Sciencemadness Discussion Board

Cleaning Glassware/how clean should it be?

pepe - 12-8-2016 at 23:55

So my question is really about cleaning methods off glassware for experiments. Mainly about the use of common dish soap in cleaning? I have made it a point to clean my glassware with either water and alcohol or a light acid such as vinegar for most purposes. My girlfriend recently, while doing the dishes, mistakenly ran some of my glass through soapy water. I have always been apprehensive of cleaning my glassware with these soaps because of possible residues and the subsequent contamination that may occur if they are used in an experiment. Its not a huge deal to me because I am sure with enough cleaning I can get any residues off but I am really wondering if my disdain for cleaning with soap is justified? Further what do you use chemically and methodically to clean your glass?

Sulaiman - 13-8-2016 at 00:48

Considering glassware cleanliness ;

suppose you left 100 mg of contaminant in a beaker or flask
and you add 100 ml of 100 % pure reagents
your reagents are now only 99.9 % pure

how many of your reagents are better than 99.9 % pure ?
(with known impurities)
or
for volumetric work, with 100 % pure reagents and perfectly clean glassware, can you achieve less than 0.1 % errors
or
try to determine the ammount of impurities in your glassware as an experiment.
or
how pure is your water?




Metacelsus - 13-8-2016 at 04:25

In the lab where I work, visible contamination is removed by scrubbing with a bottle brush and detergent water. Then, the glassware is rinsed with deionized water, and finally acetone to remove any residual organics. Glassware is then dried in an oven. This procedure is suitable for general cleaning.

unionised - 13-8-2016 at 06:29

Quote: Originally posted by Metacelsus  
In the lab where I work, visible contamination is removed by scrubbing with a bottle brush and detergent water. Then, the glassware is rinsed with deionized water, and finally acetone to remove any residual organics. Glassware is then dried in an oven. This procedure is suitable for general cleaning.

Putting glassware in the oven when it has acetone on it can be a very bad idea indeed.
Unless you are certain that the oven's thermostat is spark proof there is a grave risk of an explosion.
You really don't need a lot of acetone to get an explosive mixture with air.

NEMO-Chemistry - 13-8-2016 at 08:07

Depending on the glass etc i use liquid dishwasher soap a fair bit, my reasoning being i know the flask or whatever is pretty clean once i no longer get any foam or bubbles. At that point i use deionized water and dry upside down in an old fridge (not plugged in).

For some bag gunk and if the flask isnt quickfit type or going to be used in a vacuum i sometimes use strong hydroxide to clean.

I also use TSP for cleaning. I use bottle brush and TSP or whatever will remove the residue and a whole tin of elbow grease if the flask is one i use for vacuum. I always try and avoid Hydroxide solutions in my vacuum glass.

If i need to dry straight away i use a home made incubator set at around 50c for drying. I have seen home glassware like drinking glasses totally frosted after several months being washed in a domestic dishwasher.

No idea whats in dishwasher tablet but judging by the pitting and frosting on glass i would never use one for lab glass.

WGTR - 13-8-2016 at 11:05

Also, as an FYI, don't ever put volumetric glassware in an oven. It'll go out of calibration.

NEMO-Chemistry - 13-8-2016 at 12:13

Quote: Originally posted by WGTR  
Also, as an FYI, don't ever put volumetric glassware in an oven. It'll go out of calibration.

Paranoia stops me using Volumetric flasks with hydroxide as well, no idea if this is warranted or not.

My reasoning goes back to the dishwasher frosting, i got given alot of pyrex cooking dishes for use because they were badly etched from dishwasher washing.

I inadvertently left one lid with sodium hydroxide prills on, it was a good while (many weeks) before i got around to cleaning off the powder that had formed, to my amazement the glass had gone back to being crystal clear on the side that had the prills on.

Since then i have been cautious with sodium hydroxide and glass! It probally took the smallest amo
unt of glass of but it was enough to stop me using VF's for Sodium Hydroxide

BromicAcid - 13-8-2016 at 20:49

It depends on what you are doing, general preparative chemistry, so long as it looks clean wet (and still looks clean once it dries) you are good to go. But if you're trying to make a high purity compound (and I mean really high purity, so high I don't see the need for a home chemist to go that route) you may need to put a bit more effort into your cleaning procedure.

pepe - 13-8-2016 at 23:29

Quote: Originally posted by BromicAcid  
It depends on what you are doing, general preparative chemistry, so long as it looks clean wet (and still looks clean once it dries) you are good to go. But if you're trying to make a high purity compound (and I mean really high purity, so high I don't see the need for a home chemist to go that route) you may need to put a bit more effort into your cleaning procedure.


This seems to be what it boils down to. And since generally my experiments do not require high purity I feel that I am quite safe with it having gone through one round of dishes.

There are so many great suggestions in this thread that I want to thank all of you. The consideration of not putting volumetric glassware in the oven is something so blatantly clear when its stated but for me to consider it it had to be stated. I am definitely going to play with Sulaimans suggestion of determining the amount of impurities in my glassware. A practical and interesting experiment that could certainly be. I wonder what kind of contamanints I am unaware of that perhaps have infected my wares?

I also thank you guys for posting your general procedures. Definitely helps one to see what others do and what works.

I wish I could contribute more to this thread as it has taught me a surprising amount in what I thought would be a relatively cut and dry thread. The use of hydroxides I previously would have considered but now I am somewhat second guessing. So I must humbly thank all contributors to this thread past and future for opening up a subject (cleaning) that is more tedious than most of us prefer... and as chemists that says something!

NEMO-Chemistry - 14-8-2016 at 03:05

Cleaning is the one reason i own as many flasks as i do! I hate cleaning glass! Not so much the monotony of it but i am clumsy, i tend to break things when i clean them.

Last breakage was the fine glass tube on the side of a Soxhlet extractor, what makes it worse is i was cleaning it for first use!

Numerous threads on here of me breaking things cleaning them for first use, i try my best to be careful but its time to get a rubber sink and floor!

Herr Haber - 16-8-2016 at 11:24

I clean after using the glassware and once again before.

The "after" cleaning usually isnt as thorough as the "before". And even then, it really depends on what I am going to do.
If I'm pouring 96% H2SO4 in a vessel, I usually just feel pity for whatever is still inside.

But otherwise, I clean with minimal dish soap using a sponge that *obviously* hasnt been used for anything else, use a lot of water to rinse and depending on what I am going to do I may do a final rinsing with demi water.
I sometimes use acetone to get rid of whatever is non soluble in water too.
I use paper towels to get rid of most water / solvent then put the glassware in the oven or on a tray in the sun.
I even resorted to use a hair dryer for some glassware that I needed *now* (pipettes, condensers and the like)

XeonTheMGPony - 16-8-2016 at 11:56

I use a light mix of sunlight dish soap and water, then I rinse and wash with methanol that is warmed to remove any insoluble, then depending on residue I'll use a weak rinse of HCL befor baking dry in the oven set to 200 degrees F.

that is general pre-cleaning, for first stage cleaning depends what the reaction was, I use the appropriate solvent/acid/base to remove all the materials

for less sensitive reactions a quick wash with hot light soapy water a water rinse then a methanol rinse to dry it out (I save the wet methanol to burn in my alcohol lamp! A penny saved!)