overnight if necessary. Nitric acid at the same strength would also do the job.

Avoid any alkaline substances such as caustic soda as they will affect the glass.

But to be honest, rather than mess about with acids, I'd mix up a strong solution of biological washing powder in fairly hot water and leave it overnight in the bottle. This might well do the trick.

My lab technicians would funnel in piranha acid or chromic acid into the bottle in a fume cupboard. The deposit would be gone in seconds. Oh the fun we have in laboratories!

Seriously though, if you do decide to use acids, make sure you don goggles, gloves and observe obvious safety precautions.

[gingejbee]

Oh, the joys of using chromic acid to get REALLY clean glassware....

[Old_Geezer]

Would vinegar or a vinegar solution help ? It whips rust off iron well enough.

[theprof]

Vinegar is a good suggestion Old_Geezer as it can dissolve a surprising number of deposits and stains. However, in this case there is insufficient acid present to have an effect on the solidified milk. Vinegar is too weak to have much effect on the deposit even if it was left to stand overnight with neat vinegar on top of it.

[EDDIE51]

Chromic Acid, that brings back memories of my first years in a Chemistry lab. We used it all the time, always remember how it turns green when it dissolves some rubbish.
I think it got banned around the early 1970s ?

[EDDIE51]

^^ memory coming back now , we used to look for dead flies and drop them into Chromic Acid to watch them dissolve.