I'm not sure I can remember everything from above, but I thought you had looked up the solubility of sulfanilamide as 210 mg/mL. If that is so, then
1 mL x 300 mg/210 mg = about 1.5 mL alcohol.
You are rather certain that it will take <6 mL for that is what the lab manual tells you to measure out and bring to a boil. So-- do as I said before. Add about 1 mL of the heated alcohol to the 300 mg sample of sulfanilamide, swirl, add another few drops, swirl, and continue until all of the 300 mg sample is dissolved. Then crystallize. If you count drops, then about 20 drops is 1 mL; therefore, it should dissolve with about 10 more drops than the 1 mL you started with (assuming the 210 mg/mL is accurate.) It would help if you could determine a number for the solubility of the stuff so you would feel confident that you weren't added far too much ethanol. Adding too much will affect the yield.
How to calculate yield. The same as you do percent anything.
%yield = (amount recovered/0.300)*100.
Plug in for the 0.300 what you actually start with.
I'm really confused as to finding a RELIABLE source to find the solubility of sulfanilamide.
Do you know at what temperature are they refering to for the Merck index's
1g in 37ml of alchohol?
The reason I'm doubting the 210mg/ml is that I got that from an exact question same question answered on that answering site with a y-hoo in it. The question just had a 0.1g instead of 0.3 like I did. The person answering them posted a link to a powerpoint file. I downloaded that and I saw that it was for the same labs that I was doing and had that listed as the solubility.
However I can't back that up with anything on the web about the solubility of sulfanilamide. I looked but can't find the solubility for some reason and I still don't know what the unit gm means for the only solubility of sulfanilamide that I found or I would be able to convert it and see if it was accurate and matched with the powerpoint slide #'s.
I found solubility on a website as:
7.5 gm/100gm water at 25C (77F).
You didn't say whether you knew what that unit was Dr.Bob...like I said before all I found was GM the company
gm is an old abbrev of GRAM. That's the way we wrote it in the good old days. :).
Let me look for the solubility and I'll get back.
That clears things up alot Dr.Bob
And I'll check later to see what you find.
OK. I give up I guess. I have looked high and low and googled everything I can think of. I can find the solubility in water and The Merck Index lists about eight different temperatures along with the solubility in water. All procedures I could find on the web recrystallized from water. I found ONLY the one referecne to solubility in ethanol in The Merck Index as 1 gram in about 37 mL ethanol but no T was listed. That would be about 27 mg/mL ethanol but that doesn't tell us much without a T listed. It's interesting that I found your question and my answers to these several postings on google so others who try the same thing will find the 210 mg listed. Of course I knew to disregard that. Anyway, I tried but no luck. When you go to the library at your school, look in Beilstein if they subscribe (it will be in German) and see if Beilstein lists the solubility in ethanol. I would ask the teacher, too. If you are supposed to look this up ask him/her for a hint or two about WHERE to look it up and describe in some detail about where you have looked. I also looked in a copy of an organic chemistry text I have at home. It gave the procedure for preparing the drug but no solubilities or other information about recrystallization. I just looked in the CRC handboodk (Handbook of Chemistry and Physics) and found it was soluble in water, ether, and ethanol but no numbers or T were given. Well, I tried. But no luck. Ask some class room buddies, too.
THANKS ALOT for spending all of that time looking and I appreciate the effort it took to look up all that.
Thanks Again Dr.Bob =D
Do you have a lab text book? Perhaps it is written by Pavia or others. In many text books there is a graph of the solubility of sulfanilamide vs temperature for 95% ethanol... Look at the graph and determine the solubility at 78 deg C. Hint - it is bigger than 200 mg/mL.
To find how many mL are needed you need to dissolve it you should multiply the inverse of the solubilty times grams to get mL.
210 mg of sulfa dissolves in 1 ml of alcohol @ 78 degrees celsius.
(1ml alcohol/ .21g sulfa) 0.30g sulfanilamide = 1.42 ml alcohol to add to sample.
I have this lab text book. If you read the question carefully it says use information from the introduction to answer your question. If you then read the introduction very, very carefully, it sends you from page 23 to page 600-something where there is a solubility-vs-temperature graph for temperature and ethanol. That is where the solubility of 210 mg/ml @ 78 C is given and can be verified. It would have saved you some time, but like I said ... they did a good job of hiding the information.
Using the volume 1.5mL of 95% ethyl alcohol that's required to dissolve 0.3g at 78 C, how do i find how much sulfanilamide that will remain in the mother liquor after the mixture is cooled to 0 C?
Since the solubility of sulfanilamide at 0 C is 14mg/mL, do I multiply 1.5mL and 14 to get how much sulfa will remain in the mother liquor?
Calculate how much 95% ethyl alcohol will be required to dissolve 0.75g of sulfanilamide at 78 degrees Celsius.