Rhodium (Chief Bee)
08-21-01 18:15
No 206434
      One of the best chem technique page I've seen  Bookmark   

http://www.organicworldwide.net/
 
 
 
 
    obituary
(Hive Addict)
08-21-01 21:29
No 206475
      Re: One of the best chem technique page I've seen  Bookmark   

that's the first time you've seen that page?  you should really see some of the other stuff available.  (not that it's not an excellent page, b/c it is)
 
 
 
 
    Roman
(Newbee)
08-24-01 00:51
No 206984
      Re: One of the best chem technique page I've seen  Bookmark   

Thanks for the chem link BigBee, my first time seeing
it also.
Peace,
Roman

It ain't over till the fat lady loses 50 lbs...
 
 
 
 
    Scooby_Doo
(Newbee)
08-25-01 00:19
No 207253
      Re: One of the best chem technique page I've seen  Bookmark   

Ditto to that chief. smile
 
 
 
 
    Stonium
(Moderator)
08-25-01 11:14
No 207338
      Re: One of the best chem technique page I've seen  Bookmark   

Da-amn Rhod'. I love you. Thanks for the very WONDERFUL link!



Nunc scio quit sit amor.
-Virgil
 
 
 
 
    LaBTop
(Daddy)
08-26-01 21:13
No 207658
      Re: One of the best chem technique page I've seen  Bookmark   

5, 6, 4 that MUST be the order in the Rotavap operation page.
That's a serious mistake, 4, 5, 6 which can blow you to heaven or at least burn several bodyparts, when the flask falls off the joint,even with a Keck clip on.
First you put vacuum on, so the flask will be securely sucked to the greased joint, then you lower the flask in the water or oil bath, and then you carefully turn the speed dial on, which you first set to zero.

With 20 liter Rotavaps, you put the 2/3 filled flask on, while already in the oilbath, to prevent the joints to break (the flask will float in the oil, and thus the force on the joints will be much less, when you connect them), and then you will suck vacuum, and clip the Kleck on, and then you start the heater, and as last, the speeddial slowly from zero to 100 RPM.
Removing is done also still lowered and floating in the oil, again, to prevent the joints from breaking.
This advice will extend the lifespan of your precious apparati.

Have seen people seriously burn because they did it the wrong way, no vacuum yet, put the speeddial on, which they forgot to set to zero first, and lowered the flask into a 160 C silicone oil bath, Keck clip broke loose - flask jerked off because of the friction caused by the boyancy of the 2/3 filled flask in a sudden wave of the oil when the revolving flask hit the hot oil, ether out of the flask hit the 165 C silicone oil, spat all over the place and face of the genius, and ignited , trip to the hospital.

His Tips etc: "The ground glass joint holding your flask does not need to be greased," that's very stupid to say the least! 

Same tips : "This reduces the surface area for evaporation " , much better solution is just pouring enough silicone oil on top of the water that no water splashes through the oil, 2 cm is enough, and even better, use an alu ring where the flask fit in with enough space left to let the waterfilm not be obstructed. Water will ALWAYS fast evaporate, because that's the principle of a Rotavap (and it's not rotOvap, btw, it's a ROTAting eVAPorator), it forms a 3mm hot film on the flask when rotating.

One should be critical reading these kind of sites, he seems not to have years of practice and thus seen the most ugliests and dummest accidents, caused by non-logical thinking and pure stupidity.

But at least he set up this site, and disserves help to improve the quality. Have not read the rest, will do, and send him email.

There are better sites in my Newbee sticky threads. This one is also there. Ehh, remember? : Read. If you want to spare time on safety. LT/

WISDOMwillWIN
 
 
 
 
    terbium
(Hive Addict)
08-26-01 23:38
No 207675
      Re: One of the best chem technique page I've seen  Bookmark   


His Tips etc: "The ground glass joint holding your flask does not need to be greased," that's very stupid to say the least! 



Yes, I thought that was really strange.

Not so strange but still, I thought, curious is that in the synthetic procedures, a reaction in liquid ammonia, they go to the trouble of taking the ammonia out of the cylinder as a gas and then condensing it with dry ice acetone instead of just taking liquid ammonia out of the cylinder via an eductor tube. Perhaps they get really dirty ammonia and this is a method of purifying it?

 
 
 
 
    terbium
(Hive Addict)
08-26-01 23:51
No 207676
      Re: One of the best chem technique page I've seen  Bookmark   

Speaking of greasing joints, don't people use teflon sleeves anymore? I thought they were the greatest thing since sliced bread; definitely no worries of a frozen joint if you are using a teflon sleeve.

When teflon stopcocks came out I thought they were going to be the greateest thing since sliced bread - no more frozen stopcocks - but no such luck. At least, in a sep. funnel, they don't leak like a ground glass stopcock.
 
 
 
 
    Osmium
(Stoni's sexual toy)
08-27-01 00:33
No 207678
      Re: One of the best chem technique page I've seen  Bookmark   

I never grease my rotovap joints. At least for the regular sized ones it's unnecessary.
And who is operating rotovaps with 160C hot oil??? Rotovaps are for solvent removal, not product distillation. Their separation efficiency is close to zero anyway.