Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: Solubility and other data.
Pommie
Hazard to Self
**




Posts: 70
Registered: 6-2-2005
Location: Australia
Member Is Offline

Mood: No Mood

[*] posted on 18-11-2005 at 17:08
Solubility and other data.


Merck has made available lots of useful data at Merck ChemData

One of the links of this page is a Solubility Table.

When looking up the solubility of various compounds, I get conflicting values.

For example.
Copper Sulphate at 20<sup>o</sup>C
CuSO<sub>4</sub>.5H<sub>2</sub>O = 20.8 g/100mL
CuSO<sub>4</sub> = 36.4 g/100mL

Can I really take 57g of CuSO<sub>4</sub>.5H<sub>2</sub>O and dry it out to get 36g of CuSO<sub>4</sub>, which will then dissolve in 100mL of water? It seems counterintuitive that by drying it first I can get a solution thats nearly 3 times stronger.

Whats more, if I then go the the MSDS for CuSO<sub>4</sub>, I get different values again.

Have I misunderstood something here or is the available data unreliable?

Can anyone suggest a book (preferably EBook) that contains reliable data?

Mike.
edit clarification

[Edited on 19-11-2005 by Pommie]
View user's profile View All Posts By User
woelen
Super Administrator
*********




Posts: 7723
Registered: 20-8-2005
Location: Netherlands
Member Is Offline

Mood: interested

[*] posted on 19-11-2005 at 10:09


Sadly enough, data on the Internet is not realiable at all. I have the same kind of experience with MSDS data. Different solubilities mentioned, sometimes even different colors mentioned or one MSDS saying that a compound is slightly toxic (level 1) and another MSDS stating that its toxicity is life-threatening (level 3).

The only thing you can do is collect data from multiple sources and hope that the value, mentioned most frequently is correct.

Another thing is that you can try yourself at a gram scale. It would be very nice if tried and tested data is made available by sciencemadness members. That would be a great resource :)!




The art of wondering makes life worth living...
Want to wonder? Look at https://woelen.homescience.net
View user's profile Visit user's homepage View All Posts By User
Magpie
lab constructor
*****




Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: Chemistry: the subtle science.

[*] posted on 19-11-2005 at 10:26


I try to get all my MSDSs from reputable chemical supply houses like J.T. Baker. I feel they would be risking their reputation if they publish garbage.



The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
chromium
National Hazard
****




Posts: 284
Registered: 27-6-2005
Member Is Offline

Mood: reactive

[*] posted on 19-11-2005 at 12:46


20.8 g/100ml is in fact solubility of CuSO4 without water molecules in it ( I have book that says 20.5g /100ml )

36.4g/100ml is solubility of pentahydrate. Lets do some calculations.

36.4g of pentahydrate contains 23.27 g sulfate and 13.13g water.
So we have 113.13 ml water and 23.27g sulfate - this is 20.57 g of sulfate in 100ml water wich is almost exactly what it should be.

Regarding on reliability i completely agree with woelen just want to add that books too conatain errors. Consult as many sources as possible do not expect that you can rely on one source even if it is regarded as best of them all!

[Edited on 19-11-2005 by chromium]
View user's profile View All Posts By User
Pommie
Hazard to Self
**




Posts: 70
Registered: 6-2-2005
Location: Australia
Member Is Offline

Mood: No Mood

[*] posted on 19-11-2005 at 17:38


Thanks everyone.

Quote:

36.4g of pentahydrate contains 23.27 g sulfate and 13.13g water.
So we have 113.13 ml water and 23.27g sulfate - this is 20.57 g of sulfate in 100ml water wich is almost exactly what it should be.


That explains it. I wondered if the data was the wrong way round but couldn't get the values to tally, due to the fact that I totally ignored the 13g of water.

Mike.
View user's profile View All Posts By User

  Go To Top