The Home Scientist 014 - Cheap Sulfuric Acid, Part II

Analyzing cheap hardware store sulfuric acid for concentration and purity by gravimetric (mass) analysis.

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[98JMA]

What solvent do you use for your phenolphthalein?? I have it in powder form but when dissolve it in ethanol or water it doesn't work properly - both acids and alkalis are colourless!!

[TheHomeScientist]

@98JMA

Whatever you have, it doesn't sound like phenolphthalein, if you can dissolve it in water. Phenolphthalein is pretty freely soluble in ethanol or isopropanol, but nearly insoluble in water.

I generally make up 100 mL or so at a time by dissolving a gram or two of the solid in 50 mL or so of 91% or 99% isopropanol and making up to 100 mL with DW.

[salsburyp]

One small source of possible error would be the weight of the NaOH, which is extremely hygroscopic and would slowly gain weight as it draws water vapor from the air. If this is a centigram scale, that may not be noticeable in the small amount of time, but on my milligram balance, I can watch the weight increase second by second, which makes weighing NaOH tricky. Usually need to do it in solution.

Overall, a great 2-part video! Thanks, Robert! :-)

[TheHomeScientist]

@salsburyp

Thanks for the kind words. Yes, NaOH is extremely hygroscopic. The other obnoxious thing about it is that it absorbs CO2 from the air, producing sodium carbonate. When I'm doing critical work, I generally dry the NaOH in an oven and weigh it warm. I still standardize it, though.

[salsburyp]

@TheHomeScientist And doesn't sodium carbonate further absorb CO2 to make sodium bicarbonate? Does that mean that if left alone in the open air, NaOH would eventually become pure baking soda?

[TheHomeScientist]

@salsburyp

No, Na2CO3 is stable. In fact, it's a primary standard. The only problem with it is that it has multiple hydration states. The anhydrous form absorbs water from the air to form the monohydrate. The common decahydrate efflouresces to form the monohydrate.

[oheeohkillertofu]

This is a great video, thanks for sharing!

[Arsonomega]

I have a suggestion for your future videos.... When your listing off numbers It would be very helpful to display them on the screen lets say in the empty space to our right.... (your left) that way it would be easier to follow what your talking about...

[ScienceTry]

This might sound stupid, but are you NurdRage? I mean, if you edit your voice like he does, you sound EXACTLY like him.

[stefen7077]

What a great video! Thanks for making it.



[acemeister666]

rooto has something in it... on heating, it turns dark brown.

[gleepdiddly]

Wow!

[dukilaki]

so that is why i didnt get sulfuric acid burn when i splited it on my skin.

[PyroPortrayal]

@TheHomeScientist

May I ask where you got that nice scale?

[dstnlockwood77]

can you show how to make nitric acid please that would be really helsetll. thanks

[chemy999]

@salsburyp bicarbonate means hydrogen carbonate, not two carbonates, that would be dicarbonate