73 replies to this topic

[Bonny]

I should be getting 1l of 70% HNO3 next week to use for making strontium and barium nitrates. If I should use 25% concentration(as I have read elsewhere to use) is this the correct dilution?

Assuming I am trying to make 1l of 25% concentration:
(.70)V1=(.25)1000ml---->V1=357ml

Vs=1000-357---->643ml

Therefore I add 643ml water to 357ml of HNO3?

[YT2095]

I`ll leave the maths to you, but always add the acid to the water, NEVER add water to the acid!

[Bonny]

I`ll leave the maths to you, but always add the acid to the water, NEVER add water to the acid!

Ooops, typed it wrong. Was just trying to get ratios. I knew to always add acid to water, but should have double checked what I wrote before posting.

[YT2095]

no problem

I just don`t wanna see ya get hurt that`s all, so it seemed worth a mention

[Gazza]

Just another safety note: when you add the solid barium carbonate to the dilute nitric acid, you will see vigorous effervescence (fizzing) caused by the rapid evolution of carbon dioxide gas. The airborne aerosol produced by this will be likely to contain toxic barium nitrate, aswell as nitric acid. So, it would be advisable to carry-out the reaction outside, or cover the reaction vessel with a clear plastic bag in order to contain the mist. Only add the barium carbonate in small quantities at a time. I assume you have the appropriate safety gear- safety specs and a respirator?

[Bonny]

Just another safety note: when you add the solid barium carbonate to the dilute nitric acid, you will see vigorous effervescence (fizzing) caused by the rapid evolution of carbon dioxide gas. The airborne aerosol produced by this will be likely to contain toxic barium nitrate, aswell as nitric acid. So, it would be advisable to carry-out the reaction outside, or cover the reaction vessel with a clear plastic bag in order to contain the mist. Only add the barium carbonate in small quantities at a time. I assume you have the appropriate safety gear- safety specs and a respirator?

I'm all set for safety equipment. I did this reaction before, only I used the 70%HNO3 as is, no diluting. I did end up adding a considerable amount of water to dissolve all the nitrate though. This time I would like to start with a dilted solution and I will be doing smaller batches.

[Bonny]

I've finally finished dissolving all the barium nitrate and evaporating litres and litres and litres of water. I think I should end up with around 2kg of barium nitrate. Due to the impurities in the (ceramic grade) barium carbonate, a hydrogen sulfide odour was evident during the reaction. The nitrate still has this odour as it is drying out, and I am hoping this stink will go away once the nitrate completely dry.

[Anders Greenman]

I've done the exact same many times and never had problems with odour with the final product. If you heat it properly after the reaction has taken place, both the acid and any sulfur traces should disappear.

[YT2095]

I find that adding a small amount of H2O2 with the mix as your dissolving the carbonate stops much of H2S smell, as it locks it up as barium sulphate.
if you add Campden tablets that also works by the RXN: SO2 + 2H2S = 2H2O + 3S.

after Either of these methods you Will need to filter the liquid away from the PPT.

[Bonny]

Next time I make it (likely in the spring) I will try adding some H2O2. In this case everything is done except drying the crystals. As long as the smell goes away I'll be happy. The first time I did this rxn, it was left to evaporate outside, so smell was not noticeable, but it took forever and a day to evaporate all that water.

[YT2095]

yeah, it works quire nicely

and don`t worry that the H2O2 is more than likely stabilised with Phosphoric acid, yes it`s a nasty tribasic acid and as good as Sulphuric for most things anyday of the week!
it also will react with the barium to make an insoluble PPT, it`s only a trace amount they put in anyway to keep its shelf life, but against Barium... it`s got No chance

(3Ba 2+) + (2PO4 3-) = Ba3(PO4)2

Edited by YT2095, 14 November 2007 - 05:00 PM.

[Bonny]

I've added a box of baking soda to my drying box near the exhaust fan to try and remove the H2S smell. It seems to be working (or most of the gas has dissipated already) I'll have a better idea when I get home how much it stinks...

[Bonny]

I've done the exact same many times and never had problems with odour with the final product. If you heat it properly after the reaction has taken place, both the acid and any sulfur traces should disappear.

I'm not sure what exactly you mean by heating properly. I boiled off all the water after dissolving the barium nitrate and filtering... I have the crystals in a tray and it still stinks I cranked up the heat in my drying box today (vented outside) and am hoping to drive off the smell. Is it possible that the H2S is caught in between the crystals? I was thinking of milling the crystals and then continuing to air them out as a possible solution.

[YT2095]

it is possible yes, and since we can detect very low amounts of H2S with our noses it doesn`t need to be much.
cracking the crystals in a mill and drying again will remove it and have the added effect of releasing trapped liquid in them also leaving a drier product.