Register to reply

Just a qn on Gravimetric analysis

by sero2000
Tags: analysis, gravimetric
Share this thread:
sero2000
#1
Jun16-08, 01:47 AM
P: 24
Hi im just wondering why during precipitation, hydrochloric acid is added to the mixture of barium chloride and sodium sulphate. Does it have something to do with the PH values or what?
Phys.Org News Partner Science news on Phys.org
Suddenly, the sun is eerily quiet: Where did the sunspots go?
'Moral victories' might spare you from losing again
Mammoth and mastodon behavior was less roam, more stay at home
Borek
#2
Jun16-08, 03:52 AM
Admin
Borek's Avatar
P: 23,363
There is a common contaminant (present in the air) that gives precipitate with Ba[sup]2+[sup]. Low pH will drive it away.


the ultimate buffer calculator
sero2000
#3
Jun16-08, 04:05 AM
P: 24
Quote Quote by Borek View Post
There is a common contaminant (present in the air) that gives precipitate with Ba[sup]2+[sup]. Low pH will drive it away.

Borek
--
the ultimate buffer calculator
Hmmm... So u mean if the HCl was not added, the barium ions would react to form some other stuff instead of reacting with the sulphate ions?

Borek
#4
Jun16-08, 06:05 AM
Admin
Borek's Avatar
P: 23,363
Just a qn on Gravimetric analysis

Not all, only some, but your precipitate will be contaminated, thus it will not have known exact composition.

Also note, that if your solution contains other metals, in hight pH their hydroxides can preciptate, which won't happen in low pH. Finally, HSO4- is a relatively weak acid, in low pH it ismostly protonated, which slows down precipitation. That's good - the slower the precipitation, the larger the crystals are and the easier filtration is.

Somehow I feel presence of someone green and small...
sero2000
#5
Jun16-08, 09:35 AM
P: 24
Quote Quote by Borek View Post
Not all, only some, but your precipitate will be contaminated, thus it will not have known exact composition.

Also note, that if your solution contains other metals, in hight pH their hydroxides can preciptate, which won't happen in low pH. Finally, HSO4- is a relatively weak acid, in low pH it ismostly protonated, which slows down precipitation. That's good - the slower the precipitation, the larger the crystals are and the easier filtration is.

Somehow I feel presence of someone green and small...
Lol alright dude thanks alot man =) lol someone green and small?


Register to reply

Related Discussions
Gravimetric Analysis- Questions Chemistry 4
Gravimetric analysis of a carbonate Biology, Chemistry & Other Homework 1
A question about gravimetric analysis Chemistry 1
Thermal Gravimetric Analysis question. Chemistry 1
Gravimetric Analysis Chemistry 0